JPH07142845A - Printed wiring board and its manufacture - Google Patents

Abstract

PURPOSE:To maintain the reliability on connection of a through hole without causing a gap where copper is exposed at the boundary between the inwall of a through hole and a solder resist even if a metallic plated layer higher in fusing point than solder is made in the through hole in the case of plugging the through hole with solder resist. CONSTITUTION:In a printed wiring board 1, where conductor circuits 6 and 7 are formed on both sides of an insulating board 2 and besides a through hole 4 to electrically connect both conductor circuits 6 and 7 is made, a nickel- plated layer 8 higher in fusing point than solder is made on the surface of the copper-plated layer 5 of the through hole 4. Moreover, a solder resist 9 to cover the conductor circuit 6 and the through hole 4 is made on one side of the insulating board 2, and a solder resist 10 not to cover the through hole 4 is made on the other side.

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 and a method for manufacturing the same, and more particularly to a printed wiring board having a high connection reliability when a through hole is sealed with a solder resist and a method for manufacturing the same. .

[0002]

2. Description of the Related Art In recent years, there has been a demand for sealing through-holes for the purpose of sucking and adsorbing a printed wiring board during solder resist printing or electrical check of a manufactured printed wiring board. The sealing of this through hole is
As shown in FIG. 4, it is realized by covering the conductor circuit 31 on one side of the insulating substrate 30 constituting the printed wiring board and one opening 32a side of the through hole 32 with the solder resist 33. The reason why the solder resist 33 covers one opening 32a side of the through hole 32 is that if both opening sides are covered, the air in the cavity of the through hole expands and the solder resist is ruptured. This is because it ends up.

A solder resist 3 is provided on the printed wiring board 30.
In order to form No. 3, there is a method of applying a liquid resin composition by a curtain coating method or a printing method, or a method of thermocompression-bonding a film-formed one. However, in the latter method, the step formed by the conductor circuit on the surface of the substrate cannot be completely followed and a gap is formed between the solder resist and the substrate, which is not preferable for the purpose of protecting the circuit. Also, the filmized material is expensive,
Not suitable for mass production. Therefore, in recent years, a method of applying a liquid resin composition as a solder resist has been preferred.

In general, when a solder resist is formed, it is exposed without being formed on the surface of a pad or the like of a printed wiring board for mounting components. Then, various pads such as nickel (Ni), nickel-gold (Ni / Au) and tin (Sn) are applied to the pad exposed from the solder resist for the purpose of improving the wettability of the solder and preventing corrosion. is there. That is, a metal having a melting point higher than that of the solder is used for these plating layers and is not melted when the mounting component is reflow-soldered on the printed wiring board.

[0005]

However, as shown in FIG. 4, when the opening 32a of the through hole 32 is sealed by the solder resist 33, the printed wiring board is dipped in a plating solution to form a pad or the like. The plating layer 34 is also formed in the through holes 32 when the plating is applied to the through holes 32.
At this time, not only the circulation of the processing liquid to the inner part of the through hole 32 is deteriorated, but also a narrow gap such that copper is exposed is formed at the boundary between the inner wall (plating layer) of the through hole 32 and the solder resist 33. Therefore, it becomes difficult to discharge the liquid from here. As a result, the treatment liquid is brought into the next process to contaminate the bath in the next process, or the treatment liquid remains at the boundary between the inner wall of the through hole 32 and the solder resist 33, causing corrosion of the through hole 32. There is a problem.

Further, when acid such as soft etching remains in the gap where the copper is exposed at the boundary between the inner wall of the through hole 32 and the solder resist 33, the inside of the through hole 32 is corroded, causing a disconnection. There is a fear. Therefore, if the through hole 32 is sealed, there is a problem that the connection reliability is lowered.

The present invention has been made in order to solve the above-mentioned problems, and the purpose thereof is to seal a through hole with a solder resist so that a plated layer of a metal having a melting point higher than that of solder is provided in the through hole. A printed wiring board capable of maintaining connection reliability of a through hole without forming a copper-exposed gap at the boundary between the inner wall of the through hole and the solder resist even when the wiring board is formed, and a method of manufacturing the same. To provide.

