JP2000196011A - Electronic device and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a connecting member between boards and a structural member to be simplified in structure and a circuit to be lessened in size and cost, by a method wherein a heat releasing device is mounted on a metal circuit board as a sub-board, a low heat releasing device and input/output terminals are mounted on a resin circuit board as a mother board, and the sub-board and the mother board are electrically connected together and housed in a resin case. SOLUTION: A heat releasing device 7 such as a power transistor, a diode or the like and resistors are fixed on pads 5 on a metal circuit board 1 for the formation of a sub-board. Electronic parts such as a low heat releasing device 11, power terminals 12, signal terminals 13 or the like are mounted and connected with solder 6 on a resin circuit board 9 for the formation of a mother board. The mother board and the sub-board are mounted in a resin case 16 with an adhesive agent, the pads 5 on the boards 1 and 9 are electrically connected together with bonding wires 8 and sealed up with a filler 15. By this setup, a connecting member between boards and a structural member can be simplified in structure, and an electronic circuit can be lessened in size and cost ensuring it of reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic device for integrally mounting a board on which a low-heat-generating electronic component is mounted in a control low-power circuit and a board on which a high-heat-circuit electronic component is mounted on a high-power circuit. And a method of manufacturing the same.

[0002]

2. Description of the Related Art FIG.
1 shows an electronic device shown in the public relations. In FIG. 7, 1 is a metal circuit board, 9 is a resin circuit board, and both boards are laminated. 7 is a heat-generating element 7, 8 is a bonding wire, 12 is a power terminal, 13 is a signal terminal, 11 is a low heat-generating element, and the heat-generating element 7, the power terminal 12, and the signal terminal 13 are metal circuit boards. The low heat generating element 11 is mounted on the resin circuit board 9. 42 is a protective resin, 41 is a sealing resin, and bonding wires 8 are formed between the heat generating element 7 and the metal circuit board 1, between the low heat generating element 11 and the resin circuit board 9, and between the metal circuit board 1 and the resin circuit board 9, respectively. And are sealed with a protective resin. Further, the laminated substrates are sealed with a sealing resin 41 except for the power terminals 12 and the signal terminals 13.

The operation and manufacturing method will be described. In FIG. 7, a low heat-generating element 11 composed of a semiconductor chip such as a microcomputer and a memory is mounted on a resin circuit board 9 by thermosetting of a solder paste. The elements 11 are electrically connected. Then, the bonding wire 8 and the heat generating element 7
Is sealed with a protective resin 42.

A heat-generating element 7 and a resin circuit board 9 previously manufactured are mounted on the metal circuit board 1 by applying a solder paste and heat curing, and further, the resin circuit board 9 and the metal circuit board 9 are bonded by bonding wires 8. 1 and the heat generating element 7 and the metal circuit board 1 are electrically connected. After that, the bonding wires 8 are sealed with the protective resin 42, and the electronic components including the resin circuit board 9 mounted on the metal circuit board 1 are further sealed with the sealing resin 41, and the power terminal 12 and the signal The terminal 13 is connected with the solder 6. Here, a desired operation is performed by applying a predetermined power supply and a signal to both terminals on the metal circuit board 1.

FIGS. 8 and 9 show a state in which the metal circuit board 1 is mounted on a resin case 16 and the power terminals 12 and the signal terminals 13 are inserted into predetermined positions of the resin circuit board 9 and the solder 6
FIG. 3 is a view showing a conventional electronic device according to an embodiment, which is fixed at a position shown in FIG. On the metal circuit board 1, heat-generating elements such as a full-wave rectifier circuit and an inverter circuit are provided.
On the upper side, a low heat generating element forming a pre-driver circuit 27, a waveform generating circuit and the like, and a heat generating element 7 forming a rotor position detecting circuit and the like are mounted.

In FIG. 8, a power terminal 12 and a signal terminal 1 are shown.
Reference numeral 3 denotes an integral structure with the resin case 16, and the metal circuit board 1 and both terminals are connected by bonding wires 8. In FIG. 9, the power terminal 12 and the signal terminal 13 are connected on the metal circuit board 1 by the solder 6. In both figures, both terminals of the power terminal 12 and the signal terminal 13 and the resin circuit board 9 are connected by the solder 6 in a different process from the circuit components already mounted on the resin circuit board 9. I have.

