JP4375177B2 - Electronic circuit equipment - Google Patents

Description

  The present invention relates to an electronic circuit device having a heat dissipation function and capable of protecting a conductor wiring on a circuit board from static electricity entering from the outside.

  In an electronic circuit device in which an electronic component is mounted on a circuit board, the electronic component generates heat during operation. In addition, when the electronic circuit device is used in a high temperature environment (for example, an engine room of a vehicle), heat is applied to the electronic component from the outside. When the temperature of the electronic component rises beyond the limit due to heat generation, the operational stability is impaired. Therefore, in order to prevent the temperature rise, a heat sink is often attached to the electronic circuit device.

Due to reasons such as the fact that an insulating material that is inexpensive and excellent in heat dissipation has not been developed, the heat dissipation plate to be attached to the electronic circuit device is made of conductive aluminum. For example, in a conventional electronic circuit device (see Patent Document 1), as shown in FIG. 5, a circuit board 77 is placed on a heat radiating plate 72 held by a housing 70 via a heat radiating sheet 73. An electronic component 78 is mounted on the circuit board 77, and a space between the housing 70 and the heat sink 72, the circuit board 77, the electronic component 78, and the like is filled with a resin insulation 75.
Japanese Patent Laid-Open No. 9-18176

  However, in the conventional example, no countermeasure is taken when static electricity or noise (hereinafter referred to as “static electricity”) is applied to the heat radiating plate 72. The insulating resin 75 exists between the heat sink 72 and the circuit board 77, but when a high voltage static electricity or the like is applied to the heat sink 72, the insulation withstand voltage of the insulating resin 75 is exceeded, and a large current flows through the circuit board 77. The conductor wiring (not shown) on the top may melt or break.

  It is also conceivable that one end of the conductor wiring and the heat radiating plate 72 are connected by the first wiring, and the other end of the conductor wiring is connected to the GND. By doing this, the application time of static electricity etc. is short and the energy is small, so if it escapes to GND, fusing of the conductor wiring can be avoided, but when the battery terminal accidentally contacts the heat sink 72 during vehicle maintenance work etc. Can not cope. This is because the battery voltage is lower than the electrostatic voltage, but the application time is much longer than static electricity and the amount of energy is large.

  As a result, a large current flows through the positive terminal of the battery → the first wiring → the heat sink → the conductor wiring → the second wiring → the negative terminal of the battery, causing a short circuit. Thereby, the part with the smallest current capacity, for example, a part of conductor wiring may melt out.

  The present invention has been made in view of the above circumstances. Even when static electricity or a power supply voltage is applied to the heat sink while maintaining good heat dissipation by the conductive heat sink, the conductor wiring on the circuit board is fused. It is an object of the present invention to provide an electronic circuit device that can prevent the above.

  The inventor of the present application came up with the idea that the current flowing through the conductor wiring by the contact of the power supply terminal with the heat sink is limited by the resistance, and the static electricity applied to the circuit board through the heat sink is absorbed by the capacitor. The present invention has been completed.

An electronic circuit device according to the present invention comprises a circuit board (25) having a conductive wiring (26a to 26d) formed on at least one surface and housed in an insulating casing (10). A conductive heat sink (12) attached to the housing in the vicinity of the circuit board, a heat sink side wiring (39) for connecting one end of the conductor wiring to the heat sink, and a DC power source for the other end of the conductor wiring It comprises a GND side wiring (48) connected to the negative terminal (21b) of (20), a resistor (51) and a capacitor (53) inserted in parallel in the conductor wiring (26d).

According to the electronic circuit device of the present invention, when the power supply terminal comes into contact with the heat sink, it is possible to prevent the conductor wiring from fusing by limiting the current flowing through the conductor wiring on one surface of the circuit board. Further, static electricity applied to the circuit board through the heat sink is absorbed by the capacitor, so that electrostatic breakdown of electronic components and insulators can be prevented. According to this electronic circuit device, static electricity or the like can be absorbed by the capacitor in parallel with the resistor. According to the electronic circuit device of the second aspect, thanks to the inserted resistor having a large resistance value, the current flowing through the conductor wiring is limited, and the heat generation amount is reduced.

