JPH02212747A - Packaged circuit board inspector - Google Patents

Abstract

PURPOSE:To enable judgment of an amount of solder without being affected by a positional deviation by a method wherein a circuit board lighted from a direction of a normal of a printed circuit board is photographed from the same normal direction and an area ratio of 1 and 0 is computed within a mask with the binary coding of a brightness signal obtained to judge the propriety of a soldering from the ratio. CONSTITUTION:A printed circuit board 101 with parts 102 mounted is lighted from a direction of normal of the board 101 by a lighting means 103 such as ring lighting and photographed from the same normal direction using a camera means 104 such as CCD camera to obtain a brightness signal 105. Then, this signal is inputted into a binary coding means 10 and compared with a desired threshold to output a binary coded signal 114. A judgment processing means 108 receives an input of a mask data in a desired size predetermined for a mask processing at a position of a land for soldering on the board from a mask memory means 107. Thus, an area ratio of 1 and 0 within a mask is computed using the data and the binary coded signal 114 thereby judging the propriety of soldering from the ratio.

Description

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

BACKGROUND OF THE INVENTION Conventionally, inspection of soldered parts on printed circuit boards has relied on human visual inspection. However, as products become smaller and lighter, components on printed circuit boards are also becoming smaller and more densely packaged. Under these circumstances, visual inspection by humans is becoming increasingly difficult, and there is a strong desire for automation of inspection.

As one method, Japanese Patent Application No. 63-45206 proposes L5 to use luminance data with a two-dimensional camera and to judge the quality of the solder portion from the cumulative frequency distribution of luminance.

In Fig. 7, illumination i, +' A is applied to the solder part from the diagonal upper blade.
L shown in the cumulative frequency distribution of good and defective products for half [ ] 1 in case 7
1 The horizontal axis represents the brightness class, and the vertical axis represents the cumulative number of brightness 1u. A good solder part has many parts with high brightness waves, so it exhibits a distribution characteristic like the cumulative frequency distribution 701 of long parts. Since there are many defective 1"', ■1 parts (・7j, dark l/'1 parts of bright i, the defective part exhibits a distribution characteristic such as the cumulative frequency distribution 702. As shown in the 7th shj, The distribution characteristics of non-defective products and defective products are different, and secondly, they can be classified by size.

Problem to be Solved by the Invention 7 However, in the inspection method shown in the conventional example, the curve of the cumulative frequency distribution varies depending on the positional deviation of the component, the amount of solder, etc., and therefore it is not possible to make a sufficiently reliable determination. The best lighting! If it's not 1, it's 4゛, good or bad? The problem is that it is difficult to distinguish between genders. Furthermore, lighting unevenness and lighting streaks due to the position on the printed circuit board! There is also the issue that in order to optimize the size of 1, it is necessary to divide the image into small areas (.5).

The present invention can be applied to the left and right top 5 to prevent misalignment of components and amount of solder.
・The first purpose is to divide the luminance signal into 2
It is converted into a value and judged as good or bad based on the area ratio of 1 and O within a mask set on the land.

The second purpose is to obtain two-dimensional brightness data of the printed circuit board by scanning the printed circuit board with a scanning 1-1 conveyance means using a laser beam using a polygon mirror and an fθ lens as a means of obtaining brightness (No. 2). ni [5, it's a thing.

The third purpose is to further clearly identify the characteristics of soldering defects by adding the luminance signals obtained from a pair of light quantity detection means +1+ means, thereby improving the determination accuracy.

The fourth purpose is to determine the quality of a component that has two half-FBs by calculating the area ratio of 1 and O in the sum of the pairs.

JV-Meaning for Solving the Problems In order to achieve the above object, the technical solution of the present invention firstly provides illumination means for illuminating the printed circuit board from the normal direction; 711 direction, t, 0 center (φ image drying imaging 1 stage 1 and moe 1. "1 渭most f"uguding stage no. 6, -2 Binarize the luminance signal from 6, -2 with an arbitrary threshold value 2 Valorization means,■
- a mask storage means for storing mask data of a predetermined arbitrary size for performing mask processing on the land position; It is composed of a processing means that calculates the area ratio of l(!:O in the area) and determines the quality of soldering from the area ratio.

Second, as another means for obtaining the first brightness I, there is a transport means for transporting the printed circuit board, and a laser beam scanning means for scanning the printed circuit board with laser light from a laser light source using a polygon mirror and an fθ lens. Then, the scattered light obtained by being reflected from the printed circuit board by scanning the laser beam is reflected through an fθ lens and a polygon mirror, and further focused on a photodetecting element by a condensing lens to generate a luminance signal. It is composed of output light amount detection means.