[0007]

[0005] Resin circuit boards are generally and widely used as inexpensive circuit boards. In mounting a power semiconductor element having a large amount of heat, such as a power transistor, it is necessary to mount a heat radiation fin on the power semiconductor element and mount it on a substrate, which makes it difficult to reduce the size of the substrate. on the other hand,
Metallic circuit boards have good thermal conductivity and are suitable for mounting power semiconductor elements such as power transistors that generate a large amount of heat.However, they are more expensive than resin circuit boards. And the cost of the substrate has been increased.

[0008] In addition, there is another problem that dust adheres to the mounted chip parts and the like after the dust adheres thereto, thereby causing insulation deterioration of the different voltage portion and reducing the reliability of the circuit.

In addition, the distance between the conductor patterns of the high-voltage circuit portion must be secured in proportion to the voltage difference in order to secure the electrical insulation performance. It is had.

The switching speed of the power transistor in the inverter circuit is increased, and a steep current (high di / dt) during the operation of the power transistor flows through the inductance L of the conductor pattern, so that a surge voltage is generated in the conductor pattern. As a result, there have been problems such as a malfunction of the power transistor or its drive circuit and an increase in the level of noise generated from the device.

As shown in the conventional example, since a resin circuit board 9 as a mother board is closely laminated on a metal circuit board 1 as a sub-board, an expensive metal circuit board 1 is used.
The area of the formed sub-substrate has increased. Also,
Since the output terminals of the circuit composed of the heat-generating element 7 are mounted on the metal circuit board 1, soldering of electronic components on the metal circuit board 1 or the resin circuit board 9, such as manual or automatic soldering, is performed. It is necessary to provide a process different from the attaching process and to mount the device, and there is a problem that the process is complicated.

As an electrical connection method between the metal circuit board 1 and the resin circuit board 9, a connection method using a connector, manual soldering after inserting the terminals mounted on the sub-board into the through holes of the mother board, and the like are available. There are also methods, and both methods have led to an increase in the material cost, manufacturing cost, and processing time of the connector and the like.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is possible to simplify connection members and structural members between substrates, and to reduce the size and cost of a circuit while ensuring the reliability of an electronic circuit. It is an object of the present invention to obtain an electronic device that can be reduced in cost.

[0014]

An electronic device according to the present invention comprises a sub-substrate having a heat generating element mounted on a metal circuit board, and a resin circuit board having a low heat generating element and input / output of signals or power. A mother board on which output terminals are mounted; connecting means for electrically connecting the mother board and the sub-board; and a resin case for housing the sub-board and the mother board.

Further, the mother substrate and the sub-substrate are sealed with a resin.

The input / output terminals on the mother board are composed of signal terminals for inputting / outputting signals and power terminals for inputting / outputting power.

Further, the mother substrate and the sub-substrate are arranged in a substantially planar shape in a resin case, and the heat radiation fins having a low height are fixed to the lower portion of the sub-substrate.

Further, the low heat generating element mounted on the mother board constitutes a waveform generating circuit for driving the heat generating element mounted on the sub-board and a pre-driver circuit.

[0019] The power supply apparatus further includes a voltage detection circuit connected to the power terminal on the motherboard and configured by a passive element, and detecting a voltage of the power terminal.

Further, a rotor position detecting circuit for detecting a rotor position of the electric motor is provided.

The heat-generating element mounted on the sub-board is a power semiconductor element constituting a rectifier circuit for converting AC power from an AC power supply to DC and an inverter circuit for converting the DC to AC. .

The method of manufacturing an electronic device comprises the steps of mounting a low heat generating element and input / output terminals on a mother board, performing flow soldering, and applying a solder to the sub-substrate, and then forming a heat generating layer on the solder. Mounting the element and performing reflow soldering, mounting the mother board and the sub-board in a resin case, and between the heat-generating elements and the circuit on the sub-board, and between the mother board and the circuit on the sub-board. Electrically connecting and sealing with resin.

The mounting of the mother board and the sub-board in the resin case is such that the mother board and the sub-board are inserted into the resin case from the same direction and fixed by fitting.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Embodiment 1 of the present invention will be described with reference to FIGS. FIG. 1 is a sectional view showing an electronic device according to a first embodiment of the present invention, FIG. 2 is a circuit block diagram of an electronic device for driving an electric motor by an inverter, and FIG. 3 is a circuit diagram of the inverter circuit and the pre-driver circuit shown in FIG. FIG. In FIG. 1, 1 is a metal circuit board, 2 is an aluminum plate, 3 is an insulating layer, 4 is a conductor pattern, 5 is a pad, 6 is solder, 7 is a heating element such as a power transistor or a power semiconductor such as a diode, 8
Is a bonding wire. The metal circuit board 1 is formed by providing an insulating layer 3 of synthetic resin or the like on one surface of an aluminum plate 2 and forming a conductor pattern 4 and a pad 5 on the surface of the insulating layer 3 for forming a circuit. On the metal circuit board 1, a power transistor, a power diode, a resistor and the like are fixed on a pad 5 by solder 6. The sub-board is composed of the metal circuit board 1 on which the above-mentioned electronic components are mounted. MOSFETs for power transistors
There are types such as IGBTs and bipolar transistors. The semiconductor on the metal circuit board 1 may be a chip element, a surface-mounted electronic component mixedly mounted, or any one of them.

