US20020190389A1 - Reduction of electromagnetic interference in integrated circuit device packages - Google Patents
Reduction of electromagnetic interference in integrated circuit device packages Download PDFInfo
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- US20020190389A1 US20020190389A1 US10/040,256 US4025601A US2002190389A1 US 20020190389 A1 US20020190389 A1 US 20020190389A1 US 4025601 A US4025601 A US 4025601A US 2002190389 A1 US2002190389 A1 US 2002190389A1
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- integrated circuit
- ferrite
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/48—Arrangements for conducting electric current to or from the solid state body in operation, e.g. leads, terminal arrangements ; Selection of materials therefor
- H01L23/488—Arrangements for conducting electric current to or from the solid state body in operation, e.g. leads, terminal arrangements ; Selection of materials therefor consisting of soldered or bonded constructions
- H01L23/495—Lead-frames or other flat leads
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/48—Arrangements for conducting electric current to or from the solid state body in operation, e.g. leads, terminal arrangements ; Selection of materials therefor
- H01L23/50—Arrangements for conducting electric current to or from the solid state body in operation, e.g. leads, terminal arrangements ; Selection of materials therefor for integrated circuit devices, e.g. power bus, number of leads
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/552—Protection against radiation, e.g. light or electromagnetic waves
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/58—Structural electrical arrangements for semiconductor devices not otherwise provided for, e.g. in combination with batteries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L23/00—Details of semiconductor or other solid state devices
- H01L23/58—Structural electrical arrangements for semiconductor devices not otherwise provided for, e.g. in combination with batteries
- H01L23/585—Structural electrical arrangements for semiconductor devices not otherwise provided for, e.g. in combination with batteries comprising conductive layers or plates or strips or rods or rings
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
- H01L2924/0001—Technical content checked by a classifier
- H01L2924/0002—Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
- H01L2924/15—Details of package parts other than the semiconductor or other solid state devices to be connected
- H01L2924/151—Die mounting substrate
- H01L2924/1517—Multilayer substrate
- H01L2924/15172—Fan-out arrangement of the internal vias
- H01L2924/15173—Fan-out arrangement of the internal vias in a single layer of the multilayer substrate
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
- H01L2924/30—Technical effects
- H01L2924/301—Electrical effects
- H01L2924/3011—Impedance
Definitions
- the present invention relates generally to reduction of electromagnetic interference and specifically to reduction of electromagnetic interference generated within an integrated circuit device package.
- EMI electromagnetic interference
- a recurring observation in the analysis of EMI performance in products that use VLSI integrated circuits is that there is a significant amount of emission radiated directly from the integrated circuit package itself before the signal connections from the device are available on an external pin. This is particularly evident in devices that have a large number of pins, such as a common 208 pin Quad Flat Pack (QFP) device.
- QFP Quad Flat Pack
- a 208 pin QFP device is typically on the order of 1 inch square with the actual integrated circuit itself occupying only a small amount of the real estate of the QFP package.
- the integrated circuit (IC) is relatively small being on the order of 0.2 square inches to 0.3 square inches
- the described physical lead lengths in typical integrated circuit packaging designs generally cause two problems.
- the first problem is mid and high frequency signal degradation introduced by the inherent series inductance of the conductor leads which is particularly a problem for the power and ground feeds.
- the second problem is that the conductor leads may radiate EMI energy as an antenna thereby interfering with the signals an adjacent conductor leads in the package and with other signal paths and components in the electronic device in which the integrated circuit is utilized.
- the techniques known in the art for reducing electromagnetic interference are effective only external to the integrated circuit device package. Thus, there lies a need for a method and apparatus to reduce or eliminate electromagnetic radiation internal to the integrated circuit device package itself.
- the present invention provides reduction and elimination of electromagnetic radiation in an integrated circuit.
- the electromagnetic radiation is reduced or eliminated, and electrical signals internal to the integrated circuit package are conditioned internally within the integrated circuit package itself.
- FIG. 1 is a somewhat diagrammatic representation of the internal design of a typical integrated circuit package
- FIG. 2 is a schematic illustration of the electrical model of a typical integrated circuit device package
- FIG. 3 is a somewhat schematic illustration of the electrical model of an integrated circuit device package utilizing the present invention.
