Source: http://www.google.com/patents/US6350951?ie=ISO-8859-1&dq=6650327
Timestamp: 2014-08-27 13:37:17
Document Index: 644189605

Matched Legal Cases: ['arts 0', 'arts 0', 'art 15', 'art 15', 'art 15', 'art 15', 'art 15', 'art 15', 'application No. 08']

Patent US6350951 - Electric shielding of on-board devices - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign in<nobr>Advanced Patent Search</nobr>PatentsImproved electromagnetic compatibility for integrated motherboard or device board designs is provided by magnetic shielding, electric shielding, or both integrated into the chip packaging materials. Motherboard emissions may be reduced by use of the shielding. A nonconductive primary and tertiary layer...http://www.google.com/patents/US6350951?utm_source=gb-gplus-sharePatent US6350951 - Electric shielding of on-board devicesAdvanced Patent SearchPublication numberUS6350951 B1Publication typeGrantApplication numberUS 08/999,089Publication dateFeb 26, 2002Filing dateDec 29, 1997Priority dateDec 29, 1997Fee statusPaidPublication number08999089, 999089, US 6350951 B1, US 6350951B1, US-B1-6350951, US6350951 B1, US6350951B1InventorsRay AskewOriginal AssigneeIntel CorporationExport CitationBiBTeX, EndNote, RefManPatent Citations (4), Non-Patent Citations (9), Referenced by (18), Classifications (44), Legal Events (5) External Links: USPTO, USPTO Assignment, EspacenetElectric shielding of on-board devicesUS 6350951 B1Abstract Improved electromagnetic compatibility for integrated motherboard or device board designs is provided by magnetic shielding, electric shielding, or both integrated into the chip packaging materials. Motherboard emissions may be reduced by use of the shielding. A nonconductive primary and tertiary layer sandwich a high-conductivity metal secondary layer forming a Faraday cage for electric field shielding. A nonconductive primary layer is covered by a tertiary layer formed of a composite having permeable material for magnetic shielding. The tertiary layer formed of a composite could include a high permeability particulate ferrous material. Both the secondary layer and the tertiary layer formed of a composite could be used for both electric and magnetic shielding of chips.
What is claimed is: 1. A system encapsulating a device on a device board having a ground, comprising:
a first polymer layer covering and in contact with the device; a conductive material coupled to the ground and adjacent the first polymer layer; and a non-permeable encapsulant layer adjacent said conductive material and in contact with both said conductive material and said first polymer layer. 2. The system of claim 1, wherein the first polymer layer comprises nonconductive material.
3. The system of claim 1, wherein the first polymer layer comprises a composite matrix material.
4. The system of claim 1, wherein the first polymer layer comprises epoxy cresol nonvolac polymer.
5. The system of claim 1, wherein said non-permeable encapsulant layer comprises nonconductive material.
6. The system of claim 1, wherein the device comprises an integrated circuit coupled to the device board by bond wires.
7. The system of claim 6, wherein the integrated circuit comprises a silicon die.
8. The system of claim 1, wherein the first polymer layer covers a substantial portion of the device.
9. The system of claim 1, wherein said non-permeable encapsulant layer covers a substantial portion of the conductive material and the first polymer layer.
10. The system of claim 1, wherein the conductive material comprises foil material.
11. The system of claim 1, wherein the conductive material covers a substantial portion of the first polymer layer.
12. The system of claim 1, wherein the conductive material forms a Faraday cage.
13. The system of claim 1, wherein the conductive material provides electric shielding.
14. A method of encapsulating a device on a device board having a ground, the method comprising:
covering the device substantially with a first polymer layer, wherein the first polymer layer is in contact with the device; covering a portion of the first polymer layer with a single conductive material coupled to the ground; and covering a portion of the single conductive material and the first polymer layer with a nonconductive encapsulant layer in contact with both said single conductive material and said first polymer layer. 15. The method of claim 14, wherein covering a portion of the single conductive material comprises encapsulating the device.
16. The method of claim 14, wherein covering a portion of the single conductive material comprises covering the device with epoxy.
17. The method of claim 14, wherein covering the portion of the first polymer layer comprises covering with a foil material.