9 is a resin circuit board, 10 is a land,
Reference numeral 11 denotes a low heat-generating element such as a microcomputer, a capacitor, a resistor, a small signal transistor, a small signal diode, 12 a power terminal, and 13 a signal terminal. On the resin circuit board 9, a low heat-generating element 11, a power terminal 12, a signal terminal 1
Electronic components such as 3 are connected by solder 6 and mounted. The mother board is composed of a resin circuit board 9 on which the electronic components are mounted. As the resin circuit board 9, there is a board laminated using paper, glass or the like as a base material and using epoxy or phenol as a resin.

Reference numeral 14 denotes a radiation fin, reference numeral 15 denotes a filler, reference numeral 16 denotes a resin case. The mother board and the sub-board are mounted on the resin case 16 with an adhesive or the like. It is electrically connected. The heat generating element 7 on the metal circuit board 1 and the pad 5 on the resin circuit board 9 may be directly connected by the bonding wire 8. In the resin case 16, a filler 15 such as silicon gel or epoxy resin is filled with the bonding wires 8, the height of the electronic components mounted on the metal circuit board 1 or more, and the power terminals 1.
2. It is injected so as to be below the connection portion of the signal terminal 13.

Here, if the filler 15 is selected from a transparent material, the mounting state of the electronic components on the metal circuit board 1 and the resin circuit board 9 and the connection state of the bonding wires 8 even after the electronic device is manufactured. Can be visually grasped, and early detection of manufacturing defects becomes possible. Also, the radiation fins 14
Is fixed to the resin case 16 with screws or the like so as to make surface contact with the aluminum plate 2 of the sub-board.

FIG. 2 shows a specific example of the electronic device, and is a circuit block diagram of the electronic device that drives an electric motor by an inverter. 1 is a circuit block diagram of the electronic device according to the first embodiment of the present invention. In the figure, 17 is an AC power supply connected to the power terminal 12 of the electronic circuit, 18 is a full-wave rectifier circuit, 19 is a reactor connected to the power terminal 12, 21 is a diode, and 23 is an output of the full-wave rectifier circuit 18. , A smoothing capacitor connected to the reactor 19 via a diode 21; 25, a motor; 24, an inverter circuit connected to the smoothing capacitor 23 to output an arbitrary frequency and voltage to supply power to the motor 25; And connected between the midpoint of the series connection of the reactor 19 and the diode 21 and the negative side of the smoothing capacitor 23. 22 is a power supply current detection resistor.

Reference numeral 26 denotes a waveform generating circuit for driving signals of the transistor 20 and the inverter circuit 24, which comprises a microprocessor (microcomputer) or the like. 27, a pre-driver circuit for driving the transistor 20 and the inverter circuit 24; 28, a rotor position detection circuit for detecting the rotor position in the motor 25; 29, a bus voltage detection for detecting the voltage across the smoothing capacitor 23 Circuit, a waveform generation circuit 2
6. The low heat generating components of the pre-driver circuit 27, the bus voltage detecting circuit 29 and the rotor position detecting circuit 28 are mounted on the resin circuit board 9. In addition, the power terminal 12 is electrically connected to the AC power supply 17, the reactor 19, the smoothing capacitor 23, and the electric motor 24.
It is mounted on a resin circuit board 9 for transmitting and receiving signals to and from an external circuit.

30 is an operation command signal, 31 is a PWM signal,
32 is an inverter drive signal, 33 is a transistor drive signal, 34 is a rotor position signal, 35 is a detected current signal, 36
This is a bus voltage signal. The rotor position detection circuit 28 receives the output voltage of the inverter circuit 24 and outputs a rotor position signal 34.
Is output to the waveform generation circuit 26. Bus voltage detection circuit 29
Outputs a bus voltage signal 36 to the waveform generation circuit 26 by dividing the voltage between both ends of the smoothing capacitor 23 by a resistor. The waveform generation circuit 26 receives the operation command signal 30, the rotor position signal 34, the detected current signal 35, and the bus voltage signal 36 connected to the signal terminal 13, and outputs the PWM signal 31. The PWM signal 31 includes a driving signal for the transistor 20 and the inverter circuit 24. The pre-driver circuit 27 receives the PWM signal 31 as an input,
And a drive signal for driving the inverter drive circuit 24.

