JPH03252190A - Metal printed board - Google Patents

Abstract

PURPOSE:To largely reduce a stray capacity without disturbing heat conduction and to effectively suppress leakage of a signal, invasion of noise by forming a groove on a metal plate part opposed to a conductor circuit. CONSTITUTION:A groove 7 of substantially the same flat surface shape as a circuit is formed in depth t2 and width w2 on a surface of a metal plate 1 opposed to a conductor circuit 3. In this case, the w2 is set to a value larger than the width w1 of the circuit 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a metal printed board used in power conversion devices such as inverters.

[Conventional technology]

A metal printed board has an advantage over a typical glass epoxy resin board in that the heat generated by the components mounted on it can be dissipated into the package. On the other hand, metal printed boards have the disadvantage that signals tend to leak and noise easily infiltrates because the stray capacitance generated between the metal plate and the conductor circuit is large.

FIG. 3 is a sectional view showing the general structure of a conventional metal printed board. In this figure, 1 is a metal plate and 2 is an insulating plate. This insulating plate 2 is usually bonded to the metal plate 1. 3 is a conductor circuit, which is adhesively formed on the insulating plate 2. 4 is an electronic component attached to the conductor circuit 3 with solder 5 or the like. 6 is a symbol representing the stray capacitance formed between the insulating plate 2 and the metal plate 1.

Most of the heat generated in the electronic component 4 is dissipated in the direction of the arrow 8. The quality of heat conduction at this time is determined by the thickness tl of the insulating plate 2.
The thinner it is, the better it is, so in general, after considering the withstand strength against the voltage applied between the conductor circuit 3 and the metal plate 1,
The thickness t is formed as thin as possible.

On the other hand, the stray capacitance 6 causes signal leakage between circuits, and also causes noise to infiltrate from the outside through the metal plate 1 as shown by the arrow 9, for example. As a countermeasure for this, insulating plate 2
It is possible to increase the thickness tl, but this will result in poor conduction of heat, resulting in a problem with heat dissipation.

[Problem to be solved by the invention]

Therefore, the problem to be solved by the present invention is to reduce the stray capacitance between the conductor circuit and the metal plate while avoiding the problem of heat dissipation in the metal printed board as described above.

[Means to solve the problem]

According to the present invention, the above problem is solved by forming a groove in the portion of the metal plate facing the conductor circuit in a metal printed board in which a conductor circuit is formed on the surface of an insulating plate placed on a metal plate. Ru.

[Operation] According to the above-mentioned solution, most of the heat generated in the electronic component flows through the solder part, through the insulating plate directly below, and to the metal plate, so even if there are grooves, heat conduction is not significantly inhibited. On the other hand, the stray capacitance between the conductive circuit and the metal plate is significantly reduced by forming the grooves in the metal plate, so that signal leakage and noise infiltration are effectively suppressed.

〔Example〕

1 and 2 show an embodiment of the present invention, with FIG. 1 being a sectional view and FIG. 2 being a partial top view. In these figures, 1 is a metal plate, and 2 is an insulating plate, which is usually bonded to the metal plate 1. 3 is a conductor circuit formed on the insulating plate 2 by adhesive. 4 is an electronic component attached to the conductor circuit 3 with solder 5 or the like. 6 is a symbol representing the stray capacitance formed between the insulating plate 2 and the metal plate 1.

The difference from the conventional example shown in FIG. 3 is that the conductor circuit 2 of the metal plate 1
A groove 7 having almost the same shape as the circuit is formed at a depth t2 on the surface facing the circuit.
This is a point formed with a width w2. In this case, by setting W2 to be larger than the conductor circuit width w, electric field concentration occurring between the corner of the groove edge and the conductor circuit portion can be avoided, and an increase in t2 can be prevented.

With such a structure, a metal printed board with low stray capacitance can be realized without impeding heat conduction. In other words, most of the heat generated in the electronic component 4 is caused by the solder 5.
Since the heat flows through the insulating plate 2 immediately below and to the metal plate through the groove 7, heat conduction is not hindered much even if there is the groove 7. On the other hand, since the stray capacitance is significantly reduced by forming the groove 7, signal leakage and noise infiltration can be effectively suppressed. Furthermore, the formation of the grooves improves the adhesive strength with the insulating plate, resulting in a metal printed board that is resistant to heat cycles.

Of course, the present invention is effective even when the metal plate 1 and the insulating plate 2 are not bonded together.

[Effects of the Invention] As described above, according to the present invention, by forming grooves in the metal plate portion facing the conductor circuit, stray capacitance can be significantly reduced without impeding heat conduction. Signal leakage and noise intrusion can be effectively suppressed.

[Brief explanation of drawings]

Fig. 1 is a schematic cross-sectional view showing an embodiment of the metal printed board according to the present invention, Fig. 2 is a partial top view of the embodiment of the metal printed board of Fig. 1, and Fig. 3 is an example of a conventional metal printed board. FIG. 1... Metal plate, 2... Insulating plate, 3... Conductor circuit,
4...Electronic component, 5...Solder, 6...Stray capacitance, 7...Groove.

Claims (1)

[Scope of Claims] 1) A metal printed board in which a conductor circuit is formed on the surface of an insulating plate placed on a metal plate, characterized in that a groove is formed in the part of the metal plate facing the conductor circuit. printed board. 2) The metal printed board according to claim 1, wherein each of the grooves has substantially the same planar shape as the conductor circuit portion facing each other. 3) The metal printed board according to claim 2, wherein the width of the groove is larger than the width of the conductor circuit portions facing each other.