JPS61293000A - Inspector for printed circuit board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an inspection device for determining the presence or absence of abnormalities in various electrical components attached to a printed circuit board, and particularly relates to inspection equipment for determining whether or not capacitors and IC components are properly attached. The present invention relates to a printed circuit board inspection device that can discriminate by image processing.

"Prior Art" A large number of electrical components such as resistors, capacitors, and IC components are often mounted at high density on printed circuit boards. After mounting, the printed circuit board is inspected for the characteristics of the electrical components and visually inspected by an operator for the installation of these components. Electrical parts found to be defective during inspection will be replaced if necessary. Additionally, electrical components that are found to have been forgotten or inserted backwards will be reinstalled in the correct position on the printed circuit board.

By the way, electrical components (elements) such as coils, resistors, capacitors, etc. mounted on a printed circuit board need to be measured in a state where they are not affected by surrounding electrical components as much as possible. For this purpose, a method called the Gauding method is generally used.

FIG. 12 is for explaining this principle. now,
Assume that the element to be measured is ZX, and other elements ZA and Z exist around it. Operational amplifier 1
The ■terminal of is grounded, and the LO-probe 2 is connected to the e-terminal side and brought into contact with the connection point between the two elements Zx and Z. Further, the connection point between elements ZA and ZB is grounded by a G-probe 3, and the connection point between elements ZA and Zx is connected to a DC or AC power source 5 by an Hl-probe 4.

Under this situation, the e terminal of the operational amplifier 1 becomes virtual ground, so the LO-probe 2 and the Hl-probe 4 have the same potential. Therefore, no current flows through element ZB. Regarding element ZA, even if current flows from power supply 5 to it,
It can be considered that the potential (1) of the HI-probe 4 does not change due to this. As a result of the above, the potential on the output side of the operational amplifier 1 becomes ■. When the feedback resistance is Rr@f, the impedance of the element Zx can be determined by the following equation.

``Problems to be Solved by the Invention'' However, even with this Gauding method, it was virtually impossible to measure bypass capacitors. This is because, as shown in FIG. 13, bypass capacitors are basically electrical components connected in parallel, so it is difficult to electrically separate them during measurement. Of course, for a parallel circuit of a capacitor C and a resistor R as shown in FIG. 14, or a parallel circuit of a resistor R and a coil L as shown in FIG. By doing this, it is possible to perform separate measurements for the real part and the imaginary part. However, in the parallel circuit shown in FIG. 13, even if such phase detection is performed, the elements will be in the same phase, so the elements cannot be separated from each other.

Furthermore, when the IC components are inserted backwards, the IC components 71 to 74 form a parallel circuit between the Vcc-C and ND terminals, as shown in FIG. When inserted backwards, the most noticeable electrical difference is
This occurs between the Vcc and GND terminals, but since it cannot be electrically isolated, it is difficult to detect it by measuring the electrical characteristics of the element.

Therefore, in the past, workers visually inspected printed circuit boards to detect abnormalities that were impossible or difficult to detect by inspecting the characteristics of each electrical component, such as forgetting to attach a capacitor on a printed circuit board or inserting an IC component backwards. I discovered it by doing this. However, such visual inspections have the problem that highly reliable inspection results cannot necessarily be obtained because they depend on the skill and concentration of the operator.

In view of these circumstances, it is an object of the present invention to provide an inspection device that can satisfactorily inspect electrical components mounted on a printed circuit board without visual inspection by an operator.

"Means for Solving Problems" The present invention includes an electrical component measuring means that measures the electrical characteristics of various electrical components such as resistors mounted on a printed circuit board by bringing a probe into contact with them; A circuit board image discriminator that analyzes the image and compares it with a reference image to determine whether or not there is an abnormality in the installation of these electrical components, and analyzes and displays the measurement and determination results of the electrical component measuring means and the circuit board image discriminator. A printed circuit board inspection device is equipped with a measurement result display means.

Here, the measuring operation of the electrical component measuring means of the present invention and the image discriminating operation of the board image discriminating means can be performed temporally in parallel. Such parallel operations are convenient for shortening the inspection time for printed circuit boards.

It is effective for the circuit board image determination means to scan an image of the printed circuit board using, for example, a one-dimensional image sensor and determine the mounting status of the electrical components.