Among the input / output terminals on the resin circuit board 9, the power terminals 12 are connected to the input of the AC power supply 17 and the reactor 1.
9, the output of the smoothing capacitor 23 and the inverter circuit 24, which are the minimum necessary terminals for driving the motor 25 by the inverter. The smoothing capacitor 23 is
If mounted on the top, the number of power terminals 12 can be reduced. The signal terminal 13 is connected to the operation command signal 3.
In addition to 0, a power supply for the low heat generation element 11 or an abnormal stop (error) signal of the electronic device may be provided.

FIG. 3 is a circuit diagram showing one phase of the inverter circuit 24 and the pre-driver circuit 27 in FIG. 2, and is a circuit in which an inverter transistor 37a or 37b and an inverter diode 38a or 38b are connected in anti-parallel. Are connected in series between the high voltage part P and the low voltage part N of the smoothing capacitor 23. Driving pre-driver circuits 27a and 27b are connected to the respective inverter transistors 37a and 37b.

On the metal circuit board 1, a full-wave rectifier circuit 18,
The transistor 20, the diode 21, the power supply current detection resistor 22, and the inverter transistor 37 and the inverter diode 38 constituting the inverter circuit 24 are mounted. In addition, resistors that generate heat in the rotor position detection circuit 28 and the bus voltage detection circuit 29 are also mounted. In addition, an electronic component generating a large amount of heat, such as a transistor for a switching power supply, may be mounted.

Next, the operation of the electronic circuit according to the first embodiment of the present invention will be described with reference to FIG. First, the AC power supply 17 is converted to DC by the full-wave rectifier circuit 18 and
In step 3, the DC voltage is reduced to a pulsating little DC voltage. When the operation command signal 30 is input, the waveform generation circuit 26 determines a target DC voltage command VDC * based on the command, further inputs a bus voltage signal 36 from the bus voltage detection circuit 29, and When the PWM signal 31 is output to the pre-driver circuit 27 so as to be equal to VDC * and the current flowing through the power supply current detection resistor 22 becomes a sinusoidal current synchronized with the power supply voltage, the transistor 20 is turned on by the transistor drive signal 33. Driven. The voltage is boosted by the switching operation of the transistor 20 and the energy storage effect of the reactor 19, and the boosted pulsating voltage is supplied to the smoothing capacitor 23 to be a stable DC voltage.

The waveform generating circuit 26 generates and outputs a PWM signal 31 based on the operation command signal 30 based on the input of the operation command signal 30. Further, the waveform generating circuit 26 controls the inverter output duty so that the rotor of the electric motor 25 has a target rotation speed. Output variable. This PWM signal 31 is supplied to the rotor position detection circuit 2
8 is output to the pre-driver circuit 27 in synchronization with the position signal of FIG.
The power transistor 37 operates to obtain an AC having a desired frequency, and the motor 25 connected to the output of the inverter circuit 24 operates according to the operation command signal 30. The waveform generation circuit 26 is a general method of outputting an inverter drive signal 32 to the inverter circuit 24 so that the motor 25 is driven to match the operation command signal 30 and controlling the speed of the motor 25.

The pre-driver circuit 27 is a high-voltage IC
When (HVIC) is used and it is constituted by non-insulation,
The ground, which is the reference potential of the circuit mounted on the electronic device,
Generally, it is on the negative side of the smoothing capacitor 23. The negative power terminal 12 of the smoothing capacitor 23 and the inverter circuit 2
No. 4 pre-driver circuit 27b has a common ground between the grounds, and is originally at the same potential. If the distance between them is long, a large wiring inductance L occurs.

The switching speed of the power transistor 37 or the transistor 20 of the inverter circuit 24 is driven at a high speed in order to reduce loss, and the wiring inductance L and the steep current change (high di / dt) when the power transistor operates. ), A surge voltage is generated in the conductor pattern during this period. This voltage is unnecessary for the operation of the circuit, and causes noise and circuit malfunction.
In particular, the pre-driver circuit 27 driving the HVIC
May cause malfunction.

