JPH04268445A - Mounted substrate inspector - Google Patents

Abstract

PURPOSE:To realize shortening of inspection time necessary for automation of a visual inspection process in a production line by scanning the entire surface of a printed circuit board by a laser light to introduce reflected scattered light to a position detecting means with a reflection mirror. CONSTITUTION:A printed circuit board 101 is scanned two-dimensionally over the entire surface thereof by a laser light 106 being moved with a conveying means 103. The scattered light reflected from the circuit board 101 is reflected with a reflection mirror 110 to be focused onto a position detecting element 112 through a condenser lens 111. An image computation processing means 114 performs a computation to convert a photocurrent signal 113 inputted at a timing of a synchronous signal to a height data and a brightness data of the circuit board 101, a part 102 mounted on the circuit board and a soldered part thereof and the results are outputted to a brightness judgment processing means 115 and a height judgment processing means 116. The means 115 calculates a ratio between bright and dark parts of the soldered part by a mask data from a mask memory means 117 to judge the propriety of the soldered part. The judgment results are outputted to the means 116 and a comprehensive judgment processing means 118.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mounted board inspection apparatus for inspecting solder mounting defects on a printed circuit board on which components are mounted.

0002

2. Description of the Related Art Conventionally, inspection of soldered parts on printed circuit boards has relied on visual inspection by humans. However, as products become smaller and lighter, components on printed circuit boards are also becoming smaller and more densely packaged. Under these circumstances, it has become difficult for humans to perform visual inspections, and automation of inspections has been strongly desired. As one method, patent application No. 01-03304
No. 0 proposes measuring the brightness data of the soldered part and determining the quality of the soldered part based on the ratio of bright and dark parts, but the determination threshold is affected by the positional deviation of the component. Sometimes. As another method, Japanese Patent Application No. 02-025391 discloses that the height data of the soldered part is measured, the variation of the height data on the board-soldered part-component is determined, and the height data and the It is proposed to judge the quality of soldered parts using a correlation that uses changes in height data as two variables.

[0003] A conventional mounting board inspection apparatus will be explained below. FIG. 6 shows a block diagram of a correlation calculation means of a conventional mounted board inspection apparatus. In Figure 6, 6
01 is calculated height data, 602 is a difference calculation circuit that calculates the difference in height data, 603 and 604 are comparison circuits A and B, 605 is a difference threshold storage means, 606 is a height threshold storage means, 607 and 608 are counters C and D.

[0004] The operation of the mounted board inspection apparatus constructed as described above will be explained below.

In the difference calculation circuit 602, the mask data 6
Height data 6 extracted from image memory based on 09
The amount of change (difference value) of 01 is calculated and the difference value is output to the comparison circuit A603. The difference is calculated in the direction in which the height data goes from the board to the soldering parts and components.

In the comparison circuit A603, the difference calculation circuit 60
The difference value calculated in step 2 is compared with the threshold value from the difference threshold value storage means 605, and if the difference value is within the range determined by the threshold value, a signal of "1" is output to the counter C607 and the counter D608, and the range is If outside, a signal of "0" is output. On the other hand, the comparison circuit B604 compares the height data 601 with the threshold value from the height threshold storage means 606, and if the height data is within the range determined by the threshold value, the counter C607
A signal of "1" is output to the counter D608, and a signal of "0" is output if it is outside the range.

The counter C607 receives mask data 609.
Comparator circuits A603 and B60 for each mask based on
Counts up only when outputs from 4 are both "1". Further, the counter D608 analyzes for each mask based on the mask data 609, if the outputs from the comparator circuits A603 and B604 are both other than "1", that is, if expressed as a set of signals (A, B), (1, 0 ), (0, 1), (0,
0), the count is increased.

[0008] Through the above operations, the outputs of the respective incremented counters are the height data (
It shows the distribution numbers of data of good areas and bad areas in the correlation diagram between Z) and the difference value (ΔZ), and from these distribution numbers, it is possible to inspect the quality of the soldering state of the components.