Thirdly, in the second configuration, the two light quantity detection means are provided at symmetrical positions on the scanning plane of the laser beam, and the difference obtained from each of the light meter detection means is ( 1, l, ;,
, 5-zo7 each by binarization means! After binary conversion, both binarized signals are combined by a synthesizing means, or after each luminance signal is added by an adding means, a binary signal is obtained by a binarization means. .

Fourthly, in addition to the first, second, or third configuration, in the determination processing means that determines whether the solder is good or bad, if there are two parts to be soldered, one
By adding the areas of and O, respectively, and calculating one area ratio on a bare basis, the determination processing means is configured to determine the quality of the soldering.

According to the above configuration, the present invention first images a printed circuit board illuminated from the normal direction of the printed circuit board from the same normal direction, binarizes the luminance signal from the imaging means, and converts the luminance signal into a binary signal. The area ratio of 1 and O in the mask is calculated from the above, and the quality of the soldering is determined based on the area ratio. Second, as a means of obtaining a luminance signal, a laser beam is irradiated onto a printed circuit board, the scattered reflected light is reflected by a polygon mirror and an fθ lens, and then the light is focused on a photodetector element by a condenser lens to obtain a luminance signal. This is what is output.

Thirdly, two light amount detection means are provided at symmetrical positions with respect to the scanning plane of the laser beam, and the luminance signals obtained from each light amount detection means are combined by a combining means or addition means to obtain a binarized signal. This allows us to more clearly understand the characteristics of solder defects.

Fourthly, for parts that are soldered at both ends, the determination processing means determines whether the parts are soldered in pairs.
By evaluating based on the area ratio of 1 and 0 of the value signal, it is possible to comprehensively judge the quality of soldering of parts with misalignment.

EXAMPLE A first example of the present invention will be described below with reference to FIG.

FIG. 1 is a block diagram showing a first embodiment of a mounted board inspection apparatus of the present invention. In FIG. 1, 101 is a printed circuit board, 102 is a component mounted on the printed circuit board 101, 103 is an illumination means for illuminating the printed circuit board 101, and 104 is an imaging means such as a CCD camera for taking an image of the printed circuit board 101. It is. 106 is a binarization means for binarizing the luminance signal 105 from the imaging means 104;
Reference numeral 107 denotes a mask storage means for storing in advance a mask for mask processing. Reference numeral 108 denotes a determination processing means for determining the quality of soldering, and each component is as follows. 109 is a total counter that calculates the total area within the mask;
110 is an O counter that calculates the area of 0 in the mask in the binary signal, 111 is a divider that calculates the area ratio of 1 and 0 in the mask, and 112 is a threshold for determining the quality of soldering. 113 is a comparator that compares the result of the divider 111 with the threshold value from the threshold storage means 112. 114 is a binary signal.

The operation will be explained below.

A printed circuit board 101 on which a component 102 is mounted is illuminated from the normal direction of the printed circuit board 101 using an illumination means 103 such as a ring illumination, and an image is taken from the normal direction of the printed circuit board 101 using an imaging means such as a CCD camera. , luminance signal ]05 is obtained. The luminance signal 105 is compared with an arbitrary threshold value by the base value conversion means 106 and converted into a binary signal 114.
Output. In the determination processing means 108, the printed circuit board 1
In order to mask the position of the soldering land provided on 01, predetermined mask data of an arbitrary size is inputted from the mask storage means 107, and the mask data and the two from the binarization means 106 are input. Using the value signal 114,
The area ratio of 1 and 0 in the mask is calculated, and the quality of soldering is determined from the area ratio. That is, according to the mask data from the mask storage means 107, the total counter 109 counts all the binary signals in the mask, and the 0 counter 110 counts only when the binary signals in the mask are 0 signals. are doing. The divider 111 calculates the ratio between the output of the total counter 109 and the output of the 0 counter 110, and the comparator 1]3 stores the area ratio value from the divider 111 and the threshold for determining the quality of the solder part. The value from the threshold storage means 112 is compared to determine whether the soldering part is good or bad.

This soldering is shown in Figures 2 and 3 regarding how to judge the quality of the part.
This will be explained in more detail using figures.

