JPH066004A - Printed wiring board - Google Patents

Abstract

(57) [Abstract] [Purpose] To increase the distance on the surface of the solder resist between adjacent silver through-holes and suppress the progress of silver migration. [Structure] A through hole 2 is formed at a predetermined position of an insulating plate 1, and a circuit 4 covered with a solder resist 3 is formed on both front and back surfaces thereof. In order to connect the lands 5 on both sides of the through hole 2, a silver paste 6 is filled in the through hole 2 to form a silver through hole 7. A silver overcoat 8 on the outer surface of the silver through hole 7.
Are covered. A plurality of insulators 9 having an uneven shape are formed on the solder resist 3.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, as shown in FIGS. 5 and 6, a double-sided copper-clad laminate in which copper foil is laminated on both sides of an insulating substrate 71 is used as a printed wiring board. A through hole 72 is formed at a predetermined position of this double-sided copper clad laminate, and a circuit 73 and a land 74 are formed by exposing and etching the copper foil to form a printed wiring board. 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 was developed in view of the above-mentioned drawbacks of the prior art, and an object thereof is to provide a printed wiring board which can obtain sufficient insulation even if the pitch of adjacent silver through holes is narrowed. And

[0005]

The present invention is a printed wiring board in which silver through holes are formed, wherein an insulating layer having an uneven shape is formed between the adjacent silver through holes.

[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 and 2 show this embodiment, FIG. 1 is a sectional view, and FIG. 2 is a plan view. Reference numeral 1 denotes an insulating plate, through holes 2 are formed in a predetermined position of the insulating plate 1, and a circuit 4 covered with a solder resist 3 is formed on both front and back surfaces thereof. Lands 5 are provided on both sides of the through hole 2, and silver paste 6 is filled in the through holes 2 to connect the lands 5 on both sides to form silver through holes 7. An outer surface of the silver through hole 7 is covered with a silver overcoat 8. On the solder resist 3 between the silver through holes 7 adjacent to each other, a plurality of insulators 9 having an uneven shape are formed.

In the printed wiring board having the above structure, the plurality of insulators 9 having an uneven shape are formed on the solder resist 3, so that the distance between the adjacent silver through holes 7 on the surface of the solder resist 3 is increased. can do.

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

[0010]

Embodiment 2 FIGS. 3 and 4 show this embodiment, FIG. 3 is a sectional view, and FIG. 4 is a plan view. In this embodiment, the insulator 9 on the solder resist 3 in the first embodiment is eliminated,
Instead, it is configured by a ring-shaped insulator, and other configurations are composed of the same constituent parts, and the same constituent parts are designated by the same reference numerals and the description thereof will be omitted. In this embodiment, an insulator 11 having an annular uneven shape surrounding the silver through hole 7 is formed on the solder resist 3.

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.

[0012]

As described above, according to the printed wiring board of the present invention, the distance between the adjacent silver through holes on the surface of the solder resist 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 cross-sectional view showing a first embodiment.

FIG. 2 is a plan view showing the first embodiment.

FIG. 3 is a cross-sectional view showing a second embodiment.

FIG. 4 is a plan view showing a second embodiment.

FIG. 5 is a cross-sectional view showing a conventional example.

FIG. 6 is a plan view showing a conventional example.

[Explanation of symbols]

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

Claims (1)

[Claims] 1. A printed wiring board in which silver through holes are formed, wherein an uneven insulating layer is formed between the adjacent silver through holes.