A more specific example will be explained with reference to FIG. That is, FIG. 7 is a diagram showing the soldering state of a non-defective product.
(a) is a view of the soldered part of the component viewed from above, and Figure 7 (b)
) shows a cross-sectional view, and FIG. 7(c) shows a correlation diagram between height data and height difference values. A substrate 70 as shown in FIG. 7(b)
If the solder portion 702 of the component 703 mounted on the substrate 1 is in good condition, a correlation diagram between the height data (Z) and the difference value (dZ) shown in FIG. 7(c) is obtained. That is, Z1 (70
4) is the average height of the board, Z2 (705) is the average height on the component, and the measured data is indicated by an x mark. Further, the difference thresholds are set to O (706) and A1 (707), and the height thresholds are set to A2 (708) and A3 (709). In the correlation diagram of FIG. 7(c), since the soldering condition is good, the measurement data of the soldered part is distributed between the respective heights of the board and the component, and the difference value is also a positive value, A1 (
707) is distributed in the region (good product region) shown by S1 (710), which is not very large.

Therefore, in the comparison circuit A that compares the difference values, since data enters between O (706) and A1 (707) indicated by the difference threshold, a signal of "1" is output for each data, and the comparison circuit outputs a signal of "1" for each data. In B, since the height data is distributed between A2 (708) and (A3) 709 indicated by the height threshold, a signal of "1" is output for each data, and the value of the counter D is in the area S2 ( Since the data is not distributed in S3 (711) and S3 (712), it becomes zero, and it is determined that the soldered part is good.

It should be noted that the range indicated by the double arrow 713 in FIG. 7(b) indicates the range of mask data from the mask storage means set in the soldering part, and is a view from above. As shown in 7(a), a board 701, a solder part 702
, a mask 714 (shaded area) is set on the component 703,
Height data only within this mask is used for calculations.

0012

[Problems to be Solved by the Invention] However, in the above conventional configuration, after measuring the height data of the solder part, the difference between the height data is calculated, and the height data and the height data are calculated. Day
The problem is that it takes a very long time to determine the quality of the solder parts by determining the correlation diagram of the difference between the data and the quality of the solder part from that correlation diagram. It also had the problem of becoming an obstacle to its promotion.

The present invention solves the above-mentioned problems of the prior art, and provides a mounted board inspection device that realizes shortening of inspection time, which is essential for automating the visual inspection process on a production line by a machine. With the goal.

[0014]

[Means for Solving the Problems] In order to achieve this object, the present invention provides a transport means for moving a printed circuit board on which components are mounted, and a laser beam from a laser light source to a polygon mirror and an fθ A laser beam scanning means scans the printed circuit board with a lens, and the scattered light reflected from the printed circuit board by scanning the laser beam is connected to the printed circuit board and fθ.
Scattered light reflecting means for reflecting by a reflecting mirror provided between lenses and reflecting through an fθ lens and a polygon mirror;
A light amount detection means that further focuses the scattered light from the scattered light reflection means onto a position detection element using a condensing lens and outputs a photocurrent signal, and a light amount detection means that outputs a photocurrent signal from the light amount detection means and is mounted on a printed circuit board or a printed circuit board. image calculation processing means for calculating brightness data and height data of the soldered parts and the soldered parts;
A mask storage means for storing mask data for applying a plurality of masks of predetermined sizes to the soldered part positions of the mounted components, and brightness data in the mask data from the mask storage means are used. A brightness determination processing means for determining the quality of the soldering state; a height determination processing means for determining the quality of the soldering state using height data in the mask data from the mask storage means; and a brightness determination processing unit. and a comprehensive judgment processing means for comprehensively judging whether the soldering state of the components on the printed circuit board is good or bad using the values calculated by the means and the height judgment processing means, and the judgment result of the brightness judgment processing means is good. In this case, the overall judgment processing means determines the quality, and when the judgment result of the brightness judgment processing means is bad, the overall judgment processing means judges the quality based on the quality of the judgment result of the height judgment processing means. have.