At this time, by suctioning and fixing the printed circuit board to the measurement location using a vacuum pump, it becomes possible to read the image in a state where there are no obstacles on the surface of the circuit board. As already explained, the board image determining means mainly determines abnormalities in the mounting of capacitors and IC components on the printed circuit board. The board image discrimination means includes a calculation means for calculating the difference between an inspection image obtained from the printed circuit board to be inspected and a reference image obtained for the reference printed circuit board, and a calculation means for calculating the difference between the inspection image obtained from the printed circuit board to be inspected and the reference image obtained for the reference printed circuit board, and the calculation means for calculating the difference between the inspection image obtained from the printed circuit board to be inspected and the reference image obtained from the reference printed circuit board, and the calculation means for calculating the difference between the inspection image obtained from the printed circuit board to be inspected and the reference image obtained from the reference printed circuit board. The image area of the power part and I
A masking means for extracting only the image area of the mark indicating the polarity of the C component and masking other image parts, and comparing the output of the masking means with a predetermined value to detect the capacitors and IC components in the unmasked image area. and an abnormality determining means for determining whether or not there is an abnormality in the attachment of the device.

"Example" The present invention will be described in detail below with reference to Examples.

Requirements for the Apparatus FIG. 1 shows the external appearance of the printed circuit board inspection apparatus of this embodiment. A printed circuit board 11 mounted on the device
A jig/fixture 12 is provided for suctioning and fixing by a vacuum pump. A large number of pins are arranged on the top surface of the jig fixture 12.
These pins come into contact with each measurement location on the printed circuit board 11, and resistance values and the like are measured. Above the Jig Fixture 12 is a camera box (scanner).
13 are arranged. The camera box 13 reciprocates above the printed circuit board 11 and reads images with a built-in image sensor.

The scanned images and the measurement results from the above-mentioned bins are processed inside the inspection device to check whether there are any abnormalities in the characteristics of the electrical components,
It is determined whether there is any abnormality in the installation of parts. The determination results etc. are displayed on the CRT 15, 16 or printed by the printer 17. The keyboard 18 is used for inputting various data.

FIG. 2 shows an outline of the in-circuit tester section of this testing device. The in-circuit tester section can be roughly divided into a measurement section and a control section. The measurement part is a jig that fixes the board 11 on which electrical components are mounted.
It was mentioned above that the fixture 12 is provided. A suction tube 22 for the vacuum pump 21 is attached to the jig fixture 12, and a large number of pins 23 come into pressure contact with the bottom surface of the printed circuit board 11 when the pump suctions.

Below the jig fixture 12 is a jig receiver,
24 are arranged. The jig/fixture core 12 is prepared separately for each type of printed circuit board 11, but the jig/receiver 24, which is commonly used as a standard product among these, is equipped with a plurality of connectors 25, and the jig/fixture core 12 is provided separately for each type of printed board 11. Each bin will be connected to the necessary lines connected to the connector 25. jig receiver 2
Further below 4, a large number of relay boards 26 are arranged. Each relay board 26 is connected to a connector 25 via a cable 27. One relay board is 3
2 bins, and if the number of corresponding pins of all connectors is 512, then the relay board 26
A total of 16 sheets are required.

Data selected for each measurement target by the rear board 26 is supplied to the detector board 29 via the measurement bus 28. The detector board 29 performs measurements based on these data and A/D converts the results.

The converted digital data 31 is transferred to the system bus 33 via the first parallel output unit (PIO) 32 in the control unit.
supplied to A CPU (central processing unit) 34, a second parallel input/output section 35, a CRT/printer section 36, and a bank/floppy disk drive (BNK/FDD) 37 are connected to the system bus 33. Here the second
The parallel input/output unit 35 is used to send data to the printer 17 that prints the test results of electrical parts, and to take in data from the keyboard 18 and control box 39 for operating the device.

Further, through line 41, data is transferred to and from an image processing section, which will be described in detail later.

The CRT/printer section 36 displays data on the CRT 16 (FIG. 1). An 80-digit printer 42 can also be attached to this CRT printer section 36 for debugging. The bank floppy disk drive 37 houses a bank memory and a floppy disk drive, and further includes a floppy disk drive 43.
44 can be added.

In contrast, FIG. 3 shows an outline of the image processing section. CPU 51 is connected to line 41 and system bus 5
2, and plays a central role in image processing. Connected to the system bus 52 are a CCD interface section 53, a TV control section 54, a timing control section 55, a filter processing section 56, a difference processing section 57, and three types of image memories 58-60.

The CCD interface section 53 includes a CCD control section 62.
In addition, a scan control section 63 for controlling scanning of the camera box 13 (FIG. 1) is connected.

