JP2570174B2 - Multilayer printed wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer printed wiring board, and more particularly to a multilayer printed wiring board used for detecting a resistance smear generated in a multilayer printed wiring board.

[0002]

2. Description of the Related Art A conventional multilayer printed board is shown in FIG.
As shown in (B), the base material 7 has an outer layer land 3 formed around the through holes 4 on both surfaces of the base material 7 and an inner layer land 5 formed inside the base material 7. The through holes 4 are connected at predetermined positions by a through hole plating layer 9.

[0003] In the multilayer printed wiring board thus configured, when performing interlayer connection, a through-hole is drilled by drilling, and then a through-hole plating layer 9 is formed by copper plating. 5 (A),
As shown in FIG. 3B, the surface of the inner wall 5 of the hole wall is exposed to the melt coating by melting coating, thereby reducing the connection area between the through-hole plating layer 9 and the inner land 5 and soldering for mounting the component. Connection failure was caused by thermal shock or the like in the process.

As described above, the resistance smear 10 generated at the connection portion between the inner land 5 and the through-hole plating layer 9 of the multilayer printed wiring board cannot be detected from the outer layer surface of the multilayer printed wiring board. Therefore, first, the multilayer printed wiring board is destroyed and cut from the front surface or the back surface to the target inner layer to expose the inner layer land 5. Next, the connection portion between the inner layer land 5 and the through-hole plating layer 9 is observed using a measuring instrument such as a magnifying glass, and when the resistance smear 10 is recognized, the length is measured.
The non-defective product and the defective product were determined based on the criterion described in 3.9.2 of item 4 (the tolerance of the resistance smear was 25% or less of the hole circumference).

[0005]

In the conventional method for detecting a resist smear, the multilayer printed wiring board is destroyed and cut down to the inner layer land to measure the length of the resist smear, and the inspection is performed. There was a problem that it was necessary. For this reason, there has been a problem that the delivery date of the product is hindered.

SUMMARY OF THE INVENTION An object of the present invention is to provide a multilayer printed wiring board having an inspection pattern capable of easily inspecting a resistance smear, requiring no man-hour and a schedule, and shortening a delivery time.

[0007]

SUMMARY OF THE INVENTION A multilayer printed wiring board according to the present invention comprises a through hole for detecting a resistance smear, and a radially outward connection at an equal angle around the through hole for detecting a resistance smear. It has an extending inner layer pattern, an inner layer land connected to the terminal end of the inner layer pattern, and a through-hole or a non-through through hole for an outer layer connected to the inner layer land.

[0008]

Next, embodiments of the present invention will be described with reference to the drawings.

FIGS. 1A and 1B are a plan view and a sectional view taken along line AA 'of a first embodiment of the present invention. The first embodiment of the present invention, as shown in FIGS.
In a region other than the circuit forming portion, through holes 4 for detecting the resistance smear and through holes 2a to 2h are provided at radial positions at equal angles around the through holes 4, and the through holes 2a to 2h are formed on the inner layer surface. Inner layer land 5a ~
5 h (not shown) are arranged, and the inner layer lands 5 a to 5 h are connected to the through holes 4 by the inner layer pattern 6.
At this time, no inner layer land is provided in the through hole 4. On the other hand, an outer layer land 1 connected to each of the through holes 2a to 2h and an outer layer land 3 connected to the through hole 4 are arranged on the outer layer surface.

FIGS. 2A and 2B are plan views of a film for manufacturing an outer layer pattern and an inner layer pattern based on design criteria, respectively. Assuming that the circuit forming capability of the multilayer printed wiring board has a circuit width of 0.1 mm and a circuit interval of 0.15 mm, the minimum hole diameter of the through hole 4 for detecting the resistance smear in which the inner layer circuits can be arranged in eight directions is expressed by the following equation.

[(Circuit width + circuit interval) × the number of directions] / pi = [(0.1 + 0.15) × 8] /3.14 Therefore, the diameter of the through hole 4 for detecting the resistance smear is:
With the diameter of the through hole larger than this calculated value, it is set based on the diameter of the through hole that is used in the product and to check for the occurrence of the resistance smear. Establish the minimum hole diameter according to.

