JPH1126654A - Resin-sealed semiconductor device and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin-sealed semiconductor device which is easily relieved from defects caused by thermal stress by a new construction and its manufacturing method. SOLUTION: An IC chip 5 and a quad flat package(QFP) are mounted on a circuit board 2 by SMT and the IC chip 5 and the quad flat package(QFP) are entirely covered with potting material 11. Silicone gel 12 is used as the base material of the potting material and minute voids 13 are dispersed in the silicone gel 12. At the time of manufacture, after the IC chip 5 and the quad flat package(QFP) are mounted on the circuit board 2, uncured liquid silicone mixed with hollow ball fillers is cast and then cured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin-encapsulated semiconductor device and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, a surface mount component (SMD) arranged on a circuit board is covered with a potting resin to protect it from an external atmosphere or vibration. In this case, a surface mount component such as a flip chip (FC), a quad flat package (QFP), or a small outline type package (SOP), in which a gap is formed between the circuit board and the surface mount component, is used. Potting resin enters into the gap, and thermal stress (operating force when heat is applied) of the potting resin is applied to a connection portion (usually, a soldered portion) with the circuit board, resulting in shortening of life or destruction. There are cases. To cope with this, the stress of the potting resin itself has been reduced by changing the chemical composition of the potting resin (for example, by increasing the size of the network in the network structure).

[0003]

However, in the above method, the chemical composition needs to be changed, and the processing method needs to be changed in accordance with the change in the chemical composition, resulting in an increase in cost and a decrease in moisture resistance. There was a problem such as.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a resin-sealed semiconductor device and a method for manufacturing the same, which can easily solve the problem caused by thermal stress with a novel structure.

[0005]

According to a first aspect of the present invention, there is provided a resin-encapsulated semiconductor device, wherein minute bubbles are scattered in a potting material covering the entire surface-mounted component.

With this configuration, a potting material exists between the circuit board and the surface-mounted component. When a temperature is applied to the potting material, the potting material thermally expands and contracts. Attempts to apply stress to the electrical connection between the device and the surface mount component. However, at this time, the bubbles in the potting material serve as deformation allowances (crushing allowances) to achieve stress relaxation.

Further, the use of a general potting resin (for example, a general silicone gel) does not increase the cost. According to the second aspect of the present invention, in the first step, the surface-mounted component is arranged on the circuit board, and in the second step, the surface-mounted component is formed of a potting material obtained by mixing a hollow sphere filler in a resin. The whole is covered.

As a result, the resin-sealed semiconductor device according to the first aspect is manufactured. Here, as described in claim 3, in the second step, a solution obtained by mixing a hollow resin with a liquid resin before curing is disposed on the surface of the component, and thereafter, a curing process is performed. This is practically preferable.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a resin-sealed semiconductor device according to the present embodiment. Also,
FIG. 2 shows a longitudinal section of the resin-sealed semiconductor device. FIG.
FIG. 3 shows an enlarged portion A of FIG. The resin-sealed semiconductor device of this example is used for an ignition device in an internal combustion engine. That is, it is a device for generating a high voltage by the ignition coil and supplying it to the ignition plug.

In FIGS. 1 and 2, a hybrid integrated circuit board 2 is disposed inside a case 1, and a conductor pattern (for example, indicated by reference numerals 3a and 3b in the drawings) is provided on an upper surface of the circuit board 2.
Is formed, and a thick film resistor 4 is arranged between the conductor patterns 3a and 3b. On the upper surface of the circuit board 2, components such as a flip-chip type IC (hereinafter referred to as an IC chip) 5 and a quad flat package (QFP) 6 are mounted on the surface, and components such as a resistor 7 are mounted. An ignition control circuit is formed by the thick film resistor 4, the mounted components 5 to 7, and the like.

As shown in FIG. 3, the IC chip 5 is provided with a plurality of solder bumps 8 on the bottom surface. Each solder bump 8 of the IC chip 5 is mounted on the conductor pattern 9 on the upper surface of the circuit board 2 and soldered. By the solder bonding of the solder bumps 8, the IC chip 5 and the conductor pattern 9 are formed.
And are electrically connected. Here, a gap AG is formed between the upper surface of the circuit board 2 and the lower surface of the IC chip 5.

