JPH01123101A - Measurement of pin length - Google Patents

Abstract

PURPOSE:To enable high precision automatic measurement by a method wherein a video signal generated by irradiation from the vertical direction of a pin is sliced into binary video signals, a rectangular area where a pin exists is cut out and distribution of pin projection is calculated in the area. CONSTITUTION:A laser beam is emitted from the laser head, and a row of pins of a PGA part is irradiated by the slit beam from its tip to the foot. The reflection from the pin forms an image with a camera lens from a slant direction, and is converted into a video signal by the camera. Based on this video signal, a binary level determination device 1 determines the threshold, by which a binary processor 2 slices the video signal into binary video signals, and stores them in an image memory 3. A projection distribution processor 4 cuts out rectangular areas containing pins from binary signals read from a memory 3 and calculates the pin projection distribution in which a total number of white pixels is calculated per line along an approximately perpendicular direction to the pin. Then a height measurement processor 6 calculates each pin length with both ends of the projection distribution to be determined as the desired pin length.

Description

[Detailed Description of the Invention] [Summary] Regarding a pin length measurement method for measuring the length of a pin, the pin height (length) of a component to which a plurality of pins are attached is automatically measured in a non-contact manner and with high accuracy. For the purpose of A projection distribution processing section that calculates the projection distribution of the region where each pin included in the image signal exists, and a height measurement processing section that measures the height of the pin from each projection distribution obtained by the projection distribution processing section. and is configured to output a length corresponding to the height of each pin measured by the height measurement processing section.

[Industrial application field]

The present invention relates to a pin length measurement method for measuring the length of a pin.

[Problems to be solved by the prior art and the invention] As the density of printed circuit boards becomes higher, the use of parts for high-density mounting is increasing. In particular, a pin grid array component (Pi
n Grid Array (hereinafter referred to as PGA) is
It is used in a wide variety of fields because it can have a very high packaging density.There is a demand for the development of a device that can automatically and accurately inspect the pin arrangement state of this PGA.

For example, the height of each pin is determined to prevent erroneous soldering, since when reflow soldering a PGA to a printed circuit board, pins with a lower height will not reach the paste solder and will result in erroneous soldering. This is one of the important inspection items.

An object of the present invention is to automatically and non-contactly and highly accurately measure the pin height (length) of a component to which a plurality of pins are attached.

[Means for solving problems]

FIG. 1 shows a basic configuration diagram of the present invention.

In FIG. 1, a binarization level determination unit 1 converts an image signal into a binary image signal from an image signal generated by irradiating from the height direction of the pin of the component and photographing from an oblique direction using a camera. (This will be described later using FIG. 5).

The binarization processing unit 2 slices an image signal generated by photographing using a camera, and generates a binary image signal according to the darkness value notified from the binarization level determination unit 1.

The image memory 3 stores 2 images generated by the binarization processing section 2.
It stores value image signals.

The projection distribution processing unit 3 cuts out a rectangular area in which the pin of the component exists from the binary image signal read out from the image memory 3, and calculates the projection distribution (
As shown in FIG. 7(b), the total number of white pixels is calculated for each line in a direction substantially perpendicular to the pin.

- The time storage memory 5 is a memory that temporarily stores data such as the projection distribution calculated by the projection distribution processing section 4.

The height measurement processing section 6 measures the height (length) of each pin, as shown in FIG. 7, based on the projection distribution of each pin calculated by the projection distribution processing section 4.

[Effect]

As shown in FIG. 1, in the present invention, a binarization level determination unit 1 determines a threshold value from an image signal generated by irradiating a component from the height direction of a pin and photographing it from an oblique direction using a camera. Then, using this threshold value, the binarization processing section 2 slices the image signal to generate a binary image signal and stores it in the image memory 3. The projection distribution processing unit 4 cuts out a rectangular area in which the pin of the component exists from the binary image signal read out from the image memory 3, and draws a line approximately perpendicular to the pin as shown in FIG. 7(b). The projection distribution of the pins is calculated by calculating the total number of white pixels for each time. Then, the height measurement processing section 6
For example, both ends of the projected distribution of each pin are calculated as the length of the pin.

