JPH0682899B2 - Method of manufacturing ultraviolet shielding circuit board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION << Industrial Application Field >> The present invention has an extremely excellent effect of preventing ultraviolet ray transmission,
The present invention relates to a laminated plate for a printed circuit, which has no hue difference from that of a laminated plate produced by a conventional method and is capable of simultaneously exposing both sides of a photo-developing solder resist.

<< Prior Art >> In a printed wiring board, a solder resist is usually formed on the outermost conductor pattern layer to prevent a solder bridge between conductors during soldering or to permanently protect a conductor pattern.

There are a screen printing method and a photographic printing method using a photosensitive resin for forming the solder resist. Conventionally, the screen printing method has been often used.However, as the electronic components are miniaturized and the chip is advanced, the mounting density on the printed wiring board has become higher. Therefore, the screen printing method has high precision and workability. Practicality is becoming smaller. Therefore, instead of the screen printing method, a photographic printing method using a negative or positive mask using a photosensitive resin (photoresist) has been started.

However, in the photo printing method, when both sides of the photoresist are simultaneously exposed on the double-sided printed circuit of the laminate, the light transmitted through the photoresist at the time of exposure is further transmitted through the laminate,
It has become known that the photoresists on the opposite surfaces are also exposed, and the accuracy of the solder resist, which is the original purpose, becomes insufficient. Especially the thickness of the laminate is 1.6m
It is known that the light transmittance is large when the thickness is m or less.

For this reason, use a photoresist film with a large photoresist thickness (50 to 80μ), or
As shown in 40, a laminated board using a polyimide-modified resin is used as a base material which is the outermost surface of the laminated board. However, if the thickness of the photoresist is increased, an extra curing time is required after the exposure and development in order to sufficiently exhibit the performance as the solder resist. On the other hand, the use of a polyimide-modified resin for a part of the laminated plate has a drawback that the cost is large and the prevention of light transmission is still insufficient. In order to eliminate these drawbacks, a method has been considered in which a light-shielding substance is contained in the laminate so as to prevent light transmission (JP-A-54-32769).

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

Further, if the content rate is reduced, there is a drawback that the effect of preventing light transmission is small particularly in a laminated plate having a thickness of 1.2 mm or less. In addition, it was found that even in the case of inorganic UV-screening agents, the effect of oxides was particularly effective. However, when the resin was blended with the resin in an amount capable of preventing light transmission and impregnated by coating, due to the difference in specific gravity between the resin and the inorganic oxides. However, it has the drawback that it is difficult to impregnate it uniformly, and the light transmittance of the produced laminate varies.

Also, with the improvement in accuracy of photo solder resists in recent years, a laminated plate that shields light in a longer wavelength region (near 420 nm) than the conventional ultraviolet region is desired, and a conventional ultraviolet absorber is blended alone. However, it is becoming difficult to satisfy the prevention of back exposure. In order to deal with this, a method of incorporating a dye or a pigment at the time of manufacturing a laminated plate is taken, but in either method, there is a drawback that the appearance of the laminated plate is greatly different from the conventional color tone.

Furthermore, recently, the tendency of laminated sheets to become thin has become stronger, and a new problem has arisen in which back-exposure occurs in the overlapped portions of glass fibers, etc. simply by blending a conventional thermosetting resin with an ultraviolet absorber or a fluorescent dye. However, the prevention of light transmission of the thin laminated plate is still insufficient.

<< Problems to be Solved by the Invention >> An object of the present invention is to provide a laminate having excellent effects of preventing ultraviolet ray transmission while maintaining performance and appearance as a laminate for printed circuits. is there.

<< Means for Solving the Problem >> The present invention provides a method for producing a laminated plate, which comprises laminating a glass woven fabric or a glass non-woven fabric substrate or the like (referred to as a glass fiber substrate) impregnated with a thermosetting resin and drying the laminated substrate, and And an ultraviolet absorber that absorbs light in the visible region (wavelength 300 to 450 nm) and /
Alternatively, a fluorescent dye is applied to a glass fiber base material in advance, and the glass fiber base material is impregnated into a varnish containing a thermosetting resin mixed with an ultraviolet absorber and a fluorescent dye. And a method for manufacturing an ultraviolet shielding circuit board.