18. The method of claim 14, wherein covering the portion of the first polymer layer comprises covering the portion of the first polymer layer to provide electric shielding.
19. The method of claim 14, wherein covering the portion of the first polymer layer comprises covering a substantial portion of the first polymer layer with the single conductive material.
20. The method of claim 14 wherein covering the portion of the single conductive material and the first polymer layer comprises covering a substantial portion of the conductive material and the first polymer layer with said nonconductive encapsulant layer.
21. The method of claim 14, wherein covering the portion of the first polymer layer comprises covering the portion of the first polymer layer with the single conductive material to provide a Faraday cage.
22. A system encapsulating a device on a device board having a ground comprising:
a first polymer layer covering and in contact with a portion of the device; a grounded conductive material covering a portion of the first polymer layer, the grounded conductive material being a foil material; and a second polymer layer covering and in contact with both a portion of the conductive material and the first polymer layer, the second polymer layer comprising a composite material distinguishable from said foil material.
Motherboard designers today are faced with tighter electromagnetic compatibility (�EMC�) regulations than previously. The Federal Communications Commission (�FCC�) recently imposed the so-called �open box� electromagnetic interference (�EMI�) testing criteria. The open box criteria transfers responsibility to the manufacturer for the regulation of computer system (i.e., unintentional radiator's) radiated energy produced by on-board components, such as application specific integrated circuits (�ASICs�), from a shielded enclosure (e.g., a computer case or enclosure) housing the components to the internal components themselves, specifically a motherboard. Such emissions, which previously could be sufficiently attenuated by the shielded enclosure to satisfy the prior �closed box� regulations, must now be sufficiently attenuated without the shielded enclosure being completely closed. The exposed motherboard must thereby satisfy the open box regulations without relying on the shielded enclosure to provide sufficient attenuation. Otherwise, a given motherboard can only be marketed with a particular case if, when closed, the case reduces the emissions sufficiently.
With the open box criteria, the FCC changed the procedure for testing computer devices for radiated emissions. The FCC's regulations were incorporated in amendments to �15.32(a)(1) of Title 47 in the Code of Federal Regulations (�CFR�). These amendments were adopted for CPU boards or motherboards and power supplies. Because of difficulties associated with determining the efficacy of shielding with computer cases, the FCC did not adopt rules that authorize these enclosures. To ensure that computer systems assembled from modular components comply with the technical standards, the FCC adopted a two-step test procedure for authorizing the motherboards. The motherboard must first be tested when installed in a typical enclosure but with the enclosure's cover removed so that the internal circuitry is exposed at the top and on at least two sides of the enclosure. Other components, including a power supply, peripheral devices, and subassemblies are to be added, as needed, to complete the personal computer system. If the oscillator and the microprocessor circuits of the computer system are contained on separate circuit boards, both boards must be used in the test. Under this test procedure, radiated emissions from the system may be no more than 6 decibels (�dB�) above the limits specified in �15.109. These limits are shown in Table I below.
The testing is to be performed in accordance with the procedures specified in the measurement standards of �15.31. If the initial test shows that the open box computer system exceeds 6 dB above the limits shown in Table I, a further test is performed using the same configuration, but with the enclosure completely closed with all covers installed. Under these test conditions, the computer system under test shall not exceed the radiation limits specified in �15.109 of the rules. However, if the first test demonstrates that the computer system is in compliance with the radiation emission standards in �15.109, it is not required that the additional test be performed. The system must also be tested for compliance with the AC power line conducted limits as specified in �15.107, in accordance with the specified procedures in �15.31. If emissions greater than 6 dB above the limits can be identified and documented as originating from components other than the motherboard, then these emissions may be dismissed.
The test procedure of �15.32(a)(1) must be passed. Passing the first of the above tests, but failing the second, signifies a noncompliant product. If compliance cannot be demonstrated under the second test, then an alternative testing procedure is available in which the motherboard may be tested for compliance within the limits of �15.109 using a specified enclosure with the cover installed. Such testing must also be in accordance with the procedure specified in �15.31 and the motherboard that complies with the limits of �15.109 must be marketed together with the specific enclosure used for the test.
