JPH02260490A - Manufacture of ultraviolet ray shielding circuit board - Google Patents

Abstract

PURPOSE:To prevent transmission of an ultraviolet ray while maintaining performance and an external appearance by previously coating a glass fiber base material with ultraviolet ray absorber and/or fluorescent dye, and further using prepreg in which varnish containing ultraviolet ray absorber and fluorescent dye mixed in thermosetting resin is immersed with glass fiber base material and dried. CONSTITUTION:A glass fiber base material such as glass woven fabric, glass nonwoven fabric base material, etc. is previously coated with ultraviolet ray absorber for absorbing ultraviolet and visible lights and/or fluorescent dye, and prepreg in which varnish containing ultraviolet ray absorber and fluorescent dye mixed in thermosetting resin is immersed with glass fiber base material and dried is used. Thus, performance and external appearance as a laminated board can be maintained, and ultraviolet transmission preventing effect can be improved.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention has an extremely excellent effect in preventing ultraviolet transmission,
The present invention relates to a laminate for printed circuits which has no difference in hue from laminates produced by conventional methods and which enables simultaneous exposure of both sides of a photo-developable solder resist.

(Prior Art) A solder resist is usually formed on the outermost conductive pattern layer of a printed wiring board in order to prevent solder pre-fridges between conductors during soldering or to permanently protect the conductive pattern.

Screen stamping is used to form solder resist! There are two methods for printing photographs using photosensitive resin.

Traditionally, screen printing was the most commonly used method, but as electronic components become smaller and more chip-based, the mounting density on printed wiring boards has become higher, so screen printing has become less precise and easier to work with. It is becoming less practical. Therefore, instead of the screen printing method, photo printing using a negative or positive mask using a photosensitive resin (photoresist) has come to be performed by a method.

However, according to the photo printing method, when both sides of a photoresist are simultaneously exposed on a circuit printed on both sides of a laminate, the light that has passed through the photoresist during exposure is further transmitted through the laminate.
It has become known that photoresists on opposite sides of each other are also exposed, resulting in insufficient accuracy of the solder resist, which is the original purpose. Especially when the thickness of the laminate is 1.
It is known that the light transmittance is large when the thickness is 6- or less, so the thickness of the photoresist is increased (50 to 80 μm).
), or a laminate using a polyimide-modified resin as the outermost surface of the laminate, as disclosed in Japanese Patent Publication No. 54-34140.

However, when the thickness of the photoresist is increased, extra curing time is required after exposure and development in order to fully develop its performance as a solder resist. On the other hand, the use of polyimide-modified resin for a part of the laminate increases the cost and has the disadvantage that the prevention of light transmission is still insufficient. In order to eliminate these drawbacks, a method has been proposed in which a light-shielding substance is contained in the laminate to prevent light transmission (Japanese Patent Laid-Open No. 54-32769).

As a result of examining various light-shielding substances, the present inventors found that among organic ultraviolet absorbers, those with a specific ultraviolet wavelength absorption region are effective in preventing light transmission. When the content is increased, there are disadvantages such as a decrease in performance as a printed circuit board, such as discoloration due to heating, decrease in solvent resistance, and thermal deterioration of various performances.

Furthermore, when the content is reduced, the effect of preventing light transmission is small, especially in a laminate having a thickness of 1.2 mm or less. Furthermore, in inorganic ultraviolet screening agents,
It has been found that oxides are particularly effective, but when mixing resin with an amount that can prevent light transmission and coating and impregnating it, it is necessary to
Due to the difference in the specific gravity of the oxides, it is difficult to impregnate the oxides uniformly, resulting in variations in the light transmittance of the produced laminate.

In addition, with improvements in the accuracy of photo solder resists in recent years, a MAN plate that blocks light in a longer wavelength range (nearly 420 ns) than the conventional ultraviolet range is desired, and conventional UV absorbers are formulated alone. However, it is becoming difficult to satisfy (1) prevention of exposure to light. As a solution to this problem, a method has been adopted in which dyes or pigments are added during the production of the laminate, but either method has the disadvantage that the appearance of the laminate differs greatly from the conventional color tone.

Furthermore, recently there has been an increase in the trend towards thinner 47N111 laminates, and a new problem has arisen in which simply adding ultraviolet absorbers or fluorescent dyes to conventional thermosetting resins causes back exposure in areas where glass fibers overlap. However, the prevention of light transmission of thin plate laminates is still insufficient.

(Problem to be Solved by the Invention) It is an object of the present invention to provide a laminate that maintains the performance and appearance of a laminate for printed circuits and has an excellent effect in preventing UV transmission. It is in.

(Means for Solving the Problems) The present invention provides a glass woven fabric or a glass nonwoven fabric base material (hereinafter referred to as a glass fiber base material) impregnated with a thermosetting resin and dried.
In the manufacturing method of a laminate board, in which a glass fiber base material is coated in advance with an ultraviolet absorber and/or a fluorescent dye that absorbs light in the ultraviolet and visible regions (wavelengths 300 to 450 nii), and then thermally cured. This method of manufacturing an ultraviolet shielding substrate is characterized in that a prepreg obtained by impregnating the glass fiber base material with a varnish containing a UV absorber and a fluorescent dye and drying the prepreg is used.

