JPS6120146B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor device having elements subjected to face-down bonding and a method suitable for manufacturing the same.

Generally, when a beam lead element, a flip chip element, etc. is mounted on a substrate, a so-called face-down bonding method is adopted in which the element is bonded from the top side down. If this method is adopted, a gap is created between the substrate and the chip, so that the heat generated in the chip cannot be efficiently dissipated through the substrate. Therefore,
Conventionally, heat generated by a chip is dissipated from the back surface of the chip.

For example, in the conventional example shown in FIG. 1, a semiconductor chip 2 is face-down bonded to a substrate 1, and a heat sink/cap 3 made of ceramic is bonded to the semiconductor chip via a low melting point solder 4 such as gold or silicon. It is fixed to the chip 2 and also to the substrate 1 via a suitable low melting point solder 5. Furthermore, as shown in FIG. 2, for example, the heat sink/cap 3 is made of metal instead of ceramic.

Incidentally, in all of the conventional examples described above, the semiconductor chip 2 and the heat sink/cap 3 are fixedly attached. This fixation is extremely strong if the semiconductor chip 2 is silicon, since it is eutectic with the gold-silicon solder 4.

Therefore, if the semiconductor chip 2 is found to be defective after mounting, replacing it will be an extremely difficult task since the heat sink/cap 3 must be removed. Normally, we would want to dispose of them as waste, but in recent years semiconductor chips have been made into LSIs, and even a single chip is quite expensive. In a device in which a plurality of semiconductor chips are mounted on one substrate, if one semiconductor chip is defective, it would be too much loss to discard all of them. Furthermore, high-speed LSIs consume large amounts of power and have complex functions, so electrical tests must be conducted in conditions similar to those actually mounted on a wiring board due to heat generation, etc. In this case, the problems described above may occur. is even more serious. It has been considered that the heat sink/cap 3 may be fixed with an adhesive, but the same applies in that case.

The present invention enables face-down bonded semiconductor chips to be easily removed and replaced at will, even though heat dissipation means are provided on the back surface of the semiconductor chips.
This will be described in detail below.

FIGS. 3 to 5 are process diagrams of one embodiment of the present invention, and the following will be described with reference to these figures.

Refer to FIG. 3 (1) The semiconductor element 12 is face-down bonded to the semiconductor element mounting substrate 11.

(2) Prepare a spacer 13, a heat sink 14 made of copper (Cu), and a screw 15, for example.

The spacer 13 serves to maintain an appropriate distance between the heat dissipation substrate 14 and the substrate 11.

A through hole 14A through which the semiconductor element 12 can be viewed and a through hole 14B into which a screw is inserted are formed in the heat dissipation substrate 14. Further, in the vicinity of the through hole 14A on the surface facing the semiconductor element 12, for example, solder plating 16 is applied. This solder plating 16 may be of any other material as long as it is easy to bond with solder, such as tin (Sn) plating, preliminary solder, or the like. Further, it may be applied to the entire heat dissipation board 14 instead of partially.

The screw 15 passes through the heat dissipation board 14 and the spacer 13 and its tip is screwed into the board 11.

See FIG. 4 (3) Fix the heat dissipation board 14 to the board 11 with screws 15. A slight gap g exists between the heat dissipation substrate 14 and the semiconductor element 12.

(4) Low-temperature solder such as indium/tin (In/Sn),
That is, the solder 17 is prepared. Solder 17 shown
Although it has a cylindrical shape, the shape is not limited to that shown in the drawings, as long as it can be inserted into the through hole 14A. Further, the material must have poor wettability with respect to the semiconductor element 12, and must also melt at a low temperature. Indium and tin have poor wettability to silicon, and the temperature is 117°C.
Melts at [℃].

(5) Insert the solder 17 into the through hole 14A.

See FIG. 5 (6) Place the whole in a heating furnace and heat to such an extent that the solder 17 melts. The solder 17 melts into the shape shown.

The solder 17 is fused to at least the portion of the heat dissipation board 14 on which the solder plating 16 is applied, but it is only in contact with the semiconductor element 12.

As can be seen from the above description, since the solder 17 is not fused to the semiconductor element 12, the heat dissipating substrate 14 can be easily separated from the substrate 11 by removing the screws 15, and therefore the semiconductor element 12
If there is a defective product, it is easy to replace it. After replacing the defective product, it is possible to repair it again through the same steps as above.