PRIOR ART Reference is now made to FIG. 1 which shows a system 50 for encapsulating or covering a conventional device 12 (e.g., a chip) on a device board (e.g., a component board, a circuit board, a printed circuit board or PCB, a CPU board, a motherboard, and the like) known in the art. The encapsulation is integrated into the device packaging materials. One exemplary type of board that the device board could be is the motherboard of a computer system. In FIG. 1 the device board includes a surface 10 on which the device 12 is mounted as is well known in the art. The device 12 may be an integrated circuit component (or silicon die). The device 12 could be an ASIC, for example, a clock source, in addition to other types of devices. The device 12 may be coupled to conductive leads or components (not shown) by bond wires 14 through contacts 16 and 18 on or in the surface 10 and the device 12, respectively. The contacts 18 may be conductive contacts, ohmic contacts, Schottky barrier contacts, and the like, depending on the specific implementation of the system 50.
A �primary� layer 20 typically covers or encapsulates the device 12, the bond wires 14, and the contacts 16 and 18. However, due to other factors, for example, air bubbles or other imperfections, or by design, the primary layer 20 may only cover a portion of the device 12, the bond wires 14, and the contacts 16 and 18. The primary layer 20 is nonconductive and is formed from an industry standard encapsulant that is typically chemically resistant and thermally stable. The primary layer 20 may be, for example, an epoxy cresol novolac polymer (provided by Plaskon Singapore [a division of Amoco Chemical], Shinetsu, Nitto Denko, or others), or other polymer. Such nonconductive polymers are typically used in packaging material for integrated circuits, and they may be composite polymer matrix materials having various components. The primary layer 20 serves to protect the device 12 from possible oxidation, and to help maintain the structural integrity of the device 12, the bond wires 14, and the contacts 16 and 18, as is known in the art. However, the primary layer 20 offers no magnetic shielding or electric shielding for the device 12 of emitted (or received) radiated energy, and will not aid a given system in achieving compliance with the FCC open box regulations.
SUMMARY OF THE INVENTION In one aspect of the invention, a system 50 encapsulating a device on a device board having a ground is provided. The system includes a first polymer layer that covers a portion of the device and a conductive material that covers a portion of the first polymer layer and is coupled to the ground. The system also includes a second polymer layer that covers a portion of the first polymer layer and the conductive material.
In another aspect of the invention, a method of encapsulating a device on a device board having a ground is provided. The method includes covering a portion of the device with a first polymer layer and covering a portion of the first polymer layer with a conductive material coupled to the ground. The method also includes covering a portion of the conductive material and the first polymer layer with a second polymer layer.
First Embodiment Reference is now made to FIG. 2, which shows a system 100 for encapsulating the device 12 on the surface 10 of a device board (i.e., the device 12 may be an on-board device) in accordance with a first embodiment of the invention. The system 100 is somewhat similar to the system 50 except for the provision of a secondary layer 22 that encapsulates or covers completely, or covers a portion of (e.g., a substantial portion of), the primary layer 20. Covering only a portion may be due to, for example, air bubbles, imperfections, or it may be done by design. However, for shielding purposes, complete or substantial covering, as understood by those skilled in the art in the context of the present invention, may be desirable to maximize shielding. (This discussion of covering applies to all embodiments of the present invention, and for any type of covering layer, not just those of the first embodiment.) The secondary layer 22 may be a composite material, for example, a composite made of an industry standard encapsulant, such as the epoxy cresol novolac polymer, which is impregnated with magnetically permeable material particles. A high percentage of the total volume or mass of the secondary layer 22 may be composed of these permeable particles, which may have a high magnetic permeability. Examples of high permeability material include ferrous materials, such as ferrite (a mixture of ferric oxide and oxides of other metals, such as manganese, nickel, zinc, and the like). A natural form of ferrite is hematite. Other high permeability material particles could be used.