However, by arranging the ground of the inverter circuit 24 near the negative power terminal 12 of the smoothing capacitor 23 and shortening the conductor pattern 4, it is possible to minimize the surge voltage generated in this portion. Becomes possible,
Malfunction of the pre-driver circuit 27 or the power transistor 37 and a noise level generated by the device can be suppressed. In addition, by providing the waveform generation circuit 26, the pre-driver circuit 27, and the rotor position detection circuit 28 near each other, it is possible to reduce the voltage (generated noise) in the conductor pattern 4 due to the switching operation of the power transistor 37 or the transistor 20. , It is possible to reduce the influence of self-generated noise and the like.

Here, for the rotor position detecting circuit 28, for example, a method described in the prior art of Japanese Patent Application Laid-Open No. 8-182378 is generally known. That is, the position of the rotor can be known by comparing the reference potential obtained by dividing the voltage at both ends of the smoothing capacitor 23 by resistance and the signal obtained by dividing the output of the inverter circuit 24 by resistance at an arbitrary timing. Become. In addition, as a circuit configuration, there is a method of comparing the potential at which the other end of each resistor connected to the output of the inverter circuit 24 is connected at one place.

As described above, the resistor voltage dividing circuit (not shown) used for detecting the position of the rotor is connected to both ends of the smoothing capacitor 23 which is a high voltage circuit. It is mounted on the metal circuit board 1 as an element. Since the electronic component generating a large amount of heat is mounted on the metal circuit board 1 using the aluminum plate 2 having good thermal conductivity,
This heat is transmitted to the radiating fins 14 and radiated to the surroundings, thereby suppressing an increase in the temperature of the electronic components on the metal circuit board 1.

Between the pre-driver circuits 27a and 27b, there is a high-voltage section different from a low-voltage circuit such as a microcomputer constituting the waveform generation circuit 26. This high-voltage section is provided between the conductor patterns 4 to ensure insulation performance. Requires a large creepage distance. However, by mounting this high-voltage portion on the resin circuit board 9 and surrounding it with the resin case 16 and injecting and sealing a filler 15 such as silicon having a dielectric breakdown voltage performance sufficiently higher than that of air, the high-voltage portion is Even if the creeping distance between the conductor patterns 4 is the same as that of the low-voltage circuit, the insulation performance can be ensured.

Next, the manufacturing process of the electronic device will be described with reference to FIG. In the manufacture of the electronic device, first, the sub-board applies the solder 6 to the metal circuit board 1 (step 1a), mounts surface mounting electronic components such as power transistors and diodes (step 1b), and applies the applied solder. Is melted and cured (reflow soldering) (step 1c). Here, Step 1 is Step 1a to Step 1c.

On the other hand, the mother board is
The discrete and surface mount electronic components are mounted by an automatic insertion machine (step 2d), and odd-shaped electronic components which cannot be mounted by the automatic insertion machine are manually mounted (step 2e). Next, soldering is performed at a predetermined position in a solder bath (step 2f). Here, Step 2 is Step 2
d to step 2f.

Next, the sub-board assembled in step 1 and the mother board assembled in step 2 are inserted into the resin case 16 at predetermined positions of the resin case 16 from the same direction, respectively, and are fitted together. Fix together. (Step 3g). Thereafter, electrical wiring is performed by wire bonding between the exothermic element 7 and the pads 5 on the metal circuit board 1 and between the metal circuit board 1 and the pads 5 on the resin circuit board 9 with the bonding wires 8 (step 3h). Filler 15 is filled with bonding wire 8 in a range surrounded by metal circuit board 1, resin circuit board 9, and resin case 16.
Is injected (step 3i) and thermally cured in a thermostat (step 3j). Thereafter, an electronic device is completed through an inspection process. Here, step 3 is the above steps 3g to 3j.

For the filler 15 used in step 3i, heat is applied without damaging other electronic components by selecting thermosetting silicon that cures at 70 ° C. for 0.5 hour, for example. be able to. The board may be fixed to the resin case 16 by screws. In (Step 3h), electric wiring may be directly performed between the heat generating element 7 on the metal circuit board 1 and the pad 5 on the resin circuit board 9 by the bonding wire 8.

As described above, the inexpensive resin circuit board 9 is used for the material of the mother board, and only the heat generating element 7 is mounted on the metal circuit board 1. Therefore, the area of the expensive metal circuit board 1 is minimized. And the cost of the substrate can be reduced.
Further, in order to change the electric wiring in the metal circuit board 1, only the metal circuit board 1 needs to be redesigned and manufactured, and there is no need to redesign the resin circuit board 9. The same applies to the resin circuit board, and the design cost can be reduced. Further, by soldering the power terminals 12 and the signal terminals 13 simultaneously with other electronic components on the resin circuit board 9 and connecting the metal circuit board 1 and the resin circuit board 9 with inexpensive bonding wires 8, Unlike the conventional case, there is no need to eliminate the insert molding of the power terminal 12 and the signal terminal 13 into the resin case, or it is not necessary to solder the input / output terminal on the resin circuit board by retrofitting, which facilitates mounting. Material cost,
Manufacturing costs can be reduced.