As shown in FIGS. 1 and 2, external connection terminals (lead pins) 10a and 10b are erected on the circuit board 2, and the external connection terminals 10a and 10b are also provided on the conductor pattern on the upper surface of the circuit board 2. Is electrically connected to An ignition coil and a battery are connected to the external connection terminals 10a and 10b.

Further, the inside of the case 1 is filled with a potting material 11.
As shown in FIG. 3, the gap AG between the upper surface of the circuit board 2 and the lower surface of the IC chip 5 is also filled. In FIG.
As the potting material 11, a silicone gel 12 is used as a base material, and a large number of fine bubbles (hollow spheres) 13 are scattered in the silicone gel 12. The diameter of the bubble 13 is
It is about 80 μm. The potting material 11 has a Poisson's ratio of about 0.4. That is, the Poisson's ratio of the silicone gel 12 alone is about 0.5, but the Poisson's ratio is about 0.4 due to the scattered fine bubbles 13. With this potting material 11, an electrical connection portion (soldering portion) between the conductor pattern on the circuit board 2 side and the mounted component is provided.
Is protected.

As described above, the IC chip 5 and the quad flat package (QFP) 6 as the surface mount components are entirely covered with the potting material 11 to withstand shock and vibration.
Protected from the outside air (protected from moisture and corrosion).

Although the volume of the potting material 11 changes when heat is applied, the scattered bubbles 13 become deformation allowances (crushing allowances) to absorb thermal stress. Therefore, when heat is applied, thermal stress is less likely to be applied to the solder joints of the IC chip 5.

That is, as shown in FIG. 4, when the bubbles 13 are not mixed, a large force F proportional to the amount of strain δ is applied to the IC chip 5 as shown by the characteristic line P1, , The bubble 13 becomes a crushing allowance,
As shown by the characteristic line P2, almost no force F is applied to the IC chip 5 up to the predetermined distortion amount δ1.

The same applies to the quad flat package (QFP) 6. That is, a gap is also formed between the upper surface of the circuit board 2 and the lower surface of the quad flat package (QFP) 6, and the gap is filled with the potting material 11 in which minute bubbles 13 are scattered. Attempts to apply stress to the electrical connection site
3 serves as a deformation allowance (crushing allowance) to achieve stress relaxation.

Next, a method for manufacturing the resin-encapsulated semiconductor device thus configured will be described. First, an IC chip 5 and a quad flat package (QF
P) 6 is mounted on the surface, and components such as the resistor 7 are mounted. At the same time, the external connection terminals 10a,
10b is mounted. Then, this circuit board 2 is attached to case 1
Place inside and secure. At this time, a gap AG is formed between the upper surface of the circuit board 2 and the lower surface of the IC chip 5, and a gap is formed between the upper surface of the circuit board 2 and the lower surface of the quad flat package (QFP) 6. .

On the other hand, as shown in FIG. 5, a potting material (11) is prepared as a liquid resin before curing. That is, first, a liquid silicone gel is prepared, and a hollow sphere filler (microcapsule) 20 shown in FIG. 6 is prepared. The hollow sphere filler 20 is a fine particle having a diameter D of about 80 μm. As the hollow sphere filler 20, for example, DU-80 manufactured by Nippon Philite Co., Ltd. is used. And
The liquid silicone gel is mixed with an appropriate amount of the hollow sphere filler 20 (mixing step shown in FIG. 5).

Subsequently, a solution in which the hollow sphere filler 20 is mixed into the liquid silicone gel is injected into the case 1 (injection step shown in FIG. 5). At this time, the gap AG under the IC chip 5 and the quad flat package (QF
The silicone gel solution before curing enters the gap below P) 6.

Further, the silicone gel solution before curing is cured by heating (a heat curing step shown in FIG. 5). as a result,
The hollow sphere filler 20 is solidified while being dispersed in the liquid silicone gel.

Thus, the resin-sealed semiconductor device shown in FIGS. 1 to 3 is manufactured. Thus, this embodiment is
It has the following features. (A) In the resin-sealed semiconductor device in which the surface-mounted components 5 and 6 are surface-mounted on the circuit board 2 and sealed with a potting material, minute bubbles 13 are scattered in the potting material 11.

Therefore, the potting material 11 exists between the upper surface of the circuit board 2 and the surface mount components 5 and 6, and when the potting material 11 is heated, the potting material 11 expands and contracts due to heat. Substrate 2 and surface mount components 5, 6
Attempts to apply stress to the electrical connection site with. However, at this time, the bubbles 13 in the potting material 11 serve as deformation allowances (crush allowances), so that stress is relaxed.

