JP3047632B2 - Electronic circuit device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic circuit device,
Specifically, the present invention relates to a resin-sealed hybrid IC.

[0002]

2. Description of the Related Art Conventional resin package type hybrid I
C is SIP type and DI depending on the lead extraction structure
Although it is classified into P type, in the case of resin molding, the circuit board is inserted in the mold or case in advance, and the casting method,
The liquid or powdered thermosetting resin (for example, epoxy resin or silicone resin) is used for sealing by an immersion method, a transfer method, or the like.

FIG. 5 shows an example of an SIP type hybrid IC. The circuit board 2a is accommodated in the case 1a,
Circuit elements such as resistors R1 and R2 are formed on the circuit board 2a. 3a is a mold resin part,
Filled in a, the circuit element is moisture-proof and the circuit board is fixed. 9a is a protective glass for protecting the resistors R1 and R2.

In another example of the SIP type hybrid IC, after a thin silicon gel film is applied to the entire surface of the circuit board 2a, the circuit board 2a is housed in a case 1a, and then filled with a mold resin portion 3a. I have.

[0005]

However, in the above-mentioned conventional resin-packaged hybrid IC, the sealing resin portion 3a is mainly used in the process of shrinking when the sealing resin is hardened and the subsequent resin shrinkage due to heating and cooling. Due to the difference between the contraction rate and the coefficient of thermal expansion between the circuit board 2a and the circuit board 2a, stress is generated between the two, and this stress acts on the resistors R1 and R2 fixed to the circuit board 2a. R1, R2
Has the drawback that the resistance value of the changes according to the stress received.

According to tests and analysis by the present inventors, compressive stress and bending stress in the direction perpendicular to the surface act on the circuit board 2a due to shrinkage of the sealing resin portion 3a during curing, and the bending stress causes the resistor It was found that a compressive stress or a tensile stress was generated in R1 and R2. Since the bending stress varies in each part of the circuit board 2a, the resistance values of the resistors R1 and R2 vary depending on the fixed position on the circuit board 2a, and as a result, the output of the circuit varies.

Hereinafter, test results will be described with reference to FIGS. As shown in FIG. 6, the test circuit board 20
The vertical, horizontal, and thickness dimensions were 13 mm × 47.5 mm × 0.8 mm, and the pedestal 90 supported both ends of the circuit board 20 in the longitudinal direction. The thick film resistor R is connected to the short side 21 of the circuit board 20.
, And the center of the circuit board 20 in the longitudinal direction was pressed at right angles to the longitudinal direction of the circuit board 20. Stress applied to circuit board 20 and circuit board 20
7 shows the relationship with the change in the resistance value of the thick film resistor R fixed to FIG.
Shown in From FIG. 7, it can be seen that the pressing force (bending stress) and the change in the resistance value are substantially linear, and the circuit board 2
It has been found that a curvature of 0 causes a decrease in resistance when a compressive stress occurs in the thick-film resistor R, and an increase in resistance when a tensile stress occurs in the thick-film resistor R.

Next, the relationship between the amount of warpage (displacement) and the amount of change in resistance in the circuit board 20 of FIG. 6 was examined. FIG. 8 shows the result. However, the amount of warpage was the maximum displacement at the center of the circuit board. From FIG. 8, it can be seen that the displacement amount (warpage amount) of the circuit board 20 and the resistance value change amount have a substantially linear relationship. When the central portion is pressed while supporting both short sides 21 and 22 of the circuit board 20, the compressive or tensile stress acting on each portion in the longitudinal direction of the circuit board 20 due to the deformation of the circuit board 20 is as shown in FIG. , The central part is at most both short sides 21,
It turned out that it changes to almost 0 at 22.

Next, the circuit board 20 in which the thick film resistor R is fixed at the above position is actually accommodated in the case 1 at the position shown in FIG. A change in the resistance value of the resistor R was examined. As a result, the average value of the rate of change in resistance value of the thick film resistor R1 was about -0.7%. In the conventional hybrid IC, the circuit board 2a
It has also been found that the circuit element mounting surface A of (1) warps so as to be concave. This is because circuit elements having various heights are fixed to the circuit element mounting surface A of the circuit board 2a, and accordingly, the circuit element mounting surface A and the case 1a facing the circuit element mounting surface A are adjusted accordingly.
It is necessary to ensure a dimension between the inner surface 11a and the mold resin portion 3a filled on the circuit element mounting surface A side is much larger than the mold resin portion 3a filled on the B surface side. It is thought to be. That is, the shrinkage amount (shrinkage force) of the thickly filled mold resin portion 3a on the side A is the shrinkage amount (shrinkage force) of the mold resin portion 3a on the side B side.
Since it is larger, it is considered that the circuit board 2a is warped so that the surface A is concave.

