JP2003004662A - Pattern inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pattern inspection method in which an object can be inspected satisfactorily even when the object is a chemically polished product. SOLUTION: Before a pattern is inspected, a printed-wiring board 1 is soft- etched. Its soft etching operation has an action which removes and smoothes fine irregularities on the surface of a pattern part 2 on the board 1. As a result, by its soft etching operation, diffuse reflection is reduced when the pattern 2 is irradiated with light, and the luminance of the pattern 2 is increased. Consequently, the difference between the optical reflectance of the pattern 2 after its soft etching operation and the optical reflectance of a substrate 3 not influenced by the soft etching operation becomes large, and a remarkable contrast can be obtained. After that, the board 1 is irradiated with light, and the pattern is inspected on the basis of a difference in a reflection state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern inspection method for inspecting a pattern on the surface of an object. More specifically, the present invention relates to a pattern inspection method capable of obtaining a remarkable contrast between a pattern portion and other portions regardless of the polished state of the object.

[0002]

2. Description of the Related Art Conventionally, for a wiring board or the like having a pattern on its surface, a quality inspection of the pattern has been performed. This pattern inspection is generally performed by irradiating an object with light and distinguishing between the location of the pattern and the other location according to the reflection state of the light. In the wiring board, which is the main object of the pattern inspection, the pattern part is copper and the other base part is resin. For this reason, since the light reflectance differs between the pattern portion and the other portions, the two can be distinguished.

[0003]

However, the above-mentioned conventional pattern inspection method has the following problems. In other words, the wiring board that has been frequently used in the past was a pattern obtained by finishing the pattern by jet scrubbing. Therefore, the light reflectance of the pattern portion was high (looks to the surface of a new coin with the naked eye), and the difference from the light reflectance of the base was large. However, in recent years, chemical polishing has been used instead of jet scrubbing. In the case of a chemical-polished product, the light reflectance of the pattern is not so high (it looks like the surface of a used coin with the naked eye), so the difference from the light reflectance of the base is small. For this reason, it was not possible to distinguish between the pattern part and the other parts, not only by visual observation.

The present invention has been made to solve the problems of the conventional pattern inspection method described above. That is, the problem is to provide a pattern inspection method capable of excellent inspection even when the object is a chemically polished product.

[0005]

In the pattern inspection method of the present invention, which has been made for the purpose of solving this problem, first, an object to be inspected is soft-etched. Next, the surface of the object after the soft etching is irradiated with light. Then, the quality of the pattern is inspected based on the difference in the reflection state of the light at the pattern portion and the other portion.

In this inspection method, the object is soft-etched before the object is irradiated with light. This soft etching has a function of removing fine unevenness on the surface of the pattern portion of the object and smoothing it. Therefore, due to the soft etching, diffused reflection when light is irradiated to the pattern area is reduced, and the brightness at the pattern area is increased. As a result, the difference between the light reflectance of the pattern portion and the light reflectance of other portions that are not affected by the soft etching becomes large, and a remarkable contrast can be obtained. Therefore, it is possible to discriminate between the pattern portion and other portions depending on the difference in the light reflection state, and it is possible to inspect the pattern.

The present invention is particularly significant when the surface pattern of the object to be inspected is a chemically polished copper pattern. Furthermore, soft etching is performed with an acidic etching solution containing hydrogen peroxide, and the etching amount is 0.2 to 1.0 μm.
It is good to set it within the range of m. Within this range, a sufficient contrast can be obtained between the pattern portion and other portions, and a good pattern inspection can be performed.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments embodying the present invention will be described in detail below with reference to the accompanying drawings.
The present embodiment is one in which the present invention is embodied as a pattern inspection method when an inspection target is a chemically polished printed wiring board.

The object of inspection in this embodiment is a printed wiring board as shown in FIG. The surface of the printed wiring board 1 includes a pattern portion 2 that is a conductor pattern and a base portion 3 that is a portion where the insulating resin is exposed. The pattern portion 2 is made of copper and has been subjected to finishing treatment by chemical polishing.

Next, the pattern inspection procedure of the printed wiring board 1 will be described. First, the printed wiring board 1 is soft-etched. The soft etching here means that the pattern surface is a metal surface with high light reflectance,
It is a process of slightly dissolving copper. The etching solution is an acidic aqueous solution containing hydrogen peroxide. For example, the concentration of hydrogen peroxide is about 10 g / L and the concentration of sulfuric acid is 45 g / L.
The thing with about L is used. In the present embodiment, this makes the surface of the pattern portion 2 smooth and obtains a metal surface having a high light reflectance.

FIG. 2 is an SEM photograph (magnification at the time of photographing: 200) of the surface of the pattern portion 2 before the soft etching treatment.
00 times). On the surface before the treatment, irregularities due to the chemical polishing treatment that is already performed as a finish are conspicuous. Therefore, when the surface of the pattern portion 2 is irradiated with light, the diffuse reflection component of light is large and high brightness cannot be obtained.
On the other hand, FIG. 3 shows the pattern portion 2 after the soft etching process.
2 is an SEM photograph (20,000 times the same) of the surface of the. On the surface after the treatment, the irregularities due to the chemical polishing treatment are inconspicuous. Therefore, when the surface of the pattern portion 2 is irradiated with light, diffuse reflection of light is small and high brightness can be obtained.

