JPH053196A - Semiconductor integrated circuit element and mounting thereof on wiring board - Google Patents

Abstract

PURPOSE:To enable semiconductor integrated circuit elements different in weight or the like to be well mounted on the same wiring board. CONSTITUTION:Solder bumps 2, which are formed on the electrodes of semiconductor integrated circuit elements 1a, 1b, and 1c that are mounted on a common wiring board 3 by soldering and different from each other in number of electrodes solder, are formed of material of the same composition. The wiring board 3 is so constituted as to make a load imposed on each electrode of the semiconductor elements 1a, 1b, and 1c equal or nearly equal, and these semiconductor integrated circuit elements 1a, 1b, and 1c are mounted on the common wiring board 3 coated with solder 5 lower than the solder bump 2 in melting point by soldering through a reflow method. By this setup, a short circuit is prevented from occurring between electrodes or wirings even if they are arranged fine in pitch, so that semiconductor circuit elements can be well mounted by soldering.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mounting method capable of reliably soldering a plurality of semiconductor integrated circuit elements (hereinafter referred to as "IC") to the same wiring board.

[0002]

2. Description of the Related Art A conventional mounting method of this type will be described with reference to FIGS. In FIG. 4, the solder bumps 2 are formed on each of a plurality of electrodes on the surface of the IC 1 (in this case, represented by a flip chip) and the electric circuit wiring 4 formed on the surface of the wiring board 3. The respective solders 5 are welded by reflow to mount the IC 1 on the wiring board 3. However, the heights of the solder bumps 2 are not uniform, and are different,
When the solder 5 on the wiring board 3 is more uneven, the solder bumps 2 are often not connected to the wiring board 3 when both are soldered in such a state. . Therefore, as shown in FIG.
Place the weight 6 on the entire back surface (upper surface) of C1 and reflow,
It is soldered to prevent such a bad connection.

However, in such a mounting method, an excessive load is applied depending on the type of IC, and the solder bump 2
And the connection portion 7 formed by melting the solder 5 by reflow
In the case where the solder squeezes out and the electrode pitch of the IC is a fine pitch of about 150 μm or less, the wiring between the electrodes or adjacent wiring is short-circuited, and a mounting defect occurs. In addition, the weight 6 is placed on the back surface of the IC 1 each time the IC 1 is mounted on the wiring board 3 as described above.
Mounting work is complicated and inefficient.

[0004]

Therefore, the present invention is
It is an object of the present invention to mount the ICs without using the weight as described above, but surely so that various ICs arranged on the wiring board do not short-circuit between adjacent electrodes or adjacent wirings.

[0005]

Therefore, according to the present invention, the solder formed on the electrodes of a plurality of semiconductor integrated circuit devices having different numbers of electrodes, which are mounted by soldering on a common wiring board, has the same composition, and The load per electrode of the semiconductor integrated circuit element was configured to be equal or almost equal. When these semiconductor integrated circuit elements are mounted by soldering on the common wiring board, the plurality of the plurality of wiring patterns are attached to the common wiring board to which a solder having a melting point lower than that of the solder formed on the electrodes is previously applied. The above-mentioned problems were solved by mounting the semiconductor integrated circuit element by soldering.

[0006]

Therefore, according to the IC of the present invention and the method of mounting these ICs on the wiring board, both ICs having electrodes formed at a fine pitch and ICs having different sizes and weights are mixed. Even if the ICs are mounted on the same wiring board by reflow, there is no occurrence of a short circuit between adjacent electrodes of the IC or between adjacent wirings.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method of mounting an IC of the present invention on a wiring board will be described below with reference to FIGS. Figure 1 shows multiple ICs
Is a partial plan view showing a common wiring board mounted with,
2 is a cross-sectional view taken along the line AA of FIG. 1, and FIG. 3 is a cross-sectional view showing a state where the IC and the electric circuit wiring are connected as a result of the reflow in the state of FIG. The same parts as those in FIGS. 4 to 6 are designated by the same reference numerals.

For example, a common wiring board 3 made of glass epoxy resin shows only a part of these figures, and a plurality of electric circuit wirings 4 are formed on the surface thereof at a pitch of, for example, 150 μm. Has been formed. Solder 5 is attached to these electric circuit wirings 4. On such a wiring board 3, a plurality of ICs 1a, 1b, 1c having different sizes, weights, numbers of electrodes, electrode pitches, etc. are mounted with high density together with other electric components constituting other electric circuits. FIG. 1 shows a state in which only three ICs are mounted.

In the figure, these ICs 1a, 1b, 1c are represented by flip-chip type semiconductor devices. IC1a is 10
6 electrodes for IC1b and IC1c for IC1b
Has 16 electrodes, and the solder bumps 2 are formed on the respective electrodes. Also, the solder 5 on the electrical circuit wiring 4
As the solder of the solder bump 2, a solder having a composition of lead and tin as described below was used.

Flux is applied to the electric circuit wirings 4 and / or the solder bumps 2 of the common wiring board 3 as described above, and the ICs 1a, 1b, 1c are mounted so that the solder bumps 2 are accurately mounted on the electric circuit wirings 4. Equipped with, through a heating furnace,
For example, heating (reflow) is performed at about 216 ° C. Then, the solder 5 is completely melted, and the solder of the solder bump 2 is welded in a semi-molten state.

