JPH08153950A - Manufacture of printed wiring board - Google Patents

Abstract

PURPOSE: To provide a printed wiring board manufacturing method by which width fluctuation in the circuit pattern of a printed wiring board can be suppressed and high-density wiring and a micro-circuit can be easily formed, and then, the contaminant in an electroless plating bath with a plating resist can be prevented. CONSTITUTION: After a first copper film 3 is formed on a copper-plated substrate 1 and the film 3 is coated with a plating resist 3, the resist 5 is removed from the area of a circuit pattern forming part. Then a second copper film 6 is formed in the area from which the resist 5 is removed and a circuit pattern is formed. After forming the circuit pattern, the remaining plating resist is removed and the entire surface of the substrate 1 is coated with a solder film 7. Thereafter, a circuit pattern covered with a solder film 8 is formed by fusing the solder film 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a printed wiring board, and more particularly to a method for manufacturing a printed wiring board on which surface-mounted components can be mounted at a high density.

[0002]

2. Description of the Related Art Among conventional subtractive methods for manufacturing printed wiring boards, a panel plating method and a pattern plating method are known as typical examples.

FIGS. 4 (a) to 4 (f) are cross-sectional views showing an example of a panel plating method in a conventional method of manufacturing a printed wiring board in the order of steps. In the conventional panel plating method, first, as shown in FIG.
Is formed. Next, as shown in FIG. 4B, a hole is formed in the copper-clad substrate 1 to form a through hole 4a, and then, as shown in FIG. A copper coating 3a of 35 μm is formed. Next, as shown in FIG. 4D, a photosensitive film of about 50 μm or an adhesion resist of about 20 μm was formed on the copper coating 3a, and an active ray was irradiated to expose the area of the copper wiring pattern forming portion. After that, the photosensitive film or the adhesive resist other than the area of the wiring pattern forming portion is peeled off by development to form a pattern of the positive type etching resist 13. Next, as shown in FIG. 4E, the copper coating 3a including the copper foil 2 in the region not coated with the etching resist 13 is etched with a cupric chloride etching solution or a ferric chloride etching solution. Finally, as shown in FIG. 4F, the etching resist 1 remaining on the copper coating 3a is formed.
3 is peeled off to form a copper circuit pattern 9.

FIGS. 5 (a) to 5 (g) are cross-sectional views sequentially showing steps of an example of a pattern plating method in a conventional method of manufacturing a printed wiring board. The conventional pattern plating method is
As shown in FIG. 5A, a copper-clad substrate 1 having a copper foil 2 having a thickness of 5 to 9 μm is formed. Next, as shown in FIG. 5B, a hole is formed in the copper-clad substrate 1, and then a first copper coating 3 of 2 to 5 μm is formed by electroless copper plating. Next, as shown in FIG. 5C, a plating resist 5 is formed in a region other than the region of the wiring pattern forming portion on the first copper film 3, and then, as shown in FIG. Second
Is formed. Next, as shown in FIG. 5E, after forming a solder film 7 on the second copper film 6, the plating resist 5 is peeled off as shown in FIG. 5F.
Finally, as shown in FIG. 5 (g), unnecessary portions of the first copper coating 3 including the copper foil 2 are removed by etching, and the shape of the solder coating 7 is improved by fusing to form a copper circuit pattern. obtain.

[0005]

In the panel plating method, which is a conventional method for manufacturing a printed wiring board, a circuit is formed by etching. Therefore, delicate conditions of etching, for example, etching at front and back surfaces of a substrate and at positions in the same plane. The difference in the amount reduces the precision of the width of the circuit pattern. Further, since the accuracy of the plating thickness also affects the width accuracy of the circuit pattern, there is a problem that it is difficult to form a high-density wiring or a minute circuit pattern.

On the other hand, in the pattern plating method, the etching amount is small, and the variation in the width of the circuit pattern can be suppressed. However, since the solder film is formed while the plating resist is formed, there is a problem that the solder bath is contaminated by the plating resist.

An object of the present invention is to provide a method for manufacturing a printed wiring board in which high-density wiring and microcircuits can be easily formed and there is no contamination of a solder bath.

[0008]

According to a first aspect of the present invention, there is provided a method of manufacturing a printed wiring board, comprising the steps of: forming a first copper film by performing electroless copper plating on a surface of a copper-clad substrate; A step of coating the resist on the film and stripping the resist in the area of the circuit pattern forming portion, a step of forming a second copper film in the area where the resist has been stripped, and the step of remaining on the copper-clad substrate The method includes a step of removing a resist, a step of forming a solder coating on the exposed first copper coating and the second copper coating by electroless solder plating, and a step of fusing the solder coating.

