KR100834113B1 - Method for automated optical inspection - Google Patents

Abstract

The present invention relates to an automatic optical inspection method of a printed circuit board which can reduce overdetection of an inspection object (flexible printed circuit board). The automatic optical inspection method of a printed circuit board of the present invention has a first reflection image obtained by irradiating light in an oblique direction in a first direction when inspecting a pattern formed on the printed circuit board, and pattern pattern inspection by first distinguishing a pattern component and a spatial component. Is performed first, and the surface reflection is examined based on the region of the pattern component obtained in the first reflection image by using the second reflection image obtained by irradiating light in the second direction.

Printed Circuit Board, Diagonal Light, Vertical Light

Description

Automatic Optical Inspection System {METHOD FOR AUTOMATED OPTICAL INSPECTION}

1 is a view for explaining the configuration of an automatic optical inspection system according to an embodiment of the present invention.

2 is a view showing an inspection unit provided with two cameras.

3 is a view showing an inspection object.

4 to 6 are diagrams showing a first reflection image and a second reflection image according to each type of depression.

Explanation of symbols on the main parts of the drawings

102: unwinding unit

106: Gunguin

110: inspection unit

112: camera

114: diagonal lighting member

116: coaxial fall lighting member

The present invention relates to an automatic optical inspection method, and more particularly to an automatic optical inspection method of a printed circuit board that can reduce the over-detection of the inspection object (flexible printed circuit board).

Printed circuit boards, which are one of the main materials used in the manufacture of various semiconductor devices such as driver integrated circuits and memories of liquid crystal displays, are flexible such as film and tape types according to the trend of miniaturization and light weight of semiconductor devices. Flexible printed circuit boards are used a lot. Among flexible printed circuit boards, for example, a tape automatic bonding (TAB), a chip on film (COF) substrate, and the like are formed, and a fine circuit pattern is formed on the substrate through an exposure, development, and etching process. Therefore, as a key inspection item, manufacturers of flexible printed circuit boards should inspect the appearance of the product such as plating area, solder resist area, and semiconductor wafer area (inner lead part) before product shipment inspection. It is being divided.

That is, in the production of flexible printed circuit boards for semiconductor IC manufacturing, effective and rapid inspection of the inspection items becomes a key to productivity and quality control.

Recently, since printed circuit boards are manufactured using a substrate having a width of 300 mm or more in order to increase productivity than existing products, it is necessary to maintain flatness more than the existing 160 mm wide printed circuit boards. In particular, when the printed circuit board does not maintain the flatness during the inspection process, the inspection using light is not normally performed. Therefore, in order to provide flatness to the bottom surface of the printed circuit board, a film for maintaining flatness of stainless steel is attached.

However, this type of printed circuit board cannot be inspected using transmitted light because an opaque flat-keeping film is provided on the bottom surface, and at present, it is mostly short-circuit, short-circuit, projection, and recession by using light incident vertically. Not only the (side) but also the dent of the planar portion is detected. However, despite the fact that the planar depression is normal when the degree is weak, it is impossible to determine the degree of depression in the above structure, and all of them are detected as defective. Therefore, the accuracy of the inspection is only about 30%, and a problem arises that the operator later re-inspects the defective part with a color image.

The present invention provides an automatic optical inspection method of a printed circuit board capable of preventing overdetection in a printed circuit board in which transmission light inspection is impossible.

The present invention provides an automatic optical inspection method of a printed circuit board for inspecting a pattern shape in a printed circuit board in which transmitted light inspection is impossible.

Automatic optical inspection method of a printed circuit board of the present invention for achieving the above object is a first reflection image obtained by irradiating light in a diagonal direction when inspecting a pattern formed on the printed circuit board, and by irradiating light in a vertical direction Examine using the obtained second reflection image.

In the present embodiment, the automatic optical inspection method of the printed circuit board is inspected in the state that the film for maintaining the flatness is attached to the bottom surface of the printed circuit board.

In this embodiment, the flat film is made of an opaque material.

In the present embodiment, the first reflective image is inspected first, and the second reflective image is subsequently examined.

