JPH0518910A - Laminated-plate inspecting method - Google Patents

Abstract

PURPOSE:To obtain the detecting method which con detect micro-cracks sensitively and can perform observation with the expanse of the micro-cracks as a plane. CONSTITUTION:As a laminated-plate inspecting method, it s preferable that at least two or more methods described, below are combined and used. A fluorescence agent is made to penetrate, into a crack generated in the machined laminated plate. Then, ultraviolet rays, visible rays, X rays alpha rays, beta rays or the like are applied on the fluorescence agent. The fluorescence obtained by exciting the fluorescence agent is observed. As the method for the penetration of the fluorescence agent, the laminated plate is immersed into the solution of the fluorescence agent, and the pressure is reduced. Degassing is performed in the micro-crack. Pressure is applied, and ultrasonic wave vibration is performed. Or a printed wiring board is heated, and thereafter the board is immersed into the solution of the fluorescence agent as another method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for inspecting a crack generated in a laminated board used for a printed wiring board or the like. In particular, it relates to a method for inspecting microcracks.

[0002]

2. Description of the Related Art A printed circuit board which is compatible with high-density mounting and high functionality is required to form a fine circuit and to process a small-diameter hole. If the conditions for drilling these small holes are poor, microcracks may occur around the holes.

When such a microcrack occurs,
There has been a problem that the reliability of electrical continuity of the printed wiring board is impaired.

Conventionally, the inside wall of the hole was cut along the hole to be observed and observed by a scanning electron microscope (SEM).
In addition, as a method for detecting cracks in electronic components, ultrasonic microscope observation is also performed.

[0005]

The SEM observation method is as follows:
Although the presence or absence of microcracks can be known, there is a drawback in that the extent of their spread cannot be known. Also, observation with an ultrasonic microscope has the advantage that the spread of cracks can be seen, but in terms of sensitivity, cracks in the printed wiring board, in particular,
It cannot be applied to the detection of microcracks in which the width of the crack opening (narrower in the vertical and horizontal directions of the opening) is 10 μm or less and the depth is 5 times or more the width.

Therefore, the present invention is to solve the above problems, and an object of the present invention is to provide a detection method capable of capturing microcracks with high sensitivity and observing the spread of microcracks as a surface. It is in.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and is characterized in that after the fluorescent agent penetrates into the cracks generated in the processed laminate, the fluorescent agent is absorbed. Is a method for inspecting a laminated plate by illuminating and observing.

As a method of infiltrating the fluorescent agent into the cracks, the laminated plate is dipped in a solution of the fluorescent agent,
Depressurize to degas the microcracks and allow them to penetrate.
Inject under pressure to permeate, ultrasonic permeate,
Alternatively, at least two or more of the methods in which the printed wiring board is heated and then immersed in the solution of the fluorescent agent are used in combination. By such a method, the fluorescent agent can be completely penetrated into the microcracks, and the microcracks containing the fluorescent agent can be exposed to ultraviolet rays, visible rays, X
Microcracks can be easily detected with high sensitivity by observing the fluorescence obtained by exciting a fluorescent agent with a ray, α ray, β ray, etc., and the microcracks can be observed in a planar spread.

Further, it is preferable to carry out a desmearing treatment for removing a deposit such as a resin around the opening, so that the reliability of the laminated plate after the inspection is improved. This is because the desmear treatment can secure an entrance for the fluorescent agent solution to penetrate into the microcracks.
For the desmear treatment, a commonly used plasma treatment or a method using permanganate can be used. As a result of these effects, drill workability is also excellent.

[0010]

The method for detecting microcracks according to the present invention utilizes pressure difference, temperature difference, and vibration to improve the penetrability, causes the fluorescent agent solution to penetrate into the microcracks, and then exposes it to light for luminescence. Is applied to obtain an excitation spectrum, and the strong luminescence is observed and measured with a fluorescence microscope or a fluorometer, so that it is possible to perform inspection with high sensitivity and a planar spread.

