JPH06137829A - Inspecting device for outside appearance shape - Google Patents

Abstract

PURPOSE:To improve the accuracy of the judgement of quality and inspecting speed in coding the output of a sensor to receive reflected light from an inspection objective body by preparing a objective face description code through the judgements of a threshold and of a relative value. CONSTITUTION:Two thresholds Sa, Sb are set up, and a code is prepared as follows. In the case where an image signal level Si exceeds the threshold Sa, the codes No 1, 3, 5, 7 are respectively allotted for spaces a, c, e, g. In the case where two kinds of levels Si exceed the threshold Sb together, two kinds of middle codes, namely codes No 2, 4, 6, are allotted for spaces b, d, f. In the case where the level Si exceeds the threshold Sb, codes No 1, 7 are allotted for spaces h, i. A code No 8 is allotted for a space j. Thus the code can be prepared without computation processing.

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 or appearance state of an object having a glossy surface such as a soldered joint of an electronic component on a printed wiring board, and particularly an irradiation angle to the inspection object. Using a plurality of sets of illuminators with a multi-stage structure so as to be different, the stereoscopic shape of the inspection target is recognized based on a plurality of images obtained by switching the irradiation light to the target, and the quality is judged. The present invention relates to a video signal processing method used in a visual inspection apparatus of a system, and more specifically to a code signal generating method for describing a three-dimensional structural state of an inspection target from the plurality of video signal patterns.

In the above-mentioned multi-stage illumination type visual inspection apparatus, in order to recognize the state of the target surface at high speed, a code signal for expressing the target surface angle is generated for each pixel of the image,
Generally, a method of grasping the target three-dimensional shape from the obtained code pattern distribution is adopted. According to the present invention, in this code generation, by adaptively using a plurality of video signals, a more accurate description of the flatness and the inclination of each target portion can be executed at high speed regardless of the reflection characteristics of the target surface. The purpose of the invention is to contribute to improvement of accuracy of quality judgment in appearance inspection and improvement of inspection speed. In order to clarify such a main point of the present invention, details of the multi-stage illumination type appearance inspection machine will be described below with reference to FIGS. 2 to 11.

[0003]