The fluorescent dyes used in the present invention are mainly diaminostilbendisulfonic acid derivatives, imidazole derivatives, oxazole derivatives, coumarin derivatives, etc. In addition, triazole, carbazole, pyridine, naphthalic acid,
Derivatives such as imidacylon can be mentioned. All have absorption peaks in the wavelength range of 300 to 450 nm.

Coumarin, an oxazole derivative, is suitable for use in the present invention.

Further, the ultraviolet absorbers used in the present invention include hydroxybenzophenones and human U-xyphenylbenzotriazoles, such as 2-
Hydroxy-4-octoxybenzophenone, 2-(-
2'-Hydroxy-51-methylphenyl-)benzotriazole, 2-(-2'-Hyl'roxy3'-t-
Butyl-5'-methylphenyl-)-benzotriazole, 2-(-2'-hydroxy-3'~monobutyl-5
゜Methylphenyl-)-5-chlorobenzotriazole, 2- (-2'-hydroxy-5'-(-octylphenyl-)-benzotriazole, 2- (-3-t-
Butyl-5-methyl-2hydroxyphenyl-5-
Examples include chlorobenzotriazole, 2-(-3-t-butyl-5-methyl-2-hydroxyphenyl-)-5-chlorobenzotriazole, and the like. All exhibit a light absorption peak in the wavelength range of 300 to 400 nsi.

Suitable for use in the present invention are 2-(-2'-hydroxy-3'-1-butyl 5'-methylphenyl-)
-5-chlorobenzotriazole, 2-(-3-t-butyl-5methyl-2-hydroxyphenyl-)-5-chlorobenzotriazole.

(Function) The purpose of combining a fluorescent dye and an ultraviolet absorber in a varnish is as follows. The lamp used in the exposure machine that is most commonly used today is 365n (42
It has an energy peak near 0 nm. 365
The n-peng peak was dealt with using an ultraviolet absorber, and 420
Since transmission of the n-peak can be prevented using reflection by the fluorescent dye, it is extremely effective to use the two types in combination.

The total concentration of these ultraviolet wa@ absorbers and fluorescent dyes is suitably from 0.11 to 10% by weight. If it is less than 0.1%, the blending effect will be small, and if it exceeds 10%, no improvement in the effect will be seen, and the properties of the resulting laminate may deteriorate. In addition, the blending ratio of ultraviolet absorber and fluorescent dye is 30
: TO to TO: 30 is preferable because it has a good balance of ultraviolet absorption.

Another feature of the manufacturing method of the present invention is that before impregnating the thermosetting resin, the glass fiber substrate is impregnated with a solution in which an ultraviolet absorber and/or a fluorescent dye is dissolved in a solvent, and then dried.

Although the total concentration depends on the impregnating conditions and the number of layers of prepreg, 0.1-10% is appropriate. If it is less than 0.1%, the effect will be small, and if it exceeds 10%, no improvement in the effect will be seen, and the properties of the obtained laminate may deteriorate.

In addition, the blending ratio of ultraviolet absorber and fluorescent dye is 30:
TO~70: 30 is preferable because it has a good balance of ultraviolet absorption.

In the prepreg obtained in this way, the ultraviolet absorber and/or fluorescent dye is uniformly and sufficiently present even in the overlapped portion of the glass fibers, and when the number of laminated sheets is small such as a thin plate laminate of 0.5- or less, However, it is possible to obtain a laminate without light exposure.

In this case, we use a recently developed and commercially available UV-shielding glass woven fabric treated with an ultraviolet absorber or fluorescent dye (for example, Nittobo's UV-shielding cloth), and we also use a varnish containing an ultraviolet absorber and fluorescent dye. Approximately the same prepreg can be obtained by applying the same.

(Effects of the Invention) According to the method of the present invention, there is a large shielding effect against light of 300 to 420 nm, and when photo solder resists coated on both sides of a laminate are simultaneously exposed, the photo solder resists on the other side are exposed. In addition to being able to prevent the trouble of drying, it also has the same electrical properties, heat resistance, machinability, and appearance (color tone) as conventional laminates, making it suitable as a manufacturing method for industrial ultraviolet-shielding circuit boards. be.

(Example) Examples and comparative examples are shown below.

Example-1 2-(-2°-hydroxy-3′-
A glass fiber woven fabric was immersed in a solution of methyl ethyl ketone and methyl cellosolve, each containing 1% of t-butyl-5'-methylcellosolve)-5-chlorobenzotriazole and a coumarin derivative as a fluorescent dye, and dried.

