JP3628028B2 - Electronic circuit equipment - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an electronic circuit device, and more particularly to a resin package type hybrid IC.
[0002]
[Prior art]
Conventional resin package type hybrid ICs are classified into SIP type and DIP type according to the lead take-out structure. However, in the case of resin sealing (mold), the mold or immersion method, transfer method, etc. A circuit board is inserted in the case in advance and sealed with a liquid or powdery thermosetting resin (for example, epoxy resin or silicone resin).
[0003]
[Problems to be solved by the invention]
However, in the conventional resin package type hybrid IC described above, the difference in shrinkage rate and thermal expansion coefficient between the mold resin part and the circuit board mainly during shrinkage when the sealing resin is cured and subsequent expansion and shrinkage of the resin due to cooling. As a result, a stress is generated between the two, and this stress acts on the resistor fixed to the circuit board. As a result, the resistance value of the resistor changes according to the received stress.
[0004]
According to the test and analysis by the present inventors, the compressive stress and the bending stress in the direction perpendicular to the surface act on the circuit board due to the shrinkage of the sealing resin portion, and the bending stress exerts compressive or tensile stress on the resistor. I understood it. Since the bending stress varies in each part of the circuit board, the resistance value of the resistor varies depending on the fixed position of the resistor on the circuit board. As a result, the output of the circuit varies. In addition, it was confirmed that the resistance value of the resistor also changed due to the external force applied to the hybrid IC.
[0005]
The present invention has been made in view of the above problems, and provides an electronic circuit device that can reduce circuit output variations due to resistance value fluctuations of resistors caused by stress generated between a sealing resin portion and a circuit board. Its purpose is to provide.
[0006]
[Means for Solving the Problems]
An electronic circuit device of the present invention is fixed to both sides of a circuit board housed in a case, a pair of guide protrusions disposed on an inner surface of the case and holding a short side of the circuit board, and the circuit board. It includes a plurality of resistors interconnected formed by combining resistors and a passive circuit element and the active circuit element mounted on the circuit board, and a mold resin portion filled in the case was, the circuit board a plurality of resistors that are individually fixed to both sides of the is characterized that you have been fixed at a position equal distance from the short side of the circuit board.
In a preferred embodiment, the plurality of resistors individually fixed on both surfaces of the circuit board are connected in series with each other.
[0007]
As the resistor referred to in the present invention, a thin film resistor formed by various PVD methods or CVD methods can be employed in addition to a thick film resistor formed by firing after printing. These resistors can be bonded and fixed to the circuit board with a conductive paste, adhesive, solder, or the like, and other resistors formed directly on the circuit board are also included. These resistors are mounted on a circuit board together with other passive circuit elements such as capacitors and active circuit elements such as ICs and transistors.
[0008]
[Operation and effect of the invention]
Stress is generated between the sealing resin part and the circuit board due to shrinkage at the time of curing of the sealing resin part and expansion / shrinkage after heating / cooling, and the circuit board is caused by a difference in stress acting on the front and back of the circuit board. Is warped. Alternatively, the circuit board is warped by an external force. Due to this warpage, a compressive stress is applied to the resistor fixed to one surface of the circuit board, and a tensile stress is applied to the resistor fixed to the other surface. The resistance value of the resistor subjected to compressive stress decreases and the resistance value of the resistor subjected to tensile stress increases.
[0009]
In the present invention, a plurality of resistors are interconnected to form a combined resistor, and the resistor having the increased resistance value is the resistance of the combined resistor due to the influence of the resistor having the decreased resistance value on the resistance change of the combined resistor. Cancel some or all of the impact on the change.
In this way, the change in the resistance value of the composite resistor fixed to the circuit board is reduced or offset despite the deformation of the circuit board due to the stress or external force between the sealing resin portion and the circuit board. .
[0010]
【Example】
(Example 1)
One embodiment of the electronic circuit device of the present invention is shown in FIGS.
