JPH0210252A - Board checking apparatus - Google Patents

Abstract

PURPOSE:To judge the quality of the mounting state of parts simply by providing a means for measuring the heights of parts mounted on a board, and providing a circuit for computing the mean square errors for every reference height of the part and the mask of measured height data. CONSTITUTION:A three-dimensional coordinate measuring part 3 is composed of a distance sensor part 4 and a height computing circuit 5 using the data of the sensor part 4. The height of a part 2 which is mounted on a printed board 1 and the height of the surface are measured. The obtained height is corrected to the height from the board 1. The result is introduced into a square-error computing circuit 7. The square error of the value of part 2 in a reference-height-data storage memory A 6 and the height data which are measured in the measuring part 3 is computed. The values are accumulated and added for every mask in an accumulating and adding circuit 11 in reference with the master data of a master-data storage memory B 10. The mean value of the squaring computation in the mask is compute din an average computing circuit 12. IN a comparing and judging circuit 14, the mean square error is compared with the reference threshold value for every mask for judging the pass or fail in a reference-threshold-value storage memory C 13. The quality is judged based on whether the mean square error is larger or smaller than said value.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a board inspection device for inspecting defects such as misalignment and lifting of components mounted on a printed circuit board.

BACKGROUND OF THE INVENTION Conventionally, human visual inspection has been relied upon to inspect components mounted on printed circuit boards for defects such as misalignment, missing parts, and floating parts. However, as products become smaller and lighter, components on printed circuit boards are also becoming smaller and more densely packaged.

Under these circumstances, it was almost difficult for humans to continue inspecting the mounting conditions of extremely detailed components for long periods of time while maintaining high inspection accuracy.

Recently, there has been a strong desire to automate inspections, and devices have been proposed that inspect the positional deviation of parts from two-dimensional images of the parts.

A conventional general inspection device is shown in FIG.

In FIG. 4, 31 is a printed circuit board, 32 is a component mounted on the printed circuit board 31, 33 is a video camera that images these components, and 34 is a video signal from the video camera 33 that is A/D converted and stored in an image memory. image capture circuit to store;
Reference numeral 35 denotes an edge detection circuit that detects the edge of a component from the captured image, 36 a corner detection circuit that detects the corner of the component from edge information, and 37 reference data that stores the reference coordinate values of the corners of each component. The storage memory J, 38, is a deviation amount calculation circuit that calculates the amount of deviation of the component from the detected corner coordinates and the reference coordinate value, and 39 is the allowable deviation amount storage memo IJ H140 in which the allowable deviation amount of the component is stored. This is a comparison/judgment circuit that compares the calculated deviation amount and the allowable deviation amount to judge whether the mounting state of the component is good or bad.

The operation will be explained below. A component 32 mounted on a printed circuit board 31 is imaged by a video camera 33, and the video signal is A/D converted by an image capture circuit 34 and captured into an image memory. Using the image, the edge detection circuit 35 detects the edges of the component 32, and from the edge information, the corner detection circuit 3
6, the coordinate values of the corners of the component 32 are detected. The detected coordinate values of each corner are compared with the standard coordinate values of the component stored in the memo +) J37, and the deviation calculation circuit 38
Calculate the amount of deviation between the two. Then, the comparison/judgment circuit 40 compares the calculated deviation amount of the component from the standard value and the deviation tolerance stored in the memo 1JH39, and detects the mounting condition such as deviation of the component or missing parts. Judging whether it is good or bad.

Problems to be Solved by the Invention However, in the inspection method shown in the conventional example, since two-dimensional information is used by imaging the component with a video camera, for example, if the component is soldered, it may be the cause of a defect. In order to solve the above-mentioned problems, the present invention solves the above-mentioned problems, such as when the IC is mounted with the entire part lifted up or where the feet of the IC are partially lifted up.
A height measuring means for measuring the height of a component mounted on a board, a first memory storing a reference height of the component, and a square error for calculating a square error between the reference height and measurement data. a calculation circuit, a second memory that stores mask data, an accumulative addition circuit that cumulatively adds squared errors for each mask, an average calculation circuit that calculates the average value of squared errors for each mask, and standards for determining pass/fail. It is composed of a third memory that stores a threshold value, and a comparison/judgment circuit that compares the average value of the square error for each mask with a reference threshold value and determines whether the mounting state of the components is good or bad.

