JPS5880897A - Method of producing metal core 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] The present invention relates to a method for manufacturing a metal core printed wiring board.

Metal-core printed wiring boards have been developed to facilitate the dissipation of 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. An insulating layer 2 such as an insulating resin is formed on the surface of a metal plate 1, and a metal foil 3 such as a copper foil is formed on this insulating layer 2.
After bonding, a film pattern is formed, a conductor circuit is created by etching, and it is cut into a predetermined shape.
has been done.

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 external shape, the '4%' which is electrically insulating and has corrosion resistance is not protected by a protective film for corrosion prevention. There was a drawback that it required coating. Additionally, cutting the metal foil 3 to its outer shape causes the cut edge of the metal foil 3 to extend downward, so-called sagging, but in order to improve heat dissipation, the insulating layer 2 is made thinner.
There is a drawback that the metal plate 1 and the metal foil 3 often come into contact with each other at this cut edge as shown in FIG.

The present invention provides a method for manufacturing a metal-core printed wiring board that overcomes these drawbacks, and includes providing a strip-shaped hole in a metal plate so as to encompass the outer shape of the printed wiring board. The metal plate is characterized in that an insulating resin is applied and filled into the surface of the metal plate and the band-shaped hole, and the metal plate is cut along the band-shaped hole so that the metal plate does not come out on the cut surface.

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

Metal plate 11 with dimensions larger than the external dimensions of the printed wiring board
Drill reference holes 12.12 at both ends of the outer frame as shown in FIG. 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;
2.0-1 aluminum plate is used.

Next, the outer shape of the printed wiring board is included in the metal plate 11 so as to leave a plurality of bridge parts 14 connecting and supporting the outer frame 11a of the metal plate 11 and the inwardly extending metal plate 11b through the belt-shaped holes 13. A belt-shaped hole 13 of a predetermined width is machined at the position, and a prepared hole 15 for inserting a predetermined component is bored in the inner metal plate 11b surrounded by the belt-shaped hole 13.

The inner edge of the band-shaped hole 13 is arranged inside the outer dimensions of the printed wiring board, that is, at least 0.5 mm or more 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 band-shaped hole 13 and the pilot hole 15 are formed by etching after forming an etching resist group on the metal plate 11. If the holes are etched in this way, the strip hole 13 and pilot hole 15 can be drilled in one process, and the pilot hole 1
It can be done in a short time regardless of the number of 5s. In addition, the pilot hole 15 will be filled with insulating resin in a later step, but the pilot hole 15 and band-shaped hole 13 formed by etching have tapered portions 15a, 5, and 13a formed at the upper and lower edges thereof. This has the advantage of making it easier for the insulating resin to flow in. (See Figure 3 (1)) Next, as shown in Figure 3 (2), the strip hole 13 and the prepared hole 1 are
An insulating resin 16 having an adhesive effect is applied to the upper and lower surfaces of the metal plate 11 with holes 5 formed therein using a roller tool or the like.
A metal foil 17 is applied thereon, the insulating layer 116 is given fluidity by heating and pressurizing, and the band, hole 13 and prepared hole 15 formed in the metal plate 11 are filled with insulating resin. As the reaction progresses, metal foil 17 is bonded to the upper and lower surfaces of metal plate 11 via insulating resin 16. .

In this step, a metal foil 1 is applied to the top and bottom surfaces of the metal plate 11 by applying varnish to an inorganic substance such as a glass edge line.
You may also heat and pressurize by applying 7 and sandwiching it.

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 addition, in this insulating resin filling process, 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 a known method using a female pattern. Alternatively, instead of this method using release paper, as shown in No. 411, one band-shaped hole 13' is formed outside the band-shaped hole 13, and the amount of insulating resin is adjusted so that the filling amount does not reach the reference hole 12. The adjustment prevents the reference hole 12 from being filled with insulating resin. Note that 14' is the bridge, and then the metal plate 11
The reference hole 12.12 formed in is counter-sunk to serve as a reference position, and a hole 18 having a smaller diameter than the pilot hole 15 is bored through the metal foil 17 on the surface so as to overlap with the center of the pilot hole 15.

(See Figure 3 (3)) This hole may be made by a numerically controlled drilling machine or a punching press.

Next, this hole 18. Electroless plating 19 and electroplating 20 for through-hole plating on the lid.

An etching resist group 21 is formed using a film forming pattern circuit. (See FIG. 3 (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 group 21 is removed.

(See FIG. 3 (6)) 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 green part inside 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(6), the metal plate 1
A metal core printed wiring board is formed in which 1 is a metal core and the metal core is not exposed on the outer cut surface.

Incidentally, for the purpose of preventing corrosion, moisture-proofing, dust-proofing, etc., the printed circuit board may be coated with a solder resist film, an organic film, or a metal film.

Note that, instead of etching, the pilot hole 15 may be formed by a punching press or a pole machine under single numerical control, and the strip-shaped hole 13 may also be formed by a punching press or the like.

As explained above, according to the present invention, (1) The printed wiring board has no metal core protruding from the outer cut surface except for a limited part (bridge section 14), and the insulating resin layer is removed by cutting the outer shape. Since it is obtained in a coated state, there is no need to form a protective film to maintain the insulation properties of the exposed metal core or prevent corrosion, which is required in the past, resulting in improved workability.

(2) Since the metal core exists only up to the inside of the peripheral edge of the printed wiring board, excluding the bridge portion 14, even if the cut edge of the metal foil sag when cutting the outline, the metal There is no risk of short circuit between the metal core and the metal 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 bridge part 1
If the number 4 is removed, the circuit pattern can be formed up to the periphery of the printed wiring board, and the effective area for forming the circuit pattern can be expanded.

Further, if the strip hole 13 and the pilot hole 15 are formed by etching as described above, the pilot hole 15 and the strip hole 13 can be drilled at the same time. Also, regardless of the number of pilot holes 15, the holes can be drilled with a chisel drill. Also, pilot hole 15, strip hole 1
A tapered portion 15a is formed on the upper and lower edges of 3 by etching.
, 13a are formed, it becomes easy to fill the insulating resin, and the workability of filling is greatly improved.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing a metal-core printed wiring board made by a conventional method, Fig. 12- is a flat curved view showing the position of hole processing in a metal plate in the manufacturing method of the present invention, and Fig. 3 is a cross-sectional view showing a metal core printed wiring board made by a conventional method. A schematic process diagram of a method for manufacturing a metal core printed wiring board according to an embodiment,
FIG. 4 is a plan view showing the position of drilling holes in a metal plate in another embodiment of the present invention. 11...Metal plate, 12...Reference hole, -
:13... Band hole, 14... Bridge part,
15... Pilot hole, 16---- Insulating resin, 1
7... Metal foil, 18... Hole. Agent Patent Attorney Makoto Hayakawa Figure 1 Figure 2 Ill. Figure 3 Figure 3 Figure 4

Claims (2)

[Claims] (1) A step of drilling a reference hole in the outer frame of the metal plate that is located outside the outer shape of the printed wiring board; 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 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 front arrow of the metal plate; Step 1 of forming a conductor through resin and drilling a through hole smaller in diameter than the pilot hole so as to overlap the center of the indicator hole;
A method for manufacturing a metal-core printed wiring board, comprising the step of cutting the printed wiring board along the band-shaped hole outward from the inner edge of the band-shaped hole. (2) The method for manufacturing a metal-core printed wiring board according to claim 1, wherein the band-shaped holes and the pilot holes are formed by etching.