- FIG. 4 illustrates the resulting characteristic curve of the electrical signals conditioned by the present invention
- FIG. 5 is a schematic elevation view of an integrated circuit device package of the present invention illustrating the magnetic flux pattern occurring therein;
- FIG. 6 is a somewhat diagrammatic representation of the internal design of an integrated circuit device package utilizing the present invention.
- FIG. 7 is a schematic elevation view of an integrated circuit device package of a preferred embodiment of the present invention illustrating the magnetic flux pattern occurring therein;
- FIG. 8 is a somewhat diagrammatic representation of the internal design of an integrated circuit device package utilizing a preferred embodiment of the present invention.
- FIG. 9 is an electrical schematic diagram of the equivalent circuit model of a preferred embodiment of the present invention.
- FIG. 1 illustrates the model of a typical Quad Flat Pack (QFP) integrated circuit device.
- the Quad Flat Pack may comprise a 1.0 inch square integrated circuit device package 10 .
- the integrated circuit (IC) 12 itself may only comprise a 0.2 inch square or 0.3 inch square wafer of silicon containing the actual integrated circuitry of the integrated circuit package 10 .
- the device package 10 is formed by encapsulating the integrated circuit 12 in a plastic medium 14 which defines the physical dimensions of the device package 10 .
- the plastic medium 14 protects and supports the integrated circuit 12 and contains the lead conductors which electrically connect the IC 12 to the external input/output (I/O) pins 18 of the device package 10 .
- the lead frame conductors 16 connect to the IC 12 via bonding wires 20 which directly connect to strategic circuitry nodes on the IC 12 .
- FIG. 2 illustrates the electrical model of the typical integrated circuit package of FIG. 1.
- FIG. 2 illustrates how the conductor leads 16 from the I/O pins 18 to the integrated circuit 12 are not ideal transmission lines but in practice exhibit a per length series inductance. Longer lengths of the conductor leads 16 result in larger values of the inherent series inductance.
- Input leads 16 connect the I/O pins 18 to input buffers 22 on the integrated circuit 12
- output leads 16 connect the I/O pins 18 to output buffers on the integrated circuit 12 .
- the input and output conductor leads 16 exhibit input series inductance L IN and output series inductance L OUT .
- the inductance of the V CC and V GND leads would be zero henries.
- the effective inductance of the V CC and V GND rails is effectively reduced with multiple parallel branches since there are typically multiple V CC and V GND pins in a given integrated circuit device package 10 .
- Utilization of multiple signal paths to reduce the effective inductance of a data signal path 16 is not feasible; therefore the effective series inductances L IN and L OUT of the lead conductors 16 preferably exhibit a small amount of “lossy” inductance.
- the packaging function for the integrated circuit 12 is preferably completed by placing the lead frame 16 with bonded integrated circuit 12 into a injection molding cavity where molten plastic is injected to encapsulate the lead frame 16 and integrated circuit 12 to form the device package 10 .
- the plastic material 14 is preferably electrically passive and electrically non-conducting so that it will cause no degradation of the electrical signals to and from the integrated circuit 12 .
- a modeled plastic material 14 having desired electromagnetic properties to advantageously affect the signals to and from the integrated circuit 12 as the signals are routed through the lead frame 16 of the device is utilized.
- a small amount of ferrite powder is preferably blended with the plastic material 14 to achieve the slightly lossy magnetic characteristic of the encapsulating plastic medium 14 surrounding the lead frame conductors 16 .
- Ferrite is preferred because of its high resistivity and permeability.
- FIG. 3 illustrates the effects of the introduction of ferrite powder into the encapsulating plastic of the integrated circuit device package of FIG. 1.
- the introduction of a ferrite material into the encapsulating plastic 14 alters the permeance of the encapsulating medium 14 and thereby affects the electrical characteristics of the inherent series impedance of the lead conductors 16 .
- the ferrite material in the encapsulating medium 14 causes the series inductance of the lead conductors 16 A and 16 B to behave as a lossy inductor L F . Further, the ferrite material contributes to the mutual inductance M F and resulting coupling primarily associated with adjacent leads 16 A and 16 B.