FIG. 4 schematically shows the structure of the camera box. At the top of the box body 64 of the camera box, there is a
A CCD 65 as a dimensional image sensor is attached. The box body 64 has a strip-shaped opening 66 at its bottom in a direction perpendicular to the drawing (the scanning direction of the CCD 65). At the bottom of the box body 64, four to six halogen lamps 67 are arranged in a row at predetermined intervals in the scanning direction of the CCD 65. The emitted light from these halogen lamps 67 passes through the opening 66 and passes through the printed circuit board 1.
It is designed to be irradiated onto 1. Printed circuit board 11
The reflected light passes through the lens 68 and forms an image on the CCD 65, where photoelectric conversion is performed line by line. A light shielding plate 69 is provided above the halogen lamp 67.

Incidentally, the box body 64 needs to be sub-scanned in order to read the image of the printed circuit board 11. The scan control unit 63 performs control for this purpose. The scan control section 63 is configured to drive the scan motor 71. The driving force of the scanning motor 71 is transmitted to the ball screw 73 via the toothed belt 72, causing it to rotate. The ball screw 73 is a rod-shaped member with a spiral thread carved around its periphery, and is fixed to the box body 64 and engaged with a tapole nut 75 via a ball (not shown).
The box body 64 is moved in the direction of arrow 76 or 77 depending on the direction of rotation of the ball screw 73.

When the box body 75 starts moving in the direction of the arrow 76 (sub-scanning direction), the halogen lamp 67 turns on.
An image of the printed circuit board 11 is captured by the CCD L5. The CCD 6-5 is designed to read a 300 mm scanning lamp with 2048 pixels, and the resolution in the main scanning direction is approximately 6.8 lines/mm. The resolution in the sub-scanning direction is 5 lines/mm. Beaubascri:,
An encoder 78 is attached to the end of 73 to detect the number of revolutions of the ball screw 73 by the scanning motor 71, thereby obtaining positional information in the sub-scanning direction such as the reading start position of the printed circuit board 11. It has become.

Returning to FIG. 3, the explanation will be continued. TV control section 54
This is the part where general video control is performed, and character composition is also performed here. The timing control section 55 is a section that mainly controls various timings around the image memory, and, for example, determines the timing of filter processing, which will be described next. The filter processing section 56 is a circuit section that sets a "window" in order to extract only image regions to be inspected as part of screen calculation processing. The difference processing unit 57 is a circuit portion that compares an image of a printed circuit board to be inspected (hereinafter referred to as an inspection image) and a reference image (hereinafter referred to as a reference image) and calculates the difference between them. The image signal of the inspection image is stored in the inspection image memory 58.
Those of the reference images are respectively stored in the reference image memory 59. The processed image memory 60 is a memory that stores image signals after image processing. These memories 58 to 60 are RA
Depending on the device, for example, the image signal of the reference image may be stored once on a floppy disk so that the data can be saved when the power is cut off.

Image discrimination Figures 5 and 611! J represents the principle of determining whether or not there is an abnormality in the attachment of parts using the printed circuit board inspection apparatus having the above-described configuration. FIG. 5a shows a reference image 81 stored in reference image memory 59. FIG.

The reference image 81 is obtained by scanning a non-defective printed circuit board with no abnormalities using the CCD 65. On the other hand, the figure shows an inspection image 82. For these images 81 and 82, differences in signal levels are determined for each corresponding pixel. In FIG. 6, the difference processing unit 57 is a part that performs this processing. In this way, a difference image 83 is obtained.

The difference processing unit 57 is a part that performs this processing. The difference image 83 is stored in the processed image memory 60 shown in FIG.

Once the difference image 83 is obtained, each window 85 constituting the mask image 84 shown in FIG.

This is to remove images of locations that are not necessary for inspection before the next stage of image processing.

Figure 7 shows the window 85□ to check if the co-denser has been installed incorrectly, and Figure 8 shows the window 85□ to check if the IC part is inserted backwards.
852. Windows 85, 85. in these figures.
It is assumed that images 86 and 87 inserted in the figure for explanation purposes each represent the arrangement of parts in a normal state. In this case, one image 86 represents the pattern of the capacitor 88 and the other image 87 represents the pattern of the IC component 88.
Mark indicating the polarity of 9 (hereinafter referred to as polarity mark) 91
It represents the surrounding pattern. Window 85. ．． 852, ideally no image should appear in the corresponding image area after processing if the electronic component to be inspected is correctly installed. On the other hand, if the capacitor 88 is forgotten to be installed or the IC component 89 is inserted backwards, the processed image will be almost the same as the image 86 or 87 shown in FIG. 7 or 8. It will appear as part of image 92 (Figure 5d).