[0015]

[Operation] With the above configuration, the present invention scans the entire surface of a printed circuit board on which components are mounted using a laser beam, and guides the scattered light obtained by reflection from the printed circuit board to the position detection means using a reflecting mirror. The focal position of the scattered light on the position detection element, which changes according to the unevenness of the surface, is detected using a photocurrent signal, and the brightness data of the parts and soldered parts mounted on the printed circuit board is obtained from the photocurrent signal by image processing means. and calculate height data.

The calculated brightness data and height data are calculated only in the mask data from the mask storage means by the brightness judgment processing means and the height judgment processing means, respectively, and if the judgment result of the brightness judgment processing means is good, The overall judgment processing means determines the quality, and if the judgment result of the brightness judgment processing means is poor, the general judgment processing means judges the quality based on the quality of the judgment result of the height judgment processing means. This determination operation using both brightness data and height data can shorten the processing time until comprehensive determination without reducing the reliability of determination.

[0017]

[Embodiment] (Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a mounting board inspection apparatus according to an embodiment of the present invention. In Figure 1, 10
1 is a printed circuit board, 102 is a component mounted on the printed circuit board 101, 103 is a transport means for moving the printed circuit board 101, and 104 is an arrow indicating the direction of movement thereof. 105 is a laser light source, 106 is a laser beam from the laser light source 105, 107 is a polygon mirror, 108 is a reflecting mirror that guides the laser beam to the polygon mirror 107, 109 is f
The θ lens 110 is a reflecting mirror. 111 is a condenser lens, 112 is a position detection element, and 113 is a position detection element 1.
12, 114 is the photocurrent signal 113
115 is a brightness determination processing means; 115 is a brightness determination processing means;
6 is a height determination processing means, 117 is a mask storage means, 11
8 is a comprehensive judgment processing means.

The operation of the mounted board inspection apparatus constructed as described above will be explained below.

While the printed circuit board 101 on which the component 102 is mounted is moved in the direction of the arrow 104 by the conveying means 103, the laser beam 106 from the laser light source 105 is reflected into the rotating polygon using three reflecting mirrors 108. The polygon mirror 107 and the fθ lens 10
9, a laser beam 106 is vertically irradiated onto the printed circuit board 101. Thereby, the laser beam 106 is two-dimensionally scanned over the entire surface of the printed circuit board 101.

Scattered light reflected from the printed circuit board 101 by the scanning of the laser beam 106 is reflected by a reflecting mirror 110 provided between the printed circuit board 101 which is the object to be inspected and the f.theta. lens 109. The light is focused on the position detection element 112 through the polygon mirror 107 and the condenser lens 111. A photocurrent signal 113 from the position detection element 112 is input to an image calculation processing means 114.

The image calculation processing means 114 converts the photocurrent signal 113 input at the timing of the synchronization signal into the printed circuit board 101 or the component 10 mounted on the printed circuit board 101.
2 and the soldered portion of component 102 into height data and brightness data, and outputs the brightness data and height data to brightness determination processing means 115 and height determination processing means 116, respectively.

The brightness determination processing means 115 uses the brightness data of the soldered part extracted by the mask data from the mask storage means 117 to calculate the ratio of the bright part to the dark part of the soldered part. determine the quality of the
The determination result is output to the height determination processing means 116 and the comprehensive determination processing means 118.

Further, the height determination processing means 116 uses the height data of the soldering part extracted from the mask data from the mask storage means 117 to determine the amount of change in the height data between the board, the solder part, and the component. is determined, the quality of the soldered portion is determined using a correlation using the height data and the change in height data as two variables, and the determination result is output to the comprehensive determination processing means 118. However, this height determination processing means 116
The determination process is continued only when the determination result from the brightness determination processing means 115 which is being performed in parallel is bad, and is interrupted when the determination result from the brightness determination processing means 115 is good.
will be reset.

