JPS63179245A - Inspection system for deviation in chip position on printed circuit board - Google Patents

Abstract

PURPOSE:To accurately display the mounting states of respective chips at a high speed by structuring a photodetection part which uses an annular light source and has an image pickup camera positioned nearly in its center. CONSTITUTION:Image data picked up by the CCD camera 3 which has the annular light source 1 is supplied to an image coordinate transformation device 10 to convert a coordinate position signal corresponding to an image pickup visual field into a time series signal, which is stored in a measurement coordinate storage device 20 momentarily at a high speed. The coordinate points of each chip on a circuit board are stored in the device 20 after the whole of one printed circuit board is scanned by the camera 3 in >=1 step with a proper image pickup visual field. A reference coordinate storage device 30, on the other hand, is stored with coordinate points of respective chips on the circuit board previously, pieces of information stored in the devices 20 and 30 are read out and supplied to an arithmetic unit 40. Then data at respective reference coordinate points of the respective chips and data at corresponding measurement coordinate points are compared to find their deviation, so that the part of the shadow of each chip which is mounted at a land part and projected is displayed 50.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a method for testing misalignment of chips on a printed circuit board, which accurately inspects and displays misalignment of circuit components mounted on a printed circuit board. be.

(2) Background of the Technology Electronic circuits in which circuit components such as resistors, capacitors, and chips, such as chips, are mounted automatically or manually on printed circuit boards have been used in large numbers in various devices. In particular, with the current advances in science and technology, technology has been developed to automatically and quickly mount a large number of chips on the circuit board, making mass production possible.

However, when a large number of chips are mounted on a circuit board automatically and at high speed, some of the chips mounted on the board may be mounted out of position. This is often the cause of failure later on.

In order to inspect the misalignment of chips on these circuit boards,
Visual inspection by a staff member may be acceptable, but in the modern era of mass production, visual inspection is not only inefficient but also requires a large number of manpower, resulting in high costs.

For this reason, several devices have been proposed for mechanically (electronically) inspecting the misalignment of chips.

One of them is a mask-based device. In this device, a mask pattern with a window corresponding to each chip component is used to illuminate a part of the chip component protruding from the window, and to locate the part of the chip component. Inspecting for misalignment. However, with this mask pattern method, it is necessary to prepare a mask pattern with at least one or more good intentions corresponding to each component, and when the number of chips on a circuit board increases, it may be necessary to create a corresponding mask pattern. In addition to being complicated, there are problems with accuracy because the light that is incident with good intentions may be reflected by chip components or other components, or may interfere with each other.

Furthermore, as shown in Figure 4(a), a device that uses a method that shines light obliquely onto each chip mounted on a board and captures the shadow to inspect the positional deviation of chip components is also considered. ing. This method certainly has an advantage over the mask pattern method because it does not require the preparation of a complicated mask pattern.

However, this method works well when the packaging density on the board is low, but as the packaging density of chips on the printed circuit board increases as it does today, small chips adjacent to one relatively large chip are The disadvantage is that it gets in the shadow of the chip, making it impossible to detect its position. That is, on the actual printed circuit board, the
:As shown in I), actual large and small circuit components (chips)
is installed. Therefore, in the conventional method, the light is applied obliquely, making it impossible to detect the position of a small (low height) chip that is in the shadow of a larger chip. Therefore, even if a small chip is misaligned, there is a drawback that the state cannot be detected.

(3) Purpose of the Invention Therefore, the purpose of the present invention is to solve the above-mentioned drawbacks of the prior art, and to improve the position of the mounted circuit components even if the mounting density of the circuit components (chips) on the printed circuit board increases. Another object of the present invention is to provide a chip positional deviation inspection method on a printed circuit board that detects and displays the positional deviation reliably and at high speed.

(4) Structure of the Invention In order to achieve the above object, the chip positional deviation inspection method of the present invention uses an annular light source, and an imaging camera is provided approximately at the center of the light source, so that the light source and the circuit board are connected to each other. By setting the height between the chips at a predetermined distance and shining the light from the light source almost directly above each chip, a shadow is created around the entire periphery of each chip, and by detecting the shadow, the positions of all chips can be determined. The chip positional deviation inspection method on the printed circuit board is configured to reliably detect and display the positional deviation.

