JPH06112607A - Circuit board coping with optical inspection device type - Google Patents

Abstract

PURPOSE:To acquire a lamination board which can cope with a fluorescence type optical inspection device by adding specific fluorescent brightener to varnish which is formed by mixing hardening agent and hardening accerelator with epoxy resin. CONSTITUTION:At first, 0.1wt.% of fluorescent brightener of the formula of 100wt.% of epicoat Ep-5049, 25wt.% of Ep-180S75, 2.0wt.% of dicyandiamide, and 0.07 wt.% of 2-ethyl-4-methyl imidazole is mixed and dissolved by solvent of acetone and methyl cellosolve to make a total solid amount 50wt.%. The varnish is infiltrated in a glass cloth base material to acquire a glass cloth prepreg of 48% of resin. A 0.17mm-thick double-sided copper clad laminated board is formed by heating, pressurizing and molding one sheet of prepreg, whereon one sheet of 35mum-thick copper foil is laminated on each of the both sides thereof, for 90min at a temperature of 180 deg.C and a pressure of 400N/cm<2>. Thereby, a lamination board which can cope with a fluorescence type optical inspection device can be acquired.

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 circuit board used in electronic equipment and the like.

[0002]

2. Description of the Related Art Conventionally, inspections for extracting defective products such as circuit disconnection, line loss, copper foil remaining, etc. on a conductor pattern layer of a printed wiring board have been conducted visually by a person or by passing an electric current between the circuits. However, as patterns become finer and finer, it becomes impossible to detect defective products by these methods. Therefore, an optical inspection machine has been used, which optically captures information by irradiating an inspection object with a laser beam and detects an abnormality in the appearance of the pattern. Generally, there are a reflected light type method and a fluorescence type method in an optical inspection machine. In the reflection method, the laser light is directly applied to the copper foil and the reflected light is detected, so that it is possible to judge the flaws of the copper foil, and therefore it is often used for the outer layer inspection. On the other hand, the fluorescent method is often used for inner layer inspection because the pattern can be recognized even at the bottom portion. However, in the case of the fluorescent method, the conventional printed wiring board in which the epoxy resin prepreg obtained by mixing the epoxy resin with the curing agent and the curing accelerator, and impregnating and drying the same in the glass substrate is used as the insulating substrate. When the part is irradiated with laser light, there is a drawback that the fluorescence emitted is weak and the occurrence rate of false alarms is high due to the influence of the circuit on the back surface and the dust adhering to the surface of the base material.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to obtain a laminated board which can be used in a fluorescence type optical inspection machine while maintaining the performance as a conventional printed wiring board. For this reason, the present inventor efficiently laminates a prepreg obtained by mixing a specific optical brightener that efficiently absorbs light near 440 nm and emits light of 450 to 550 nm with a conventional epoxy resin varnish. The present invention has been completed.

[0004]

The present invention provides an epoxy resin varnish with the following chemical formula [I]:

[Chemical 2]

The optical brightening agent represented by the formula (1) is preferably blended in an amount of 0.05 to 0.2% by weight with respect to the resin solid content, and the epoxy resin prepreg obtained by impregnating and drying the base material is laminated and molded. The present invention relates to a circuit board corresponding to the fluorescence type optical inspection machine. The fluorescent whitening agent of the above formula [I] used in the present invention has a fluorescent property due to the stilbene structure,
efficiently absorbs UV and visible light near nm
Since it emits fluorescence of 0 to 550 nm and the amount of fluorescence is large, excellent effects can be obtained with a small amount of the compound in the present invention.

The blending amount of this optical brightening agent is 0.05 to 0.2% by weight based on the resin solid content. If it is less than 0.05% by weight, the characteristics as a circuit board for a fluorescent optical inspector cannot be satisfied, and if it exceeds 0.2% by weight, the resin may be hardened or the characteristics of the circuit board may be affected. So not suitable. Furthermore, this fluorescent whitening agent dissolves well in a solvent, is homogenized in a varnish, and does not dissolve or chemically change in an alkali during a plating process or an acid during an etching process even after the substrate is manufactured, and thus the laminated plate There is no problem in the processing step.

[0007]

EXAMPLES << Example 1 >> Epicoat Ep-5049 1
00 parts by weight, Ep-180S75 25 parts by weight, dicyandiamide 2.0 parts by weight, 2-ethyl-4-methylimidazole 0.07 parts by weight, and 0.1 part by weight of the fluorescent whitening agent of the chemical formula [I]. Then, it was dissolved in a solvent of acetone and methyl cellosolve so that the total solid content became 50% by weight. This varnish is impregnated into a glass woven base material to form a resin component 4
8% glass woven prepreg was obtained. 1 piece of this prepreg and 1 piece of 35 μm copper foil on both sides of the prepreg,
It was heated and pressed at 80 ° C. and a pressure of 400 N / cm ² for 90 minutes to obtain a double-sided copper clad laminate having a thickness of 0.17 mm.

Comparative Example 1 A double-sided copper clad laminate having a thickness of 0.17 mm was obtained in the same manner as in Example 1 except that the prepreg containing no optical brightening agent was used. <Comparative Example 2> The above-mentioned optical brightening agent was added to a glass woven fabric substrate in an amount of 0.1
A thickness of 0.17 was obtained in the same manner as in Example 1 except that a prepreg made by impregnating the above-mentioned epoxy resin varnish (however, containing no optical brightening agent) with a weight% of which was adhered was used.
A double-sided laminated board of mm was obtained.

Next, in the obtained copper-clad laminate, one surface copper foil was etched to form two disconnection portions (10 μm).
A signal line pattern (circuit width 150 μm, circuit interval 150 μm) having the above was formed. The number of defects of this circuit board was measured by a fluorescence type optical inspection machine. In Example 1, the gain box (Gain
The level of Box) is appropriate, and the minimum value of the fluorescence amount is sufficiently large, so that the fine pattern portion can be easily recognized without any false alarm due to amplification. On the contrary, in Comparative Examples 1 and 2, the minimum value of the fluorescence amount was small and the amplification factor was increased, so that many false reports were seen in the fine pattern portion, and the result that the compatibility with the inspection machine was poor was obtained. The above results are shown in Tables 1 and 2.

[0010]

[Table 1]

[0011]

[Table 2] The laminated plate obtained in Example 1 was measured for electrical characteristics, heat resistance, machinability and the like as a printed circuit board, and good results equivalent to those of the conventional laminated plate were obtained.

[0012]

The printed circuit board of the present invention has the following features. (1) By adding a slight amount of optical brightener to the varnish,
Efficiently absorbs light near 440 nm, 450 to 550
Since it emits fluorescence of nm, it is sufficiently compatible with the fluorescence type optical inspection machine and can detect the circuit failure accurately. (2) The electrical characteristics, heat resistance, machinability, etc. of the circuit board are the same as those of the conventional ones and good.

Claims (2)

[Claims] 1. A varnish prepared by blending an epoxy resin with a curing agent and a curing accelerator, and a varnish represented by the following chemical formula [I]: A circuit board corresponding to a fluorescent type optical inspecting machine, comprising a base material impregnated with a varnish prepared by adding the optical brightening agent represented by the above, and a laminated epoxy resin prepreg. 2. The circuit board according to claim 1, wherein in the epoxy resin varnish, the fluorescent whitening agent is blended in an amount of 0.05 to 0.2% by weight based on the resin solid content.