JPH06125164A - Through hole printed wiring board - Google Patents

Abstract

PURPOSE:To enable enhancement of reliability despite of low cost by preventing an edge of a through hole mounting no components out of through holes in a through hole printed wiring board from corroding/discontinuing and from developing bridges and balls caused by solder blow through. CONSTITUTION:A through hole 3 mounting no components is blocked in a sealed state with a cured part 4A of a resist liquid for solder resist printing used to form an insulative layer 4 and a cured part 5A of a marking printing ink used to form a display 5 such as letters.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is incorporated in an electronic device such as a portable radio and a personal computer in order to make the electronic device lighter, thinner and smaller, and is used in an electronic device such as an IC or a transistor, a resistor or a capacitor. A printed circuit board by mounting electronic components or other components (hereinafter referred to as components) at predetermined positions and soldering their lead wires or terminals to lands that are part of the conductive pattern. The present invention relates to a through-hole printed circuit board that constitutes a.

[0002]

2. Description of the Related Art FIG. 4 is a front view showing an example of a conductive pattern in a through-hole printed wiring board made of a copper through-hole double-sided board. In FIG. A conductive pattern portion 2 made of a copper foil as a material and a large number of through hole holes 3 having an inner wall plated with copper are formed based on electrical design. Reference numeral 4 is an insulating layer formed by solder resist printing (or coating), and 5 is various display marks such as characters formed by marking printing (silk printing).

Of the methods of manufacturing a through-hole printed wiring board as in the above example, the steps of the subtractive method, which is generally used conventionally for mass production, will be briefly described with reference to FIGS. 5 and 6. First, the double-sided copper clad laminate 1A as a material is cut into a predetermined shape and size.
Through hole 3 using process, NC multi-axis drilling machine, etc.
2nd step of opening, 3rd step of forming electroless copper plating 6 thinly, 4th step of forming electrolytic copper plating 7, 5th step of sticking a photosensitive thin film, that is, dry film 8 on the entire surface, conductive pattern Sixth step of forming an etching resist film 9 by exposing only a portion to light and then developing and fixing, an edging resist film 9 by spraying an etching solution on the copper foil surface.
It is composed of a seventh step of dissolving and removing the copper foil other than the conductive pattern portion 2 covered with, and an eighth step of exposing the conductive pattern portion 2 by peeling and removing the edging resist film 9 with a chemical. .

After the above process, a solder resist printing process for forming the insulating layer 4 and the display mark 5 are performed.
An outer layer forming step such as a marking printing step for forming a layer is performed. In a through-hole printed wiring board manufactured through such steps, conventionally, as a rust preventive measure for the conductive pattern portion 2, solder plating for covering the entire surface of the conductive pattern 2 with nickel or gold is performed. Was there.

[0005]

However, in the conventional through-hole printed wiring board as described above, components are not attached to all the through-holes 3, and for example, the portion surrounded by the dotted line in FIG. Only, the components are attached by flow or reflow soldering, and the other components are not mounted. In view of such a situation, the conventional product in which the entire surface of the conductive pattern 2 is solder-plated with nickel or gold, including the parts where the components are not mounted, causes a cost increase due to an increase in the material cost and the number of manufacturing steps. Inevitable.

Further, when the solder plating which causes the cost increase as described above is omitted, the conductive pattern portion 2 where the components are not mounted is exposed as the copper foil. Therefore, even if the insulating layer 4 formed by the solder resist printing is present, as shown in FIG. 7, the edge portion 3a of the through hole 3 is exposed early due to the influence of moisture or temperature change, There is a problem of causing corrosion and disconnection. Further, when the components P are attached by the flow or reflow soldering, as shown in FIG. 8, the solder a is blown out from the through hole 3 where the components P are not mounted to form the bridge b with the conductive pattern portion 2. There is a problem that a defective situation such as the occurrence of a solder ball c is likely to occur.

The present invention has been made in view of the above-mentioned circumstances, and it is possible to reduce the cost without solder plating of nickel or gold on the entire surface of the conductive pattern, but to prevent corrosion, disconnection, It is an object of the present invention to provide a through-hole printed wiring board that can reliably prevent generation of bridges and solder balls and maintain high reliability for a long period of time.

[0008]

In order to achieve the above object, a through-hole printed wiring board according to the present invention comprises:
In a through-hole printed wiring board in which a large number of through-holes are formed in an electrically insulating substrate on which a conductive pattern is formed, among the above-mentioned through-holes, the through-holes not mounting components are solder resist printing resists. The liquid is clogged with a liquid and a marking printing ink.

Particularly, the conductive pattern is formed on both front and back surfaces of an electrically insulating substrate, and is applied to a wiring board comprising a copper through-hole double-sided plate in which the inner wall of each through-hole is plated with copper. It is valid.

[0010]

According to the present invention, through-holes not mounting components are used not only for the resist solution for solder resist printing, but also for marking printing for displaying various characters on the substrate surface. By blocking with the ink, even if the entire surface of the conductive pattern is not subjected to surface treatment that causes cost increase such as solder plating with nickel or gold etc. Not only can it be exposed to prevent corrosion and disconnection due to the effects of humidity and temperature, but also
When the components are attached by the flow or reflow soldering, the solder does not blow out from the through-hole holes where the components are not mounted, and the generation of bridges or solder balls can be prevented.

