US 20100281454 A1
A substrate device is designed by identifying one or more criteria for handling of a transient electrical event on the substrate device. The one or more criteria may be based at least in part on an input provided from a designer. From the one or more criteria, one or more characteristics may be determined for integrating VSD material as a layer within or on at least a portion of the substrate device. The layer of VSD material may be positioned to protect one or more components of the substrate from the transient electrical condition.
1. A method for optimizing application of voltage switchable dielectric material (VSD) on a substrate device, the method being performed by one or more processors that perform steps comprising:
identifying one or more criteria for handling a transient electrical event on the substrate device;
identifying one or more optimization criteria for integrating the layer of VSD material onto at least the portion of the substrate; and
optimizing the layer of VSD material based on the one or more optimization criteria.
2. The method of
determining, from the one or more criteria, one or more characteristics for integrating VSD material as a layer within or on at least a portion of the substrate device, the layer of VSD material being positioned to protect one or more components of the substrate from the transient electrical event.
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This application is a Continuation of U.S. patent application Ser. No. 11/860,530 entitled SYSTEM AND METHOD FOR INCLUDING PROTECTIVE VOLTAGE SWITCHABLE DIELECTRIC MATERIAL IN THE DESIGN OR SIMULATION OF SUBSTRATE DEVICES, filed Sep. 24, 2007, which claims benefit of priority to Provisional U.S. Patent Application No. 60/943,556, entitled SYSTEM AND METHOD FOR PROGRAMMATICALLY DESIGNING ELECTRONIC DEVICES USING VOLTAGE SWITCHABLE DIELECTRIC MATERIAL, filed Jun. 13, 2007; the aforementioned priority applications being hereby incorporated by reference in its entirety.
Embodiments described herein pertain to design or simulation of electrical devices. In particular, embodiments described herein pertain to a system and method for including protective voltage switchable dielectric material in the design or simulation of substrates and other electrical devices.
Electronic Design Automation software and similar programmatic tools enable the design and/or simulation of components on electronic devices. Examples of such devices include printed circuit boards (PCBs) and integrated circuit or semiconductor packages. Typical functionality provided with such tools include schematic entry, behavioral modeling, circuit simulation, full custom layout, physical verification, extraction and back-annotation. Used mainly for analog, mixed-signal, radio-frequency communication components (“RF”), and standard-cell or memory designs. EDA software may also be used for functions such as (i) create integrated circuit devices, including testing and placing and routing of such devices; (ii) simulate function verification.
Embodiments described herein may be referenced to any one or more of the following figures.
Embodiments described herein provide for programmatic design or simulation of substrates carrying electrical elements to integrate voltage switchable dielectric (“VSD”) material as a protective feature. In particular, VSD material may be incorporated into the design of a substrate device for purpose of providing protection against transient electrical conditions, such as electrostatic discharge (ESD). In this respect, embodiments described herein may be used as part of a computer system or programmatic process for designing and/or simulating substrate devices. As an example, one or more embodiments may be implemented as part of an Electronic Design Automation (EDA) program, which are normally used to design and produce electronic devices and systems, including printed circuit board (PCBs), display devices and backplanes, integrated circuit devices, semiconductor components and devices.
Generally, VSD material refers to material that exhibits the property of (i) acting as a dielectric in the absence of some threshold voltage or energy that is significant in the context or environment where the VSD material is provided, (ii) becomes conductive when applied a voltage that is in excess of a threshold voltage level. The threshold voltage level may vary for different kinds of VSD materials, but it generally exceeds the operational voltage of the surrounding environment of the VSD material. As a result of this switching property, VSD material can be positioned to form transient electrical connections that can protect against transient electrical events, most notably electrostatic discharge (ESD).
Embodiments described herein recognize that an ESD event typically ranges from a few hundred volts to tens of thousands of volts, with peak amperages of a few amps to tens of amps. ESD events are both high wattage (product of volts and current) and low energy events (as energy is a product of volts current and duration), since an ESD event only lasts from picoseconds to a few nanoseconds. When a VSD material is triggered to the “on” state with a high voltage pulse, current begins to flow through the thickness of the material.
Some devices or structures are capable of handling ESD events by including a layer of VSD material within or on a thickness of the device. Conventional approaches provide for depositing VSD material to occupy a layer within a thickness of a printed circuit board. Such a layer may be tied to various electrical leads or current carrying elements through vias as conductive elements. U.S. Pat. No. 6,797,145 (hereby incorporated by reference in its entirety) describes a technique for implementing VSD material within a current carrying structure in a manner that enables the VSD material to be used to plate the conductive element. Such plating techniques may also enable the device to have some capabilities for handling ESD events.
Numerous examples of VSD material exist, including those described in U.S. patent application Ser. No. 11/881,896 and U.S. patent application Ser. No. 11/829,951, both of which are incorporated by reference in their respective entirety. VSD material may also include commercially available products sold under the name “SURGX”, manufactured by the SURGX CORPORATION (which is owned by LITTLEFUSE INC.). VSD material can further be characterized as a material having non-linear resistance.
Moreover, according to one or more embodiments, the VSD material has a characteristic of being uniform in its composition, while exhibiting electrical characteristics as stated. In such an embodiment, the VSD material is comprised of a matrix or binder that contains conductive and/or semi-conductive material that is substantially uniformly distributed.
As used here, “design phase” or “simulation phase” of a substrate or other device refers to data representations of such substrates and devices.
In the description and examples provide, the characteristic voltage level and the threshold values are assumed values, determined from experimental conditions that can be affected by numerous variables. As such, the values described in this application should not be considered physical certainties, like would be the case for the property of density.