(5) Embodiment of the Invention FIG. 1(a) shows the overall schematic configuration of an embodiment of an inspection method for accurately inspecting the positional deviation of circuit components (chips) mounted on a printed circuit board according to the present invention. shows.

That is, in FIG. 1(a), the photodetector 100 according to the present invention includes an annular light source (lamp) 1. Hood for the lamp2. and an imaging camera, for example, a CCD camera 3, and the annular light source of the photodetector 100 is mounted on a support 4 movable at least in a direction perpendicular to the printed circuit board. FIG. 1(C) shows a state in which the hood for the lamp is removed, and light is irradiated from the annular lamp 1 onto the chip C mounted on the printed circuit board 9 from almost directly above. I have to.

The printed circuit board 9 is mounted on a carrier 7 with wheels 8, and can freely move on the rails 6 in a fixed direction. Note that the carrier can be controlled by a motor means (not shown) and a control device for controlling the motor means so as to automatically move or stop at a predetermined position. Since the means are well known to those skilled in the art and this is not the point of the invention, further detailed description is omitted. .

In the present invention, it is particularly important to note that the annular lamp 1
The light is irradiated from almost directly above each chip of the printed circuit board 9. Therefore, in the photodetecting device 100 consisting of the lamp 1 and the CCD camera 3, if the distance between the substrate 9 and the annular lamp 1 becomes larger than a predetermined value, the shadow of each chip mounted on the substrate 9 On the other hand, as the CCD camera 3 is made smaller than a certain predetermined value, that is, as the CCD camera 3 is brought closer to the substrate, a shadow will be formed over the entire outer periphery of each chip. However, if the lamp 1 is brought too close to the substrate 9, the luminous intensity from the lamp becomes strong and the difference in brightness between each chip becomes so small that shadows cannot be detected. Therefore, the height H that produces an appropriate shadow of the chip is determined to be a predetermined distance.

This point in the inspection method of the present invention is different from the conventional method of detecting the actual position of the chip or its positional deviation by detecting a shadow biased to one side of the chip by irradiating light from an angle. Significantly different. This is because the conventional thinking was based on the concept that shadows of objects and other objects are created by light shining at an angle.

FIG. 2 is an enlarged analytical view of a case where a certain chip mounted on the printed circuit board 9 of FIG. 1 is misaligned. The location where each chip is mounted on the circuit board 9 is determined in advance on its coordinates during automatic mounting. Therefore, for example, as shown in FIG. 2, some reference coordinate points P+ of the window (marginal portion W corresponding to the outer periphery of the resistor indicated by the dotted line and its shadow) where the chip C such as a resistor element should originally be correctly mounted, h, P:1・
... is stored in the storage device in advance, and the outer periphery and the shadow part S of the resistor photographed by the CCD camera 3 are detected to determine the corresponding coordinate point P I of the resistor actually installed.
'+Pt', Pff'... are determined, and the reference coordinates P1. P2. P, and by calculating the deviation, it is possible to know the mounting state of each chip on the printed circuit board 9. Furthermore, if a reference value for determination is provided, it is possible to determine whether the product is good or bad by comparing the deviation value with the reference value.

In other words, when mounting a chip such as a resistive element shown in FIG. 2, in the state (if the position is shifted), the board 9 is mounted almost vertically at a predetermined height H due to the annular shape ≠≠→1 shown in FIG. 1. If irradiated from above, a shadow S will be cast on the entire periphery of the chip.
Can be done. However, the land area that connects the chip is
Generally, it is made of copper (or copper-plated) for connections, so it reflects light well, but other surfaces such as the surface of the board or the surface of the chip such as a resistor element are colored. Since there is little reflection of light, the contrast between the brightness of the shadow part projected on the land and the part where the light is reflected is clear, so the reference coordinate point in that part and the actual CCD camera 3 By comparing the coordinate points of the shadows measured by and processing the data, it is possible to display the shadows projected on the land and the areas where the light is reflected in black and white contrast. Therefore, it is possible to inspect and display the mounting state of each chip on the substrate, including the chip that is misaligned.

