JPH10132756A - Appearance inspection apparatus for multilayer ceramic circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an appearance inspection apparatus by which a state inside a microscopic cavity is detected precisely by providing an illumination system which is installed so as to face the central part of the cavity, a plurality of imaging parts which are installed so as to face the peripheral part of the cavity, and an optical system which guides reflected light from the cavity to the imaging parts. SOLUTION: A fiber illumination part 1, which uses an optical fiber, is made to face the central part of a cavity 3 at a multilayer ceramic circuit board 2, and a small camera 4 is made to face the peripheral part of the cavity 3. Then, an optical system 5 which uses a small reflecting mirror 5a and a small reflecting mirror 5b and whose shape is like a periscope is interposed between the fiber illumination part 1 and the small camera 4. Thereby, since the fiber illumination system 1 is faced with the central part of the cavity 3, a shade due to the wall part of the cavity 3 is not generated, and a step inside a wire- bonding-pad-pattern layer does not generate a shade.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for inspecting the appearance of a multilayer ceramic circuit board for inspecting print misalignment and lamination misalignment occurring in the process of manufacturing a multilayer ceramic circuit board.

[0002]

2. Description of the Related Art When manufacturing a multilayer ceramic circuit board such as a ceramic PGA board, a plurality of thin ceramic green sheets on which a circuit pattern has been printed or through holes have been formed are laminated and fired. Molding. At this time, since the printing displacement and the lamination displacement of the circuit pattern may occur, it is necessary to inspect the printing displacement and the lamination displacement after laminating, firing and Ni plating of the ceramic green sheets. At this time, the presence or absence of a defect due to the deviation amount to be inspected is, for example, ± 100 μm from a predetermined dimension.
Since the numerical value is determined such that the range of m is within the standard range and the outside of the standard range is determined to be defective, it is difficult to perform a visual quantitative inspection. Therefore, conventionally, there has been proposed an appearance inspection apparatus for a multilayer ceramic circuit board for inspecting a printing shift or a stacking shift occurring in a manufacturing process of the multilayer ceramic circuit board. For example, as shown in FIG. 6, these appearance inspection devices illuminate a portion to be inspected from above, detect the reflected light with a TV camera installed above, and obtain a circuit pattern of the circuit pattern based on the detected image. Printing and lamination defects are determined.

[0003]

However, in the conventional visual inspection apparatus as shown in FIG. 6, when the situation inside the extremely small cavity in the circuit board is to be detected by a TV camera, the wall portion of the cavity is to be detected. However, there is a problem that an accurate image cannot be obtained because of the shadow.

The present invention has been made in view of such problems of the prior art, and provides an apparatus for visually inspecting a multilayer ceramic circuit board, which can accurately detect a situation in a very small cavity. With the goal. Another object of the present invention is to provide an appearance inspection apparatus for a multilayer ceramic circuit board, which can appropriately calculate the size of a boundary between a board and a circuit pattern.

[0005]

An apparatus for inspecting the appearance of a multilayer ceramic circuit board according to the present invention for solving such a problem is provided so as to face substantially the center of a cavity of the circuit board, and is provided in the cavity. An illumination system for irradiating light, a plurality of imaging units provided to face the periphery of the cavity, and imaging the inside of the cavity, and an optical system for guiding reflected light from the cavity to the imaging unit, It is composed.

In the present invention, the size of the boundary between the substrate and the circuit pattern is further obtained by subtracting the density product sum calculation value of the substrate from the density product sum calculation value of the circuit pattern,
It is preferable to provide a boundary calculating unit which is obtained by multiplying the difference by a preset threshold level ratio to calculate the difference.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing an appearance inspection apparatus for a multilayer ceramic circuit board according to the present embodiment. Conventionally, when imaging a cavity of a circuit board, both an illumination unit that irradiates light to the cavity and a small camera are opposed to the center of the cavity, and imaging is performed while irradiating the inside of the cavity. However, when an image is taken in a particularly small cavity, at least one of the illumination unit and the small camera comes off the center of the cavity toward the periphery. For this reason, if the illuminating portion deviates from the center of the cavity, the wall of the cavity and the like become shadowed, and it becomes difficult to capture an accurate pattern. Also,
If the miniature camera deviates from the center of the cavity, there is a disadvantage that a part of the cavity becomes blind spot.

Therefore, in this embodiment, as shown in FIG.
A fiber illuminating unit 1 using an optical fiber is opposed to the center of the cavity 3 of the multilayer ceramic circuit board 2 and four small cameras 4 are opposed to the periphery of the cavity 3 (see also the plan view of FIG. 2). . An optical system 5 like a periscope using the small reflecting mirrors 5 a and 5 b is interposed between the fiber illumination unit 1 and the small camera 4. Thereby, since the fiber illuminating unit 1 faces the center of the cavity 3, the shadow of the wall of the cavity 3 does not occur. That is,
In the present embodiment, as for the illumination of the cavity 3, the fiber illumination unit 1 using a thin optical fiber is installed at the center of the cavity 3 as shown in FIG. Can not be made. If a shadow is formed, the shadow is added to a printing gap distance at the time of a printing shift (pull-back) inspection described later, and an error increases. Therefore, it is necessary to prevent the shadow from being formed. Further, in the present embodiment, since the four small cameras 4 are arranged adjacent to each other so as to face the peripheral portion of the cavity 3, there is no blind spot in imaging by the small cameras 4. In the first embodiment, since the small camera 4 is set on the small XY stage 6 via the holder 7, the imaging position can be changed arbitrarily.