Embodiments described herein provide for a system or method for design or simulation of a substrate device. Specifically, numerous embodiments described herein exist, or are otherwise implemented, in the context of a design or simulation phase of a substrate device. In a design or simulation phase, no actual substrate device is necessary for practicing one or more embodiments described herein. Rather, embodiments that are described herein in the context of a design or simulation phase may use data representations of substrate devices, VSD material, components and elements of the substrate device, and the behavior of the components/elements/VSD material under various conditions.
In one embodiment, a substrate device is designed by identifying one or more criteria for the handling of a transient electrical event on the substrate device. The one or more criteria may be based at least in part on an input provided from a designer. From the one or more criteria, one or more characteristics may be determined for integrating VSD material as a layer within or on at least a portion of the substrate device. The layer of VSD material may be positioned to protect one or more components of the substrate from the transient electrical condition.
In another embodiment, a system is provided for manufacturing a substrate device (rather than a system for design or simulation apart from manufacture). The system may include an interface, a memory resource and a processing resource. The interface receives one or more criteria from a designer. The memory resource stores information about the substrate and/or various types of VSD material. The processing resource may be configured to use the input and the information stored in the memory to: (i) identify one or more criteria for handling of a transient electrical event on the substrate device; and (ii) determine, from the one or more criteria, one or more characteristics for integrating VSD material as a layer within or on at least a portion of the substrate device. The layer of VSD material is positioned to protect one or more components of the substrate from the transient electrical condition.
Still further, an embodiment provides for designing a substrate device during a design or simulation phase. Responsive to an interaction with a designer, a plurality of locations are selected on a substrate device that are to provide a protective electrical path when the transient electrical event occurs. At each of the plurality of locations, a dimension of a layer of a VSD material is determined at the selected location. The dimension of the layer of VSD material is selected based at least in part on a threshold measure of energy that is required to cause the layer of VSD material to switch from a dielectric state into a conductive state. When the VSD material is in the conductive state, the VSD material interconnects one or more components to the protective electrical path.
Another embodiment provides for determining a spacing of one or more electrical components that are to be connectable on a substrate device. In an embodiment, one or more electrical tolerances are identified for an electrical component that is to be protected against transient electrical events by a protective electrical path. A layer of VSD material may be identified that is to provide a gap separation between the electrical component and the protective electrical path. The VSD material is capable of switching from a dielectric state into a conductive state with application of a measure of energy that exceeds a threshold level, and the threshold level may be dependent at least in part on a dimension of the VSD material. In an embodiment, the gap separation is sized or dimensioned so that the threshold level for the measure of energy that causes the VSD material to switch is less than the one or more tolerances of the electrical component.
According to another embodiment, a system is provide for enabling design or simulation of at least a portion of a substrate device. The system includes a data store and a configuration module. The data store maintains data that references a first entry representing a first type of VSD material with one or more properties of the first VSD material. The one or more properties of the first VSD material may include a value representing a characteristic voltage per designated length. The characteristic voltage per designated length may correspond to a known or designated voltage level value that, when applied across a designated length of the first VSD material, causes the first VSD material to switch from a dielectric state into a conductive state. The configuration module determines, from one or more interactions with a designer of the system, (i) one or more dimensional parameters that are based on spatial constraints of the portion or of the substrate, and (ii) a voltage level that is tolerable by one or more electrical components that are to be protected in the portion of the substrate device. The configuration module may be configured to determine a gap separation that (i) is to be provided by a layer of the first VSD material on at least the portion of the substrate, and (ii) is to separate at least one electrical component from a protective electrical path on the substrate for transient events. Additionally, the configuration module determines the gap separation based at least in part on determining (i) a threshold voltage level that will likely cause the first VSD material to switch into the conductive state (ii) based on the characteristic voltage per designated length and a size of the gap separation. The configuration module may further ensure that the threshold voltage level is less than the tolerable voltage level of the one or more electrical components.
An embodiment further includes an optimization system for enabling design or simulation of at least a portion of a substrate device. The system includes a data store, a configuration module, and an optimization component. The data store maintains information about a plurality of types of VSD materials. The information may include a characteristic voltage per designated length for each of one or more types of VSD materials. The characteristic voltage per designated length may correspond to a voltage level applied across a designated length of a particular type of VSD material that is likely to trigger the VSD material of the type to switch from being in a dielectric state to being in a conductive state. The configuration module may be configured to determine, from one or more interactions with a designer of the system, (i) one or more dimensional parameters that are based on spatial constraints of the portion or of the substrate, and (ii) a voltage level that is tolerable by one or more electrical elements that are to be protected in the portion of the substrate device. The configuration module is configured to determine, for any of the plurality of types of VSD materials, a gap separation that (i) is to be occupied by that type of VSD material on at least the portion of the substrate, and (ii) is to separate at least one electrical element from a protective electrical path for transient events. The configuration module is further configured to determine, for any one of the plurality of types of VSD material, the gap separation needed for using a layer of that VSD material to separate the at least one electrical element from the protective electrical path. The optimization component is configured to make a selection of at least one of (i) a selected type of VSD material from the plurality of types of VSD material, or (ii) a size of the gap separation for the selected type of VSD material. The optimization component may also be configured to make the selection based on one or more optimization criteria.
Still further, one or more embodiments include a system for optimizing application of VSD material on a substrate device. The system includes an interface, a memory resource, and a processing resource. The interface may be configured to receive one or more criteria from a designer of the substrate device. The memory resource stores information about at least one of the substrate or of various types of VSD material. The processing resource is coupled to the interface and to the memory resource, and is configured to use the input and the information stored in the memory to (i) identify one or more criteria for handling of a transient electrical event on the substrate device; and (ii) determine, from the one or more criteria, one or more characteristics for integrating VSD material as a layer within or on at least a portion of the substrate device. The layer of VSD material may be positioned to protect one or more components of the substrate from the transient electrical condition. One or more optimization criteria are identified for integrating VSD material onto some or all of the substrate.
