JPS629204A - Positioning method for printed board - Google Patents

Abstract

PURPOSE:To find a standard point on the conductive pattern on a printed board precisely by digitizing an image obtained from a camera and performing processing such as spatial differentiation, and extracting a border line where brightness varies. CONSTITUTION:A device consists of the TV camera 2, an orthogonal coordinate type robot 3, a microcomputer 4, an image processor 5, and a YAG laser device 6. The conductor pattern on the printed board 7 is observed through the camera 2 and processor 5 to detect the edge 31 of the pattern from the difference in contrast from the surface of the board 7, and the edge is approximated as straight lines 32. Then, the intersection of the straight lines 32 is found as the vertex of the pattern. Further, the center point of positioning is calculated from several vertexes. The deviation of the center point from a coordinate center is detected. Further, the robot 3 carries a semiconductor chip 8 into the visual field of the camera 2 and the processor 5 corrects the shift in relative position between the pattern and chip 8; and then the chip 8 is placed on the board 7 at a specific position and soldered by the laser device 6 on YAG laser basis. Thus, chip packaging is made high in accuracy and automated and the yield is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is intended for use in devices that mount semiconductor elements on printed circuit boards that require particularly high-precision mounting. The present invention relates to a precision positioning method.

(Conventional technique #I) Chip parts of semiconductor devices (
Automatic mounting, which involves grabbing a chip (hereinafter referred to as a chip), transporting it to a predetermined position on a printed circuit board, and fixing it by soldering, is quite common. At this time, the printed circuit board is usually placed on an X-Y table so that it can be moved between two positions: a position where the board is mounted and a position where the chip is mounted. And X.

A robot arm with degrees of freedom in the Y and Z axes grabs the chip at the chip supply position, carries it to a predetermined position, aligns it, and places the chip on it.

Here, the positioning standard becomes an issue. The conductor pattern is formed on the board itself with considerable precision, and the positional deviation accuracy of the edge of the conductor pattern with respect to the edge of the board is ±
It is about a/mvn. Therefore, if the edge is used as a reference when fixing the board, the conductor pattern will also be placed on the X-Y table within ±0. /a accuracy is fixed. Therefore,
Conventionally, chips were carried and mounted to a position based on this board edge.

(Problems to be solved by the invention) However, when performing even more precise positioning,
This misalignment of the conductor pattern on the substrate has an effect, and even if other accuracy is improved, there is a problem that the limits are determined by this misalignment.

In the case of high-frequency semiconductor devices and the like, the precision of conventional mounting methods is insufficient because even a slight misalignment between the conductor pattern and the chip deteriorates the high-frequency characteristics.

It is an object of the present invention to solve these problems.

(Means for Solving the Problems) As shown in FIG. 1, the devices used in the present invention include an X-Y table 1, a TV camera 2. Cartesian coordinate robot 3 and microcomputer 41 that controls them 5. Soldering is performed using a YAG laser device 6.

The procedure is to first look at the conductor pattern on the substrate γ using the camera 2 and the image processing device 5, and determine the reference point on which the semiconductor element and child chip 8 on the conductor pattern should be placed, and the coordinate center point on the screen. Find the difference between

Next, the orthogonal coordinate type four pot 3 takes out the chip from the pallet and carries it within the field of view of the camera 2, and after correcting the relative positional deviation between the conductor pattern and the chip using the image processing device 5, the chip is placed on the substrate 7. The chip 8 is placed on the position and soldered using a YAG laser from the YAG laser device 6. In addition, 9 is a laser emitting port, and 10 is a vacuum suction chuck.

(Function) The present invention is a method for precisely determining the reference point of a conductor pattern on a printed circuit board. The image processing unit of this device digitizes the image obtained from the camera, performs processing such as spatial differentiation, and extracts boundaries where brightness changes. As a result, the outline of the area where the conductor pattern is provided can be seen as a line due to the difference in brightness from the other substrate surfaces. The information on this line is processed by the microcomputer 4 to find the reference point.

(Example) The conductor pattern captured by the camera is, for example, shown in Figure 2 (
Suppose that (a) and (b) are two wedge shapes facing each other. (The comb is the actual pattern, (
b) is an ideal pattern.

Now, assume that the position where the high-frequency chip is placed is equidistant from both sides of the wedge shape, and is on a line that bisects the width of the conductor pattern. Therefore, it is the midpoint P of the two wedge-shaped vertices. Note that 20 is a solder plated surface.

Ideally, the wedge shape is formed as a straight line as shown in Figure 2, and the apex is also represented as a clear line.However, in reality, the wedge shape is formed as a straight line as shown in Figure 2. It is often the case that a clear peak is not sought.

In the present invention, as a solution to such a case, the introduced line is approximated by a straight line as shown in FIG.

Since the position of the conductor pattern on the printed circuit board, which is set at a predetermined position in front of the camera, is determined, the position of the straight line to be determined is also determined. Therefore, it is clear in advance which line will be approximated as a straight line. Of this line, by removing the bent part of the curve 1531 obtained by image processing near the vertex 30 within a certain range, a line that is quite close to a straight line can be obtained. By approximating these with a straight line 32 and finding their intersection, the apex 30 of the wedge-shaped conductor pattern can be found. Therefore, if we find the midpoint from the vertices of the two wedge shapes obtained in this way, we get
This becomes the reference point.

(Effects of the Invention) By analyzing the image, the conductor pattern on the board can be positioned with high precision. Furthermore, even if there is some distortion in the conductor pattern, it can be approximated to a certain extent and the point where the chip will be placed can be indicated.

This makes it possible to automate chip mounting with high precision and improve yield.

[Brief explanation of the drawing]

The drawings all relate to the printed circuit board positioning method of the present invention; Fig. 1 is an explanatory diagram of the apparatus used in this method, Fig. 2 is an explanatory diagram of the printed pattern, (A) is the actual pattern, (→ is An explanatory diagram of an ideal pattern, and Fig. 3 is an explanatory diagram of a method of linear approximation. 1... X-Y table, 2... TV camera, 3...
・Orthogonal coordinate robot, 4...Microcomputer, 5...Image processing device, 6...YAG laser device, T...Substrate, 8...Semiconductor element chip, 9...Laser emission port , 10... Vacuum suction chuck, 20... Soldering surface, 30... Vertex, 31... Line determined by image processing, 3
2...Approximate straight line.

Claims (1)

[Claims] 1. To mount semiconductor chip components onto a conductor pattern on a printed circuit board, the printed circuit board fixed on an X-Y table is moved, the chip components are moved using a Cartesian coordinate robot, and the conductor pattern is positioned. In the method of carrying the chip component to a predetermined position and placing it on the conductor pattern, the conductor pattern is viewed from above with a TV camera when positioning the conductor pattern, and the deviation of the center position is detected from the image. When capturing an image, illumination is applied from approximately the same direction as the camera, and the edge of the conductor pattern is detected from the difference in contrast between the board surface of the printed circuit board and the conductor pattern, and the detected edge is aligned with a straight line. A method for positioning a printed circuit board, which is characterized by approximating the line as the vertex of the conductor pattern, determining the center point of positioning from several vertices, and detecting a deviation from the center of coordinates.