JPH0621623A - Method for processing solder resist in manufacture of printed wiring board - Google Patents

Abstract

PURPOSE:To easily clean up etchant without closing a VIA hole at the time of cleaning up etchant by forming a solder resist layer on both front and rear surface of a base member and then applying surface roughing treatment to an electronic parts mounting position with etchant. CONSTITUTION:Copper plating 3 is applied to the inner wall of a number of VIA holes 2 extending through an insulating base member 1, thereby interconnecting the wiring circuits on the outer and the inner layer formed on the front and the rear surface of the base member 1 in a printed wiring board. When solder resist treatment is performed in the finishing process of manufacturing processes for such a printed wiring board, first of all, surface roughing treatment is performed with etchant after a solder resist layer 4 is so formed on the surface of the base member 1 as not to close the VIA holes. And after the electronic parts mounting position on the surface to which the surface roughing treatment is applied is coated with solder, the VIA holes 2 are closed with a solder resist film 5, and after the printed wiring board is so processed that it can be fixed by sucking, it is transferred to an electrical inspection process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a finishing process for manufacturing a printed wiring board having at least two layers of wiring circuits and VIA holes for conducting these wiring circuits.
The present invention relates to a solder resist processing method in the production of a printed wiring board in which a solder resist layer is formed on the surface of the printed wiring board.

[0002]

2. Description of the Related Art A printed wiring board is formed by laminating a double-sided printed wiring board having wiring circuits made of copper foil, copper plating, etc. on both sides of a plate-like insulating base material or a wiring circuit layer of three or more layers. There is a multilayer printed wiring board having a wiring circuit in the inner layer of the printed wiring board. And these printed wiring boards
A VIA hole for connecting the wiring circuits of a plurality of layers to each other is formed.

The VIA hole has a through hole formed in the insulating base material, an inner wall of the through hole is metal-plated, and the metal plating is connected to the wiring circuit of each layer to form a wiring circuit of a different layer. The circuits are electrically connected to each other to form one circuit.

During the finishing operation in the production of such a printed wiring board, the wiring circuit formed on the surface of the insulating base material is protected, and at the time of mounting electronic parts, the soldering of the printed wiring board is carried out. SR that forms a solder resist (hereinafter sometimes abbreviated as SR) layer made of an insulating resin on the surface of the printed wiring board in order to prevent the wiring circuit from short-circuiting due to the adhesion of solder to unnecessary parts There are processing steps. In this SR processing step, the SR layer is not formed on the terminal portion of the printed circuit board surface where the electronic component of the wiring circuit is mounted.

Conventionally, the above-mentioned finishing work is carried out by the SR treatment step and then by lightly etching the surface of the wiring circuit exposed from the SR layer to form a wiring circuit for solder coating (hereinafter abbreviated as SC) described later. In order to improve the solderability between the electronic parts and the wiring circuit terminals and to protect the wiring circuit exposed from the SR layer, a surface roughening process for cleaning and roughening the copper surface to be formed is performed. The SC step of coating the surface of the wiring circuit exposed from the layer with solder.

Further, after the SC process, there is an inspection process such as an electrical inspection for inspecting the wiring circuit for disconnection or short circuit. In the electrical inspection, a constant voltage is applied between the terminals of the wiring circuit of the printed wiring board, and the conduction and insulation states are inspected by the resistance value. At the time of this electrical inspection, by sucking the printed wiring board, the terminals are brought into close contact with a test probe that applies a voltage to each terminal of the wiring circuit,
A voltage is applied to the wiring circuit.

During the electrical inspection, if the VIA hole penetrates the printed wiring board, air will pass through the VIA hole, and the insulating base material will be sucked into the test probe to cause the terminal to contact the terminal. Since it is difficult to adhere the SR layer to the surface of the insulating substrate,
SR at the opening on one side of the VIA hole on the surface of the insulating substrate
Film is formed to close the VIA hole.

The method of covering the VIA hole with the SR film in this way is called a tenting method.

