US 3895207 A
Free paths are burnt into metalization layers upon insulator foils, for instance capacitor foils, by applying a high-frequency relatively low voltage to a burning electrode, while placing the electrode in direct contact with, and moving it with respect to, the metalized foil. Thereby, the contact part of the electrode is continuously renewed.
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Description (OCR text may contain errors)
United States Patent [1 1 Heywang et a1.
AVAILABLE C 1 1 [451 July 15, 1975 METHOD AND DEVICE FOR THE PRODUCTION OF METAL-FREE PATHS ON METALIZED INSULATOR FOILS  Inventors: Hermann Heywang, Munich;
Manfred Kobale, Faistenhaar; Gerhard Seebacher, Munich, all of Germany  Assignee: Siemens Aktiengesellschaft, Berlin & Munich, Germany  Filed: Apr. 10, 1974  Appl. No.: 459,621
 Foreign Application Priority Data Apr. 13, 1973 Germany 2318754  U.S. Cl 219/68; 219/119  Int. Cl B23p 1/20  Field of Search 219/68, 83, 119, 383, 384
 References Cited UNITED STATES PATENTS 2,435,441 2/1948 Grouse 219/68 X 2,671,157 3/1954 Dubilier 219/68 3,013,140 12/1961 Nunn 219/68 X 3,119,919 l/l964 Pratt 219/384 3,585,338 6/1971 Rosenthal 219/68 3,596,043 7/1971 Sporri 219/83 Primary Examiner-J. V. Truhe Assistant ExaminerN. D. l-lerkamp Attorney, Agent, or F irmHill, Gross, Simpson, Van Santen, Steadman, Chiara & Simpson [5 7 ABSTRACT Free paths are burnt into metalization layers upon insulator foils, for instance capacitor foils, by applying a high-frequency relatively low voltage to a burning electrode, while placing the electrode in direct contact with, and moving it with respect to, the metalized foil. Thereby, the contact'part of the electrode is continuously renewed.
13 Claims, 1 Drawing Figure METHOD AND DEVICE FOR THE PRODUCTION OF METAL-FREE PATHS ON METALIZED INSULATOR FOILS BACKGROUND OF THE INVENTION called a burn path, into metalization layers upon insulal0 tor foils and more particularly, to a burning electrode for the production of metal-free margins for electric capacitor foils.
2. Prior Art A means has been devised in the past where pinshaped burning electrodes are used in a recorder of relatively low writing speeds. However, such a burning electrode cannot be used to burn away the narrow metal-free margins of capacitor foils because of the 'small contact pressure required in order to avoid that the insulator foils carrying the metalized foils are destroyed during the burning process. Depositions upon the electrodes, however, would have to be removed by a great contact pressure or avoided by the use of relatively high voltages. The high voltages, in turn, burn wide and more or less jagged margins due to the high production speeds of the foil and since each light-arch discharge lasts a finite time. Valuable portions of the metalized foil may be lost, and the insulator foil may be damaged due to strong localized heating, in particular if the foils are very thin.
It has therefore been found desirable to provide a burning electrode which is able to produce long uninterrupted burn paths of an even width as inexpensively as possible.
SUMMARY OF THE INVENTION It is an important feature of the present invention to provide a method for burning relatively narrow paths into metalization layers disposed upon insulator foils, in particular fast moving foils.
It is also a feature of the present invention to provide devices for carrying out the above method to obtain best results under differing conditions.
It is a principal object of the present invention to provide a device producing narrow metal-free paths in capacitor foils by using a high-frequency relatively lowvoltage burning electrode which is in direct contact with the metalized foil and is moved with respect to the metalized foil.
It is another object of the present invention to provide a device whereby the electrode and the metalized foil move along the same path at different speeds and the electrode moves at a rate determined by the burning of the electrode so as to obtain a perfect burning path in the capacitor foil.
These and other objects, features and advantages of the present invention will be understood in greater detail from the following description and the associated drawing wherein reference numerals are used to designate a preferred embodiment.
BRIEF DESCRIPTION OF THE DRAWING The FIGURE is a schematic view of a preferred device according to this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a method and a device for burning free paths into metalization layers disposed upon insulator foils, whereby these foils move at high production speeds.
In accordance with a preferred embodiment of the present invention, a high-frequency relatively low voltage is applied between a metalized foil and the burning electrode. The burning electrode and the metalized foil are pressed against one another and against a guide roller, and the burning electrode is moved with respect to the guide roller, so that the contact portion of the burning electrode is continuously renewed.
The continuous renewal of the contact portion of the burning electrode permits the use of a low voltage since the foil material which deposits upon the electrode during the burning process cannot interrupt the current. The advantage of a low voltage is an exact path margin. Arc discharges are almost entirely avoided, and the metal is removed only in the electrode area.
