JPH0658923B2 - Mounting method of semiconductor chip - Google Patents

Description

The present invention relates to a flip-chip type semiconductor in which semiconductor chips having solder bumps are mounted on both sides of an insulating substrate such as ceramic and the bumps are connected to conductor portions on the substrate. Regarding a chip mounting method.

[Conventional technology]

A flip chip method in which a solder bump of a semiconductor chip is aligned with a conductor portion of which at least a surface on an insulating substrate is made of solder, and the solder is reflowed and fused is well known. FIG. 2 shows an example of such a mounting method,
Solder paste is printed on the ceramic substrate 1 to form the conductor portion 2, and the chip 3 is placed on the ceramic substrate 1 with the surface having the solder bumps 4 facing downward so that the bumps 4 are in contact with the conductor portion 2 and then heated. Place in furnace to reflow solder and fuse. In this case, even if the positions of the conductor portion 2 and the bump 4 are slightly deviated from each other, there is a self-aligning function in which the connection is performed by the surface tension of the solder.

When chips are mounted on both sides of the substrate for high-density mounting, conductors are formed on both sides of the insulating substrate by using solders having different melting points. That is, first, a conductor portion is formed on one surface of a substrate by using a high melting point solder paste, and then a chip is mounted, and a bump of the chip and the conductor portion are fused in a reflow furnace. Next, a conductor part is formed on the other surface of the board using a low melting point solder paste, and the chip is placed on that surface with the surface facing up, and the other surface is used in the reflow furnace whose temperature is lower than that of the first reflow furnace. The conductor portion on the side and the bump of the chip are fused.

[Problems to be solved by the invention]

 Such a double-sided mounting method has the following problems.

(1) Two kinds of solder paste and reflow oven are required.

(2) The process time is long.

(3) Other electronic parts having low heat resistance, such as capacitors and resistors, cannot be mounted on the surface of the substrate where the high melting point solder is used.

An object of the present invention is to solve the above problems and provide a semiconductor chip mounting method capable of mounting chips on both surfaces of a substrate at the same time in a single reflow process using only low melting point solder. is there.

[Means for solving problems]

In order to achieve the above-mentioned object, the method of the present invention comprises forming conductor portions on both surfaces of an insulating substrate, at least surface layers of which are made of solder of the same material, and the substrate is provided in a positioning recess of a chip supporting jig. Each chip mounted on the surface is housed one by one to support the center of the lower surface of the chip, the substrate is placed on the chip supporting jig, and the conductor portion on the one surface is close to or in contact with the bump of each chip in the supporting jig. Then, another chip is placed on the other surface of the substrate, the bumps of each chip are brought into close proximity to or in contact with the conductor portion on the other surface, and then the conductor portion and the bump are fused in a reflow furnace.

[Action]

The conductor part formed on both sides of the insulating substrate, at least the surface of which is made of solder of the same material, has the chip accommodated in the positioning recess of the jig on the lower surface and the solder bump of the chip placed on the upper surface. Since they are in contact with each other or close to each other, the bumps of the chip and the conductor portion can be fused on both surfaces by one heating by reflowing the solder, and it is not necessary to use high temperature solder and high temperature reflow furnace.

〔Example〕

FIG. 1 shows an embodiment of the present invention, and the same parts as those in FIG. 2 are designated by the same reference numerals. The chip supporting jig 5 has a concave portion 6, the semiconductor chip 3 housed therein is supported by a support 7 at the center of the concave bottom surface, and the solder bumps 4 on the upper surface are on the lower surface of the insulating substrate 1. It is provided at a position where it comes into contact with the conductor portion 2 formed by printing the solder paste. The chip 3 is placed on the upper surface of the substrate 1 and on the conductor portion 2 formed by printing the solder paste at the same time as the lower surface so that the bumps 4 come into contact with each other. By placing the substrate 1 and the chips 3 thus arranged together with the chip supporting jig 5 in a reflow furnace and heating,
The bumps 4 of each chip and the conductor portions 2 on both upper and lower surfaces are fused.
A step 8 is formed on the support jig 5 below the periphery of the substrate 1 to prevent the substrate 1 from being lowered too much and being crushed at the fused portion during reflow. Even if all the bumps 4 and the conductors 2 are not in contact with each other before the reflow, they are contacted by the deformation of the solder at the time of the reflow, and the bumps 4 and the conductors 2 are connected at a normal position with the self-alignment function. Done. Since each of the chips 3 on the lower surface side is supported by the support 7 only at one point in the central portion, the displacement of the chips when the self-alignment function works is not hindered. However, the width of the recess 6 is limited to about 100 μm larger than the size of the chip 3.

FIG. 3 shows another embodiment, which is different from the embodiment shown in FIG. 1 in that the chip 3 is supported by the pin 9 in the recess of the supporting jig 5. The support pin 9 has a structure in which each chip 3 is pushed upward by a spring 10 with a constant pressure. By doing so, there is an advantage that variations in the thickness of the chip 3 can be absorbed.

The conductor portion on the insulating substrate 1 is not limited to the solder only as in the above embodiment, but may be a conductor made of another material and preliminarily soldered.

〔The invention's effect〕

According to the present invention, by positioning the semiconductor chip mounted on the lower surface of the insulating substrate by the recess of the supporting jig,
Fusing the solder bumps of each chip with the conductors on both sides of the board in a single reflow process together with the chip placed on the upper surface,
The connection can be made. Therefore, since the melting point of the solder can be arbitrarily selected, it is not necessary to increase the reflow temperature, and it is possible to mount the semiconductor chip on both sides by the flip chip method without damaging other electronic components.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a jig set in one embodiment of the present invention, FIG. 2 is a perspective view showing flip-chip mounting, and FIG. 3 is a sectional view of another embodiment of the present invention. It is sectional drawing in the state set in the tool. 1: Insulating substrate, 2: Conductor part, 3: Semiconductor chip, 4: Solder bump, 5: Support jig, 6: Recess, 7: Support,
9: Pin.

Claims (1)

[Claims] 1. A method of mounting semiconductor chips having solder bumps on both sides of an insulating substrate and connecting the bumps to conductor portions on the substrate, the conductor comprising at least surface layers made of solder of the same material on both sides of the insulating substrate. Part is formed, and each of the chips mounted on one surface of the substrate is housed in the positioning recess of the chip supporting jig to support the center of the lower surface of the chip, and the substrate is placed on the chip supporting jig. Bring the conductor on one side of the substrate close to or in contact with the bump of each chip in the support jig, then place another chip on the other side of the substrate and place the bump of each chip near the conductor on the other side of the substrate. A method for mounting a semiconductor chip, characterized in that each conductor portion and each bump are fused together in a reflow furnace.