JP2849163B2 - Manufacturing method of electronic circuit board - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method of manufacturing an electronic circuit board having a high-density and fine circuit pattern.

(Prior art)

2. Description of the Related Art In recent years, the tendency of finer electronic circuit boards has become remarkable, and it is necessary to form as many patterns and through holes as possible on a board having a predetermined area.

The electronic circuit board is generally manufactured by a solder peeling method (see Examples).

Incidentally, in order to reduce the interval between the patterns, it is one of effective means to make the thickness of the plating layer as small as possible. For example, in a method for manufacturing a high-density and fine electronic circuit board with a pattern interval of 100 μm or less, an electroless
It is known that the generation of the bridge 80 (FIGS. 14 and 15) can be avoided by setting the thickness of the Ni plating layer to about 2 μm. Here, the bridge 80 refers to a phenomenon that occurs between the bases of the adjacent patterns 8, 8 at the end thereof during the electroless nickel plating or gold plating process. This bridge
Due to 80, the patterns 8 and 8 are short-circuited, resulting in insulation failure.

That is, on the copper plating layer 82 formed on the copper foil 81, a pattern plating layer such as a Ni-Au plating layer of the Ni plating layer 83 and the Au plating layer 84 is further formed thereon. At this time,
As the thickness of the Ni plating layer 83 increases, the bridge 80
Is more likely to occur.

On the other hand, it is known that the bridge 80 does not occur when the thickness of the Ni plating layer 83 is reduced to, for example, 2 μm or less.

[Problem to be solved]

However, the above prior art has the following problems.

That is, the high-density and fine pattern may require a certain thickness or more. For example, a pattern 8 or a terminal electrically connected to a semiconductor or a light emitting diode (LED) by wire bonding, a conductor land 85, and an inner wall 86 of a through hole 90 connected thereto. In these, strength that can withstand wire bonding, that is, wire bonding durability is required. Therefore, the minimum thickness of the Ni plating layer 83 is, for example, about 5 μm. Therefore, for example, in forming the pattern 8, the LED terminal, and the like by the electroless plating method, the bridge 80 is easily generated as shown in FIGS.

The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a method of manufacturing an electronic circuit board having a high-density and fine circuit pattern, which does not generate a bridge during metal plating.

[Solutions to solve the problem]

The present invention relates to a method for manufacturing an electronic circuit board, which comprises forming a circuit pattern on an insulated circuit board by performing pattern plating using solder on the insulated circuit board, and thereafter performing etching, solder peeling, and metal plating. A resin is applied to the entire surface of the insulated circuit board, cured, and then the surface of the resin layer is removed to expose the solder, and then the solder is peeled off. is there.

In the present invention, the most remarkable thing is that after the above-mentioned etching, a resin is applied to the entire surface of the insulated circuit board, cured, and then the surface of the resin layer is removed to expose the above-mentioned solder, and then the above-mentioned solder peeling Is to do.

The above-mentioned circuit pattern forms a Cu or Ni plating layer of a certain thickness by, for example, electroless plating.

In forming the resin layer, a resin film having a desired thickness is formed on the entire surface of the insulated circuit board including the pattern plating portion using solder by a spray coating method, a roll coater coating method, a printing method, or the like. I do. In curing the resin film, for example, exposure, electron beam irradiation, hot-air drying, or the like is used. As the resin, for example, an epoxy resin or a polyimide resin is used.

As a method of removing the surface of the resin layer, for example, there are a polishing process using a sand paver, a polisher process for polishing a resin applied surface, and a shot blasting method for projecting grit (small particles) onto the resin applied surface.

Further, as the solder stripping method, there is a method of removing a solder layer formed on the surface of the pattern plating using a solder stripping solution (acid solution).