According to the electronic circuit device of the third aspect , the fusing of the conductor wiring formed on the other surface of the circuit board can be prevented. According to the electronic circuit device of the fourth aspect , when driving the vehicle-mounted battery to control the vehicle-mounted device, fusing of the conductor wiring of the circuit board when the battery line comes into contact with the electronic circuit device is prevented.

  The electronic circuit device of the present invention includes a circuit board, conductor wiring and electronic components, a heat sink, a heat sink side wiring and a GND side wiring, a resistor and a capacitor.

<Heat sink>
The heat sink is made of a conductive material, and the casing made of an insulating material is held in a box-shaped or container-shaped casing. A circuit board (to be described later) is mounted on at least one surface of the heat sink via an insulating adhesive. The heat radiating plate can be formed into a flat plate shape, for example, but is not limited thereto, and may have any shape such as an arc shape or a wave shape.

<Circuit board, conductor wiring>
The circuit board is coupled on a heat sink held by the housing. At the time of coupling, for example, it may be bonded to the heat sink with an insulating adhesive, or may be fixed to the heat sink with a screw tightening rivet or the like.

  A plurality of conductor wirings are formed on at least one surface (for example, the upper surface) of the circuit board, are electrically connected to each other, and an electronic component is mounted thereon. A resistor and a capacitor for protecting the electronic component are mounted on one of the plurality of conductor wirings. If necessary, one or a plurality of conductor wirings can be formed on the other surface (for example, the lower surface) of the circuit board to mount an electronic component (see claim 4).

<Resistance and capacitor>
Resistor and capacitor between the heat sink side pad and the GND side pad in a conductor wiring for mounting the resistor or the like that are arranged in parallel. The resistance limits (reduces) the current flowing through the conductor wiring when the power supply terminal is in contact with the heat sink, and the resistance value is that of the heat sink side wiring, the internal resistance of the conductor wiring, and the internal resistance of the GND side wiring. It is selected to be larger than the total resistance value (see claim 2). Capacitor is intended to absorb it upon application of static electricity or the like (Namasu), the tolerance is determined by the relationship between the voltage value of such static electricity that may be applied.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

(Constitution)
1 and 2 show an electronic circuit device according to an embodiment. This is a case where the present invention is applied to an injector drive unit (EDU). In FIG. 1, the EDU includes a housing 10, a heat sink 12, a circuit board 25, conductor wirings 26a to 26d and electronic components 28a to 28c, a heat sink side wire 39 and a GND wire 48, a resistor 51, a capacitor 53, and the like. More specifically, a plate-shaped heat sink 12 made of aluminum is held by an insulating box-shaped housing 10, and a plurality of signal transmission / reception terminals (terminals) 13 a, 13 b, and 13 c are formed from the heat sink 10 to the housing 12. A pair of power supply terminals (terminals) 17a and 17b are attached.

  Terminals 13a to 13c are connected to predetermined devices 15a to 15c via external wires 14a to 14c. The terminals 17a and 17b are connected to a plus terminal 21a and a minus terminal 21b of the in-vehicle battery 20 via external wires 18a and 18b.

  As shown in FIGS. 1 and 2, a circuit board 25 is mounted on the heat sink 12 via an adhesive 23, and four conductor wirings 26a, 26b, 26c and 26d are formed on the upper surface thereof. Among these, electronic components (circuits) 28a, 28b and 28c and pads 31a, 31b and 31c are mounted on the three conductor wirings 26a, 26b and 26c, respectively. The four conductor wirings 26a to 26d are connected to each other, and their current capacities may be the same or different.

  The electronic components 28a and 28b are connected by a wire 32a, and the electronic components 28b and 28c are connected by a wire 32b. The pads 31a, 31b and 31c are connected to the terminals 13a, 13b and 13c by wires 46a, 46b and 46c. An input side pad 34 is mounted on an extension 26 b 1 extending from the conductor wiring 26 b and connected to the terminal 17 a by a wire 47.

  Further, a heat sink side pad 37 and a GND side pad 41 are mounted on the conductor wiring 26d, and are connected to the heat sink 12 and the terminal 17b by a heat sink side wire 39 and a GND side wire 48, respectively. A resistor 51 and a capacitor 53 are inserted in parallel between the heat sink side pad 37 and the GND side pad 41. The housing 10 is covered with a resin lid 51.

