JPH032547A - Method for inspecting circuit pattern - Google Patents

Abstract

PURPOSE:To accurately inspect circuit patterns with high efficiency by integrally coupling the high fluorescence imparted to an insulating layer and the specific stimulating light to strongly stimulate this fluorescence. CONSTITUTION:A wiring board consisting of an insulating substrate formed by perfecting of the curing of a resin compsn. contg. an epoxy resin, the diaminodiphenyl methane compd., which is expressed by formula, and is compounded at the ratio ranging 5 to 20 pts.wt. per 100 pts.wt. this epoxy resin, and a curing accelerator in the base material and the circuit patterns formed on this insulating substrate is irradiated with 350 to 500nm stimulating light. The abnormality of the circuit patterns is decided in comparison with the normal circuit patterns by utilizing the property that while the insulating patterns formed between the circuits of the circuit patterns exhibit the extreme by high fluorescence to 350 to 500nm stimulating light the circuit patterns do not exhibit the fluorescence. The circuit patterns are accurately inspected with the high efficiency by the fluorescence emitted by this stimulating light.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a printed wiring board comprising an insulating substrate in which an epoxy resin has been completely cured in an insulating base material, and a circuit pattern formed on the insulating substrate. The present invention relates to a method for inspecting circuit patterns of wiring boards such as the above.

[Conventional technology]

Epoxy resins have traditionally been widely used as resins for laminates and the like. Conventionally known methods for inspecting circuit patterns on printed wiring boards made from such laminates include a direct conduction method using a probe, a method using reflected light from a metal conductor circuit pattern using a metallurgical microscope, and a method using soft X-rays. However, recently, as a method for highly efficient inspection with good surface accuracy, printed wiring boards are exposed to excitation light by imparting fluorescence to the insulating layer, which emits fluorescence in response to excitation light. The conductor circuit pattern is divided into the part of the conductor circuit pattern that does not emit light, and the part of the insulating pattern that is exposed between the circuits of the conductor circuit pattern and emits light in response to the excitation light, and the excitation light is irradiated by utilizing the difference in luminescence of these parts. A method of inspecting a circuit pattern is being attempted, in which an abnormality in a circuit pattern is inspected by comparing it with a normal circuit pattern. The success or failure of this testing method naturally depends on the high luminescence imparted to the insulating layer and the integral combination of excitation light that strongly excites luminescence. In particular, the luminescence imparted to the insulating layer decreases as the thickness of the insulating layer becomes thinner (and also decreases when the insulating layer is blackened). It is necessary to give gender.

[Problem to be solved by the invention]

Therefore, the present invention relates to a novel circuit pattern inspection method that can accurately and efficiently inspect circuit patterns using fluorescence emitted by excitation light. The problem is solved by integral combination of specific excitation light that strongly excites this fluorescence.

[Means to solve the problem]

The method for inspecting a circuit pattern formed on an insulating substrate according to the present invention includes: (a) epoxy resin; (b) 5 to 20 parts by weight per 100 parts by weight of the epoxy resin;
Contains a diaminodiphenylmethane compound represented by the following general formula (R, R2 is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms) blended in an amount within the range of parts by weight, (iii) and a curing accelerator. The resin composition was applied to a wiring board consisting of an insulating substrate that had been completely cured in the base material and a circuit pattern formed on this insulating substrate.
It is characterized by irradiating m excitation light.

The present invention will be explained in detail below. The insulating substrate constituting the wiring board applied to the circuit pattern inspection method of the present invention contains epoxy resin and 5 to 2 parts by weight per 100 parts by weight of this epoxy resin.
The resin composition containing a diaminodiphenylmethane compound and a curing accelerator blended in an amount in the range of 0 parts by weight is limited to an insulating substrate in which curing is completed in the base material. Here, the epoxy resins include bisphenol A epoxy resins and halogenated bisphenol A epoxy resins that have flame retardancy, or novolac epoxy resins that are used in combination to improve heat resistance, and epoxy resins that are resistant to these. Examples include halogenated novolac type epoxy resins that have been imparted with flammability. And 10 epoxy resins like this
The reason why the amount of the diaminodiphenylmethane compound blended is limited to 5 to 20 parts by weight relative to 0 parts by weight is that if the blending amount is less than the lower limit of 5 parts by weight, the fluorescence against excitation light will be weak.
This is because if the upper limit of 20 parts by weight is exceeded, the curing speed of the epoxy resin is too fast and it becomes difficult to use it in a resin varnish. In the present invention, this diaminodiphenylmethane compound is a curing agent selectively employed as a curing agent for epoxy resin, and has a novel action as a fluorescent agent that emits fluorescence in response to light belonging to a specific wavelength. at the same time.