According to a second aspect of the present invention, there is provided a method of manufacturing a printed wiring board, comprising: a step of forming a first copper film by electroless copper plating on a surface of an insulating substrate; and a step of coating a resist on the first copper film. Removing the resist in the region of the circuit pattern forming portion, forming a second copper film in the region where the resist has been removed, removing the resist remaining on the insulating substrate, exposing Forming a solder coating on the first copper coating and the second copper coating by electroless solder plating; and covering a mounting portion including a pad with a solder etching resist and coating with the solder etching resist. And removing the solder etching resist and fusing the solder coating.

[0010]

Embodiments of the present invention will now be described with reference to the drawings.

FIGS. 1A to 1G are sectional views showing the first embodiment of the present invention in the order of steps, FIGS.
(B) is a top view of the circuit pattern in the manufacturing process of 1st Example, respectively. The first embodiment of the present invention is as follows.
As shown in FIG. 1A, a copper-clad substrate 1 is formed by molding an insulating substrate 11 on which a copper foil 2 having a thickness of 5 to 9 μm is adhered into a predetermined shape. Next, as shown in FIG. 1 (b), a predetermined diameter of the copper-clad substrate 1 is
After piercing a through hole, degreasing, soft etching,
Pre-treatment of pre-dip, catalyst, accelerator, and electroless copper plating using copper sulfate, formaldehyde, EDTA, sodium hydroxide at a temperature of 70 ° C and copper foil 2 and through hole wall surface. 2 to 5 μm
The first copper coating 3 having a thickness of 1 is deposited to form the through hole 4. At this time, the first copper coating 3 including the copper foil 2 on the insulating substrate 11 after the formation of the first copper coating 3 is set not to exceed 15 μm. This is because if the copper film on the insulating substrate 11 exceeds 15 μm, a copper residue is generated when the copper film is replaced with a solder film in a later step.

Next, as shown in FIG. 1C, the photosensitive layer on the first copper film 3 has a thickness of 30 to 30 having plating solution resistance.
A 50 μm dry film is laminated, and a region other than the circuit pattern forming part is exposed by a super high pressure mercury lamp with a positive pattern film and developed with a sodium carbonate developer to form a plating resist 5 in the region other than the circuit pattern forming part. To do. At this time, the circuit interval of the circuit pattern is 1 mm.
If the opening is open, the solder on the insulating substrate 11 may not remain on the copper circuit pattern portion and remain as a solder ball due to the fusing in a later process. As shown in FIGS. 2 (a) and 2 (b), it is preferable to provide a solder focusing pattern 10 for focusing the solder.

Next, as shown in FIG.
Immerse in an electroplating solution of sulfuric acid and brightener at room temperature for 60 to 90 minutes, or use copper sulfate, formaldehyde, EDT
A, 70 ℃ in electroless copper plating solution of sodium hydroxide
After the second copper film 6 is formed on the portion of the first copper film 3 that is not coated with the plating resist 5 by 20 to 30 μm by immersion for 10 to 15 hours, as shown in FIG. Next, the plating resist 5 is peeled off with a stripping solution of caustic soda. Next, as shown in FIG. 1 (f), all of the exposed first copper coating 3 and copper foil 2 and the second copper are immersed in an organic acid-based electroless solder plating solution at a temperature of 70 ° C. Film 6
The thickness of the surface layer of 7 to 15 μm is
To form. Finally, as shown in FIG.
℃ or more, peak temperature 220 ~ 240 ℃ 30 ~
By performing fusing for 60 seconds, the replaced solder film 7 on the insulating substrate 11 gathers in the copper circuit pattern portion, and a copper circuit pattern 9 covered with the solder film 8 after fusing is obtained.

