JPH088408B2 - Electronic circuit device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to the parts on a circuit board.
Involved in electronic circuit devices that are solder-sealed with caps, especially
Low melting point solder is interposed between the circuit board and each of the caps,
High melting point that was previously rolled and heat treated between these low melting point solders
With the processed solder inserted, melt the low melting point solder itself.
The components on the circuit board are solder-sealed by fusion
And an electronic circuit device.

[0002]

2. Description of the Related Art Conventionally, in electronic circuit devices, surface mounting by soldering has been known for the purpose of mechanical and chemical protection of semiconductors and components, mass productivity and improvement of reliability. Among them, as the highest density mounting method for semiconductors,
As shown in FIG. 4, a method is known in which the semiconductor chip 1 and the peripheral surface of the circuit board 2 are connected to each other with fine solder 3 via electrodes 4 and 5 (for example, Japanese Patent Laid-Open No. 43-28735).
See Japanese Patent Publication No. 3871014 and U.S. Pat. No. 3,871,014.
And ).

[0003]

However, according to the conventional method, when the semiconductor chip 1 and the circuit board 2 are connected, the solder 3 is completely melted and the wetting / diffusion reaction between the electrodes 4 and 5 is utilized. Then, the semiconductor chip 1 and the substrate 2 were connected. Therefore, as a connecting portion between the semiconductor chip 1 and the substrate 2,
During the cooling process, all the solder 3 is segregated in alloy composition, gaps and residual stress are generated, and the cast structure becomes small in elongation. The casting condition is small elongation against the external force, for generating a non-uniform deformation, fatigue characteristics is poor, a relatively short time against <br/> various stresses in use, the solder 3
There was a problem of destroying.

[0004] The present invention is to solve the conventional problems described above, soft
Another object of the present invention is to provide an electronic circuit device which has excellent ductility and fatigue characteristics and enables highly reliable solder sealing.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a component on a circuit board having a metallization.
The solder is capped so that the
The first low melting point solder provided on the
The second low melting point solder provided and the second low melting point solder
If so, it is previously inserted between the first low melting point solder and
It consists of rolled and heat-treated high melting point processed solder.
Circuit board by melting the first and second low melting point solders themselves
The above mounted components are sealed with solder .

[0006]

The present invention is based on the following phenomena and principles, and in addition to the low melting point solder, is preliminarily rolled and heated.
Processed high melting point processed solder (hereinafter referred to as processed solder
Capped parts on the circuit board using processed solder material
In one in which the solder seal. That is, most of the metals, when melted and solidified, have many gas absorptions and defects, and most alloys other than pure metals have a heterogeneous cast structure with composition segregation and weight segregation during the solidification process. Metals and alloys consisting of such defects and inhomogeneous structures are generally brittle, so when they are used for structural members, etc., they are rolled or heat-treated to break the cast structure and make it homogeneous.
As a result, a method of improving toughness and ductility is performed. However, Pb-Sn and Au-Sn as brazing materials
Since alloys such as the above have a basic principle of fusion connection, when they are melted and solidified, they always have a cast structure, and it is almost impossible to process this to destroy the structure.

In FIG. 5, working solders a ', b', and c'are given by taking a Pb-Sn alloy with stress (kg / mm2) on the vertical axis and elongation ε (%) on the horizontal axis as an example. Casting material a,
It shows how different the tensile properties of b and c are.

As shown in the figure, the processed solder a ',
In both compositions, b'and c'are soft and markedly improved in elongation. This processed solder a ', b',
In c ', a tensile test piece is prepared from a sheet cold-rolled at a rolling rate of 90% and then heat-treated at room temperature for about 1 week. Next, FIG. 6 is 95Pb / 5Sn solder cast material (the FIG. 6 (a), the equivalent to c in FIG. 5), the processing of solder (Fig. 6
(B), corresponding to the structure of c'in FIG. 5). As shown in the figure, the structure of the processed solder is such that the crystal grains are finely segregated, the high-concentration Sn is spheroidized, and the internal strain is small as compared with the cast material. This elongation is 3 to 4 times that of the cast material, and the effect of property improvement by working and heat treatment can be understood.

From the above phenomena, the present inventors have made it clear that by using the above-mentioned processed solder as a connecting material, a connecting portion which can sufficiently withstand fatigue due to various stresses can be obtained. . In other words, the processing reaction
A low melting point solder than I, by only connecting end portions of the machining solder melting connection, can be connected without losing excellent toughness and ductility of the processed solder can reliable connection, and like this This is because most brazing filler metals have potential as materials that can be expected to be effective. FIG. The phase diagram of the Pb-Sn alloy announced by Hansen in 1958.
FIG. 9 is a state diagram of the —In alloy, and FIG. 9 is a state diagram of the Pb—Sb alloy. As is clear from these figures, segregation and inhomogeneous structures are formed in the cooling and solidification process, and if these are processed and heat-treated, improvement in elongation properties can be expected.

[0010]

1 to 3 showing an embodiment of the present invention.
Will be described. FIG. 1 is described with reference to FIGS. 1 and 2 showing a case where the present invention is applied to sealing in an electronic circuit device. As shown in FIG. 2 , in order to seal the components such as the semiconductor chip 1 and the capacitor connected to the circuit board 2 by the connecting solder 24, the semiconductor chip 1 and the capacitor are arranged so as to cover the upper parts of the components. Between the cap 25 and the peripheral end of the circuit board 2
The processed solder 26, which has been processed and formed through 5, is inserted, and a solder (not shown) having a melting point lower than that of the processed solder 26 is attached between each of the electrodes 4 and 5 and the processed solder 26. Only the melting point solder is melted and the cap 25 and the circuit board 2 are locally melted and connected. The inside sealed with the cap 25, the processed solder 26 and the circuit board 25 protects the components in a vacuum or an atmosphere of an inert gas. Further, the connecting solder 24 for connecting the semiconductor chip 1 and the components such as the capacitor to the circuit board 2 includes the cap 25 and the circuit board 2.
High melting point solder is used so as not to melt when sealing and.

