JPH032548A - 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 orthocresol novolak compounded at the ratio ranging 10 to 25 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 extremely 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. [Prior Art] Epoxy resins have been widely used as resins for laminated boards 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, the printed wiring board does not emit light in response to excitation light by imparting fluorescence to the insulating layer, which emits fluorescence in response to excitation light. The conductor circuit button part,
The conductor circuit pattern is divided into parts of the insulating pattern that are exposed between the circuits and emit light in response to excitation light, and abnormalities in the circuit can be corrected by irradiating the excitation light using the difference in luminescence between these parts. A method of inspecting a circuit pattern by comparing it with a similar circuit pattern is being tried. 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 includes a blackened insulating layer. need to be granted.

[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 a circuit board according to the present invention includes: (a) epoxy resin; (b) 10 to 2 parts by weight per 100 parts by weight of the epoxy resin;
An insulating substrate in which a resin composition containing an orthocresol novolak (c) and a curing accelerator, which is blended in an amount within the range of 5 parts by weight, is completely cured in a base material, and a circuit formed on this insulating substrate. 350~500n on a wiring board consisting of a pattern
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 10 to 10 parts by weight of this epoxy resin.
The resin composition containing orthocresol novolac and a curing accelerator blended in an amount within the range of 25 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 novolanc 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.

The reason why orthocresol novolak is limited to 10 to 25 parts by weight per 100 parts by weight of such epoxy resin is that if the amount is less than the lower limit of 10 parts by weight, the fluorescence against excitation light will be weak, and the upper limit of This is because if the amount exceeds 25 parts by weight, the curing speed of the epoxy resin will be fast, making it difficult to use it in a resin varnish. This orthocresol novolak is a curing agent selectively employed as a curing agent for epoxy resins in this invention, and has a novel action as a fluorescent agent that emits fluorescence in response to light belonging to a specific wavelength. It has at the same time.

As curing accelerators, tertiary amines such as benzyldimethylamine, 2ethyl4methylimidazur (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 appropriate. 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., alone or in combination, are used with an epoxy resin content of 40 to 80% by weight, preferably 55 to 80% by weight. It can be used in an amount of 70% by weight.

After impregnating a base material such as glass cloth with the resin varnish prepared in this way, the reaction of the epoxy resin is progressed while the solvent is evaporated by drying, and the resin composition in the base material is semi-cured to form a prepreg. shall be.

The type of the base material is not particularly limited. Usually, glass cloth or the like is 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 170°C. If the temperature exceeds 170°C, the reaction of the epoxy resin will proceed too much, and the interlayer adhesive strength of the obtained prepreg will decrease, causing a decrease in performance as an insulating substrate, such as water absorption rate. 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 one circuit pattern 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 the present 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.
It 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 a circuit pattern exhibits significant fluorescence in response to excitation light of 350 to 500 nm, the circuit pattern does not exhibit fluorescence, which can be used to detect abnormalities in the circuit pattern. This can be determined by comparing it with the circuit button. In particular, the fluorescence of the insulating layer decreases as the thickness of the insulating layer becomes thinner, and it also decreases when the insulating layer includes a blackened insulating layer.
For example, in inspecting a circuit pattern of a wiring board having an insulating substrate of 0.2 mm or less or a blackened insulating substrate, it is extremely useful to increase the fluorescence intensity of the insulating layer.

Specific examples will be given below.

[Example] Example 1 As an epoxy resin, 10% of brominated epoxy resin (Tobu Kagasha, YD B-500, epoxy equivalent 500) was used as an epoxy resin.
0 parts by weight, 25 parts by weight of orthocresol Novola ivy with n=7 shown in the structural formula below (Tobu Kagasha, D-5, hydroxyl equivalent 121.8, softening point 96°C), hardened. A resin varnish was prepared by adding 0.1 parts by weight of 2E4MZ as an accelerator and a mixture of MEK and DMF as a solvent so that the resin content was 65% by weight. A prepreg was obtained by impregnating and drying the glass cloth.

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 a molding pressure of 50 kg/c was applied.
Ifl, hot pressing at a temperature of 170'C for 100 minutes,
This copper foil was etched to obtain a wiring board having a circuit pattern on an insulating substrate and an insulating pattern in which the insulating substrate was 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 taken as the first fluorescence intensity.
Shown in the table. In addition, we applied a fluorescent pattern inspection device using excitation light of 442r+m to this 300mm x 500m+n wiring board, and inspected the circuit pattern for conductor width, conductor spacing, breaks, shorts, pinholes, copper residue, and copper chips. The circuit patterns detected as abnormal by the pattern inspection device are observed again using a microscope, and as a result, the number of circuit patterns that are confirmed to have no abnormality, that is, the number of circuit patterns detected incorrectly by the fluorescent pattern inspection device, is inspected. The accuracy results are also shown in Table 1.

Example 2 Orthocresol novolak used in Example 1 with n=7 (Tobu Kagasha, D-5, hydroxyl equivalent: 121.8
Example 1 was carried out in the same manner as in Example 1, except that 17 parts by weight (softening point: 96°C) and 0.6 parts by weight of dicyandiamide were added, and the results shown in Table 1 were obtained.

Example 3 Orthocresol novolak n-7 used in Example 1 (
Tobu Kagasha, D-5, hydroxyl equivalent: 121.8 Softening point: 96
Example 1 was carried out in the same manner as in Example 1, except that 10 parts by weight of dicyandiamide (10 parts by weight) and 1 part by weight of dicyandiamide were added, and the results shown in Table 1 were obtained.

Comparative Example 1 Orthocresol novolak n=7 used in Example 1 (Tobu Kagasha, D-5, hydroxyl equivalent: 121.8
Softening point: 96°C) is not added, dicyandiamide 2°5
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 Examples 1 to 3 of the present invention, 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 O...
0 to 5 pieces x 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 combined into a 0.5 mm inner layer that was blackened. The prepreg obtained in Example 1 was placed on both sides of the printed wiring board, and 18
μm copper foil was arranged, sandwiched between metal plates, laminated and molded under the heat and pressure conditions of Example 1, and further etched to obtain a circuit pattern on the insulating substrate. The circuit pattern was 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 procedure was carried out in the same manner as in Example 4, except that the inner layer printed wiring board and prepreg of Example 4 used in Example 4 were changed to the inner layer printed wiring board and prepreg of Comparative Example 1, and these results were compared to Example 2. As is clear from Table 2, according to the examples of the present invention according to Examples 4 to 6, the fluorescence intensity increases, and as a result, specifically, the high fluorescence imparted to the insulating layer is strongly excited. This property can be used to improve the accuracy of inspections.

This can be done at a reasonable rate.

Claims (1)

[Claims] (1) (A) Epoxy resin, (B) 10 to 2 parts by weight per 100 parts by weight of the epoxy resin.
An insulating substrate in which a resin composition containing an orthocresol novolak (c) and a curing accelerator, which is blended in an amount within the range of 5 parts by weight, is completely cured in a base material, and a circuit formed on this insulating substrate. 350 to 500 nm on a wiring board consisting of a pattern
A circuit pattern inspection method characterized by irradiating with excitation light.