A relatively high frequency permits a capacitive coupling between the metalized foil and the corresponding electrode, even if the electrode contacts the metalized foil directly. This is due to impurities or oxide layers. The direct contact between the electrodes and the metalized foil is another factor permitting the decrease of the burning voltage since little air resistance has to be overcome. The direct contact between the electrode and the metalized foil also results in a more perfect burn path.
The method of this invention can also be used to burn paths into metalizations covering both sides of an insulator foil.
In a preferred embodiment of the invention, the burning electrode is applied in the area of one of several guide rollers, and at least one of these guide rollers is in contact with'the metalized foil. If the frequency is high, the capacitive resistance between the roller and the metalized foil is so small that a current concentration, which may occur in the case of an arc discharge, cannot destroy the metalized foil. A fairly large basic frequency of at least approximately kHz (100,000 cycles/sec) should be used with a common capacitor foil and a roller diameter of approximately 6 cm.
According to a preferred embodiment of the invention, a sinusoidal alternate voltage is used, but a direct voltage with animpulse frequency of at least approximately 100 kHz is also applicable. The quality of the impulse shape is not particularly important.
In accordance with one embodiment of the invention, a rotating electrode is used, and the burning process is started with a relatively high current, due to a correspondingly high voltage, and this current is gradually decreased after the beginning of the burning process. Thus, the burn path obtains a perfect start, while the use of a lower voltage avoids that the path becomes too wide.
If the insulator foil advances at a relatively low speed, these electrodes may be roll-shaped, while endless tapes or wires are required with the higher advance speeds as they are common in the production of capacitor foils. The contact parts of the electrode are cleaned before they are reused. This may be done by way of wiping.
A speed of 0.1 mm/sec suffices for a burning electrode as described above, in the insulator material foils is moved at a high production speed, for instance 1 m/sec. If an aluminum layer has a conductivity of 0.5 Siemens (Mhos), and the insulator material foil has a thickness of approximately 3.5 pm, a sinusoidal highfrequency voltage of approximately 500 kHz and an effective value of 12 Volts is most advantageous. A common HF-tube transmitter may be used, and the low voltage is particularly important when thick foils are burned is obtained with a correspondingly designed transformer. It is also possible to apply transistor voltage sources.
When higher voltages are applied, arch discharges tend to make the burn path much wider than the width of the burning electrodes. If, for instance, a voltage of 40 Volts is applied to a tape-shaped burning electrode of 0.5 mm width, a burning path of 0.9 mm width is produced, while a lower voltage of, for instance, 12 Volts results in a path which is only approximately 50 um wider than the width of the burning electrode. However, if the tape is slightly bent, and its margins do not contact the foil, the figures obtained are quite different.
Relatively high currents must be used with fairly thick metalizations foils having, for instance, a surface conductivity of approximately Siemens. these metalized foils are advantageously applied to carrier foils of approximately 40 um thickness.
The burning process is started with a relatively high voltage of approximately 30 Volts. This is due to the fact that the current dissipates at first via the conductive metal layer. Particularly in the case of thick carrier foils, an additional contact via one of the guide rollers is desired or required.
According to one embodiment of the invention, the plastic foil contacts one of the guide rollers, while the burning electrode is pressed against the metalized foil upon this guide roller. Thereby, the electric resistance is made as small as possible by providing the burning electrode with a smooth contact surface. The heat capacity of the burning electrode must be as large as possible, so that the current or the evaporating metal cannot damage the electrode.
According to a further embodiment of the invention, relatively narrow burn paths of approximately 0.1 mm are produced, whereby the electrode is a metal wire of a somewhat larger diameter than the width of the burn path.
According to another embodiment of the invention, a burn path, which is wider than approximately 0.7 mm is produced by an electrode made ofa metal tape of approximately the same width. Such a metal tape can be relatively easily bent perpendicular to its width, and thus it does not require great contact pressures. This is particularly important when thin plastic foils are used which may be easily damaged. An additional advantage of this arrangement is that the tape may contact the metalized foil at a somewhat larger length upon the circumference of the guide roller, if such a roller is used,
whereby interruptions of the path are avoided which may be due to vibrations.
A burn path of approximately 0.6 mm may be produced with common impulse voltages of an amplitude of approximately 60 volts. Herefore, a wire of approximately 1 mm could be used or a metal tape of approximately 0.5 mm width. If the wire or the metal tape consist of the same material, their bending forces are.re-
lated in proportion to their moments of inertia (I). The moment of inertia of a wire (1 and the moment of inertia of the rectangular tape (1:1) are the following, whereby a is the tape thickness and b is the tape width;
Wire: 1 (1 /64, Rectangular tape: I a b/l2.
If the values d equals 1 mm, b equals 0.5 mm, and a equals 0.05 mm, the following is obtained:
The force required to deform a tape is thus only approximately 1 /10,000 of that required to bend a round wire.