[0011] Next the 3, in advance on the circuit board half
Assuming that parts such as conductor chips are connected,
A method of manufacturing an electronic circuit device in which components are sealed with a cap on a circuit board will be described. First, as shown in FIG. 3A, the electrodes 5 are formed on a substrate 2 made of various materials by a method suitable for each material. To form. For example, when the substrate 2 is made of alumina ceramic, a conductive paste such as Ag-Pb and W is printed and fired to form the electrode 5. When the conductor paste is W, Ni plating or the like is further performed to form the electrode 5. On the electrode 5 thus formed, a low melting point solder, for example, P
A eutectic solder such as b-Sn or An-Sn is printed by solder paste, supplied by reflow, solder balls, vacuum deposition, etc. Reflow and solder dip are used to form the solder 7 to form a circuit board. Cash in the same way
The low melting point solder 8 is also formed on the electrode 4 on the chip 25 . Next, as shown in FIG. 3B , assuming that the electrodes 4 and 5 have a shape such as a circle, a quadrangle, or a triangle ,
Forming a high-melting machining solder 26 in which the corresponding shape. That is, the processed solder 26 is, for example, 95 wt% P
b-5 wt% Sn and 80 wt% Au- 20 wt% Sn are molded and placed in conformity with the low melting point solder 7 on the circuit board 2. In this state, heating is performed to melt only the low melting point solder 7 and fix the processed solder 26 on the electrode 5. The processed solder 26 was obtained by melting and casting, rolling it into a plate shape, processing it to a rolling rate of 90% , and heat treating it at 50 ° C. for 2 days in an inert atmosphere. It was almost identical to the characteristics of c 'shown in FIG. Then, the low and the cap 25 as shown in FIG. 3 (c)
After the solder 8 having a melting point is placed so as to match the working solder 26 , it is heated at a temperature slightly higher than the melting point of the low melting point solder 8 and melted and connected to the upper portion of the working solder 26 , as shown in FIG. An electronic circuit device can be obtained as shown. In the above embodiment, the shape of the work solder 26 is a cylinder having a diameter of 0.15 mm and a length of 0.3 mm.
Further, the method of supplying the processed solder 26 to the circuit board 2 is as follows.
A stainless mask having holes corresponding to the pattern of the electrode 5 is used. Since the solder connection portion thus obtained has a high melting point and a large volume of the processed solder 26 ,
Processed solder 26 for connection processing with the low melting point solders 7 and 8
The region is very small, 20 to 30 μm, so that it is almost processed solder. This is a temperature cycle -55
When fatigue life is evaluated by + 150 ° C, 1 cycle / hr test, fatigue life is 95 Pb-compared with conventional cast solder.
It was 5 times for 5Sn solder and 2 times for 80Au-20Sn solder .

[0012]

As described above, according to the present invention, a semiconductor and a component can be sealed by using a softened solder having excellent ductility and fatigue characteristics.
Highly reliable electronic circuit devices can be obtained with a simple configuration and easy operation, and in the field of surface mounting, where higher reliability and higher density are required in the future, for example, high-performance electronic circuit devices such as computers. It can make a great contribution to functionalization.

[Brief description of drawings]

FIG. 1 is a perspective view of an electronic circuit device showing an embodiment of the present invention.

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

FIG. 3 is an explanatory sectional view showing a manufacturing process of the electronic circuit device .

FIG. 4 is a perspective view showing a conventional electronic circuit device.

FIG. 5 is a tensile characteristic diagram of a processed solder according to the present invention and a conventional solder.

FIG. 6 is a photograph replacing a drawing showing the structures of a processed solder according to the present invention and a conventional cast solder.

FIG. 7 is a phase diagram of a Pb—Sn alloy according to the present invention.

FIG. 8 is a phase diagram of a Pb-In alloy.

FIG. 9 is a phase diagram of a Pb-Sb alloy.

[Explanation of Codes] 2 ... Circuit board, 7, 8 ... Low melting point solder, 4, 5 ... Electrode
Pole, 25 ... Cap, 26 ... Processed solder with high melting point .

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsu Sakaguchi 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Inside the Hitachi, Ltd. Institute of Industrial Science (72) Inventor Murata 292 Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Hitachi, Ltd., Production Engineering Laboratory (72) Inventor, Kazuo Hirota, 292, Yoshida-cho, Totsuka-ku, Yokohama City, Kanagawa Prefecture, Ltd. Hitachi, Ltd., Production Engineering Laboratory (56) Reference JP-A-51-16260 (JP, A) )

Claims (1)

[Claims] 1. A electronic circuit device solder seal cap components on the circuit board having a metallized, the
The solder is the first low melting point solder provided on the cap side.
And a second low melting point solder provided on the circuit board side,
Between the second low melting point solder and the first low melting point solder
Pre-rolled and heat-treated high melting point processed solder
Consists of a, the first, mounting components on the circuit board by melting of the second low melting point solder itself is formed by solder seal
Electronic circuit device of configuration .