Therefore, it is possible to automatically measure the height (length) of a pin in a non-contact and highly accurate manner based on an image signal generated using a camera from an oblique direction and irradiated from the height direction of the pin.

[°Example]

Next, the configuration and operation of one embodiment of the present invention will be explained in detail using FIGS. 2 to 7.

FIG. 2 shows a configuration diagram of one embodiment of the present invention. In the figure, the laser head 12 to which power is supplied from the laser power supply 11 is
Emits a laser beam. This emitted laser beam is spread into a fan shape perpendicular to the plane of the paper by the first stage cylindrical lens 13 and the second stage cylindrical lens 14.
One row of pins of the GA component 16 is irradiated with a laser slit beam from the tip of the pin to the root as shown in the figure.

The irradiated position is adjusted by moving the component clamping mechanism 15 using x, y, z, and θ direction moving mechanisms (not shown). The reflected light from the pin of the PGA component 16 irradiated by the slit beam is
An image is formed by the imaging lens 18 from the oblique direction shown in the figure, and C
The signal is converted into an image signal by the camera 19 under the control of a CU (camera control unit) 20 and stored in the image memory 3. Under the control of the memory control unit 22, the image signals stored in the image memory 13 are
The processed image is displayed on the monitor 21.

The program 23 is a procedure for executing the various processes described using FIG. . - The time storage memory 5 stores intermediate results of processing and the like.

The external IF board (external interface board) 24 is
This is an interface port for exchanging data with the outside. The MPU (microprocessor) 25 performs the processing described using FIG. 1 based on the program 23. Note that the bandpass filter 17 transmits only laser light and blocks other disturbance light.

The operation of the configuration of one embodiment of the present invention will be sequentially explained below.

FIG. 3 shows the movement path of the pin part irradiated by the laser slit beam. FIG. 3(A) shows the irradiation start position, and FIG. 3(B) shows the irradiation end position. In this way, the pins arranged on the PGA are slid at the pitch interval of the pins so as to sequentially irradiate each row. The state in which each row of pins is irradiated by the laser slit beam is photographed by a camera, an image signal is generated, and the image signal is stored in the image memory 3.

FIG. 4 shows an explanatory diagram of the image detection process. To measure the height of a pin according to the present invention, only the reflected light from the tip and root portions of the pin is required, so only the image fδ of both is generated by the following processing.

FIG. 4(a) shows a cross-sectional view of the pin of the component. Slit illumination light (laser slit beam) from the lower left direction in this figure
Set it to irradiate in the direction from the tip of the pin to the root. This allows light to be reflected only from the tip and base of the pin.

FIG. 4(b) shows an analog signal. This represents an analog image signal generated by capturing an image of FIG. 4(a) from the bottom side of the figure with a television camera.

FIG. 4 (C1 indicates a digital signal (binary image signal). This is the analog image signal of FIG. Represents a binary image signal generated by binarization.

This binary image signal is such that only the tip and base portions of the pin appear as "1" (white) pixels.

FIG. 4 (dl indicates a digital image. This is the fourth
This is a two-dimensional display of the digital signal in Figure (C). The small oval area on the left represents the tip of the pin, and the large triangular area on the right represents the base of the pin. but,
The triangular area actually overlaps with the shadow of the pin in the foreground, and only the "V" shaped part (shown in Figure 7 (a)) excluding the dotted part in the figure is displayed. Become.

