JPH05292744A - Mounting structure for power supply module - Google Patents

Abstract

PURPOSE:To provide a mounting structure of a power supply module for inverting DC voltage through a transistor into high frequency voltage which is then subjected to step-down and rectification to produce a low DC voltage wherein cooling performance is enhanced and propagation of noise is suppressed. CONSTITUTION:The mounting structure of power supply module comprises a metal base printed board 30 mounting a transistor 10 with the package conductor part 11 thereof being connected tightly with a pad 35 formed on an insulation layer 32, I/O terminals 38 planted on the mounting surface of the metal base printed board 30, and a mother printed board 50 having a surface mounted with circuit components such as a transformer and rectifier elements. The metal base printed board 30 is then mounted on the mother printed board 50 with the I/O terminals 38 being connected, at the ends thereof, with the mother printed board 50.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mounting structure of a power supply module which converts direct current into a high frequency by a transistor, steps down and rectifies and outputs low voltage direct current.

Many power supply modules for supplying low-voltage direct current to electronic devices have a circuit configuration shown in FIG. Figure 2
As shown in the figure, 48V DC is input to the transistor
It is converted into a high frequency at 10 and is stepped down by the transformer 2 and further rectified by a rectifying circuit in which the diode 3, the coil L and the capacitor C are combined in a desired manner to output a low voltage DC of 5V or 12V.

For such a power supply module, there is a demand for a mounting structure in which the heat dissipation of the components, especially the transistor, is good.

[0004]

2. Description of the Related Art FIG. 3 is a sectional view showing a mounting structure of a conventional power supply module. In FIG. 3, reference numeral 10 denotes a transistor whose bottom is packaged by the package conductor portion 11 and whose upper portion is packaged by the package insulating portion 12.

The collector of the transistor 10 is connected to the package conductor portion 11, the base and the emitter are connected to the leads, respectively, and led out from the side wall of the package insulating portion 12 to the outside of the package.

Reference numeral 20 denotes a metal base printed board on which an insulating layer 22 is formed on the surface of a metal plate 21 such as aluminum, and a pad 25 for mounting and soldering the transistor 10 and other conductor patterns are formed on the insulating layer 22. is there.

The package conductor 11 is aligned and placed on the pad 25 of the metal base printed board 20 and soldered, and the leads connected to the base and the emitter are bent into a substantially Z shape, and formed on the surface of the insulating layer 22. The transistor 10 is mounted on the metal base printed board 20 by soldering to a conductor pattern.

In addition to the above, the metal base printed board 20 includes a transformer for stepping down the power source converted to high frequency by the transistor 10, a diode, a capacitor, a coil which is a rectifying circuit constituent element, and constituent elements constituting other circuits. The circuit component 5 is mounted.

Since the transistor 10 is mounted on the metal base printed board 20 as described above, most of the heat of the transistor 10 passes through the package conductor portion 11 and the insulating layer 22 of the metal base printed board 20, and the metal plate 21. To the outside through the metal plate 21.

Therefore, the transistor 10 does not reach a temperature higher than a predetermined temperature.

[0011]

By the way, a high pulse voltage is applied to the transistor. On the other hand, the package conductor portion (collector) of the transistor is in close contact with the pad, and the pad faces the metal plate of the metal base printed board via the insulating layer.

Therefore, a capacitance is generated between the pad of the metal base printed board and the metal plate. As a result, there is a problem in that the metal plate serves as an antenna and the noise propagates to other circuit components mounted on the metal base printed board.

The present invention has been made in view of the above points, and an object thereof is to provide a mounting structure of a power supply module, which has a good cooling performance and suppresses the propagation of noise.

[0014]

In order to achieve the above object, the present invention, as shown in FIG. 1, converts a direct current into a high frequency by a transistor, steps down and rectifies it, and outputs a low voltage direct current. In the module, the package conductor portion 11 of the transistor 1 is in close contact with and connected to the pad 35 formed on the surface of the insulating layer 32, and the transistor 1 is mounted on the metal base printed board 30.

Further, the input / output terminals 38 are provided in a mounted state on the mounting surface of the metal base printed board 30. On the other hand, a transformer, a rectifying circuit element and other circuit parts are mounted on the mother printed board 50.

Then, the metal base printed board 30 is layered with the metal plate 31 on the upper side, and the tips of the input / output terminals 38 are connected to the mother printed board 50, so that the metal base printed board 30 is attached to the mother printed board 50. It is configured to be installed.

Alternatively, the metal base printed board 30 is sealed with the synthetic resin 60 while being mounted on the mother printed board 50.

[0018]

According to the present invention, only the transistor is mounted on the metal base printed board, and the metal plate of the metal base printed board is electromagnetically separated from the mother printed board. Therefore, even if a high pulse voltage is applied to the transistor and a capacitance is generated between the pad of the metal base printed board and the metal plate, the metal plate of the metal base printed board does not act as an antenna. That is, no noise is added to the circuit components mounted on the mother printed board.

Further, since the heat of the transistor is transferred to the metal plate of the metal base printed board and is radiated to the outside from the surface of the metal plate 31, the heat dissipation of the transistor is good.
On the other hand, the thermal conductivity of synthetic resin is higher than that of air. Therefore, after mounting the metal base printed board on the mother printed board and sealing it with the synthetic resin, the heat of the transistor is transferred to the metal base printed board, and further transferred to the synthetic resin, so that a large area surface of the synthetic resin is transferred. It is released to the outside and transmitted to the mother printed board,
It is also released from the mother printed board.

Therefore, the heat dissipation of the transistor is further improved.

[0021]

The present invention will be described in detail with reference to the drawings. The same reference numerals denote the same objects throughout the drawings.

