JP5043605B2 - Optical inspection system and optical inspection method - Google Patents

Description

The present invention relates to an optical inspection method, and more particularly to an automatic optical inspection method for a printed circuit board that can reduce overdetection of an inspection object (such as a flexible printed circuit board).

Printed circuit boards, one of the main materials used in the manufacture of various types of semiconductor devices such as driver integrated circuits and memories for liquid crystal display devices, are becoming increasingly smaller and lighter as semiconductor devices are becoming smaller and lighter. A flexible printed circuit board is often used. Among flexible printed circuit boards, for example, there are TAB (Tape Automatic Bonding), COF (Chip On Film) boards, and the like, and a fine circuit pattern is formed on the board by exposure, development, etching processes, and the like. Therefore, in the industrial body of flexible printed circuit boards, appearance inspection of product plating areas, solder resist areas, areas where semiconductor wafers are mounted (internal lead parts), etc., in the inspection before product ejection. Is the core inspection item.

That is, in a production body of a flexible printed circuit board for manufacturing semiconductor ICs, effective and quick inspection of the inspection items is the key to productivity and quality control.

Recently, in order to increase the productivity over existing products, printed circuit boards are produced using a substrate having a width of 300 mm or more, and therefore it is necessary to maintain flatness more than the existing printed circuit board having a width of 160 mm. There is. In particular, if the printed circuit board does not maintain flatness during the inspection process, the inspection using light cannot be performed normally. Therefore, in order to ensure the flatness of the printed circuit board, a flatness maintaining film made of stainless steel is attached to the bottom surface of the printed circuit board.

However, this type of printed circuit board is provided with an opaque flattening film on the bottom surface, which makes it impossible to inspect with transmitted light. Currently, not only short-circuits, protrusions, and depressions (side surfaces) but also depressions in the plane portion are detected at a time. However, if the level of the dent in the plane is weak, the level of the dent cannot be determined with the above structure, although it is normal. Therefore, the accuracy of the inspection is only about 30%, and there arises a problem that the operator must reinspect the defective portion with a color image or the like later.

The present invention has been made in view of the above-described problems, and an object thereof is to provide an automatic optical inspection method for a printed circuit board capable of preventing over-detection in a printed circuit board in which a transmitted light inspection is impossible. There is to do.

It is another object of the present invention to provide an automatic optical inspection method for a printed circuit board for inspecting a pattern shape on a printed circuit board in which transmitted light inspection is impossible.

In order to achieve the above object, an optical inspection method for a printed circuit board according to the present invention is an oblique direction with respect to a pattern formed on the printed circuit board with a film attached to the bottom surface of the printed circuit board. A first reflection image obtained by irradiating light on the substrate and a second reflection image obtained by irradiating light in a direction perpendicular to the pattern are used for the inspection of the pattern. If the dent is not detected in the first reflection image and the dent is detected to be equal to or smaller than a preset width with respect to the pattern width, the non-defective product is detected. you determined that the depression of sexual surface.

In this embodiment, an automatic optical inspection method of the printed circuit board, the printed circuit bottom surface of the substrate in a state in which off Irumu is attached, the light in an oblique direction with respect to the formed printed circuit board pattern And a second reflection image obtained by irradiating light in a direction perpendicular to the pattern, and the pattern is indented on the surface of the substrate. In the first reflection image, the dent is detected to be equal to or smaller than a preset width with respect to the width of the pattern, and the dent is detected with respect to the width of the pattern in the second reflection image. If it is detected to be greater than or equal to a preset width, it is determined that the surface has poor dentability .

In the present embodiment, the flatness maintaining film is made of an opaque material.

In the present embodiment, the inspection for the first reflection image is first performed, and then the inspection for the second reflection image is performed.

In the present embodiment, the printed circuit board is a flexible substrate in the form of a film or a tape, and the plurality of substrates are arranged in parallel and simultaneously inspected to maintain the flatness of the plurality of substrates. The inspection is performed in a state where a flatness maintaining film for maintaining flatness is attached to the bottom surface of the substrate.

