JPH0983128A - Junction structure of semiconductor module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrict thermal stress applied to electronic parts to the minimum by subjecting only one time electronic parts constituting a semiconductor module to high temperature of a predetermined one or higher by fabricating the semiconductor module using a high melting point solder while mounting the module using a low melting point solder. SOLUTION: A semiconductor module 20 where electronic parts are mounted on a sub-printed circuit board 21 with reflow soldering is reflow-soldered to a main printed circuit board 10. In such a structure, the reflow-soldering of electronic parts to the sub-printed circuit board 21 is achieved using a high melting point solder 25 which requires 200 deg.C as maximum temperature in a reflow furnace. The reflow-soldering of the electronic module 20 to the main printed circuit board 10 is achieved using a low melting point solder 33 which is capable of soldering at 200 deg.C or lower as maximum temperature in the reflow surface. Accordingly, high temperature of 200 deg.C or higher may be applied only one time upon fabrication of the semiconductor module 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a joint structure for mounting a semiconductor module on a printed board by soldering.

[0002]

2. Description of the Related Art A semiconductor module is constructed by mounting a bare IC chip or other chip parts on a sub-printed board by reflow soldering. This semiconductor module is mounted on a main printed board together with other electronic parts. In the conventional case, as shown in the process diagram of FIG.
The solder paste is printed on the main printed circuit board to mount the semiconductor module, the semiconductor parts such as QFP / SOP and the chip parts, and the solder paste is melted in the reflow furnace.

The solder paste used in the conventional soldering process for semiconductor modules and the like is similar to the solder paste used for reflow soldering bare IC chips and the like on a sub-printed board in the semiconductor module manufacturing process. , Eutectic solder with a melting point of 183 ° C (hereinafter referred to as high melting point solder) is used, and the maximum temperature in the reflow furnace is 220 ° C for reflow soldering.
It was necessary to carry out in a high temperature atmosphere of up to 240 ° C.

Therefore, various electronic components constituting the semiconductor module are heated at a high temperature of 200 ° C. or more at least twice during the production of the semiconductor module and during the soldering of the semiconductor module, and the thermal stress is applied to the semiconductor module. Occurred in the electronic components that make up the solder, and caused soldering defects and component defects.

In order to solve this problem, soldering of electronic parts other than the semiconductor module to the main printed circuit board is performed by reflow soldering using a high melting point solder, and for the semiconductor module, a pulse heating method, a laser method or hot air is used. It is possible to individually solder the main printed circuit board by using a high melting point solder depending on the method or the like, but such a method has a problem that the number of work steps required for soldering increases. Moreover, since the soldering to the main printed circuit board is performed using high melting point soldering, it is difficult to attach and detach the semiconductor module.
There is also a risk that adjacent non-defective electronic components will also be defective.

[0006]

As described above, in the above-mentioned semiconductor module joining structure, the semiconductor module is reflow-soldered to the main printed circuit board by using the same kind of solder as the high melting point solder used when manufacturing the semiconductor module. Therefore, the electronic components constituting the semiconductor module are heated at a high temperature of 200 ° C. or more at least twice, and there is a problem that soldering defects or component defects of the electronic components occur due to thermal stress. . In addition, since the semiconductor module is joined to the main printed circuit board by high melting point solder, it is difficult to attach and detach the semiconductor module when repairing the semiconductor module, and the adjacent good electronic parts are also defective due to high temperature heating. There was a risk of

The present invention has been made to solve the above-mentioned conventional drawbacks, and when the semiconductor module is reflow-soldered to the main printed circuit board, the thermal stress applied to the electronic components can be extremely reduced. It is intended to provide a structure.