- the ferrite material exhibits hysteresis loss, but because ferrite has high characteristic resistivity, it exhibits no eddy-current loss.
- Increasing the permeance of the physical medium 14 surrounding the inductance with the presence of a magnetic material such as ferrite produces an effect opposite to the effect resulting with magnetic core inductors; instead of concentrating the magnetic flux within the center of the inductor to thereby augment the effective inductance as with a magnetic core, the increased permeance of the surrounding medium 14 due to the magnetic material tends to distribute the flux throughout the medium away from the inductor thereby attenuating the effective inductance.
- FIG. 4 illustrates the resulting preferred characteristic signal shape of a given data signal when a ferrite material is introduced into the encapsulating medium.
- the lossy inductor L F as shown in FIG, 3 would serve to attenuate only the highest frequency signal components while introducing generally little true inductance effects of overshoot and ringing associated with the series inductance of the leads 16 when no ferrite is present.
- the Q of the inherent series inductance of the conductor leads 16 is thereby minimized rather than maximized.
- the intentionally introduced inductor loss reduces the undesired effects of the inherent series inductance such as overshoot and ringing.
- FIG. 5 illustrates a two conductor mutual coupling model of the present invention.
- Introduction of mutual coupling and signal crosstalk between two adjacent lead conductors 16 A and 16 B would be an undesirable effect that is preferably minimized.
- Current flowing into conductor 16 A introduces magnetic flux 32 through adjacent conductor 16 B thereby inducing a current therein.
- a relatively small amount of ferrite material is blended in the encapsulating plastic 14 resulting in a relative permeability of the surrounding material 14 that is not too high to cause significant mutual coupling but yet sufficient to desirably affect the series inductance of the lead conductors 16 .
- the relative permittivity of the encapsulating medium 14 ranges from 5 to 10.
- the actual amount of mutual inductance M F between two adjacent lead conductors 16 A and 16 B is small with respect to the self-inductance L F of each conductor 16 .
- the reduction of crosstalk on any particular conductor 16 may be further achieved by placing that particular lead conductor 16 adjacent to a V CC or V GND lead to avoid any coupling to another data signal path.
- FIG. 6 illustrates a preferred embodiment of the present invention in which mutual coupling between adjacent leads is eliminated.
- the virtual elimination of the mutual inductance may be achieved by molding the device package 10 in two steps.
- the first step preferably comprises constructing the lead frame 16 and then forming or molding individual ferrite “microbeads” 30 on each lead 16 .
- the microbeads 30 are preferably offset so they do not interfere with adjacent microbeads 30 .
- the microbead adjacent are electrically isolated from the adjacent conductors 16 .
- the microbeads 30 are made of pure ferrite material which may be constructed using known ceramic techniques and the microbeads 30 would be formed as an integral part of the lead frame 16 .
- the microbeads 30 are utilized in a manner analogous to the utilization of ferrite bead chokes in radio-frequency transmission lines and antennas. The bead surrounds the transmission line and effectively chokes undesired high frequency signals immediately external to the transmission line that are the source of electromagnetic interference without affecting data signals passing therethrough.
- the second step preferably comprises ordinary plastic encapsulation of the frame 16 and the integrated circuit 12 upon completion of the bonding and wiring of the IC 12 to the lead frame 16 .
- a ferrite microbead 30 on any given lead 16 is optional depending upon the type of signal transmitted thereon. For example, V CC and V GND signals perform better if there is no ferrite bead 30 on those leads.
- the standard lead frame 16 is constructed with a microbead 30 on each lead 16 . Microbeads 16 may be selectively removed by crushing away the undesired beads 30 which is facilitated by the inherent brittleness of ferrite.
- a simple press may be utilized having small crushing pins arranged above the corresponding microbeads to be crushed in which all undesired microbeads 30 may be removed in a single step.
- FIG. 7 illustrates a preferred embodiment of the present invention in which the magnetic flux is contained within the ferrite beads.