11 Figure 2 (,1), (1)) shows the side and plane views of the component 202 on the printed circuit board 201.
ing. Irradiation light 203 (■, (
■, ■) is the reflected light 20.1 from the component 202-1- and the solder surface, which is reflected from the CCD camera 7 installed in the direction of the normal line j) of the printed circuit board 201 (in the same figure, one direction). The light is focused on a photoelectric conversion element and converted into a luminance signal.

In particular, the solder portion 2 () 5 and the electrode portion 206 form a mirror surface 7.
It has the characteristic of specular reflection. In Figure 2(a),
Irradiation 'N', 203 (■, ■, ■) is irradiated onto the land 207, the electrode portion 206, and the solder fillet 205, respectively, and the reflected light 204 (■') is irradiated onto the land 207, the electrode portion 206, and the solder fillet 205, respectively.

■′, ■′) are reflected. At this time, the reflected light 204 is reflected by a portion of the planar electrode portion 206 and one tendon 207 toward the electric conversion element and is converted into a brightness signal with a high brightness level. The irradiated light 203■ irradiated onto the solder fiber (which is not a flat surface) 205 is specularly reflected by the semi-[1 riireno) 2 (15, and has the characteristic that it does not return to the photoelectric conversion element side as the reflected light 204 (■') (F' do.

If we look at this as a luminance signal, -11; of the electrode part 206 and land 207, which are flat as shown in Fig. 2 (I), becomes a bright bright part 208, and the area of -11; The area is dark and becomes a dark area 2095, and when such epi-illumination is 1mm, the characteristics of the luminance signal on the side 1M are as shown in Figure 2 (1)).
) -7Sk A210 (displayed by broken line) is set to any size of land 2070. Within this mask A210, the luminance signal is binarized and generated at an arbitrary luminance level f'V:
2 (1 (bright part 209) and 0 (dark part 21) of the iji conversion signal
0) to determine the quality of the soldering parts.

For example, as shown in Figure 3, the area ratio of 0 (dark area) of the binarization code to the entire mask is #! When determining the quality of a part, it can be roughly classified depending on whether the area ratio of the dark part is larger or smaller than the threshold value A 301. That is, without soldering a) 30
2 or insufficient solder (++) In the case of 303 + (j, ゛1'-
When there is less formation of fillets, the area ratio of the dark area within the mask becomes smaller. Also, when determining the cases of 13 and excessive solder (d) 305, where the area ratio of the dark part is abnormally large compared to the IL good product (C) 304, a threshold value B506 is set to distinguish it from a good product. Can be done.

As described above, in this embodiment, the illumination means, the imaging means, the mask, and the soldering means that accurately captures the characteristics of light reflection of the part (C) binarize the luminance signal of the part, and from the area ratio, By using the binarization and judgment processing means to judge the quality of the attached part, there is no need to set delicate lighting conditions, and one ask is set on the land to be soldered, and the two values within the -7 ask are set on the land to be soldered. Since the relative area ratio of the solder signals is compared, it is not affected by the amount of solder, the shape, the size of the part, etc., so a very reliable determination can be made.

Next, a second embodiment of the present invention will be described using FIG. 1.

FIG. 4 is a block diagram showing a second embodiment of the mounted board inspection apparatus of the present invention. In this embodiment, in place of the illumination means and imaging means used to obtain the luminance signal in the first embodiment, another three stages using a laser beam are used, and the same as in the first embodiment is used. A signal with a brightness of 1.1 can be obtained.

In FIG. 4, 401 is a printed circuit board, 1.02 parts are mounted on the printed circuit board 40, 7103 is a transport means for moving the printed circuit board 401, and 404 is an arrow indicating the direction of movement thereof. As a laser beam scanning means, 405 is a laser beam (original), 406 is a laser beam from a laser f light source 405, 407 is a polygon mirror, 408 is a mirror that guides the laser beam 406 to a polygon mirror 407, 40
9 is an fθ lens. In addition, as a light amount detection means, 41
0 is a condenser lens, and 41 is a light detection element. In addition, 1
05 is a luminance signal from the photodetector element 411, 106 is a binarization means, 107 is a mask storage means, and 108 is a determination processing means. These are the same as those in the first embodiment of the present invention, so the same numbers are used. A detailed explanation will be omitted.

The operation will be explained above.

While moving the printed circuit board on which the component 402 is mounted in the direction of the arrow 404 by the transport means 403, the three mirrors 10 are moved against the laser source 406 from the laser light source 405.
8 is used to guide the laser beam 406 to the rotating polygon mirror 156-407, and the polygon mirror 407 and fθ lens 409 irradiate the laser beam 406 vertically onto the printed circuit board 401. This causes the laser beam 406 to scan the entire surface of the printed circuit board 401 two-dimensionally.