The fluorescent dye used in the present invention is mainly a diaminostilbene disulfonic acid derivative, an imidazole derivative, an oxazole derivative, a coumarin derivative, and the like, and also triazole, carbazole, pyridine, naphthalic acid,
Examples thereof include derivatives such as imidazolone. All have an absorption peak in the wavelength region of 300 to 450 nm.

Suitable for use in the present invention are coumarins, oxazole derivatives.

Further, the ultraviolet absorbers used in the present invention include hydroxybenzophenones and hydroxyphenylbenzotriazoles, and examples thereof include 2-
Hydroxy-4-octoxybenzophenone, 2-(-
2'-hydroxy-5'-methylphenyl-) benzotriazole, 2-(-2'-hydroxy-3'-t-butyl-5'-methylphenyl-)-benzotriazole, 2-(-2'-hydroxy -3'-t-butyl-
5'-methylphenyl-)-5-chlorobenzotriazole, 2-(-2'-hydroxy-5'-t-octylphenyl-)-benzotriazole, 2-(-3-t-
Butyl-5-methyl-2-hydroxyphenyl-)-5
-Chlorobenzotriazole, 2-(-3-t-butyl-5-methyl-2-hydroxyphenyl-)-5-chlorobenzotriazole and the like can be mentioned. Both show a light absorption peak in the wavelength region of 300 to 400 nm.

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

<< Action >> The purpose of the combined use of the fluorescent dye and the ultraviolet absorber in the varnish is as follows. The lamps used in the exposure machines that are most frequently used at present have energy peaks near 365 nm and 420 nm. An ultraviolet absorber corresponds to the peak of 365 nm, and transmission of the peak of 420 nm can be prevented by utilizing reflection by a fluorescent dye. Therefore, it is extremely effective to use two kinds in combination.

The total concentration of these UV absorbers and fluorescent dyes is 0.
1-10% by weight is suitable. If it is less than 0.1%, the compounding effect is small, and if it exceeds 10%, the effect is not improved, and the properties of the obtained laminate may be deteriorated. Further, the mixing ratio of the ultraviolet absorber and the fluorescent dye is preferably 30:70 to 70:30 because of good balance of ultraviolet absorption.

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

Although the total concentration of these depends on the number of laminated prepregs impregnated, 0.1-10% is suitable. If it is less than 0.1%, the effect is small, and if it exceeds 10%, the effect is not improved, and the properties of the obtained laminate may be deteriorated. Further, the mixing ratio of the ultraviolet absorber and the fluorescent dye is preferably 30:70 to 70:30 because of good balance of ultraviolet absorption.

The prepreg thus obtained has a uniform and sufficient amount of the ultraviolet absorber and / or the fluorescent dye even in the overlapped portion of the glass fibers, and even when the number of laminated sheets is small, such as a thin laminated sheet of 0.5 mm or less, the back side It is possible to obtain a laminated plate that is not exposed to light.

At this time, a varnish containing a UV-shielding glass woven fabric (for example, a UV-shielding cloth manufactured by Nitto Boseki) treated with a UV-absorber or a fluorescent dye, which has been recently developed and marketed, and further contains a UV-absorber and a fluorescent dye. It is possible to obtain almost the same prepreg even if the coating is performed by using.

<< Effects of the Invention >> According to the method of the present invention, when the photosolder resists coated on both surfaces of the laminated plate have a large shielding effect against light of 300 to 420 nm, the photosolder resists on the other surfaces are exposed to each other. In addition to being able to prevent such troubles, the electrical properties, heat resistance, machinability, and appearance (color tone) of conventional laminates are similar, making it suitable as an industrial method for manufacturing an ultraviolet shielding circuit board. is there.

<< Example >> An example and a comparative example are shown below.

Example-1 2-(-2'-hydroxy-3'- as an ultraviolet absorber
A woven glass fiber cloth was dipped in a solution of t-butyl-5'-methylphenyl-)-5-chlorobenzotriazole, methyl ethyl ketone and methyl cellosolve each containing 1% of a coumarin derivative as a fluorescent dye, and dried.