2. Description of the Related Art Among various inspection processes in the production process,
Visual inspection occupies an important position in understanding the status of the manufacturing process itself and ensuring manufacturing quality. For example, in the mounting process of printed wiring boards used for electronic devices, the quality of the soldered parts that join the electronic components mounted on the board affects product reliability. Has been done. However, with the recent progress in high-density mounting of printed boards and miniaturization of electronic components, automation and mechanization of soldering visual inspection have been generalized for the purpose of improving work efficiency and ensuring work quality. Various types of automatic appearance inspection apparatuses for fine target parts typified by solder joints have been already developed, and an effective method is an inspection method using multistage illumination. Fig. 2 shows the basic system configuration of the multi-stage lighting solder inspection device. Multi-stage structure with different light projection angles (two stages in the figure)
The reflected light from the illuminator 20 through the inspection object 10 is received by the television camera 30, and a plurality of sets of video signals 130 obtained by switching the illumination are image-stored in the form of a luminance distribution pattern on the target surface. It is stored in the device 50. The code distribution pattern 1 in which the code generator 70 indicates the angular distribution of the target surface using the plurality of sets of stored contents 150 as input signals
70 is generated, and the recognition processing unit 90 uses this to recognize the three-dimensional shape of the target and determine whether it is good or bad.
Assuming that the inspection target is the soldering of IC leads,
This series of processing steps is shown in FIG. Although a plurality of leads of the IC are included in the screen of the television camera 30, an inspection window is sequentially set for each of the leads and the quality of soldering is determined. The setting position of the inspection window is usually set in a form that matches the soldering land, based on teaching information performed in advance. A code signal for describing the angle of the target surface is generated by a method described below by 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 the code distribution pattern. Done. In FIG. 2, reference numeral 60 is an illumination switching device, 40 is a moving table for sequentially moving the target, and 80 is a driving device thereof. The recognition processing unit 90, which also has a function as a control unit, sequentially moves 40 to a position suitable for inspecting each of a plurality of inspection targets via the table control signal 180 as necessary, and outputs the illumination control signal 160. The illumination is switched via the above, and the processing operation of FIG. 3 is executed sequentially. FIG. 4 is a side view showing more specifically the relationship between the optical system and the inspection target in the multi-stage lighting solder inspection apparatus. The illuminator is 20-, 20-, 20-
Also, the annular illuminator is composed of four stages of 20-, and is arranged on a concentric circle when viewed from the upper side of the drawing. A plurality of television cameras 30 are often used in order to enable inspection according to the structure of the target, but generally, the vertically arranged 30-a is used. FIG. 5 shows the relationship between the projected light from these illuminators and the solder fillet of the IC lead to be inspected. In FIG. 5, 11 is an IC
2 shows the cross-sectional shape of the lead, and 12 also shows the cross-section of the solder fillet that electrically joins the lead and the land 8 on the printed wiring board 9. Also, each arrow, 21
-21-, 21-, and 21- are illuminators 20-, 20-, 20-, and 20-, respectively.
Shows the optical path of the reflected light through the object. Since the illuminators have different projection angles, the reflected light having the highest brightness at the different angle portions of the solder fillet to be inspected is received by the television camera in the upper part of the figure. That is, when each illuminator is given a slight surface illumination characteristic, the reflected light from the illuminator to the TV camera shows the maximum brightness at a specific fillet angle (hereinafter, this is referred to as the reflection center angle of the illuminator). , The brightness decreases as the target surface shifts from this angle. FIG. 6 shows the relationship between the target surface angle and the brightness of the reflected light. The reflection center angle of each illuminator is determined by the structure of the optical system. In the case of the figure, 5 °, 15 °, and 25 °, respectively.
An example is shown in which the design is made in ° and 35 °. Using the reflection characteristics of each illuminator, the luminance distribution pattern of the target surface and the angle code distribution pattern based on the luminance distribution pattern are formed by the method shown in FIGS. 7 to 9. That is, when the solder fillet 12 shown in FIG. 7A is to be inspected, first, an inspection window 10 based on the land 8 is used.
Set to 0. Then, by switching the illuminator, the video signal shown in FIG. 8 is obtained in the inspection window region. In FIG. 8, 140-, 140-, 140-, and 140- are illuminators 20- and 20-, respectively.
, 20-, and 20- are video signal patterns of the television camera corresponding to the irradiation, and show a luminance distribution according to the three-dimensional shape of the target surface. It should be noted that one unit 101 of the mesh portion in FIGS. 7 and 8 corresponds to one pixel in the image of the television camera, and its size is determined by the configuration of the optical system. Each image area in FIG. 8 corresponds to the inspection window 100 in FIG.
The angle code generation processing using the above-mentioned four types of images is executed for each pixel inside. When a four-stage illuminator is used, eight-stage code generation based on the reflection center angle of each illuminator is fundamental. That is, the illuminators 20-, 20
Codes No1, No3, No5, and No7 corresponding to the reflection center angles of −, 20−, and 20−,
In addition, codes No2, No4, and
No. 6 is assigned to the angle corresponding to code No. 7 and above, or code No. 8 is assigned when the angle is unknown. Such code generation is basically executed in the form of integer arithmetic by the following arithmetic expression. Code number = A1 × S1 + A3 × S3 + A5 × S5 + A7 × S7 / B1 × S1 + B3 × S3 + B5 × S5 + B7 × S7 (1) In the formula (1), Si is the reflected light luminance level by each illuminator, and each coefficient Ai and Bi. Is determined according to the characteristics of the illuminator and the characteristics of the target surface, but the content thereof is outside the scope of the present invention. In FIG. 6, in the range where the target surface angle is 45 ° or more, all the luminance signal levels are lowered, and the calculation result of the equation (1) is the normal code No4, but from the viewpoint of S / N, the signal level is A code No. 8 is often set as an unknown area if the value is extremely low. FIG. 9 shows a specific example of the code pattern generated based on such calculation. FIG. 1A shows an example in which a good fillet is formed, and an inspection window (that is, a land) 10 is shown.
The pattern distribution in which the angle code gradually increases from the end portion of 0 to the tip portion of the lead 11 can be determined, and it can be determined that the shape of the solder fillet is good, and the code string on the land center line is changed from the end of the inspection land to the lead. By performing cumulative calculation over the tip position, it is possible to calculate the fillet cross-sectional shape shown in FIG. 13, that is, the height and length of the fillet. On the other hand, (b) of the figure shows a so-called lead floating defect in which the lead is lifted and the fillet on the land is not joined to the lead. In the code distribution pattern in this case, cords showing a high fillet gradient are distributed around the inspection window 100, and cords showing a flat angle are concentrated in the center of the window. In the state of No. 13, it can be determined that the solder and the lead are not joined to each other.

