JP4994025B2 - Resin-sealed electronic equipment - Google Patents

Description

  The present invention relates to a resin-sealed electronic device. In particular, the present invention relates to a resin-sealed electronic device provided with a heat sink that dissipates heat.

  In a resin-sealed electronic device that needs to release heat from an electronic component such as an IC chip or a transistor mounted on a circuit board to the outside, a heat sink is fixed to the circuit board. An electronic component is attached to the heat sink so that the heat is transmitted from the electronic component. As a result, heat generated from the electronic component can be released from the heat sink to the outside, and it is possible to protect electronic components that generate a large amount of heat and electronic components that are vulnerable to heat (for example, see Patent Document 1).

  FIG. 5 shows a conventional resin-encapsulated electronic device. The circuit board 110 is disposed in a case not shown. On the circuit board 110, an electronic component 120 such as a transistor is mounted, and a heat sink 130 is attached. The terminal 121 of the electronic component 120 passes through the circuit board 110, and the through end 121 a is soldered to be electrically connected to the circuit pattern of the circuit board 110.

  The heat sink 130 is fixed to the circuit board 110 by the legs 131 penetrating the circuit board 110 and soldering the penetrating ends. The illustrated heat sink 130 has a vertically long shape that rises from the circuit board 110. Further, the plurality of fins 133 extend in the lateral direction with a gap therebetween, improving the heat radiation efficiency.

The electronic component 120 is attached to the heat sink 130 by means of adhesion, screwing or the like while in contact with the heat sink 130. In the resin-encapsulated electronic device, the case is filled with an insulating mold resin, and the heat sink 130 and the electronic component 120 are sealed with the filled mold resin. In the illustrated example, the mold resin 140 is potted and cured on the circuit board 110 so that the resin thickness is such that the upper portion of the heat sink 130 is exposed. By sealing with the mold resin 140, the electronic component 120 can be waterproofed and moisture-proof, and oxidation of the solder portion can be prevented.
JP 2005-86149 A

  In the structure shown in Patent Document 1 and FIG. 5, since heat can be dissipated by heat conduction to the heat sink, the electronic component can be protected from heat. However, inconveniences such as breakage such as cracks occur in the electronic component sealed with the mold resin, and the connection part (soldering part) to the circuit board of the electronic component peels off. These inconveniences are particularly common in electronic devices used for vehicles and outdoors. Accordingly, there is a demand for an electronic device that does not cause breakage of electronic components or peeling of connection portions.

  An object of the present invention is to provide a resin-encapsulated electronic device that can prevent destruction of an electronic component and peeling of a connection portion in a structure in which heat of the electronic component is radiated by a heat sink.

  The present inventors have found that the destruction of the electronic components and the peeling of the connection part are due to the stress caused by the difference in the thermal expansion coefficients of the circuit board, the heat sink, and the mold resin, and the following invention has been completed.

(1) A heat sink fixed to a circuit board, an electronic component mounted on the circuit board in a state of being attached to the heat sink, and an insulating mold resin that seals an arrangement region of the heat sink and the electronic component. A buffer member made of a low-hardness silicone resin that absorbs or reduces stress caused by expansion and contraction of the circuit board, the heat sink, and the mold resin is at least between the heat sink and the circuit board. A resin-encapsulated electronic device characterized by being arranged.

According to the invention of (1), the buffer member is disposed between the heat sink and the circuit board. The buffer member is made of low-hardness silicon resin , and absorbs or reduces stress caused by expansion and contraction of the circuit board, the heat sink, and the mold resin.

For this reason, the thermal expansion coefficients of the circuit board, the heat sink, and the mold resin are different, and the stress generated due to the difference in expansion and contraction is absorbed or reduced when transmitted from the circuit board to the heat sink. As a result, a large stress does not act on the heat sink and the electronic component attached to the heat sink, and the destruction of the electronic component and the peeling off of the connection portion can be prevented.

(2) The resin-sealed electronic device according to (1), wherein the buffer member has adhesiveness.

  According to invention of (2), since a buffer member has adhesiveness, a buffer member can be arrange | positioned between a heat sink and a circuit board, without using an adhesive agent.

(3) The resin-sealed electronic device according to claim 1 or 2, wherein the buffer member has a thermal conductivity larger than that of a mold resin or a circuit board.

  According to the invention of (3), since the heat conductivity of the buffer member is large, the buffer member itself also has a heat dissipation function, and the overall heat dissipation efficiency of the heat sink and the buffer member combined increases.

  In the resin-sealed electronic device according to the present invention, the buffer member disposed between the heat sink and the circuit board absorbs or reduces the stress caused by the expansion and contraction of the circuit board, the heat sink, and the mold resin. Therefore, a large stress does not act on the heat sink and the electronic component attached to the heat sink, and it is possible to prevent the electronic component from being broken and the connecting portion from being peeled off.

  Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments. FIG. 1 is a sectional view showing a first embodiment of the present invention.