Further, since a general silicone gel is used, there is no increase in cost. That is, if the potting resin itself is reduced in stress by changing the chemical composition of the potting resin (for example, by increasing the size of the mesh in the network structure), the cost will be reduced due to the change in the chemical composition and the processing method accompanying the change in the composition. However, in this embodiment, it is not necessary to change the processing method using a general silicone gel.

Further, the chemical composition of the potting resin is not changed, and the surface mount components 5, 6 can be reliably protected from the outside air by utilizing the moisture-proof property of the silicone gel. (B) The surface-mounted components 5 and 6 are arranged on the circuit board 2 (first step), and the entire surface-mounted components 5 and 6 are covered with a potting material in which the hollow sphere filler 20 is mixed in the resin (second step). Through the two steps), the resin-encapsulated semiconductor device described in (a) above is manufactured. (C) In particular, in the second step, a solution in which the hollow sphere filler 20 is mixed in the liquid resin before curing is arranged on the surface of the surface mount components 5 and 6, and thereafter, a curing treatment is performed. It becomes more preferable.

In addition to the embodiment described above, the present invention may be implemented as follows. As shown in FIG. 7, the surface mount component (semiconductor mold package) 30 has leads 31 and 32 extending from side surfaces. Then, the leads 31 and 32 of the surface mount component 30 are mounted on the circuit board 2.
Are mounted on the conductors 33 and 34 on the upper surface of the circuit board 2 and joined by soldering. A gap AG is formed between the upper surface of the circuit board 2 and the lower surface of the surface mount component 30. A potting material (moisture proof film; HumiSeal) 35 is applied around the surface mounting component 30 including the gap AG. The potting material 35 is made of polyimide (or polyamide) 36 as a base material and fine bubbles 37 dispersed in the polyimide 36. That is, a hollow filler (microballoon) is mixed into the polyimide 36 before curing, applied to the surface mount component 30, and then cured. Even when a thermal cycle is applied by the potting material 35, the upper surface of the circuit board 2 and
The potting material 35 attempts to expand and contract in the gap AG with the lower surface of the cell, but the stress is absorbed by the bubbles 37,
When a stress is applied between the circuit board 2 and the surface mount component 30, the bubbles 37 in the potting material 35 become deformation allowances (crush allowances), so that stress is relaxed.

In addition, although heating was used for curing the sealing resin,
It may be performed by a method such as ultraviolet irradiation. In addition, bonding of the surface-mounted component to the substrate side may be performed by a conductive adhesive other than soldering, and the component-side electrode and the substrate-side conductor may be bonded.

[Brief description of the drawings]

FIG. 1 is a perspective view of a resin-sealed semiconductor device according to an embodiment.

FIG. 2 is a longitudinal sectional view of a resin-sealed semiconductor device.

FIG. 3 is an enlarged view of a portion A in FIG. 2;

FIG. 4 is a characteristic diagram showing a relationship between a strain amount and a force.

FIG. 5 is a process chart for explaining a manufacturing process of the resin-sealed semiconductor device.

FIG. 6 is a sectional view of a hollow sphere filler.

FIG. 7 is a cross-sectional view of another example of a resin-sealed semiconductor device.

[Explanation of symbols]

2 circuit board, 5 IC chip, 6 quad flat package, 11 potting material, 13 bubbles, 20
Hollow sphere filler, 30: surface mount component, 35: potting material, 37: air bubble.

Claims (3)

[Claims] 1. A resin-encapsulated semiconductor device comprising: a circuit board; a surface-mounted component disposed on the circuit board; and a potting material that covers the entire surface-mounted component. A resin-encapsulated semiconductor device characterized in that minute bubbles are scattered in the semiconductor device. 2. A first step of disposing a surface mount component on a circuit board, and a second step of covering the entire surface mount component with a potting material obtained by mixing a hollow sphere filler in a resin. A method for manufacturing a resin-encapsulated semiconductor device, comprising: 3. The method according to claim 2, wherein, in the second step, a solution in which a hollow sphere filler is mixed in a liquid resin before curing is disposed on the surface of the component, and thereafter, a curing treatment is performed. Of manufacturing a resin-sealed semiconductor device.