Additionally, an embodiment includes a data system. The data system may be used for applications that include enabling design or simulation of a substrate device. The data system includes a data store that is accessible to a configuration module for integrating VSD material into a substrate device. The data store maintains a plurality of entries, and each entry (i) identifies a type of VSD material, and (ii) includes data that identifies one or more electrical characteristics of the type of VSD material that are pertinent to integration of that type of VSD material into the substrate device. The one or more electrical characteristics of the type of VSD material may include any one or more of: (i) a characteristic measurement of energy that, when applied to a designated measurement of the type of VSD material, is likely to cause the VSD material of the type to switch from a dielectric state to being in a conductive state, (ii) a leakage current associated with the type of VSD material; or (iii) an off-state resistance associated with the type of VSD material.
As provided below, numerous other embodiments are described. Additional embodiments may also combine features of multiple different embodiments even though such combinations are not expressly stated in this application.
Embodiments described herein provide that methods, techniques and actions performed by a computing device are performed programmatically, or as a computer-implemented method. Programmatically means through the use of code, or computer-executable instructions. A programmatically performed step may or may not be automatic.
One or more embodiments described herein may be implemented through the use of modules or components. A module or component may include a program, a subroutine, a portion of a program, or a software component or a hardware component capable of performing one or more stated tasks or functions. As used herein, a module or component can exist on a hardware component independently of other modules/components, or a module or component can be a shared element or process of other modules, programs or machines.
Furthermore, one or more embodiments described herein may be implemented through the use of instructions that are executable by one or more processors. These instructions may be carried on a computer-readable medium. Machines shown in figures below provide examples of processing resources and computer-readable mediums on which instructions for implementing embodiments of the invention can be carried and/or executed. In particular, the numerous machines shown with embodiments of the invention include processor(s) and various forms of memory for holding data and instructions. Examples of computer-readable mediums include permanent memory storage devices, such as hard drives on personal computers or servers. Other examples of computer storage mediums include portable storage devices, such as CD or DVD devices, flash memory (such as carried on many cell phones and personal digital assistants (PDAs)), and magnetic memory. Computers, terminals, network enabled devices (e.g. mobile devices such as cell phones) are all examples of machines and devices that utilize processors, memory, and instructions stored on computer-readable mediums.
Application of VSD Material on Substrate Device
With reference to an embodiment of
The designer 102 may implement various kinds of information in the design module 110, including circuit layout, components, design parameters, and/or performance criteria. These specifications enable the subject device 122 to be designed, simulated and optionally produced in a design medium 120. As such, the design medium 120 may be virtual or simulated, or alternatively actual or real. The simulated or virtual design medium may correspond to a computer-implemented environment that enables, for example, simulation or testing of a subject device 122. As embodiments such as described pertain to design or simulation, device 122 may include data representations of actual physical devices. A real design medium may include the use of manufacturing, production and/or other implementation equipment and processes for implementing designs generated from module 110 onto the subject device 122 production.
In one embodiment, design module 110 includes logic 114 for determining and automating application of VSD material onto the subject device 122. Logic 114 may be responsive to design and/or performance parameters 104 specified by the designer 102 and/or obtained from other sources. The application of VSD material may include an initial determination as to whether VSD material is to be used. In one embodiment, an initial determination is made as to whether a board or base element of the subject device 122 is to include VSD material. For example, the user may simply select a substrate for the design that has embedded within it a layer of VSD material. If VSD material is to be included, VSD material application logic 114 may use various prompts and/or design (“VSD material configurations 116”) specifications to determine how VSD material is to be applied on the subject device 122.
In an embodiment, the design module 110 may provide an initial prompt 111 or interface to enable the designer 102 to elect (explicitly or implicitly) to have the VSD material included in the subject device 122. The module 110 may also provide one or more subsequent prompts 111 or interfaces to determine specifics about the device under design, including tolerance levels of individual elements on the substrate, spatial constraints, and device type. In one embodiment, all of the information used in determining a configuration for the VSD material is inferred. For example, user input pertaining to voltage tolerances of individual components or elements of a device under design may be used to programmatically determine at least some of the VSD configuration information, such as, for example, the type of VSD material used and one or more spatial characteristics of the VSD material (e.g. gap separation or shape, as described below). In another embodiment, some of VSD configurations may be determined from user-input that directly pertains to the VSD material. The responses to the prompts 111 may be provided by inputs 113 of the designer 102. The additional VSD material configurations 116 may, for example, specify location of the VSD material, and material composition of the VSD material or other factors that may affect the performance of the VSD material in the presence of an ESD event. Under one embodiment, the presence and specification of the VSD material may be tied to the ESD characteristics desired from the subject device 122.
In step 210, the design module 110 prompts the user for information that is directly or indirectly related to the application of VSD material on the subject device 122. In one embodiment, the prompts include an initial prompt as to whether the designer wishes to include VSD material and/or its protective functionality on the substrate. As an alternative or variation, the designer may also be prompted for one or more of the following: (i) for desired ESD characteristics or types of electrical events that are to be protected, (ii) optimization parameters, such as cost or priority in spatial constraints, (iii) regional input affecting location where VSD material is to be provided. The prompts listed are not intended to be exhaustive, but numerous other prompts may also be included. In one implementation, the prompts may be in the form of questions that direct the user to enter the desired characteristics. As another implementation, the prompts may be provided in the form of presentation of graphical menus or other graphical features or options that enable the user to specify design choices (such as relating to ESD handling capabilities).