Next, as a pattern inspection, an optical appearance inspection is carried out. In this optical appearance inspection, the printed wiring board 1 is irradiated with light and the quality of the pattern portion 2 is inspected based on the difference in the reflection state of the light. In this embodiment, a halogen lamp is used as the main light source.

Here, an example of a case of inspecting a part of the pattern of the printed wiring board 1 as shown in FIG. 4 will be described. First, FIG. 4A shows the luminance distribution on the line marked A in FIG. 4 for the inspection body after the soft etching treatment. Figure 4
(A) High brightness is shown on the middle pattern portion 2. On the other hand, the base portion 3 shows low luminance. In this way, there is a sufficient difference between the high-luminance portion and the low-luminance portion, and the pattern inspection can be performed by setting an appropriate threshold value. On the other hand, FIG. 4B shows the luminance distribution of the inspection body before the soft etching treatment. In FIG. 4B, there is only a slight difference in brightness. In addition, the brightness of each individual inspection object varies depending on various conditions such as finishing, so that an appropriate threshold value cannot be set. Therefore, the pattern inspection cannot be performed.

Next, with respect to the soft etching in the present embodiment, whether or not the inspection for each etching amount and the test result of measuring the voltage required for the halogen lamp will be briefly described. The voltage measured here is the voltage necessary for performing a good visual inspection. The etching amount is controlled by time. FIG. 5 is a table showing the experimental results of the soft etching amount. In the table, the first column shows the etching amount, the second column shows the voltage of the halogen lamp, and the third column shows whether or not the optical appearance inspection is possible. First, when soft etching was not performed (soft etching amount 0.00 μm), even if the halogen lamp voltage was increased to 15.0 V, it was not possible to obtain a contrast that could inspect the pattern portion. Therefore, the third column is "No". Next, when the soft etching amount was 0.28 μm, it was possible to obtain the contrast that could inspect the pattern portion when the halogen lamp voltage was 13.1V. Similarly, the etching amount is 0.42, 0.61, 0.71, 1.03 μm
, The halogen lamp voltage is 12.
When the voltage was set to 2, 12.2, 11.3, and 10.7 V, the contrast for inspecting the pattern portion could be obtained.
Therefore, the third column is “OK”.

Based on the result of FIG. 5, FIG. 6 shows a graph of the relationship between the soft etching amount and the light source voltage. From the measurement data, it can be seen that the smaller the soft etching amount, the higher the required voltage. For example, it can be seen that an etching amount of 0.2 μm or more is necessary to inspect at a voltage of 13.5V.

As described in detail above, in the inspection method of this embodiment, the printed wiring board 1 to be inspected is soft-etched. The pattern portion 2 of the printed wiring board 1 is a copper pattern, and its surface is smoothed by soft etching. Next, the soft-etched printed circuit board 1 is irradiated with light. Since the pattern portion 2 has a smoothed metal surface, it can reflect light. That is, the soft etching ensures the contrast between the pattern portion 2 and the base portion 3 necessary for the inspection. Therefore, the pattern portion 2 and the base portion 3 can be discriminated by the difference in the light reflection state, and the quality of the pattern portion 2 can be inspected.

As the etching solution for soft etching, an acidic aqueous solution containing hydrogen peroxide is used. The etching amount was 0.2-1.
It can be seen that it is within the range of 0 μm. As a result, a pattern inspection method capable of performing a good inspection even when the inspection target is the printed wiring board 1 which is a chemically polished product is realized.

The present embodiment is merely an example and does not limit the present invention. Therefore, naturally, the present invention can be variously improved and modified without departing from the gist thereof.

[0019]

As is apparent from the above description, according to the present invention, there is provided a pattern inspection method capable of performing a good inspection even when the object is a chemically polished product.

[Brief description of drawings]

FIG. 1 is a printed wiring board used in the embodiment.

FIG. 2 is an SEM photograph of the copper pattern surface before soft etching.

FIG. 3 is an SEM photograph of a copper pattern surface after soft etching.

FIG. 4 is a luminance distribution of a printed wiring board before and after soft etching treatment.

FIG. 5 is a table showing experimental results of soft etching amount.

FIG. 6 is a graph showing the relationship between the amount of soft etching and the light source voltage.

[Explanation of symbols]

1 printed wiring board 2 pattern parts 3 Base part

Claims (2)

[Claims] 1. A method for inspecting a pattern on the surface of an object, wherein the object is soft-etched, the surface of the object after soft-etching is irradiated with light, and the light is applied at a pattern location and other locations. A pattern inspection method comprising inspecting the quality of a pattern based on the difference in the light reflection state. 2. The pattern inspection method according to claim 1, wherein the surface pattern of the object is a chemically polished copper pattern, and soft etching is performed with an acidic etching solution containing hydrogen peroxide. The amount is 0.2
A pattern inspection method characterized in that the thickness is within a range of 1.0 μm.