JPS59224192A - High heat conductive metal base printed circuit 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 Field of Industrial Application The present invention relates to a wiring board for a highly thermally conductive metal base 1 with good thermal conductivity used in electronic equipment.

Conventional configurations and their problems In recent years, the electronic equipment field has been trending towards miniaturization and use of pumice, and it is becoming increasingly difficult to dissipate heat from high-heating components such as ICs, MS I, LSI, power transistors, and arrange them in high density. (Implementation) has become a major issue.

Conventionally, organic polymer materials such as paper-based phenolic resin laminates or glass-based epoxy resin laminates, and ceramic materials such as alumina substrates have been used as substrate materials for printed wiring boards. However, because of their low thermal conductivity and insufficient heat dissipation, it was not possible to mount high-heat generating components such as ICs, MSIs, LSIs, and power transistors in a high density.

Therefore, highly thermally conductive metal-based printed wiring boards have been developed that are based on metals with excellent thermal conductivity, heat resistance, and mechanical strength. This conventional high thermal conductive metal-based printed wiring board is made of an organic polymer material from the material of the insulating layer. The former is the mainstream, while the latter is in the development stage. Such a conventional high thermal conductivity metal base printed wiring board 1 will be explained with reference to FIGS. 1 and 2. Figure 1 is a cross-sectional view of a conventional high thermal conductive metal base copper clad plate processed into a conventional high thermal conductive metal base pudding 1 to wiring board, and Figure 2 is a cross sectional view of a high thermal conductive metal base copper clad plate processed into a wiring board. Conventional high thermal conductivity metal base printer 1 - A cross-sectional view of a state in which electronic components including high heat generation components are mounted on a wiring board, 1 is a metal base, 2
is an insulating layer, 3 is a copper foil, 4 is a high heat generation component, 5 is an electronic component,
6a.

6b is a solder layer, 7 is silicone grease, and 8 is a heat radiation fin. A wiring circuit is formed by etching etc. on a highly thermally conductive metal base copper clad plate (Fig. 1) in which a metal base 1 and a copper foil 3 are bonded together via an insulating layer 2, and a wiring circuit is formed on it as shown in Fig. 2. , ICs, MSIs, LSIs, power transistors, and other semiconductor high heat generating components 4 and electronic components 5 such as capacitors, resistors, diodes, transistors, etc. are arranged adjacent to each other with high density, and solder layers 5a and 6b are connected to copper foil. It is connected to 3. Furthermore, a heat dissipation fin 8 is attached to the lower surface of the metal base 1 via silicone grease 7 (dC type). In FIG. The heat is dissipated by conduction in the vertical direction to the copper foil 3.However, the heat dissipation by conduction is so large that the heat dissipation by convection and radiation can be ignored.For this reason, in order to improve the heat dissipation characteristics of the high heat generation component 4, it is necessary to solder It is necessary to reduce the thermal resistance from the layer 6a to the silicone grease 7.In addition, regarding the heat dissipation fin 8, it is determined by the calorific value of the high heat generation component 4 and the cumulative thermal resistance up to the silicone grease 7. or use heat dissipation fins,
Conversely, it becomes possible to use small heat dissipation fins with high thermal resistance. That is, let us assume that the amount of heat generated when a load is applied to the high heat generating component 4 is pc (W), the allowable temperature of the high heat generating component 4 at that time is Tj (oC), the ambient temperature is Ta (・OC),
The thermal resistance of the semicircular layer 6a is Rthi, and the thermal resistance of the copper foil 3 is eR.
th2, thermal resistance of insulating layer 2 is Rtb3, thermal resistance of metal base 1 is Rtl)4, thermal resistance of silicone grease 7 is 1
(1115, if the thermal resistance of the radiation fin 8 is Rtb6, there is a total thermal resistance Rt1) - 2n, and between the thermal resistances Rth1 to Rtl+6 of each component c, Rth=R
th1+Rth2 +l'(th3 +Rtb4-Jt
There is a relationship of h5 +Rth6. Here, high heat generation component 4
When the 0 calorific value pc, the allowable temperature Tj, and the ambient temperature Ta are constant (that is, Rtb-constant), the thermal resistance Rth6 that determines the size and volume of the radiation fins 8 is the thermal resistance of the other solder layer 6a. It is determined by the total thermal resistance from RL111 to the thermal resistance Rth5 of the silicone grease 7. If it is small, the thermal resistance Rth6 of the radiation fin 8 will be too large (that is, a small radiation fin), and if it is too large (the thermal resistance Rth6 will be too small), For example, a heat dissipation fin 8 with a small thermal resistance Rthe (ie, a large heat dissipation fin or a heat dissipation fin with a forced cooling part) is selected. The insulating layer 2 is made of an organic polymer material such as epoxy, and is usually formed to have a thickness of 30 .mu.II to 60 .mu.m from the viewpoint of reliability, dielectric breakdown voltage, thermal conductivity, etc. In addition, the material of the metal base 1 is aluminum,
For the semi-[1,1 layer 6a, eutectic solder of lead and tin is used °C
There is. When looking at the conventional highly thermally conductive metal base print 1 to wiring board, the thermal resistance Rth3 accounted for by the insulating layer 2 is 90% or more of the thermal resistances Rth1 to Rths. Furthermore, in order to improve heat dissipation (and thereby increase the power of the high heat generation component 4) and to reduce the size and weight of the heat dissipation fins 8, it is most efficient to reduce the thermal resistance of the insulating layer 2. It's a method.