On the other hand, through hole 4 and through hole 2a
The minimum interval of ２2h is represented by the following equation.

(Diameter of outer layer land 3 + diameter of outer layer land 1)
First, an inner land 5 and an inner layer pattern 6 are formed at predetermined positions of an inner layer using a film for manufacturing an inner layer pattern shown in FIG. 2B created based on the above-described design criteria, and a prepreg is formed. The base material having a copper foil on one side is stacked on the substrate and a laminate is formed by a known thermocompression bonding means. Next, the outer layer pattern 1 is moved to the position where the center of the outer layer land 3 intersects the inner layer pattern 6 using the film for manufacturing an outer layer pattern shown in FIG. An outer layer pattern is formed at a position corresponding to the above. Next, after drilling holes for through holes at the centers of the outer layer lands 3 and 1, through a plating step, the through holes 4 are connected to the inner layer patterns 6, and the through holes 4 are respectively formed through the inner layer patterns 6. Through holes 2a to 2h to be connected
Then, solder resist, character printing, and outer diameter processing are performed.

Next, in the electrical inspection step, the connection with the through holes 2a to 2h is inspected with reference to the through hole 4. At this time, the through hole 4 and the through holes 2a to 2h
When all are in the conductive state, no resistance smear occurs and the through hole 4 is in the state shown in FIGS. 4A and 4B. On the other hand, if only the through-hole 2a is broken, it indicates that a resistance smear has occurred in that portion, and it can be said that the length of the resistance smear is 25% or less of the circumference of the through-hole 4. The state of the through hole 4 at this time is shown in FIG.
(A) and (B). Also, through hole 2a
2b is disconnected, the length of the resistance smear can be said to be 25% or more and 37.5% or less of the circumference of the through hole 4.

FIG. 3 is a sectional view of a second embodiment of the present invention. In the second embodiment, as shown in FIG. 3, a non-penetrating srule 8 is formed in two layers instead of the through-hole 2 of the first embodiment, and an electrical inspection is performed from both sides. Therefore, the inspection pattern is provided in the same area as that of the first embodiment, and it is possible to correspond to a four-layer multilayer printed wiring board.

[0016]

As described above, according to the present invention, a through-hole for resistance smear inspection is provided, an inner layer pattern is provided radially around the through-hole, and a through-hole with the outer layer is provided at the end of the inner layer pattern. Accordingly, there is an effect that the presence or absence of the occurrence of the resistance smear and the size thereof can be easily detected without breaking the multilayer printed wiring board in the electrical inspection process.

In addition, since the inspection is performed in the electrical inspection process, the number of man-hours for inspection of the resistance smear, which has been conventionally performed, is not required, which contributes to shortening the delivery time of the product.

[Brief description of the drawings]

FIGS. 1A and 1B are a plan view and a sectional view taken along line AA ′ of a first embodiment of the present invention.

FIGS. 2A and 2B are plan views of a film for manufacturing an outer layer pattern and an inner layer pattern based on design standards, respectively.

FIG. 3 is a sectional view of a second embodiment of the present invention.

FIGS. 4A and 4B are a plan view of an example of a through hole of a conventional multilayer printed wiring board and a cross-sectional view taken along line BB 'of FIG.

FIGS. 5A and 5B are a plan view for explaining an example of a resistance smear of a conventional multilayer printed wiring board, and FIGS.
It is C 'line sectional drawing.

[Explanation of symbols]

 1,3 outer layer land 2,2a-2h, 4 through hole 5 inner layer land 6 inner layer pattern 7 base material 8 non-through through hole 9 through hole plating layer 10 resistance smear

Claims (3)

(57) [Claims] 1. A through hole for detecting a resistance smear, an inner layer pattern connected to the through hole for detecting a resistance smear and extending radially outward at an equal angle around the through hole for detecting a resistance smear, and connected to a terminal end of the inner layer pattern. A multilayer printed wiring board comprising: an inner layer land to be formed; and a through hole connected to the inner layer land. 2. The multilayer printed wiring board according to claim 1, wherein the through hole connected to the inner layer land is a through hole with the outer layer. 3. The multilayer printed wiring board according to claim 1, wherein the through hole is a non-through through hole with an outer layer.