JPH0217955B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a metal core printed wiring board.

Metal-core printed wiring boards have been developed to make it easier to dissipate the heat generated by mounted electronic components, but this type of metal-core printed wiring boards are made of aluminum or other materials that serve as the metal core, as shown in Figure 1. Forming an insulating layer 2 such as an insulating resin on the surface of the metal plate 1,
After bonding a metal foil 3 such as copper foil to this insulating layer 2, a film pattern is formed, a conductive circuit is formed by etching, and the conductive circuit is cut into a predetermined shape.

However, according to the above manufacturing method, since the metal plate 1, which is the metal core, is exposed on the cut surface of the outer shape,
It had the disadvantage of requiring the application of a protective film for electrical insulation or corrosion protection. Also, when cutting the outer shape, the cut edge of the metal foil 3 extends downward, causing so-called sagging, but since the insulating layer 2 is made thin to improve heat dissipation, the cut edge of the metal foil 3 as shown in FIG. As shown, there was a drawback that the metal plate 1 and the metal foil 3 often came into contact with each other.

The present invention provides a method for manufacturing a metal-core printed wiring board that overcomes these drawbacks, and provides a method for manufacturing a metal-core printed wiring board by providing a band-shaped hole in the metal plate that serves as the metal core so as to encompass the outer shape of the printed wiring board. The metal plate is characterized in that the surface of the metal plate and the band-shaped hole are coated and filled with resin, and the metal plate is cut along the band-shaped hole so that the metal plate is not exposed on the cut surface.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. 2, reference holes 12, 12 are bored at both ends of the outer frame of the metal plate 11, which has dimensions larger than the outer dimensions of the printed wiring board. This hole drilling is performed using a jig boring machine, a numerically controlled drilling machine, etc.
The material and thickness of the metal plate 11 must be determined in consideration of mechanical properties and heat dissipation properties; for example, an aluminum plate with a thickness of 0.6 to 2.0 mm is used.

Next, a plurality of bridge portions 14 are left in the metal plate 11 via the belt-shaped holes 13 to connect and support the outer frame 11a of the metal plate 11 and the inner metal plate 11b at positions that include the outer shape of the printed wiring board. A band-shaped hole 13 of a predetermined width is machined in the metal plate 11b, and a pilot hole 15 for inserting a predetermined component is bored in the inner metal plate 11b surrounded by the band-shaped hole 13.

The inner edge of the band-shaped hole 13 is made to be inside the outer dimensions of the printed wiring board, that is, to be at least 0.5 mm inside the outer circumference of the printed wiring board. Further, the hole diameter of the pilot hole 15 is made larger than the finished hole that will serve as the component insertion hole.

The belt-shaped hole 13 and the pilot hole 15 are drilled using the metal plate 1.
After forming an etching resist film in step 1, etching is performed. If holes are made by etching in this manner, the process of drilling the band-shaped holes 13 and the pilot holes 15 can be performed at the same time, and can be done in a short time regardless of the number of pilot holes 15. In addition, the pilot hole 15 will be filled with insulating resin in a later process, but the pilot hole 15 will be filled with insulating resin in a later step.
Since tapered portions 15a and 13a are formed at the upper and lower edges of the band-shaped hole 13, there is an advantage that the insulating resin easily flows into the prepared hole 15. (3rd
(See FIG. 1) Next, as shown in FIG. 3, an insulating resin 16 having an adhesive effect is applied to the upper and lower surfaces of the metal plate 11 in which the strip holes 13 and pilot holes 15 have been drilled, using a roller coater or the like. A metal foil 17 is applied on top of the metal foil 17, fluidity is imparted to the insulating resin 16 by applying heat and pressure, and the band-shaped hole 13 and pilot hole 15 formed in the metal plate 11 are filled with the insulating resin, and the reaction is further carried out. Then, metal foil 17 is bonded to the upper and lower surfaces of metal plate 11 via insulating resin 16.

In addition, in this step, on the upper and lower surfaces of the metal plate 11,
The metal foil 17 may be applied to an inorganic material such as glass fiber impregnated with varnish, sandwiched, and heated and pressurized.

Further, instead of joining the metal foil 17, a metal layer may be formed on the surface of the insulating resin 16 by metal plating.

In this insulating resin filling step, the reference hole 12 provided in the outer frame 11a of the metal plate 11 is prevented from being filled with the insulating resin by using a known method using release paper. Alternatively, instead of this method using release paper, as shown in FIG. By adjusting the amount of the insulating resin, the reference hole 12 is prevented from being filled with the insulating resin. Note that 14' is a bridge section.