On the other hand, 100 parts by weight of Epicoat EP-1046 (brominated bisphenol A type epoxy resin manufactured by Yuka Shell Co., Ltd.),
4 parts by weight of dicyandiamide, 0.15 parts by weight of 2-ethyl-4-methylimidazole, and 2 parts by weight as an ultraviolet absorber.
- (-2°-hydroxy-3゛-(-butyl-5°-
methylphenyl, )-5-chlorobenzotriazole,
An epoxy resin varnish was prepared by dissolving 1 part by weight of each coumarin derivative as a fluorescent dye in a solvent with methyl ethyl ketone and methyl cellosolve so that the total solid content was 50% by weight.

The glass fiber woven fabric was impregnated with this varnish and dried to obtain an epoxy resin-impregnated prepreg with a resin content of 45%.

Layer 3 sheets of this prepreg, then layer 1 sheet of 18μ copper foil on both sides, heating temperature 165'C1 pressure 60kg/
d for 90 minutes to obtain a double-sided copper-clad laminate having a thickness of 0.6 mm.

In the same manner, eight sheets of the prepreg were stacked to obtain a double-sided steel-clad laminate having a thickness of 1.6 mm.

Example 2 A glass fiber woven fabric was dipped in advance in a solution containing only 1% of the fluorescent dye used in Example 1, and then dried. After that, the thickness was 0.6 m in the same manner as in Example-1.
A 1.6 m double-sided copper-clad laminate was obtained.

Example 3 A glass fiber woven fabric was dipped in advance in a solution containing only 1% of the ultraviolet absorber used in Example 1, and then dried. After that, the thickness was 0.6 as in Example-1.
+ss and 1.6- double-sided copper-clad laminates were obtained.

Comparative Example-1 Glass fiber mil in advance! The same procedure as in Example 1 was carried out, except that the cloth was not treated with an ultraviolet absorber and a fluorescent dye, and the epoxy resin varnish in Example-1 was not mixed with an ultraviolet absorber and a fluorescent dye. Thickness 0.6mm
A 1.6 m double-sided steel clad laminate was obtained.

The copper-clad + i-layer boards obtained in each of the above cases were etched to remove the copper, and the ultraviolet transmittance of the substrates was measured using an ultraviolet spectrophotometer (Shimadzu self-recording spectrophotometer model UV-260).

The results are shown as ultraviolet absorber lines in FIG. 1 (in the case of 1.6 iwe thickness) and FIG. 2 (in the case of 0.6 iwe thickness).

Examples 4 to 6 Only one sheet of the epoxy resin-impregnated prepreg obtained in Examples 1 to 3 was heated and pressed at 165°C and 60 kg/c for 90 minutes with 18μ copper foil laminated on both sides to reduce the thickness. A double-sided copper-clad laminate with a diameter of 0.2 as+ was obtained.

Comparative Example-2 Using only one epoxy resin-impregnated prepreg obtained in Comparative Example-1, a double-sided steel-clad laminate with a thickness of 0.2 mm was obtained in the same manner as in Examples 4 to 6 above. .

Comparative Example 3 A prib 1/g impregnated with a C epoxy resin was obtained in the same manner as in Example 1, except that the pretreatment with the C2 ultraviolet absorber and fluorescent dye was not performed. Using only one sheet of this prepreg, a double-sided copper-clad laminate with a thickness of 0.2 mm was obtained in the same manner as in Comparative Example-2.

Comparative Example-4 An epoxy resin-impregnated prepreg was obtained in the same manner as in Example-1 except that the ultraviolet absorber and fluorescent dye were not blended into the epoxy resin varnish.

Using only one sheet of this prepreg, a double-sided copper-clad laminate with a thickness of 0.2 m was obtained in the same manner as in Comparative Example-2.

The copper-clad laminates obtained in Examples 4 to 6 and Comparative Examples 2 to 4 were etched to remove copper, and photoresist (rPsR-4000 manufactured by Taiyo Ink Co., Ltd.) was applied to both sides of the substrate. Dry. A negative film was applied to one side, irradiated with ultraviolet light [No. 1 (manufactured by Oak Seisakusho) trowel, and developed with a sodium carbonate solution. The back exposure was examined to see if there was any resist remaining.

The results are shown in Table 1, and no back exposure was observed in the substrates of Examples 4 to 6.

Table 1 Laminated board used in the example for printed circuit board) 1L
- The electrical properties, heat resistance, and machinability of the laminate were equivalent to those of conventional laminates.

4,

[Brief explanation of drawings]

FIGS. 1 and 2 are graphs showing the "C" ultraviolet transmittance of the substrates obtained in Examples 1 to 3 and Comparative Example 1.

Claims (1)

[Claims] (1) A method for manufacturing a laminate in which a glass fiber base material such as a glass woven fabric or glass non-woven fabric base material impregnated with a thermosetting resin and dried is laminated and molded.
The glass fiber base material is coated with an ultraviolet absorber and/or fluorescent dye that absorbs light in the range of 0 to 450 nm in advance,
A method for producing an ultraviolet shielding circuit board, further comprising using a prepreg obtained by impregnating and drying the glass fiber base material with a varnish containing a thermosetting resin, an ultraviolet absorber, and a fluorescent dye.