[0009]

By the way, as described above, when the SR film is formed on the one-side opening of the VIA hole when the SR layer is formed on the insulating base material, the VIA is not formed. Since the bottom of the SR film is formed in the hole, when cleaning the etching solution used in the surface roughening step, the cleaning solution is applied from the one surface side of the insulating substrate to the other surface V
You cannot pass through the IA hall. That is, SR
Due to the tenting of the film, the etching solution entering the VIA hole becomes difficult to clean.

When a part of the etching solution remains in the VIA hole, the metal plating on the inner wall of the VIA hole may be damaged by the etching solution, resulting in a defective conduction in the VIA hole.

The present invention has been proposed in view of the above circumstances, and an object of the present invention is to prevent the etching solution from remaining in the VIA hole during the surface roughening step and to improve the reliability of the printed wiring board. It is an object of the present invention to provide a solder resist treatment method in the production of a printed wiring board that can improve the property.

[0012]

A solder resist treatment method in the production of a printed wiring board according to the present invention comprises a wiring circuit formed on at least both front and back surfaces of a plate-shaped insulating base material and the insulating base material. In the manufacturing process of a printed wiring board, which penetrates and has through holes having metal plating formed on the inner wall so as to connect the wiring circuits to each other, in the manufacturing process of a printed wiring board in which electronic components are mounted on the wiring circuit, the wiring A solder resist layer is formed on both front and back surfaces of an insulating base material on which circuits and through holes are formed, and both front and back surfaces of an insulating substrate excluding the openings of the through holes and mounting parts for electronic components of the wiring circuit. A resist forming step of forming a solder resist layer, and then a roughening step of etching the mounting portion of the electronic component of the wiring circuit to roughen the surface.
After the roughening step, a closing step of forming a solder resist film at the opening of the through hole and closing the solder resist film is provided.

[0013]

According to the above structure, in the resist forming step, the through hole is not blocked by the SR film, and the surface roughening step using the etching solution is performed in a state where the through hole is not blocked, and thereafter, The opening of the through hole is closed by the SR film. Therefore, when cleaning the etching solution after etching in the roughening step, the cleaning solution can pass through the through holes, and the etching solution can be easily cleaned.

Further, since the through hole is closed by the SR film in the closing step, the terminals of the wiring circuit on the surface of the printed wiring board are brought into close contact with the test probe by sucking the printed wiring board during the electrical inspection. When V
No air leaks from the IA hole.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 to 3 are drawings for explaining a solder resist processing method in manufacturing a printed wiring board according to this embodiment, and FIGS. 1 and 2 show positions of VIA holes 2 in an insulating base material 1 described later. FIG. 3 is a flow chart of the solder resist processing method.

The printed wiring board is a well-known multi-layered printed wiring board, and wiring circuits (not shown) are formed on the outer layers on both front and back surfaces of the plate-shaped insulating base material 1, and the board-shaped printed wiring board is formed. A wiring circuit (not shown) is also formed on the inner layer of the insulating base material 1. Then, as shown in FIGS. 1 and 2, in the insulating base material 1, a number of VIA holes penetrating the insulating base material 1 (in FIG. 1 and FIG. 2, one VIA hole of the insulating base material 1 is used). A hole 2 is shown in an enlarged manner to form a portion 2.

Copper plating 3 is applied to the inner wall of the VIA hole 2. The VIA hole 2 connects the copper plating 3 on the inner wall thereof to the wiring circuits of the outer layer and the inner layer so that the wiring circuits are electrically connected to each other.

The solder resist treatment of this embodiment is carried out as a finishing step after the formation of the wiring circuit on the insulating base material 1 and the formation of the VIA hole 2 are completed in the production of the printed wiring board. Is.

