JP2713037B2 - Printed wiring board and manufacturing method thereof - Google Patents

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 pads for surface mounting electronic components and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, when mounting an electronic component on a printed wiring board, soldering is performed on pads for mounting the electronic component on the printed wiring board so that the electronic component can be easily mounted. In some cases, instead of applying solder to the surface pad for this purpose, the exposed copper surface is coated with a pre-flux. When solder is applied to a pad for mounting electronic components, it is manufactured through the following steps, for example. A description will be given taking a single-sided printed wiring board as an example.

[0003] A prepreg (a glass nonwoven fabric impregnated with an epoxy resin and semi-cured) and a copper foil are laminated on a substrate and subjected to electroless plating and electrolytic plating to form an outermost copper layer. Perform copper plating on the foil surface. Next, a dry film is laminated to form a conductor pattern, a positive film of a desired conductor pattern is adhered to the dry film, exposed and developed, a resist is formed, and a wiring pattern of an outer layer circuit is formed. Then, copper is applied to the wiring pattern of the outer layer circuit having no resist by copper sulfate plating, and solder is applied to the copper surface of the outer layer circuit wiring pattern by electrolytic plating to form a solder layer.

Then, the dry film is removed,
Etching is performed using the solder layer as a resist to provide a desired conductor pattern. After that, as an etching resist, the used solder layer is dissolved and removed, and a solder resist is applied to pads other than pads for mounting electronic components. (The manufacturing process up to this point is the same as the manufacturing process of a multilayer printed wiring board to which a pre-flux is applied as described below.)

[0005] In order to improve the wettability of the solder when mounting electronic components, it is necessary to apply solder to the wiring board in advance on the multilayer printed wiring board on which the solder resist has been applied. Printed wiring in which a wiring board is immersed in a molten solder bath at a temperature of ℃ to 240 ° C for 3 to 5 seconds, the wiring board is pulled up in a vertical direction, and excess solder is blown off with hot air to form a solder layer on pads for mounting electronic components. There is a manufacturing method for obtaining a board.

On the other hand, the method of manufacturing a printed wiring board to which a pre-flux is applied is the same as the above-described method of manufacturing a multilayer printed wiring board up to the step of applying a solder resist. On the printed wiring board after the solder resist is applied, a surface treatment is performed by soft etching on a portion where copper is exposed, such as a pad for mounting an electronic component, and a pre-flux is applied to obtain a printed wiring board.

[0007]

However, in recent years, the width of the leads of electronic mounted components has been reduced due to the high integration and miniaturization of electronic mounted components, and the width between the leads has also been reduced. For example, cream solder is used when mounting electronic components on high-density pads such as pads with a width of 0.20 mm or less for mounting electronic components and widths of 0.10 mm or less for pads. It is required to thicken the solder instead of using it.For sparse pads, a printed wiring board coated with pre-flux that is easy to mount, that is, a pad layer contains a solder layer and a pre-flux depending on the pad density There is a need for printed wiring boards.

In order to obtain a printed wiring board having a pad in which a solder layer is provided on a pad for mounting an electronic component and a pad on which a pre-flux is applied as described above, first, It is sufficient to form a solder layer and then apply a pre-flux, but there are the following problems. For one, in order to apply a pre-flux, the copper surface must be cleaned, etched and surface-treated, so that the solder layers (4) and (4a) are exposed as shown in FIG. When such a surface treatment is performed, there is a problem that the solder layer is eroded. The above problem is that a protective mask may be formed on the solder part in order to protect it from etching erosion.However, when a dry film is used as the protective mask, the solder and pre-flux are eroded by the peeling liquid when peeling. There is a problem that is.

[0009]

That is, according to the first aspect of the present invention, in a pad on the same surface of a printed wiring board having pads for mounting electronic components on a surface, the pads have a high density. The printed wiring board according to claim 2, wherein a solder layer is provided on the provided pad, and a pre-flux is applied to the sparsely provided pad.
The invention described in (1) is a printed wiring board having pads for surface mounting electronic components, a solder layer is provided on some of the pads, a peelable protective mask is laminated on the solder layer, and the like. 4. A method for manufacturing a printed wiring board, comprising applying a pre-flux to cover a pad, and then peeling off the protective mask. The invention according to claim 3, wherein the protective mask is a peel coat ink. Alternatively, the method is a method for manufacturing a printed wiring board according to claim 2, wherein the printed wiring board is formed by a tape.