Based on information provided by the user, a determination is made in step 215 as to whether VSD material is to be present on the subject device 122. In one implementation, the determination is as simple as the user electing to have VSD material and/or material protection against ESD and/or other transient events. In another implementation, the determination may be programmatically inferred from, for example, input from the designer specifying desired characteristics of the subject device 122 and how the subject device 122 is to handle ESD (e.g. tolerance voltage levels).
If the VSD material is not necessary, step 220 provides that the design of the subject device 122 is carried forward without use of VSD material. If the VSD material is deemed necessary, step 230 provides that the design of the subject device 122 is carried forward with VSD material integrated in the construct or thickness of the device. In one embodiment, for example, the application or program performing the method selects a substrate that has VSD material integrated as an internal or surface layer within the substrate.
As an addition or alternative to routing the board, components of the subject device 122 may be selected. In one embodiment, step 235 may thus provide full or partial automation of routing or otherwise implementing a design of the subject device 122, based on the determination that the device is to inherently include a layer of VSD material, such as in the form of a layer of VSD material in a thickness of a substrate of the subject device 122.
Still further, as another alternative or addition to step 235, step 240 may enable the designer 102 to enter information regarding desired performance parameters, material strength and/or components that are to be used on the subject device. Based on such information, step 240 configures or constructs VSD material elements within the subject device 122. In one implementation, the material composition of the VSD material may be set by the material properties of the subject device 122. For example, the pliability or strength of the board or its components may determine the composition, thickness and location of the VSD material. Likewise, performance parameters such as switching voltage (as provided by characteristic voltage per designated length) may affect the type and/or thickness of VSD material used, or the manner in which VSD material is used to plate vias or other conductive areas of the subject device 122. In this way, the application of VSD material is based on information provided by the user relating to desired characteristics of (i) the subject device 122 and/or (ii) how the subject device handles the ESD events.
VSD Material Configuration During Design Phase
As an addition or alternative to embodiments such as described above, one or more embodiments described herein provide for the design or simulation of a substrate to incorporate programmatic selection or design of specific characteristics (under design or simulation) of the VSD material, including both localized and substrate-level characteristics.
In general, embodiments described herein recognize that VSD material may be of various types in that numerous compositions of the material are possible. The composition of the VSD material affects electrical and physical properties of the VSD material. Some of the pertinent electrical properties of the VSD material include the characteristic voltage or energy levels by which a specific type or composition of VSD material switches on (i.e. switch from being dielectric to being conductive).
The characteristic energy level indicates a measure of energy needed in order to switch-on a given amount of VSD material of a particular type. As the ability for VSD material to switch on generally lasts a short time period, the amount of energy required to switch VSD material into the conductive state may be represented by the characteristic energy level. The characteristic energy level for a given type of VSD material generally corresponds to some form of energy (such as voltage) that can be applied to a designated measurement of VSD material in order to switch the VSD material into the conductive state. The designated measurement of VSD material may correspond to a linear dimension of VSD, corresponding to a gap or separation distance between two conductive elements that are to be connected when the VSD material switches on. While the form of energy may be expressed as current, power or electric field, embodiments described herein primarily refer to the characteristic energy level has being in the form of an applied voltage. It should be apparent, however, that use of applied voltage may readily be substituted for other forms of energy, such as current or power. The use of applied voltage as the form of energy that defines the characteristic energy level and the behavior of the VSD material under transient and operating conditions is a matter of choice, as simple relationships can substitute voltage for other forms of energy. For example, the application of Ohms law (which may be strictly applied only at a limited range of voltage values, given non-linear resistive nature of VSD material) may enable identification of a characteristic current from the characteristic voltage.
In the description provided herein, the “characteristic energy level” is represented through voltage (i.e. the “characteristic voltage level”). The “characteristic voltage level” is (i) specific to a particular type of VSD material, and (ii) is known with some degree of certainty to cause a designated measurement of the particular type of VSD material to switch from being dielectric to being conductive. Unless stated otherwise, the characteristic voltage level is a voltage that is applied over a designated length of VSD material and is known to cause the amount of VSD material occupying that length to switch into a conductive state. As stated previously, the use of voltage as the form of energy may be substituted for other forms of energy, such as current, power, or electric field.
A “threshold energy level” represents an amount of applied energy for switching the VSD material into an on-state. When the applied energy is expressed as voltage, a “threshold voltage level” or “on-voltage” refers to the voltage level that is needed to switch a particular quantity of VSD material into a conductive state. In many cases, the threshold voltage level can be assumed to be a product value of the characteristic voltage level per designated length multiplied by the length of VSD material that is present.
More specifically, the characteristic energy level includes elements of a trigger and a clamp. A trigger energy level is an initial energy level that initiates the material to switch from being dielectric to being conductive. The clamp energy level is the energy level that needs to be maintained in order to maintain the VSD material in an “on-state”. When expressed as voltage, both the trigger voltage and clamp voltage provide a measure of energy that can be applied in a given duration to effect the switch in the electrical characteristics of the material. Even though the length of time that the VSD material can remain on is brief, in some cases, the application of energy as measured from the trigger voltage may be compensated for by time. In at least some scenarios, the trigger voltage may be reduced or compensated for with a lesser voltage that exceeds the clamp voltage and lasts a sufficient duration. In most cases, the occurrence of a voltage exceeding the clamp voltage is a requirement for switching the VSD material on. However, the trigger voltage does not always have to be matched in order to switch the VSD material on. As such, unless stated otherwise, embodiments described herein which reference a characteristic voltage level (per designated length) of VSD material should be assumed to reference the clamp voltage.