Scattered light reflected from the printed circuit board 401 by the scanning of the laser beam 406 is passed through an fθ lens 409 and a polygon mirror 407, and further through a condenser lens 410 to a photodetector element 41 which is a photoelectric conversion element. It emits light and outputs a luminance signal 105.

The subsequent operation is the same as that of the first embodiment, so it will be briefly explained.
Using the binary signal and the mask data from the mask storage means 107, the determination processing means 108 calculates the area ratio of 1 and 0 in the mask, and determines whether the soldering is good or bad based on the area ratio. .

As described above, in this example, laser light and polygon mirror
By using an fθ lens, a condensing lens, and a photodetection element, it is possible to obtain a similar brightness signal of the printed circuit board by means different from the first embodiment, and the laser beam can be irradiated perpendicularly to the printed circuit board. This makes it possible to eliminate the adverse effects of uneven illumination due to the position on the printed circuit board. In addition, by selecting the rotation speed of the polygon mirror, the spot diameter of the laser beam, and the moving speed of the conveyance means, the resolution of the luminance signal on the printed circuit board can be increased much more easily than when using a CCD camera, etc. This makes it possible to inspect soldered parts with higher accuracy.

A third embodiment of the present invention will be described below with reference to FIG.

FIG. 5 is a block diagram showing a third embodiment of the mounted board inspection apparatus of the present invention. In FIG. 5, a condenser lens 501 and a photodetector element 502, which are light amount detection means, are further provided at positions symmetrical to the scanning plane of the laser beam, and an adding means 504 calculates the amount of light from these two photodetection elements. The luminance signals (1o5 and 5o3) are added and the binarization means 106
Since the configuration is the same as that in Figure 4 on page 17 shown in the second embodiment of the mounted board inspection device of the present invention, the same numbers as in Figure 4 are given and explanations are omitted. do.

The operation will be explained below.

As in the second embodiment, while the printed circuit board 401 on which the component 402 is mounted is moved by the transport means 403, the laser beam 406 is guided to the polygon mirror 407 and irradiated vertically onto the printed circuit board 401 through the fθ lens 409. do.

Scattered light reflected from the top of the printed circuit board 4 by the scanning of the laser beam 406 is collected via an fθ lens 409 and a polygon mirror 407 through condenser lenses 410, 501, and Photodetection element 4]
, 1 , leading to 502. and photodetector element 411
．． , 502 output luminance signals 105 and 503, and adding means 504 adds the two luminance signals, and then 2
It is binarized by the digitization means 106. Using the binary signal and the mask data from the mask storage means 107, the determination processing means 108 calculates the area ratio of 1 and O in the mask, and determines the quality of the solder (=1 digit) from the area ratio. .

In the operations described in more than 18 pages, the operation of providing two light quantity detection means and adding the two obtained luminance signals will be explained using FIG.

FIG. 6 shows a soldering failure caused by misalignment of components soldered on a printed circuit board. 6
01 is a printed circuit board, 602 is a component soldered to the printed circuit board 601, 603 is an electrode part of the component 602,
604 is a land, 605 is a defective soldered portion, 606 is laser irradiation light, and 607 is reflected light. In a defective soldering state as shown in FIG. 6(a), the irradiated light beams 606 (■) and (2) are reflected in different directions as reflected light beams 607 (■' and ■'), respectively. Looking at this as a luminance signal, Fig. 6(b)
As shown in FIG. In the signal, the bright parts are bright part A608 and bright part C
(within the broken line) 610, and the dark part is the dark part 61]. That is, in the case of a solder defect as shown in FIG. 6(a), the area of the bright part that appears as a characteristic of the defect is
.

By providing two means and adding both luminance signals, a larger image can be obtained.

As described below, in this embodiment, the light detection means is provided at a position symmetrical to the scanning plane of the laser beam, and the addition means adds the luminance signals from both light detection means, thereby further identifying the characteristics of solder defects. This allows for a clearer understanding of the soldering process and improves the accuracy of determining whether the soldering part is good or bad.

In this embodiment, the luminance signals from both light detection means are added by the addition means and then binarized by the binarization means. ,
Logically OR the post-binarized signal.

Even if the combination is performed using a combination means such as a circuit, the same effect as that of this embodiment can be obtained, and the order of combination of the two luminance numbers in the binarization means table does not limit the present invention in any way.