Further, since the mother substrate and the sub-substrate are sealed with resin, insulation deterioration due to moisture absorption after dust adherence and stress on a wire bonding portion due to vibration can be reduced, thereby improving circuit reliability. Further, by encapsulating the wiring conductor pattern portion of the high-voltage circuit with resin, insulation can be ensured even when the distance between the wiring conductors 4 is reduced, so that the mounting area of the high-voltage circuit portion can be reduced and the board area can be reduced. It becomes possible.

Further, by shortening a path through which a rapidly changing current flows, such as the inverter circuit 24 and the transistor 20, and reducing the wiring inductance, it is possible to minimize the surge voltage generated due to the wiring inductance of the conductor pattern. This makes it possible to prevent the power transistor from operating due to a malfunction of the pre-driver circuit 27 or the waveform generation circuit 26, and to suppress the level of noise generated from the device, thereby improving the reliability of the electronic device and the mounted devices. I can do it. Further, the routing of the high voltage wiring can be minimized, the size of the substrate and the device can be reduced, and the cost can be reduced.

Since the rotor position detecting circuit 28 for detecting the rotor position of the motor 25 is mounted on the resin circuit board 9, the power terminal 12 on the resin circuit 9 board, which is the output of the inverter circuit 24, and the motor 25 are connected. Direct connection is possible, and the number of lead members for connecting to an external control board can be reduced. Further, a terminal block or the like on the substrate connected to the electronic device is not required, and the size of the substrate can be reduced.

The mounting of the mother board and the sub-board in the resin case is performed by inserting the mother board and the sub-board from the same direction into the resin case and fixing them by fitting. can do.

In the first embodiment, an example in which the electronic device is used for the inverter control device has been described. However, the present invention can be applied to a power control circuit device of a power application device such as an air conditioner and a fluorescent lamp.

Embodiment 2 FIG. 5 is a cross-sectional view illustrating a configuration of a resin case, a metal circuit board, a resin circuit board, and the like of an electronic device according to a second embodiment of the present invention, in which electronic components are omitted. 1 is mounted as well.
In the figure, reference numeral 16a is provided on the bottom surface of the resin case 16 and has an elastic fitting portion for fitting the metal circuit board 1;
Reference numeral 6b denotes a resilient fitting portion provided on the bottom surface of the resin case 16 and for fitting the resin circuit board 9 therein. When the metal circuit board 1 is attached to the fitting portion 16a from above the resin case 16 and pressed downward, the fitting portion 16a
Has elasticity, the metal circuit board 1 fits into the fitting portion 16a. The resin circuit board 9 is similarly fitted to the fitting portion 16b. The heat radiation fins 14 having a low height are used, and are attached to the lower portion of the metal circuit board 1 so as to be in close contact therewith (to cover the lower portion of the resin circuit board 9).

As described above, since the metal circuit board 1 and the resin circuit board 9 are inserted into the resin case 16 from the same direction and fitted and fixed, an adhesive for fixing each board to the resin case 16 is unnecessary. Becomes Further, since the substrates are inserted into the resin case 16 from the same direction, the structure is easily adapted to automation of assembly. Further, since the two substrates are not superposed and are arranged in a plane, and the radiation fins having a low height are used, the thickness can be reduced to 1/2 to 1/3 of the conventional circuit.

FIG. 6 is a sectional view of the electronic device having the thin structure shown in the third embodiment according to the present invention used in a control circuit of a refrigerator, viewed from the side of the refrigerator. In the figure, reference numeral 39 denotes a refrigerator, and reference numeral 40 denotes a control circuit storage unit that stores a control circuit of the refrigerator 39. Since the electronic device having a thin structure is used for the control circuit, the control circuit housing portion 40 can be made thinner, and a wide storage space can be secured even in a refrigerator having a thin structure.

In the second embodiment, an example in which the electronic device is used for a refrigerator has been described. However, the electronic device can be used for power application equipment such as an air conditioner and a fluorescent lamp.