[0011]

EXAMPLES The present invention will be specifically described below with reference to examples.

Example 1 A glass-based epoxy resin-based four-layer board (manufactured by Matsushita Electric Industrial Co., Ltd. inner layer material R-1766, 0.9 mm thick, 70 mm copper foil and three prepregs R-1661, 0.1 mm). Used a drill bit of 0.4 mm in diameter with a part of the blade missing.
Drilling was performed at a feed rate of 1.6 m / min.

This laminated plate was soaked in a fluorescent penetrant flaw detector (trade name "Neo Glow" manufactured by Eishin Chemical Co., Ltd.) 1332
After reducing the pressure to Pa and holding for 10 minutes to remove the air inside the microcracks, the pressure was then increased to 10 kg / cm ² to allow neoglow to penetrate into the microcracks. After pressurizing for 10 minutes, the pressure was returned to normal pressure and the laminated plate was pulled up from the liquid of neoglow and washed with water to remove neoglow on the surface.

Next, ultraviolet rays were applied to this laminated plate and the fluorescence around the holes was observed with a fluorescence microscope. As a result, the part of the microcracks around the hole appeared to float in green.

Example 2 The same procedure as in Example 1 was carried out except that the defoaming treatment under reduced pressure was performed while ultrasonically vibrating the method of permeating neoglow in the section of Example 1 and the pressure was removed.

The results were the same as in Example 1, and the microcracks around the holes appeared to float up in green.

Example 3 Example 1 was repeated except that the method of infiltrating neoglow in the section of Example 1 was changed to depressurization and the laminated plate was heated to 80 ° C. and immersed in neoglow.

The results were the same as in Example 1, and the microcracks around the holes appeared to float in green.

Example 4 A permanganate desmear manufactured by Shipre Co., Ltd. was used by using a laminated plate punched by using a worn drill bit instead of a φ0.4 mm drill bit in which a part of the blade in Example 1 was chipped. After the treatment was carried out under standard conditions, the section of Example 1 was carried out as it was. As a result, as in the case of Example 1, the microcracks around the hole appeared to float up in green.

Example 5 The method of infiltrating neoglow is described in Example 4,
Except that the item of Example 1 is changed to a series of processes of degassing under reduced pressure while performing ultrasonic vibration which is the item of Example 2,
Same as Example 1.

The results were the same as in Example 1, and the microcracks around the holes appeared to float up in green.

Comparative Example 1 The depressurization and pressurization described in Example 1 were stopped, and the laminated plate was simply immersed in neoglow. As a result, no microcracks were observed around the holes.

Comparative Example 2 The same process as in Example 1 was carried out except that the pressure applied in Example 1 was stopped. As a result, fluorescence was observed around the holes, but only about 3/5 of that in Example 1, and the entire microcracks could not be observed.

Comparative Example 3 The procedure of Example 4 was repeated except that the desmear treatment described in Example 4 was omitted. As a result, fluorescence was observed around the holes, but only about 1/2 of that in Example 4, and the entire microcracks could not be observed.

Comparative Example 2 The laminated plate obtained in Example 1 was observed with an ultrasonic microscope, but no abnormality was found.

[0026]

According to the present invention, microcracks can be detected with high sensitivity and the spread of microcracks can be observed as a surface.

Claims (3)

[Claims] 1. A method for inspecting a laminated sheet, which comprises infiltrating a fluorescent agent into a crack generated in a processed laminated sheet, and then observing by making the fluorescent agent emit light. 2. The method of infiltrating a fluorescent agent into the crack according to claim 1, wherein the laminate is immersed in the fluorescent agent, and two or more of pressure reduction, pressure application, ultrasonic vibration or heating are combined. 2. The method for inspecting a laminated board according to claim 1, wherein 3. The method for inspecting a laminated plate according to claim 1, wherein the processed portion is desmeared before being penetrated by the fluorescent agent.