[Action and effect]

In the present invention, first, a circuit pattern is formed on an insulated circuit board by electroless copper plating. Next, a portion other than the circuit pattern is coated with a plating resist film. Next, electrolytic copper plating is performed on the circuit pattern portion. Then, the surface of the circuit pattern is coated with solder by electrolytic solder plating and pattern plating is performed. The reason is that it is necessary to perform etching after the formation of the pattern plating layer to remove unnecessary copper-clad portions.

In addition, as the metal plating, the surface of the pattern plating layer after the above-mentioned solder peeling is further subjected to electroless plating.
A Ni-Au plating layer is formed.

The Ni-Au plating layer has an Au plating layer formed on the Ni plating layer. Therefore, it has excellent durability, conductivity, and wire bonding properties.

Further, since the Ni plating layer is formed with the resin layer separated, no bridge is generated between circuit patterns. The reason is that the recess formed by the resin layer
This is because a Ni plating layer will be formed.

Therefore, according to the present manufacturing method, it is possible to easily manufacture an electronic circuit board having a high-density and fine circuit pattern without causing a bridge at the time of metal plating.

〔Example〕

First Embodiment A method of manufacturing an electronic circuit board according to an embodiment of the present invention will be described with reference to FIGS.

As shown in FIG. 2 to FIG. 6, the manufacturing method of the present embodiment employs an electrolytic solder plating layer 16 on the insulating circuit board 9 by a solder peeling method.
Is performed by using the pattern plating. Thereafter, as shown in FIGS. 7 and 8, peeling and etching are performed.
As shown in FIG. 13 to FIG. 13, solder plating and metal plating such as Ni-Au are performed.

After the etching, as shown in FIGS. 9 and 10, a resin layer 4 is applied to the entire surface of the insulated circuit board 9 and cured, and then the surface of the resin layer 4 is removed and the electrolytic solder plating is performed. The layer 16 is exposed, and then the above-mentioned solder peeling is performed.

The electronic circuit board obtained in this example is one in which a circuit pattern 1 is formed on a substrate 9 as schematically shown in FIG. Here, the circuit pattern 1 is a copper foil 11
And a chemical copper plating layer 12 sequentially formed thereon,
Cu plating layer 13 (about 10μm thick) and electroless Ni plating layer
14 (thickness of about 5 μm) and Au plating layer 15 (thickness of about 0.5 μm)
m).

Next, a method of manufacturing an electronic circuit board will be described with reference to FIGS.
This will be described with reference to the drawings.

First, in the first step, as shown in FIG. 2, an activation process 10 is performed on the surface of the glass epoxy substrate 9 covered with the copper foil 11 using a hydrochloric acid-based palladium solution.

Next, in the second step, as shown in FIG. 3, a chemical copper plating layer is formed on the copper foil 11 by electroless copper plating.
Form 12. In the third step, as shown in FIG. 4, a plating resist 17 is formed by screen printing, and is exposed and developed.

Next, in the fourth step, by electrolytic Cu plating,
Chemical copper plating layer not covered by the plating resist 17
As shown in FIG. 5, an electrolytic Cu plating layer 13 (thickness: 10 μm) is formed on the surface of the substrate.

In the fifth step, as shown in FIG.
An electrolytic solder plating film 16 is coated on the electrolytic Cu plating layer 13. Further, as shown in FIG.
17 is peeled off.

Next, in the etching step, as shown in FIG. 8, portions other than the electrolytic solder plating film 16 formed on the electrolytic Cu plating layer 13 are removed by etching.

The electrolytic solder plating film 16 has a thickness of 10 to 15 μm as described later.

Thereafter, as shown in FIG. 9, the resin 4 is applied to the insulating circuit board 9. That is, the resin 4 is applied and cured so that the electrolytic solder plating layer 16 is also covered on the circuit pattern 1 of the insulating circuit board 9. The resin 4 uses an epoxy resin. The resin 4 is cured by heating.