As a result of the above, such a circuit board 2
(Ie, bending stress in the direction perpendicular to the surface of the circuit board 2), compressive stress is applied to the thick film resistor R fixed on the circuit element mounting surface A, and the resistance value of the thick film resistor R decreases. . Further, as described above, by applying a soft silicon gel film on the surface of the circuit board 2a in advance, stress acting between the mold resin portion 3a and the circuit board 2a can be reduced. Since the film thickness was small, stress relaxation was slight, and the warpage of the circuit board 2a could not be eliminated. Of course, silicone gel coating,
Although the stress relaxation effect can be improved by repeating the drying many times, it is troublesome, and even if a thick silicon gel film is formed by multiple coatings, the molding resin portion 3
As a is filled, a stress acts on the circuit board 2a through the silicon gel film due to the curing shrinkage.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides an electronic circuit device capable of eliminating a resistance value variation of a resistor caused by a stress generated between a mold resin portion and a circuit board. That is its purpose.

[0012]

According to the first aspect of the present invention,
Have a substrate insertion groove for a circuit board held in the inner surface of one end opening
A case for being accommodated in the a resistor formed integrally casing, a circuit board end Ru held by the substrate insertion groove, one end of which is fixed to the circuit board, the other end before
A lead protruding from the opening of the case to the outside;
The lead without contacting the substrate at the opening of the source.
Holds the door and shields the opening of the case
A lid made of hard resin and filled in the case,
A uniform, gel-like soft resin that covers the entire surface of the circuit board
Electronic circuit device, characterized in that it comprises a part. Claim 2
The described invention is further improved in the electronic circuit device according to claim 1.
The contact portion between the lid and the case is bent.
It is characterized by having a structure. Claim 3
The invention further provides an electronic circuit device according to claim 1 or 2.
Preferably, the flexible resin portion is made of silicon gel.
Features.

As the resistor in the present invention, in addition to a thick film resistor formed by printing and firing, a thin film resistor formed by various PVD methods or CVD methods can be employed. These resistors are formed directly on the circuit board.

[0014]

According to the present invention, with the circuit board inserted into the case, the flexible resin portion is filled in the case and covers the entire surface of the circuit board. Then, the lid made of hard resin seals the opening of the case. The board fitting groove provided on the inner surface of the case holds the end of the circuit board.

In this case, unlike the conventional case, the thermosetting shrinkable sealing resin portion is not filled in the case, but only the flexible resin portion is filled to protect the circuit board. No stress is applied to the Further, since the lid covers the bottom opening of the case, the lead can be fixed while protecting the flexible resin portion and the circuit board. As a result, it is possible to realize an electronic circuit device in which the resistance value fluctuation of the resistor due to the stress is eliminated.

[0016]

(Embodiment 1) One embodiment of an electronic circuit device of the present invention is shown in FIGS. This electronic circuit device is a hybrid IC, and includes a case 1 having an opening 10 and a case 1.
A circuit board 2 accommodated in a case 1 and a silicon gel portion (flexible resin portion in the present invention) 3 filled in the case 1
A lid 6 for shielding the opening 10 of the case 1; and a lead 4 having one end fixed to the circuit board 2 and the other end penetrating through the silicon gel portion 3 and protruding to the outside.
In FIG. 1, the silicon gel portion 3 on the main surface of the circuit board 2 is shown.
Is peeled off and shown.

Case 1 has a length, width and height of 18 mm × 5.
It has a rectangular hollow body shape of 0 mm x 6 mm, and the bottom surface is open. Case 1 has a wall thickness of about 1 mm and is formed by injection molding of PBT resin. A pair of guide projections 11 (see FIG. 3) are provided on both inner end faces located at both longitudinal ends of the case 1 so as to project in parallel with each other. Guide protrusion 1
1 is 2.4mm x 7.1mm x 0.8m in height, width and height
m, a board fitting groove 12 into which an end of the circuit board 2 is fitted is formed between the pair of guide protrusions 11.

The circuit board 2 is a single-layer or multilayer board made of alumina.
2 are fitted and held between the pair of guide projections 11, respectively. The dimensions of the circuit board 2 are 13 mm in length, width and thickness
× 47.5 mm × 0.8 mm, and its linear expansion coefficient is about 75 × 10 ⁻⁶ / ° C. A single-layer or multi-layer wiring pattern (not shown) is formed on the circuit board 2. Resistors R1 and R2 are fixed on the circuit element mounting surface A of the circuit board 2 in the vicinity of the short side 21 of the circuit board 2, and the resistors R1 and R2 are fixed.
A protective glass 9 is attached on top.

The resistors R1 and R2 have a length, width and thickness of 1.
It is composed of a rectangular film of 5 mm × 0.85 mm × 10 μm. As shown in FIG. 4, the resistors R1 and R2 are thick film resistors formed by sintering a thick film conductor paste by screen printing technology, and the both ends thereof are Ag and Ag / P.
It is connected to a wiring layer 5 made of d, Cu, or the like and having a thickness of about 10 μm. The protective glass 9 is formed by applying a thick-film glass paste to a thickness of about 10 μm after baking,
It was formed by heating and firing at 0 degrees for 0.5 hours.