When the mask is set as explained above, if there is no abnormality in the installation of the electrical components corresponding to each window, the images of those windows will ideally be in a clear state. However, in reality, some noise components will appear in the difference image due to positional errors in the attachment of electrical components, etc. Therefore, the filter processing unit 56 removes the noise components, resulting in a final filtered image 94 (FIG. 6).
shall be.

The level of the image signal in the filtered image 94 is checked in association with the position of each window, and if the level is higher than the reference value, it is determined that there is an abnormality in the installation of the electrical component. However, for example, the capacitor 88 shown in FIG.
As in the case where a resistor of almost the same shape is attached instead of the electric component, it may not be possible to determine an abnormality in the attachment of the electrical component only by the determination made by the image processing unit.

Therefore, the inspection device of this embodiment uses the results of characteristic inspection of electrical components to determine installation abnormalities and component abnormalities.
It is designed to be displayed.

Measuring electrical components FIG. 9 shows the principle of measuring electrical parts.

When a start button (not shown) is pressed to start the inspection, the vacuum pump 21 shown in FIG. 2 starts operating, and the printed circuit board 11 is sucked downward. At this time, the guide board 97 covered the tip of the pin 23 for protection.
is also sucked downward. As a result, the tip of the pin 23 is exposed and pressed against a predetermined location on the printed circuit board 11. Pin board 9 placed below guide board 97
8 is a jig/fixture chair 12 along with a guide board 97
The bottle holder is configured to hold the pin 23 by a tool 99 via a built-in spring.

The bottle holder 99 is connected to a connector 101 on the jig/fixture side. This connector 101 is a jig
By being connected to the connector 25 on the receiver side, each pin 23 is connected to the corresponding pin node 102 of the relay board 26.

The bin node 102 and the measuring bus 103 are selectively connected within the relay machine IJ hook 04 depending on the object to be measured. For example, when measuring the resistance 105 in the same figure, as explained in FIG.
5 line 103A is connected to the bin node 102-1 on one end side of the resistor 105. Further, the line 103B connected to the e terminal of the operational amplifier l is connected to the bin node 102-N at the other end of the resistor 105. The operational amplifier l is housed in the detector board 29 together with the A/D converter 108, and the measurement data is A/D converted and then supplied to the control section shown in FIG. The control section compares the measured data with reference data (reference resistance value in this case) manually entered in advance from the keyboard 18 (FIG. 2) to find an error. If this error falls between the upper and lower limits set in advance for the electrical component, the component is judged to be acceptable; if it is not, it is judged to be rejected.

Now, the above-described external inspection of the printed circuit board 11 and the electrical inspection of the individual electrical components are performed in parallel.

For example, the printed circuit board 11 to be inspected is 130 mm.
Assume that the size is 230 mm x 230 mm, and there are 40 windows and 220
If the test is performed using 2 pins, each of these tests will be completed in about 5 seconds or 8 seconds. That is, the entire test is completed in 10 seconds or less. The test results are displayed on the CRT 15 or 16 and printed out if necessary.

FIG. 10 shows an example of a CRT display screen in the apparatus of this embodiment. An image 111 of the printed circuit board to be inspected is directly displayed on the CRT from the inspection image memory 58 (see FIG. 3). Since symbols such as resistance are printed on the surface of the printed circuit board, these will also be displayed as they are. If there is an abnormality in the electrical component mounted on the printed circuit board or if there is an error in the installation of the component, an error mark 112 is displayed on the display screen at the location of the component and this blinks. In FIG. 10, error marks 112 are blinking at two locations: IC component IC5 and resistor R2. The printed circuit board inspection operator can immediately determine whether the IC component IC5 is inserted backwards from the image. Furthermore, regarding the resistor R2, it can be easily determined whether a component has been forgotten to be attached.

In other words, in the past, for example, as shown in Figure 11, the display screen was virtually regarded as a printed circuit board, and the numerical values of the electrical components in which the error occurred were displayed by roughly dividing the display screen vertically and horizontally. It was difficult to establish a strict correspondence between the two locations, and it took time to confirm the location. The inspection device of this embodiment can not only solve such problems, but also make it possible to confirm abnormalities in component attachment through visual display.