As curing accelerators, tertiary amines such as hensyldimethylamine, 2ethyl4methylimidazole (2E4
An imidazole such as MZ) is used, and its blending ratio is 0.05 parts by weight per 100 parts by weight of the epoxy resin.
~1 part by weight is suitable. Explaining the process by which the above-mentioned components promote the crosslinking reaction in the base material and give a solid content of the cured resin, the above-mentioned components are contained in a resin varnish dissolved in a solvent. Here, as a solvent, dimethylformamide (DMF), methyl ethyl ketone (MEK), acetone, methyl cellosolve, dimethyl acetamide, dioxane, etc. are used alone or as a mixture, and the resin content is 40 to 80% by weight, preferably 55% by weight.
It can be used in an amount of up to 70% by weight. After impregnating the resin face prepared in this way into a base material such as glass cloth, the solvent is evaporated by drying and the reaction of the epoxy resin is progressed to semi-cure the resin composition in the base material to form a prepreg. do. The type of the base material is not particularly limited. Glass cloth or the like is usually used. In addition, inorganic fiber cloth such as quartz fiber cloth, highly heat-resistant organic fiber cloth such as polyimide resin fiber cloth, etc. may be used. The temperature during semi-curing is preferably 140 to +70'C. 17
If the temperature exceeds 0°C, the reaction of the epoxy resin will proceed too much, and the interlayer adhesion of the obtained prepreg will decrease, causing a decrease in performance as an insulating substrate, such as water absorption. A metal foil-covered insulation that can form a circuit pattern by stacking several sheets of prepreg obtained in this way and then layering a metal foil such as copper, nickel, or aluminum, and then hot-pressing this under commonly used conditions. This metal foil is then etched using a subtractive method, which is a commonly used circuit forming method, to obtain a wiring board with a circuit pattern formed on the insulating substrate. Therefore, the insulating substrate is divided into two circuit patterns and an insulating pattern formed by the insulating substrate exposed between the circuits of this circuit pattern. Note that a wiring board in which a circuit pattern is formed on an insulating substrate by an additive method can also be used as the wiring board in this invention.

A wiring board according to the present invention comprising the above insulating substrate and a circuit pattern formed on the insulating substrate has a wavelength of 350 to 350.
This method utilizes the property of emitting fluorescence especially when exposed to light of 500 nm. In other words, while the insulating pattern formed between the circuits of the circuit pattern exhibits significant fluorescence in response to excitation light of 350 to 500 nm, the circuit pattern does not exhibit fluorescence to detect abnormalities in the circuit pattern. This can be determined by comparing it with the circuit pattern.

In particular, the thinner the insulating layer, the lower the fluorescence of the insulating layer.
In addition, since there is a property that the fluorescence intensity decreases when an insulating layer that has been treated with blackening is included, for example, when inspecting a circuit pattern of an insulating substrate of 0.2 mm or less or a wiring board that has an insulating substrate that has been treated with blackening, the fluorescence intensity of the insulating layer is increased. This is extremely useful. Specific examples will be given below.