In order to achieve the above object, in the automatic optical inspection method for a printed circuit board according to the present invention, the pattern inspection item of the printed circuit board includes a defect inspection of a pattern shape, and a recess is a pattern in the first reflection image. If the width is detected to be equal to or larger than a preset width, a pattern shape defect is detected.

In the present embodiment, an automatic optical inspection method for a printed circuit board , wherein the printed circuit board is inspected with a flatness maintaining film attached to a bottom surface in order to maintain flatness, The film for maintaining flatness is an opaque metal material, and a pattern component and a spatial component are obtained by using a first reflection image obtained by irradiating light on a pattern formed on the printed circuit board in an oblique direction. First, a pattern shape inspection is performed by distinction, and then a region of a pattern component obtained from the first reflection image is referred to using a second reflection image obtained by irradiating light in a direction perpendicular to the pattern. Inspect the center of the dent on the surface.

In the present embodiment, the first reflected image is obtained by irradiating light in a diagonal direction while moving in one direction of the printed circuit board, and the second reflected image is obtained by irradiating the printed circuit board with the one printed circuit board. It is obtained by irradiating light in the vertical direction while moving in the direction opposite to the direction.

In the present embodiment, the pattern inspection item of the printed circuit board includes a defect inspection of a depression on the surface, the depression is not detected in the first reflection image, and the depression is a pattern in the second reflection image. If the width is detected to be equal to or smaller than the width set in advance, it is detected as a depression on the surface with good quality.

According to the present invention, there is an extraordinary effect that it is possible to reduce overdetection in a printed circuit board in which transmitted light inspection is impossible. Further, according to the present invention, a pattern shape inspection on a printed circuit board in which a transmitted light inspection is impossible is a first reflection image obtained by irradiating light in the oblique direction, and a second obtained by irradiating light in the vertical direction. Using the reflected image, it is possible to improve the inspection quality to the same extent as when using reflected light by accurately discriminating good quality dents, deep defective dents, and pattern shape dents. .

The embodiments of the present invention can be modified in various forms, and the scope of the present invention should not be construed as being limited by the embodiments described in detail below. This embodiment is provided to explain the present invention in more detail to those who have ordinary knowledge in the technical field to which the present invention belongs. Accordingly, the shape of elements in the drawings may be exaggerated in order to emphasize a clearer description.

Embodiments of the present invention will be described in detail with reference to FIGS. For components having the same function in the drawings. Use the same reference numbers.

The inspection method of the present invention is extremely suitable for inspecting a flexible printed circuit board on which a fine pattern is formed by using a semi-additive process in which copper is grown by plating. In particular, the inspection method of the present invention is extremely suitable for inspecting a defective pattern shape on a flexible printed circuit board to which a flatness maintaining film made of a metal material is attached and inspection using transmitted light is impossible.

FIG. 1 is a diagram for explaining a configuration of an automatic optical inspection system according to an embodiment of the present invention, and FIG. 2 is a diagram showing an inspection unit provided with two cameras. FIG. 3 is a diagram illustrating an inspection object.

As shown in FIG. 1, an automatic optical inspection system 100 according to the present invention includes a line scan camera and two types of reflected light illumination on an inspection object 10 such as a film or tape type in which a flexible printed circuit board unit is continuously formed. This is an automatic inspection system using (oblique light (oblique light) and vertical light). The solid arrow symbol shown in the attached FIG. 1 indicates the movement path of the inspection object, and the dotted arrow symbol indicates signal transmission.

The optical automatic inspection system 100 is roughly composed of a feed roller (loader) 102, an inspection unit 110, and a winding roller (unloader) 106.

The inspection object is wound around the reel 104 in the unwinding section 102, and the inspection object 10 sent from the unwinding section 102 is supplied to the inspection section 110 through the guide roller 105. The inspection object is wound on the reel 108 of the inspection unit 110 and the winding unit 106. Of course, if necessary, a re-inspection unit and a marking unit for re-inspecting a defective portion with a color image or the like may be added between the inspection unit and the winding unit.

