JPH0727531A - Inspection region recognizing method for appearance shape inspecting device - Google Patents

Abstract

PURPOSE:To improve the quality judgment accuracy and inspecting speed by providing a region recognition section detecting an object region in reference to the threshold value suitable for the detection of the inspection object region. CONSTITUTION:The light from a multi-stage structure luminaire 10 is reflected by an inspection object 5, and it is received by a television camera 15. Multiple sets of image signals obtained when the luminaire 10 is switched are stored in an image pattern memory section 25. A code generation section 35 generates codes indicating the angular distribution of an object face based on the memory contents, and a recognition processing section 45 recognizes the three-dimensional shape of the object 5 and judges its quality by utilizing the codes. Signals 20 are fed to a land (inspection object) region recognition section 90. The recognition section 90 is constituted of a threshold value calculation section and a threshold value judgment section. The threshold value calculation section collects the image signals of resist and a printed wiring board, adds a fixed additional value to the total, and calculates the threshold value suitable for detection. The threshold value judgment section accurately determines the land position in reference to the threshold value for code generation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inspection device for judging the appearance shape and appearance state of an electronic component soldered joint on a printed wiring board. Using multiple sets of illuminators with a multi-stage structure with different inspection target angles, multiple video signals obtained by switching the irradiation light to the target are generated into code signals expressing the target surface angle for each pixel, and the In the appearance inspection apparatus that determines the quality of a three-dimensional shape from the code pattern distribution, the inspection area is set in a shape that matches the land by the teaching performed in advance. The present invention aims to more accurately detect the inspection area necessary for inspection from the image signal by each stage illumination in this inspection range, and by generating the code only for the detected land,
It is intended to improve the accuracy of quality judgment in appearance inspection and the inspection speed.

[0002]

2. Description of the Related Art Various types of automatic visual inspection devices for fine target parts typified by solder joints have already been developed. As an effective means therefor, a multi-stage illumination inspection method is well known. Is. The outline is as follows. FIG. 10 shows a basic system configuration of a multi-stage lighting type solder inspection device. Light from the illuminator 10 having a multi-stage structure with different light projection angles with respect to the inspection target 5 is reflected from the inspection target 5 and received by the television camera 15. A plurality of sets of video signals 20 obtained by switching the illumination 10 are stored in the image storage device 25 in the form of the luminance distribution pattern of the target surface. The recognition processing unit 45 executes recognition of the three-dimensional shape of the target and determination of quality based on the stored contents of the plurality of sets. The recognition processing unit 45 sequentially moves the moving table 70 to a position suitable for the inspection via the drive device 65 by the table control signal 55 as needed, and causes the processing operation.
For example, if it is assumed that the inspection target is the soldering of the IC leads, a plurality of leads of the IC are included in the screen of the television camera, and an inspection window (that is, an inspection area) is sequentially set for each of the leads and soldering is performed. A pass / fail judgment is made. The setting position of the inspection window is set in advance in such a manner that the coordinates of the land position obtained from the reference point on the printed wiring board are stored in the device as teaching information in advance and the inspection land is usually matched with the soldering land. The quality of the inspection object is determined by using a plurality of pieces of luminance information for each pixel in the inspection window.

[0003]

As described above, the multi-stage illumination type visual inspection apparatus usually uses soldering lands as shown in FIGS. 7 and 11 based on teaching information for setting the inspection range in advance. It is set in a form consistent with 11. However, in the conventional inspection range setting, as shown in FIGS. 8 and 12, the land position may deviate from the inspection range and the resist portion may be recognized as solder. 7 and 8 are perspective views of the soldering portion, and FIGS. 11 and 12 are views showing the relationship between the window and the land. 7, 8, and 11
In FIG. 12, 6 is an IC lead, 7 is a solder fillet that joins the lead and land, 8 is a land on the printed wiring board, 11 is an inspection range based on teaching information, that is, a window, and 101 is a pixel portion within the inspection range. Is.

This is because, in general, when performing an inspection, there is no ability to accurately recognize even one pixel as a reference point, vibration when a printed wiring board is conveyed, and distortion of a substrate and soldering inspection are the same. Since it is difficult to inspect the conditions, the inspection range given in advance may not be an inspection range that exactly matches the pad. Then, the resist portion around the land enters the inspection range, and the solder shape is recognized in an incorrect form.
In order to solve the above-mentioned problems and to realize a higher-performance visual inspection, the shape recognition determination process is performed only within the land, and therefore the inspection range must exactly match the land.