Next, as shown in FIGS. 10 and 11, the surface of the resin layer was removed by a grinder (not shown) such as a belt sander.
The electrolytic solder plating layer 16 is exposed. That is, first, the resin layer 4
Until it is flush with the electrolytic solder plating film 16 (10th
Next, the electrolytic solder plating layer 16 is removed with an acid solution (FIG. 11).

Then, the surface is coated with a solder resist film 5 as shown in FIG.

Thereafter, as shown in FIGS. 1 and 13, Ni-Au plating is performed by electrolytic plating.

That is, the portion where the electrolytic solder plating layer 16 has been peeled off is
As shown in FIG. 13, first, a Ni plating layer 14 is formed by electroless plating. Next, as shown in FIG.
The plating layer 15 is also formed by electroless plating.
Thus, an electronic circuit board having the circuit patterns 1 and 1 is obtained.

 Next, the effects will be described.

In this example, the Ni plating layer 14 and the Au plating layer 15
In forming this, a resin layer 4 thicker than the circuit pattern 1 is formed between the circuit patterns 1 as shown in FIGS. 9 to 13. Therefore, the Ni plating layer 14 having a thickness of 5 to 7 μm and the thickness of 0.5 to
The Au plating layer 15 having a relatively large thickness of 1.0 μm can be formed. At this time, since the resin layer 4 is formed between the circuit patterns 1, the circuit patterns 1 and
1 No bridges are created between each other.

Therefore, according to the present manufacturing method, it is possible to easily manufacture a high-density and fine electronic circuit board which does not generate a bridge between the circuit patterns 1 and 1 at the time of metal plating of the Ni-Au plating layer.

In the above, the mutual interval between the circuit patterns 1 is
Although it was 50 to 60 μm, no bridge was formed in any case within this range.

Also, when the thickness of the solder plating 2 is 10 to 15 μm, the thickness of the Ni plating layer 14 is 5 to 7 μm, and the thickness of the Au plating layer 15 is 0.5 to 1.0 μm, No bridging occurred.

Second Embodiment In the method of the first embodiment, as shown in Table 1, various substrates were used, and the thickness of the electrolytic solder plating layer and the thickness of the Ni plating layer and the Au plating layer after the solder was peeled were variously changed. ,
An electronic circuit board was manufactured.

In the above substrate, the chemical copper plating layer 12 and the electrolytic Cu
The total thickness of the plating layers is 10 μm.

As is clear from Table 1, the thickness of the metal plating layer of the Ni plating layer and the Au plating layer is formed smaller than the thickness of the peeled solder layer. However, the thickness of the Ni plating layer and Au plating layer can be made larger than usual. No bridge was formed between the Ni-Au plating layers of the pattern.

[Brief description of the drawings]

1 to 13 show an embodiment of the present invention, FIG. 1 is a cross-sectional view of an electronic circuit board obtained by this embodiment, and FIGS.
The figure is a schematic view of the process of pattern plating formation, FIGS. 8 to 13 show the manufacturing process of an electronic circuit board having a metal plating layer without a bridge, FIGS. 14 and 15 show a conventional example, and FIGS. Is a sectional view of a printed wiring board, and FIG. 15 is a sectional view of a metal plating layer in the printed wiring board. 1 ... circuit pattern, 10 ... activation treatment, 11 ... copper foil, 12 ... chemical copper plating layer, 13 ... electrolytic Cu plating layer, 14 ... Ni plating layer, 15 ... Au plating layer, 16 ... Electrolytic solder plating layer, 4 ... Resin layer, 5 ... Solder resist film, 9 ... Insulated circuit board,

Claims (1)

(57) [Claims] 1. A method of manufacturing an electronic circuit board, comprising: forming a circuit pattern on an insulated circuit board, performing pattern plating using solder on the insulated circuit board, and thereafter performing etching, solder peeling, and metal plating. A method of manufacturing an electronic circuit board, comprising applying a resin to the entire surface of an insulating circuit board after etching, curing the resin, removing the surface of the resin layer to expose the solder, and then performing the solder peeling. .