[0010]

According to such technical means, even if a solder layer is formed first, a protective mask is applied to the solder, so that even if a surface treatment by etching for applying a pre-flux is performed, the solder is eroded. It will not be done. Furthermore, if the protective mask is provided with a peel coat ink or a tape, when the protective mask is peeled off, the solder and pre-flux applied portions are not eroded, so that the solder layer and the solder layer are applied to the pads for mounting electronic components. A printed wiring board in which flux is mixed can be obtained.

[0011]

1 to 4 are cross-sectional views of a main part showing a manufacturing process of a printed wiring board according to first and second embodiments of the present invention. A prepreg (insulating glass non-woven fabric impregnated with an epoxy resin and semi-cured) and a copper foil are laminated on the base material (1), and electroless plating and electrolytic plating are performed. Copper plating is performed on the foil surface. Next, a dry film is laminated to form a conductor pattern, a positive film of a desired conductor pattern is adhered to the dry film, exposed and developed to form a resist, and a wiring pattern of an outer layer circuit is formed. Copper is applied to the wiring pattern of the outer layer circuit having no resist by copper plating, and solder is applied to the copper surface of the outer layer circuit wiring pattern by electrolytic plating to form a solder layer.

Then, the dry film is removed,
Etching is performed using the solder layer as a resist to provide a desired conductor pattern. Thereafter, the pad (2) has a high-density pad having a width of 0.15 mm and a width of 0.10 mm between the pads for mounting electronic components in the conductor pattern.
In order to form a resist on a portion where the solder layer (4) provided with is left, a dry film is laminated, a negative film is placed thereon, and exposure and development are performed to form a resist. Then, the solder of the portion where the solder layer on which the resist is formed, that is, the sparsely provided pad (3) and the wiring pattern portion other than the pad portion provided at a high density is melted and removed, and the solder is separated.

Thereafter, the dry film is peeled off, and the remaining solder layer is heated to melt the solder to form a homogeneous alloy. Then, a solder resist (5) is applied. Therefore, in the above embodiment, as shown in FIG. 1, the solder (4) remains in the portion (2) where the pads for mounting electronic components are dense, and the solder is peeled in the sparse portion (3), and the copper is removed. Is exposed.

The printed wiring board formed as described above has its surface washed to leave the solder of the solder layer (4) as it is and to apply a pre-flux to the conductor pattern without solder. In the manufacturing process, the surface of the conductor pattern is oxidized, so the oxide film is removed,
In addition, etching is performed to roughen the surface and surface treatment is performed so that the solder can be put in a good state at the time of mounting electronic components and mounting can be performed reliably. At this time, as shown in FIG. 2, a peel coat ink (product name: 448) is applied to the solder (4) so that the solder (4) is not eroded by etching.
D, Manufacture: Asahi) is printed by screen printing so as to be 0.05 mm wider than the conductor pattern on which the solder is applied, to form a protective mask (6). After forming the protection mask (6),
Wash with water and perform surface treatment by etching. Next, FIG.
Preflux (7) (manufactured by MEC, R-40
00) is applied to the entire surface of the printed wiring board with a thickness of 1.0 to 2.0 μm by a roll coater. Here, since the pre-flux (7) is applied to the entire surface of the printed wiring board, the pre-flux (7) is applied to the conductor pattern without solder.
Is applied.

Next, the protective mask (6) is peeled off and peeled off. Then, the solder and the pre-flux can be peeled off without erosion, and the solder remains on the high-density pad (2) for mounting the electronic component, and the pre-flux (7) on the sparse pad (3). Can be obtained as shown in FIG.

In the second embodiment, a base material (1a) is laminated with a prepreg (a glass nonwoven fabric impregnated with an epoxy resin and semi-cured) as an insulating adhesive and a copper foil, and electroless plating is performed. Then, electrolytic plating is performed, and copper plating of the outermost copper foil surface is performed. Next, a dry film is laminated to form a conductor pattern, a positive film of a desired conductor pattern is brought into close contact with the dry film, exposed and developed to form a resist, and a wiring pattern of an outer layer circuit is formed.
Copper is thickened on the wiring pattern of the outer layer circuit having no resist by copper sulfate plating, and solder is electrolytically plated on the copper surface of the outer layer circuit wiring pattern to form a solder layer.

