Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Chip mounted on chip
Reexamination Certificate
2000-01-27
2003-09-30
Clark, Jasmine J B (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Chip mounted on chip
C257S723000, C257S787000, C257S713000, C257S717000
Reexamination Certificate
active
06627997
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a semiconductor module in which bare or packaged semiconductor chips are mounted on a wiring board, a heat spread plate is disposed above the semiconductor chips, and resin is filled around the semiconductor chips so that they are sandwiched between the wiring board and the heat spread plate, as well as a mounting method for the semiconductor module. Particularly, the invention is concerned with a multi-chip module with a plurality of semiconductor chips mounted on a single wiring board, as well as a mounting method for the multi-chip module.
BACKGROUND OF THE INVENTION
Semiconductor modules are used as high-speed or highly integrated memories in electronic devices such as personal computers, servers, and large-sized computers. These electronic devices now show a tendency toward reduction of size and thickness and are becoming higher in speed and integration degree. With such a tendency, semiconductor modules are also now required to attain high-density mounting, narrow pitch/multi-pin connection, low noise, and low heat resistance.
Under such circumstances, attempts are being made to enhance the mounting density by mounting on a wiring board a plurality of bare chips or chips size (or chip-scale) packages (hereinafter referred to as CSP) each almost equal in size to a chip. Attempts are also being made to attain a low heat resistance by bonding a heat spread plate to the backs of chips after mounting of plural bare chips or CSPs onto a wiring board.
As an example, in U.S. Pat. No. 5,724,729 there is disclosed a multichip module having a structure wherein a plurality of semiconductor chips are mounted on a single wiring board, and a heat spread cap is bonded to the backs of the semiconductor chips with use of a thermally conductive adhesive.
In Japanese Patent Laid-open No. Sho 63-29563 there is disclosed a semiconductor device having a structure wherein a flip chip is face down-bonded to a mullite substrate through bump electrodes, a silicon carbide substrate superior in thermal conductivity is bonded onto the flip chip with use of solder, and an epoxy resin is filled between the mullite substrate and the silicon carbide substrate. There is also described therein a multi-chip module having a structure wherein a plurality of such semiconductor devices as just referred to above are mounted on a single substrate, a heat spread plate is disposed so as to cover the plural semiconductor devices from above, and the heat spread plate and the semiconductor devices are connected together using a comb teeth-like heat transfer part.
According to our study, however, the above conventional techniques involve the following problems.
First, in the multi-chip module described in U.S. Pat. No. 5,724,729, the stress exerted on a chip is not dispersed because there exists a gap between adjacent chips. Consequently, when a stress is applied to a certain chip, the bonded end face between the stressed chip and the heat spread cap is apt to be cracked. Moreover, since an underfill resin is not filled around the bump electrodes connecting the chips to the wiring board, the bump electrodes are apt to be oxidized, besides, heat generated in each chip is difficult to be transmitted to the wiring board.
In the multi-chip module disclosed in Japanese Patent Laid-open No. Sho 63-29563, plural semiconductor devices are fixed to the heat spread plate mechanically through the heat transfer part, so if there are variations in size of the semiconductor devices, the heat spread plate will tilt, making it difficult to fix the semiconductor devices to the heat spread plate. In the module disclosed in Japanese Patent Laid-open No. Sho 63-29563, since the heat transfer part is in the shape of comb teeth, it is difficult for the heat spread plate to tilt even if there are slight variations in size of the semiconductor devices, but the comb teeth shape makes the structure of the multi-chip module complicated. Although resin is molded sideways of each semiconductor device, there is a resin-to-resin gap, so that water is apt to get into the gap or moisture condensation is apt to occur, with a consequent tendency toward material deterioration of the resin and insulation degradation.
In a multi-chip module, it is well known, as described in Japanese Patent Laid-open No. Hei 7-86492, that an underfill resin is filled between the semiconductor chips and a wiring board. However, the provision of a heat spread plate is not described in Japanese Patent Laid-open No. Hei 7-86492, giving no hint for solving the foregoing problems.
It is an object of the present invention to provide a semiconductor module having a structure wherein a plurality of bare or packaged semiconductor chips are mounted on a single wiring board and are covered with a single heat spread plate, the semiconductor chips and the heat spread plate being bonded together so as to permit thermal conduction without using any other heat transfer part, with a stress exerted on each of the semiconductor chips being dispersed, as well as a mounting method for the semiconductor module.
It is another object of the present invention to provide a semiconductor module having a structure wherein a plurality of semiconductor chips are connected to a single wiring board with use of metal bumps, a single heat spread plate is disposed on the backs of the semiconductor chips, a gap between the semiconductor chips and the wiring board is filled with an underfill resin, and the semiconductor chips and the heat spread plate are bonded together without using any other heat transfer part, allowing a stress exerted on each chip to be dispersed, as well as a mounting method for the semiconductor module.
SUMMARY OF THE INVENTION
The present invention, in a first aspect thereof, resides in a semiconductor module having a structure wherein a plurality of bare or packaged semiconductor chips are mounted on a single wiring board and a single heat spread plate is disposed on the plural semiconductor chips, characterized in that resin is filled around the plural semiconductor chips thus sandwiched between the wiring board and the heat spread plate and that adjacent semiconductor chips are connected together through the resin.
As methods for mounting a bare or packaged semiconductor chip onto a wiring board there are a method wherein the semiconductor chip is mounted while a circuit-formed side of the chip faces down and is opposed to the wiring board, and a method wherein the circuit-formed side of the chip faces up and a circuit-free side of the chip is opposed to the wiring board. In a semiconductor module of a face-down bonding type wherein a semiconductor chip is connected to a wiring board while a circuit-formed side of the semiconductor chip faces down, pads formed on the circuit-formed side of the chip and pads formed on the wiring board are connected together through metal bumps. On the other hand, in a semiconductor module of a face-up bonding type wherein a semiconductor chip is mounted on a wiring board while a circuit-formed side of the chip faces up, a circuit-free side of the semiconductor chip is bonded to the wiring board using an adhesive, and pads formed on the circuit-formed side of the semiconductor.chip and pads formed on the wiring board are bonded together with metal wires. The term “pads” as used herein indicate input-output terminals, which are sometimes called electrodes, electrode terminals, or simply terminals.
The present invention, in a second aspect thereof, resides in a semiconductor module having a structure wherein a plurality of either bare semiconductor chips or packaged semiconductor chips are connected to a single wiring board electrically through metal bumps while circuit-formed sides of the chips face down, and a single heat spread plate is disposed above circuit-free sides of the chips, characterized in that a resin is filled between the wiring board and the semiconductor chips, also between the semiconductor chips and the heat spread plate, and further between adjacent semiconductor chips, so that the s
Akahoshi Haruo
Anjo Ichiro
Eguchi Shuji
Nagai Akira
Nishimura Asao
Antonelli Terry Stout & Kraus LLP
Clark Jasmine J B
Hitachi , Ltd.
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