  Wire resistors R1, R2, and R3 exist in the heat sink side wire 39, the conductor wiring 26, and the GND side wire 48, respectively. The resistance value R of the insertion resistor 51 is selected to be much larger than the sum of the resistance values of the wire resistors R1 to R3. The withstand capacity of the capacitor 53 is determined in consideration of the magnitude of high voltage such as static electricity that may be applied.

(Function and effect)
Since the operation of this EDU is well known and is not directly related to the present invention, its description is omitted. According to this EDU, the following effects can be obtained.

  (A) The heat generated by the electronic components 28a to 28c on the conductor wirings 26a to 26c during the operation of the electronic circuit device is dissipated by the heat radiating plate 12 disposed immediately below the circuit board 25. Aluminum, which is the material of the heat radiating plate 12, has good heat dissipation, so that the generated heat is efficiently heat-exchanged with air and air-cooled.

(B) Contact of power supply terminal The case where the battery 20 contacts the heat radiating plate 12 will be described with reference to FIGS. In this case, a large current flows through the positive terminal 21a of the battery 20 → the heat sink 12 → the heat sink side wire 39 → the conductor wiring 26d → the terminal 17b → the external wire 18b → the negative terminal 21b of the battery 20. However, the resistance 51 inserted into the conductor wiring 26d prevents the conductor wiring 26d from being melted. For example, when the voltage of the battery 20 is 12V, it is assumed that the minimum current capacity among the current capacities of the plurality of conductor wirings 26a to 26d is 1.2A. In this case, if the resistance value of the resistor 51 is selected to be 1Ω or more, the current flowing through the heat sink side wire 39, the conductor wiring (any one of 26a to 26d) having the minimum current capacity, and the GND side wire 48 is 1.2A. Limiting to the following, fusing of the conductor wiring (any one of 26a to 26d) having the minimum current capacity is prevented.

(C) Application of Static Electricity On the other hand, a case where static electricity or the like is applied from the outside via the heat sink 12 will be described with reference to FIGS. 1, 2, and 4. The heat sink 12 and the circuit board 25 are insulated from each other by the adhesive 23. However, due to the arrangement of the resistor 51, when the high voltage of static electricity is applied to the heat sink 12, the insulation withstand voltage of the adhesive 23 may be exceeded. is there. In this case, a high voltage may be applied to the electronic components 28a to 28c mounted on the conductor wirings 26a to 26c on the circuit board 25. However, by providing the capacitor 53 on the conductor wiring 26d, the high voltage can be absorbed and the electrostatic breakdown of the electronic components 28a to 28c can be prevented.

  The high voltage absorbed by the capacitor 53 is accumulated as electric charge and then consumed by the resistor 51 arranged in parallel therewith, so that the energy held by the high voltage disappears and is harmless to the circuit. It becomes a state.

It is explanatory drawing of the injector drive device with which the Example of this invention was applied. It is 2-2 sectional drawing in FIG. It is operation | movement explanatory drawing of the said Example (at the time of the contact with the heat sink of a power supply terminal). It is operation | movement explanatory drawing of the said Example (at the time of application to a heat sink, such as static electricity). It is principal part sectional drawing which shows a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10: Housing | casing 12: Heat sink 20: Battery 21a: Positive terminal 21b: Negative terminal 25: Circuit board 26a to 26d: Conductor wiring 28a to 28c: Electronic component 39: Heat sink side wire 48: GND side wire 51: Resistor 53 : Capacitor

Claims (4)

A circuit board housed in an insulating housing and having conductor wiring formed on at least one surface thereof;
A conductive heat sink attached to the housing in proximity to the circuit board;
A heat sink side wiring for connecting one end of the conductor wiring to the heat sink, and a GND side wiring for connecting the other end of the conductor wiring to the negative terminal of the DC power source;
A resistor and a capacitor inserted in parallel in the conductor wiring; and
An electronic circuit device comprising:   2. The electronic circuit device according to claim 1, wherein a resistance value of the resistor is larger than a total of resistance values of internal resistances of the conductor wiring, the heat sink side wiring, and the GND side wiring. The electronic circuit device according to claim 1, wherein conductor wiring is formed on the other surface of the circuit board . The electronic circuit device according to claim 1, wherein the DC power supply is an in-vehicle battery .

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