In particular, when applied to a printed circuit board composed of a copper through-hole double-sided board, the through-holes not mounting the components are completely closed by a resist liquid for solder resist printing and an ink for marking printing to be hermetically sealed. Therefore, it is possible to completely eliminate the above-mentioned corrosion, disconnection, bridge and solder ball generation, and to secure the reliability as a substrate.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an enlarged vertical cross-sectional view of a main part of a through-hole printed wiring board made of a copper through-hole double-sided board according to an embodiment of the present invention other than the part surrounded by the dotted line in FIG. In the figure, since 1 to 3 are the same as the conventional example shown in FIG. 7, the same reference numerals are given to corresponding parts, and the description thereof will be omitted. In FIG. 1, 3A is all through hole holes 3
It is the copper plating on the inner wall of the. The manufacturing method of this through-hole printed wiring board is as shown in FIGS.
Since it is the same as that already described with reference to, the description thereof will be omitted here.

In FIG. 1, among the through-holes 3, the through-holes 3 in which components are not mounted are formed in the through-holes 3 at the time of printing a solder resist for forming the insulating layer 4 on the conductive pattern 2. Hardened resist portions 4A, 4A obtained by hardening the resist liquid flowing from both front and back sides at the entrance portion, and markings for forming various display marks 5 such as characters on the front and back surfaces of the insulating substrate 1 at the time of printing. It is completely closed by the cured ink portion 5A in which the printing ink is made to flow and cured. As a blockage processing pattern for such a through-hole hole 3, as shown by the phantom lines in FIGS. ) To (E), as shown by the phantom lines, a pattern in which a plurality of through-holes 3 are collectively processed may be used.

FIG. 3 is an enlarged vertical sectional view of an essential part of a single-sided printed wiring board in which the conductive pattern 2 is formed only on one surface of the insulating substrate 1. In this case, no components are mounted. Of the total depth of the through-holes 3, it is only necessary to block about half the depth on the surface side where the conductive pattern 2 is formed with the cured resist portion 4A and the cured ink portion 5A.

In the above embodiment, the subtractive method is adopted as the method of manufacturing the through-hole printed wiring board, but the additive method or the semi-additive method may be adopted.

[0016]

As described above, according to the present invention, through-holes in which components are not mounted are provided for displaying the resist liquid for solder resist printing and various characters on the substrate surface. By blocking with the ink for marking printing, parts of the through-hole that are not mounted without the surface treatment that causes cost increase such as solder plating with nickel or gold on the entire surface of the conductive pattern In particular, it not only prevents the edges from being exposed and prevents corrosion and disconnection due to the effects of moisture and temperature, but also when mounting components by flow or reflow soldering, solder from the through-hole holes where components are not mounted. It is possible to prevent the generation of bridges and solder balls due to the blowout. Therefore, cost reduction can be achieved by reducing the solder plating material and omitting the process, but it is possible to reliably prevent corrosion, wire breakage, bridges, solder balls, etc., and maintain high reliability for a long time. There is an effect that can be made.

[Brief description of drawings]

FIG. 1 is an enlarged vertical cross-sectional view of a main part of a through-hole printed wiring board including a copper through-hole double-sided board according to an embodiment of the present invention.

FIGS. 2A to 2E are schematic plan views showing examples of through-hole blocking processing patterns.

FIG. 3 is an enlarged vertical sectional view of a main part of a single-sided printed wiring board according to another embodiment of the present invention.

FIG. 4 is a front view showing an example of a conductive pattern in a through-hole printed wiring board including a copper through-hole double-sided plate.

FIG. 5 is a flow sheet showing steps of a subtractive method, which is one method of manufacturing a through-hole printed circuit board.

6 is a vertical cross-sectional view of the main part along the process of FIG.

FIG. 7 is an enlarged vertical cross-sectional view of a main part of a through-hole printed wiring board including a conventional copper through-hole double-sided plate.

FIG. 8 is a schematic cross-sectional view illustrating a defect of a conventional through hole printed wiring board.

[Explanation of Codes] 1 Electrical Insulating Substrate 2 Conductive Pattern 3 Through Hole Hole 4 Insulating Layer 4A Cured Resist Part 5 Indication Mark 5A Cured Ink Part

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[Procedure amendment]

[Submission date] April 1, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

Claims (2)

[Claims] 1. In a through-hole printed wiring board in which a large number of through-holes are formed in an electrically insulating substrate on which a conductive pattern is formed, among the through-holes, the through-holes not mounting components are solder. A through-hole printed wiring board, which is capped with a resist liquid for resist printing and an ink for marking printing. 2. The through hole print according to claim 1, wherein the conductive pattern is formed on both front and back surfaces of an electrically insulating substrate, and comprises a copper through hole double-sided plate having copper plated inside walls of the through holes. Wiring board.