In the present embodiment, the printed circuit board is a flexible substrate in the form of a film or tape, the plurality of substrates are arranged in parallel to be inspected at the same time, the plurality of substrates arranged in parallel to maintain the flatness The bottom surface of the substrates are inspected with the flattening film attached to maintain the flatness.

In the present exemplary embodiment, the pattern inspection item of the printed circuit board includes a surface patchability defect, and no recesses appear in the first reflection image, and the recesses are less than or equal to a pattern width in the second reflection image. If present, a good surface patch is detected.

In the present exemplary embodiment, the pattern inspection item of the printed circuit board includes a surface patchability defect, and the depressions in the first reflection image appear below a predetermined width relative to the pattern width, and the depressions in the second reflection image are patterns If the width exceeds the preset width, it is detected as a poor surface coarseness.

In the present exemplary embodiment, the pattern inspection item of the printed circuit board includes a pattern shape defect, and when the depression is greater than or equal to a predetermined width in the first reflection image, the pattern inspection item is detected as a pattern shape defect.

Automatic optical inspection method of a printed circuit board of the present invention for achieving the above object has a pattern component and a spatial component having a first reflection image obtained by irradiating light in an oblique direction in the first direction when inspecting a pattern formed on the printed circuit board First, the pattern shape inspection is performed by first distinguishing and then the surface reflection is examined by referring to the region of the pattern component obtained in the first reflection image by using the second reflection image obtained by irradiating light in the second vertical direction. .

In the present embodiment, the printed circuit board is inspected while the flat film is attached to the bottom surface to maintain flatness; the flat film is an opaque metal material.

In the present exemplary embodiment, the first reflection image is obtained by irradiating light in an oblique direction while moving in one direction of the printed circuit board, and the second reflection image is moved in a vertical direction while moving in a reverse direction of the printed circuit board. Investigate and get

In the present exemplary embodiment, the pattern inspection item of the printed circuit board includes a surface patchability defect, and no recesses appear in the first reflection image, and the recesses are less than or equal to a pattern width in the second reflection image. If present, a good surface patch is detected.

For example, embodiments of the present invention may be modified in various forms, and the scope of the present invention should not be construed as being limited by the embodiments described below. This embodiment is provided to more completely explain the present invention to those skilled in the art. Accordingly, the shape of the elements in the drawings and the like are exaggerated to emphasize a more clear description.

An embodiment of the present invention will be described in detail with reference to FIGS. 1 to 6. In addition, in the drawings, the same reference numerals are denoted together for components that perform the same function.

The inspection method of the present invention is very suitable for inspecting a flexible printed circuit board on which a fine pattern is formed by using a semi additive process of forming a pattern component by plating. In particular, the inspection method of the present invention is very suitable for inspecting a pattern shape defect in a flexible printed circuit board which is attached to a flat film of a metal material and cannot be inspected using transmitted light.

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

Referring to FIG. 1, the automatic optical inspection system 100 according to an embodiment of the present invention includes a line scan camera and two kinds of inspection objects 10, such as a film and a tape type, in which flexible printed circuit board units are continuously formed. Automatic inspection system using reflected light illumination (diagonal light and vertical light). In the accompanying drawings, the solid arrow symbol shown in FIG. 1 indicates a moving path of the inspection object, and the dotted arrow symbol indicates signal transmission.

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

An inspection object is wound on the reel 104 in the unwinding part 102, and the inspected object 10 sent out from the unwinding part 102 is supplied to the inspecting part 110 through the guide rollers 105. The inspection object is wound around the reel 108 of the winding unit 106 of the inspection unit 110. Of course, if necessary, a re-inspection unit and a marking unit may be added between the inspecting unit and the gusset unit to re-inspect the defective part by the color image.

As shown in FIG. 3, the object 10 to be inspected in the present invention is a product of a wide width (300 mm or more) type in which a plurality of printed circuit board units 12 are arranged in parallel. The inspection is performed while the opaque flattening film 18 is attached to the bottom surface to maintain flatness. Here, the opaque flattening film 18 preferably uses a film of sus (stainless steel) material in order to maintain flatness of a wide inspection object. As such, the inspection object to which the flat film of metal material is attached cannot be inspected using the transmitted light and only inspected using the reflected light. For this reason, the reliability of the pattern inspection of the inspection object to which the flat film of metal material is attached is inevitably lowered. However, the inspection method using the diagonal light and the vertical light as in the present invention can prevent the over-detection of the pattern defect of the inspection object to which the flat film of the metal material is attached, thereby increasing the inspection reliability. For example, the inspection object is a flexible printed circuit board in which a fine pattern is formed by using a semi additive process.