  As shown in FIG. 1, an electronic component 2 is mounted on a circuit board 1 on which a circuit pattern is formed. A heat sink 3 is fixed to the circuit board 1. The entire circuit board 1 is disposed in a case not shown.

The heat sink 3 is formed of a metal extruded material such as alumina or aluminum. The heat sink 3 has leg portions 3a. The leg portions 3a penetrate the circuit board 1 and are fixed to the circuit board 1 by soldering the penetrating ends. The heat sink 3 has a vertically long shape that rises from the circuit board 1 and has a vertical plate portion 3b and a plurality of fins 3c extending in the horizontal direction from the vertical plate portion 3b. The plurality of fins 3c are provided with a predetermined interval with respect to the vertical plate portion 3b. By providing the fins 3c, the heat dissipation efficiency of the heat sink 3 is improved.

  As the electronic component 2, a transistor such as an FET (field effect transistor), a diode, or the like is used. The electronic component 2 contacts the heat sink 3 and is attached to the heat sink 3 by adhesion, soldering, screwing, or the like in this contact state. Accordingly, the heat sink 3 can dissipate heat from the electronic component 2. The electronic component 2 has a terminal 2a extending to the circuit board 1 side. The terminal 2a penetrates the circuit board 1, and the electronic component 2 is mounted by soldering the penetrating end 2b of the terminal 2a and connecting to the circuit pattern of the circuit board 1.

On the circuit board 1, the mold resin is potted and cured, so that the heat sink 3 and the electronic component 2 are sealed with the mold resin 4. The mold resin 4 is potted so that the thickness of the upper portion of the heat sink 3 is exposed. As the mold resin 4, an insulating resin such as urethane resin or epoxy resin is used. These mold resins 4 are different in thermal expansion coefficient from the heat sink 3 and the circuit board 1. For example, when an aluminum extruded material is used as the heat sink 3, the thermal expansion coefficient is 23.4 × 10 ⁻⁶ (cm / cm / ° C.), and when a urethane resin is used as the mold resin 4, the thermal expansion coefficient is 14 × 10. ⁻⁵ (cm / cm / ° C.), with different thermal expansion coefficients. Furthermore, the coefficient of thermal expansion when a glass substrate is used as the circuit board 1 has a value different from these.

  A buffer member 5 is disposed between the circuit board 1 and the heat sink 3. The buffer member 5 has a plate shape and is sandwiched between the lowermost fin 3 c closest to the circuit board 1 and the circuit board 1. The buffer member 5 has a thickness that fills the space between the circuit board 1 and the heat sink 3, and the upper and lower surfaces thereof are in contact with and bonded to the fins 3 c and the circuit board 1.

The buffer member 5 is made of an elastic material, more preferably an insulating elastic material. By having elasticity, the amount of expansion and contraction differs based on the difference in thermal expansion coefficients of the circuit board 1, the heat sink 3, and the mold resin 4, and even if stress is generated by this, the stress is absorbed or Acts to alleviate. That is, the stress is absorbed or reduced when the stress is transmitted from the circuit board 1 to the heat sink 3. For this reason, a large stress does not act on the heat sink 3 and the electronic component 2 attached to the heat sink 3, and the electronic component 2 is not broken or the soldered portion with the circuit board 1 is not peeled off.

  The buffer member 5 is preferably a material having adhesiveness in addition to elasticity. By having adhesiveness, the circuit board 1 and the fin 3c of the heat sink 3 can be tightly bonded. Accordingly, an adhesive for fixing the buffer member 5 is not required, and it is not necessary to consider the thermal expansion coefficient and hardness of the adhesive, and the degree of freedom in design increases. Further, since the adhesive is not required, the buffer member 5 acts to absorb or reduce stress more satisfactorily.

  The buffer member 5 is preferably a material having a higher thermal conductivity than the mold resin 4 or the circuit board 1. The buffer member 5 having a high thermal conductivity itself has a heat dissipation function, and the heat dissipation performance of the buffer member 5 is added to the heat dissipation performance of the heat sink 3, so that the heat dissipation efficiency is increased. Therefore, the amount of expansion and contraction of the mold resin 4 and the circuit board 1 based on the temperature change is reduced, and the generated stress is reduced correspondingly, and the adverse effect on the electronic component 2 can be reduced.

  As the buffer member 5 described above, a low hardness silicon resin can be used. Silicone resin has a stable hardness and functions well, and has a chemically and physically stable property. The low hardness silicon resin is a resin having a small hardness while having such characteristics. A low hardness silicon resin having a hardness of about 22 is preferable. The low hardness silicon resin having the hardness of 22 has a thermal conductivity of 1.34 (w / m · k) and a large thermal conductivity. Moreover, this low hardness silicon resin has adhesiveness. Therefore, by using a low-hardness silicon resin as the buffer member 5, there is an advantage that it can be arranged without an adhesive and heat dissipation is good.