Effects With the above configuration, the present invention quantifies the degree of deviation from a reference value for each mask using the average value of the squared error based on the height information of the components mounted on the board, and In addition to inspecting for misalignment (e.g.), defects such as three-dimensional parts lifting can also be easily inspected.

Embodiment FIG. 1 is a block diagram showing an embodiment of the substrate inspection apparatus of the present invention. In FIG. 1, 1 is a printed circuit board, 2 is a component mounted on the printed circuit board 1, 3 is a three-dimensional coordinate measuring unit that measures the height of the printed circuit board 1 and the component 2;
4 is a distance sensor section, 5 is a height calculation circuit, 6 is a memory A in which reference height data of component 2 is stored, 7 is a square error calculation circuit, 8 is a subtraction circuit, 9 is a square calculation circuit, 10 is a memory B corresponding to the same size as the printed circuit board 1, and a mask is set for each component in the memory B.

11 is a cumulative addition circuit, 12 is an average calculation circuit, and 13 is a memory C in which reference threshold values for each mask are stored. 14 is a comparison/judgment circuit.

The operation will be explained below.

The height of the component 2 mounted on the printed circuit board 1 and the height of the surface of the printed circuit board 1 are measured by a three-dimensional coordinate measuring section 3. The three-dimensional coordinate measurement section 3 is composed of a distance sensor section 4 and a height calculation circuit 5 that calculates the height using information from the distance sensor section 4. The principle of coordinate measurement uses the principle of triangulation using a laser and a light receiving element. The obtained height information is corrected to the height of the printed circuit board 1 and output to the square error calculation circuit 7.

The square error calculation circuit 7 calculates the square error between the value from the memory 6 in which the height data of the reference component 2 is stored and the height data measured by the three-dimensional coordinate measuring section 3. That is, the difference between both data is determined by the subtraction circuit 8, and the square of the difference is calculated at high speed by the square calculation circuit 9. Then, the calculated squared error is cumulatively added for each mask in the cumulative addition circuit 11 with reference to the mask data stored in the memory 10, and the cumulative addition value is divided by the number of cumulative additions in the average calculation circuit 12. , calculate the mean value of the squared error in the mask.

Finally, the comparison/determination circuit 14 compares the mean squared error for each mask, which is the output of the average calculation circuit 12, with the reference threshold value for each mask for pass/fail determination stored in the memory 13, and calculates the average Bad/good is determined based on whether the squared error is larger or smaller than a reference threshold value.

In the above operation, the mask data in the memory 10 and the reference threshold value in the memory 13 will be explained in more detail. The mask data in the memory 10 has the same number of data as the height data on the printed circuit board 1, and has a one-to-one correspondence in position (address) on the printed circuit board 1.The contents of the mask data are as follows. Each area of each mask is filled with a unique number for each mask. Therefore, the cumulative addition circuit 11 is provided with a buffer A that performs cumulative addition for each mask unique number, and cumulatively adds the square error between the reference height and the measured height within each mask area to the buffer A. Then, the average calculation circuit 12 divides the cumulative addition value of the squared errors in the buffer A by the number of cumulative additions, calculates the average squared error in the mask, and stores it in the buffer B.

Buffer A (? Suffu number) - E (Reference height [
address] - measurement height [address])'...
・・・■・・・・・・■ In other words, the square error calculation circuit 7 performs the calculation as shown in the first equation.
The calculation shown in the second equation is performed by the average calculation circuit 12.

FIG. 2 shows the relationship between specific mask data and component positional deviation. FIG. 2 fa) shows a non-defective product, and FIG. 2b shows a defective product. The dashed line frame 21 indicates the normal placement position of the rectangular parallelepiped-shaped component when there is no positional shift, and within that frame, four masks P15. Q16. R17°S18 is set. Solid line frames 19 and 20 indicate the two-dimensional positions of the actually placed parts'. In this embodiment, the mask P15. Q16. Eigenvalues of R17 and S18 (
Mask number) is 10. 11.12. 13
Therefore, as mask data, for example, mask P1
All addresses within the area of 5 (within the diagonal line) are "10"
” is stored.