FIG. 3 shows an embodiment of an apparatus for data processing images detected by a COD camera using the inspection method of the present invention.

Image data photographed by a CCD camera 3 having an annular lamp 1 as shown in FIG. (for example, RAM) at high speed and moment by moment.

After the CCD camera 3 scans an entire printed circuit board in one or more steps with a proper imaging field of view, the coordinate points of each chip on the board are stored in the storage device 20. become.

On the other hand, the reference coordinate storage device 30 (for example, a ROM may be used)
Since the reference coordinate points of each chip on the substrate 9 are stored in advance, the information stored in the two storage devices 20 and 30 is read out and given to the arithmetic unit 40, and the reference coordinate points of each chip are stored in advance. By comparing and processing the data between the point and the corresponding measurement coordinate point and determining the deviation, the shadow of each chip mounted and projected on the land can be displayed. Therefore, it is possible to know the wearing state.

It goes without saying that it is possible to display the test results of the chip attachment state on the display device 50 and print the test results using the printing device 60 using techniques well known to those skilled in the art.

Although not shown, the comparison (contrast) between the shadow part of the chip C projected on the land area (black signal) and the part corresponding to the other reflected light (white signal) is also shown. A threshold circuit can be provided in front of the image coordinate transformation device 10 for greater clarity and easier viewing of the chip attachment status.

(6) Effects of the Invention As described above, the method for inspecting chips on a printed circuit board according to the present invention uses an annular light source with a structure in which the lens of an imaging camera, such as a COD camera, is located approximately in the center of the annular light source. A light detection unit is used to shine light onto each chip mounted on the substrate from almost directly above, and by adjusting the distance between the annular light source and the substrate to create a shadow over the entire outer periphery of each chip. In particular, the contrast between the shadow projected on the metal land and its reflected light is captured to accurately and quickly display the mounting status of each chip.

Therefore, in the present invention, since an oblique light beam is not used as in the conventional method, the shadow of the chip projected onto the land is not biased, and an approximately equal shadow is generated over the entire periphery of the land, so that the mounting state can be accurately inspected. . In addition, since light is irradiated from directly above each chip without using the oblique light as described above, the shadow of a relatively large chip is projected onto an adjacent small chip, making it impossible to detect the position of the small chip. This method can be used to inspect printed circuit boards with high chip mounting density.

In addition, in the present invention, each chip on the board is irradiated with light from the light source from almost directly above, so even if the chips have various shapes, the mounting state of the chips can be clearly detected. Since the shadow of each chip is reliably detected, the positional deviation of the chip can be detected stably, quickly and accurately, regardless of the coloring state of the chip or the coloring state of the surface of the printed circuit board.

[Brief explanation of the drawing]

FIG. 1(a) is an embodiment of the chip positional deviation inspection method on a printed circuit board according to the present invention, and FIG.
) is a perspective view of the detection unit with the hood removed, FIG. 2 is an analysis diagram of chip position deviation detection according to the present invention, FIG.
Figures (a) and (b) respectively show methods for detecting the shadow of a chip on a land according to the prior art. 6 is a rail, 7 is a carrier, 8 is a car, 9 is a printed circuit board, and C is a chip. Figure 1, Figure 2

Claims (1)

[Claims] An annular light source, an imaging camera such that a lens of the imaging camera is located approximately at the center of the light source, and the annular light source and imaging camera are mounted, and the annular light source is at least perpendicular to the printed circuit board. and a carrier means movable in at least one direction on a rail, each chip on a printed circuit board placed on the carrier means receives light from the annular light source. Light is irradiated from almost directly above, and the imaging camera detects a shadow that appears at a predetermined distance between the annular light source and the substrate and covers the entire outer periphery of each chip on the substrate, and determines the predetermined reference coordinates of each chip position. A chip positional deviation inspection method on a printed circuit board, characterized in that a point is compared with a measurement coordinate point detected by the camera, the positional deviation of each chip is detected from the deviation, and the result is displayed.