[0004]

As described above, the multi-stage illumination type appearance inspection apparatus describes the three-dimensional shape of the target surface based on a plurality of target image patterns obtained by using the illuminators having different projection angles. Although it has the ability to generate a code pattern distribution and accurately execute the shape judgment of the target, the above-mentioned code generation method has the following problems. (1) For many pixels in the inspection window, it is necessary to generate a code that involves multiplication and division operations, which requires processing time. (2) Depending on the property of the target surface, a code indicating the tilt angle may be generated even if the target surface is flat. Of these, (2) will be described with reference to FIGS. 10 and 11. Generally, the soldering lands on the printed circuit board are roughly classified into a case where they are plated to improve the wettability of the solder and a case where they are copper foil materials. FIG. 10 shows the reflection luminance characteristics of a solder surface, a copper foil, etc. by multi-stage illumination. The letters a to i in the drawing show a group of luminance characteristics when the angle of the solder surface exhibiting the mirror surface characteristic changes from the reflection center angle of the illumination 20- to the reflection center angle of 20-. These are code No. 1 and No.
2 or No. 3 is assigned. On the other hand, the copper foil characteristics in the figure show the state on a flat surface, and the code No. 1 should be assigned originally. However, since the copper foil has the scattering reflection property, S1 and S3 in the figure have the same brightness level, so that the code No. 3 corresponding to the tilt angle is assigned in the above-mentioned coding method. As a result, for example, when a solder fillet having a relatively short length is formed in a copper foil land shape as shown in FIG. 11A, it becomes difficult to distinguish the fillet slope portion and the land portion in the code pattern, and the solder fillet becomes difficult. There is an error in the calculation of the length and height of the fillet. The silk-printed part that is commonly used for substrates
If it exists in the area of the inspection window, it causes the same error. Further, as shown in FIG. 10, the resist printed surface around the soldering land on the board has a low level of all luminance signals. Is code No8
Is assigned. Therefore, when there is a positional deviation between the land and the inspection window due to the movement error of the table as shown in FIG. 11B, it is difficult to identify the fillet sloped portion and the resist portion as in the case of the copper foil. Therefore, an error occurs in the calculation of the length and height of the solder fillet. In order to solve the above-mentioned problems and to realize a higher performance visual inspection, it is necessary to generate a code for accurately describing the angle of the target surface regardless of the property of the target surface.

[0005]

In order to solve the above problems, a code generator 70 according to the present invention includes a threshold value determining unit 70-1 and a relative value determining unit 70-, as shown in FIG.
It is composed of two functions.

[0006]

The threshold value determining section has a function of performing code allocation depending on whether or not each video signal level exceeds a predetermined threshold value, thereby eliminating the conventional arithmetic processing.