Based on such mask data, the mean squared error within the mask between the reference data and measurement data of the component is calculated to determine whether the mounting state of the component is good or bad. For example, in the case of Fig. 2(a), the deviation of the solid line frame 19 is small and is within the deviation tolerance, so each mask is contained within the solid line frame 19, and within the mean square within each mask. This is the cumulative number of squared errors. On the other hand, in the case of Fig. 2 fb), the solid line frame 20
Because the deviation is large, the mask R17 is completely aligned with the solid line frame 20.
It has gone outside. Therefore, there is a mean square error within mask R17.

Figure 3 shows this in an easy-to-understand graph.

In FIG. 3, the shaded bar graph represents the mean squared error within the mask. D22 corresponds to the case of a non-defective product in FIG. 2fa), and F23 corresponds to the case where a positional shift occurs in FIG. 2(b). Also, although there is no major positional shift, the overall placement is floating,
E24 corresponds to the case where it is arranged at an angle. Therefore, by setting the standard threshold value for each mask for pass/fail judgment (in the case of this figure 2, the standard threshold value for mask R17) to the value of G25, two-dimensional positional deviation exceeding the allowable value can be avoided. In addition, defects such as lifting and tilting of three-dimensional parts can also be determined using the same configuration.

If the mask size (shape) has changed or there are parts of the measurement data inside the mask where the 3D coordinates cannot be measured due to the influence of the part shape, etc., the number of data used for judgment inside the mask will change. However, in the configuration of this embodiment, the square error between the reference data and the measured data is averaged by the number of valid data for each mask, so it is necessary to change the reference threshold value for pass/fail judgment as the number of data increases or decreases. Therefore, the quality of the component mounting state can always be determined using the same criteria.

As described above, in this embodiment, it is now possible to inspect three-dimensional lifting or tilting of parts, partial lifting of IC legs, etc., which could not be inspected by comparing two-dimensional position information. By calculating the average of the squared errors between the reference value and the measured data based on appropriate mask data, it is possible to determine the quality of the mounting state of the component very easily.

Effects of the Invention As described above, according to the present invention, there is provided a height measuring means for measuring the height of a component mounted on a board, and a mean square of the reference height of the component and the measured height data for each mask. A circuit that calculates the error and a comparison circuit that compares the mean squared error and standard threshold for each mask to determine whether the mounting state of the components is good or bad.
With a relatively simple circuit configuration consisting of a judgment circuit and a judgment circuit, it is possible to inspect for defects related to three-dimensional float inclination, which could not be inspected using two-dimensional position information, without relying on human visual inspection. This can bring great benefits such as automating inspections and improving work efficiency.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a board inspection apparatus according to an embodiment of the present invention, Fig. 2 (al, (bl) is a relationship diagram between the mask and positional deviation, and Fig. 3 is a diagram showing the relationship between the mask and the positional deviation of the mean square error in the mask. Fig. 4 is a block diagram of a conventional board inspection device. 1... Printed circuit board, 2... Components, 3... Three-dimensional coordinate measuring section, 6... Standard Height storage memory, 7... Square error calculation circuit, 10... Mask data storage memory,
11... Cumulative addition circuit, 12... Average calculation circuit, 1
3... Reference threshold value storage memory, 14... Comparison/judgment circuit. Figure 2 (L:A) / Button diagram

Claims (1)

[Claims] a height measuring means for measuring the height of a board and a component mounted on the board; a first memory storing a reference height of the component; and height data from the height measuring means. a square error calculation circuit that calculates the square error between the reference height data and the reference height data from the first memory; a second memory that stores the mask data set on the substrate; an accumulative addition circuit that cumulatively adds the squared errors for each mask from the second memory; an average calculation circuit that calculates the average value of the squared errors for each mask; and a reference threshold for pass/fail judgment. a third memory, for each mask, a comparison that compares the mean squared error value calculated by the average calculation circuit with a reference threshold value from the third memory, and determines whether the mounting state of the component is good or bad; A board inspection device comprising a determination circuit.