Then, the dry film is removed,
Etching is performed using the solder layer as a resist to provide a desired conductor pattern. Thereafter, the solder layer used as the resist is melted and removed.

Next, pads (2a) having a high density of 0.10 mm and 0.10 mm between the pads for mounting electronic components in the conductor pattern.
In order to form a solder layer only on the surface, a portion to be formed is cleaned to form a solder layer (4a).

Therefore, a solder layer (4a) is formed on the pad (2a) on which pads for mounting electronic components are provided at a high density, and copper (3a) and the wiring pattern provided on the pad (2a) are provided sparsely. Is exposed.

Then, a solder resist (5a) is applied to pads other than pads for mounting electronic components, and the printed wiring board on which the solder resist (5a) has been applied as shown in FIG. 1 has no solder. In order to apply the pre-flux to the sparse pad (3a), the applied surface is cleaned and the oxide film is removed because the pattern surface is oxidized in the above manufacturing process, and the solder is in good condition when mounting electronic components. In order to assure the mounting, the surface is roughened by etching for the purpose of roughening the surface. Therefore, in order to prevent the solder from being eroded by etching, for example, a tape (manufactured by Sumitomo 3M, # 851) is attached to the solder portion by a crimping method so as to be 0.05 mm wider than the conductor pattern on which the solder is applied, as shown in FIG. A protection mask (6a) is formed.
The type of tape is # 331T made by Sumitomo 3M in addition to the above.
And material type 9190, NITTO SPV2
31 or the like can be used. After the protection mask (6a) is formed, it is washed with water, surface-treated by soft etching, and a preflux (7a) is applied to the entire surface of the printed wiring board by a roll coater at a film pressure of 1 to 2 μm as shown in FIG. Here, since the preflex (7a) is applied to the entire surface of the printed wiring board, the preflex is applied to the sparse pads (3a) on which no solder is applied.

Next, the protection mask (6a) is manually peeled off. In this case, it is not peeled off by chemicals, so it can be peeled off without eroding the solder and preflex, the part where the surface pad for mounting the electronic mounting parts has the solder on it, and the preflex on it Figure 4 where parts are mixed
Can be obtained.

[0022]

As described above, according to the present invention, there is provided a printed wiring board in which a pad for providing a solder layer on a pad for mounting an electronic component and a pad for applying a preflux instead of the solder layer are mixed. Can be obtained, and in the manufacturing method, first, a solder layer is provided, and then, when a pre-flux is applied, a pre-flux is applied after providing a protective mask on the solder layer. Does not erode the solder layer when performing a surface treatment to apply the solder.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part of a printed wiring board in a manufacturing process according to first and second embodiments of the present invention.

FIG. 2 is a cross-sectional view of a main part of the printed wiring board in a manufacturing process according to the first and second embodiments of the present invention.

FIG. 3 is a cross-sectional view of a main part of a printed wiring board in a manufacturing process according to the first and second embodiments of the present invention.

FIG. 4 is a cross-sectional view of a main part of a printed wiring board in a manufacturing process according to the first and second embodiments of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate 1a ... Substrate 2 ... High density pad 2a ... High density pad 3 ... Sparse pad 3a ... Sparse pad 4 ... Solder layer 4a
... Solder layer 5 ... Solder resist 5a ... Solder resist 6 ... Protective mask 6a ... Protective mask 7 ... Pre-flux 7a ... Pre-flux

Claims (3)

(57) [Claims] A pad provided on a same surface of a printed wiring board having pads for mounting electronic components on a same surface, a pad provided with a high density of pads, a solder layer provided, and a pad provided sparsely provided. A pre-flux is applied to the printed wiring board. 2. A printed wiring board having pads for surface-mounting electronic components, a solder layer is provided on some of the pads, and a peelable protective mask is laminated on the solder layer. A method for manufacturing a printed wiring board, comprising applying a pre-flux so as to cover a pad, and then removing the protective mask. 3. The protection mask according to claim 2, wherein the protection mask is formed of a peel coat ink or a tape.
3. The method for producing a printed wiring board according to claim 1.