FIG. 5 shows an explanatory diagram for determining the binarization level. In the figure, the horizontal axis represents the white level of pixels in the binary image signal, and the vertical axis represents the number of pixels at that time. This histogram represents the relationship between the luminance information (level) for one screen that has been A/D converted into, for example, a 256-gradation digital image signal and the number of pixels. In this histogram, the region "B" represents the level of the background part, for example, the level of the background part drawn with diagonal lines in Figure 4, and the region "A" represents the level of the tip and base of the pin, for example, the level shown on the left side of Figure 4. It represents the level of the small oval part and the large "V" shaped part on the right side (excluding the shadow part of the front pin). Therefore, in order to extract only the tips and bases of the pins, the diagonal line marked with "A" in the figure corresponds to the total area (total number of pixels) calculated based on the total number of pins, the area of the tips of the pins, etc. The lower end of the part i [T is 2
Determined as the value level (dark value). Using this binarization level T (darkness value, threshold value), the analog signal in Fig. 4 is sliced to generate a binary digital image signal shown in Fig. 4 fdl. It is possible to automatically determine the binarization level based on this and generate a binary image signal in which only the tip and root portions of the pin are extracted.

Figure 6 shows an explanatory diagram of edge position detection. This is the edge (joint surface of the PGA pin) that is the reference position (length measurement start position) in order to measure the height of each pin on the input screen. This is to explain the process of finding . In general, P.G.
The screen may be tilted or curved to some extent due to the positional relationship between the clamp device that holds A and the camera, the distortion of the imaging lens 18, etc. The area is divided vertically as shown, and the projection distribution (FIG. 7(b)) is obtained for each of these divided areas. From this obtained projection distribution, each edge position of the divided area is calculated as shown in the figure. The edge position (edge line) is calculated by the above processing, so next, from the left end position "E" of the pin of the component (position "E" in Figure 6), the illustrated pin with the pitch interval of the pin as one area is calculated. Set the search area. Then, the highest white level pixel in this pin search area (the pixel at the position ■ in FIG. 7) is found, and this is set as the position of the tip of the pin.

Through the above processing, the position of the fuji in Figure 6 and the position of the tip of the pin (the position of the top of the small ellipse at the top of the figure) have been detected.

Figure 7 shows an explanatory diagram of pin height measurement.
As shown in the figure, the shortest distance between the calculated edge line (edge position) and the pin tip detected as ■ in the figure,
That is, when a perpendicular line is drawn from the tip of the pin to the edge line, the distance of the perpendicular line is calculated as the pin height. This results in
Even if the pin is tilted to some extent due to the influence of the positional relationship between the clamp device that holds the PGA and the camera, it is possible to accurately measure the correct pin height by correcting this tilt.

〔Effect of the invention〕

As explained above, according to the present invention, the image signal that is irradiated from the height direction of the pin and imaged from an oblique direction using a camera is sliced at a predetermined binarization level, and only the tip and root portions of the pin are sliced. A binary image signal consisting of
The configuration uses a configuration that measures the pin height by detecting the measurement reference position (edge position) and the pin tip position from the value image signal, making it possible to measure the pin height (length) non-contact and with high precision. Can be measured automatically.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the principle of the present invention, Figure 2 is a diagram showing the configuration of one embodiment of the present invention, Figure 3 is a diagram explaining the movement path of the pin parts, Figure 4 is a diagram explaining the image detection process, and Figure 5 is a diagram explaining the image detection process. FIG. 6 is an explanatory diagram of determining the disulfide level, FIG. 6 is an explanatory diagram of edge position detection, FIG. 7 is an explanatory diagram of pin height measurement, and FIG. 8 is an example of pin parts. In the figure, 1 is a binarization level determination section, 2 is a binarization processing section, and 4
6 represents a projection distribution processing section, and 6 represents a height measurement processing section. Fig. 5 ([])
(a) Explanatory diagram of vertical height 1 constant Fig. 7 Pin parts properties 11 Fig. 8

Claims (1)

[Claims] In a pin length measurement method for measuring the length of a pin, a binarization processing unit (which irradiates light from the height direction of the pin and binarizes an image signal photographed using a camera) 2), a projection distribution processing unit (4) that calculates the projection distribution of the area where each pin included in the binary image signal binarized by the binarization processing unit (2), and and a height measurement processing section (6) that measures the height of each pin from each projection distribution obtained by the distribution processing section (4). A pin length measurement method characterized in that it is configured to output a length corresponding to the length of the pin.