[0056]

As described above, according to the present invention, the low heat-generating element and the input / output for inputting / outputting signals or power are provided on the sub-board having the heat-generating element mounted on the metal circuit board and the resin circuit board. A mother board having terminals mounted thereon, and connection means for electrically connecting the mother board and the sub-board,
Since the sub-substrate and the resin case for accommodating the mother substrate are provided, the connecting members and the structural members between the substrates can be simplified, the connecting members can be inexpensive such as wire bonding, and the reliability of the electronic circuit can be improved. The circuit size and cost can be reduced while ensuring the performance. In addition, since an inexpensive resin circuit board is used for the material of the mother board, and only the heat-generating elements are mounted on the metal circuit board, the area of the expensive metal circuit board can be minimized, and the cost of the board can be reduced. Becomes Further, when changing the electric wiring in the metal circuit board, only the metal circuit board needs to be redesigned and manufactured, and there is no need to redesign the resin circuit board. The same applies to the resin circuit board, and the design cost can be reduced. In addition, by soldering the input / output terminals simultaneously with other electronic components on the resin circuit board and connecting the metal circuit board and the resin circuit board with inexpensive connection means such as wire bonding, the conventional input / output terminals can be used. There is no need to abolish insert molding in the resin case, or to solder the input / output terminals on the resin circuit board by retrofitting, which facilitates mounting and reduces material and manufacturing costs. .

Further, since the mother substrate and the sub-substrate are sealed with resin, insulation deterioration due to moisture absorption after dust adheres and stress on the wire bonding portion due to vibration can be reduced, thereby improving circuit reliability. Further, by sealing the wiring conductor pattern portion of the high-voltage circuit with resin, insulation can be ensured even when the distance between the wiring conductor patterns is reduced, so that the mounting area of the high-voltage circuit portion can be reduced and the board area can be reduced. Become.

The input / output terminals on the mother board are composed of signal terminals for inputting / outputting signals and power terminals for inputting / outputting power. The power and signal terminals are provided on the resin circuit board by other electronic components. At the same time, it was soldered and the resin circuit board and the metal circuit board were connected by inexpensive connection means such as wire bonding, so the insert molding of the power and signal terminals into the resin case as in the past was eliminated, or There is no need to solder the power and signal terminals on the board by retrofitting, which makes mounting easier and reduces material costs,
Manufacturing costs can be reduced.

Further, since the mother board and the sub-board are arranged in a substantially planar shape in the resin case, and the low radiating fins are fixed to the lower portion of the sub-board, a product such as a refrigerator for mounting an electronic device can be used. The control circuit housing can be made thin. For this reason,
An electronic device that can secure a wide product storage space and can store more items, and that is easy to use and does not adversely affect products to be mounted can be obtained. Further, the cooling efficiency can be improved.

Further, the low heat generating element mounted on the mother board constitutes a waveform generating circuit for driving the heat generating element mounted on the sub-board and a pre-driver circuit.
The electronic components mounted on each circuit are arranged close to each other to minimize the surge voltage generated due to the wiring inductance of the conductor pattern and to make it less susceptible to external noise. This makes it possible to prevent the operation of the power transistor due to a malfunction of the pre-driver circuit or the waveform generation circuit and to suppress the level of noise generated from the device, thereby improving the reliability of the electronic device and the mounted device. Further, the routing of the high voltage wiring can be minimized, the size of the substrate and the device can be reduced, and the cost can be reduced.

Further, a voltage detecting circuit which is connected to the power terminal on the mother board and is constituted by a passive element and detects the voltage of the power terminal is provided, so that it is connected to an external control board. The number of lead members can be reduced. Further, a terminal block or the like on the substrate connected to the electronic device is not required, and the size of the substrate can be reduced.

Further, since the rotor position detecting circuit for detecting the rotor position of the motor is provided, it is possible to directly connect the power terminal on the resin circuit board, which is the output of the inverter circuit, to the motor, and to connect an external control board to the motor. Can be reduced. Further, a terminal block or the like on the substrate connected to the electronic device is not required, and the size of the substrate can be reduced.

The heat-generating element mounted on the sub-board is a power semiconductor element constituting a rectifier circuit for converting AC power from an AC power supply to DC and an inverter circuit for converting the DC to AC. Therefore, the electronic components mounted on each circuit are arranged close to each other, and the ground, which is the reference potential of these circuits, is arranged near the negative side of the smoothing capacitor. By reducing the wiring inductance by shortening the flowing path, it is possible to minimize the surge voltage generated due to the wiring inductance of the conductor pattern. As a result, the level of noise generated from the device can be suppressed, and the reliability of the electronic device and the mounted device can be improved. Further, the routing of the high voltage wiring can be minimized, the size of the substrate and the device can be reduced, and the cost can be reduced.