The inspection unit 110 includes a single camera 112, a diagonal illumination member 114 for irradiating diagonal light to the inspection object 10, a coaxial falling illumination member 116 for irradiating vertical light to the inspection object, and a camera ( 112 and the coaxial fall illumination member 116 and the moving member 120 for moving the oblique light member 114. The camera 112 and the diagonal / coaxial fall illuminating members 114 and 116 are moved back and forth by the moving member 120 by a predetermined distance in the longitudinal direction (the direction indicated by the arrow in the drawing) of the inspection object 10. Here, the moving member 120 may be a cylinder type using a hydraulic or various methods using a motor, a ball screw and a transfer nut.

In this embodiment, one camera, the diagonal illumination member and the coaxial fall illumination member are shown to be made of one module, but as shown in FIG. 2, the diagonal illumination member 114 and the coaxial fall illumination member of the two cameras 112. 116 may be provided and used respectively, in which case the moving member may be omitted. As another example, a method of firstly photographing an inspection object by using an oblique illumination member and then secondly imaging by using a coaxial falling illumination member while winding the inspection object in an opposite direction may be used. Even when this method is used, the movable member can be omitted. For example, the camera 112 may be a line scan camera, and the inspection unit 110 may be additionally installed with the camera and the lighting member according to the inspection conditions of the inspection object and the user's requirements. The inspection unit 110 has a processing unit 130 that receives an image captured by the camera 112. The processor 130 is provided as a typical computer system (aka, microcomputer) to control and process various operations according to the automatic optical inspection. The processor 130 receives the first reflection image and the second reflection image from the camera 112 and detects the pattern defect by integrating the first reflection inspection and the second reflection inspection.

Referring back to FIG. 1, when the camera 112 moves forward by the predetermined distance by the moving unit 120, light is radiated in the diagonal direction from the diagonal lighting member 114, and the camera 112 moves to the moving unit 120. At the time of the backward movement by the distance moved forward by the () is irradiated in the vertical direction from the coaxial fall illumination member 114. As described above, in the present invention, the first reflection image obtained by irradiating light in a diagonal direction and the second reflection image obtained by irradiating light in a vertical direction may be sequentially obtained by one camera 112 moving forward and backward. This not only shortens the inspection time but also increases the space utilization of the equipment.

In particular, the pattern inspection in the present invention has a first reflection image obtained by firstly irradiating light in an oblique direction to first distinguish the pattern component and the spatial component to perform pattern shape inspection (single line, short circuit, protrusion, recess) first. (First reflection test). Then, the second reflection image obtained by irradiating light in the vertical direction in the second direction is mainly examined for surface pits by referring to the region of the pattern component obtained in the first reflection image (secondary reflection inspection). Of course, the part not detected in the first reflection image in the spatial component may be seen in the second reflection image, but in the secondary reflection inspection, the main inspection concentrates inspection of the pits on the surface. That is, as can be seen in Figures 4 to 6 below, in order to increase the inspection reliability of the surface patch, the secondary reflection image obtained by irradiating the light in the vertical direction is required.

Specifically. The light irradiated in the diagonal direction from the diagonal illumination member 114 makes the surface patch defects look smaller than the actual ones than the vertical light (because scattering in the surface patches causes the parts to appear bright), and thin surface patches ( Surface deepening) and the like are hardly outlined, but in the case of a pattern shape defect (defect shown in FIG. 6), the outline is clearly shown. On the contrary, even the light irradiated in the vertical direction from the coaxial falloff illumination member 116 has a contour (dent) even in the same way as the actual defect, even for a good surface patch (thin surface depth). Therefore, if the image obtained by the two illuminations having these characteristics is used, it is possible to clearly determine whether the surface dents are good or bad and pattern dents. For example, the order in which the light in the diagonal direction and the light in the vertical direction is irradiated in the present invention may be changed.

