JP2009276208A - Visual inspection method for mounting substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform quality determination, simply, with sure reliability, as to inspection for determining the quality of soldering for a circuit element, and especially, of soldering by means of a soldering robot or by means of manual work using a soldering iron. <P>SOLUTION: As shown in Fig. 1 (A), a resistance 3 disposed on a green substrate 2 is photographed by a camera (imaging device) 4 disposed above the resistance 3 while the resistance 3 is illuminated via a special filter 6 made of milk-white acrylic by red coaxial illumination 5 from the camera 4 side. An image obtained by the photographing is black-and-white binarized to determine the quality of soldering. This method makes it possible to perform determination without being affected by flux 9 covering fillets 8 as shown in Fig. 1 (B). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an appearance inspection method for determining whether a circuit element such as an IC chip, a capacitor, or a resistor mounted on a printed circuit board is soldered.

There is a conventional method for inspecting whether circuit elements such as an IC chip, a capacitor, and a resistor are well soldered to a printed circuit board (Non-patent Document 1). As shown in FIG. 4A, in this example, the resistor 101 is disposed on the substrate 100, and the camera (imaging device) 102 disposed above the resistor 101 causes white coaxial illumination from the camera 102 side. (Top illumination) A method of taking a picture while irradiating with 103 and determining whether soldering is good or bad is employed. Reference numerals 104a and 104b are white middle illumination and white bottom illumination, respectively, for preventing shadows from being produced. As shown in detail in FIG. 4B, the resistor 101 to be inspected in this example has leads (electrodes) 101 a and 101 b of the resistor 101 inserted into holes of the substrate 100, respectively, on the back surface of the substrate 100. A portion (hereinafter referred to as a fillet) 105 formed by solder is formed around the protruding leads 101a and 101b on the protruding side, and the shape of the fillet 105 is that of each of the leads 101a and 101b. The lead 101a and 101b gradually expand toward the rear surface of the substrate 100 from the tip portion protruding from the rear surface of the substrate 100 to form a substantially triangular pyramid shape. Such a fillet 105 images the resistor 101 formed on the leads 101 a and 101 b with the camera 102. Then, as shown in FIG. 4B, the light reflected by the back surface of the substrate 100 returns to the camera 102, but the light reflected by the fillet 105 does not return to the camera 102. For example, the fillet 105 of the lead 101a is When a photograph is taken and the photographed image is shown by binarization processing of black and white (in the case of binarization, the black and white of the video is reversed), as shown in FIG. A fillet image is obtained. Therefore, the black image, (in the figure, indicated by the area S ₁ surrounded by a rectangle of white lines) given rectangle predetermined number of pixels forming the white image (due to the imaging of the fillet 105) in the In other words, the quality of soldering is determined using a predetermined threshold value.

However, this method is used when the inspection target is a reflow soldering process in which the amount of flux (contained in order to improve the properties of the solder, which includes pine yarn, etc.) is small. For example, when soldering is performed manually using a soldering robot or a soldering iron, a large amount of flux scatters around the fillet and hardens like glass at room temperature. For example, as shown in FIG. 6 (A), the flux 106 is formed in a manner of being laminated on the fillet 105 formed around the leads 101a and 101b of the resistor 101, and in an uneven shape. When the resistor 101 having such a fillet 105 or flux 106 is photographed by the camera 102, for example, when viewing the lead 101a of the resistor 101, the light reflected by the flux 106 is reflected by the camera 102 as shown in FIG. There are things that return to (for example, arrow a ₁ ) and things that do not return (for example, arrows b ₁ , c _1, etc.). 2 When shown by binarization, as shown in FIG. 6 (B), the black image, in the predetermined rectangular S ₁ previously determined, or scattered white mottle x is black in white image In other words, it is possible to obtain a pattern in which the uneven pattern y is scattered. For this reason, there exists a problem which cannot judge the quality of soldering with the predetermined threshold value set.
VISION TESTER ESV-304 HS Catalog New Electronics Co., Ltd. April 2006

  The problem to be solved is simple and reliable reliability in the inspection of the soldering of circuit elements, particularly in the judgment of the quality of manual soldering using a soldering robot or a soldering iron. The point is that it is possible to make a pass / fail judgment.

  According to the first aspect of the present invention, there is provided an appearance inspection method for determining whether soldering is good or not when a circuit element such as an IC chip, a capacitor, or a resistor is mounted on a green circuit board by soldering. In this method, the imaging device is arranged above the circuit element, and the circuit element is photographed while irradiating red light from the imaging device side through a special filter such as made of milky night acrylic. The captured image is binarized and compared with a predetermined threshold value to determine pass / fail. This type of inspection method is simple and reliable with respect to soldering pass / fail. This is a method that can be determined.

  The mounting board appearance inspection method according to the present invention is an inspection method for photographing while irradiating red light through a special filter. Therefore, the mounting board appearance determination method is simple, and the quality of soldering is determined with certainty. be able to.