- the ferrite bead 30 surrounding conductor lead 16 A completely contains the magnetic flux 32 generated by the current flowing into conductor lead 16 A. Thus, no current is induced in conductor lead 16 B from the magnetic flux 32 created by the current flowing through conductor lead 16 A.
- only the microbeads 30 contain ferrite wherein the encapsulating medium 14 entirely comprises non-magnetic plastic.
- a small amount of ferrite may be blended in with the encapsulating plastic 14 in conjunction with the utilization of ferrite beads to further achieve the reduction of electromagnetic interference.
- FIG. 8 illustrates the preferred placement of the ferrite beads of the present invention relative to the integrated circuit wafer in the device package.
- the most effective physical location for the microbeads 30 is as near to the integrated circuit 12 as possible. With the required close spacing of the lead frame conductors 16 near the IC bonding pads 20 , the physical size of a microbead 30 may not be very large la:yc:er the effects of the reduced size are offset by the fact that the placement of the ferrite microbead 30 near the IC 12 is nearly ideal.
- FIG. 9 illustrates the resulting electrical circuit model of a given conductor path in an integrated circuit device package of the present invention.
- An output signal V OUT from the integrated circuit 12 feeds into an output buffer 24 which is externally connected through an IC bonding wire pad 20 .
- the bonding wire 20 exhibits a small series inductance L 8 which is small relative to the inductance L F of the ferrite microbead 30 .
- the u frame conductor 16 exhibits a characteristic lumped series inductance L OUT and shunt capacitance C OUT , the effects of which are negligible compared to the inductance L F of the microbead 30 , and extends through the encapsulating medium 14 .
- the effects of inductance L OUT and capacitance C OUT may be further reduced by the blending of ferrite with the encapsulation material 14 .
- the lead frame conductor 16 connects to an external pin 18 on the exterior of the device package 10 .
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Abstract
Description
- The present invention relates generally to reduction of electromagnetic interference and specifically to reduction of electromagnetic interference generated within an integrated circuit device package.
- Advents in the performance of microcomputer based electronics have resulted in dramatic increases in operating speeds of the logic switching circuits. Increased switching and operating speeds correspond to increased bandwidths of the electronic signals transmitted within the interior of an electronic device which become a significant source for electromagnetic radiation causing interference with the internal circuitry of the device itself and with other electronic devices operating within the vicinity of the device. The electromagnetic radiation emitted at these higher frequencies may cause undesirable electromagnetic coupling between data paths resulting in cross channel interference.
- The amount of internally generated electromagnetic radiation must be limited to the guidelines and regulations set by governmental agencies such as the FCC in the United States and CISPR in European countries. Sources of electromagnetic radiation originating externally to the device may also affect and interfere with the operation of the device. In general the problems resulting from unwanted electromagnetic radiation are classified as electromagnetic interference (EMI).
- A recurring observation in the analysis of EMI performance in products that use VLSI integrated circuits is that there is a significant amount of emission radiated directly from the integrated circuit package itself before the signal connections from the device are available on an external pin. This is particularly evident in devices that have a large number of pins, such as a common208 pin Quad Flat Pack (QFP) device. A 208 pin QFP device is typically on the order of 1 inch square with the actual integrated circuit itself occupying only a small amount of the real estate of the QFP package. Typically, the integrated circuit (IC) is relatively small being on the order of 0.2 square inches to 0.3 square inches As a result, there must be internal conductor leads from the IC silicon wafer to the external pins of the device. This is typically implemented with a lead frame of metal strips etched or stamped from a sheet of material to support the integrated circuit chip and to provide a signal path for the input and output (I/O) pins of the QFP device.
- In such a design there may be a significant conductor length from the IC itself through the bonding wires and the lead frame conductors to the external pins of the device. This is especially true for pins at or near the corner of the device, in which case the conductor lead length may be well over 0.5 inch.
- The described physical lead lengths in typical integrated circuit packaging designs generally cause two problems. The first problem is mid and high frequency signal degradation introduced by the inherent series inductance of the conductor leads which is particularly a problem for the power and ground feeds. The second problem is that the conductor leads may radiate EMI energy as an antenna thereby interfering with the signals an adjacent conductor leads in the package and with other signal paths and components in the electronic device in which the integrated circuit is utilized. The techniques known in the art for reducing electromagnetic interference are effective only external to the integrated circuit device package. Thus, there lies a need for a method and apparatus to reduce or eliminate electromagnetic radiation internal to the integrated circuit device package itself.
