WO2000030418A1 - Carbon coating method for electromagnetic shielding of electronic circuit boards to provide electromagnetic compatibility - Google Patents
Carbon coating method for electromagnetic shielding of electronic circuit boards to provide electromagnetic compatibility Download PDFInfo
- Publication number
- WO2000030418A1 WO2000030418A1 PCT/TR1999/000045 TR9900045W WO0030418A1 WO 2000030418 A1 WO2000030418 A1 WO 2000030418A1 TR 9900045 W TR9900045 W TR 9900045W WO 0030418 A1 WO0030418 A1 WO 0030418A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- printed circuit
- circuit board
- electronic
- high conductivity
- layer containing
- Prior art date
Links
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 22
- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 22
- 238000000576 coating method Methods 0.000 title claims abstract description 5
- 238000000034 method Methods 0.000 claims abstract description 22
- 239000003973 paint Substances 0.000 claims abstract description 14
- 238000002955 isolation Methods 0.000 claims abstract description 6
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 3
- 239000010949 copper Substances 0.000 claims description 3
- 229910052802 copper Inorganic materials 0.000 claims description 3
- 230000005670 electromagnetic radiation Effects 0.000 claims description 3
- 238000002360 preparation method Methods 0.000 claims description 2
- 239000011248 coating agent Substances 0.000 abstract 2
- 238000001035 drying Methods 0.000 abstract 1
- 239000000463 material Substances 0.000 description 12
- 229910052751 metal Inorganic materials 0.000 description 9
- 239000002184 metal Substances 0.000 description 9
- 230000035699 permeability Effects 0.000 description 6
- 238000004519 manufacturing process Methods 0.000 description 5
- 238000012216 screening Methods 0.000 description 5
- 230000008878 coupling Effects 0.000 description 4
- 238000010168 coupling process Methods 0.000 description 4
- 238000005859 coupling reaction Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 230000002238 attenuated effect Effects 0.000 description 2
- 239000004020 conductor Substances 0.000 description 2
- 238000009413 insulation Methods 0.000 description 2
- 239000000696 magnetic material Substances 0.000 description 2
- 230000005855 radiation Effects 0.000 description 2
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 239000004411 aluminium Substances 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 230000005672 electromagnetic field Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 239000004332 silver Substances 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K9/00—Screening of apparatus or components against electric or magnetic fields
- H05K9/0073—Shielding materials
- H05K9/0081—Electromagnetic shielding materials, e.g. EMI, RFI shielding
- H05K9/0092—Electromagnetic shielding materials, e.g. EMI, RFI shielding comprising electro-conductive pigments, e.g. paint, ink, tampon printing
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K1/00—Printed circuits
- H05K1/02—Details
- H05K1/0213—Electrical arrangements not otherwise provided for
- H05K1/0216—Reduction of cross-talk, noise or electromagnetic interference
- H05K1/0218—Reduction of cross-talk, noise or electromagnetic interference by printed shielding conductors, ground planes or power plane
Definitions
- the present invention relates to a shielding method designed to prevent undesired effects of electromagnetic radiation created by electronic circuit boards.
- metal screening One of the measures taken against electromagnetic interference in electronic devices is metal screening. Optimising the lengths and positioning of the lines and filtering are also two other important applications. These two last mentioned methods may be inefficient in keeping electromagnetic interference to the lowest level. Due to this fact, the coupling of electric, magnetic and electromagnetic fields present between two units within the same system is suppressed using metal screening method. A screen is located between two units to abate coupling.
- Metal screen covers used in prior art were too costly. In addition to this the application of the screening on the chassis was not easy and these methods were difficult to apply because of the necessity to realise the grounding at certain points of grounding lines. Shielding with a conducting material was a frequently used method to establish a system without interference. This method is generally accomplished by using nonmagnetic materials such as copper, silver or aluminium. Iron and steel are rarely used instead of non-magnetic materials. The screen is grounded with conductor of low ohmage. Here the aim is to prevent the occurrence of undesirable secondary radiation of induced currents on the screen.
- Another condition is to provide the shielding by covering the area with a shielding material.
- the metal plate thus used in shielding is effective but it is difficult to predict undesired effect caused by uncalculated electric and magnetic fields. Therefore whole shielding region is covered by the said metal.
- the object of hereby invention is to perform a shielding of electronic printed circuit boards using a method which requires few workmanship, simple ways of production and which brings ease in operation.
- Figure 1 is the sectional view of the stages of carbon printing application to electronic printed circuit boards.
- FIG 2 is the dispersed view of the stages of carbon printing application to electronic printed circuit boards.