Another electrical characteristic of VSD material for consideration is a measurement of leakage current, or alternatively, off-state resistivity. In general, leakage current is undesirable, but can be tolerated. Different types of VSD material have varying leakage current rates. Moreover, leakage current characteristics of VSD material (or alternatively the off-state resistance) may fluctuate with other factors, including operational voltage. Thus, the environment for use of the VSD material, and more specifically, the operational voltage, may also be a consideration when VSD material is analyzed or otherwise considered for design.
For any given type of VSD material, both the threshold voltage (needed to switch the material “on”) and the leakage current are or affected by the effective amount of material present at a relevant location (i.e. between two conductive paths). The effective amount of material may be measured linearly, by area or by volume. In general, the greater a linear length of VSD material in use (alternatively termed the gap separation or gap value), (i) the greater the threshold voltage level needed to switch the material on, and (ii) the lesser the amount of leakage current present (or conversely the higher the off-state resistance). As a matter of reference, the characteristic voltage level and leakage current values for VSD material may be specified by a designated length.
The amount of area or volume of VSD material at a relevant location between two conductive points may also be pertinent to electrical properties that are to be present between the two conductive points. For example, in come cases, the volume occupied by VSD material in providing the transient connection may increase leakage current.
Embodiments described herein recognize that during design or simulation of a substrate device or other electrical component, the VSD material may be selectively positioned to form a transient connection between a conductive path and a protective electrical path (e.g. such as a ground). A designer of the substrate or electrical device may specify design criteria for the transient connection, that explicitly or implicitly results in a determination of one or more of the following: (i) at what voltage level should the connection be switched on (i.e. the threshold voltage level); (ii) how much leakage current is acceptable at the connection, considering tolerance levels of surrounding components; (iii) how much space is available for the transient connection.
In the application of VSD material to accommodate a given design criteria, the following determinations may then be made: (i) the type of VSD material that is to be used, as the type affects desired electrical characteristics; and/or (ii) the gap separation distance that the VSD material is to occupy in forming the transient connection. One or more embodiments may also consider the area and volume (i.e. thickness and area) that the VSD material is to occupy in providing the separation and transient connection between two conductive elements.
Under an embodiment, VSD configuration module 310 implements the various considerations and principles described for integrating VSD material onto a substrate as part of a transient protective connection. As described, the considerations and principles for implementing VSD material may require determination of parameters relating to spatial restraints of the device or area where VSD material to be present, tolerance levels of components and elements that surround or may use the VSD material, and transient level requirements (e.g. desired level of ESD protection) of the device or elements that are to be protected. With reference to an embodiment of
In an embodiment of
In addition to the design library 350, the VSD configuration module 310 may have access to the VSD material library 360. The VSD material library 360 may be incorporated or integrated with, for example, the design library 360. The VSD material library 360 may carry data about the pertinent characteristics, including the electrical characteristics, of various types of VSD material. For example, the VSD material library 360 may carry information that references a type of VSD material to a characteristic voltage level, reference measurement of leakage current (or off-state resistance), and required gap distances to that result in a given threshold voltage for switching the material on. The threshold voltage may be used in identifying the level of ESD protection that can be provided by the particular type of VSD material applied across the stated gap distance.
With use of design library 350 or VSD material library 360, the design parameters 312 may be identified from explicit designer input (i.e. explicitly), or inferred or determined programmatically from other input. According to an embodiment, the design parameters 312 may include spatial constraint parameters 322, which includes data that may infer or identify preferred dimensions of interconnectivity or spacing amongst elements. As an addition or alternative, the spatial constraint parameter 322 may expressly define the spacing of VSD material and/or the availability of protective grounding elements and/or other features. As mentioned, the spatial constraint parameters 322 may be based on spatial information that is explicitly provided the designer, or inferred from other information, including the use of the design library 350. For example, the designer may specify a type of circuit board, and the spatial constraint parameters may be identified by cross-referencing the type or circuit board with the design library 350. Thus, for example, a circuit board for a particular kind of application may be associated with a default size range, such as by a value (e.g. “small”).
Another one of the design parameters 312 may correspond to tolerance parameters 324. The tolerance parameters 324 may include voltage and/or current values that define, amongst other limits, one or more of the following: (i) operational voltage ranges of some or all of the devices, (ii) break-down voltages for such devices, and/or (iii) tolerable leakage currents. In one embodiment, the VSD configuration module 310 uses the design library 350 to access information that cross-references specific components that are included on a board or device with their respective tolerance parameters 324. In this way, the tolerance parameters for a device under design or simulation may be determined through input provided by the user, including input corresponding to component selection. The components for use on the device may be also be determined by default or association with other components or input from the user. For example, the designer (or the design library 350) may include information in the form of government regulations or industry standards that require tolerance values that exceed those of the specific devices. Likewise, the designer (or design library 350) may incorporate information relating to factors of safety, or include other conditions from which one or more tolerance levels may be inferred. The tolerance parameters 324 may also be analyzed or subjected to various determinations. For example, tolerances 324 may be regionalized on the substrate device (e.g. voltage tolerance in one region of a substrate may differ from tolerance in another region), or processed to determine lowest or critical values (e.g. the voltage value at which one component will breakdown).
Numerous other design rules or implementation characteristics may be accounted for by the VSD configuration module 310 in its determination of the implementation details for VSD material. For example, design rules, regulations or other factors may set ESD parameters, which may limit the tolerance to voltages that the device as a whole may experience, or alternatively, a specific component or region of the device may experience.