In order to improve heat dissipation, a highly thermally conductive material in which a metal oxide is dispersed in an adhesive organic polymer has been put into practical use as the material 1 for the insulating layer 2, as described above. It's coming. However, when the insulating layer 2 is formed only with this highly thermally conductive material, the thermal resistance of the insulating layer 2 can be reduced by more than 50% compared to that formed only with an organic polymer material, and the high heat generation component 4 Although it is possible to improve the power of the heat dissipation fins 8 and to make the heat dissipation fins 8 smaller and more hanging, there are limits to this. In other words, increasing the thermal conductivity of the insulating layer 2 also raises the temperature of other electronic components 5 mounted adjacent to the high heat generating component 4 through the highly thermally conductive insulating layer 2. A problem arises from the reliability of the electronic component 5. Therefore, when a highly thermally conductive material is used as the insulating layer 2, it becomes possible to use a heat generating component 4 with a large power, but the thermal influence on the electronic component 5 becomes large, and the high thermally conductive metal base material This means that high-density mounting on the l-wiring board is only possible. On the other hand, if high-density packaging is attempted, there is a problem in that even if there is heat dissipation ability, it is not possible to use high heat generation components 4 with extremely large power.

Purpose of the Invention The present invention solves the above-mentioned drawbacks of the conventional technology.It is an object of the present invention to solve the above-mentioned drawbacks of the conventional technology. The purpose of the present invention is to provide a metal-based printed wiring board with high thermal conductivity.

Structure of the Invention In order to achieve the above object, the highly thermally conductive metal-based printed wiring board of the present invention comprises a metal base, an insulation layer laminated on the metal base, and a conductor laminated on the insulating layer. The insulating layer has a structure in which an insulating layer made of a low thermal conductive material and an insulating layer made of a high thermal conductive material are selectively arranged.

DESCRIPTION OF EMBODIMENTS Below, an embodiment of the present invention will be described based on the drawings.

Figure 3 is a cross-sectional view of a highly thermally conductive metal-based copper clad board used for a high thermally conductive metal-based printed wiring board, and Figure 4 is a high thermal conductive metal-based copper clad board with wiring processed as shown in Figure 3. FIG. 2 is a cross-sectional view of a state in which electronic components are mounted on a metal-based printed wiring board, in which the same components as those shown in FIGS. 1 and 2 are given the same reference numerals.

In FIG. 3, 1 is a metal base, 3 is a copper foil, 9 is an insulating layer with low thermal conductivity, and 10 is an insulating layer with high thermal conductivity, and as an insulating layer interposed between the metal base 1 and the copper foil 3, A low thermal conductivity insulating layer 9 and a high thermal conductivity insulating layer 10 are formed on the same plane. In Figure 4, 4 is a high heat generation component, 5
is an electronic component, 5a.