Next, the reference hole 12 formed in the metal plate 11,
12 as a reference position, and from the metal foil 17 on the surface, drill the pilot hole 1 so that it overlaps the center of the pilot hole 15.
A hole 18 with a smaller diameter than 5 is drilled. (See FIG. 3.) This drilling may be done by a numerically controlled drilling machine or a punching press.

Next, electroless plating 19 and electroplating 20 for through-hole plating are applied to this hole 18 to form an etching resist film 21 based on a film forming pattern circuit. (See FIG. 3 and 4) In this step, after forming the positive film forming circuit, an insoluble metal may be attached to the etching solution.

Next, after removing unnecessary metal layers by etching, the etching resist film 21 is removed.
(See FIG. 3, FIG. 5) Next, along the band-shaped hole 13 of the metal plate 11 (indicated by A in FIG. 2), the outer shape is cut outward from the inner edge of the band-shaped hole 13. Note that this step can also be performed using a punching press.

In the above manner, as shown in FIG. 3, a metal core printed wiring board is formed in which the metal plate 11 is a metal core and the metal core is not exposed on the cut surface of the outer shape.

Note that a coating made of solder resist, an organic coating, or a metal coating may be applied to the printed wiring board for the purpose of preventing corrosion, moisture, dust, or the like.

Note that the pilot hole 15 may be formed by a numerically controlled punching press or a drilling machine instead of etching, and the band-shaped hole 13 may be similarly formed by a punching press or the like.

As explained above, according to the present invention, (1) the printed wiring board is limited to a limited part (bridge part 1);
Except for 4), the metal core is not exposed on the cut surface and the insulating resin layer is covered with the cut surface, making it possible to maintain the insulation properties or prevent corrosion of the exposed metal core as in the conventional method. There is no need to form a protective film to prevent this, and workability is improved.

(2) Since the metal core exists only up to the inside of the peripheral edge of the printed wiring board, except for the bridge section 14, even if the cut edge of the metal foil sag during outline cutting, the metal foil and metal There is no risk of short circuit with the core. For this reason, in the past, in order to prevent this short circuit, the circuit pattern had to be formed slightly inside the peripheral edge of the printed wiring board, but in the printed wiring board obtained by the present invention, the circuit pattern was formed slightly inside the periphery of the printed wiring board, except for the position where the bridge portion 14 is present. The circuit pattern can be formed up to the peripheral edge of the printed wiring board, and the effective area for forming the circuit pattern can be expanded.

It has the following effects.

Furthermore, if the strip hole 13 and the pilot hole 15 are formed by etching as described above, the pilot hole 15
and the drilling work of the strip hole 13 can be performed at the same time. Further, regardless of the number of pilot holes 15, the holes can be drilled in a short time. Further, since tapered portions 15a and 13a are formed by etching at the upper and lower edges of the pilot hole 15 and the band-shaped hole 13, filling with the insulating resin becomes easy and the workability of filling is greatly improved.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a metal-core printed wiring board produced by a conventional method, FIG. 2 is a plan view showing the position of hole drilling in a metal plate in the manufacturing method of the present invention, and FIG. 3 is an embodiment of the present invention. FIG. 4 is a schematic process diagram of a method for manufacturing a metal core printed wiring board according to the present invention, and FIG. 4 is a plan view showing the position of hole processing in a metal plate in another embodiment of the present invention. 11...Metal plate, 12...Reference hole, 13...Strip hole, 14...Bridge part, 15...Prepared hole, 16...
Insulating resin, 17...metal foil, 18...hole.

Claims (1)

[Claims] 1. A step of drilling a reference hole in an outer frame of a metal plate that is located outside the outer shape of the printed wiring board; a band-shaped hole that includes the outer shape of the printed wiring board in the metal plate; processing the metal plate so as to leave a bridge portion that connects and supports the outer frame of the metal plate and the metal plate located inside the belt-shaped hole through the belt-shaped hole; a step of drilling a pilot hole; a step of applying and filling an insulating resin on at least the inner surface of the band-shaped hole, the band-shaped hole and the pilot hole; and a step of applying the insulating resin to the metal plate. forming a conductor through the hole; drilling a through hole with a smaller diameter than the pilot hole so as to overlap the center of the pilot hole; A method for manufacturing a metal core printed wiring board, comprising the step of cutting the printed wiring board to an outer shape. 2. The method of manufacturing a metal-core printed wiring board according to claim 1, wherein the band-shaped holes and the pilot holes are formed by etching.