4 to 6 are diagrams showing a first reflection image and a second reflection image according to each type of depression. Here, in the first and second reflection images, a white portion represents a pattern component and a dark portion represents a spatial component.

Referring to FIG. 4, a shows a pattern cross section with a recess in the upper surface, and a-1 and a-2 show a pattern cross section a with a good quality recess in the upper surface in the diagonal direction and the vertical direction. The first reflection image and the second reflection image obtained by examination are respectively shown.

First, in the first reflection image (a-2), the depression appears as much as the width of the depression, but in the first reflection image (a-1) even if there is a small depression on the upper surface does not appear. As mentioned earlier, diagonal light is regarded as a bright part when light is transmitted to the camera due to scattering of light inside the recessed part for small depressions belonging to a standard product at the edge of the planar part. Because it doesn't look good. Therefore, the measurement is made at the normal line width. As described above, in the case of a, undetection in the first reflection image and depressions detected in the second reflection image are less than 1/2 of the reference pattern width.

For example, even when the depression is not detected in the first reflection image and the depression detected in the second reflection image is 1/2 or more of the reference pattern width, the fact that the depression is not detected in the first reflection image is not deep. If the depth is wide, but not deep, it can be detected as good.

Referring to FIG. 5, b shows a pattern cross section with deep recesses on the surface, and b-1 and b-2 show a first reflection image obtained by irradiating light on the pattern cross sections b and in a diagonal direction and a vertical direction. Each of the second reflection images is shown.

First, in the first reflection image (b-1), a depression appeared, which may mean that the depth of the depression formed in the pattern is deep or the pattern shape defect is poor. Therefore, the second reflection image must be confirmed for sure confirmation. In the second reflection image, the width of the depression was more than 1/2 of the pattern width. As a result, in the case of b, since the depth of the deepening is deep, it is detected as a poor surface roughness.

Referring to FIG. 6, c shows a pattern section in which one side of the pattern is completely separated, and c-1 and c-2 show a first reflection obtained by irradiating light on the pattern sections c in a diagonal direction and a vertical direction. Show the image and the second reflection image respectively. First, in the first reflection image c-1, the depression appears as much as the width of the pattern disappeared, and in the second reflection image c-2, the depression appears almost the same as the first reflection image. In this case, more than one-third of the reference pattern width was detected in the first reflection test, and almost the same recesses appeared in the second reflection test.

Examining the inspection criteria, the pattern shape defect detects 1/3 or more of the reference pattern width, and the surface coarseness defect detects 1/2 or more of the reference width. That is, in the present invention, if there is a defect in the image in the second reflection test where the pattern shape defect is not detected in the first reflection test, only the difference of 1/2 or more of the existing line width may be detected, thereby greatly reducing the overdetection. .

As described above, even when the inspection unit of the present invention does not use the reflected light, the first reflection image obtained by irradiating light in a diagonal direction when inspecting a pattern formed on a printed circuit board, and the second reflection image obtained by irradiating light in a vertical direction By using to accurately determine the good quality, deep defects, pattern shape, there is a special effect that can increase the inspection quality as much as using the reflected light.

In the above, the configuration and operation of the automatic optical inspection system according to the present invention is shown in accordance with the above description and drawings, but this is only an example, and various changes and modifications can be made without departing from the technical spirit of the present invention. Of course.

As described above, the present invention has a particular effect of reducing overdetection in a printed circuit board in which transmission light inspection is impossible. In addition, the present invention provides a good quality patch using a first reflection image obtained by irradiating light in a diagonal direction for pattern shape inspection on a printed circuit board that is not possible to check the transmitted light, and a second reflection image obtained by irradiating light in a vertical direction, There is a special effect that can accurately determine the deep defect pattern and pattern shape pattern and improve the inspection quality as much as using the reflected light.