FIG. 1 is a sectional view of an embodiment of the present invention. The transistor 10 has the bottom packaged by the package conductor section 11 and the upper section packaged by the package insulation section 12, the collector connected to the package conductor section 11, the base and the emitter respectively connected to the lead, and the package insulation section. It is led out of the package from 12 side walls.

Reference numeral 30 denotes a strip-shaped metal base in which an insulating layer 32 is formed on the surface of a metal plate 31 such as aluminum, and a pad 35 for mounting and soldering the transistor 10 and other conductive patterns are formed on the insulating layer 22. It is a printed board.

The package conductor portion 11 is aligned and placed on the pad 35 of the metal base printed board 30 and soldered, and the leads connected to the base and the emitter are bent into a substantially Z shape and formed on the surface of the insulating layer 32. The transistor 10 is mounted on the metal base printed board 30 by soldering to a conductor pattern.

Further, on the mounting surface of the metal base printed board 30, input / output terminals 38 are provided in a standing state. 50 is
On the surface of a metal plate 51 such as a sufficiently wide square aluminum,
It is a mother printed board made of a metal base printed board on which an insulating layer 52 is formed.

The mother printed board 50 is provided with pads for soldering the tip portions of the input / output terminals 38 corresponding to the input / output terminals 38 of the metal base printed board 30, and a conductor pattern passing therethrough is provided. It is provided.

Further, on the mother printed board 50, circuits such as a transformer for stepping down the power source converted to a high frequency by the transistor 10 and a diode, a capacitor, a coil which are rectifying circuit constituent elements, and constituent elements constituting other circuits are provided. The component 5 is mounted.

Then, with the metal plate 31 on the upper side, the input / output terminals are
With the 38 as the mother printed board 50 side, the metal base printed board 30 is layered on the mother printed board 50, and the tips of the input / output terminals 38 are soldered to the corresponding pads of the mother printed board 50 to create a metal base. The printed board 30 is mounted on the mother printed board 50.

Then, as described above, the metal base printed board
After mounting 30 on the mother printed board 50, the metal base printed board 30 side is inserted into a box-shaped mold with an upper opening, and the mounting surface of the mother printed board 50 is pressed against the opening surface of the molding die. By injecting and filling the synthetic resin 60 into the molding die in this state, all of the metal base printed board 30, the transistor 10 and the input / output terminals 38 are sealed to the mother printed board 50 with the synthetic resin 60.

Therefore, even if a high pulse voltage is applied to the transistor 10 and a capacitance is generated between the pad 35 and the metal plate 31 of the metal base printed board 30, noise is generated in the circuit component 5 mounted on the mother printed board 50. I don't ride.

On the other hand, the heat of the transistor 10 is transferred to the metal plate 31 of the metal base printed board 30 and further transferred to the synthetic resin 60, and is radiated to the outside from the wide area surface of the synthetic resin 60. In addition, a part of the heat transferred to the synthetic resin 60 is transferred to the mother printed board 50, and the metal plate of the mother printed board 50.
It is released from 51 to the outside.

Therefore, the heat dissipation of the transistor 10 is good. The mother printed board is not limited to the metal base printed board, and a laminated printed board such as glass epoxy resin or a ceramic printed board has substantially the same cooling effect.

On the other hand, a synthetic resin 60 is used for the metal base printed board.
Since 30 etc. are sealed, the input / output terminals 38 etc. do not fall. Therefore, not only the transistor, the metal base printed board, etc. are protected, but also the reliability of the connection between the pad of the metal base printed board and the input / output terminal and between the input / output terminal and the pad of the mother printed board is high.

[0034]

As described above, according to the present invention, only the transistor, which is a semiconductor component for applying a pulsed high voltage, is mounted on a metal base printed board, and the metal base printed board is used as another constituent element constituting a power supply module. That is, the mounting structure of the power supply module is mounted on the mother printed board 50 in which the transformer, the rectifying circuit constituent elements, and the constituent elements of other circuits are mounted on the mother printed board with the metal plate facing upward. Not only does it have good cooling performance, but it also has a practically excellent effect that noise is not placed on the circuit components mounted on the mother printed board.

The one in which the metal base printed board is sealed to the mother printed board with the synthetic resin not only protects the transistor and the metal base printed board, but also between the pad and the input / output terminals of the metal base printed board and the input. The reliability of the connection between the output terminal and the pad of the mother printed board is high.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention.

[Figure 2] Circuit diagram of power supply module

FIG. 3 is a sectional view of a conventional example.

[Explanation of symbols]

 2 Transformer 3 Diode 5 Circuit parts 10 Transistor 11 Package conductor part 12 Package insulating part 20,30 Metal base printed board 21,31,51 Metal plate 22,32,52 Insulation layer 25,35 Pad 38 Input / output terminal 50 Mother printed board 60 synthetic resin

Claims (2)

[Claims] 1. A direct current is converted into a high frequency by a transistor,
In a power supply module for stepping down and rectifying and outputting a low voltage direct current, a metal in which the transistor 1 is mounted by closely connecting the package conductor portion 11 of the transistor 1 to a pad 35 formed on the surface of the insulating layer 32. A base printed board 30; an input / output terminal 38 erected on a mounting surface of the metal base printed board 30; and a mother printed board 50 having a circuit component 5 such as a transformer and a rectifying device mounted on the surface thereof. The input / output terminals 38 are connected at their tips to the mother printed board 50, and the metal base printed board 30 is mounted on the mother printed board 50 in a state in which the metal plate 31 is stacked on the upper side. Power module mounting structure. 2. The mounting structure of a power supply module according to claim 1, wherein the metal base printed board 30 is sealed with a synthetic resin 60 while being mounted on the mother printed board 50.