  By adopting such a structure, the resin-sealed electronic device shown in FIG. 1 does not receive a large stress on the electronic component 2 and prevents the connection of the electronic component 2 from being broken or soldered. it can. The inventors conducted a heat shock test in which the resin-encapsulated electronic device of FIG. 1 was left in a −40 ° C. atmosphere for 30 minutes and then left in a 100 ° C. atmosphere for 30 minutes. The electronic component 2 was not broken or broken, and the soldered portion of the electronic component 2 was not peeled off.

  FIG. 2 is a cross-sectional view of a resin-encapsulated electronic device according to the second embodiment of the present invention. In this embodiment, a plate-like buffer member 5 is provided between the circuit board 1 and the fin 3 c of the heat sink 3, and a second buffer member 7 is disposed around the heat sink 3. .

  The second buffer member 7 is made of the same material as the buffer member 5 (for example, low hardness silicon resin). Therefore, it can arrange | position, without using an adhesive agent. The buffer member 7 has a cylindrical shape surrounding the heat sink 3 and is disposed so as to surround the sealing portion of the mold resin 4 in the heat sink 3. In this case, the second buffer member 7 is disposed between the mold resin 4 and the heat sink 3 in a state of being in close contact with the outer surface of the heat sink 3.

  In the structure of FIG. 2, the stress is absorbed or reduced by the buffer member 5 provided between the circuit board 1 and the heat sink 3, and the stress by the second buffer member 7 provided between the mold resin 4 and the heat sink 3. Absorption or mitigation works. Thereby, destruction of the electronic component 2 and peeling of a connection part can be prevented further reliably.

  FIG. 3 is a cross-sectional view of a resin-encapsulated electronic device according to the third embodiment of the present invention. In this embodiment, two plate-shaped buffer members 5 and 8 are used. The buffer members 5 and 8 are made of, for example, a low hardness silicon resin.

  The buffer member 5 is disposed between the circuit board 1 and the lowermost fin 3c of the heat sink 3, and the buffer member 8 is sandwiched between the lowermost fin 3c and the upper fin 3c. It is arranged in the state. By arranging the two buffer members 5 and 8 on the fins 3 c of the heat sink 3 in this way, the stress is absorbed or reduced by the two buffer members 5 and 8. As a result, deformation and fluctuation of the heat sink 3 can be suppressed, damage to the electronic component 2 attached to the heat sink 3 can be prevented, and peeling of the connection portion of the electronic component 2 can be prevented.

  FIG. 4 is a sectional view of a resin-encapsulated electronic device according to the fourth embodiment of the present invention. In this embodiment, the cushioning material 9 is provided between the circuit board 1 and the heat sink 3. The buffer member 9 is formed by a plate-like portion 9a sandwiched between the lowermost fin 3c of the heat sink 3 and the circuit board 1, and a peripheral wall portion 9b rising from the periphery of the plate-like portion 9a, and the peripheral wall portion 9b. Has a structure in which the heat sink 3 is placed on the plate-like portion 9a in a state where the lower portion of the heat sink 3 is wrapped. The entire buffer member 9 is formed of a low-hardness silicon resin, and can be arranged without using an adhesive.

  The buffer member 9 shown in FIG. 4 performs the same operation as the buffer member used in FIGS. Further, it can be fixed on the circuit board 1 integrally with the heat sink 3 while being attached to the heat sink 3. Therefore, the buffer member 9 can be easily arranged.

  The present invention is not limited to the above embodiment, and various modifications are possible. For example, the buffer member may be provided at least between the circuit board 1 and the heat sink 3, and other arrangement portions are not limited. The shape of the heat sink 3 is not particularly limited, and may be a simple block shape or a structure in which fins are arranged in the vertical direction.

1 is a cross-sectional view illustrating a resin-sealed electronic device according to a first embodiment of the present invention. It is sectional drawing which shows the resin sealing type electronic device of 2nd Embodiment of this invention. It is sectional drawing which shows the resin sealing type electronic device of 3rd Embodiment of this invention. It is sectional drawing which shows the resin sealing type electronic device of 4th Embodiment of this invention. It is sectional drawing which shows the conventional resin-sealed electronic device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Circuit board 2 Electronic component 2a Terminal 3 Heat sink 3c Fin 5, 8, 9 Buffer member 7 2nd buffer member

Claims (3)

A resin seal comprising: a heat sink fixed to the circuit board; an electronic component mounted on the circuit board in a state of being attached to the heat sink; and an insulating mold resin that seals an arrangement region of the heat sink and the electronic component. A stationary electronic device,
A resin seal characterized in that a buffer member made of low-hardness silicon resin that absorbs or reduces stress caused by expansion and contraction of the circuit board, the heat sink, and the mold resin is disposed at least between the heat sink and the circuit board. Stop-type electronic equipment.   The resin-sealed electronic device according to claim 1, wherein the buffer member has adhesiveness.   The resin-encapsulated electronic device according to claim 1, wherein the buffer member has a thermal conductivity larger than that of the mold resin or the circuit board.

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