- the descriptions of the components numbered in the figures are as follows;
- the hereby preferred method intends to solve the electromagnetic compatibility problem by covering electronic printed circuit board's (1) regions sensitive to electromagnetic interference with paint layer containing high conductivity carbon with appropriate parameters of density, thickness and conductivity.
- the electrical ground connection is done directly to provide the effectiveness of the shielding.
- a specific region of the electronic printed circuit board may be screened as well as the entire card surface. The method brings an advantage with regard to flexibility that it provides to production by enabling screening of surfaces of different size and shape.
- Carbon screen layer weakens electromagnetic wave passing through, due to the ohrnic losses which are calculated approximately using the formula set down under:
- Attenuation of undesired signal is changing with materials characteristics used in screening as well as with signal's frequency. Attenuation increases with root square of frequency. Attenuation of direct current in metals is zero and it depends on the following parameters:
- Attenuation level desired to a specific frequency is adjusted by choosing a specific resistivity of materials to be used in shielding and a magnetic permeability thereof. Since the relative magnetic permeability of the materials varies with the frequency, this fact is taken in regard when using magnetic materials.
- Paint layer containing high conductivity carbon reflects some portion of electromagnetic wave and causes attenuation of the signal passing through. Electromagnetic wave is reflected when passing from one environment to the other having different impedance characteristics. The magnitude of the reflection depends on the difference between the impedances of the environment and of the screen. Screen impedance is the surface impedance of the material used. It is then created an impedance incompatibility which will cause a reflection and therefore an attenuation with the paint layer containing high conductivity carbon. The losses created by the above incompatibility is calculated with the following formula;
- Zr environmental impedance (to vary between 10 and 1000 )
- the region to be shielded is prepared according to electronic printed circuit board film preparation techniques.
- the silk printing film is prepared as a separate layer after having masked the electronic circuit board (1) two times with insulation mask or after having masked the region only one time and then having covered it with an insulation coat.
- the silk printing film having paint layer containing high conductivity carbon on it is applied onto electronic printed circuit board (1) and dried and hardened after being heated in air-circulated furnace. The grounding is achieved by setting electrical contacts with copper surfaces during this hardening process.
- a shielding method is achieved by means of a paint layer containing high conductivity carbon and resulting with a solution which is easy, simple and requiring less workmanship. With the help of this method it is possible to perform shielding; 1. between lines
Abstract
Electromagnetic compatibility of an electronic printed circuit board (1) is being achieved by coating sensitive regions of electronic printed circuit board (1) with a paint layer containing high conductivity carbon (4). The coating with the said paint layer containing high conductivity carbon (4) is obtained by using 'silk printing' method of the paint layer containing high conductivity carbon (4) to electronic printed circuit board (1) covered either twice with isolation mask (3) or once with isolation mask (3) and then with an insulating coat and by drying the product thus obtained in an air circulating furnace.
Description
CARBON COATING METHOD FOR ELECTROMAGNETIC
SHIELDING OF ELECTRONIC CIRCUIT BOARDS TO PROVIDE
ELECTROMAGNETIC COMPATIBILITY
The present invention relates to a shielding method designed to prevent undesired effects of electromagnetic radiation created by electronic circuit boards.
It is a well known fact that electronic systems effect each other (intersystem interference) as well as the electronic units within these systems (intrasystem interference). The said problem becomes more important with the growing electronic industry. Therefore it is required to take severe precautions in both design and manufacture of electronic products. Furthermore, bandwidth of electronic circuits expanded as their operational rates grew and it makes electronic circuits more sensitive to interferences. On the other hand, the functions and in connection with these the complexities of the electronic devices have also increased. Integration of electronic circuits ease the electromagnetic interference.
It is highly required to lay emphasis on the above issues as well as on the isolation of the electronic systems from these interferences.
One of the measures taken against electromagnetic interference in electronic devices is metal screening. Optimising the lengths and positioning of the lines and filtering are also two other important applications. These two last mentioned methods may be inefficient in keeping electromagnetic interference to the lowest level. Due to this fact, the coupling of electric, magnetic and electromagnetic fields present between two units within the same system is suppressed using metal screening method. A screen is located between two units to abate coupling.
Metal screen covers used in prior art were too costly. In addition to this the application of the screening on the chassis was not easy and these methods were difficult to apply because of the necessity to realise the grounding at certain points of grounding lines.
Shielding with a conducting material was a frequently used method to establish a system without interference. This method is generally accomplished by using nonmagnetic materials such as copper, silver or aluminium. Iron and steel are rarely used instead of non-magnetic materials. The screen is grounded with conductor of low ohmage. Here the aim is to prevent the occurrence of undesirable secondary radiation of induced currents on the screen.