Claims (12)

delete In the automatic optical inspection method of a printed circuit board: Inspecting a pattern formed on the printed circuit board by using a first reflection image obtained by irradiating light in a diagonal direction and a second reflection image obtained by irradiating light in a vertical direction; Inspection is carried out in the state in which the flat film is attached to the bottom surface of the printed circuit board to maintain the flatness, the optical inspection method of the printed circuit board. The method of claim 2, The flattening film is an automatic optical inspection method of a printed circuit board, characterized in that made of an opaque material. In the automatic optical inspection method of a printed circuit board: Inspecting a pattern formed on the printed circuit board by using a first reflection image obtained by irradiating light in a diagonal direction and a second reflection image obtained by irradiating light in a vertical direction; The first reflective image is inspected first, and the second reflected image is subsequently inspected. In the automatic optical inspection method of a printed circuit board: Inspecting a pattern formed on the printed circuit board by using a first reflection image obtained by irradiating light in a diagonal direction and a second reflection image obtained by irradiating light in a vertical direction; The printed circuit board is a flexible substrate in the form of a film or tape, and the plurality of substrates are arranged in parallel and simultaneously inspected. In order to maintain the flatness of the plurality of substrates arranged in parallel to the bottom surface of the substrate, the inspection is carried out in the state that the flat film for maintaining the flatness is attached to the automatic optical inspection method of the printed circuit board. In the automatic optical inspection method of a printed circuit board: Inspecting a pattern formed on the printed circuit board by using a first reflection image obtained by irradiating light in a diagonal direction and a second reflection image obtained by irradiating light in a vertical direction; The pattern inspection item of the printed circuit board includes poor surface coarseness, No depressions appear in the first reflection image, And if the dents in the second reflection image are less than or equal to a predetermined width in comparison with the pattern width, detecting as a good surface dents. In the automatic optical inspection method of a printed circuit board: Inspecting a pattern formed on the printed circuit board by using a first reflection image obtained by irradiating light in a diagonal direction and a second reflection image obtained by irradiating light in a vertical direction; The pattern inspection item of the printed circuit board includes poor surface coarseness, In the first reflection image, the depressions appear less than or equal to a predetermined width relative to the pattern width, And if the dents in the second reflection image are greater than or equal to a predetermined width relative to the pattern width, detecting the surface dents as defective. In the automatic optical inspection method of a printed circuit board: In the inspection of the pattern formed on the printed circuit board, the first reflection image obtained by irradiating light in an oblique direction and the second reflection image obtained by irradiating light in a vertical direction; The pattern inspection item of the printed circuit board includes a pattern shape defect, If the depression in the first reflection image is greater than the predetermined width compared to the pattern width is detected as a pattern shape defect automatic optical inspection method of a printed circuit board. delete In the automatic optical inspection method of a printed circuit board: When the pattern formed on the printed circuit board is inspected, pattern shape inspection is first performed by first distinguishing the pattern component and the spatial component with the first reflection image obtained by irradiating light in the diagonal direction first, and then performing the light in the second vertical direction. Using the second reflection image obtained by the irradiation, the area of the pattern component obtained in the first reflection image is referred to, and the inspection is performed on the surface pavement. The printed circuit board is inspected in a state in which a film for flattening is attached to a bottom surface to maintain flatness; The flattening film is an automatic optical inspection method of a printed circuit board, characterized in that the opaque metal material. In the automatic optical inspection method of a printed circuit board: When the pattern formed on the printed circuit board is inspected, pattern shape inspection is first performed by first distinguishing the pattern component and the spatial component with the first reflection image obtained by irradiating light in the diagonal direction first, and then performing the light in the second vertical direction. Using the second reflection image obtained by the irradiation, the area of the pattern component obtained in the first reflection image is referred to, and the inspection is performed on the surface pavement. The first reflection image is obtained by irradiating light in an oblique direction while moving in one direction of the printed circuit board, the second reflection image is obtained by irradiating light in a vertical direction while moving in a reverse direction of the printed circuit board Automatic optical inspection method of printed circuit board. In the automatic optical inspection method of a printed circuit board: When the pattern formed on the printed circuit board is inspected, pattern shape inspection is first performed by first distinguishing the pattern component and the spatial component with the first reflection image obtained by irradiating light in the diagonal direction first, and then performing the light in the second vertical direction. Using the second reflection image obtained by the irradiation, the area of the pattern component obtained in the first reflection image is referred to, and the inspection is performed on the surface pavement. The pattern inspection item of the printed circuit board includes poor surface coarseness, No depressions appear in the first reflection image, And if the dents in the second reflection image are less than or equal to a predetermined width in comparison with the pattern width, detecting as a good surface dents.

Images