JP2000013004A - Manufacture of printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a stable square solder dam between part mounting pads with a narrow gap. SOLUTION: An insulating substrate 1 where a part mounting pad 2, is coated with at least two kinds of photosolder resists 3 and 4 of different development capacities which are set to touch for exposure and development. Two or more kinds of solder resists 3 and 4 of different development speeds are coated in the order starting with higher development speed, so the development is faster as lower layers, approach with its relative development time shorter than when only one kind of solder resist is used.

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 forming a rectangular solder dam between component mounting pads having a small interval.

[0002]

2. Description of the Related Art As a method of manufacturing a printed wiring board, there is a method of forming a rectangular solder dam between component mounting pads having a small space between each other.

A method of manufacturing a printed wiring board which suppresses undercut and forms a rectangular solder dam is disclosed in Japanese Patent Application Laid-Open No. 63-2.
No. 00594. JP-A-63-20
The production method disclosed in Japanese Patent No. 0594 is a method using two layers of photocurable solder resists having different internal curability, and the production process is shown in FIG.

According to the manufacturing method disclosed in Japanese Patent Application Laid-Open No. 63-200574, a circuit pattern 7 is first formed on an insulating substrate 1 as shown in FIG.
As shown in the figure, the internal photocurable solder resist 8
Is applied to the entire surface of the substrate by screen printing to a thickness of 15 to 25 μm, and drying is performed at 70 to 90 ° C. for 5 to 10 minutes.

Next, as shown in FIG. 2C, a surface light-curable solder resist 9 is formed on the internal light-curable solder resist 8 by screen printing to a thickness of 15 to 25 μm.
And dried at 70 to 90 ° C. for 15 to 30 minutes.

[0006] Next, as shown in FIG. 2 (d), 200-500 mJ / cm ² ultraviolet light exposure is applied through the mask film 5 to obtain 1.1.1.1. Development is performed with a solvent such as trichloroethane, and a desired solder resist pattern 6 is obtained (FIG. 2E).

The solder resist pattern 6 shown in FIG. 2 (e) has a surface photo-curing property in the upper layer and an internal photo-curing property in the lower layer. Can be suppressed.

[0008]

By the way, it is necessary to form a solder resist in the gap between the component mounting pads of the printed wiring board in order to prevent the adhesion of solder bridges and solder balls during soldering. As electronic devices become smaller and have higher performance, pad gaps are becoming smaller year by year.

However, it is extremely difficult to form a fine wiring pattern 7 and a fine solder resist pattern 6 in the manufacturing method using solder resists having different curability as shown in FIG.

An object of the present invention is to provide a method for manufacturing a printed wiring board for forming a rectangular solder resist having stable and excellent adhesion between pads having a small gap.

[0011]

In order to achieve the above object, a method of manufacturing a printed wiring board according to the present invention is directed to a method of manufacturing a printed wiring board in which a solder resist is patterned and formed in a narrow space on a substrate. Then, two or more solder resists having different development speeds are applied to the entire surface of the substrate, and the solder resist is dried by touching, exposed and developed, and then patterned in a narrow space on the substrate. It is formed.

The two or more solder resists having different developing speeds are set so that the developing speed of the lower layer is higher than that of the upper layer.

Two or more solder resists having different developing speeds have different developing speeds with respect to an alkaline developing solution due to a difference in acid value.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.

Referring to FIG. 1, the method for manufacturing a printed wiring board according to the present invention is a method for manufacturing a printed wiring board by patterning a solder resist in a narrow space on a substrate. Are applied to the entire surface of the substrate 1, and the solder resists 3 and 4 are dried by touching. After exposure and development processes, the solder resist 6 is placed in a narrow space on the substrate 1. Is formed by patterning.

The two or more solder resists 3 and 4 having different developing speeds are set so that the lower layer has a higher developing speed than the upper layer. The two or more solder resists 3 and 4 having different developing speeds have different acid values. The developing speed for an alkaline developing solution is made different.

Next, a specific example of the method for manufacturing a printed wiring board according to the present invention will be described in detail as an embodiment.

FIG. 1 is a sectional view showing a method of manufacturing a printed wiring board according to an embodiment of the present invention in the order of steps.

As shown in FIG. 1A, a component mounting pad 2 is formed on an insulating substrate 1 made of an organic insulating material made of glass epoxy or glass polyimide.