This electronic circuit device is a hybrid IC, and includes a case 1, a circuit board 2 accommodated in the case 1, a mold resin portion 3 filled in the case 1, and one end of the circuit board. 2 and a lead 4 that protrudes to the outside through the mold resin portion 3. In FIG. 1, the mold resin portion 3 on the main surface of the circuit board 2 is separated and shown.
[0011]
The case 1 has a rectangular hollow body shape of 18 mm × 50 mm × 6 mm in height, width, and height, and the bottom surface is opened. The wall thickness of the case 1 is about 1 mm, and is formed by injection molding of PBT resin. A pair of guide protrusions 11 (see FIG. 3) are provided in parallel with each other on both inner end faces located at both longitudinal ends of the case 1.
The circuit board 2 is a multilayer board made of alumina, and both short sides 21 and 22 of the circuit board 2 are gently fitted and held between the pair of guide protrusions 11. The dimensions of the circuit board 2 are vertical, horizontal, thickness 13 mm × 47.5 mm × 0.8 mm, and its linear expansion coefficient is about 7.5 × 10 ⁻⁶ / ° C. A single-layer or multilayer wiring pattern (not shown) is formed on the circuit board 2. Various circuit components are fixed and electrically connected to one surface of the circuit board 2. Particularly in this embodiment, the resistor R1 is fixed to the circuit element mounting surface A of the circuit board 2 so as to be close to the short side 21 of the circuit board 2 and at a distance L1 from the short side 21. A resistor R2 is fixed to the back surface B of 2 near the short side 21 of the circuit board 2 and at a distance L1 from the short side 21 (see FIG. 3).
[0012]
The resistors R1 and R2 are formed of a rectangular film having a length, width, and thickness of 1.5 mm × 0.85 mm × 10 μm, and the longitudinal directions of the resistors R1 and R2 are parallel to the short side 21. As shown in FIG. 4, the resistors R1 and R2 are thick film resistors formed by baking a thick film resistor paste by a screen printing technique and baked, and Ag, Ag / Pd, Cu, etc. are provided at both ends thereof. Wiring layers 5a to 5d having a thickness of about 10 μm are formed.
[0013]
Further, a through hole 6 is opened in the circuit board 2, and a buried conductor 7 is buried in the through hole 6, and the buried conductor 7 connects the wiring layer 5b and the wiring layer 5c, whereby the resistors R1 and R2 are connected to each other. The combined resistor R is connected in series.
The mold resin portion 3 is formed by inserting the circuit board 2 into the case 1, injecting an epoxy resin into the case 1, thermosetting, and cooling. The linear expansion coefficient of this epoxy resin is about 51 × 10 ⁻⁶ / ° C., and the volume shrinkage ratio after curing from the liquid state is about 96%.
[0014]
The circuit on the circuit board 2 has a monolithic operational amplifier OP and a first-stage sense amplifier composed of resistors R1 and R2. The voltage amplification factor k of the operational amplifier amplifier circuit is proportional to the resistance value of the combined resistor R. It is supposed to be.
The hybrid IC described above warps to the circuit element mounting surface A side as schematically shown in FIG. 5 due to curing shrinkage of the sealing resin portion 3. This is because the amount of sealing resin on the circuit element mounting surface A side in the case is larger than the amount of resin on the back surface side, so that the compressive force applied to the circuit element mounting surface A of the circuit board 2 (particularly in the longitudinal direction). However, it is considered that it is superior to that of the back surface B, and for this reason, the center portion of the circuit board 2 warps in the direction in which the circuit element mounting surface A is depressed with respect to both short sides 21 and 22 of the circuit board 2. The amount of warpage, that is, the stress on the substrate, naturally changes depending on the temperature change. Further, although the center portion of the circuit board 2 warps in the direction in which the circuit element mounting surface A is depressed with respect to both the long sides 23 and 24 of the circuit board 2, the amount of warpage is relatively small. Further, each part of the circuit board 2 is locally strengthened by each circuit element fixed on the circuit element mounting surface A, and the amount of warpage and stress distribution of each part varies, but in this embodiment it is ignored.
[0015]
Due to the warp of the circuit board 2 (that is, the bending stress in the direction perpendicular to the surface of the circuit board 2), a compressive stress is applied to the resistor R1 fixed thereon, and a tensile stress is applied to the resistor R2.