Another condition is to provide the shielding by covering the area with a shielding material. The metal plate thus used in shielding is effective but it is difficult to predict undesired effect caused by uncalculated electric and magnetic fields. Therefore whole shielding region is covered by the said metal.
With this method the components of the equipment which causes intersystem and/or intrasystem interference are kept in a metal box with appropriate thickness.
Such a method, though efficient in cases where far field couplings are present, proves itself insufficient for couplings of near field. Moreover, as it is required to have an extra metal box it is a costly method. The manufacturing of the metal box requires a mold production. This triggers additional costs for material and workmanship.
The object of hereby invention is to perform a shielding of electronic printed circuit boards using a method which requires few workmanship, simple ways of production and which brings ease in operation.
Covering with a paint layer containing high conductivity carbon for the accomplishment of the object of hereby invention is shown in the attached drawings, where:
Figure 1, is the sectional view of the stages of carbon printing application to electronic printed circuit boards.
Figure 2, is the dispersed view of the stages of carbon printing application to electronic printed circuit boards.
The descriptions of the components numbered in the figures are as follows;
(1) electronic printed circuit board
(2) electronic ground connection
(3) insulating mask
(4) paint layer containing high conductivity carbon
The hereby preferred method intends to solve the electromagnetic compatibility problem by covering electronic printed circuit board's (1) regions sensitive to electromagnetic interference with paint layer containing high conductivity carbon with appropriate parameters of density, thickness and conductivity. The electrical ground connection is done directly to provide the effectiveness of the shielding. In addition to this it is an easier and cheaper method. With this method, a specific region of the electronic printed circuit board may be screened as well as the entire card surface. The method brings an advantage with regard to flexibility that it provides to production by enabling screening of surfaces of different size and shape.
Carbon screen layer weakens electromagnetic wave passing through, due to the ohrnic losses which are calculated approximately using the formula set down under:
(1) Loss (dB) : d.0.13 ,where
d: screen thickness
f: frequency
.. relative magnetic permeability
.. relative specific resistivity (... square mm/m)
Attenuation of undesired signal is changing with materials characteristics used in screening as well as with signal's frequency. Attenuation increases with root
square of frequency. Attenuation of direct current in metals is zero and it depends on the following parameters:
* Frequency signal
* Thickness of material used in shielding
* Relative specific resistivity of shielding material
* Relative magnetic permeability of shielding material
Attenuation level desired to a specific frequency is adjusted by choosing a specific resistivity of materials to be used in shielding and a magnetic permeability thereof. Since the relative magnetic permeability of the materials varies with the frequency, this fact is taken in regard when using magnetic materials.
Paint layer containing high conductivity carbon reflects some portion of electromagnetic wave and causes attenuation of the signal passing through. Electromagnetic wave is reflected when passing from one environment to the other having different impedance characteristics. The magnitude of the reflection depends on the difference between the impedances of the environment and of the screen. Screen impedance is the surface impedance of the material used. It is then created an impedance incompatibility which will cause a reflection and therefore an attenuation with the paint layer containing high conductivity carbon. The losses created by the above incompatibility is calculated with the following formula;
(2) losses (dB): 20.log ( ), where
Zr: environmental impedance (to vary between 10 and 1000 )
Zs: screen layer surface impedance
Zs is calculated using the simple formula below:
(3) , where
f frequency
electromagnetic permeability of the gap
relative magnetic permeability of shielding material
relative specific resistivity of shielding material
The region to be shielded is prepared according to electronic printed circuit board film preparation techniques. The silk printing film is prepared as a separate layer after having masked the electronic circuit board (1) two times with insulation mask or after having masked the region only one time and then having covered it with an insulation coat. The silk printing film having paint layer containing high conductivity carbon on it, is applied onto electronic printed circuit board (1) and dried and hardened after being heated in air-circulated furnace. The grounding is achieved by setting electrical contacts with copper surfaces during this hardening process.
Due to the impedance incompatibility of the paint layer contairiing high conductivity carbon (4) some amount of electromagnetic wave is reflected, while some other is absorbed and the attenuated amount is let passed. The signal thus passed is the source of electromagnetic radiation. The level of this signal is kept at a desired level by adjusting conductivity level and thickness of carbon composition. The passing signal is absorbed due to the ohmic resistivity of the paint layer containing high conductivity carbon (4), therefore energy is converted to heat. Electric and magnetic field magnitudes are attenuated exponentially and independently from radiation direction.