[0008]

In order to solve the above problems, according to the invention of claim 1, conductor circuits are formed on both surfaces of an insulating substrate, and through holes for electrically connecting both conductor circuits are formed. In the printed wiring board, a plated layer of a metal having a melting point higher than that of solder is formed on the surface of the through hole, a solder resist covering the conductor circuit and the through hole on one surface of the insulating substrate, and the other surface. Solder resists that do not cover the through holes are formed on the respective.

Further, in the manufacturing method according to the second aspect, through holes for electrically connecting the conductor circuits formed on both surfaces of the insulating substrate are formed, and then the first solder resist not covering the through holes is formed. After forming on both surfaces of the substrate and plating a metal having a higher melting point than solder, a second solder resist was formed on the insulating substrate so as to cover one opening side of the through hole.

[0010]

According to the invention of claim 1, since the plated layer of the metal having a melting point higher than that of the solder is formed on the surface of the through hole, copper is not formed on the boundary between the inner wall of the through hole and the solder resist. No exposed gap is formed.
As a result, when the through hole is sealed with the solder resist, the plating treatment liquid does not remain in the through hole, and the connection reliability of the through hole is maintained. Further, since the plating thickness formed on the inner wall of the through hole becomes uniform, it is possible to improve the conduction reliability of the through hole and reduce the conduction resistance.

According to the manufacturing method of the second aspect,
Through holes for electrically connecting the conductor circuits formed on both surfaces of the insulating substrate are formed. Next, a first solder resist that does not cover the through hole is formed on both sides of the substrate, and a plating process of a metal having a melting point higher than that of solder is performed. It is formed so as to cover the opening side. Therefore, when the pad or the like forming the conductor circuit is plated, the treatment liquid is not brought into the next step to contaminate the bath or the treatment liquid remains in the through hole.

[0012]

EXAMPLE 1 Example 1 embodying the present invention will be described below with reference to FIGS.

As shown in FIG. 1, the printed wiring board 1 includes an insulating substrate 2, and lands 3 are formed on both surfaces of the insulating substrate 2. Both lands 3 are electrically connected to each other through a copper plating layer 5 of a through hole 4 formed by penetrating the insulating substrate 2. Each land 3 is an insulating substrate 2.
Are electrically connected to the conductor circuits 6 and 7 formed on both surfaces of each.

A nickel (Ni) plating layer 8 is formed on the surfaces of the copper plating layer 5 of the through hole 4 and both lands 3. Further, solder resists 9 and 10 are formed on both surfaces of the insulating substrate 2. The solder resist 9 on one side is the opening 4 of the conductor circuit 6 and one of the through holes 4.
It is formed so as to cover the a side.

In this printed wiring board 1, a nickel plating layer 8 is formed on the copper plating layer 5 of the through hole 4 and the land 3.
Therefore, a gap for exposing copper is not formed at the boundary between the plating layer 5 and the solder resist 9 on the inner wall of the through hole 4. As a result, the plating treatment liquid does not remain on the plating layer 5, and the connection reliability of the through hole 4 can be maintained. Further, since the nickel plating layer 8 is formed on all surfaces of the plating layer 5 of the through hole 4, the thickness thereof becomes uniform,
It is possible to improve the conduction reliability of the through hole 4 and reduce the conduction resistance.

Next, a method of manufacturing the printed wiring board 1 configured as described above will be described. The conductor circuits 6 and 7 are formed on both surfaces of the insulating substrate 2 by a conventional method, and the through holes 4 for electrically connecting the conductor circuits 6 and 7 on both sides are formed on the insulating substrate 2. Next, the printed wiring board 1 is dipped in a nickel plating solution to perform electrolytic nickel plating,
A nickel plating layer 8 is formed on the surfaces of the conductor circuits 6 and 7, the plating layer 5 of the through hole 4 and the land 3 (FIG. 2).
At this time, since the openings of the through holes 4 are not covered with the solder resist, the flow of the plating solution is improved and all the plating layers 5 are plated. Therefore, after the immersion treatment, the treatment liquid is not brought into the next step to contaminate the bath or the treatment liquid does not remain in the plating layer 5.

Next, solder resists 9 and 10 are formed on both surfaces of the insulating substrate 2 so as to cover the conductor circuits 6 and 7 and one opening 4a side of the through hole 4 (FIG. 1). In this way, the printed wiring board 1 having the through holes 4 sealed by the solder resist 9 is obtained.

(Second Embodiment) Next, a second embodiment will be described. In this embodiment, the solder resist covering the insulating substrate 2 on the side of the opening 4a of the through hole 4 has a two-layer structure.