In regions external to or outside the secondary layer 22 (or outside the device 12 or the device board), for example, at 3 meters distance, the strength of the magnetic field, whose flux lines may emanate from the device 12, will be reduced because of the presence of the high permeability particles in the secondary layer 22. A relatively large portion of the energy of these magnetic fields may be used to align the dipoles of the permeable particles in the secondary layer 22, and the magnetic flux lines will tend to be contained within the permeable material in the secondary layer 22. The tertiary layer 22 will also function to shield the device 12 from external magnetic fields derived from other sources for similar reasons. In making the composite material for the secondary layer 22, the proportion of permeable particles to polymer material, and the thickness of the resulting secondary layer 22 may be designed specifically to reduce magnetic field strength due to the device 12 in regions external to the secondary layer 22. It is understood that this proportion and this thickness, which are determinable in the art, would be at least sufficient to bring about a reasonable reduction in magnetic field strength external to the system 100 (e.g., to prevent harmful effects on other systems or people), and could be capable of complying with any anticipated future regulations that may be instituted regarding external magnetic field strength.
Second Embodiment Referring now to FIG. 3, a system 200 is shown in accordance with a second embodiment of the invention. The system 200 is somewhat similar to the system 100, but the system 200 does not include a secondary layer like 22. Instead, the system 200 includes a secondary layer 24 that is electrically conductive, and may be highly conductive. The secondary layer 24 is adjacent or layered on the primary layer 20 encapsulant, and may completely cover, or cover only a portion of, the layer 20. The secondary layer 24 also includes conductive shielding contacts or sections 26 coupled to the contact 16 which, in turn, are coupled to a device board ground (not shown in specific detail). The device contact 18 may also be coupled via the bond wire 14 to the device board ground. An encapsulant layer 28 is included that is adjacent or layered on (and covers all of, or a portion of, e.g., a substantial portion of) the secondary layer 24 and the primary layer 20, such that the secondary layer is disposed between the encapsulant layer 28 and the primary layer 20. The layer 28 differs from the secondary layer 22 in the system 100 in that it contains no permeable particles. The layer 28 may be nonconductive, and it may be made from the same polymer material as is used in the primary layer 20, or it could be different.
Third Embodiment Referring now to FIG. 4, a system 300 is shown in accordance with a third embodiment of the invention. The system 300 incorporates all the functionality of, and similar features to, both the systems 100 and 200 shown in FIGS. 1 and 2. The system 300 includes a primary layer 20′ (similar to the primary layer 20), a secondary layer 24′ (similar to the secondary layer 24), and a tertiary layer 22′ (similar to the secondary layer 22 in system 100). The secondary layer 24′ is adjacent or layered on (completely covering, or covering a portion of, e.g., a substantial portion of) the primary layer 20′, analogous to the layering of the secondary layer 24 on the primary layer 20 in the system 200. Moreover, the tertiary layer 22′ is adjacent or layered on (completely covering, or covering a portion of, e.g., a substantial portion of) the secondary layer 24′, such that the secondary layer is disposed between the tertiary layer 22′ and the primary layer 20′, analogous to the layering of the encapsulant layer 28 on the secondary layer 24 in the system 200. Such a configuration as the system 300 would be designed to be sufficient to reduce electrical energy radiating from the device 12 (e.g., at 3 meters distance) to bring the device board, onto which the system 300 is integrated, also into compliance with the open box regulations discussed above, as well as to reduce the magnetic field strength outside the system 300.
Method Embodiments In the present invention, for any foregoing discussion about covering layers with polymer layers and for any such discussion that follows, it is assumed that the polymer layers may be cured by any known technique, for example, with temperature, with chemicals, with ultraviolet light, etc. It may be possible that any polymer curing process that would be used in the present invention would also help with the adherence or attachment of the conductive foil layer in the systems 200 and 300, for example to the layers 20 and 28, or 20′ and 22′. Moreover, in the present invention, as discussed herein, covering a layer or layering on a layer includes the possibility that only a portion of the item being covered or layered on is actually covered (i.e., the covering may not be complete), due to, for example, imperfections, or by choice. Various methods of the present invention will now be discussed with reference to FIGS. 5-7.
