JP6969891B2 - Manufacturing method of printed wiring board - Google Patents

Description

The present invention relates to a method for manufacturing a printed wiring board that dissipates heat generated from a mounted component to a heat sink on the other side through a through hole of the printed wiring board.

Recently, the parts themselves tend to be modularized and become smaller. Meanwhile, the heat dissipation requirement did not change, and it was difficult to effectively dissipate heat even if a normal through-hole plating through hole was connected to the heat sink.

Generally, there is a printed wiring board in which the copper pin is press-fitted into the through hole of the printed wiring board by mechanically press-fitting the copper pin (so-called "copper inlay").
In the copper inlay, the copper pin is made thicker than the plate thickness of the board, the copper pin is inserted into the corresponding through hole, mechanical pressure is applied, and the copper pin is pushed and crushed by the mechanical pressure. Then, the inner wall of the through hole and the copper pin come into contact with each other (see, for example, Patent Document 1).

Hereinafter, a copper inlay for mechanically press-fitting such a copper pin will be described with reference to FIGS. 6 and 7.

The printed wiring board T includes a conductor circuit 51 on the front and back of the insulating substrate 50, and the conductor circuit 51 is composed of a copper foil 51a and a panel plating 51b. The panel plating 51b is composed of electrolytic copper plating and electrolytic copper plating, and the copper pin 52 is press-fitted into the through-plating through hole 51c by the mechanical pressure of the press-fitting device 53.

As shown in FIG. 7, the copper pin 52 is in a state of being crushed by mechanical pressure in the through-plating through hole 51c due to the press fitting. However, since the copper pin 52 is mechanically press-fitted, mechanical stress is also applied to the printed wiring board, and there is a problem that a peeled portion 54 is formed on the glass fiber and the resin of the insulating substrate 50.

Therefore, in order to improve the peeling between the glass fiber and the resin, a method of fixing the copper pin with an insulating film has been required from a mechanical press-fitting method.
However, although the adhesion between the glass fiber and the resin is improved by the method of fixing with an insulating film, the following new problems have arisen.
That is, first, a copper pin having a height lower than the plate thickness of the substrate is inserted into the through hole formed in the printed wiring board. Next, the resin for forming the insulating film is filled, but at that time, since the gap between the inner wall of the through hole and the copper pin is small, if the resin is not filled properly, the filled resin will rise, and it will be used for mounting parts in the subsequent process. There was a risk of failure. Further, the insulating film for fixing the copper pin needs an adhesive force for fixing the copper pin at least until the component mounting in the subsequent process, but there is a problem that the adhesive force is weak because only a small amount is filled in the gap. ..
Therefore, all of them are obstacles to component mounting, and it is difficult to stably mount components.

Japanese Unexamined Patent Publication No. 2010-263003

The present invention has been made in view of the above-mentioned conventional problems and actual conditions, and an object of the present invention is to provide a printed wiring board having excellent heat dissipation without any obstacle to component mounting.

As a result of conducting various studies to solve the above problems, the present inventor has found that extremely good results can be obtained by inserting a metal piece into a through hole and fixing it with ink by an inkjet method. completed.

That is, the present invention is a method for manufacturing a printed wiring board that dissipates heat from heat-generating parts , and is a semi-cured prepreg and a copper foil above and below a core substrate in which a double-sided copper-clad laminated board is circuit-formed by a photographic method. A step of forming a through hole in the insulating base material laminated with the above and applying electroless / electrolytic copper plating to the through hole, and then a step of forming a circuit to selectively form a through plating through hole and a through hole. Then, a step of forming a solder resist, then a step of laminating a peelable insulating resin film on one surface, and then a step of selectively inserting a metal piece into a through hole or a through plating through hole. Next, an ink is applied from the opening side where the metal piece is exposed to the gap between the metal piece and the through hole or the through plating through hole by an inkjet method to form an insulating film for fixing the metal piece, and then It is characterized by having a step of peeling off the insulating resin film, and then a step of solder-mounting a heat-generating component on the metal piece and forming heat-dissipating fins on the opposite surface thereof via a heat-conductive insulating resin. The above problem is solved by the method of manufacturing a printed wiring board.

In the printed wiring board obtained by the present invention, the through holes of the metal piece and the printed wiring board are fixed by the insulating film formed by ink application by the inkjet method, so that the stable fixing action of the metal piece and the through hole can be obtained. As a result, stable mounting is possible without any trouble in component mounting.

It is sectional drawing which shows the manufacturing example of the printed wiring board of this invention. It is sectional drawing which shows the manufacturing example of the printed wiring board of this invention following FIG. It is sectional drawing which shows the manufacturing example of the printed wiring board of this invention. FIG. 3 is a cross-sectional process diagram showing a manufacturing example of the printed wiring board of the present invention, following FIG. It is sectional drawing of the heat dissipation structure part which mounted the heat generating component on the printed wiring board obtained by this invention. It is sectional drawing which shows the manufacturing example of the conventional printed wiring board. It is sectional drawing of the conventional printed wiring board obtained in FIG.

Embodiments of the present invention will be described with reference to FIGS. 1 to 4.

First, a semi-cured prepreg 12 and a copper foil 13 are laminated on top and bottom of a core substrate 11 on which a double-sided copper-clad laminate is formed by a photographic method (FIG. 1A). Next, a through hole 14 is formed in the laminated substrate laminated in FIG. 1 (a) by drilling or laser processing (FIG. 1 (b)).

Subsequently, electroless / electrolytic copper plating 15 is applied to the entire surface of the laminated substrate on which the through hole 14 is formed (FIG. 2 (c)).
Next, a circuit is formed by a photographic method, a through-plating through hole 16 and a through hole 17 are selectively formed, and then a solder resist 18 is formed on the outermost layer by a photographic method (FIG. 2 (d)). ..
Next, the peelable insulating resin film 19 is attached to one surface (lower surface) of the printed wiring board on which the solder resist 18 is formed (FIG. 3 (e)). The insulating resin film 19 serves as a support for supporting the metal piece 20 inserted into the through hole 17.

