JPS6150003A - Pattern detecting method - Google Patents

Abstract

PURPOSE:To detect the wiring pattern on substrates accurately, by reproducing the image of a linear non-directional light source by a hologram, and performing linear lighting. CONSTITUTION:When laser light 12 is inputted to a hologram 11, a linear images 4 is formed on substrates 5 and 6. Since the image 4 is the reproduced image of the non-directional light source through the hologram, light is converged in corresponding with the non-directional property of the hologram forming light source, i.e., in irregular directions, and the linear image is formed. Therefore, light rays in various directions are mixed in the light 13, which is applied on the copper foil pattern 6. As a result, the light 13, which is applied at any part of the end part of the copper foil pattern 6, sufficiently reaches a CCD8 through a lens 7. Even if the surface of the pattern is not flat, the pattern including its width can be accurately detected by this method.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a nosetan detection method, for example, a method for accurately detecting a wiring pattern on a printed circuit board.

In the semiconductor device industry, wiring patterns on printed boards are becoming finer and the board area is increasing. For this reason, it has become difficult to visually inspect printed boards, and an effective automatic inspection method is desired.

2. Description of the Related Art Conventionally, as a method of detecting a pattern on a plane, a method of linearly irradiating laser light and detecting by line COD is known. To explain with reference to FIG. 4, the light emitted from the laser 1 passes through the optical beam expander 2 and enters the cylindrical lens 3. Irradiate to 5. An image of the wiring pattern 6 on the printed board 5 is formed by the lens 7 and detected by the CCD 8. The printed board 5 is moved and the laser beam 4 runs on the printed board 5, causing - on the printed board 5.
Detects P-turn.

In the above method, the laser beam 1r is focused in a linear manner for illumination because the plastic printed board substrate has the property of internally diffusing light. Internally diffused light mixes with the reflected light from the board, lowering the detection contrast ratio and making accurate detection of wiring patterns difficult. 58'-194808).

Problems to be Solved by the Invention Wiring patterns on printed boards are typically formed by etching copper foil on the surface of a printed board base material such as epoxy into a desired wiring butter, but during etching, etc. [° drooping] occurs at the edge (shoulder) of the pattern. However, since laser light is originally parallel light, the light that passes through the cylindrical lens 3 and is focused has variations in the traveling direction of the light within an angular range that is in conflict with the focusing angle. However, the light in the direction perpendicular to the plane including the condensing angle reaches the printed board base material 5 and pattern 6 as parallel light. Therefore, as seen in FIG. 5(b), even if the parallel component of the Rede light that forms on the linear image 4 hits the copper foil pattern (light 9), the edge of the pattern is not flat. If it is reflected from the sagging part, it is not necessarily the detection CCD.
It doesn't reach 8. For this reason, as shown in FIG. 5(b), the pattern edge 10 is
The strength of the trundle is reduced, as a result of which it is impossible to accurately detect the width of the tsuktan.

Means and operation for solving the problems In order to solve the above-mentioned problems, the present invention creates a hologram of a linear omnidirectional light source and uses the hologram to create an image of the linear omnidirectional light source. Reproduce. Here, the term "omnidirectional light source" refers to the fact that the light emitted from the light source does not have a fixed directionality in the direction of travel, but is oriented randomly in all directions. When reproducing a hologram formed by forming the light from such a light source as an object wave, the regenerated light has the property of reproducing the image of the light source by traveling exactly in the opposite direction to the object wave at the time the hologram was formed, so it can be used in any random direction. Light gathers from the hologram and reproduces the image of the light source (light that is not recorded in the hologram cannot be reproduced, so there is a certain range or limit to the direction of the reproduced light).

Therefore, if such a hologram is used, it is possible to illuminate the printed board in a linear manner with light from multiple directions, so it is possible to prevent a decrease in the received light intensity due to sagging of the pattern when detecting the wiring pattern. The pattern can be accurately detected up to its width.

Embodiments Embodiments of the present invention will be described with reference to FIGS. 1 to 3. FIG. 10) is a detailed explanation of the present invention for inspecting patterns on a printed board, and the same parts as in FIG. 4(a) are indicated by the same numerals.

That is, 4 is a linear focused image, 5 is a printed board base material, and 6 is a linear focused image.
is a copper foil pattern, 7 is a lens, and 8 iL ccD. However, in the embodiment, a hologram 11 is used in place of the cylindrical lens. The details of how to create this hologram 11 will be described later, but it is a hologram of a linear omnidirectional light source. When laser light (parallel light) 12 is incident on this hologram 11, a linear image 4 is formed on printed boards 5 and 6. Since this image 4 is a hologram reconstructed image of a non-directional light source, as mentioned above, light is condensed from non-directional, that is, random directions into a line, corresponding to the non-directionality of the hologram-forming light source. It forms an image of the shape. Therefore, the copper foil pattern 6
The light 13 that hits the cylindrical lens is not parallel light as in the case of light passing through a cylindrical lens, but is a mixture of light from various directions. The emitted light 13 is also transmitted to the CCD 8 via the lens 7.
(Light 14).

In this way, according to the method of the present invention, even if the surface condition of the pattern is not necessarily flat, as long as the light reflection efficiency of the pattern and the background is different, it is possible to accurately detect the pattern including its width. (See Figure 1 ←)).

Next, a method for creating the above hologram will be explained with reference to FIGS. 2 and 3. For example, a high-resolution photographic plate (silver salt) is used as the hologram recording film 20. As a linear omnidirectional light source, use blank paper or a material 2 with a diffusely reflective surface such as ground glass.
1 is cut into a predetermined linear shape (for example, 100 μm wide, 20 groups long), placed on a black background 22, and exposed to Rede light (He-N
It is possible to irradiate the e-laser beam 23 and use its reflected light 24. This reflected light 24 is naturally diffusely reflected light from the linear material 21, that is, non-directional light. This linear light source 2
The light from 1 is an object wave 24, and parallel light (He-Ne Radhe light) having a certain angle with respect to the hologram recording film 20
A hologram 30 is created using the reference wave 25 as the reference wave 25. When the same light 31 as the reference wave 25 at the time of recording is incident on this hologram 30 from the direction exactly opposite to the reference wave, the light 32 passes through a course exactly opposite to the object wave 24 at the time of recording and forms a linear image. form 33. The light 32 is not parallel even in the direction perpendicular to the plane including the condensing angle, but is omnidirectional, that is, disordered, and multidirectional.

Effects of the Invention As is clear from the above description, the present invention provides a method for accurately detecting a pattern including its width even when the surface condition of the pattern is not flat or uniform. Although this method is particularly effective for inspecting wiring patterns on printed circuit boards, the detected/set turns are not necessarily linear.

[Brief explanation of the drawing]

FIG. 1 is a perspective view illustrating a turn detection method according to an embodiment of the present invention, FIG. 2 is a perspective view illustrating hologram recording, FIG. 3 is a perspective view illustrating hologram image reproduction, and FIG.
1 and 5 are perspective views illustrating a conventional pattern detection method. 1... Laser, 3... Cylindrical lens, 4...
... Image, 5... Printed board base material, 6... Wiring pattern, 7... Lens, 8... ecD, 11... Hologram, 20... Hologram recording film, 21... Slit for light source, 30... Hologram, 33... Image.

Claims (1)

[Claims] 1. In a method of scanning linear illumination on a plane and receiving the reflected light to detect a pattern on the plane, a hologram of a linear omnidirectional light source is created, and the hologram is used to detect the linear non-directional light source. A pattern detection method characterized in that the linear illumination is performed by reproducing an image of a directional light source.