6 b is a solder layer, 7 is silicone grease, and 8 is a heat dissipation fin, all of which are made in parentheses in the same manner as in the past. IC
, MSI, LSI, power transistor, etc., the insulation layer located below the high heat generation components 4 is protected by the high thermal conductivity insulation layer 10 and receives excessive heat from the high heat generation components 4. Electronic components that are difficult to find 5 (e.g. chip resistors, chip capacitors, diodes, transistors, etc.)
The insulating layer located below is constituted by the low thermal conductivity insulating layer 9. As a result, the heat from the high heat generation components 4 is reduced to a high thermal conductivity insulation figure 10 with low thermal resistance.
It flows in the vertical direction from the to the heat dissipation fins 8, and in the horizontal direction from the high thermal conductivity insulating layer 10 to the low thermal conductivity insulating layer 9.
As a result, the flowing heat is significantly reduced, and the electronic component 5 is prevented from being overheated by the heat from the high heat generation component 4.

Next, an example of a method for manufacturing the highly thermally conductive metal-based printed wiring board will be described. First, a pattern design is performed by setting the portion on which the high heat generating component 4 will be mounted and covered.

A metal base, a metal base, Coating is performed on the base 1 using a bar coater, roll coater, screen printing, etc. Next, as a low thermal conductivity insulating layer 9, an adhesive or the like consisting only of an organic polymer medium is coated on the metal base 1 using the coating method described above.

In this way, the high thermal conductivity insulating layer 10 and the low thermal conductivity insulating layer 9
Copper foil 3 is laminated onto the metal base 1 selectively coated with the following, and pressed while heating with a heating nib press to obtain a highly thermally conductive metal base copper foil plate (FIG. 3). This metal base copper clad board is subjected to wiring processing by etching or the like based on the pattern design, and 1 g of a highly thermally conductive metal base print/wiring board is obtained. Note that an insulating layer 9 is provided on the metal base 1.
, 1o may be coated on the copper foil 3.

Moreover, it goes without saying that various other manufacturing methods are possible.

As the metal base 1, it is desirable to use aluminum or alumite-treated aluminum, which is inexpensive and has high thermal conductivity. In this way, by using aluminum or treated IC aluminum as the 41 diagonal of the metal base 1, the heat dissipation characteristics are further improved, and furthermore, it is possible to mount high power and high heat generation components 4. As a result, it is possible to further reduce the size and weight of the highly thermally conductive metal-based printed wiring board and the radiation fin. In addition, a lifting platform and F distribution using anodized aluminum.
In the A substrate manufacturing process, the etching culm is added to the etching process, which also has the effect of not being corroded by the etching solution.
It can be obtained by f u.

Effects of the Invention - As explained above, according to the present invention, since the insulating layer is selectively provided with a material of low thermal conductivity and a material of high thermal conductivity, it is possible to achieve higher power than before. Practical work on high-density high-heating components adjacent to other electronic components 1!
7ru. According to IC, high thermal conductive metal base pudding 1~
It is possible to reduce the size of the wiring board and the size and weight of the radiation fin.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a conventional high thermal conductive metal base print 1 - a copper clad plate used for a wiring board, and Fig. 2 is a cross sectional view of a conventional high thermal conductive metal base print 1 - mounted on a wiring board in the lζ state. , FIG. 3 is a cross-sectional view of a copper-clad board used in a highly thermally conductive metal-based printed wiring board according to an embodiment of the present invention.
The figure is a cross-sectional view of one embodiment of the present invention mounted on a highly thermally conductive metal-based printed wiring board. 1...metal base, 3...copper foil conductor layer), 9...
・Low thermal conductivity insulating layer, 10... High thermal conductivity insulating layer agent Yoshihiro Morimoto Figure 1 Figure 8

Claims (1)

[Claims] 1. A metal base, an insulating layer laminated on the metal base, and a conductor layer laminated on the insulating layer, the insulating layer being an insulating layer made of a material with low thermal conductivity. A highly thermally conductive metal-based printed wiring board having a structure in which layers and an insulating layer made of a highly thermally conductive material are selectively arranged. 2. The highly thermally conductive metal-based printed wiring board according to claim 1, wherein aluminum is used as the metal base. 3. The highly thermally conductive metal-based printed wiring board according to claim 1, wherein alumite-treated aluminum is used as the metal base.