As shown in FIG. 3, an object 10 to be inspected according to the present invention is a wide-width (300 mm or more) type product in which a large number of printed circuit board units 12 are arranged in parallel. No. 10 performs an inspection in a state where an opaque flatness maintaining film 18 for maintaining flatness is attached to the bottom surface. Here, the opaque flatness maintaining film 18 is preferably a sus (stainless steel) material film in order to maintain the flatness of a wide inspection object. As described above, the inspection object to which the metal flatness maintaining film is attached cannot be inspected using transmitted light, and only inspected using reflected light. For this reason, the reliability of the pattern inspection of the inspection object to which the metal flatness maintaining film is attached must be remarkably lowered. However, as in the present invention, the inspection method using oblique light and vertical light prevents over-detection for a pattern defect of an inspection object to which a metal flatness maintaining film is attached, thereby improving inspection reliability. Can be increased. For example, the inspection object is a flexible printed circuit board on which a fine pattern is formed using a semi-additive method.

The inspection unit 110 includes a single camera 112, a diagonal illumination member 114 that irradiates the inspection object 10 with oblique light, a coaxial incident illumination member 116 that irradiates the inspection object with vertical light, and a camera 112, a coaxial incident illumination member 116, A moving member 120 for moving the oblique illumination member 114 is included. The camera 112 and the oblique / coaxial epi-illumination members 114 and 116 are moved back and forth by a distance set in advance in the length direction of the inspection object 10 (direction indicated by an arrow in the drawing) by the moving member 120. Here, the moving member 120 may use a cylinder method using hydraulic pressure or various methods using a motor, a ball screw, and a transfer nut.

In the present embodiment, one camera, the oblique illumination member, and the coaxial incident illumination member are shown to be composed of one module. However, as shown in FIG. 2, the two cameras 112 are coaxial with the oblique illumination member 114. The epi-illumination member 116 can also be installed and used, and in this case, the moving member can be omitted. As yet another example, a method is first used in which an inspection object is first imaged using a diagonal illumination member and then secondly imaged using a coaxial incident illumination member while the inspection object is wound in the opposite direction. You can also. Even when this method is used, the moving member can be omitted. For example, a line scan camera can be used as the camera 112, and a camera and an illumination member can be further installed in the inspection unit 110 later depending on the inspection conditions of the inspection object and user requirements. The inspection unit 110 includes a processing unit 130 to which an image captured from the camera 112 is provided. The processing unit 130 is provided in a typical computer system (also referred to as a microcomputer), and controls and processes various operations according to automatic optical inspection. Then, the processing unit 130 receives the first reflection image and the second reflection image from the camera 112 and integrates the primary reflection inspection and the secondary reflection inspection to detect a pattern defect.

As shown in FIG. 1, when the camera 112 moves forward by a distance set in advance by the moving unit 120, light is emitted from the oblique illumination member 114 in the oblique direction. When the camera 112 moves backward by the distance moved forward by the moving unit 120, light is irradiated from the coaxial incident illumination member 114 in the vertical direction. As described above, in the present invention, the first reflection image obtained by irradiating light in the oblique direction by the movement of one camera 112 back and forth and the second reflection image obtained by irradiating light in the vertical direction are obtained. Since it can be obtained sequentially, not only the inspection time can be shortened, but also the space utilization of equipment can be improved.

In particular, the pattern inspection in the present invention uses a first reflection image obtained by first irradiating light in the oblique direction, first distinguishing the pattern component from the spatial component, and then performing a pattern shape inspection (single line, combined line, protrusion) , Dent) is first performed (primary reflection inspection). Then, by using the second reflection image obtained by irradiating light in the secondary vertical direction, the surface depression is focused on by referring to the pattern component region obtained from the first reflection image (2 Second reflection inspection). Of course, a portion that is not detected from the first reflection image in the spatial component may be visible from the second reflection image. However, in the secondary reflection inspection, the surface depressions are mainly inspected mainly. That is, as shown in FIGS. 4 to 6 below, in order to improve the inspection reliability of the surface depression, a secondary reflection image obtained by always irradiating light in the vertical direction is necessary.