With this invention, a shielding method is achieved by means of a paint layer containing high conductivity carbon and resulting with a solution which is easy, simple and requiring less workmanship. With the help of this method it is possible to perform shielding;
1. between lines
2. within and between systems
3. of the limited regions where it is difficult to be performed.
Claims
(1) A carbon coating method to provide electromagnetic compatibility of an electronic printed circuit board (1) characterized in that; the region to be shielded on the said electronic printed circuit board (1) to prevent the electromagnetic interference caused by the electronic equipment in which the said electronic circuit board (1) is used and/or by the electromagnetic radiation of the other external equipment, is prepared according to film preparation techniques and the said printed circuit board (1) is masked twice with an isolation mask (3), the silk printing film is prepared as a separate layer, the said silk printing film is painted with the layer containing high conductivity carbon (4) and is applied to said electronic printed circuit board (1), the grounding is achieved by means of the electrical contact with copper surfaces and the said electronic printed circuit board(l) is dried and hardened in an air-circulated furnace
(2) A method as specified in claim (1), characterized in that, in order to prevent the short circuits, the application of the said paint layer containing high conductivity carbon (4) to electronic printed circuit boards (1) is performed by silk printing.
(3) A method as specified in claim 1, characterized in that, in order to prevent the short circuits, the said electronic printed circuit board (1) on which the paint layer containing high conductivity carbon (4) will be applied, is first masked with one isolation mask (3) and then painted with an isolation coat.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| TR2001/01269T TR200101269T2 (en) | 1998-11-13 | 1999-11-15 | Carbon coating method for the electromagnetic shielding of electronic circuit boards to ensure electromagnetic compatibility |
| AU15950/00A AU1595000A (en) | 1998-11-13 | 1999-11-15 | Carbon coating method for electromagnetic shielding of electronic circuit boardsto provide electromagnetic compatibility |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| TR9802320 | 1998-11-13 | ||
| TR9802320 | 1998-11-13 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| WO2000030418A1 true WO2000030418A1 (en) | 2000-05-25 |
Family
ID=21621714
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/TR1999/000045 WO2000030418A1 (en) | 1998-11-13 | 1999-11-15 | Carbon coating method for electromagnetic shielding of electronic circuit boards to provide electromagnetic compatibility |
Country Status (3)
| Country | Link |
|---|---|
| AU (1) | AU1595000A (en) |
| TR (1) | TR200101269T2 (en) |
| WO (1) | WO2000030418A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2161974A1 (en) | 2008-09-09 | 2010-03-10 | Hegutechnik v. Gutwald KG | Bifunctional EMC coating |
| EP2519092A1 (en) * | 2009-12-22 | 2012-10-31 | Huawei Device Co., Ltd. | Method for shielding a printed circuit board and the printed circuit board thereof |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4490282A (en) * | 1983-02-18 | 1984-12-25 | Corboy Thomas A | Conductive paint composition |
| US5112648A (en) * | 1990-07-18 | 1992-05-12 | Nippon Cmk Corp. | Method of manufacturing a printed circuit board |
| US5220135A (en) * | 1989-03-15 | 1993-06-15 | Nippon Cmk Corp. | Printed wiring board having shielding layer |
-
1999
- 1999-11-15 WO PCT/TR1999/000045 patent/WO2000030418A1/en active Application Filing
- 1999-11-15 TR TR2001/01269T patent/TR200101269T2/en unknown
- 1999-11-15 AU AU15950/00A patent/AU1595000A/en not_active Abandoned
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4490282A (en) * | 1983-02-18 | 1984-12-25 | Corboy Thomas A | Conductive paint composition |
| US5220135A (en) * | 1989-03-15 | 1993-06-15 | Nippon Cmk Corp. | Printed wiring board having shielding layer |
| US5112648A (en) * | 1990-07-18 | 1992-05-12 | Nippon Cmk Corp. | Method of manufacturing a printed circuit board |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2161974A1 (en) | 2008-09-09 | 2010-03-10 | Hegutechnik v. Gutwald KG | Bifunctional EMC coating |
| EP2519092A1 (en) * | 2009-12-22 | 2012-10-31 | Huawei Device Co., Ltd. | Method for shielding a printed circuit board and the printed circuit board thereof |
| EP2519092A4 (en) * | 2009-12-22 | 2012-12-26 | Huawei Device Co Ltd | Method for shielding a printed circuit board and the printed circuit board thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| TR200101269T2 (en) | 2002-01-21 |
| AU1595000A (en) | 2000-06-05 |
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