Next, the metal piece 20 is inserted into the through hole 17. After that, using an inkjet coating device, ink for inkjet is applied to the gap between the metal piece 20 and the through hole 17 from the upper opening side where the metal piece 20 is exposed to form an insulating film 21 to form the metal piece. 20 is fixed to the through hole 17 (FIG. 3 (f)). At the same time as forming the insulating film 21, characters can also be formed by using inkjet. In this case, since the insulating film 21 can be formed at the same time as normal character printing, the metal piece 20 can be fixed without adding an extra step, and the production efficiency is improved.

The insulating film 21 for fixing the metal piece 20 formed of the ink is cured at a temperature lower than the UV curing temperature, the curing temperature of the UV / thermal curing combined type, or the curing temperature of the solder resist of the printed wiring board. preferable.
Incidentally, the curing temperature of the solder resist 18 is around 180 degrees. Therefore, it is preferable that the insulating film 21 is cured at a temperature of 180 ° C. or lower, particularly between 100 ° C. and 150 ° C., because it can be processed without applying a thermal load to the printed wiring board.

Further, the gap between the metal piece 20 and the through hole 17 is designed to be about 50 μm on one side with respect to the diameter of the through hole 17. Therefore, even when the ink to be the insulating film 21 is formed by inkjet, it is preferable to adjust the viscosity of the ink to 0.15 dPa · s or less so that the ink easily penetrates into the gap.
If the viscosity of the ink is lower than 0.15 dPa · s, the ink smoothly penetrates into the gap even if the gap between the metal piece 20 and the through hole 17 is narrow, and the insulating film 21 formed by the ink penetrates the metal piece 20. It can be securely fixed by the hole 17. Moreover, since the ink smoothly penetrates into the gap between the metal piece 20 and the through hole 17, the insulating film 21 does not protrude extremely. Therefore, the step of flattening the protruding insulating film 21 by a polishing action or the like is omitted. Can be done.

Next, after fixing the metal piece 20 with the insulating film 21, the film 19 used as a support for supporting the metal piece 20 was peeled off to obtain a printed wiring board P (FIG. 4 (g)).
Next, an insulating film 21 was formed in the gap between the metal piece 21 and the through hole 17 on the surface from which the film 19 was peeled off in the previous step to obtain a printed wiring board Q (FIG. 4 (h)). However, as shown in FIG. 4 (h), it is not always necessary to form the insulating film 21 for fixing the metal piece 20 on both sides, and it goes without saying that either one-sided or double-sided specifications may be selected. ..

Subsequently, using FIG. 5, the heat-generating component 22 is soldered to the printed wiring board obtained in the present invention 23, and the heat-dissipating fins 25 are formed on the opposite surface thereof via the heat-conductive insulating resin 24. The heat dissipation structure of the plate will be described.
As a mechanism for heat dissipation in the heat dissipation structure portion R, heat from the heat generating component 22 is efficiently radiated to the outside from the heat dissipation fin 25 via the metal piece 20 arranged in the through hole. Since the metal piece 20 is made of a lump of metal, if heat dissipation performance is required, the hole diameter of the through hole is increased, and the metal piece 20 to be inserted into the through hole is also increased according to the hole diameter of the through hole. By doing so, the heat dissipation performance can be improved.

11: Core substrate 12: Semi-cured prepreg 13: Copper foil 14: Through hole 15: Electroless / electrolytic copper plating 16: Through plating Through hole 17: Through hole 18: Solder resist 19: Insulating resin film 20: Metal piece 21: Insulation film 22: Heat-generating component 23: Solder 24: Conductive insulating resin 25: Heat-dissipating fin P: Printed wiring board obtained in the present invention Q: Printed wiring board obtained in the present invention R: Obtained in the present invention Heat dissipation structure part 51c of printed wiring board: Through plating through hole 52: Copper pin 53: Press-fitting device 54: Peeling part between glass fiber and resin T: Conventional printed wiring board

Claims (4)

A method for manufacturing a printed wiring board to radiate heat from the heat generating component, double-sided copper-clad laminate insulating base material formed by laminating a prepreg and a copper foil in a semi-cured state and below the core substrate having the circuit formed by a photographic method the A step of forming a through hole and subjecting the through hole to electroless / electrolytic copper plating, and then a step of forming a circuit to selectively form a through plating through hole and a through hole, and then a solder resist. A step of forming a metal piece, then a step of laminating a peelable insulating resin film on one surface, and then a step of selectively inserting a metal piece into a through hole or a through plating through hole, and then the metal. A step of applying ink by an inkjet method to a gap between a metal piece and a through hole or a through plating through hole from the opening side where the piece is exposed to form an insulating film for fixing the metal piece, and then applying the insulating resin film. Manufacture of a printed wiring board characterized by having a step of peeling off, and then a step of solder-mounting a heat-generating component on the metal piece and forming heat-dissipating fins on the opposite surface via a heat-conductive insulating resin. Method. The method for manufacturing a printed wiring board according to claim 1, wherein characters are formed at the same time as an insulating film for fixing the metal piece by the inkjet method. The method for manufacturing a printed wiring board according to claim 1 or 2, wherein the viscosity of the ink used in the inkjet method is 0.15 dPa · s or less. Any one of claims 1 to 3, wherein the insulating film fixing the metal piece is cured at a curing temperature lower than the curing temperature of UV curing, UV curing and heat curing, or the solder resist of the printed wiring board. The method for manufacturing a printed wiring board according to the section.

Images