On the other hand, Epicoat EP-1046 (brominated bisphenol A type epoxy resin manufactured by Yuka Shell Co., Ltd.) 100 parts by weight, dicyandiamide 4 parts by weight, 2-ethyl-4-methylimidazole 0.1.
15 parts by weight, 2-(-2'-hydroxy-3'-t-butyl-5'-methylphenyl-) as an ultraviolet absorber
-5-chlorobenzodriazole, 1 part by weight of coumarin derivative as a fluorescent dye, and 50% as a total solid content, respectively.
Epoxy resin varnish was prepared by dissolving it in a solvent with methyl ethyl ketone and methyl cellosolve so as to have a weight percentage.

This varnish was impregnated with the woven glass fiber cloth and dried to obtain an epoxy resin-impregnated prepreg having a resin content of 45%.

Three pieces of this prepreg are laminated, and 18μ copper foil is further laminated on both sides of each prepreg, and heated and pressed at a heating temperature of 165 ° C. and a pressure of 60 kg / cm ² for 90 minutes to form a double-sided copper-clad laminate with a thickness of 0.6 mm. Obtained.

Similarly, eight prepregs were stacked to obtain a double-sided copper-clad laminate having a thickness of 1.6 mm.

Example-2 A glass fiber woven fabric was immersed in a solution containing only 1% of the fluorescent dye used in Example-1 in advance in the glass fiber woven fabric and dried. After that, double-sided copper clad laminates having thicknesses of 0.6 mm and 1.6 mm were obtained in the same manner as in Example-1.

Example-3 A glass fiber woven fabric was immersed in a solution containing only 1% of the ultraviolet absorber used in Example-1 in advance in the glass fiber woven fabric and dried. After that, the thickness is 0.6 mm in the same manner as in Example-1.
A 1.6 mm double-sided copper clad laminate was obtained.

Comparative Example-1 Except that the glass fiber woven fabric was not previously treated with the ultraviolet absorber and the fluorescent dye, and the epoxy resin varnish in Example-1 was not blended with the ultraviolet absorber and the fluorescent dye. Same as Example-1 with thickness of 0.6mm and 1.6mm
A double-sided copper clad laminate was obtained.

The copper clad laminate obtained in each of the above examples was etched to remove copper, and the ultraviolet transmittance of the substrate was measured by an ultraviolet spectrophotometer (Shimadzu Autograph UV6 (60 type)).

The results are shown in Fig. 1 (when the thickness is 1.6 mm) and Fig. 2 (0.6 mm).
In the case of thickness), it is shown as an ultraviolet absorption curve.

Examples -4 to 6 Only one epoxy resin-impregnated prepreg obtained in Examples -1 to 3 was heated and pressed for 90 minutes at 165 ° C. and 60 kg / cm ² together with 18 μ copper foil laminated on both sides thereof to obtain a thickness. 0.2m
A double-sided copper clad laminate of m was obtained.

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

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

Comparative Example-4 An epoxy resin-impregnated prepreg was obtained in the same manner as in Example-1, except that the ultraviolet absorber and the fluorescent dye were not mixed in the epoxy resin varnish.
Using only one prepreg, a double-sided copper clad laminate having a thickness of 0.2 mm was obtained in the same manner as in Comparative Example-2 below.

The copper clad laminates obtained in Examples 4 to 6 and Comparative Examples 2 to 4 were etched to remove copper, and a photoresist (“PSR-4000” made by Taiyo Ink Co., Ltd.) was applied to both surfaces of the substrate. Dried. A negative film was applied to one surface, ultraviolet rays were irradiated with an ultraviolet ray irradiator (manufactured by Oak Manufacturing Co., Ltd.), and developed with a sodium carbonate solution. The back exposure was examined by the presence or absence of residual resist.

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

The electrical properties, heat resistance, and machinability of the laminated board used in the examples for printed circuit boards were equivalent to those of the conventional laminated board.

[Brief description of drawings]

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

Claims (1)

[Claims] 1. A method for producing a laminated plate, comprising laminating a glass fiber substrate such as a glass woven fabric or a glass nonwoven fabric substrate, which is impregnated with a thermosetting resin and dried, in the ultraviolet and visible region (wavelength 300 to 450 nm). The glass fiber base material is applied to the glass fiber base material in advance with an ultraviolet absorber and / or a fluorescent dye that absorbs the light, and the glass fiber base material is added to a varnish containing the ultraviolet absorbent and the fluorescent dye in a thermosetting resin. A method of manufacturing an ultraviolet-shielding circuit board, which comprises using a prepreg impregnated with and dried.