Next, as shown in FIG. 1B, a first photo solder resist 3 is applied to the entire surface of the insulating substrate 1 for 10 to 2 hours.
The entire surface is applied to a film thickness of 0 μm by screen printing or curtain coating.

The first photo solder resist 3 shown in FIG. 1 (b) is prepared by adding 5.6 mol of acrylic acid to a dipentaerythritol derivative and then adding 0.4 mol of Of phthalic anhydride or maleic anhydride, the acid value of which is 60
A photo solder resist containing an acrylate resin adjusted to １００100 (mg · KOH / g) is used.

Next, the first photo solder resist 3 applied on the entire surface of the insulating substrate 1 is heated at 70 to 90 ° C. for 15 minutes.
Dry to touch for ~ 30 minutes.

Subsequently, as shown in FIG. 1C, a second photo solder resist 4 is screen-printed or curtain-coated on the first photo solder resist 3 having a thickness of 10 to 20 μm on the touch-dried first photo solder resist 3. It is applied by a coating method or the like.

The second photo solder resist 4 has a first
5.6 mol of methacrylic acid is added to the dipentaerythritol derivative and then reacted with 0.4 mol of phthalic anhydride or maleic anhydride in order to increase the development speed more than that of Photo Solder Resist 3 A photo solder resist containing an acrylate resin whose acid value is adjusted to 30 to 50 (mg · KOH / g) is used.

Next, the second photo solder resist 4 applied on the first photo solder resist 3
Dry to the touch at 0-90 ° C for 15-30 minutes.

Through the above two steps, two layers of photo solder resists 3 and 4 having different developing speeds are formed between the component mounting pads 2 and 2 of the insulating substrate 1.

Of the two layers of the photo solder resists 3 and 4, the lower layer of the solder resist 4 has a higher developing speed than the upper layer of the solder resist 3, and the lower layer has a higher developing speed than the upper layer.

Here, the developability of the first photo solder resist 3 can be improved to about 1.5 to 2 times that of the second photo solder resist 4 due to the difference in acid value.

Next, as shown in FIG. 1D, the integrated exposure amount is 50 to 200 (mJ / c) through the mylar film 5.
m ² ) UV light 4 is applied to the photo solder resists 3 and 4.

Next, as shown in FIG. 1E, a 1% aqueous solution of sodium carbonate was used at a liquid temperature of 30 ° C. and a spray pressure of 2-3.
(Kg / cm ² ), and development is performed for a processing time of 30 seconds to 90 seconds.

A solder resist pattern 6 having a rectangular shape and excellent adhesion without causing halation or back exposure.
Is formed between adjacent component mounting pads 2.

[0032]

As described above, according to the present invention, a solder dam with good adhesion can be stably formed in the gap between the component mounting pads having a small pad gap.

The reason is that, since two or more types of solder resists having different developing speeds are applied in the order of higher developing speed, the developing speed becomes higher as going to the lower layer, and the relative developing time becomes longer. It can be shorter than when only one type is used. That is, development proceeds in the lower layer direction without undercutting the upper layer solder resist, so that a rectangular solder dam having excellent adhesion can be formed.

[Brief description of the drawings]

FIG. 1 is a sectional view illustrating a method for manufacturing a printed wiring board according to an embodiment of the present invention in the order of manufacturing steps.

FIG. 2 is a cross-sectional view showing a method of manufacturing a printed wiring board according to a conventional example in the order of manufacturing steps.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating board 2 Component mounting pad 3 First solder resist 4 Second solder resist 5 Mylar film 6 Solder resist pattern

Claims (3)

[Claims] 1. A method of manufacturing a printed wiring board, comprising forming a solder resist in a narrow space on a substrate by patterning the solder resist, wherein two or more solder resists having different developing speeds are applied to the entire surface of the substrate. A method for manufacturing a printed wiring board, comprising: performing touch drying on a substrate; and performing exposure and development steps to pattern a solder resist in a narrow space on the substrate. 2. The method for manufacturing a printed wiring board according to claim 1, wherein the two or more solder resists having different developing speeds are set to have a higher developing speed for a lower layer than for an upper layer. 3. The method for manufacturing a printed wiring board according to claim 2, wherein the two or more solder resists having different developing speeds have different developing speeds with respect to an alkaline developer depending on a difference in acid value.