The VSD configuration module 310 uses the various design parameters 312, in connection with VSD material library 360 (and design library 350), to determine implementation details 332 that include one or more of the following: (i) gap value 342, (ii) area determination 344, (iii) shape determination 346, and/or (iv) type determination 348. Other determinations may also be determined, such as volume determination, location determination, or cost range or limits. According to one or more embodiments, each of these determinations may be made based on any one or more of the design parameters 312. For example, the spatial parameter 312 may set constraints on the gap value 342.
However, calculations may be required to ensure the gap value 342 does not result in the threshold voltage level for switching the VSD material on to be too high. The calculation may be determined by identifying the characteristic voltage level of the particular VSD material identified by the type determination 348, and then determining a product value of the characteristic voltage level (per designated length) and the gap value (in terms of the designated length). The determined threshold voltage for the deposit of VSD material (as identified by the type determination 348) across the gap identified by the gap value must also result in a threshold voltage level that is less than the breakdown voltage of components that are to be protected. A factor of safety may also be applied to the breakdown voltage to ensure the threshold voltage level switches on before a damaging event.
Likewise, the type determination 348 may be used to identify leakage or off-state resistance values for a selected VSD material, and the gap value 342 may be used to calculate the leakage current that results from use of the VSD material (leakage current decreases and off-state resistance increases with greater the gap value 342). The resulting leakage current may be compared against tolerable leakage current levels to ensure that the leakage current is less than permitted tolerance levels. In some cases (such as when optimization is performed), some implementation details 332 may dependent on the determination of other implementation details.
The gap value 342 may correspond to a distance of separation provided by VSD material that extends between a conductive element that is to be protected and a protective electrical path. The gap value 342 is illustrated with an embodiment of
The area determination 344 may correspond to a planar measurement of VSD material that provides the gap value 342. While the gap value 342 is the primary factor in determining the overall voltage level for a given type of VSD material, the overall area occupied by the VSD material may increase leakage current and possibly affect the on-voltage level. An embodiment of
The shape designation 346 may specify the default shape from which area determination 344 is provided (e.g. concentric ring), or alternatively act as a modification to the default shape. In one embodiment, for example, the VSD material may be assumed to form a concentric ring or oval about a protective electrical path. The shape designation 346 may modify the default shape with contours so as to reduce the overall area, while maintaining the gap value 342 and the general diameter or size of the conductive element (e.g. grounding via) that is being surrounded. With reduction of area, the shape designation 346 may offer benefits such as decreasing the leakage current from the VSD material deposition. The shape designation 346 may be determined from, for example, use of spatial constraint parameter 322, and possibly motivated by one or more tolerance parameters 324 that indicate lowering of the leakage current is desired or warranted.
The type determination 348 specifies the composition of VSD material that is to be used. Numerous different compositions exist for VSD material, with varying electrical characteristics and mechanical properties. In particular, the characteristic voltage level and the leakage current vary considerably amongst different types of VSD material. The desired electrical characteristics, which may be determined from design parameters 312, may be referenced against the VSD material library 360 to identify one or more types of composition. Other input or considerations, such as desired mechanical properties (e.g. strong adhesion to copper) or cost may also influence the selection.
In a step 410, one or more user-input parameters are received. The user-input parameters may range, depending on implementation detail, from simple to detailed or complex. According to one or more embodiments, the user-input parameters may correspond to one or more of the following: (i) a designer selection to include VSD material protection as an integrated component on the substrate for protection against transient electrical events such as electrostatic discharge, and/or (ii) selection of a specific type of substrate that includes, for example, pre-deposited layer of VSD material. As an alternative or addition, the designer-input may correspond to explicit input in the form of design parameters 312 of an embodiment of
Step 420 provides for identification and implementation of design rules for a particular simulation or design. The design rules may be selected by, for example, the particular application, substrate or other parameters. The design rules may specify various conditions and criteria, including protective requirements of individual components or the device as a whole, and/or specification of specific components or types of components that are to be included on the substrate. As an example, the design rules may specify, for a circuit board in a particular application (such as for a wireless device), (i) specific components on the board, (ii) ESD protective requirements for individual components, regions or the entire board; (iii) spatial constraints or parameters on the board, (iv) thickness and other dimensions of the board. In one embodiment, the design library 350 maintains different sets of design rules for various applications that can be designed or simulated by a program implementing a method of
In step 430, one or more design parameters are programmatically determined, based on the inputs and identifications made in one or both of step 410 or step 420. The determination of such design parameters may result from input from the designer, and other logic in connection with the design library 350 and/or VSD material library 360, to determine any one or more of the design parameters 312. Thus, for example, the design library 350 may set the requirements for breakdown voltage based on industry or legal standard, as well as on the presence of one or more sensitive components that the designer has selected to use. Likewise, the spatial parameter 322 may be inferred by referencing the type of device that the designer is creating.
In step 440, the implementation details of the VSD material is determined. The implementation details may include any of the implementation details 332 such as described with an embodiment of
According to an embodiment, once determinations of implementation details is made, the remainder of the design and/or simulation may be performed with the program incorporating or including anticipated behavior and characteristics of the VSD material (as implemented). Thus, for example, a designer may build a remainder of a circuit board. As an alternative or addition, a simulator may anticipate ESD events and determine the results of such unplanned events on the operation of the device.