[0005]

In order to solve the above problems, according to the present invention, an inspection area recognizing unit is provided, and the inspection area recognizing unit is composed of two functions of a threshold value calculating unit and a threshold value judging unit. To do. The threshold value calculation unit collects each video signal of the resist and the printed wiring board, gives a constant additional value to the sum, and calculates a threshold value for separating the pad and the resist. This is because the resist and the printed wiring board are flat, but they have the property of scattering light, and since the TV camera receives only scattered light at any angle of incidence, each video signal is very small. become. On the other hand, the land part
This is because both the land and the solder have high light reflectance, so that the video signal from any one of the illuminations at each stage becomes strong.

[0006]

[Function] The threshold value determination unit determines that the land position is accurately determined if the video signal has a higher total sum of the input video signals than the threshold value calculated by the threshold value calculation unit, and determines the land position accurately. It is intended to generate code.

[0007]

FIG. 1 shows an embodiment of the present invention. This is Figure 1
The inspection area recognition unit 90 is added between the image storage device 25 and the code generation unit 35 of the conventional basic system shown in FIG. FIG. 2 is a block diagram showing the structure of the inspection area recognition unit 90. In both figures, 5 is an inspection target (including a solder joint portion of the IC lead), 10 is an illuminator,
Reference numeral 15 is a light receiving sensor such as a television camera, 20 is a light receiving sensor output, 25 is a video pattern storage unit, 30 is a video pattern output, 35 is a code generation unit, 40 is a code generation unit output (code pattern), 45 is a recognition processing unit, 50 is a lighting control signal, 55 is a table control signal, 60 is a lighting switching device, 65 is a table drive device, 70 is a moving table, 9
Reference numeral 0 is a land area recognition unit, 91 is a threshold value calculation unit, and 92 is a threshold value determination unit. First, a conventionally known inspection method using multi-stage illumination will be briefly described. Illuminator 10 having a multi-stage structure in which the light projection angles to the inspection target 5 are different
The television camera 15 receives the light reflected by the inspection object 5 from the. A plurality of sets of video signals 20 obtained by switching the illumination 10 up and down are stored in the image storage device 25 in the form of a luminance distribution pattern on the target surface. The code generation unit 35 generates a code distribution pattern indicating the angle distribution of the target surface based on the stored contents of the plurality of sets, and the recognition processing unit 45 uses the code distribution pattern to recognize the three-dimensional shape of the target and determine the quality. . Known examples of the automatic appearance inspection apparatus using such an inspection system using multi-stage illumination include JP-A-61-41906, JP-A-4-301549, JP-A-4-343046, and JP-A-4-346011.
Now, as shown in FIG. 3, the recognition processing unit 45 sequentially moves the moving table 70 to a position suitable for the inspection by the table control signal 55 via the drive device 65 as necessary, and illuminates it via the illumination control signal 50. The switching device 60 switches the illumination. Furthermore, the recognition processing unit 45 sets a window in the inspection target range, converts the luminance distribution image into a code distribution (window-encodes for each pixel), recognizes the target three-dimensional shape from the code distribution pattern, and determines whether it is good or bad. It is also a control unit for performing processing operations. For example, when the inspection object 5 is an IC as shown in FIG. 9, the relationship between the projection light from the illuminator 10 and the solder fillet of the IC lead which is the inspection object 5 is shown in FIG. In FIG. 4, 6 shows the cross-sectional shape of the leads of the IC, and 7 also shows the cross-section of the solder fillet that electrically joins the leads and the lands 8 on the printed wiring board 9. FIG. 3 shows this series of processing steps when the inspection target is assumed to be the soldering of the IC leads. Although a plurality of leads of the IC are included in the screen of the television camera, an inspection window is sequentially set for each of them to judge whether the soldering is good or bad. The setting position of the inspection window is set in advance in such a manner that the coordinates of the land position obtained from the reference point on the printed wiring board are stored in the device as teaching information in advance and the inspection land is usually matched with the soldering land. A code signal for describing the angle of the target surface is generated using a plurality of luminance information for each pixel in the inspection window, and the three-dimensional shape of the target is grasped and the quality of the target is judged from this code distribution pattern. When the inspection object 5 enters the screen of the television camera 15, each video signal 20 is sampled and enters the land area recognition unit 90. Here, reflected light is respectively reflected by S1, S3, S5, with respect to incident light by 10-1, 10-3, 10-5 and 10-7 according to FIG.
And S7. The sum of the video signal levels from S1 to S7 on the printed wiring board around the inspection object in the threshold value calculation unit 91 is defined as S0, and this S0 is a temporary threshold value for separating the land and the resist. To do. The threshold value s is determined by adding the discriminant constant t set according to the type of substrate to the provisional threshold value s0. Usually the discriminant constant t is s
Set to 1/2 of 0. When the threshold value s is determined, the threshold value judging unit 92 inspects the video signal level in the range from A to B, which is wider than the conventional inspection range from C to D in FIG. The inspection method calculates the sum s0 of the video signal levels for each pixel from A and compares it with the threshold value s.
Then, the coordinate N1 at which the video signal level becomes higher than the threshold value s is recognized, and the process proceeds toward B. Next, the coordinate N2 whose video signal level becomes smaller than the threshold value s is recognized. FIG. 6 is a graph showing the variation of the video signal level from A to B in this step. By this operation, the land areas N1 to N recognized by the actual land areas P1 to P2 are detected.
It agrees with 2. In this way, by performing a series of operations in the threshold value judging section 92, N1 to N2 become the actual land range. Therefore, the land area obtained by the land area recognizing unit 90 can be passed to the code generating unit 35 and the code can be generated only in the land area.