- The present invention provides reduction and elimination of electromagnetic radiation in an integrated circuit. The electromagnetic radiation is reduced or eliminated, and electrical signals internal to the integrated circuit package are conditioned internally within the integrated circuit package itself.
- The numerous objects and advantages of the present invention may be better understood by those skilled in the art by reference to the accompanying figures in which:
- FIG. 1 is a somewhat diagrammatic representation of the internal design of a typical integrated circuit package;
- FIG. 2 is a schematic illustration of the electrical model of a typical integrated circuit device package;
- FIG. 3 is a somewhat schematic illustration of the electrical model of an integrated circuit device package utilizing the present invention;
- FIG. 4 illustrates the resulting characteristic curve of the electrical signals conditioned by the present invention;
- FIG. 5 is a schematic elevation view of an integrated circuit device package of the present invention illustrating the magnetic flux pattern occurring therein;
- FIG. 6 is a somewhat diagrammatic representation of the internal design of an integrated circuit device package utilizing the present invention;
- FIG. 7 is a schematic elevation view of an integrated circuit device package of a preferred embodiment of the present invention illustrating the magnetic flux pattern occurring therein;
- FIG. 8 is a somewhat diagrammatic representation of the internal design of an integrated circuit device package utilizing a preferred embodiment of the present invention; and
- FIG. 9 is an electrical schematic diagram of the equivalent circuit model of a preferred embodiment of the present invention.
- FIG. 1 illustrates the model of a typical Quad Flat Pack (QFP) integrated circuit device. The Quad Flat Pack may comprise a 1.0 inch square integrated
circuit device package 10. The integrated circuit (IC) 12 itself may only comprise a 0.2 inch square or 0.3 inch square wafer of silicon containing the actual integrated circuitry of theintegrated circuit package 10. Thedevice package 10 is formed by encapsulating theintegrated circuit 12 in aplastic medium 14 which defines the physical dimensions of thedevice package 10. Theplastic medium 14 protects and supports theintegrated circuit 12 and contains the lead conductors which electrically connect theIC 12 to the external input/output (I/O)pins 18 of thedevice package 10. Thelead frame conductors 16 connect to the IC 12 viabonding wires 20 which directly connect to strategic circuitry nodes on theIC 12. - FIG. 2 illustrates the electrical model of the typical integrated circuit package of FIG. 1. FIG. 2 illustrates how the conductor leads16 from the I/
O pins 18 to the integratedcircuit 12 are not ideal transmission lines but in practice exhibit a per length series inductance. Longer lengths of the conductor leads 16 result in larger values of the inherent series inductance. Input leads 16 connect the I/O pins 18 toinput buffers 22 on theintegrated circuit 12, and output leads 16 connect the I/O pins 18 to output buffers on theintegrated circuit 12. In general the input and output conductor leads 16 exhibit input series inductance LIN and output series inductance LOUT. - Ideally, the inductance of the VCC and VGND leads would be zero henries. In a preferred embodiment of the present invention the effective inductance of the VCC and VGND rails is effectively reduced with multiple parallel branches since there are typically multiple VCC and VGND pins in a given integrated
circuit device package 10. Utilization of multiple signal paths to reduce the effective inductance of adata signal path 16 is not feasible; therefore the effective series inductances LIN and LOUT of thelead conductors 16 preferably exhibit a small amount of “lossy” inductance. By making the series inductance of the conductor leads 16 lossy, the detrimental EMI effects of the series inductances may be thereby reduced. - Given the construction of the
lead frame 16, the packaging function for the integratedcircuit 12 is preferably completed by placing thelead frame 16 with bonded integratedcircuit 12 into a injection molding cavity where molten plastic is injected to encapsulate thelead frame 16 and integratedcircuit 12 to form thedevice package 10. Theplastic material 14 is preferably electrically passive and electrically non-conducting so that it will cause no degradation of the electrical signals to and from the integratedcircuit 12. - In a preferred embodiment of the present invention a modeled