In the embodiment described above, one image sensor is used as the image sensor.
Although a dimensional CCD is used, it is also possible to use other image pickup devices or two-dimensional image sensors to read images.

Furthermore, although a halogen lamp was used to illuminate the printed circuit board, it is also possible to use a fluorescent lamp for high-frequency lighting.

In this case, the lighting frequency of fluorescent lights, etc. is 1KH2 to 10KHz.
degree is preferred. Further, in the embodiment, an abnormality in the installation of an electrical component is detected by, for example, a polarity mark on an IC component, but it can also be detected by reading and identifying characters or symbols printed on an IC component or the like.

"Effects of the Invention" As described above, according to the present invention, since the inspection of electrical components mounted on a printed circuit board is performed in combination with the inspection by image processing, highly reliable inspection results can be obtained in a short time.

[Brief explanation of the drawing]

Figures 1 to 1O are for explaining one embodiment of the present invention, of which Figure 1 is a perspective view of a printed circuit board inspection device, and Figure 2 is a schematic configuration diagram of an in-circuit tester section. , Fig. 3 is a schematic configuration diagram of the image processing unit, Fig. 4 is a partial cross-sectional view of the camera box, Fig. 5 is an explanatory diagram showing the progress of image processing, and Fig. 6 is a block diagram showing the flow of image processing. , 7th
Figure 8 is an explanatory diagram showing the window set for capacitors, Figure 8 is an explanatory diagram showing the window set for IC components, Figure 9 is a principle diagram showing the measurement principle of electrical components, and Figure 10 is an illustration of the inspection results. A plan view showing an example of a display screen, Fig. 11 a plan view showing an example of a conventional display screen, Fig. 12 a circuit diagram showing the principle of measurement of coils, resistors, capacitors, and capacitors, and Fig. 13 a parallel diagram of bypass capacitors. A circuit diagram showing the connection state, Fig. 14 is a measurement circuit configuration diagram for a parallel circuit of a resistor and a capacitor, Fig. 15 is a measurement circuit configuration diagram for a parallel circuit of a resistor and a coil, and Fig. 16 is an IC component installation situation. It is a circuit diagram showing an example. ■...Operation amplifier, 11...Printed circuit board, 15.16...CRT. 21...Vacuum pump, 23...Bin (probe), 34.51...CPU. 56...Filter processing unit, 57...Difference processing unit, 58...Inspection image memory, 59...Reference image memory, 60... - Processing image memory, 65...CCD. 85... Window, 88... Capacitor, 89... IC parts, 105... Resistor. Applicant Atec Co., Ltd. Agent Patent Attorney Umeo Yamauchi Fig. 1 Fig. 6 3rd session (image processing) Fig. 7 Fig. 8 Teguter 7 units, uncle 29 Fig. 13 Fig. 16

Claims (1)

[Scope of Claims] 1. Electrical component measuring means for measuring the electrical characteristics of various electrical components such as resistors mounted on a printed circuit board by contacting them with a probe, and analyzing an image of the printed circuit board for reference. a circuit board image discriminating means for determining whether there is an abnormality in the installation of the electrical component by comparing the image with an image of A printed circuit board inspection device comprising: 2. The printed circuit board inspection apparatus according to claim 1, wherein the measuring operation of the electrical component measuring means and the image discriminating operation of the board image discriminating means are performed in parallel in time. 3. The printed circuit board inspection apparatus according to claim 1, wherein the circuit board image discrimination means scans the image of the printed circuit board using a one-dimensional image sensor. 4. The printed circuit board inspection apparatus according to claim 1, wherein the printed circuit board is sucked and fixed at a measurement location by a vacuum pump. 5. The printed circuit board inspection apparatus according to claim 1, wherein the circuit board image determining means determines abnormalities in the attachment of capacitors and IC components on the printed circuit board. 6. The board image discrimination means includes a calculation means for calculating the difference between an inspection image obtained from the printed circuit board to be inspected and a reference image obtained for the reference printed circuit board, and a calculation means for calculating the difference between the inspection image obtained from the printed circuit board to be inspected and the reference image obtained for the reference printed circuit board, and the arrangement of the capacitors in the difference image as a result of the calculation. masking means for extracting only the image area of the part to be masked and the image area of the mark indicating the polarity of the IC component and masking other image parts; 6. The printed circuit board inspection apparatus according to claim 5, further comprising an abnormality determining means for determining whether or not there is an abnormality in the attachment of these capacitors and IC components in the image area.