Integrated circuit package with EMI shield

[0002] The present invention relates to integrated circuit packages, in particular, those containing die that generate substantial levels of electromagnetic emissions.

[0003] Computer systems can emit electromagnetic radiation at various frequencies. Those emissions may cause undesirable electromagnetic interference (“EMI”) with the circuitry of the computer system and other electronic equipment near the computer system. For that reason, the FCC has enacted certain Open Chassis EMI regulations that impose limits on the electromagnetic emissions that such systems generate. 47 CFR §15.109. These limits are specified in Table 1 below.

[0004] Currently, most of the EMI that computer motherboards cause results from emissions produced by the packaged integrated circuits (“ICs”) that are mounted, or coupled, to the motherboard. To block (or reduce) the emissions that those parts release, various types of Faraday cages (or other sealing/covering apparatus) may be placed over them. Such devices, however, add cost to the system, may occupy scarce motherboard space, and may impose challenging signal routing requirements. As a consequence, using such devices to reduce the EMI that these packaged ICs cause is not a particularly attractive solution.

[0005] Accordingly, there is a need for an improved mechanism for reducing IC generated EMI. There is a need for such a mechanism that can be integrated into standard component designs without requiring significant modification. The packaged IC of the present invention includes such a mechanism.

[0006] FIG. 1 illustrates a side view of a cross-section of an embodiment of the packaged integrated circuit of the present invention.

[0007] FIG. 2 illustrates an overhead view of a cross-section of an embodiment of the packaged integrated circuit of the present invention.

[0008] A packaged integrated circuit (“IC”) is described. That device includes a substrate upon which is mounted a semiconductor die. An EMI shield encapsulates the semiconductor die, and a package body encapsulates the EMI shield. In the following description, numerous details are set forth to provide a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the invention may be practiced in many ways other than those expressly described here. The invention is thus not limited by the specific details disclosed below.

[0009] FIG. 1 illustrates a packaged IC according to one embodiment of the present invention. IC 100 comprises elements found in conventional devices, such as package tub 101, pedestal 102, semiconductor die 103, bond wires 104 and 105, external pins 106 and 107, and package body 108. Those elements may be made from materials conventionally used to make packaged ICs, using conventional processes. (In this embodiment, package tub 101 and pedestal 102 comprise the IC substrate upon which die 103 is mounted.) In addition to such standard components, IC 100 includes EMI shield 110. EMI shield 110 encapsulates semiconductor die 103, and is itself encapsulated by package body 108.

[0010] By grounding EMI shield 110 to the motherboard, e.g., via connection to one of IC 100's ground pins, EMI shield 110 may form a grounded Faraday cage that is integrated within the IC package. To serve as an EMI barrier, EMI shield 110 should be formed from aluminum or another conductive material that can block electromagnetic radiation. In a preferred embodiment of the present invention, such a conductive shield, or cage, surrounds die 103 and is connected exclusively to one or more of the package's ground pins.

[0011] The packaged IC of the present invention enables EMI to be contained and suppressed at the package level. As a result, additional costly, cumbersome and motherboard space occupying covers or shields need not be placed over the IC to minimize EMI. In addition, incorporating an EMI shield into the IC package (and thereby suppressing EMI closer to its source) may enable signal integrity related problems to be reduced by decreasing emissions of electromagnetic energy that could otherwise affect nearby traces and circuitry. Although particularly applicable to ICs that cause substantial EMI, EMI shield 110 may be integrated into all kinds of packaged ICs to reduce their contribution to EMI.

[0012] FIG. 2 provides an overhead view of a cross-section of an embodiment of the packaged integrated circuit of the present invention. In this embodiment, EMI shield 210 includes first, second, third, and fourth side surfaces—211, 212, 213, and 214, respectively. EMI shield 210 also preferably includes substantially planar upper and lower surfaces (not shown). Side surfaces 211, 212, 213, and 214 are each preferably oriented substantially perpendicular to those upper and lower surfaces. As shown in FIG. 2, first side surface 211 and second side surface 212 are each substantially planar and are oriented substantially perpendicular to third and fourth side surfaces 213 and 214.

[0013] In this embodiment, third and fourth side surfaces 213 and 214 each have a substantially jigsaw like configuration, in which indented portions 215 alternate with extended portions 216. Indented portions 215 engage extended portions 216 at substantially 90° angles. Side surfaces 213 and 214 receive a plurality of external pins, e.g., pins 206 and 207. Indented portions 215 each receive an end 217 of an external pin 206. Extended portions of side surfaces 213 and 214 (for example, extended portion 216) penetrate between adjacent external pins, e.g., pins 206 and 207, a distance along the length of those pins.

[0014] As shown in FIG. 2, EMI shield 210 forms a grounded Faraday cage that surrounds semiconductor die 203 on all of die 203's surfaces. In this embodiment, EMI shield 210 is connected to ground pin 220. Although in this example shield 210 is connected to only a single ground pin, large/complex ICs may require shield 210 to be connected to a larger number of ground pins.

[0015] An improved packaged IC has been described. That IC includes an EMI shield that has been integrated into it for blocking electromagnetic emissions that the IC may generate. Integrating such an EMI shield inside an IC package may be particularly useful for ICs that produce substantial EMI. By forming an EMI shield inside an IC package, the resulting IC will generate less electromagnetic emissions without requiring placement of costly and cumbersome shielding/covering mechanisms over the device.

[0016] Additional components that may be included in the illustrated packaged IC have been omitted as they are not useful to describe aspects of the present invention. Although the foregoing description has specified a packaged IC that includes certain features, those skilled in the art will appreciate that many modifications and substitutions may be made. For example, although the embodiment described above relates to an IC package having bond pads formed on the die opposite the package's mounting surface, the present invention may be used in other types of IC packages, such as flip chip, chip-on-flex, etc. . . . Also, although described in the context of a packaged IC for a computer motherboard, the present invention may apply to ICs used in various other applications, e.g., cellular phones, information appliances, personal digital assistants, set top boxes, telecommunication equipment, power supplies, consumer electronics, etc. . . . In addition, the shape of the EMI shield that is incorporated into the packaged IC is not important as long as it serves its EMI reducing function. Accordingly, it is intended that all such modifications, alterations, substitutions and additions be considered to fall within the spirit and scope of the invention as defined by the appended claims.