More specifically, the light irradiated in the oblique direction from the oblique illumination member 114 makes the defect of the surface depression appear to be smaller than the actual light than the vertical light (the reason is that scattering occurs in the surface depression. This is because the portion looks bright), and a shallow surface dent (a surface dent that is not deep) has almost no outline, but if the pattern shape is poor (the defect shown in FIG. 6), the outline is clear. Appears in On the contrary, the light irradiated in the vertical direction from the coaxial epi-illumination member 116 has a contour (a dent) in the same way as an actual defect even in a dent on the surface with good quality (thickness of the dent on the surface is shallow). Therefore, when using images obtained from two types of lighting with such characteristics, it is possible to clearly determine whether the surface depression is good, defective, or pattern shape depression. It is. For example, in the present invention, the order in which light in the oblique direction and light in the vertical direction are irradiated can be changed.

4-6 is a figure which shows the 1st reflective image and 2nd reflective image according to the type of a hollow. Here, in the first and second reflection images, a white portion indicates a pattern component, and a dark portion indicates a spatial component.

As shown in FIG. 4, (a) shows a pattern cross section with a depression on the upper surface, and (a-1) and (a-2) show a pattern cross section (a) with a non-defective depression on the upper surface. A first reflection image and a second reflection image obtained by irradiating light from the oblique line direction and the vertical direction are respectively shown.

First, in the first reflection image (a-2), a depression corresponding to the width of the depression appears, but in the first reflection image (a-1), even if there is a small depression on the upper surface, no depression appears. This is because, as described above, the light in the oblique line direction is scattered from the inside of the depressed portion to the camera, and the light is transmitted to the camera for the small depression belonging to the non-defective product at the edge of the plane portion. This is because it is recognized as a bright part and the dent cannot be seen well. Therefore, it is measured as a normal line width. Thus, in the case of (a), the non-detection is detected from the first reflection image, and the depression detected from the second reflection image is ½ or less with respect to the reference pattern width.

For example, when no depression is detected from the first reflection image and the depression detected from the second reflection image is ½ or more of the reference pattern width, no depression is detected from the first reflection image. Means that the depth is not deep. Therefore, if the depth is not deep even though the depression is wide, it can be detected as a non-defective product.

As shown in FIG. 5, (b) shows a pattern cross section with a deep dent on the surface, and (b-1) and (b-2) show light from the pattern cross section (b) from the oblique direction and the vertical direction. A first reflection image and a second reflection image obtained by irradiation are shown.

First, in the first reflection image (b-1), a dent appears, which can be determined to mean that the depth of the dent formed in the pattern is deep or that the pattern shape is poor. Therefore, as a precaution, the second reflection image must be confirmed. In the secondary reflection image, the width of the dent appeared to be 1/2 or more with respect to the pattern width. As a result, in the case of (b), since the depth of the depression is deep, it is detected that the surface has a depression characteristic.

As shown in FIG. 6, (c) shows a pattern cross section in which one side of the pattern is completely dropped, and (c-1) and (c-2) show the pattern cross section (c) in a direction perpendicular to the oblique line direction. A first reflection image and a second reflection image obtained by irradiating with light are respectively shown. First, in the first reflection image (c-1), a dent appears for the width in which the pattern disappears, and in the second reflection image (c-2), a dent appears almost in the same manner as the first reflection image. In this case, 1/3 or more of the reference pattern width is detected in the first reflection inspection, and almost the same recess appears in the second reflection inspection, so that it can be determined that the pattern shape is poor.

Explaining the inspection standard, the pattern shape defect detects 1/3 or more of the reference pattern width, and the surface dent defect detects 1/2 or more of the reference width. That is, in the present invention, when there is an image defect in the secondary reflection inspection in a portion where the pattern shape defect is not detected in the primary reflection inspection, only a difference of 1/2 or more with respect to the existing line width is detected. Since it is good, overdetection can be greatly reduced.

As described above, when inspecting a pattern formed on a printed circuit board without using reflected light, the inspection unit of the present invention has a first reflection image obtained by irradiating light in the oblique direction, Using the second reflection image obtained by irradiating light in the vertical direction, it accurately discriminates good quality depressions, deep defective depressions, and pattern shape depressions, and has the same inspection quality as using reflected light. There is a special effect that it can be increased.

The above-described preferred embodiments of the present invention are disclosed for the purpose of illustration, and those having ordinary knowledge in the technical field to which the present invention belongs do not depart from the technical idea of the present invention. Various substitutions, modifications, and alterations are possible within the scope, and such substitutions, alterations, and the like belong to the scope of the claims.