In view of the above, metal tapes are more advantageous when the electrode width is more than 0.4 mm, whereby silver-coated copper tapes of 30 am thickness are most advantageous. Nickel ferrite tapes are more suited for narrower burn paths, due to their greater tensile strength. They should have a thickness of approximately 50 ,um. 1f the width of the burn path is 0.3 mm, the tape width should be 0.25 mm and its thickness 50 If a preferred voltage of 12 Volts is applied to a metalized foil with a conductivity of 0.5 Siemens, the width of the burn path will be approximately 50 am more than that of the metal tape.
If the electrode is particularly wide, plastic tapes with an aluminum coating and a surface conductivity of at least 10 Siemens are particularly suited. It is also possible to replace the aluminum layer by carbon or graphite layers. Such electrodes are advantageous when relatively wide paths are burnt into thin insulator foils, for instance approximately 2 mm wide burn paths.
The electrodes may be supplied from a roll and transferred onto another roll during the burning process. This embodiment is suited when very narrow and sensitive electrodes are used which cannot be easily cleaned.
If several burn paths are produced, they should be arranged next to one another, while being connected with outputs of alternate voltage sources or impulse generators.
According to an advantageous embodiment of this invention, the burning electrodes are arranged adjacent to a cutting device, for instance approximately 5 cm away from this cutting device, so that the insulator foil can be split in the center of the burnt path.
It is illustrated in the FIGURE that an insulator material foil 1 carrier a metalization layer 2 and moves via the guide rollers 3 and 4 which are grounded. The guide roller 3 contacts the metalized foil 2.
A metal tape 5 serves as burning electrode and contacts the metalized foil 2 upon the guide roller 4, whereby it partially embraces the roller. 4. Terminal 11 contacts both the supply roll 6 and a pole of a burning voltage, and the electrode 5 is rolled from the supply roll 6 onto the roll 7. The electrode 5 moves slowly with respect to the area 12 where it contacts the metalized foil 2, in a direction opposite to the moving direction of the insulator material foil 1. Tape guides 8 and 9 prevent a lateral movement of the metal tape 5.
According to an advantageous embodiment, the tape guide 9 is embodied as a roller with a guide groove. This embodiment is particularly suited for a burning electrode operating at low advance speeds or for a burning electrode which is to be used for relatively thick metalizations. The embodiment of guide 9 as a roller permits a perfecttransport of the electrode 5, even as metal has deposited thereon. The arrangement according to the FlGURE results in a perfect burn path 10 upon the insulator foil 1.
It will be understood that these embodiments of the invention have been described for illustrative purposes only and that various modifications and variations in the invention may be made without departing from the spirit and scope of the novel concepts thereof.
1. Method of producing free paths in metalizations upon insulator foils, comprising the steps of applying a relatively low voltage of a high frequency between a guide roller and a burning electrode and pressing a metalized foil against the guide roller to form a capacitive coupling between the guide roller and the metalized foil;
pressing the burning electrode against the metalization of the metalized foil; and
moving the burning electrode with respect to the metalized foil, thereby continuously renewing the contact portion of the electrode. 2. A method in accordance with claim 1 wherein an alternating voltage with a basic frequency above 100 kHz is applied to the guide roller.
3. A method in accordance with claim 2 wherein a relatively high burning current is initially applied and is decreased after the beginning of the burning process.
4. A method in accordance with claim 1 wherein a pulsed direct voltage with an impulse frequency above 100 kHz is applied.
5. A method in accordance with claim 1 wherein a relatively high burning current is initially applied and is decreased after the beginning of the burning process.
6. A method in accordance with claim 16 wherein a burning electrode is applied, said electrode moving with respect to the metalized foil, and the contact parts of the burning electrodes are continuously freed from the metal deposited thereupon.
7. A device for producing metal-free strips in metal layers disposed upon insulator foils, comprising:
at least one-guide roller; and
at least one burning electrode contacting the metalization and moving with respect to the metalized foil directly and continuously replacing its contact portions, wherein the burning electrode is a tape or wire, wherein a groove guide roller guides the used portion of the electrode and wherein the burning electrode is bent partially around another guide roller.
8. A device in accordance with claim 7 wherein the electrode is formed of silver-coated copper.
9. A device in accordance with claim 7 wherein the electrode is formed of nickel ferrite.
10. A device in accordance with claim 7 wherein the electrode is formed of aluminum-coated plastic.
11. A device in accordance with claim 7 wherein the electrode is formed of a graphite-coated plastic.
12. A device in accordance with claim 7 wherein a the electrode is formed of a carbon-coated plastic. 13. A device in accordance with claim 7 wherein several electrodes are applied simultaneously, each of said electrodes having its own voltage contact.