〔Example〕

Example I As an epoxy resin, brominated epoxy resin (Tobu Kasei Co., Ltd., Y D B-500, epoxy equivalent weight 500) was used at 10
0 parts by weight, R with the above diaminodiphenylmethane compound
, and 3,3'-diethyl-4,4'- where R2 is an ethyl group
20 parts by weight of diaminodiphenylmethane and 0.0 parts of 2E4MZ as a curing accelerator. 1 part by weight, and M as a solvent.
EK,l! A resin varnish was prepared by adding the above-mentioned resin content to 65% by weight, and this resin varnish was impregnated into a 0.1 mm glass cloth and dried to obtain a prepreg. Then, copper foil with a thickness of 18 μm was placed on both sides of this prepreg, and this was sandwiched between metal plates and hot-press molded at a molding pressure of 50 kg/ci and a temperature of 170°C for 100 minutes, and this copper foil was etched. The wiring board has a circuit pattern on an insulating substrate and an insulating pattern in which the insulating substrate is exposed between the circuits of the circuit pattern. This wiring board was irradiated with excitation light of 350 to 500 nm using a spectrofluorometer, and the maximum value of the fluorescence intensity that appeared at that time was shown in Table 1 as the fluorescence intensity. In addition, a fluorescent pattern inspection device using 442 nm excitation light was applied to this wiring board of 300 mm x 500 mm, and the conductor width of the circuit pattern, conductor spacing,
As a result of inspection for disconnections, short circuits, pinholes, copper residue, and copper chips, the circuit patterns that were detected as abnormal using the fluorescent pattern inspection device were again observed using a microscope, and as a result, it was confirmed that there were no abnormalities in the circuit patterns. The number of pieces, that is, the number of pieces erroneously detected by the fluorescent pattern inspection device was defined as the inspection accuracy, and the results are also shown in Table 1.

Example 2 The same procedure as in Example 1 was carried out except that 14 parts by weight of 3,3'-diethyl-4,4'diaminodiphenylmethane used in Example 1 was used, and 0.6 parts by weight of dicyandiamide was added. Obtained the results in the table.

Example 3 5 parts by weight of 3,3'-diethyl-4,4'diaminodiphenylmethane used in Example 1, 1 part of dicyandiamide
．． The same procedure as in Example 1 was carried out except that 8 parts by weight was added, and the results shown in Table 1 were obtained.

Comparative Example: The 3,3'diethyl-4,4'diaminodiphenylmethane used in Example 1 was not blended, and 2.5% of dicyandiamide was used.
The same procedure as in Example 1 was carried out except that the parts by weight were added, and the results shown in Table 1 were obtained.

As is clear from Table 1, according to the examples of the present invention according to Examples 1 to 3, the fluorescence intensity increases, and as a result, specifically, the high fluorescence imparted to the insulating layer can be strongly excited. The accuracy of inspection using this property can also be improved.

Table 1 *1 Number of incorrectly detected pieces per wiring board○...0
~5 pieces×...50 to 200 pieces Example 4 An insulating substrate obtained by hardening the prepreg in Example 1 and a circuit pattern formed on this insulating substrate were printed with a 0.5 mm inner layer that was blackened. The prepreg obtained in Example 1 was placed on both sides of the wiring board, and 18
A copper foil with a thickness of μm was arranged, sandwiched between metal plates 1 and laminated under the heat and pressure conditions of Example 1, and then etched to obtain a circuit pattern on the insulating substrate. The strength and circuit pattern were inspected. These results are shown in Table 2.

Example 5 The same procedure as in Example 4 was carried out except that the inner layer printed wiring board and prepreg of Example 1 used in Example 4 were changed to the inner layer printed wiring board and prepreg of Example 2. Shown in the table.

Example 6 The same procedure as in Example 4 was carried out except that the inner layer printed wiring board and prepreg of Example 1 used in Example 4 were changed to the inner layer printed wiring board and prepreg of Example 3, and these results were compared to the second example. Shown in the table.

Comparative Example 2 The same procedure as in Example 4 was carried out except that the inner layer printed wiring board and prepreg of Example 1 used in Example 4 were changed to the inner layer printed wiring board and prepreg of Comparative Example 1. As shown in Table 2, the present invention enables inspection of circuit patterns by integrally combining high fluorescence imparted to an insulating layer and specific excitation light that strongly excites this fluorescence. This can be carried out with high precision and high efficiency using fluorescence emitted by excitation light.

Claims (1)

[Claims] (1) (a) Epoxy resin (b) 5 to 20 parts by weight per 100 parts by weight of the epoxy resin
A diaminodiphenylmethane compound represented by the following general formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (R_1 and R_2 are hydrogen atoms or alkyl groups having 1 to 4 carbon atoms), which is blended in amounts within the range of parts by weight. c) and a wiring board consisting of an insulating substrate on which the resin composition containing a curing accelerator has been completely cured in the base material and a circuit pattern formed on this insulating substrate, with a thickness of 350 to 500 nm.
A circuit pattern inspection method characterized by irradiating with excitation light.