As shown in FIG. 3, the solder resist is the first solder resist 12a, 1 which covers the conductor circuits 6, 7.
2b, and one of the first solder resist 12a and the second solder resist 13 that covers the opening 4a side of the through hole 4. The first solder resists 12a and 12b are made of a material having sufficient resistance to the nickel plating solution.

Printed wiring board 1 constructed as described above
In order to manufacture, the first solder resists 12a and 12b are formed on both surfaces of the insulating substrate 2 on which the conductor circuits 6 and 7 and the through holes 4 are formed so as to cover the conductor circuits 6 and 7. Next, the printed wiring board 1 is dipped in a nickel plating solution to perform electrolytic nickel plating, and the through holes 4 are formed.
Nickel plating layer 8 on the surface of plating layer 5 and land 3
To form. Next, the second solder resist 13 is formed on one surface of the insulating substrate 2 so as to cover the first solder resist 12a and the through hole 4 so as to cover one opening 4a side thereof.

As described above, in the printed wiring board 1 according to the second embodiment, the first solder resists 12a, 12 are used.
Since the nickel plating layer 8 is formed in the through hole 4 after the conductor circuits 6 and 7 are covered with b, the portion where the nickel plating layer 8 is formed can be reduced and the plating cost can be reduced. it can.

The present invention is not limited to the above embodiments, but may be modified as follows without departing from the gist of the present invention. (1) In the first and second embodiments, the nickel plating layer 8 is formed on the through hole 4 or the conductor circuits 6 and 7, but instead, nickel-gold (Ni / A) having a melting point higher than that of solder is used.
u) A plated layer, a tin (Sn) plated layer or the like may be formed.

(2) In the second embodiment, the second solder resist 13 is formed on only one side of the insulating substrate 2, but it may be formed on both sides. By thus forming the second solder resist 13, it is possible to prevent the printed wiring board 1 from warping.

(3) The present invention may be applied not only to the printed wiring board 1 having conductor circuits 6 and 7 formed on both sides but also to a multilayer printed wiring board having conductor circuits on the inner layer. (4) The first solder resist 12a in FIG.
It is desirable to form so as to cover a part of the land 3. This is because it is difficult to sufficiently form the nickel plating layer 8 to the lower part of the outer peripheral edge of the land 3.

[0025]

As described in detail above, in the printed wiring board according to the first aspect of the present invention, when the through hole is sealed with the solder resist, the through hole is plated with a metal having a melting point higher than that of the solder. Even if a layer is formed, there is no gap such that copper is exposed at the boundary between the inner wall of the through hole and the solder resist, and it is possible to maintain the connection reliability of the through hole. .

In the invention described in claim 2, the method is suitable for manufacturing the printed wiring board.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a main part of a printed wiring board according to a first embodiment of the present invention.

FIG. 2 is likewise a schematic cross-sectional view of an essential part showing a state in which a conductor circuit and through holes of Example 1 are plated.

FIG. 3 is a schematic cross-sectional view of essential parts showing a printed wiring board according to a second embodiment.

FIG. 4 is a schematic cross-sectional view of essential parts showing a conventional printed wiring board.

[Explanation of symbols]

1 ... Printed wiring board, 2 ... Insulating substrate, 3 ... Land, 4 ...
Through hole, 4a ... Opening, 5 ... Plating layer, 6, 7 ...
Conductor circuit, 8 ... Nickel plated layer, 9, 10 ... Solder resist, 12a, 12b ... First solder resist,
13 ... Second solder resist.

Claims (2)

[Claims] 1. A conductor circuit is formed on both surfaces of an insulating substrate,
And in a printed wiring board in which a through hole that electrically connects both conductor circuits is formed, a plated layer of a metal having a melting point higher than that of solder is formed on the surface of the through hole, and one surface of the insulating substrate is formed. A printed wiring board, wherein a solder resist that covers the conductor circuit and the through hole and a solder resist that does not cover the through hole are formed on the other surface. 2. A through hole for electrically connecting conductor circuits formed on both surfaces of an insulating substrate is formed, and then a first solder resist that does not cover the through hole is formed on both surfaces of the substrate. A method of manufacturing a printed wiring board, characterized in that a second solder resist is formed on the insulating substrate so as to cover one opening side of the through hole after a plating process of a high metal is performed.