Finally, in the comprehensive judgment processing means 118, if the judgment result from the brightness judgment processing means 115 is good, the general judgment is determined to be good without waiting for the judgment result from the height judgment processing means 116, and the brightness judgment processing means 115 If the determination result from the height determination processing means 116 is poor, a comprehensive determination is made based on the quality of the determination result by the height determination processing means 116.

By repeating and sequentially performing the following operations, the entire surface of the printed circuit board 101 can be inspected. This series of operations must be performed in synchronization with an appropriate signal, but in this embodiment, the polygon mirror 107
Synchronization was achieved using a synchronization signal that matched the rotation of the

[0027] With this configuration, height measurement can be performed at higher speed and with higher precision than in a configuration in which spot scanning is performed using a laser beam using means such as a galvanometer mirror.

Next, the image calculation processing means 114 will be explained in more detail with reference to FIG. Image calculation processing means 1
14, as shown in FIG. 2, the photocurrent signal 113 from the position detection element 112 is converted into a digital signal by the A/D converter 201 and input to the position calculation circuit 202. In this embodiment, the position detection element is a PSD [Position-Sensitive Detector (Position-Sensitive Detector)].
sitive Detectors (semiconductor position detection elements)], and the incident position of the PSD is
An element is used in which the current flowing through the electrodes at both ends of the element is inversely proportional to the distance between each electrode. In the position calculation circuit 202, the currents I1 and I from both electrodes are converted into digital signals.
2, the height data is calculated using equation (1). Furthermore, K
is a coefficient for normalization.

Height data=K・(I1−I2)/(I1+I
2) --------(1) The height data obtained by the position calculation circuit 202 is temporarily stored in the height data storage memory 20.
3.

On the other hand, the brightness data is based on the current I from both electrodes.
1 and I2 using equation (2), the brightness calculation circuit 204
Calculate with.

Luminance data=I1+I2
--------(2)
The brightness data obtained by the brightness calculation circuit 204 is temporarily stored in the brightness data storage memory 205.

Next, the brightness determination processing means 115 will be explained in more detail with reference to FIGS. 3 and 4.

The brightness determination processing means 115 receives the brightness data 301 from the image calculation processing means 114, as shown in FIG.
Binarization means 302 for binarizing, mask storage means 117
Total counter 3 to calculate the total area in the mask data from
03, a 0 counter 304 that calculates the area of 0 in the mask data of the binary signal, a divider 305 that calculates the area ratio of 1 and 0 in the mask, and a threshold for determining the quality of soldering. It is composed of a threshold value storage means 306E for storing and a comparator 307 for comparing the result of the divider 305 and the threshold value from the threshold value storage means E306.

The operation will be explained below. The brightness data 301 from the image calculation processing means 114 is binarized by the binarization means 302 using an arbitrary threshold value, and a binarized signal is output. Then, according to the mask data from the mask storage means 117, the total counter 303 counts all the binary signals in the mask, and the 0 counter 304 counts only when the signal is 0 among the binary signals in the mask. ing. divider 30
5 calculates the ratio between the output of all counters 303 and the output of 0 counter 304, and comparator 307 calculates the ratio between the output of all counters 303 and the output of 0 counter 304, and the comparator 307 calculates the ratio of the area ratio value from the divider 305 and the threshold value storage means E306 in which the threshold value for determining the quality of the solder part is stored. The quality of the soldered part is determined by comparing the value with the value of height determination processing means 1.
16 and output to comprehensive judgment processing means 118.

The method for determining the quality of the soldered portion will be explained in more detail with reference to FIG. FIGS. 4A and 4B show a side view and a plan view of a printed circuit board 401 with a component 402 soldered thereon. Irradiation light 403 {(1), (2), (3)} irradiated onto the printed circuit board 401 becomes reflected light 404 from the component 402 or the solder surface, and is reflected in the normal direction of the printed circuit board 401 (as shown in the figure). The light is focused on a position detection element installed in the upper direction) and converted into a luminance signal.