Referring to FIG. 5, a flowchart representation is shown of a method of encapsulating a device (e.g., the device 12) on a device board (e.g., on the surface 10 in the system 100), in accordance with an embodiment of the invention. At block 102, a first portion of the device is covered with a polymer layer (e.g., the primary layer 20, which may be an epoxy), said device being completely covered, or in the alternative, only substantially covered, leaving no completely covered device. At block 104, a polymer material and a magnetically permeable material are combined (i.e., mixed together using known techniques in the art, for example, the mixing of ferrous particles and polymers is well known in the art of electrophotography) to form a composite polymer material. At block 106, the polymer layer is covered with a layer of the composite polymer material (e.g., the secondary layer 22 which may be a composite of epoxy and magnetically permeable particles).
Referring now to FIG. 6, a flowchart representation is shown of a method of encapsulating a device (e.g., the device 12) on a device board (e.g., on the surface 10 in the system 300) having a ground in accordance with another embodiment of the invention. At block 202, a portion of device is covered with a polymer layer (e.g., the primary layer 20)′, leaving a second portion uncovered. At block 204, the device is covered (e.g., also covering the first polymer layer) with a conductive foil material (e.g., the secondary layer 24′). The covering of the device may include attaching the conductive foil material to the first polymer layer and coupling the conductive foil material to the ground. At block 206, a polymer material (e.g., an epoxy) and a magnetically permeable material (e.g., ferrous particles) may be combined to form a composite polymer material, and at block 208, the conductive foil material and the polymer layer may be covered with a layer of the composite polymer material (e.g., the tertiary layer 22′).
Referring now to FIG. 7, a flowchart representation is shown of a method of encapsulating a device (e.g., the device 12) on a device board (e.g., on the surface 10 in the system 300) having a ground. At block 302, a first portion of the device is covered with a first polymer layer (e.g., the primary layer 20 which may be an epoxy), said device being completely covered, or in the alternative, only substantially covered, leaving no completely covered device. At block 304, the device is covered with a conductive foil material (e.g., the secondary layer 24). The covering of the device may include attaching the conductive foil material to the first polymer layer and coupling the conductive foil material to the ground. At block 306, the conductive foil material and the first polymer layer may be covered with a second polymer layer (e.g., the encapsulant layer 28 which may be an epoxy).
Patent CitationsCited PatentFiling datePublication dateApplicantTitleUS5561265Oct 4, 1994Oct 1, 1996Northern Telecom LimitedAssembly of a microelectronic device and a packageUS5639989 *Apr 19, 1994Jun 17, 1997Motorola Inc.Shielded electronic component assembly and method for making the sameUS5703761 *Aug 19, 1996Dec 30, 1997Siemens AktiengesellschaftShielding for flat modulesUS5814882 *Jul 6, 1995Sep 29, 1998Nec CorporationSeal structure for tape carrier package* Cited by examinerNon-Patent CitationsReference1Title 47-Telecommunications, Code of Federal Regulations; vol. 1, Parts 0 to 19; 47CFR 15.107 pp. 655-656, Oct. 1, 1998.2Title 47�Telecommunications, Code of Federal Regulations; vol. 1, Parts 0 to 19; 47CFR 15.107 pp. 655-656, Oct. 1, 1998.3Title 47-Telecommunications. Chapter 1 Federal Communications Commission, Part 15 Radio Frequency Devices. Sec. 15.31, Aug. 7, 1998.4Title 47�Telecommunications. Chapter 1 Federal Communications Commission, Part 15 Radio Frequency Devices. Sec. 15.31, Aug. 7, 1998.5Title 47-Telecommunications. Chapter 1 Federal Communications Commission, Part 15 Radio Frequency Devices. Sec. 15.32, Aug. 4, 