[0008]

The invention according to claim 1 is
In a junction structure of a semiconductor module in which a semiconductor module in which electronic components are mounted on a sub-printed circuit board by reflow soldering is reflow-soldered on a main printed circuit board, reflow soldering of the electronic component to the sub-printed circuit board is performed in a reflow furnace. Maximum temperature is 2
Reflow soldering of the semiconductor module to the main printed circuit board is performed using a high melting point solder that needs to be set to 00 ° C. or higher, and a low melting point solder that can be soldered at a maximum temperature in the reflow furnace of 200 ° C. or lower is used. I am going. Here, since the heat resistance limit temperature of the electronic component against the thermal stress is about 200 ° C., according to the above configuration, the reflow soldering of the semiconductor module to the main printed circuit board can be performed at the maximum temperature of 200 ° C. or less. Since the high temperature of 200 ° C. or higher applied to the constituent electronic parts is required only once when the semiconductor module is manufactured, the thermal stress of the electronic parts is minimized. Even when it is confirmed that the semiconductor module itself is defective, the low melting point solder is used for soldering the semiconductor module and the main printed circuit board. It can be done without applying heat until it reaches a high temperature.

According to the invention of claim 2, the invention of claim 1
In, the reflow soldering of the semiconductor module to the main printed circuit board is performed in a nitrogen atmosphere.
When soldering at low temperature, the wettability is lower and soldering failure is more likely to occur than when soldering at high temperature, but by soldering in a nitrogen atmosphere and preventing metal oxidation, this The drawbacks can be eliminated.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIG.
It will be described in detail with reference to FIG. 1 to 4 are views showing a first embodiment, FIG. 1 is a side view of a main printed circuit board to which a semiconductor module is soldered, FIG. 2 is a perspective view of the semiconductor module, and FIG. FIG. 4 is a manufacturing process drawing, and FIG. 4 is a mounting process drawing of the electronic component on the main printed circuit board.

As shown in FIG. 1, the main printed circuit board 1
The semiconductor module 20, the semiconductor device (QFP / SOP) 31, and the chip component 32 are soldered to the pad 11 of 0 using the low melting point solder (melting point 150 ° C.) 33. As shown in FIG. 2, the semiconductor module 20 includes a sub-printed board 21, a bare IC chip 22 mounted on the board 21, and a chip component 23. The sub-printed circuit board 21 is in the form of LCC (leadless chip carrier), and the I / O pad 211 is formed on the peripheral side surface thereof.
The pads 211 of the sub printed board 21 are soldered to the pads 11 of the main printed board 10. Further, pads 212 of various shapes are provided on the component mounting surface of the sub-printed circuit board 21, and the bare IC chip 22 and the chip component 23 have high melting point solder (eutectic solder, melting point 183).
25 ° C.) to the pad 212. Bumps 221 made of high melting point solder are provided in a grid pattern on the back surface of the bare IC chip 22, and the bumps 221 are soldered to the pads 212. Further, the soldered portion of the bare IC chip 22 is sealed with resin 26.

The above-mentioned semiconductor module 20 is manufactured by referring to FIG.
As shown in FIG. 1, in the first step, the solder paste containing the high melting point solder 25 is printed on the pads 212 of the sub-printed board 21, and in the second step, the bare IC chip 22 and the chip component 23 are placed at predetermined positions on the sub-printed board 21. Mount and
Reflow soldering in a reflow furnace (not shown) in the third step (peak temperature in the furnace is 220 ° C to 240 ° C)
I do. Then, in the fourth step, cleaning is performed to remove the residual flux, and in the fifth step, the bare IC chip 22 is removed.
The resin 26 is sealed in the soldered portion of the semiconductor module 20 to complete the semiconductor module 20.

To mount the electronic components on the main printed circuit board 10, as shown in FIG. 4, a solder paste containing the low melting point solder 33 is printed on the pads 11 of the main printed circuit board 10 in the first step, and the second step is performed. In the process, the semiconductor module 20, QFP /
The SOP 31 and the chip component 32 are mounted, and in a third step, reflow soldering (peak temperature of the furnace is 200 ° C. or less) in a nitrogen atmosphere reflow furnace (not shown) is completed.