[0008]

As described above, strict recognition of the inspection object range by the present invention is important for accurately recognizing the shape of the object, and must be obtained stably. Since it is the minimum condition that does not occur, it is effective in improving the performance of the appearance inspection device for glossy objects such as soldering. In addition, the recognition of the inspection range has been described only for one direction in FIG. 5, but the principle of the present invention is also applicable when recognition is performed in a direction orthogonal to this direction or when recognition is performed at a plurality of locations in the same direction. It is possible within.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram of a land area recognition unit that is an embodiment of the present invention.

FIG. 3 is an operation flowchart of a land area recognition unit that is an embodiment of the present invention.

FIG. 4 is a diagram showing a reflection model of an optical system.

FIG. 5 is a diagram showing a land area inspection method according to the present invention.

FIG. 6 is a diagram showing a relationship between a video signal level and a land according to the present invention.

FIG. 7 is a model diagram of code generation by normal inspection area setting in the multi-stage illumination type visual inspection apparatus.

FIG. 8 is a model diagram of code generation by an erroneous inspection area in the multi-stage illumination type visual inspection apparatus.

FIG. 9 is a plan view of an IC lead.

FIG. 10 is a block diagram of a conventional example.

FIG. 11 is a diagram showing a correct relationship between a window and a land.

FIG. 12 is a diagram showing a relationship between a window having an error and a land.

[Explanation of symbols]

 5 Inspection target (including solder joint of IC lead) 6 IC lead 7 Fillet for joining land and lead 8 Soldering land on printed wiring board 9 Printed wiring board 10 Illuminator 11 Inspection window area 15 Light receiving sensor such as TV camera 20 light receiving sensor output 25 video pattern storage unit 30 video pattern output 35 code generation unit 40 code generation unit output (code pattern) 45 recognition processing unit 50 lighting control signal 55 table control signal 60 lighting switching device 65 table driving device 70 moving table 90 Land area recognition unit 91 Threshold value calculation unit 92 Threshold value determination unit

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Claims (2)

[Claims] 1. A plurality of sets of illumination light sources having different projection angles to an inspection target, and reflected light from the inspection target by the illumination light sources are received as a reflected light luminance distribution in a two-dimensional area including the inspection target. A light receiving sensor for outputting as an electric signal, a storage device for storing a plurality of light receiving sensor output signal patterns obtained by switching the light emitting positions of the plurality of illumination light sources, and the plurality of signal patterns as input, A code signal generation unit that generates an angle code at each position of a two-dimensional region including the inspection target, and a recognition processing device that recognizes the three-dimensional shape of the inspection target based on the distribution state of the generated code in the inspection region. A method for recognizing an inspection target for code generation in an external appearance shape inspection device, which has a function of calculating a threshold value suitable for detection of an inspection target area from the output information of the light receiving sensor A method for recognizing an inspection area in an appearance shape inspection device characterized by having a function. 2. The appearance shape inspection apparatus according to claim 1, comprising a method of recognizing an inspection target area for code generation,
An inspection area recognition method, characterized in that the input information has a function of detecting an inspection area by referring to the threshold value of claim 1.