1997.6Title 47�Telecommunications. Chapter 1 Federal Communications Commission, Part 15 Radio Frequency Devices. Sec. 15.32, Aug. 4, 1997.7Title 47-Telecommunications. Chapter 1 Federal Communications Commission, Part 15, Radio Frequency Devices. Sec. 15.109, Oct. 1, 1993.8Title 47�Telecommunications. Chapter 1 Federal Communications Commission, Part 15, Radio Frequency Devices. Sec. 15.109, Oct. 1, 1993.9U.S. application No. 08/998,615, Askew.Referenced byCiting PatentFiling datePublication dateApplicantTitleUS6479886 *Sep 15, 2000Nov 12, 2002Intel CorporationIntegrated circuit package with EMI shieldUS6498733 *Mar 1, 2001Dec 24, 2002Sony Computer Entertainment Inc.Electronic device and shieldUS6560125 *Dec 28, 2001May 6, 2003Motorola, Inc.Shield for shielding radio componentsUS6872880Jun 17, 2003Mar 29, 2005Delphi Technologies, Inc.Two-piece solderless EMC/EMI shieldUS6936763Jun 28, 2002Aug 30, 2005Freescale Semiconductor, Inc.dielectric region is on the substrate and the integrated circuit wherein the substrate and the dielectric region form an outer surface; substrate, dielectric region, and the magnetic material layer are integratedUS6989994 *Feb 26, 2004Jan 24, 2006Eagle Comtronics, Inc.Circuit board sub-assemblies, methods for manufacturing same, electronic signal filters including same, and methods, for manufacturing electronic signal filters including sameUS7358447Sep 10, 2003Apr 15, 2008Wavezero, Inc.Electromagnetic interference shields for electronic devicesUS7459769 *Feb 8, 2005Dec 2, 2008Sony CorporationMagnetic shield member, magnetic shield structure, and magnetic memory deviceUS8071431Dec 16, 2010Dec 6, 2011Skyworks Solutions, Inc.Overmolded semiconductor package with a wirebond cage for EMI shieldingUS8138584 *Sep 14, 2005Mar 20, 2012Freescale Semiconductor, Inc.Method of forming a semiconductor package and structure thereofUS8399972Aug 4, 2006Mar 19, 2013Skyworks Solutions, Inc.Overmolded semiconductor package with a wirebond cage for EMI shieldingUS8552725 *Dec 7, 2009Oct 8, 2013Northrop Grumman Guidance & Electronics Company, Inc.Systems and methods for obstructing magnetic flux while shielding a protected volumeUS20090184403 *Sep 14, 2005Jul 23, 2009Freescale Semiconductor. Inc.Method of forming a semiconductor package and structure thereofUS20110133738 *Dec 7, 2009Jun 9, 2011Abbink Henry CSystems and Methods for Obstructing Magnetic FluxUS20120211876 *Apr 23, 2011Aug 23, 2012Azurewave Technologies, Inc.Module ic package structureEP1733427A1 *Feb 11, 2005Dec 20, 2006Skyworks Solutions, Inc.Overmolded semiconductor package with an integrated emi and rfi shieldWO2004004435A1 *Jun 18, 2003Jan 8, 2004Motorola IncMagnetic shielding for electronic circuits which include magnetic materialsWO2005093833A1Feb 11, 2005Oct 6, 2005Skyworks Solutions IncOvermolded semiconductor package with an integrated emi and rfi shield* Cited by examinerClassifications U.S. Classification174/521, 257/659, 361/753, 361/816, 257/660, 257/E23.114, 361/799, 361/800, 361/818, 174/391, 257/E23.126International ClassificationH01L23/552, H01L23/60, H01L23/31Cooperative ClassificationH01L2924/01029, H01L2224/48091, H01L2924/01025, H01L2924/00014, H01L23/3135, H01L2924/3025, H01L2924/1433, H01L2224/85399, H01L2224/48464, H01L2224/4911, H01L2224/05599, H01L23/60, H01L2924/1617, H01L2924/14, H01L2924/01079, H01L2924/0103, H01L2924/16152, H01L24/49, H01L23/552, H01L2924/19107, H01L2924/01014, H01L24/48, H01L2924/01013, H01L2924/01028, H01L2924/10253European ClassificationH01L24/49, H01L24/48, H01L23/552, H01L23/31H4, H01L23/60Legal EventsDateCodeEventDescriptionMar 14, 2013FPAYFee paymentYear of fee payment: 12Aug 19, 2009FPAYFee paymentYear of fee payment: 8Aug 22, 2005FPAYFee paymentYear of fee payment: 4Nov 19, 2002CCCertificate of correctionDec 29, 1997ASAssignmentOwner name: INTEL CORPORATION, CALIFORNIAFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:ASKEW, RAY;REEL/FRAME:008919/0517Effective date: 19971229RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services©2012 Google