Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Flip chip
Reexamination Certificate
2002-05-16
2003-12-02
Williams, Alexander O. (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Flip chip
C257S734000, C257S737000, C257S738000, C257S668000, C257S712000, C257S698000, C257S700000, C257S701000, C257S707000, C257S713000, C257S758000, C257S786000, C438S127000, C438S107000, C438S118000, C438S612000, C361S708000, C361S719000, C361S720000, C361S704000
Reexamination Certificate
active
06657311
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to flip-chip ball grid arrays and, more particularly, to a heat dissipating flip-chip ball grid array.
BACKGROUND OF THE INVENTION
Flip chip assembly involves the direct electrical connection of face-down electronic components onto substrates or circuit boards by means of conductive bumps on the chip bond pads. By contrast, wire bonding uses face-up chips with a wire connection to each pad. There are three primary stages in making flip chip assemblies: bumping the die or wafer, attaching the bumped die to the board or substrate, and, in most cases, filling the remaining space under the die with an electrically non-conductive material. The bump serves several functions in the flip chip assembly. Electrically, the bump provides the conductive path from chip to substrate. The bump also provides a thermally conductive path to carry heat from the chip to the substrate. In addition, the bump, provides part of the mechanical mounting of the die to the substrate. Finally, the bump provides a space, preventing electrical contact between the chip and substrate. In the final stage of assembly, this space is usually filled with a non-conductive “underfill” adhesive joining the entire surface of the chip to the substrate. The underfill protects the bumps from moisture or other environmental hazards, provides additional mechanical strength to the assembly, and compensates for any thermal expansion difference between the chip and the substrate. Underfill mechanically “locks together” chip and substrate so that differences in thermal expansion do not break or damage the electrical connection of the bumps.
A Ball Grid Array (BGA) package is primarily composed of three basic parts: the bare chip, a BGA substrate, and an interconnection matrix. The flip-chip is connected to the BGA substrate face-down, while the interconnection matrix connects the bare chip to the BGA substrate using direct attach flip-chip style connections. The BGA substrate, which includes very small traces and vias, conveys signals to the underlying printed circuit board through the solder-bump attachment pads on its bottom surface. A metal cover or plastic encapsulation is then used to seal the package.
One of the problems facing flip-chip devices is the heat that is formed during use of the devices and as a result of power consumption. If the flip-chip device is heated above a certain threshold, the speed, performance, and lifetime of the device may be adversely affected. To aid in the removal of such heat, some packages incorporate a heat spreader which ensures safe operation of the device by efficiently diffusing the released heat and preventing over heating of the chip.
Utilizing a heat spreader, however, has various limitations. For example, an interface layer is added between the die and the heat spreader and a second interface is placed between the heat spreader and the heat sink. With the small package and die sizes involved, these interface layers are not very efficient, thus limiting the amount of heat that can be removed efficiently from the back of a package or chip. Other limitations include the limited area of dissipation and the cost associated with a heat spreader. As such, a larger area of dissipation at a lower cost would be very advantageous.
It is therefore desirable for the present invention to overcome the limitations described above that are involved in dissipating heat from flip-chip packages.
SUMMARY OF THE INVENTION
The present invention achieves technical advantages as a heat dissipating flip-chip Ball Grid Array (BGA) including additional structure that dissipates heat from the flip-chip to a supporting structure, such as a printed circuit board.
In one embodiment, a flip-chip ball grid array comprises a substrate, a die, a first set of solder balls adapted to couple the die with the substrate, a thermal compound adapted to couple to a backside of the die, a second set of solder balls adapted to couple with the substrate, and a printed circuit board comprising a heat dissipating metal, wherein the heat dissipating metal is adapted to couple with the thermal compound, and wherein the second set of solder balls is adapted to couple with the printed circuit board.
In another embodiment, a flip-chip ball grid array comprises a substrate, a die comprising a plated backside, a plurality of solder bumps adapted to couple the die to the substrate, a heat dissipating metal adapted to couple to the plated backside of the die, a plurality of solder balls adapted to couple to the substrate, and a multi-layer printed circuit board adapted to couple to the heat dissipating metal and to the plurality of solder balls.
In a further embodiment, a flip-chip ball grid array comprises a substrate, a die, a first set of solder balls adapted to couple the die to the substrate, a thermal compound adapted to couple to a backside of the die, a second set of solder balls adapted to couple to the substrate, and a multi-layer printed circuit board comprising: a heat dissipating metal, comprising thermal vias, adapted to couple to the thermal compound, and thermal vias adapted to couple to the second set of solder balls.
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Hortaleza Edgardo R.
Torres Orlando F.
Brady III Wade James
Skrehot Michael K.
Telecky , Jr. Frederick J.
Texas Instruments Incorporated
Williams Alexander O.
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