VSD Material Implementation Ata Protective Path
In the presence of a surge or other high voltage, however, the VSD material 540 switches into a conductive state. In the conductive state, the charge from the event is carried to the protective conductive path 520, which may be a ground. In the implementation shown, for example, the protective conductive path 520 is a via extending to an integrated grounding plane positioned within a thickness of the substrate device. As is inherent in the property of VSD material, the transition from dielectric to conductive occurs nearly instantly, so that even in the short time frame of an ESD event, the VSD material 540 becomes conductive before an electrical component connected to the conductive element 510 can be damaged by the ESD event. Thus, the VSD material 540 is able to protect the substrate from the ESD event, by connecting the conductive element 510 to the protective electrical path 520. But this connection only occurs when a transient electrical event of sufficient magnitude occurs. As such, the connection formed across the gap may be termed a transient electrical path 508.
In particular, the transient electrical event must be of a magnitude that exceeds a threshold (or “on”) voltage of the VSD material 540. The threshold voltage refers to a minimum voltage that is likely to switch a given deposit of VSD material from dielectric to conductive. If the voltage is on the low-end of the threshold where switch should occur, depending on composition and duration of the event (i.e. power), as well as potentially other factors, the occurrence of the switch may be less than certain. Thus, an embodiment may include a safety factor that places the “on-voltage” of the material well below the breakdown or tolerance voltage of the elements that are being protected.
The determination or estimate of the threshold voltage needed for a given deposit may be determined in part by the characteristic voltage per designated length or amount of the given material. For purpose of the gap value 515, the threshold voltage corresponds to a product of the gap value 515 and a known or estimated characteristic voltage of the VSD material that is being used. In particular, the characteristic voltage may be provided for a given designated length, and the gap value 515 may be defined in terms of the same designated length (e.g. mils). When voltage tolerances are considered or included as one of design parameter 312 (
The Factor of Safety is assumed to be less than 1.0.
The relationship ensures that the transient electrical path 508 is present when electrical events apply potentially damaging voltage levels. This ensures, for example, that the conductive element 510 may be grounded, but only in the presence of an otherwise harmful voltage level.
The various types of VSD material may be distinguished by their compositions, as well as their electrical and/or mechanical properties. As previously noted, the electrical properties include trigger or clamp voltages that make the material conductive. The mechanical properties include the physical nature of the material, which may be based on its composition. One or more embodiments provide for the programmatic determination of the gap value 515 from a selected or pre-selected type of VSD material 518. For example, under one implementation, the designer may have a preference for a particular type of VSD material because of its material properties (e.g. strength to bond with copper, non-brittleness) or aesthetics. The gap value 515 may be calculated with consideration of the characteristic voltage level of the selected VSD material, and the necessary threshold or “on-voltage” to protect the necessary components or elements of the device.
Under another implementation, a program may be configured to select the least costly VSD material that can provide the desired electrical characteristics. The desired electrical characteristics may be determined by, for example, input from the designer and/or the designer library 350 (
Various other parameters or input may be used to enable the identification of a particular VSD material 518. Each type of VSD material may have a different known or estimated characteristic voltage per designated length. Thus, some types of VSD material may require smaller or larger gap values 515 to provide the desired product or threshold trigger voltage value for an electrical event.
While an embodiment such as described above provides for determination of gap value 515 from the electrical properties of the VSD material 540, other embodiments provide that the gap value 515 is a criteria for the selection of the VSD material. For example, one of the design parameters 312 (
A separation 585 between the conductive element that is to be protected and the antipad 582 may be defined by a gap value 575. The gap value 575 may be determined in a manner such as described with an embodiment of
As with other embodiments, conductive path 610 that is in need of protection may be separated from the antipad 622 by an area that is defined in part by a gap separation 625. A gap value (such as determined with an embodiment of
In particular, embodiments recognize that size of the antipad 622 may be increased or decreased without affecting the gap value representing the size of the separation 625.
Thus, as illustrated by an embodiment of
In one embodiment, a default shape may be assumed to be an annular ring or oval, such as shown and described with an embodiment of
For each locations determination 812, considerations such as described with embodiments of
Under embodiments described herein, any of the implementations of VSD material described with embodiments of
Individual layers 902, 904, 906 may include elements (in the form of traces or components) that are to be protected by transient electrical condition. A via 930 may intersect the layers and provide a ground or other protective electrical path. According to an embodiment, multiple gap values may be determined to define the separation of different conductive elements and the protective electrical path, under an embodiment such as described. A first gap value 915 may define the separation between a first conductive element 910 (on layer 902) and the via 930. As described with embodiments of
A second gap value 917 may define a separation between a second conductive element 912 (on layer 904) and the protective electrical path, which may include the first electrical element 910. The actual measurement of the first and second separations may be different, and reflected by the first gap value 915 and second gap value 917. In an implementation shown by
Display Backplanes and Devices
Embodiments described herein include may be implemented in various applications, such as printed circuit boards. Additionally, as described with an embodiment of
In general, the process of selecting VSD material and designing its integration into a device is a mufti-variable consideration in which selection of one desired result may have negative impact to another result. For this reason, an embodiment provides for a prioritization or selection scheme by which a designer may specify one desired characteristic, variable or result over another. More specifically, in the process of determining implementation determinations 332 (See
The cost parameter 1112 may reflect the process by which the cost of integrating VSD material into a substrate device is minimized. Factors that may influence the overall cost include the cost of a particular VSD composition, as well as the amount of VSD material from the composition that may be needed. For example, some VSD compositions may require less material, by for example achieving desired performance characteristics using small gap distances and areas. Additionally, some VSD material may be easier to integrate with a device than others. For example, some substrates may include pre-formulated VSD material as a layer within or near a surface of the substrate, so that the addition of another layer after pre-fabrication is more expensive than the use of the pre-formulated VSD material. Thus, more than one factor may influence the cost parameter 1112. The cost parameter 1112 may be provided as either a composite value, or a mufti-dimensional parameter having variables that affect the cost of using a particular type of VSD material.
