JPS6245719B2 - - Google Patents

Description

[Detailed description of the invention]

In the present invention, a conductive circuit is sandwiched and covered with an aluminum plate on which an electrically insulating oxide film is formed on the surface by an anodic oxidation method and an electrically insulating layer made of synthetic resin, and only necessary parts of the conductive circuit are provided on the aluminum plate. This is a printed wiring board whose surface is exposed through a through hole. The printed wiring board uses a copper-clad laminate that integrates an electrically insulating layer of synthetic resin and electrolytic copper foil. Conductive circuits are formed by conventional printing etching, and holes for mounting parts are formed by punching or drilling. This is the normal one. In response to the recent demand for miniaturization of electronic device parts, these ordinary printed wiring boards have become more densely packed with conductive circuits and components. Problems such as deterioration of the printed wiring board and damage to mounted components due to temperature rise and heat accumulation occur, and circuit design is reaching its limits. Further, mounting of components on a printed wiring board and fixing of conductivity are usually carried out by soldering. This can be done either by printing a solder resist on the parts of the printed wiring board that do not require soldering, and after inserting the component into the component mounting hole, it is immersed in a solder bath at 200 to 300°C for a few seconds to ensure continuity, or by using a soldering iron. This is a method of fixing conductivity. During this soldering, a normal printed wiring board is subjected to an instantaneous heat shock and the heat that remains on the printed wiring board, causing the conductive circuit of the printed wiring board to separate from the electrical insulating layer, the conductive circuit to be disconnected, and the mounted components to be separated. Damage is often seen and has become a problem. On the other hand, various printed wiring boards using aluminum plates as substrates have been devised to compensate for the weaknesses of the above-mentioned ordinary printed wiring boards. Printed wiring boards using this aluminum plate as a substrate can be roughly divided into Figures 1 and 2.
It can be summarized into two types as shown in the figure. That is, a conductive circuit 3 is obtained by using a copper-clad aluminum substrate in which an aluminum plate 1 and an electrolytic copper foil are laminated and bonded via an electrical insulating layer 2 as shown in FIG. Printed wiring board. An aluminum plate 1 as shown in Fig. 2 is made into the required shape and size of a printed circuit board, and after punching or drilling a through hole 4 in a predetermined portion, an anode is placed on the surface of the aluminum plate including the inner wall surface of the through hole 4. Printed wiring obtained by forming an insulating oxide film 5 by an oxidation method, further forming an insulating layer 6 coated with an insulating paint, etc., and then forming a conductive circuit 7 by a plating method, a vapor deposition method, a conductive paint printing method, etc. It is a board. The former is a printed wiring board with excellent heat dissipation and dimensional stability, but its biggest drawback is that it is impossible to drill holes in the board and mount components because the aluminum plate is an electrical conductor. be. Therefore, the attachment parts are limited to parts that can be fixed on the conductive circuit surface, such as chip elements. Like the former, the latter has excellent heat dissipation and dimensional stability, but not only is the manufacturing process complicated and requires advanced technology, but it also has poor soldering heat resistance, heat resistance, and It is unreliable and inferior in all characteristics such as moisture resistance, peel strength of conductive circuits, and continuity reliability, and its uses are extremely limited. The printed wiring board of the present invention has heat dissipation properties, dimensional stability,
This printed wiring board takes full advantage of the physical properties of aluminum plates, such as mechanical strength, and is comparable in electrical properties to ordinary printed wiring boards. That is, the present invention has a structure in which the surface of the conductive circuit of a conventional printed wiring board is covered with an aluminum plate coated with an oxide film, and only the necessary portion of the conductive circuit is exposed through a through hole provided in the aluminum plate. Therefore, the characteristics of ordinary printed wiring boards are fully satisfied, and the heat generated from the conductive circuits and mounted components is immediately dissipated through the aluminum plate, eliminating any adverse effects such as deterioration or damage to the printed wiring boards and mounted components due to heat.
Furthermore, it becomes possible to increase the density of circuit wiring and component mounting. Also, when fixing mounted components to a printed wiring board by soldering, the aluminum plate with an anodized film comes into contact with the solder, so the aluminum plate acts as a solder resist, and at the same time, the heat during soldering is absorbed by the solder. The heat is dissipated through the aluminum plate almost immediately after the work is completed, reducing the adverse effects of heat on the printed wiring board and mounted components. Furthermore, since it uses an aluminum plate with good dimensional stability, it has less expansion and contraction than ordinary synthetic resin printed wiring boards, and has good dimensional stability, so it is less prone to warping, twisting, etc. There will be fewer problems. Moreover, since the printed wiring board of the present invention is obtained by obtaining a normal printed wiring board by a conventional method and then bonding an aluminum plate to it, it can be used in the same way as a normal printed wiring board and can be used for an unspecified number of purposes. It can be used in electrical and electronic equipment, there is no need for electrical conduction between parts and aluminum plates, and it maintains the electrical and mechanical properties of ordinary printed wiring boards, while at the same time maintaining normal thermal properties and dimensional stability. It exhibits superior characteristics to other printed wiring boards. The printed wiring board of the present invention will be explained with reference to the drawings. The printed wiring board of the present invention has a single-sided printed wiring board having an electrically insulating layer 8 made of synthetic resin as shown in FIG. , surface and through hole 1
1. An aluminum plate 10 shown in FIG. 4 having an oxide film formed on its inner wall surface is prepared. A single-sided printed wiring board and an aluminum plate 10 with the conductive circuit 9 on the inside so that the conductive circuit land portion 9' and the through hole 11 are aligned with each other.
A laminated material 12 prepared separately is further laminated on the side of the single-sided printed wiring board where the conductive circuit 9 is not provided, and these are bonded together under heat and pressure. At this time, the conductive circuit land portion 9' of the single-sided printed wiring board
is bent and press-fitted into the through hole 11 of the aluminum plate 10 as shown in FIG. The components are mounted on the printed wiring board by bending and press-fitting them into the through-holes 11 as shown in FIG. Small parts mounting hole 13
part 1 by punching or drilling.
4 is inserted from the side opposite to the aluminum plate 10, and then fixed by the solder dip method, solder float method, or
This is done using a soldering iron method, etc., and the final printed wiring board as shown in FIG. 6 is obtained. 15 is solder. The thickness of the single-sided printed wiring board shown in FIG. 3 is preferably one-half or less of the final product board thickness since it is necessary to press-fit the conductive circuit land portion 9' into the through hole 11 of the aluminum plate 10 and bend it. The electrical insulating layer 8 of the single-sided printed wiring board shown in Figure 3 is made by impregnating and curing a thermosetting resin such as phenol, epoxy, or polyester into a base material such as paper, cloth, or woven glass fabric, or by curing polyester, Films or sheets made of polyimide, polyamideimide, etc. The conductive circuit 9 is 5 to 100
μ thick copper foil, nickel foil, aluminum foil,
Chrome foil, etc. The diameter of the conductive circuit land portion 9' is such that the conductive circuit land portion 9' has a diameter such that the conductive circuit land portion 9' has a diameter such that the conductive circuit land portion 9' is
It is preferable that the diameter of the through hole 11 be at least 5% larger than the diameter of the through hole 11 to prevent wire breakage. The thickness of the aluminum plate 10 in FIG. 4 is 0.1~
3 mm is preferred. If it is less than 0.1 mm, the effects of heat dissipation and dimensional stability will be lost, and if it is more than 3 mm, it will be difficult to press and bend the conductive circuit land portion 9' into the through hole 11 of the aluminum plate 10 as shown in FIG. As a result, it becomes impossible to solder the mounted components. Aluminum plate 10 and through hole 11
The anodic oxide film 16 formed on the surface of is aluminum oxide, and the film formation method is JIS standard H-8601.
In this method, the film thickness must be 5μ or more, considering electrical properties such as electrical insulation and breakdown voltage. It is desirable that the diameter of the through holes 11 in the aluminum plate be at least 5% smaller than the diameters of the conductive circuit lands 9' shown in FIG. 3, and at least 5% larger than the component mounting holes 13 shown in FIG. . As shown in FIG. 5, the heating and pressure forming method of bending and press-fitting the conductive circuit land portion 9' of the single-sided printed wiring board into the through hole 11 of the aluminum plate 10 is performed under pressure of 30 to
The weight is 200Kg/cm ² , the temperature is 150 to 180°C, and the time is about 30 to 90 minutes. It is preferable to use an adhesive containing polyacetal and phenolic resin as main components to bond the aluminum plate and the single-sided printed circuit board. The adhesive is applied to the surface of the aluminum plate 10 to a thickness of 20 to 50 μm. The laminated material 12 used during heating and pressure molding is
It is made by impregnating a thermosetting resin such as phenol, epoxy, polyester, etc. into a base material such as paper, cloth, glass woven cloth, etc., and is cured by heating and pressing, and does not necessarily have to be the same as the electrical insulating layer 8. Further, if necessary, an adhesive containing polyacetal and phenolic resin as main components may be applied to the surface of the electrical insulating layer 8 that comes into contact with the laminated material 12. The component mounting hole 13 shown in FIG. 6 is formed by punching or drilling, and its diameter is preferably 5% or more smaller than the through hole 11 of the aluminum plate 10. Five types of printed wiring boards shown in Table 1 A to E were manufactured with different materials and board thicknesses according to the structure of the present invention, and the heat dissipation and
The dimensional stability and electrical properties of the printed wiring board were compared with a conventional paper-based phenolic resin printed wiring board and a glass cloth-based epoxy resin printed wiring board. The results are shown in Table 2.