The step of mounting the low heat generating element and the input / output terminals on the mother board and performing the flow soldering, and the step of applying the solder on the sub-board and mounting the heat generating element on the solder and performing the reflow soldering Performing the steps of: mounting the mother board and the sub-board in a resin case, electrically connecting the heat-generating elements on the sub-board and the circuit, and electrically connecting the mother board and the circuit on the sub-board, Sealing, so that the input / output terminals are soldered on the resin circuit board simultaneously with other electronic components, and the metal circuit board and the resin circuit board are connected by inexpensive wire bonding such as aluminum wire. As a result, it is possible to eliminate the conventional insert molding of power and signal terminals into the resin case, or to eliminate the soldering process by attaching input / output terminals on the resin circuit board To become. As a result, it is possible to connect the boards with inexpensive components, and it becomes easy to mount the power terminals, so that material costs and manufacturing costs can be reduced.

In addition, the mounting of the mother board and the sub-board in the resin case is performed by inserting the mother board and the sub-board into the resin case from the same direction and fixing them by fitting. can do.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an electronic device according to an embodiment of the present invention.

FIG. 2 is a circuit block diagram of the electronic device shown in FIG.

3 is a circuit diagram of a high-voltage circuit unit of the electronic device shown in FIG.

FIG. 4 is a flowchart illustrating a manufacturing procedure of the electronic device.

FIG. 5 is a sectional view showing another electronic device according to the embodiment of the present invention.

FIG. 6 is a cross-sectional view of the refrigerator as viewed from the side.

FIG. 7 is a cross-sectional view illustrating a conventional electronic device.

FIG. 8 is a sectional view of a conventional electronic device in which a metal circuit board is mounted on a resin case.

FIG. 9 is a cross-sectional view of a conventional electronic device in which a metal circuit board is mounted on a resin case.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 metal circuit board, 7 heat generating element, 8 bonding wire, 9 resin circuit board, 11 low heat generating element, 12
Power terminal, 14 Radiation fin, 15 Filler, 16
Resin case, 18 full-wave rectifier circuit, 24 inverter circuit, 26 waveform generation circuit, 27 pre-driver circuit, 28 rotor position detection circuit, 29 bus voltage detection circuit.

Claims (10)

[Claims] 1. A sub-board on which a heat generating element is mounted on a metal circuit board; a mother board on which a low heat generating element and input / output terminals for inputting / outputting signals or power are mounted on a resin circuit board; An electronic device, comprising: a connecting means for electrically connecting the sub-boards; and a resin case for housing the sub-boards and the mother board. 2. The electronic device according to claim 1, wherein the mother board and the sub-board are resin-sealed. 3. The electronic device according to claim 1, wherein the input / output terminals on the mother board include a signal terminal for inputting / outputting a signal and a power terminal for inputting / outputting power. 4. A substrate according to claim 1, wherein said mother substrate and said sub-substrate are disposed in a substantially planar shape in a resin case, and said heat-radiating fin having a low height is fixed to a lower portion of said sub-substrate. 4. The electronic device according to any one of 3. 5. The low heat generating element mounted on the mother board constitutes a waveform generating circuit for driving the heat generating element mounted on the sub-board and a pre-driver circuit. The electronic device according to claim 4. 6. The power supply terminal according to claim 5, further comprising a voltage detecting circuit connected to the power terminal on the mother board, configured by a passive element, and detecting a voltage of the power terminal. Electronic device for inverter control. 7. The electronic device for inverter control according to claim 5, further comprising a rotor position detection circuit for detecting a rotor position of the electric motor. 8. The heat-generating element mounted on the sub-board is a power semiconductor element constituting a rectifier circuit for converting AC power from an AC power supply to DC and an inverter circuit for converting the DC to AC. The electronic device for controlling an inverter according to claim 1, wherein: 9. A step of mounting a low heat generating element and an input / output terminal on a mother board and performing flow soldering, and after applying solder to the sub-board, mounting the heat generating element on the solder and performing reflow soldering. Performing the steps of: mounting the mother board and the sub-board in a resin case;
Electrically connecting between the heat-generating element on the sub-substrate and the circuit and between the mother substrate and the circuit on the sub-substrate and sealing with resin. . 10. The mounting of the mother board and the sub-board on the resin case is performed by mounting the mother board and the sub-board from the same direction.
The method for manufacturing an electronic device according to claim 9, wherein the electronic device is inserted into a resin case and fixed by fitting.