In particular, the solder portion 405 and the electrode portion 406 form mirror surfaces and are characterized by specular reflection. In FIG. 4A, irradiation light 403 {(1), (2), (3)} is irradiated onto a land 407, an electrode portion 406, and a solder fillet 405, respectively, and each reflected light 404 {(1)
)', (2)', (3)'} are reflected. At this time, (1)' and (2)' of the reflected light 404 are reflected to the position detection element side by a part of the flat electrode portion 406 and land 407, and are converted into a brightness signal with a high brightness level. Irradiation light 4 irradiated onto solder fillet 405 that is not flat
03(3) has the characteristic that it is specularly reflected on the solder fillet 405 and does not return to the position detection element side as reflected light 404 (3)'. Looking at this as a luminance signal, Figure 4
The electrode portion 406 and land 407 are flat as shown in (b).
A part becomes a bright part 408, and the solder fillet 40
An angled portion as shown in 5 becomes a dark portion 409. For such characteristics of the luminance signal around the soldered portion, a mask A410 (indicated by a broken line) as shown in FIG. 4(b) is set on the land 407 with an arbitrary size. This mask A4
10, 1 (bright part 408) and 0 (dark part 40) of the binary signal generated by binarizing the luminance signal at an arbitrary luminance level.
9) to determine the quality of the soldered portion.

Next, the height determination processing means 116 will be explained in more detail with reference to FIG. FIG. 5 shows a block diagram of the height determination processing means 116. In FIG. 5, 501 is calculated height data, 502 is a difference calculation circuit that calculates the difference between the height data, and 503 is
04 is a comparison circuit F and G, 505 is a differential threshold storage means,
506 is a height threshold storage means, 507 and 508 are counters H and I, 509 is mask data from the mask storage means 117, and 510 is a determination result from the brightness determination processing means 115.

The operation of the height determination processing means 116 configured as described above will be explained below.

In the difference calculation circuit 502, the mask data 5
09, the amount of change (difference value) in the height data 501 extracted from the image calculation processing means 114 is calculated, and the difference value is output to the comparison circuit F503. The difference is calculated in the direction in which the height data goes from the board to the soldering parts and components.

In the comparison circuit F503, the difference calculation circuit 50
The difference value calculated in step 2 is compared with the threshold value from the difference threshold storage means 505, and if the difference value is within the range determined by the threshold value, a signal of "1" is output to the counter H507 and the counter I508, and the range is If outside, a signal of "0" is output. On the other hand, the comparison circuit G504 compares the height data 501 with the threshold value from the height threshold storage means 506, and if the height data is within the range determined by the threshold value, the counter H507
A signal of "1" is output to the counter I508, and a signal of "0" is output if it is outside the range.

The counter H507 has mask data 509.
Comparator circuits F503 and G50 for each mask based on
Counts up only when outputs from 4 are both "1". Further, the counter I508 analyzes for each mask based on the mask data 509, if the outputs from the comparator circuits F503 and G504 are both other than "1", that is, if expressed as a set of signals (F, G), (1, 0 ), (0, 1), (0,
0), the count is increased.

[0042] Through the above operations, the outputs of the respective counted up counters correspond to the data of the good area and the bad area in the correlation diagram of the height data (Z) and the difference value (ΔZ) shown in FIG. 7(c). The number of distributions indicates the number of distributions, and the quality of soldering of the components can be inspected from these numbers of distributions, and the output of the incremented counter is output to the comprehensive judgment processing means 118. In this way, since the actual height data of the soldered part is used for judgment, the calculation time for judgment is relatively long, but compared to judgment using brightness data, the judgment is not affected by the positional deviation of the component. Accuracy is high.

However, the determination processing by the height determination processing means 116 is carried out in parallel with the luminance determination processing means 11.
The process is continued only when the judgment result 510 from the brightness judgment processing means 115 is bad, and is interrupted and reset when the judgment result 510 from the brightness judgment processing means 115 is good.