【table】

【table】

[Table] As mentioned above, the printed wiring board of the present invention has a structure in which the conductive circuit surface of a normal printed wiring board is covered with an aluminum plate, so it maintains sufficient electrical properties of a normal printed wiring board and has high mechanical strength. It has improved heat dissipation and dimensional stability, which are the characteristics of aluminum plates, and its industrial value is extremely large.

[Brief explanation of the drawing]

Figures 1 and 2 are cross-sectional views of a conventional printed wiring board using an aluminum plate as a substrate, Figure 3 is a plan view of a single-sided printed wiring board used in the present invention, and Figure 4 is an aluminum plate used in the present invention. FIG. 5 is a plan view of the board, FIG. 5 is a cross-sectional view of the printed wiring board of the present invention, and FIG. 6 is a cross-sectional view showing a state in which components are mounted on the printed wiring board in FIG. 8 is an electrical insulating layer, 9 is a conductive circuit, 9' is a conductive circuit land, 10 is an aluminum plate, 11 is a through hole, 12 is a laminated material, and 16 is an anodized film.

Claims (1)

[Claims] 1. A single-sided printed wiring board with a conductive circuit formed on an electrically insulating layer made of synthetic resin, an aluminum plate having a through hole at a position corresponding to the land of the conductive circuit and an oxide film formed on the surface and the wall of the through hole, and the above. Printing in which the laminated material in contact with the side without conductive circuits of a single-sided printed wiring board is integrally molded by heating and pressing with the conductive circuits inside, and the land portions of the conductive circuits are bent and press-fitted into the through holes of the aluminum plate. wiring board.