3 (a) to 3 (i) are sectional views showing a second embodiment of the present invention in the order of steps. In the second embodiment of the present invention, first, as shown in FIG. 2A, a through hole having a diameter of 0.4 mm is drilled at a predetermined position of an insulating substrate 11 having no copper film using a drill. Pre-treatment of degreasing, pre-dip, catalyst, accelerator, electroless copper plating at 70 ° C using copper sulfate, formaldehyde, EDTA, sodium hydroxide electroless copper plating solution, including through hole wall The first copper film 3 and the through hole 4 are formed on the surface of the insulating substrate 11. Next, FIG. 3 (b)
As shown in (1), a 30-50 μm-thick dry film having plating solution resistance is lined as a photosensitive layer on the first copper film 3, and a plating resist 5 is applied to a region other than a circuit pattern forming portion by a positive pattern film. Exposure is performed with an ultrahigh pressure mercury lamp, and the phenomenon occurs with a developing solution of sodium carbonate to form a plating resist 5 in a region other than the circuit pattern forming portion.
Next, as shown in FIG. 3 (c), it is immersed in an electroplating solution of copper sulfate, sulfuric acid, and a brightener at room temperature for 60 to 90 minutes,
Alternatively, it is applied to an electroless copper plating solution of copper sulfate, formaldehyde, EDTA, sodium hydroxide at a temperature of 70 ° C. for 10 to 15
By immersing for 2 hours, the second copper coating 6 is formed on the first copper coating 3 not covered by the plating resist 5.
After the formation of 0 to 30 μm, as shown in FIG. 3D, the plating resist 5 is stripped with a stripping solution of caustic soda.

Next, as shown in FIG. 3 (e), all of the exposed first copper coating 3 is immersed in an organic acid-based electroless solder plating solution at a temperature of 70.degree. The thickness of the surface layer 7 to 15 μm of the coating 6 is replaced to form the solder coating 7. Next, as shown in FIG. 3F, after mounting parts such as pads are covered with a solder etching resist 12,
As shown in FIG. 3 (g), the solder coating 7 in the uncoated area is peeled off. Thereby, it is possible to prevent a phenomenon that a solder ball is generated on the insulating substrate 11 at a location where the circuit interval of the copper circuit pattern is too large to be 1 mm or more when performing the fusing. Next, after the solder etching resist 12 is peeled off as shown in FIG.
As shown in (i), a copper circuit in which a mounting portion such as a pad is covered with the solder coating 8 after fusing by performing fusing at a temperature of 200 ° C. or higher and a peak temperature of 220 to 240 ° C. for 30 to 60 seconds. A pattern 9 is obtained.

[0016]

As described above, according to the present invention, the plating resist is coated, the plating resist in the area of the circuit pattern forming portion is peeled off, and then a circuit pattern is formed in the peeled area. Since the solder film is formed and the solder film is fused, variations in the width of the circuit pattern on both the front and back surfaces and in the same surface due to etching are suppressed, and there is an effect that high-density wiring and minute circuits can be easily formed.

Further, there is an effect that the electroless plating bath can be prevented from being contaminated by the plating resist.

[0018]

[Brief description of drawings]

FIGS. 1A to 1G are cross-sectional views shown in the order of steps for explaining a first embodiment of the present invention.

2A and 2B are plan views of a copper circuit pattern during the manufacturing process of the first embodiment, respectively.

3 (a) to 3 (i) are cross-sectional views shown in the order of steps for explaining a second embodiment of the present invention.

FIGS. 4A to 4F are cross-sectional views sequentially illustrating steps of an example of a panel plating method in a conventional method of manufacturing a printed wiring board.

5A to 5G are cross-sectional views showing the order of steps for explaining an example of a pattern plating method of a conventional method for manufacturing a printed wiring board.

[Explanation of symbols]

 1 Copper-clad substrate 2 Copper foil 3 First copper film 3a Copper film 4 Through hole 4a Through hole 5 Plating resist 6 Second copper film 7 Solder film 8 Solder film after fusing 9 Copper circuit pattern 10 Solder focusing pattern 11 Insulation substrate

Claims (2)

[Claims] 1. A step of forming a first copper film by performing electroless copper plating on a surface of a copper-clad substrate, and coating a resist on the first copper film and removing the resist in a region of a circuit pattern forming portion. Stripping, forming a second copper film in a region where the resist has been stripped, stripping the resist remaining on the copper-clad substrate, and exposing the exposed first copper film. A method for manufacturing a printed wiring board, comprising: a step of forming a solder film on the second copper film by electroless solder plating; and a step of fusing the solder film. 2. A step of forming a first copper film by performing electroless copper plating on a surface of an insulating substrate, and coating a resist on the first copper film and peeling the resist in a region of a circuit pattern forming portion. Performing a step of forming a second copper film in a region where the resist has been removed, removing the resist remaining on the insulating substrate, and removing the second copper film on the exposed first copper film. Forming a solder film on the copper film by electroless solder plating, and covering the mounting portion including the pad with a solder etching resist, and removing the solder film in a region not covered with the solder etching resist. Stripping the solder etching resist and fusing the solder coating.