An apparatus for realizing a mounting board appearance inspection method according to an embodiment of the present invention will be described with reference to FIGS.
As shown in FIG. 1A, the appearance inspection apparatus 1 takes the resistor 3 in order to image a resistor (circuit element) 3 of the same type as that of the conventional example, which is disposed on a general green substrate 2. The camera (imaging device) 4 disposed above the camera 4, the red coaxial illumination (top illumination) 5 disposed immediately below the camera 4, and the milk filter acrylic special filter disposed below the coaxial illumination 5 6 is used to judge whether soldering is good or bad by photographing while irradiating with the red coaxial illumination 5. Here, the reason why the filter 6 is interposed is that the direct illumination of the coaxial illumination 5 is too strong and is affected by the reflected light. Reference numerals 7a and 7b are white middle illumination and white bottom illumination, respectively, for preventing shadows from being produced.

  By the way, the resistor 3 to be inspected is disposed so as to protrude from the back surface of the substrate 2 by inserting the leads 3a and 3b of the resistor 3 into the holes of the substrate 2 as shown in detail in FIG. The leads 3a and 3b are disposed around the protruding leads 3a and 3b from the tip portions of the leads 3a and 3b protruding from the back surface of the substrate 2 toward the back surface of the substrate 2. A fillet 8 having a substantially triangular pyramid shape is formed in a progressively divergent manner around the periphery of the film, and a flux 9 is formed in an uneven shape and in an uneven shape. . Even if the fillet 8 is formed with such a flux 9, there is no problem as long as the fillet 8 itself is good.

Next, a quality determination method for soldering using the appearance inspection apparatus 1 will be described.
With this device 1, the camera 3 photographs the resistance 3 in which such fillets 8 and flux 9 are formed on the leads 3 a and 3 b. At this time, for example, the reflection state of the light beam from the coaxial illumination 5 around the lead 3a of the resistor 3 will be described. As shown in FIG. Since it is good, it passes through the flux 9 and is reflected by the substrate 2 and returns to the camera 4. Further, the light beam b passes through the flux 9 and is reflected by the fillet 8 and does not return to the camera 4. Further, the light beam c passes through the flux 9 and is reflected by the substrate 2 and returns to the camera 4 in the same manner as the light beam a. Further, the light beam d is reflected by the substrate 2 and returns to the camera 4 as a matter of course. Under such a situation, an image captured by a light beam b that does not return to the camera 4 is captured in a dark color. In addition, in the imaging where light rays a, c, d and the like returning to the camera 4 are connected, the irradiated light rays a, c, d are red and the substrate 2 of the irradiated object is green, so-called subtraction. Due to the nature of the color mixture, the amount of light returning to the camera 4 is reduced and the image is taken dark. When the image captured in the dark color is shown by the binarization processing of black and white (in the case of the binarization, the imaging black and white is inverted), as shown in FIG. A pure white image is obtained over the predetermined rectangle (indicated by a section S surrounded by a black line rectangle in the figure). This is because such an image is obtained when the soldering is good, and therefore it is possible to determine whether the soldering is good or not without being affected by the flux 9.

  By the way, as shown in FIG. 3A, when there is a soldering failure of the resistor 3, for example, the lead 3b, that is, the flux 9 is applied to the land (copper foil for soldering) 10 on the substrate 2 of the lead 3b. If the fillet 8 is formed but not formed, when this is photographed by the camera 4, a white image captured by the light beam e reflected back from the land 10 is obtained (by the light beam f or the like). The connected image is captured in a dark color as described above), and this is shown by a black and white binarization process (in the case of binarization, the black and white of the image is reversed), as shown in FIG. As shown in B), for example, a black image (by imaging of the land 10) z is shown in a predetermined rectangle S of the white image, so that it can be determined that there is a soldering defect in the lead 3b.

  The present invention makes it possible to make a pass / fail judgment simply and with a certain degree of reliability in an inspection for judging pass / fail of any soldering including manual soldering using a soldering robot or a soldering iron. It can be said that it can be widely used for this kind of inspection.

It is a schematic block diagram of the apparatus which implement | achieves the external appearance inspection method which concerns on embodiment of this invention. It is an image figure when the imaging which image | photographed the soldering non-defective product with the apparatus of FIG. It is explanatory drawing at the time of image | photographing the soldering defect goods with the apparatus of FIG. It is a schematic block diagram of the conventional external appearance inspection apparatus. FIG. 4 is an image diagram when the image captured by the apparatus of FIG. 3 is subjected to black and white binarization processing. FIG. 4 is an image diagram when the image captured by the apparatus of FIG. 3 is subjected to black and white binarization processing.

Explanation of symbols

1 Visual inspection device 2 Green substrate 3 Resistance (circuit element)
4 Camera (imaging device)
5 Red coaxial lighting 6 Special filter

Claims (1)

  An external appearance inspection method for determining whether soldering is good or not when a circuit element such as an IC chip, a capacitor, or a resistor is mounted on a green circuit board by soldering, and an imaging device is disposed above the circuit element And imaging the circuit element while irradiating red light from the imaging apparatus side through a special filter, and binarizing the captured imaging and comparing with a predetermined threshold value to determine pass / fail A mounting substrate visual inspection method.

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