In one embodiment, the cost parameter 1112 may be used to select the VSD material (and thus influence the VSD designation 348). As an alternative or addition, the cost parameter 1112 may influence location determinations 812 (see
The quantity parameter 1114 may correspond to a priority to reduce the quantity of VSD material in use on the board. Lesser amounts of VSD material may be desired in the case when, for example, the environment where the VSD material is to be deposited is crowded. In a crowded environment, even small amounts of separation gaps for VSD material may be costly. In order to perform optimization based on the quantity parameter 1114, for example, an embodiment provides that the optimization module 1100 uses the output of the VSD configuration module 310 (
But as described with examples such as provided with
Still further, the optimization module 1100 may optimize to enhance a specific performance characteristic 1116. For example, for sensitive equipment, the VSD material that can be configured to provide the lowest amount of threshold voltage may be selected. This material may, for example, provide the desire characteristic at a low gap separation, while having a leakage current that is within the device's tolerance. Thus, even when performance is considered, the optimization module 1100 may require output of various VSD implementations to select or influence selection of a particular type of VSD material. Examples of performance characteristics include (i) negative presence of capacitance, (ii) impedance, and (iii) heat loss. Any of the optimization processes may optimize for one of these characteristics.
Optionally, the system 1200 may be coupled to a manufacturing interface 1250. The processing resources 1210 may communicate 1210 implementation configurations 332 (
The following section provides an implementation example that incorporates one or more embodiments described herein.
A printed circuit board (PCB) may be designed using software (such as an EDA application) configured in accordance with embodiments described herein. The design of the printed circuit board may call for integration of VSD material, for purpose of providing protection against potentially harmful and transient electrical events such as ESD. The PCB design may call for use of three chips, each of which has a different set of tolerances for ESD, leakage current or other electrical properties. Table 1 shows examples of recommended or manufacture-stated tolerances for individual chips. The identified tolerances are for ESD and for off-state resistance. As mentioned elsewhere, the off-state resistance also infers leakage current tolerance. In an embodiment, information provided with Table 1 may be listed in the design library 350 (see
An embodiment provides for the programmatic identification of a candidate type of VSD material. As a candidate, the VSD material may not be fully processed to determine whether all of the tolerances and criteria for integrating the VSD material have been satisfied. In analyzing the VSD material as a candidate, electrical properties may be identified in reference to a stated linear dimension, which in the examples provided, is a 1 mil gap. To analyze the voltage level at which the VSD material is turned on, the characteristic voltage level is normalized as the voltage needed to switch the VSD material on when applied across a 1 mil gap. The threshold voltage level (the total voltage needed to switch a quantity of the VSD material on) is then calculated from a product of the characteristic voltage level (per mil) multiplied by the size of the gap (also measured in mils).
For leakage current/off-state resistance analysis, the following relationships are generally applicable for VSD material: (i) higher gap sizes have greater off-state resistance and less leakage current, and (ii) higher operational voltages have lower off-state resistance and greater leakage current.
Both relationships of
With these relationships in mind, an embodiment provides that the VSD material of the first type may be analyzed as a candidate for integration in a substrate device by first determining the size of the gap separation required between each chip and its ground in order to provide the necessary voltage protection against ESD events. The necessary voltage protection requires the threshold voltage level of the VSD material to turn on at a voltage that is below the breakdown voltage, as modified by a safety factor. Under an embodiment, once the size of the gap separation is determined, the size of the gap separation may be used to determine the off-state resistance and/or leakage current.
Following the example provided, the VSD material of Type I may have the characteristic voltage level of 113 volts/mil. The off-state resistance may also be expressed in terms of an equation:
In the example provided, Equation (2) applies for components that have operating voltages in the range of 12 volts. As shown by
Table 2 illustrates results of integrating VSD material on the PCB, with its known or assumed electrical characteristics of clamp voltage and its off-state resistance. As mentioned, an embodiment provides for determining the size of the gap separation to satisfy the ESD requirements, and then cross-referencing the size of the gap separation to determine off-state resistance and/or leakage current. Table 2 summarizes the results:
Table 2 shows that in order to achieve the desired ESD protection for Chip 1 on the PCB, the gap separation formed by including the VSD material between (i) Chip 1 and a ground or other protective element would need to be 1.42 mils, (ii) Chip 2 and the ground would be about 3.54 mil, and (iii) Chip 3 would be at 7.09 mil. Under Equation 2, however, the VSD Material Type I fails the off-state requirements of Chip 1.
Under an embodiment, when one component fails, the configuration module 310 (see
Table 3 provides the results for using the VSD Material Type II with to provide a transient connection to ground for Chip.
While embodiments described herein provide for determination, in a design or simulation medium, of VSD material or its characteristics for purpose of handling ESD or overvoltage conditions, other embodiments provide that the logic or software makes a determination as to whether VSD material it to be used. For example, the user may specify conditions and parameters that make the use of ESD protection unwanted, in which case logic may make a determination to not include VSD material in the design of the device.
Although illustrative embodiments of the invention have been described in detail herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments. As such, many modifications and variations will be apparent to practitioners skilled in this art. Accordingly, it is intended that the scope of the invention be defined by the following claims and their equivalents. Furthermore, it is contemplated that a particular feature described either individually or as part of an embodiment can be combined with other individually described features, or parts of other embodiments, even if the other features and embodiments make no mentioned of the particular feature. Therefore, the absence of describing combinations should not preclude the inventor from claiming rights to such combinations.