After the circuit board 2 is inserted into the case 1, the silicon gel portion 3 is formed by a nozzle with a silicon gel (trade name DT).
087, manufactured by Toray Industries, Inc.) into the case 1 and thermally cured at 145 ° C. for 40 minutes. As shown in FIG. 2, the silicon gel portion 3 is injected until the entire surface of the circuit board 2 is completely covered, and the silicon gel portion 3 is injected into the upper part of the internal space of the case 1 (the opening 10 in the present invention). Instead, the lid 6 is formed as described later.

The cover 6 is formed by injecting a liquid epoxy resin (trade name: Ecogel, manufactured by Nippon Pernox Co., Ltd.) through a nozzle after the silicone gel 3 has been cured, thermally curing at 125 ° C. for 2 hours, and cooling. Is done. The molding shrinkage of this epoxy resin is about 96%, and the linear expansion coefficient is about 51 × 10 ⁻⁶ /
° C. Therefore, the center of the lead 4 whose inner end is fixed to the circuit board 2 is fixed to the lid 6 and the lead 4
Has an outer end protruding outside.

The circuit on the circuit board 2 constitutes a monolithic operational amplifier OP and a first-stage sense amplifier having resistors R1 and R2. The voltage amplification factor k of this operational amplifier amplifier circuit is determined by the resistors R1 and R2. It is determined. Hereinafter, features of the present embodiment will be described. As described above, in this embodiment, the interior space of the case 1 is filled with the silicon gel portion 3 except for the opening 10. Therefore, the circuit board 1 warps due to the shrinkage of the mold resin portion made of epoxy resin as in the prior art, and the resistor R
1, the resistance value of R2 does not change.

In this embodiment, the opening 10 of the case 1 is sealed by potting of a liquid epoxy resin, and the lead 4 is further fixed. Therefore, the circuit board 1 is fixed to the lid 6 through the leads 4. In this embodiment, the width of the board fitting groove 12 between the pair of guide projections 11 is larger than the thickness of the circuit board 1.
This prevents displacement of the circuit board 1 due to external force.

As a result, the variation in the voltage amplification factor of the first-stage sense amplifier comprising the operational amplifier voltage amplifier circuit due to the above-described fluctuation of the resistors R1 and R2 could be eliminated. Normally, the voltage amplification rate of the first-stage sense amplifier that amplifies a minute input signal voltage or signal current requires much higher stability than the subsequent circuit stages that handle a larger signal voltage. Thus, variations in the voltage amplification factor can be greatly reduced, and this is suitable for such a first-stage sense amplifier.

(Embodiment 2) FIG. 4 shows another embodiment. In this embodiment, a double wall 19 is provided around the opening 10 of the case 1, and the lid 6 is fitted into a groove between the double walls 19. By doing so, the contact area between the lid 6 and the case 1 increases, and the two mesh with each other, so that it is possible to enhance the bonding and improve the moisture resistance inside.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment;

FIG. 2 is a sectional view showing Example 1.

FIG. 3 is a sectional view showing the first embodiment;

FIG. 4 is a sectional view showing another embodiment;

FIG. 5 is a sectional view of a conventional hybrid IC,

FIG. 6 is a schematic view showing a test apparatus for testing a relationship between a bending force applied to a circuit board and a resistance value change rate of a resistor;

FIG. 7 is a characteristic diagram showing test results obtained by the test apparatus of FIG. 6,

FIG. 8 is a characteristic diagram showing a relationship between a displacement amount (thickness direction) to a circuit board and a resistance change amount of a resistor;

FIG. 9 is a characteristic diagram showing a change in a stress applied to the resistor in accordance with the bending of the circuit board in a longitudinal direction of the circuit board;

[Explanation of symbols]

1 is a case, 2 is a circuit board, 3 is a silicon gel part (flexible
RESIN portion), 4 is read, R1, R2 are resistors, 6 lid,

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroyuki Ban 1-1-1 Showa-cho, Kariya-shi, Aichi Japan Inside Denso Corporation (72) Inventor Kengo Oka 1-1-1, Showa-cho, Kariya-shi, Aichi Japan Nihon Denso Co., Ltd. (56) References JP-A-3-225943 (JP, A) JP-B-50-8495 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 23/28 H01L 23 / 29 H01L 23/31 H01L 21/56

Claims (3)

(57) [Claims] An inner surface has a board insertion groove for holding a circuit board.
And, a case one open end, is accommodated in the a resistor formed integrally casing, a circuit board end Ru held by the substrate insertion groove, one end is fixed to the circuit board , The other end of the case
A lead protruding from the mouth to the outside, and without contacting the substrate at the opening of the case;
Hold the lead and block the opening of the case.
A lid made of a hard resin to be covered, and filled in the case to cover the entire surface of the circuit board
An electronic circuit device comprising: a gel-like soft resin portion having a uniform composition . 2. The electronic circuit device according to claim 1, wherein The contact portion between the lid and the case has a bent structure.
An electronic circuit device comprising: 3. The electronic circuit device according to claim 1, wherein:
hand, The flexible resin portion is made of silicon gel.
Electronic circuit device.