As described above, when the semiconductor module 20 is manufactured, the high melting point solder 25 is used, but when the semiconductor module 20 is mounted, the low melting point solder 33 is used. The applied high temperature of 200 ° C. or higher can be applied only once, so that the thermal stress of the electronic component can be minimized. Further, even when the semiconductor module 20 is removed from the main printed circuit board 10 and is newly attached due to a defect in the semiconductor module 20, the low melting point solder 33 is used, so that these operations can be performed easily and low. Since the detaching and attaching work can be performed at a temperature, the electronic components adjacent to the semiconductor module 20 are unlikely to be damaged by high heat.

5 and 6 are views showing a second embodiment, FIG. 5 is a side view of a main printed circuit board to which a semiconductor module is soldered, and FIG. 6 is a perspective view of the semiconductor module. In this example, the I / O pad is not formed on the peripheral side surface of the sub-printed board 21A of the semiconductor module 20A, but instead the solder ball 213 formed of high melting point solder is provided on the back surface of the board 21A. Has been. Further, in the semiconductor module 20A, the solder balls 213 of the sub-printed board 21A have the low melting point solder 33.
Is soldered to the main printed circuit board 10. Other configurations are similar to those of the first embodiment, and the semiconductor module 20A is manufactured according to the process flow chart shown in FIG. 3, and the electronic components such as the semiconductor module 20A are mounted on the main printed circuit board 10. The process is performed according to the process flow chart shown in FIG.

[0016]

As described above, in the joining structure of the semiconductor module according to the first aspect, since the high melting point solder is used for manufacturing the semiconductor module and the low melting point solder is used for mounting the semiconductor module, the semiconductor module is configured. The high temperature of 200 ° C. or higher applied to the electronic component can be set only once, and therefore the thermal stress applied to the electronic component can be minimized. In addition, since the low melting point solder is used, the semiconductor module can be easily removed and installed, and therefore, the semiconductor module can be easily replaced. The problem that parts are damaged by high heat is unlikely to occur.

Further, in the joint structure of the semiconductor module according to a second aspect, since the reflow soldering of the semiconductor module to the main printed circuit board is performed in a nitrogen atmosphere in the first aspect, it is possible to prevent metal oxidation, and therefore Good soldering with low melting point solder can be performed.

[Brief description of drawings]

FIG. 1 is a view showing a first embodiment of the present invention and is a side view of a main printed circuit board to which a semiconductor module is soldered.

FIG. 2 is a perspective view of a semiconductor module mounted on the main printed board of FIG.

3A to 3D are manufacturing process diagrams of the semiconductor module of FIG.

FIG. 4 is a process diagram of mounting electronic components on the main printed circuit board of FIG.

FIG. 5 is a view showing a second embodiment of the present invention, and is a side view of a main printed circuit board to which a semiconductor module is soldered.

6 is a perspective view of a semiconductor module mounted on the main printed circuit board of FIG.

FIG. 7 is a mounting process diagram of an electronic component on a conventional main printed circuit board.

[Explanation of symbols]

10 Main printed circuit board 20, 20A
Semiconductor module 21, 21A Sub-printed circuit board 25 High melting point solder 33 Low melting point solder

Claims (2)

[Claims] 1. A reflow soldering of the electronic component to the sub-printed circuit board in a semiconductor module joint structure for reflow-soldering a semiconductor module in which an electronic component is mounted on the sub-printed circuit board by reflow soldering. Is performed by using a high melting point solder that requires the maximum temperature in the reflow furnace to be 200 ° C. or higher, and the reflow soldering of the semiconductor module to the main printed circuit board is performed when the maximum temperature in the reflow furnace is 200 ° C. or lower. A semiconductor module joining structure characterized in that a low melting point solder that can be applied is used. 2. The joint structure of a semiconductor module according to claim 1, wherein the reflow soldering of the semiconductor module to the main printed circuit board is performed in a nitrogen atmosphere.