plastic material 14 having desired electromagnetic properties to advantageously affect the signals to and from the integratedcircuit 12 as the signals are routed through thelead frame 16 of the device is utilized. A small amount of ferrite powder is preferably blended with theplastic material 14 to achieve the slightly lossy magnetic characteristic of the encapsulatingplastic medium 14 surrounding thelead frame conductors 16. Ferrite is preferred because of its high resistivity and permeability. - FIG. 3 illustrates the effects of the introduction of ferrite powder into the encapsulating plastic of the integrated circuit device package of FIG. 1. The introduction of a ferrite material into the
encapsulating plastic 14 alters the permeance of theencapsulating medium 14 and thereby affects the electrical characteristics of the inherent series impedance of thelead conductors 16. The ferrite material in the encapsulatingmedium 14 causes the series inductance of thelead conductors adjacent leads physical medium 14 surrounding the inductance with the presence of a magnetic material such as ferrite produces an effect opposite to the effect resulting with magnetic core inductors; instead of concentrating the magnetic flux within the center of the inductor to thereby augment the effective inductance as with a magnetic core, the increased permeance of the surroundingmedium 14 due to the magnetic material tends to distribute the flux throughout the medium away from the inductor thereby attenuating the effective inductance. - FIG. 4 illustrates the resulting preferred characteristic signal shape of a given data signal when a ferrite material is introduced into the encapsulating medium. The lossy inductor LF as shown in FIG, 3 would serve to attenuate only the highest frequency signal components while introducing generally little true inductance effects of overshoot and ringing associated with the series inductance of the
leads 16 when no ferrite is present. The Q of the inherent series inductance of theconductor leads 16 is thereby minimized rather than maximized. Thus, the intentionally introduced inductor loss reduces the undesired effects of the inherent series inductance such as overshoot and ringing. - FIG. 5 illustrates a two conductor mutual coupling model of the present invention. Introduction of mutual coupling and signal crosstalk between two
adjacent lead conductors conductor 16A introducesmagnetic flux 32 throughadjacent conductor 16B thereby inducing a current therein. In a preferred embodiment of the present invention a relatively small amount of ferrite material is blended in the encapsulatingplastic 14 resulting in a relative permeability of the surroundingmaterial 14 that is not too high to cause significant mutual coupling but yet sufficient to desirably affect the series inductance of thelead conductors 16. In a preferred embodiment of the present invention, the relative permittivity of the encapsulatingmedium 14 ranges from 5 to 10. - Regarding the two conductor mutual coupling example as shown in FIG. 3, the actual amount of mutual inductance MF between two
adjacent lead conductors conductor 16. In a preferred embodiment of the present invention, the reduction of crosstalk on anyparticular conductor 16 may be further achieved by placing thatparticular lead conductor 16 adjacent to a VCC or VGND lead to avoid any coupling to another data signal path. - FIG. 6 illustrates a preferred embodiment of the present invention in which mutual coupling between adjacent leads is eliminated. The virtual elimination of the mutual inductance may be achieved by molding the
device package 10 in two steps. The first step preferably comprises constructing thelead frame 16 and then forming or molding individual ferrite “microbeads” 30 on each lead 16. Themicrobeads 30 are preferably offset so they do not interfere withadjacent microbeads 30. The microbead adjacent are electrically isolated from theadjacent conductors 16. - In a preferred embodiment of the present invention the
microbeads 30 are made of pure ferrite material which may be constructed using known ceramic techniques and themicrobeads 30 would be formed as an integral part of thelead frame 16. Themicrobeads 30 are utilized in a manner analogous to the utilization of ferrite bead chokes in radio-frequency transmission lines and antennas. The bead surrounds the transmission line and effectively chokes undesired high frequency signals immediately external to the transmission line that are the source of electromagnetic interference without affecting data signals passing therethrough. - The second step preferably comprises ordinary plastic encapsulation of the