Then, as shown in FIG. 3, according to the solder resist treatment method, the SR layer 4 is formed on both front and back surfaces of the insulating base material 1.
And a component marking (abbreviated as CM) printing step S2 for printing an abbreviation of an electronic component (not shown) or the like on the SR layer 4 formed in the resist forming step S1. The roughening step S3 of roughening the surface of the portion of the wiring circuit outside the insulating base material 1 exposed from the SR layer 4 with an etching solution, and the wiring circuit roughened in the roughening step S3 After the SC step S4 of coating the surface with solder and the roughening step S3 and SC step S4, the SR film 5 is formed in one opening of the VIA hole 2 to form the VIA hole 2 as shown in FIG. It comprises a closing step S5 of closing one opening and an inspection step S6 of performing an inspection such as an electrical inspection of the printed wiring board.

In the resist forming step S1, as shown in FIG. 1, a well-known liquid photoresist which is a photosensitive resin is used as an ink to perform screen printing on both front and back surfaces of the insulating base material 1 to form an SR layer. 4 is formed, and the SR layer 4 is photo-cured and developed by exposing the portion of the VIA hole 2 excluding the opening and the mounting portion of the electronic component on the wiring circuit. Therefore, on both the front and back surfaces of the insulating base material 1, the entire surface except the terminals (not shown) where electronic components of the wiring circuit are mounted and the opening of the VIA hole is S
The R layer 4 will be formed.

Then, in the CM printing step S2,
On the surface of the cured SR layer 4, characters, symbols, lines, etc. indicating the abbreviations and mounting positions of electronic components to be mounted on the printed board are screen-printed.

In the next roughening step S3, prior to the SC step S4, the surface of the portion of the wiring circuit exposed from the SR layer 4 is brought into contact with an etching solution to be soft-etched to form the wiring circuit. Cleans the surface of copper,
This is a step of roughening. That is, only the surface layer of copper is dissolved and removed for the purpose of easily soldering the solder.

Then, in the roughening step S3, the etching solution is washed after only the copper surface layer is dissolved and removed. At this time, the SR layer 4 is formed in the opening of the VIA hole 2.
1 is not formed, the VIA hole 2 penetrates and is opened as shown in FIG. That is,
The cleaning liquid can pass through the VIA hole 2. Therefore, the etching liquid that has entered the VIA hole 2 can be easily washed out with the cleaning liquid.

In the SC step S4 performed after the cleaning of the etching solution, the surface of the insulating base material 1 is brought into contact with molten solder to coat the copper surface exposed from the SR layer 4 with solder. Also, SC process S
In 4, the insulating base material 1 was immersed in molten solder,
After bringing the molten solder into contact with the surface of the insulating base material 1, hot air blowing leveling is performed.

Also in this SC step S4, the VIA hole 2 is in a state of being penetrated and opened, and the molten solder can flow in the VIA hole 2 and at the time of hot air blowing leveling. The hot air is in VIA hall 2
Since it can pass through the inside, the excess solder in the VIA hole 2 is blown off and the surface of the copper plating 3 on the inner wall of the VIA hole 2 is uniformly coated with the solder.

When one opening of the VIA hole 2 is blocked by the SR layer as in the conventional case, the flow of the molten solder in the VIA hole 2 is restricted. , VIA hole 2 may have a small amount of solder attached to it. Also, VI
The solder that adheres to the A hole 2 in the form of a small lump may come off when mounting electronic components on the completed printed wiring board. There is a possibility that they may reattach to the terminals of parts and cause a short circuit in the wiring circuit.

However, as described above, in the present embodiment, since the solder can flow in the VIA hole 2 and the hot air can pass through, there is no possibility that a lump of solder will be generated in the VIA hole 2 and the print can be performed. The short circuit of the wiring board can be prevented.

After the SC step S4, the insulating base material 1 is
In order to close the opening of the VIA hole 2 on one side,
In the opening of the VIA hole 2 of the insulating base material 1, the SC process S
Dot printing using well-known thermosetting SR ink is performed to a size approximately the same as the diameter of the VIA hole 2 after 4.
Then, as shown in FIG. 2, the SR film 5 is formed in one opening of the VIA hole. Then, after the dot printing, the SR film 5 that closes the opening of the VIA hole 2 is cured by baking.

