JPH03218405A - External appearance ininspecting method for soldering filet - Google Patents

Abstract

PURPOSE:To detect the position of a soldering filet by scanning a detection area in a search area and comparing the distribution state of luminance in the internal part of the detection area with the distribution state of luminance for a master picture. CONSTITUTION:On a base 1, a lead 3 is adhered to an electrode part 2 by a soldering filet 4 and the soldering filet 4 is irradiated with light from a light source 5 and observed by a camera 6. A search area A is set with a size to include the tip part of the lead 3 and the filet 4 and in the internal part of the area A, a detection area B is set with a size to include the filet 4 and scanned so as to detect the distribution state of the luminance in the area B at points P1, P2,... Pn. The distribution state of the luminance at each point is compared with the distribution state of the luminance for the master picture set in advance and the part of the low luminance in the detection area at the most matched point can be detected as the position of the soldering filet.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a solder fillet appearance inspection method. Specifically, the position of the solder fillet is first detected using an upper camera, and then the quality of the shape of the solder fillet is determined. Concerning methods for making decisions.

(Prior Art) A board to which electronic components are bonded using cream solder is then sent to a reflow device, where the cream solder is heated. FIGS. 8 and 9 show a side view of a conventional visual inspection means for a solder fillet heat-treated in this manner, and a plan view of the vicinity of the lead tip. lOO is the substrate, 101
is the lead, 102 is the solder fillet, 103 is the camera,
104 is a light source.

As shown in the figure, the upper surface of the solder fillet saw I-102 is a curved surface with a downward slope. When light is irradiated from above and observed by the camera 103 above, the light is reflected to the side, and the reflected light is not reflected by the camera 103. Since almost no light is incident, the base end 102a of the solder fillet 102 is observed darkly. Furthermore, since the tip 102b of the solder fillet 102 has a gentle slope close to horizontal, the reflected light is slightly reflected upward and enters the camera 103 to some extent, so that it is observed as a slightly light gray color.

Conventionally, the light reflection characteristics of the solder fillet 102 are used to set a check area 105 at a position where the solder fillet 102 is expected to exist, and the area S of this check area 105 and this 7 In the queria 105, the area Sx of the darkly observed portion (i.e., the proximal end 102a) is detected, and if Sx≧αS, it is determined that the solder fillet 102 is sufficiently formed and its shape is good. Ta. α is a constant determined by the required precision, and is, for example, 0.6.

(Problems to be Solved by the Invention) However, with the above conventional means, when the lead 101 is misaligned and the solder fillet 102 protrudes from the solder area 105, as shown by the broken line in FIG. Even if the shape of 1 0 2 is good, there is a problem in that it does not satisfy the above inequality and is erroneously judged as NG.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a solder fillet appearance inspection method that can solve the problems of the conventional methods described above.

(Means for Solving the Problems) To this end, the present invention provides the following features: (i) When observing a solder fillet for bonding an electrode portion of an electronic component to a substrate using an upper camera, (i) the electrode portion and the solder fillet are Along with setting a search area, (ii) setting a detection area inside this search area, and (iii) causing the detection area to scan inside the search area to determine the distribution of brightness inside the detection area at each point. (iv) Next, the brightness distribution state inside the detection area at each point is compared with the brightness distribution state of a preset master image, and (v) The part with low brightness is detected as the position of the solder fillet.

(Operation) According to the above configuration, the position of the solder fillet is detected by comparing the brightness distribution state inside the detection area of each point in the search area with the brightness distribution state of the master image, and then the solder fillet position is detected. Wetting length,
By determining the wetting area, it is determined whether the shape of the solder fillet is good or bad.

(Example 1) Next, embodiments of the present invention will be described with reference to the drawings.