[0007]

EXAMPLES Examples will be described below. In FIG. 12, the following code generation is performed after setting two types of threshold values Sa and Sb. (1) When the video signal level Si exceeds the threshold value Sa, the code is determined only by this Si. In the case of FIG. 12, this corresponds to the sections of a, c, e, and g, and the codes No1, No3, No5, and No7 are assigned to them, respectively. (2) If the two types of video signal levels Si1 and Si2 both exceed the threshold value Sb under conditions other than the above, the middle of Si1 and Si2 is assigned. In the case of FIG. 12, this corresponds to the section b which does not correspond to the condition (1) above, and the sections d and f among the sections B where S1 and S3 exceed Sb, respectively. , Codes No2, No4, and No6 are assigned. (3) If the video signal level Si exceeds the threshold value Sb under conditions other than the above, the code is determined only by this Si. In the case of FIG. 12, the sections corresponding to this are the sections of h and i, which are code No1 and No7, respectively.
Is assigned. (4) For conditions other than the above, that is, for the section j in the case of FIG. 12, the code 8 is assigned as an unknown region. As described above, according to the present invention, by setting the threshold value in consideration of the characteristic of the reflected light due to the multi-stage illumination, it is possible to appropriately generate the code without using the arithmetic processing. Next, the function of the relative value determination unit will be described. The level characteristics of the low-gradient fillet region and the copper foil surface shown from a to i in FIG. 10 are shown in FIG. 13 with S1 and S3 as indexes, and the level relationships are close or overlapping. It can be seen that it is difficult to distinguish between the two. The same applies to the silk-printed part. However, as shown in FIG. 14, "S1 + S3" and "S5 + S"
7 ”, it is understood that these areas can be easily identified by the coefficient Kc. Similarly, as shown in FIG. 15, if the levels are compared using S1 + S3 and S3-S5, it is found that the copper foil portion and the silk-printed portion can be further identified by the coefficient Ks. That is, by paying attention to a plurality of luminance signal relative characteristic relationships according to the property of the target surface, it is possible to perform accurate code generation regardless of the reflective property of the target surface. FIG. 16 shows an example of the code generation unit processing method including the functions of the threshold value comparison unit and the relative value determination unit described above. Such a function can be realized by either hardware means or software means. With the code generation method of FIG. 16, the code pattern in the case of FIG. 11A is improved as shown in FIG. 17, the copper foil flat portion and the solder fillet can be clearly identified, and the quality judgment can be accurately performed. Next, as shown in FIG. 10, the reflection characteristic of the resist printed surface around the land shows a characteristic similar to that of a fillet high gradient portion where the reflectance is generally low and the luminance level is generally lowered.
For this reason, as shown in FIG. 18, it is difficult to distinguish between the two based on the luminance signal level, and the situation is as shown as the distribution of the codes 8 in the code pattern of FIG. 11B. Therefore, it is necessary to identify such an object in consideration of the structural characteristics of the object to be inspected, rather than the identification at the luminance signal level. That is, when the solder fillet is considered as an inspection target, the pixel portion to which the code 8 is assigned is always adjacent to the pixel portion of the code 7 or 6 because the fillet has a high gradient. That is, after performing the code generation processing according to FIG. 16, if necessary, code regeneration may be executed for the pixel portion where the luminance signal is entirely low. As a method thereof, as shown in FIG. 12, a threshold value Sc is set, and when the adjacent code is No6 or No7 for the pixel portion where each luminance signal level is lower than this, No8 (processed as a high gradient portion), Code is originally No
The area of 8 or No. 4 or less is code Nor or No.
o (both are treated as flat portions). In FIG. 18 showing one embodiment of such processing, Ci is the pixel code of the address i, Ci-1 is the code number of the pixel of the address i-1, and SO = S3 + S5 + S7SC is shown in FIG.
As a result, as shown in FIG. 19B, the flat portion and the fillet portion can be easily identified, and the quality of soldering can be appropriately determined.

[0008]

As described above, according to the present invention, it is possible to generate an angle code signal that accurately describes a target surface shape from a plurality of target image information by switching a plurality of illuminators, and soldering can be performed. Industrially significant effects such as performance improvement and speed improvement in the appearance inspection device for fine and various glossy objects such as attachment. The basic principle of the present invention can be applied regardless of the number of stages of the illuminator, the structure method, and the type of the light receiving sensor. Further, although the embodiment has been described with respect to the 8-level coding system using the 4-stage illuminator, 4 levels or 1
There may be two levels of coding, etc. Further, it is obvious that various threshold values used for code generation can be changed by an external signal according to the type of the inspection target within the scope of the present patent system.