The relationship between the stress applied to the circuit board 2 and the change in the resistance value of the resistor fixed to the circuit board was examined. As shown in FIG. 6, the test circuit board 20 has dimensions of 13 mm × 47.5 mm × 0.8 mm in length, width, and thickness. Supported. The resistor R was fixed at a position of 15.3 mm from the short side 21 of the circuit board 20, and the center of the circuit board 20 was pressed toward the circuit board 20 to examine a change in resistance value. The result is shown in FIG.
[0016]
From FIG. 7, the pressing force (bending stress) and the change of the resistance value are in a substantially linear relationship. When the compressive stress is generated in the resistor R1 due to the bending of the circuit board 2 due to the pressing force, the resistance is decreased. It has been found that resistance increases when tensile stress is generated in R1. In this embodiment, the longitudinal direction of the resistor R1, that is, the energizing direction, is the longitudinal direction of the circuit board 2. It has been found that when compressive stress is generated in the resistor R1, the resistance is decreased, and when tensile stress is generated in the resistor R1, the resistance is increased.
[0017]
Next, the relationship between the warpage amount (displacement amount) and the resistance value change amount in the circuit board 20 of FIG. 6 was examined. The result is shown in FIG. However, the amount of warpage was the maximum displacement at the center of the substrate.
In addition, when both the short sides 21 and 22 of the circuit board 2 are supported and the center part is pressed, the compressive or tensile stress acting on each part in the longitudinal direction of the circuit board 2 due to elastic deformation of the circuit board 2 is shown in the schematic diagram of FIG. As shown in the figure, the central portion changes so as to be approximately 0 at both short sides 21 and 22 at the maximum.
[0018]
Next, the change in the resistance value of the resistor R when the circuit board 20 having the resistor R fixed at the above-described position was accommodated in the case 1 and molded entirely with the mold resin portion was examined. As a result, the average value of the resistance value change rate of the resistor R1 was about -0.7%.
Hereinafter, features of the present embodiment will be described.
In this embodiment, the resistors R <b> 1 and R <b> 2 have the same resistance value, and are fixed on the front and back of the circuit board 2 at an equal distance from the short side 21 in the longitudinal direction of the circuit board 2. As a result, the compressive stress and the tensile stress acting on the resistors R1 and R2 through the circuit board 2 described above are equal, and the resistance value change amounts of the resistors R1 and R2 are equal, and the increasing / decreasing directions are opposite.
[0019]
Therefore, as shown in FIG. 11, when both resistors R1 and R2 having a resistance value r when the applied stress is 0 are connected in series, if the resistance value change due to the applied stress is Δr and −Δr, the combined resistance The resistance value of R becomes r + r + Δr−Δr = 2r, and the resistance value change can be canceled with respect to the applied stress.
In this embodiment, the resistors R1 and R2 are arranged close to the short side 21, so that the stress acting on the resistors R1 and R2 proportional to the bending stress of the circuit board 2 is small, and the variation in stress can be reduced. . As a result, the influence of the warp of the circuit board 2 on the output characteristics (voltage amplification factor k) of the operational amplifier voltage amplifier circuit is reduced.
[0020]
Furthermore, in this embodiment, the longitudinal directions of the resistors R1 and R2 are arranged in parallel with the short side 21. In this way, variation in compressive stress acting on each part of resistors R1 and R2 is small, and variation in resistance values of both resistors R1 and R2 is also small.
As a result of the above, the variation in the voltage amplification factor of the first-stage sense amplifier comprising this operational amplifier voltage amplifier circuit could be greatly reduced. Normally, the voltage amplification factor of the first-stage sense amplifier that amplifies a minute input signal voltage or signal current requires much higher stability than the subsequent circuit stage that handles a larger signal voltage. Therefore, the variation in voltage amplification factor can be greatly reduced, which is suitable for such a first-stage sense amplifier.