As described above, according to this embodiment, the brightness data and height data of the parts and soldered parts on the printed circuit board are measured, and the measured brightness data and height data are processed for brightness determination in parallel. The means and height determination processing means perform calculations only on the mask data from the mask storage means. The brightness determination processing means is characterized in that it requires relatively little calculation time, and the height determination processing means is characterized in that it requires a relatively large amount of calculation time but has high determination accuracy. Therefore, when the judgment result of the brightness judgment processing means is good, the comprehensive judgment processing means judges it as good without waiting for the judgment result of the height judgment processing means, and when the judgment result of the brightness judgment processing means is bad, the height By determining pass/fail by the comprehensive determination processing means based on the quality of the determination result of the determination processing means, the processing time up to the comprehensive determination can be shortened compared to the conventional method without reducing the reliability of the determination.

[0045]

As described above, the present invention measures the brightness data and height data of components and soldered parts on a printed circuit board, and uses the measured brightness data and height data respectively to the brightness determination processing means and the height data. The brightness judgment processing means calculates only the mask data from the mask storage means, and if the judgment result of the brightness judgment processing means is good, the overall judgment processing means judges it as good, and the judgment result of the brightness judgment processing means is bad. In this case, the general judgment processing means judges the pass/fail based on the judgment result of the height judgment processing means, which is an excellent implementation that can shorten the processing time until the comprehensive judgment without reducing the reliability of the judgment. This makes it possible to realize a board inspection device.

[Brief explanation of the drawing]

[Fig. 1] Block wiring diagram of a mounted board inspection device in an embodiment of the present invention

[Figure 2] Detailed block wiring diagram of the image calculation processing means in the main part of the device

[Fig. 3] Detailed block wiring diagram of the brightness determination processing means in the main part of the device

[Fig. 4] (a) Cross-sectional view of the soldered part (b) Conceptual diagram showing the inspection algorithm in the embodiment of the present invention

[Fig. 5] Detailed block wiring diagram of the height determination processing means in the main part of the device

[Figure 6] Main part block wiring diagram of conventional mounted board inspection equipment

[Figure 7] Conceptual diagram showing the inspection algorithm of a conventional mounted board inspection device

[Explanation of symbols]

101 Printed circuit board 102 Parts 103 Transport means 105 Laser light source 107 Polygon mirror 109 fθ lens 110 Reflection mirror 111 Condensing lens 112 Position detection element 114 Image calculation processing means 115 Brightness determination processing means 116 Height judgment processing means 117 Mask storage means 118 Comprehensive judgment processing means

Claims (1)

[Claims] 1. A transport means for moving a printed circuit board on which components are mounted, and a laser beam scanning means for scanning a laser beam from a laser light source onto the printed circuit board using a polygon mirror and an fθ lens. Then, the scattered light obtained by being reflected from the printed circuit board by the scanning of the laser beam is reflected by a reflection mirror provided between the printed circuit board and the fθ lens, and the scattered light is reflected by the reflection mirror provided between the fθ lens and the polygon mirror. a scattered light reflecting means for reflecting the scattered light through the scattered light reflecting means; a light amount detecting means for further condensing the scattered light from the scattered light reflecting means onto a position detection element using a condensing lens and outputting a photocurrent signal; and a light amount detecting means for outputting a photocurrent signal; image calculation processing means for calculating brightness data and height data of the printed circuit board, the components mounted on the printed circuit board, and the soldered portions based on current signals; A mask storage means for storing mask data for processing a plurality of masks of a predetermined arbitrary size, and the brightness data in the mask data from the mask storage means are used to determine the quality of the soldering state. a brightness determination processing means; a height determination processing means for determining the quality of the soldering state using the height data in the mask data from the mask storage means; the brightness determination processing means and the height Comprehensive judgment processing means for comprehensively judging whether the soldering state of the components on the printed circuit board is good or bad using the value calculated by the judgment processing means, and when the judgment result of the brightness judgment processing means is good; If the overall judgment processing means determines that the product is good, and the judgment result of the brightness judgment processing means is poor, the overall judgment processing means judges the quality based on the quality of the judgment result of the height judgment processing means. Mounted board inspection equipment.