FIG. 6 is an explanatory diagram of another embodiment, and the same parts as in the embodiment described with reference to FIGS. 3 to 5 are indicated by the same symbols.

This embodiment differs from the previous embodiment in that cooling fins 18 are attached to the heat dissipation board 14. In this case, as long as the cooling capacity of the fins 18 is sufficient, the heat dissipation board 14 can serve as a fin holder, so even a material with low thermal conductivity may be used as the heat dissipation board. I can do it.

Cooling fin 1 marked with symbol a in Figure 6
8 explains the state in which it is attached to the heat dissipation board 14, the one with symbol b explains the state in which solder 17 is supplied, and the one with symbol c explains the state after heating. This example is basically the same as the previous example. Incidentally, in both this embodiment and the previous embodiment, the gap g is adjusted by appropriately selecting the height of the spacer 13.

Another embodiment according to the invention is shown in FIG. 7th
The figure shows the mounting structure in a state corresponding to FIG. The only difference is that a semiconductor element in which 19 is fixed with solder or adhesive 20 is used. In this case, the molybdenum (Mo) plate and the solder 17 are in contact with each other in such a way that they can be easily peeled off.

As can be seen from the above description, according to the present invention, for example, warping of a semiconductor element mounting board, warping of a heat dissipation board, non-uniform thickness or unevenness of a semiconductor chip, and gaps between a heat dissipation board or fins and a semiconductor element can be prevented. Even if there is non-uniformity in the air gaps, the back surface of the semiconductor element and the heat dissipation substrate or fins are all tightly bonded by the solder, so the heat dissipation effect is good. Since the solder and the semiconductor element are only in contact with each other, the board and the heat dissipation board can be easily separated, so for example, if a defective chip is discovered after completing a multi-chip device. , it is easy to replace it, so the economic loss is reduced.

[Brief explanation of the drawing]

1 and 2 are explanatory diagrams of a conventional example, FIGS. 3 to 5 are explanatory diagrams of one embodiment of the present invention, FIG. 6 is an explanatory diagram of another embodiment, and FIG. 7 is an explanatory diagram of another embodiment. It is an explanatory diagram of an example. In the figure, 11 is a substrate, 12 is a semiconductor element,
13 is a spacer, 14 is a heat dissipation board, 15 is a screw,
16 is solder plating, 17 is solder, 18 is fin,
14A and 14B are through holes, and g is a void.

Claims (1)

[Scope of Claims] 1. A semiconductor element mounting board on which a plurality of semiconductor elements are mounted, a heat dissipation board that is removably attached to the semiconductor element mounting board by means of screws, and the heat dissipation board is It is attached to the semiconductor element mounting board through the through hole on the heat dissipation board side, and is melted and solidified to tightly fill the space between each of the semiconductor elements and the heat dissipation board, and also on the heat dissipation board side. and a solder fixed to the
A semiconductor device characterized in that the solder is not fused to the back surface of each of the semiconductor elements and forms a tight heat dissipation path from each semiconductor element to the heat dissipation substrate without any gaps. . 2. A semiconductor element mounting board on which a plurality of semiconductor elements are mounted, which is made up of a thin plate made of a material with good thermal conductivity fixed to the back of a semiconductor chip, and a semiconductor element mounting board that is removably attached by screws to face the semiconductor element mounting board. a thin plate that is attached to the semiconductor element mounting substrate through a through hole on the heat radiation substrate side, and is melted and solidified to be fixed to each of the semiconductor elements; and a solder that tightly fills the space between the heat dissipating substrate and the heat dissipating substrate, and the solder is not fused to the thin plate fixed to each of the semiconductor elements, and is not fused to the thin plate fixed to each of the semiconductor elements. 1. A semiconductor device, characterized in that a solid heat dissipation path is formed from a thin plate fixed to an element to the heat dissipation substrate without any gaps. 3. A plurality of semiconductor elements are mounted face down on a semiconductor element mounting board, and a heat dissipation board in which a through hole facing the back side of each semiconductor element is formed is removably fixed to the semiconductor element mounting board by screwing. Then, the method includes a step of supplying a non-fused solder to the back surface of each of the semiconductor elements through the through hole, and melting and solidifying the solder to bring the solder into close contact with the semiconductor element and to fix it to the heat dissipation substrate. A method of manufacturing a semiconductor device, characterized in that: