JPH066031A - Method for manufacturing printed wiring board - Google Patents

Abstract

PURPOSE:To suppress the advancement of silver migration by lengthening the surface distance of a solder resist between adjacent silver jumpers. CONSTITUTION:Through holes 2 are formed on specific positions of an insulating sheet 1. Circuits 3 and lands 4 are formed on the insulating sheet 1. The circuits 3 are coated with a solder resist 5. The through holes 2 are filled up with a silver paste 6 to form silver through holes 7 whose outer surfaces are coated with a silver overcoat 8. Finally, multiple insulators 9 are formed on the silver resist 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a printed wiring board having silver through holes.

[0002]

2. Description of the Related Art Conventionally, as shown in FIGS.
As the printed wiring board, a double-sided copper clad laminated board in which copper foil is laminated on both surfaces of the insulating substrate 71 is used. A through hole 72 is formed at a predetermined position of this double-sided copper clad laminate, and a circuit 73 is formed by exposing and etching the copper foil.
By forming the land 74 and the land 74, a printed wiring board is formed. The land 74 is provided around the through hole 72, and in order to connect the lands 74 on both surfaces of the insulating substrate 71, a silver paste 75 is filled in the through hole 72 to form a silver through hole 76. Reference numeral 77 is a solder resist formed on the insulating substrate 71, and 78 is an overcoat layer deposited on the silver paste 75 in the silver through holes 76.

[0003]

In recent years, however, the pitch between adjacent silver through holes has become narrower with the increase in circuit density. As a result, silver particles in the silver through-holes permeate the overcoat layer due to the passage of current over time, and migration occurs frequently in which adjacent silver through-holes are short-circuited.

Therefore, the present invention has been developed in view of the above-mentioned drawbacks of the prior art, and is a method for manufacturing a printed wiring board in which sufficient insulation can be obtained even if the pitch of adjacent silver through holes is narrowed. For the purpose of provision.

[0005]

According to the present invention, a step of filling a through hole with a silver paste to connect between lands of a substrate and a step of forming an uneven insulating layer between adjacent silver through holes. It is a manufacturing method consisting of.

[0006]

In the present invention, the distance between the silver through holes can be increased by forming the uneven insulating layer at the narrow pitch between the silver through holes.

[0007]

Embodiment 1 FIGS. 1 to 7 show a manufacturing method of this embodiment,
FIG. 1 is a plan view, and FIGS. 2 to 7 are sectional views showing manufacturing steps. Reference numeral 1 denotes an insulating plate having copper foil on both sides, and a through hole 2 is formed at a predetermined position of the insulating plate 1 (see FIG. 2).
reference). Circuit 3 by exposing and etching the copper foil of insulating plate 1
And lands 4 are formed (see FIG. 3). Further, the circuits 3 on both sides of the insulating plate 1 are covered with the solder resist 5 (see FIG. 4). Next, the silver paste 6 is placed in the through hole 2.
To form a silver through hole 7 (see FIG. 5).
Then, the outer surface of the silver through hole 7 is covered with a silver overcoat 8 (see FIG. 6).

After the above steps, a plurality of insulators 9 having an uneven shape are formed on the solder resist 5 simultaneously with the printing of characters (see FIG. 7).

In the printed wiring board having the above structure, a plurality of insulators 9 having an uneven shape are formed on the solder resist 5, so that the distance between the adjacent silver through holes 7 on the surface of the solder resist 5 is increased. can do.

According to this embodiment, the distance between the adjacent silver through holes on the surface of the solder resist can be increased and the progress of silver migration can be suppressed.

[0011]

Embodiment 2 FIGS. 8 and 9 show this embodiment, FIG. 8 is a plan view, and FIG. 9 is a sectional view showing a manufacturing process. In this embodiment, the steps up to the step of coating the outer surface of the silver through hole 7 with the silver overcoat 8 in the first embodiment are the same steps, and the description of the same steps will be omitted.

After the above steps, an insulator 11 having a ring-shaped concavo-convex shape surrounding the silver through holes 7 is formed on the solder resist 5 at the same time when the characters are printed.

The operation and effect of this embodiment are the same as those of the first embodiment, and the description of the operation and effect will be omitted.

[0014]

As described above, according to the method for manufacturing a printed wiring board of the present invention, the distance on the surface of the solder resist between adjacent silver through holes is lengthened to suppress the progress of silver migration. As a result, the density of the circuit can be increased, and the progress of silver migration can be suppressed even when the humidity is high during the rainy season.

[Brief description of drawings]

FIG. 1 is a plan view showing a first embodiment.

FIG. 2 is a cross-sectional view showing the manufacturing process of the first embodiment.

FIG. 3 is a cross-sectional view showing a manufacturing process of the first embodiment.

FIG. 4 is a cross-sectional view showing a manufacturing process of the first embodiment.

FIG. 5 is a cross-sectional view showing the manufacturing process of the first embodiment.

FIG. 6 is a cross-sectional view showing the manufacturing process of the first embodiment.

FIG. 7 is a cross-sectional view showing a manufacturing process of the first embodiment.

FIG. 8 is a plan view showing a second embodiment.

FIG. 9 is a cross-sectional view showing the manufacturing process of the second embodiment.

FIG. 10 is a plan view showing a conventional example.

FIG. 11 is a cross-sectional view showing a conventional example.

[Explanation of symbols]

 1 Insulation Plate 2 Through Hole 3 Circuit 4 Land 5 Solder Resist 6 Silver Paste 7 Silver Through Hole 8 Silver Overcoat 9,11 Insulator

Claims (1)

[Claims] 1. A method for manufacturing a printed wiring board, comprising: a step of filling a through hole with silver paste to connect between lands of a substrate; and a step of forming an uneven insulating layer between adjacent silver through holes. .