It is a figure for demonstrating the structure of the automatic optical inspection system by embodiment of this invention. It is a figure which shows the test | inspection part provided with two cameras. It is a figure which shows a test target object. It is a figure which shows the 1st reflective image and 2nd reflective image according to the type of a hollow. It is a figure which shows the 1st reflective image and 2nd reflective image according to the type of a hollow. It is a figure which shows the 1st reflective image and 2nd reflective image according to the type of a hollow.

Explanation of symbols

102 Unwinding unit 106 Winding unit 110 Inspection unit 112 Camera 114 Oblique illumination member 116 Coaxial epi-illumination member

Claims (10)

In an optical inspection method for a printed circuit board,
A first reflection image obtained by irradiating light obliquely with respect to a pattern formed on the printed circuit board in a state where a film is attached to the bottom surface of the printed circuit board;
Using a second reflection image obtained by irradiating light in a direction perpendicular to the pattern ,
The inspection of the pattern includes a defect inspection of a depression on the surface of the substrate,
The depression is not detected in the first reflection image, and
An optical inspection method for a printed circuit board , wherein if the dent is detected to be equal to or less than a preset width with respect to a pattern width in the second reflection image, it is determined as a dent on a non-defective surface . In an optical inspection method for a printed circuit board,
A first reflection image obtained by irradiating light obliquely with respect to a pattern formed on the printed circuit board in a state where a film is attached to the bottom surface of the printed circuit board;
Using a second reflection image obtained by irradiating light in a direction perpendicular to the pattern,
The inspection of the pattern includes a defect inspection of a depression on the surface of the substrate,
In the first reflection image, the depression is detected to be equal to or smaller than a preset width with respect to the width of the pattern;
An optical inspection method for a printed circuit board , wherein if the dent is detected to be greater than or equal to a predetermined width with respect to the width of the pattern in the second reflection image, it is determined that the dent of the surface is poor . The film printed circuit optical inspection method for a substrate according to claim 1 or 2, characterized in that the flat keep film for maintaining the flatness. The method for optical inspection of a printed circuit board according to claim 3, wherein the flatness maintaining film is made of an opaque material. 5. The optical inspection method for a printed circuit board according to claim 1, wherein after the inspection of the first reflection image, the inspection of the second reflection image is performed. 6. The printed circuit board is a flexible substrate in the form of a film or tape, and a plurality of the substrates are arranged in parallel and simultaneously inspected,
The inspection is performed in a state where a flatness maintaining film for maintaining flatness is attached to a bottom surface of the substrate in order to maintain flatness of the plurality of substrates. Item 5. The printed circuit board optical inspection method according to any one of Items 4 above. The pattern inspection items of the printed circuit board include a defect inspection of the pattern shape,
5. The method according to claim 1, wherein if the depression is detected in the first reflection image to be equal to or greater than a preset width with respect to the pattern width, it is determined that the pattern shape is defective. An optical inspection method for the printed circuit board as described. In an optical inspection method for a printed circuit board,
In order to maintain the flatness, the printed circuit board is inspected with a flatness maintaining film attached to the bottom surface, and the flatness maintaining film is an opaque metal material,
For the pattern formed on the printed circuit board, using the first reflection image obtained by irradiating light in an oblique direction, after performing pattern shape inspection by distinguishing the pattern component and the spatial component,
Using a second reflection image obtained by irradiating light in a direction perpendicular to the pattern, a surface depression is inspected with reference to a pattern component region obtained from the first reflection image. Optical inspection method for printed circuit boards. The first reflection image is obtained by irradiating light in an oblique direction while moving the printed circuit board in one direction, and the second reflection image is obtained by irradiating the printed circuit board in a direction opposite to the one direction. 9. The optical inspection method for a printed circuit board according to claim 8 , wherein the optical inspection method is obtained by irradiating light in a vertical direction while moving to. The printed circuit board pattern inspection items include surface defect inspections,
The depression is not detected in the first reflection image;
9. The printed circuit board optical according to claim 8 , wherein if the dent is detected to be equal to or less than a preset width with respect to the pattern width in the second reflection image, it is determined as a dent on a non-defective surface. Inspection method.

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