[0021]
The longitudinal directions of the resistors R1 and R2 can be parallel to the long sides 23 and 24 of the circuit board 2, and the angle between the longitudinal direction of the resistors R1 and R2 and the longitudinal direction of the circuit board 2 is also possible. May be a predetermined value. Moreover, as shown in FIG. 12, it is also possible to provide two through holes and connect the resistors R1 and R2 in parallel. It is also possible to cover the surfaces of the resistors R1 and R2 on both sides with a film such as silicon gel for stress relaxation. In the above embodiment, the initial resistance values of the resistors R1 and R2 are set to be equal, but may not be equal. That is, since the distance is equal from the short side 21 when they are equal, the change in the resistance value can be almost zero, but the change in the resistance value of the composite resistor R can be reduced even if the initial resistance value is slightly different. I can. Further, in the above embodiment, the distances from the short sides 21 of both resistors R1 and R2 are made equal, but the change in resistance value R can be reduced even if they are not equal.
[0022]
(Example 2)
Another embodiment is shown in FIG.
In this embodiment, the resistor R1 is fixed at a distance from the short side 21 to L1, and the resistor R2 is fixed at a distance from the short side 21 to L2. The resistance value fluctuation amount with respect to the stress of each resistor is a function (F (L ₁ ), F (L ₂ )) of the distance from the edge of the substrate. For this reason, if the resistors are arranged (fixed) in consideration of the resistance value fluctuation amount of the resistor used (depending on the material, shape, etc.), the combined resistance value fluctuation of the two resistors can be reduced to zero.
[0023]
In the above embodiment, the canceling of the resistance value change by the pair of resistors R1 and R2 has been described. However, it is natural that the combined resistor R can be configured by three or more resistors.
(Example 3)
Another embodiment is shown in FIG.
In this embodiment, the wiring layers 5b and 5c of the resistors R1 and R2 are short-circuited by leads 4 instead of through holes. 8 is solder.
[0024]
In this way, the through hole can be omitted.
In the above embodiments, application examples to the operational amplifier voltage amplification circuit have been described. However, the present invention is applied to various circuits such as current amplification, waveform processing, frequency processing, digital processing, comparator, A / D conversion, and D / A conversion. Naturally, it can be widely applied, and is particularly suitable for the first stage portion of these circuits requiring the highest precision.
[Brief description of the drawings]
1 is a cross-sectional view showing Example 1;
FIG. 2 is a sectional view showing Example 1;
FIG. 3 is a sectional view showing Example 1;
4 is an enlarged R2 cross-sectional view of the resistor of FIG.
FIG. 5 is a schematic diagram showing warpage of a circuit board;
FIG. 6 is a schematic diagram showing a test apparatus for testing the relationship between the bending force to the circuit board and the resistance value change rate of the resistor;
FIG. 7 is a characteristic diagram showing a test result by the test apparatus of FIG.
FIG. 8 is a characteristic diagram showing the relationship between the displacement amount (thickness direction) to the circuit board and the resistance value change amount of the resistor;
FIG. 9 is a characteristic diagram showing the change in the longitudinal direction of the circuit board of the stress applied to the resistor as the circuit board is curved;
FIG. 10 is a sectional view showing Example 2.
FIG. 11 is a circuit diagram showing series connection of resistors R1 and R2.
FIG. 12 is a circuit diagram showing parallel connection of resistors R1 and R2.
FIG. 13 is a sectional view showing Example 3.
[Brief description of symbols]
1 is a case, 2 is a circuit board, 3 is a mold resin part, 4 is a lead, R1 and R2 are resistors,

Claims (2)

A circuit board housed in a case;
A pair of guide protrusions disposed on the inner surface of the case to hold the short side of the circuit board;
A combined resistor formed by interconnecting a plurality of resistors individually fixed on both sides of the circuit board;
A passive circuit element and an active circuit element mounted on the circuit board;
A mold resin portion filled in the case ,
The electronic circuit device, wherein the plurality of resistors individually fixed on both surfaces of the circuit board are fixed at positions at an equal distance from the short side of the circuit board. The electronic circuit device according to claim 1, wherein the plurality of resistors individually fixed to both surfaces of the circuit board are connected in series to each other.

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