After the SR process described above is performed, an inspection step S6 such as an electrical inspection of the printed wiring board is performed. In the electrical inspection, a test probe (not shown) is closely attached to many terminals of the wiring circuit on the surface of the printed wiring board, a constant voltage is applied between the terminals, and the continuity and insulation state of the wiring circuit are judged by the resistance value. , Inspect the wiring circuit for breaks and short circuits. At this time, the terminals of the wiring circuit are brought into close contact with the test probe by sucking the printed wiring board, but the VIA hole 2 is closed in the step S.
Since it is in the state of being blocked by the SR film 5 in 5, there is no problem in adhesion to the test probe by suction.

As described above, according to this embodiment, in the roughening step S3 after the SR step S1, the VIA hole 2 is in a penetrating and opening state. Therefore, when the etching solution is washed after etching, In addition, the etching solution in the VIA hole 2 can be easily washed, and the etching solution does not remain in the VIA hole 2. Therefore, VI
It is possible to prevent the copper plating 3 on the inner wall of the VIA hole 2 from being damaged by the etching solution remaining in the A hole and impairing the reliability of the printed wiring board.

Also in the SC step S4, since the VIA hole 2 is in a state of penetrating and opening, VI
The solder melted in the A hole 2 can freely flow, and hot air blows VIA at the time of hot air blowing leveling.
VIA Hall 2 as it can pass through the hall
There is no small lump of solder inside,
The surface of the copper plating 3 on the inner wall of the A hole 2 can be uniformly coated with solder. Therefore, when mounting the electronic component, it is possible to prevent the wiring circuit from being short-circuited due to a small lump of solder formed in the VIA hole 2.

The VIA hole 2 has a roughening step S.
3. After the SC step S4, tenting is performed by SR dot printing and the SR film 5 closes, so that when the electrical inspection is performed, the terminals of the printed circuit of the printed wiring board and the test probe are adhered by suction. It does not hinder the operation.

In the present embodiment, when forming the SR layer 4, a liquid photoresist is used as SR, and VI is used.
When the A hole 2 is tented by the SR film 5, S
Although a thermosetting type R is used as R, other well-known SR may be used for the SR layer 4 or the SR film 5. For example, a well-known ultraviolet curable resist may be used in the closing step S3.

[0034]

As described above in detail, according to the solder resist processing method in the production of the printed wiring board of the present invention, the through hole is not blocked when the SR layer is formed, and the resist forming step is performed. In the subsequent roughening step, the enching liquid can be easily washed,
The etching liquid does not remain in the through holes, and the reliability of the printed wiring board can be improved.

Further, since the through hole is closed in the closing step after the roughening step, it causes a problem when the printed wiring board is sucked and brought into close contact with the test probe during the electrical inspection. There is no.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a VIA hole portion of a printed wiring board for explaining a solder resist processing method in manufacturing the printed wiring board of the above embodiment.

FIG. 2 is a cross-sectional view of a VIA hole portion of the printed wiring board.

FIG. 3 is a flowchart for explaining a solder resist processing method in manufacturing the printed wiring board.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating substrate 2 VIA hole (through hole) 3 Copper plating (metal plating) on inner wall of VIA hole 4 Solder resist layer 5 Solder resist film

Claims (1)

[Claims] 1. A wiring circuit formed on at least both front and back surfaces of a plate-shaped insulating base material and metal plating formed on an inner wall so as to penetrate the insulating base material and connect the wiring circuits to each other. In a process for manufacturing a printed wiring board in which electronic components are mounted on the wiring circuit, a solder resist layer is formed on both front and back surfaces of the insulating substrate on which the wiring circuit and the through hole are formed. A method of processing a solder resist in the production of a printed wiring board for forming a solder resist layer on both front and back surfaces of an insulating substrate excluding an opening of the through hole and a mounting portion of an electronic component of the wiring circuit. A forming step, and then a roughening step of etching the mounting portion of the electronic component of the wiring circuit to roughen the surface; and a solder at the opening of the through hole after the roughening step. The solder resist processing method in the manufacture of printed wiring board, characterized by comprising; and a blocking step for blocking to form a resist film.