[Brief description of drawings]

FIG. 1 is a diagram showing a basic configuration of the present invention.

FIG. 2 is a diagram showing a basic system configuration of a multi-stage illumination type visual inspection device which is a specific object of the present invention.

FIG. 3 is an operation flowchart of the present invention.

FIG. 4 is a specific structural diagram of the optical unit of the present invention.

FIG. 5 is a diagram showing a reflection model of the optical system of the present invention.

FIG. 6 is a target surface reflection characteristic diagram of a conventional illuminator.

FIG. 7 is a model diagram of image information formation according to a conventional example.

FIG. 8 is a model diagram of image information formation according to a conventional example.

FIG. 9 is a model diagram of a code generation situation according to a conventional example.

FIG. 10 is a diagram showing the relationship between the type of target surface and brightness characteristics.

FIG. 11 is an explanatory diagram of a problem of code generation in the conventional method.

FIG. 12 is an explanatory diagram of the principle of the code generation method by the threshold value judgment in the embodiment of the present invention.

FIG. 13 is an explanatory diagram of a code generation method principle by relative value comparison in the embodiment of the present invention.

FIG. 14 is an explanatory diagram of the principle of a code generation method by relative value comparison in the embodiment of the present invention.

FIG. 15 is an explanatory diagram of the principle of a code generation method by relative value comparison.

FIG. 16 is an explanatory diagram of an embodiment of a code generation system according to the present invention.

FIG. 17 is an explanatory view of another embodiment of the present invention.

FIG. 18 is an explanatory diagram of a code refining generation method according to the embodiment of the present invention.

FIG. 19 is an explanatory diagram of effects of the present invention.

[Explanation of symbols]

 10 Inspection Target (Including Solder Joint of IC Lead) 8 Soldering Land on Printed Wiring Board 9 Printed Wiring Board 11 IC Lead 12 Solder Fillet for Joining the Land and Lead 13 Cross Section of the Fillet 20 Illuminator 21 Illumination Light 30 TV camera, etc. Light receiving sensor 130 Light receiving sensor output 50 Image pattern storage unit 150 Same output (image pattern) 70 Code generation unit 71 Same threshold comparison unit 72 Same relative value comparison unit 170 Code generation unit output (Code pattern) 100 Inspection window 101 Pixel part in the inspection window

Claims (4)

[Claims] 1. A threshold value when an output of a light receiving sensor for receiving reflected light from the inspection object is coded in an appearance shape inspection having a plurality of stages of illumination light sources having different projection angles to the inspection object. An appearance shape inspection device that generates a target surface description code by judgment and relative value judgment. 2. A plurality of sets of illumination light sources having different projection angles to the 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. , And 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, It is possible to recognize a three-dimensional shape of the inspection target based on a code signal generation unit that generates an angle code at each position of a two-dimensional region including the inspection target based on the above, and a distribution state of the generated code in the inspection region. A recognition surface processing code generating method for a target surface description code used in an appearance shape inspection apparatus having a different recognition processing apparatus, the code generation being performed by comparing the level of input information with a predetermined threshold value. Appearance inspection device characterized by having function. 3. A target surface description code generation method used in the appearance inspection apparatus according to claim 1, wherein specific one or a plurality of pieces of input information and one or a plurality of other pieces of input information are included. An appearance shape inspection device having a function of generating a code signal for describing input information when the input information has a predetermined level relationship. 4. A target surface description code generation method used in the appearance inspection apparatus according to claim 1, wherein the code generation for the inspection target area is once executed, and then a pixel portion within a predetermined range in the area. On the other hand, an appearance shape inspection apparatus having a function of executing code conversion with reference to the code generation result.