frame 16 and theintegrated circuit 12 upon completion of the bonding and wiring of theIC 12 to thelead frame 16. In an alternative embodiment of the present invention the inclusion of aferrite microbead 30 on any givenlead 16 is optional depending upon the type of signal transmitted thereon. For example, VCC and VGND signals perform better if there is noferrite bead 30 on those leads. In a preferred embodiment, thestandard lead frame 16 is constructed with amicrobead 30 on each lead 16.Microbeads 16 may be selectively removed by crushing away theundesired beads 30 which is facilitated by the inherent brittleness of ferrite. Preferably, a simple press may be utilized having small crushing pins arranged above the corresponding microbeads to be crushed in which allundesired microbeads 30 may be removed in a single step. - FIG. 7 illustrates a preferred embodiment of the present invention in which the magnetic flux is contained within the ferrite beads. The
ferrite bead 30 surrounding conductor lead 16A completely contains themagnetic flux 32 generated by the current flowing intoconductor lead 16A. Thus, no current is induced inconductor lead 16B from themagnetic flux 32 created by the current flowing throughconductor lead 16A. In a preferred embodiment of the present invention, only themicrobeads 30 contain ferrite wherein the encapsulatingmedium 14 entirely comprises non-magnetic plastic. Alternatively, a small amount of ferrite may be blended in with the encapsulatingplastic 14 in conjunction with the utilization of ferrite beads to further achieve the reduction of electromagnetic interference. - FIG. 8 illustrates the preferred placement of the ferrite beads of the present invention relative to the integrated circuit wafer in the device package. The most effective physical location for the
microbeads 30 is as near to theintegrated circuit 12 as possible. With the required close spacing of thelead frame conductors 16 near theIC bonding pads 20, the physical size of amicrobead 30 may not be very large la:yc:er the effects of the reduced size are offset by the fact that the placement of theferrite microbead 30 near theIC 12 is nearly ideal. - FIG. 9 illustrates the resulting electrical circuit model of a given conductor path in an integrated circuit device package of the present invention. An output signal VOUT from the integrated
circuit 12 feeds into anoutput buffer 24 which is externally connected through an ICbonding wire pad 20. Thebonding wire 20 exhibits a small series inductance L8 which is small relative to the inductance LF of theferrite microbead 30. Theu frame conductor 16 exhibits a characteristic lumped series inductance LOUT and shunt capacitance COUT, the effects of which are negligible compared to the inductance LF of themicrobead 30, and extends through the encapsulatingmedium 14. The effects of inductance LOUT and capacitance COUT may be further reduced by the blending of ferrite with theencapsulation material 14. Thelead frame conductor 16 connects to anexternal pin 18 on the exterior of thedevice package 10. - In view of the above detailed description of a preferred embodiment and modifications thereof various other modifications will now become apparent to those skilled in the art. The contemplation of the invention below encompasses the disclosed embodiments and all reasonable modifications and variations without departing from the spirit and scope of the invention.
Claims (10)
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
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US10/040,256 US20020190389A1 (en) | 1995-11-15 | 2001-12-31 | Reduction of electromagnetic interference in integrated circuit device packages |
US10/684,072 US7125743B2 (en) | 1995-11-15 | 2003-10-13 | Method for reduction of electromagnetic interference in integrated circuit packages |
US11/551,712 US20070096273A1 (en) | 1995-11-15 | 2006-10-21 | Reduction of Electromagnetic Interference in Integrated Circuit Device Packages |
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
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US675595P | 1995-11-15 | 1995-11-15 | |
US6868598A | 1998-05-13 | 1998-05-13 | |