Next, the operation of the present embodiment for detecting a lamination shift will be described with reference to FIG. First, a standard pattern of each layer and each side (for example, in FIG. 3, a total of eight patterns (2 × 4 = 8 patterns) of four sides of each of two wire bonding pad (W / B) pattern layers) is stored in advance. The stacking shift is detected by detecting each pattern position by gray pattern matching. At this time, if the glare on the surface caused by the previous illumination is smoothed by the averaging process and a gray search is performed, the image processing is stabilized.

Next, an operation for inspecting a print shift (pullback) will be described with reference to FIG. FIG. 4 is an enlarged view of a part (a part indicated by R) in the cavity of FIG.
0 is a step layer, 11 and 12 are wire bonding pad patterns made of nickel plating, 13 is a ceramic substrate,
Reference numeral 14 denotes a boundary between the pattern and the ceramic substrate. The calculation of the boundary line between the pattern and the substrate according to the present embodiment is performed by a light-dark density product-sum calculation in a certain direction. For example, a wire bonding pad (W /
B) One layer of pattern and wire bonding pad (W /
B) When measuring the print gap distance (pullback) L between the two layers of the pattern, the point from point A to point B is obtained from the result of the density product sum calculation in the x direction (see FIG. 5). Boundary pixel position ya, yb based on gray level difference in window W
Is a preset threshold level ratio SL
(%) (E.g., about 30% is good), and is obtained by an inter-pixel operation (see the following equation). Ya = (GA _max −G _min ) × SL Yb = (GB _max −G _min ) × SL However, in the above equation, ya and yb are obtained by, for example, performing an inter-pixel calculation up to 0.1 pixel.

Then, the printing gap distance L is obtained by the following equation by multiplying by the pixel size constant P (μm / pixel). L = (yb-ya) × P This value is determined to determine a non-defective product or a defective product.

The feature of this method is that a boundary value is not found by a fixed density value, but is calculated by a ratio of a difference between light and dark portions. The difference is that the difference from the true value of the dimension measurement due to the difference is small (about ± 0.1 pixel). Also, by increasing the number of integral pixels, reproducibility is high. However, since this method integrates in the X or Y direction, it is necessary to perform a rotation correction process when rotating.

Further, in the handling apparatus according to the present embodiment, a substrate is taken out of a tray containing 12 pieces of packages (4 rows × 3 columns) by suction every three pieces.
Next, after the substrate is positioned by the substrate positioning machine, the substrate is transferred to an inspection table, and after another inspection, the above-described wire bonding pad pattern layer and pattern deviation are inspected. Then, according to the determination result of the presence / absence of the defect by the deviation inspection, the trays are packed and stored in a tray in a pre-selected storage location among the five storage locations.

[0014]

As described above, according to the present invention, since the illuminating portion is opposed to the center of the cavity, no shadow is generated by the wall of the cavity, and an accurate image can be detected. Further, in the present invention, by providing an optical system for transmitting the reflected light from the cavity to the imaging unit, the plurality of imaging units are opposed to the peripheral portion of the cavity instead of the central portion thereof, and the Since the inside of the cavity is imaged, there is no blind spot in the image inside the cavity, and an accurate image can be detected.

Further, in the present invention, the difference between the size of the boundary product between the substrate and the circuit pattern is obtained by subtracting the density product-sum calculation value of the substrate from the density product-sum calculation value of the circuit pattern,
The difference is calculated by multiplying the difference by a preset threshold level ratio.
For this reason, the size of the boundary line (boundary value) is not found by a fixed density value, but is calculated by the ratio of the difference between the light and dark portions. The difference from the true value of the dimension measurement due to the difference is small (± 0.
(About one pixel). There is also a merit that the reproducibility becomes high by increasing the number of integral pixels.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a ceramic circuit board appearance inspection apparatus according to an embodiment of the present invention.

FIG. 2 is a plan view schematically showing the configuration of the embodiment.

FIG. 3 is a diagram for explaining an operation of inspecting a stack displacement of the ceramic package according to the present embodiment;

FIG. 4 is a partially enlarged view of the inside of the cavity of FIG. 3, and is a diagram for explaining an operation of measuring a print gap distance according to the present embodiment.

FIG. 5 is a diagram for explaining a print shift measuring operation according to the embodiment;

FIG. 6 is a schematic view showing a conventional circuit board appearance inspection apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fiber illumination part 2 Multilayer ceramic circuit board 3 Cavity 4 Small camera 5 Optical system 5a, 5b Small reflection mirror 6 Small XY stage 7 Holder 8 Ceramic PGA 9 Cavity 10 Step layer 11 Wire bonding pad pattern 1 layer 12 Wire bonding pad pattern 2 Layer 13 Substrate 14 Boundary (boundary value)

Claims (2)

[Claims] 1. An apparatus for inspecting the appearance of a multilayer ceramic circuit board for inspecting print misalignment or lamination misalignment of a circuit pattern generated in a process of manufacturing a multilayer ceramic circuit board, comprising: An illumination system provided to face the cavity and irradiating the cavity with light; a plurality of imaging units provided to face the periphery of the cavity and imaging the inside of the cavity; and an imaging unit configured to reflect light reflected from the cavity. And a optics system for guiding the appearance of the multilayer ceramic substrate. 2. The method according to claim 1, wherein the size of the boundary between the substrate and the circuit pattern is obtained by subtracting the density product sum operation value of the substrate from the density product sum operation value of the circuit pattern, and calculating the difference. An appearance inspection apparatus for a multilayer ceramic substrate, comprising: a boundary calculation unit which is calculated by multiplying a predetermined threshold level ratio.