JPS62209888A - Insulating board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a metal-based insulating plate used for ICs, power transistors, etc. The present invention relates to an insulating plate having peeling resistance.

[Conventional technology] Conventionally, epoxy resin plates, alumina ceramic plates, etc. have been widely used as substrates for mounting electronic components.
f-1, ks There is a risk that the temperature will rise and damage the functions of ICs, etc. And this problem is I
This problem is becoming increasingly serious as C components become more highly integrated, and there is an urgent need to improve the heat dissipation properties of substrate materials. Under these circumstances, substrates with excellent heat dissipation properties are being developed, and are made by laminating a thin insulating film on a metal plate with excellent thermal conductivity, bonding copper foil on top of it, and then bonding copper foil on top of it. A so-called metal base substrate on which a circuit pattern is formed by etching has been proposed, and its practical use is progressing.

By the way, glass, epoxy resin, or polyimide resin is generally used as the insulating film for the above-mentioned metal base substrate, but although these insulating materials have excellent voltage resistance, they have low thermal conductivity. However, the heat dissipation performance is still low. That is, at present, even if the thickness of the insulating layer is reduced to the minimum thickness that can guarantee the required withstand voltage characteristics, its heat dissipation performance has not yet reached a satisfactory level.

Therefore, in order to further improve the heat dissipation properties of the metal base substrate, the insulating layer was made of alumina ceramics (Al1.03).
Attempts have been made to form a thermally sprayed layer. This A
The 12O3 sprayed layer has good voltage resistance and excellent heat dissipation, and can be used for parts such as power transistors that generate a large amount of heat.

[Problems to be Solved by the Invention] However, the Al2O3 insulating layer formed by thermal spraying has low toughness and may crack even if the substrate is slightly deformed. Furthermore, when soldering wires, etc. to a metal base substrate with an Al2O3 sprayed layer applied as an insulating layer, the substrate is heated to 250 to 350°C, but due to the deformation of such soldering, the substrate is exposed to the heat of heating and cooling. This causes cracks in the Al2O3 sprayed layer or peeling of the Al2O3 sprayed layer from the metal plate.

In addition to the method of forming the circuit pattern by etching the copper foil adhered onto the Al2O3 sprayed layer, there are also methods for forming the circuit pattern.
3. There is a method of forming a circuit pattern by screen printing a conductive paste on the sprayed layer and baking it. The firing temperature at this time reaches a maximum of 900 to 1000°C, and At20. In the case of a thermally sprayed layer, everything will peel off.

As described above, metal base substrates using an Al2O3 sprayed layer as an insulating layer have problems such as cracking and peeling of the sprayed layer, and a satisfactory metal base substrate, particularly an insulating plate for configuring electronic components, has not yet been provided.

The present invention has been made in view of these circumstances, and it is an object of the present invention to provide an insulating board that has excellent heat dissipation properties and voltage resistance, as well as high toughness and peeling resistance.

[Means for Solving the Problems] The insulating plate of the present invention that achieves the above object has a gist in that a thin MgO film is formed as an insulating layer on a metal substrate.

[Function] Ensuring high heat dissipation as well as voltage resistance are essential conditions for an insulating board for electronic components.

In other words, the recent trend toward higher integration is accelerating.
To combat this trend, it is necessary to increase integration without causing heat buildup. Therefore, in order to ensure a high degree of heat dissipation, it is necessary to use a metal plate with high thermal conductivity as the base plate of the insulating plate. The type of such metal plate is not particularly limited, and various metal plates and alloy plates can be used, but typical examples include mild steel plates and AI plates.

Next, as an insulating layer integrally formed on the metal plate,
Since the metal plate is a conductor, it is necessary to create an electrically disconnected state between the metal plate and the printed circuit pattern, and the electrically disconnected state must be ensured to withstand a considerable voltage difference. That is, the insulating layer must have considerable voltage resistance and must be able to quickly conduct heat generated from the printed circuit portion to the metal plate side and dissipate the heat. The present inventors have searched for various substances having such characteristics, and selected the above-mentioned Al.
An MgO thin film has been discovered as a material that has higher toughness than a 2O3 sprayed layer and also has excellent peeling resistance due to thermal cycles. It was also found that the MgO thin film has superior voltage resistance properties and heat dissipation properties over the Al2O3 sprayed layer.

There are several types of MgO thin films depending on the formation method, and typical examples include thermal sprayed films and vapor deposited films. Among thermal sprayed films, films formed by low-pressure plasma spraying are more preferable because they have a small porosity within the film and are excellent in thermal conductivity, that is, heat dissipation, as well as high toughness and peeling resistance. be able to. In the present invention, there is no particular restriction on the thickness of the MgO thin film, but a thickness of 50 to 500 μm is recommended in order to satisfy the required characteristics. In other words, if the film thickness is less than 50 μm, the withstand voltage characteristics may fall below the specified value because it is too thin. On the other hand, if the film thickness exceeds 500 μm, heat transfer resistance will increase, heat dissipation will deteriorate, and processing will be difficult. Resistance increases, making cracking and peeling more likely.

The insulating plate of the present invention is formed by forming a MgO thin film on a metal plate as described above, and by printing a circuit pattern on this, a metal base substrate for forming electronic components such as ICs and power transistors can be obtained. I can do it.

[Example Example 1 Al2O3 powder with a particle size of 44 μm and Mg were placed on a mild steel substrate.
Insulating layers each having a thickness of 200 μm were formed by plasma spraying O powder. Table 1 shows the results of these three-point bending tests.

Further, a 1 cm2 metal piece was adhered to the surface of the Al2O3 layer and MgO layer obtained above, and with the substrate fixed, a tensile force was applied to the metal piece to measure the peel strength of each layer. The results are shown in Table 2.

From Tables 1 and 2, it was found that the MgO sprayed layer had excellent toughness and peeling resistance.

Table 1 Table 2 Example 2 Al2O3 powder with a particle size of 44 μm and Mg on an AI substrate
Plasma spray O powder under reduced pressure of 150 mbar,
An Al2O3 layer and a MgO layer were each formed to a thickness of 200 μm, and a 35 μm thick electrolytic copper foil was further bonded and a circuit pattern was formed by etching, and then a characteristic test was conducted.

Table 3 shows the respective withstand voltages. Furthermore, a chip resistor was soldered onto the substrate, and the supplied power and the temperature of the chip resistor were measured. The results are shown in FIG.

From these results, it was found that the MgO layer is excellent in both withstand voltage and heat dissipation properties.

Table 3 [Effects of the Invention] The present invention is configured as described above, and can provide an insulating board that is excellent in voltage resistance, heat dissipation, toughness, and peeling resistance. In this way, it is possible to obtain electronic components such as high-performance ICs and power transistors that are compatible with high-level integration.

[Brief explanation of drawings]

FIG. 1 is a graph showing the results of comparing the heat dissipation performance of the MgQ sprayed film and the Al2O3 sprayed film.

Claims (3)

[Claims] (1) An insulating plate characterized in that a thin MgO film is formed as an insulating layer on a metal substrate. (2) The insulating plate according to claim 1, wherein the MgO thin film is formed by a thermal spraying method. (3) The insulating plate according to claim 2, wherein the thermal spraying method is low pressure plasma spraying.