Next, the first embodiment of the mounted board inspection device of the present invention is as follows.
This will be explained using FIG. 2(b) used in the first embodiment of the present invention. In the same figure, the part is exposed to the solder (approximately in the center of the four-car land 207), but soldering defects caused by misalignment of the part, etc. can be seen only in the bright and dark areas on the right or left side. The judgment becomes delicate, and it is detected as a defect ((<< 7(, sometimes.

Therefore, in the determination processing means 108, the [9] part and the dark part of both the mask A2o) and the mask B211 are added by an adding means (not shown), and one area ratio is calculated in the bare area, and the total is calculated. Judgment accuracy can be improved by making a comparison, and a wider allowable range can be set for a position (6 deviation, etc.) versus (7).

Effects of the Invention As described above, the effects of the present invention include: binarizing a luminance signal with an arbitrary threshold value, calculating the area ratio of ] and 0 in the mask using the binarized signal and mask data,
By determining the quality of half-A1 from the area ratio, it becomes possible to determine the amount of solder without being affected by positional deviation, which has the great effect of automating inspections and improving work efficiency. be able to.

2] The method of obtaining the Beige luminance signal is to use laser light and fθ
2 to the printed circuit board by lens and polygon mirror
By irradiating the light vertically, there is no need to consider uneven illumination depending on the position on the printed circuit board. In addition, by providing the photodetection means at a symmetrical position to the scanning plane of the laser beam and adding the two luminance signals obtained from both photodetection means, it is possible to more clearly capture the characteristics of solder defects. Therefore, the determination accuracy can be improved.

When there are two twisted solder parts, the determination accuracy can be further improved by performing determination in pairs.

[Brief explanation of the drawing]

Fig. 1 is a block wiring diagram of a mounted board inspection device according to the first embodiment of the present invention, Fig. 2 is an explanatory diagram of a method for determining whether or not a part is soldered by the same device, and Fig. 3 is a state of soldering by the same device. FIG. 4 is a block diagram of a mounting board inspection device according to the second embodiment of the present invention, and FIG. 5 is a diagram showing the relationship between the area ratio of 0 and 0. FIG. FIG. 6 is a state diagram of solder failure caused by misalignment, etc., and FIG. 7 is a characteristic diagram of the cumulative frequency distribution of a conventional semi-aE inspection. 101--Printed circuit board, 102-Components, 103-Illumination means, 104-Imaging means, 1.06--Binarization means,
107...Mask storage means, 108...Determination processing means, 405.Laser light source, 407...Polygon mirror
409... fO lens, 410 - Condensing lens, 41
]...Photodetection element. Name of agent: Patent attorney Shigetaka Awano and one other person

Claims (4)

[Claims] (1) illumination means for illuminating components arranged and soldered on a printed circuit board from the normal direction of the printed circuit board;
an imaging means for capturing an image of the printed circuit board from the normal direction of the printed circuit board; a binarization means for binarizing the luminance signal from the imaging means using an arbitrary threshold; and soldering provided on the printed circuit board. mask storage means for storing mask data of a predetermined arbitrary size to be subjected to mask processing at the position of the land for use in the mask; and a binary signal from the binarization means and the mask data from the mask storage means to A mounting board inspection device comprising a determination processing means for calculating the area ratio of 1 and 0 in the area ratio and determining the quality of soldering from the area ratio. (2) As a means for obtaining a luminance signal, a conveying means for conveying a printed circuit board, a laser beam scanning means for scanning the printed circuit board with a laser beam from a laser light source using a polygon mirror and an fθ lens, and scanning of the laser beam. comprises a light amount detection means for reflecting the scattered light obtained by reflection from the printed circuit board through the fθ lens and the polygon mirror, and further condensing the light onto a photodetection element with a condenser lens and outputting a luminance signal. The mounted board inspection apparatus according to claim 1, characterized in that: (3) Two light quantity detection means are provided at symmetrical positions with respect to the scanning plane of the laser beam, and after each luminance signal obtained from each light quantity detection means is binarized by the binarization means, both are binarized. 3. The mounted board inspection apparatus according to claim 2, wherein the signals are synthesized by a synthesizing means, or after the respective luminance signals are added by an adding means, a binarized signal is obtained by a binarizing means. (4) For components with two soldering locations, the determination processing means for determining the quality of solder adds the areas of 1 and 0 in both masks, and calculates one area ratio for each pair. 2. The mounting board inspection apparatus according to claim 1, further comprising a determination processing means for determining the quality of soldering by performing the following steps.