US10/040,256 US20020190389A1 (en) | 1995-11-15 | 2001-12-31 | Reduction of electromagnetic interference in integrated circuit device packages |
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PCT/US1996/017916 Division WO1997018586A1 (en) | 1995-11-15 | 1996-11-15 | Reduction of electromagnetic interference in integrated circuit device packages |
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US6868598A Division | 1995-11-15 | 1998-05-13 |
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US10/684,072 Expired - Fee Related US7125743B2 (en) | 1995-11-15 | 2003-10-13 | Method for reduction of electromagnetic interference in integrated circuit packages |
US11/551,712 Abandoned US20070096273A1 (en) | 1995-11-15 | 2006-10-21 | Reduction of Electromagnetic Interference in Integrated Circuit Device Packages |
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---|---|---|---|
US10/684,072 Expired - Fee Related US7125743B2 (en) | 1995-11-15 | 2003-10-13 | Method for reduction of electromagnetic interference in integrated circuit packages |
US11/551,712 Abandoned US20070096273A1 (en) | 1995-11-15 | 2006-10-21 | Reduction of Electromagnetic Interference in Integrated Circuit Device Packages |
Country Status (1)
Country | Link |
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US (3) | US20020190389A1 (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20080135977A1 (en) * | 2006-12-07 | 2008-06-12 | Infineon Technologies Ag | Semiconductor component including a semiconductor chip and a passive component |
US20160006428A1 (en) * | 2014-07-03 | 2016-01-07 | Transphorm Inc. | Switching circuits having ferrite beads |
US20160099220A1 (en) * | 2014-10-01 | 2016-04-07 | Analog Devices Global | High isolation wideband switch |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7353092B2 (en) * | 2004-12-17 | 2008-04-01 | Honeywell International, Inc. | Support bridge for flexible circuitry |
Family Cites Families (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5138431A (en) * | 1990-01-31 | 1992-08-11 | Vlsi Technology, Inc. | Lead and socket structures with reduced self-inductance |
US5871625A (en) * | 1994-08-25 | 1999-02-16 | University Of Iowa Research Foundation | Magnetic composites for improved electrolysis |
JP2806328B2 (en) * | 1995-10-31 | 1998-09-30 | 日本電気株式会社 | Resin-sealed semiconductor device and method of manufacturing the same |
US6563299B1 (en) * | 2000-08-30 | 2003-05-13 | Micron Technology, Inc. | Apparatus for measuring parasitic capacitance and inductance of I/O leads on an electrical component using a network analyzer |
JP3645197B2 (en) * | 2001-06-12 | 2005-05-11 | 日東電工株式会社 | Semiconductor device and epoxy resin composition for semiconductor encapsulation used therefor |
-
2001
- 2001-12-31 US US10/040,256 patent/US20020190389A1/en not_active Abandoned
-
2003
- 2003-10-13 US US10/684,072 patent/US7125743B2/en not_active Expired - Fee Related
-
2006
- 2006-10-21 US US11/551,712 patent/US20070096273A1/en not_active Abandoned
Cited By (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20080135977A1 (en) * | 2006-12-07 | 2008-06-12 | Infineon Technologies Ag | Semiconductor component including a semiconductor chip and a passive component |
US8471393B2 (en) | 2006-12-07 | 2013-06-25 | Infineon Technologies Ag | Semiconductor component including a semiconductor chip and a passive component |
US20160006428A1 (en) * | 2014-07-03 | 2016-01-07 | Transphorm Inc. | Switching circuits having ferrite beads |
US9543940B2 (en) * | 2014-07-03 | 2017-01-10 | Transphorm Inc. | Switching circuits having ferrite beads |
US20170085258A1 (en) * | 2014-07-03 | 2017-03-23 | Transphorm Inc. | Switching circuits having ferrite beads |
US9660640B2 (en) * | 2014-07-03 | 2017-05-23 | Transphorm Inc. | Switching circuits having ferrite beads |
US20170222640A1 (en) * | 2014-07-03 | 2017-08-03 | Transphorm Inc. | Switching circuits having ferrite beads |
JP2017524267A (en) * | 2014-07-03 | 2017-08-24 | トランスフォーム インコーポレーテッド | Switching circuit with ferrite beads |
US9991884B2 (en) * | 2014-07-03 | 2018-06-05 | Transphorm Inc. | Switching circuits having ferrite beads |
US20160099220A1 (en) * | 2014-10-01 | 2016-04-07 | Analog Devices Global | High isolation wideband switch |
US9893025B2 (en) * | 2014-10-01 | 2018-02-13 | Analog Devices Global | High isolation wideband switch |
Also Published As
Publication number | Publication date |
---|---|
US7125743B2 (en) | 2006-10-24 |
US20070096273A1 (en) | 2007-05-03 |
US20040075175A1 (en) | 2004-04-22 |
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