In this mounting method, the most important requirement for preventing the inconvenient short circuit pointed out in FIG. 6 is the load per electrode. The present inventors confirmed the connection state between the electric circuit wiring 4 and the solder bump 2 with an IC having a 80 mm electrode as a 6 mm square silicon chip as the IC 1 a. In this case, for the solder 5 on the electric circuit wiring 4, for example, a solder having a composition of a ratio of lead and tin of 6: 4 is used, and for the solder of the solder bump 2, for example, lead and tin are used. The solder having the composition of the ratio of 1: 9 is used, for example, about 21
When heated at 6 ° C, solder 5
It was also confirmed that the solder bumps 2 were welded in a good state and did not short-circuit between the electrodes and between the electric circuit wirings. Then, when the load per electrode of this IC 1a was measured, it was about 0.
It was 48 mg.

As the IC 1b, an IC having 40 electrodes on a 3 mm square silicon chip is referred to as the IC 1a.
When the same solder composition was used and the same temperature was applied and the welding state of both was confirmed, it was found that some electrodes were not connected. Therefore, this IC1
When the load per electrode of b was measured, it was about 0.26 m
It was g. Therefore, the inventors plated copper on the back surface of this IC, increased the load per electrode to 0.5 mg, which is almost equal to that of IC1a, and conducted an experiment again under the same conditions as described above. As shown in FIG. 3, it was confirmed that the solder 5 and the solder bump 2 were welded in a good state.

Further, as the IC 1c, an IC having 120 electrodes on a 9 mm square silicon chip is
When the composition of each solder was the same as that of C1a, heating was performed at the same temperature, and the welding state of both was confirmed, it was found that a part of the electrodes and the electric circuit wiring were short-circuited. Then, when the load per electrode of this IC1c was measured, it was about 0.65 mg. Therefore, the present inventors ground the back surface of this IC to reduce the load per electrode,
When the amount was reduced to 0.5 mg, which is almost the same as that of IC1a, and an experiment was conducted again under the same conditions as described above, it was confirmed that the solder 5 and the solder bump 2 were welded in a good state.

Therefore, even in the ICs 1a, 1b, 1c having different appearances such as size, weight, number of electrodes, etc., if the load per electrode is configured to be equal or substantially equal and have the same solder composition. It has been confirmed that even if these ICs are simultaneously mounted on the common wiring board 3, a good connection state can be obtained.

In the above experiment, the weight was increased by adhering copper to a 3 mm square silicon chip, and the 9 mm square silicon chip was polished to reduce the weight. However, since it is inefficient, if the type of IC to be mounted on a common wiring board is known, plating, vapor deposition, etc. of a heavy object on the back surface of the silicon wafer on which the integrated circuit that is the basis of each IC is formed. If the wafer is adhered by means or the back surface thereof is ground and the wafers are diced, the load per electrode of each chip can be set to a predetermined load.

Further, in the above-mentioned embodiment, the flip-chip type IC has been described as an example of the IC, but the present invention can also be applied to a surface mounting type IC such as the QFJ type.

[0017]

As is apparent from the above description, according to the IC of the present invention and the method of mounting those ICs on the wiring board, even if the ICs have electrodes formed at a fine pitch, the size, weight and Even if ICs with different sizes are mixed and mounted on the same wiring board by reflow, the I
An event that short-circuits the electrodes adjacent to each other or the wires adjacent to each other does not occur. Moreover, since the batch reflow can be performed at the same temperature, the work efficiency is improved. And again
Since all the ICs are reflowed under the optimum conditions, various excellent effects such as improvement in reliability and yield can be obtained.

[Brief description of drawings]

FIG. 1 is a partial plan view showing a common wiring board on which a plurality of ICs are mounted.

FIG. 2 is a cross-sectional view taken along the line AA of FIG.

FIG. 3 is a cross-sectional view showing a state where the semiconductor integrated circuit element and the electric circuit wiring are connected as a result of reflowing in the state of FIG.

FIG. 4 is a sectional view for explaining a state of a semiconductor integrated circuit element and a wiring board.

FIG. 5 is a cross-sectional view for explaining a method for mounting a semiconductor integrated circuit element of a conventional technique on a wiring board.

6 is a cross-sectional view showing a state in which a semiconductor integrated circuit element is mounted on a wiring board by the mounting method of FIG.

[Explanation of symbols]

1 Semiconductor integrated circuit element (IC) 2 Solder bump 3 wiring board 4 electrical circuit wiring 5 solder 6 weights 7 connection

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H05K 3/34 H 9154-4E

Claims (2)

[Claims] 1. A solder formed on electrodes of a plurality of semiconductor integrated circuit elements having different numbers of electrodes to be mounted by soldering on a common wiring substrate, and having the same composition, and one electrode of each semiconductor integrated circuit element A semiconductor integrated circuit device having a load which is equal or substantially equal. 2. When a plurality of semiconductor integrated circuit elements having different numbers of electrodes are mounted by soldering on a common wiring board, the load per electrode of each of these semiconductor integrated circuit elements is equal or substantially equal, Then, the composition of the solder formed on each electrode is configured to be the same, while the melting point of the solder previously deposited on the wiring board is set lower than the melting point of the solder formed on the electrode. A method for mounting a semiconductor integrated circuit device on a wiring board, comprising mounting the plurality of semiconductor integrated circuit devices by soldering.