Figure 1 is a side view of a state in which the appearance of the solder fillet of the lead electrode part of an electronic component such as a QFP or SOP is being inspected, and Figure 2 is a plan view, where ■ is on the board and 2 is on the board l. This is an electrode part of a circuit pattern formed on the electrode part 2, and a lead 3, which is an electrode part of an electronic component, is mounted on this electrode part 2. 4 is a solder fillet for bonding the lead 3 to the electrode part 2; this solder fillet 4 is irradiated with light from an upper light source 5 and observed by an upper camera 6 to judge whether the shape of the solder fillet 4 is good or bad. .

The upper surface of the solder fillet 4 is a curved surface with a downward slope and has specularity, so when irradiated with light from above and observed with the camera 6 above, the upper surface of the proximal end 4a of the solder fillet 4 has a steep slope. Therefore, the light is reflected to the side as shown by the arrow, and almost no one hits the camera 6.
Therefore, it is observed darkly by the camera 6, but since the tip portion 4b has a gentle slope close to horizontal, light is slightly reflected upward, and it is observed as a slightly bright gray color. Therefore, in the present invention, this darkly observed proximal end portion 4a is defined as the wetting portion (wet portion) of the solder fillet 4, and both portions 4a. The tangent angle θ of the surface of the solder fillet 4 at the boundary of the solder fillet 4b is defined as a welt angle, and the length l of the welt portion 4a on the equal dividing line N of the lead 302 is defined as a welt length. The magnitude of the welt angle θ that determines the boundary between the welt portion 4a and the tip portion 4b varies depending on the type of camera 6, but is generally about 15°. As will be described later, the quality of the shape of the solder fillet 4 is determined from the welt area and the welt length l of the welt portion 4a.

Next, the steps of the visual inspection method will be explained.

As shown in FIG. 2, a search area A including the tip of the lead 3 and the solder fillet 4 is set. The size of the search area A is set so that even if the lead 3 is slightly misaligned, the tip of the lead 3 and the solder fillet 4 can be sufficiently contained therein.

Also, inside this search area A, a detection area B is set. The size of this detection area B is considerably smaller than the search area A, but is set to a size that can include the solder fillet 4.

Next, the search area A is scanned with the detection area B to detect the luminance distribution state inside the detection area B at each point Pi P2 . . . Pn.

FIG. 3 shows the distribution of brightness at point Px. In the figure, the part surrounded by the thick line a corresponds to the tip of the lead 3, and is observed brightly with a luminance of 47 or higher. Also, in the figure, the part surrounded by the thick line b is the lead 3
This is the part corresponding to the solder protruding from the side of the lead 3 and the wetting part 4a at the tip of the lead 3.As mentioned above, the light irradiated from above is reflected to the side and almost all of the light is not incident on the camera 6. Therefore, it is observed darkly with a luminance of 4 or less. The part surrounded by the thick line C corresponds to the tip 4b, and is observed as a slightly bright gray color with a luminance of about 11 to 17. Further, the part surrounded by the line d corresponds to the electric scratching part 2 on the board 1 side and the top surface of the board l, and has a brightness of 48
It is observed brighter than above. Note that FIG. 5 shows the brightness of each part as a gray scale.

FIG. 4 shows the brightness distribution state of the preset master image. The brightness distribution state of this master image is determined by selecting an image in which there is no displacement of the lead 3 and having a good shape of the solder fillet 4, and observing it in advance.

Next, the brightness distribution state of the detection area B at each of the above points l-PI to Pn is compared with the brightness distribution state of the master image, and the point where the brightness distribution state is most massotized (point Px in this example) is determined. demand. This matching is performed, for example, using the following equation.

In the above formula, Pn,m is the brightness of each pixel n,m in the vertical and horizontal directions N,M in the detection area B, Rn,m is the brightness of each pixel n,m in the master image, and the average value is calculated. In order to do this, it is divided by 64x(nm). Note that the calculation formula is not limited to the above formula, for example, Pn,
You may also calculate the square of the difference between m and Rn,m, or 64
It is not necessary to divide by X(n-m); in short, any calculation means that can detect the most masocing point is sufficient.

Once the position of the point Px that is most marked is determined as described above, the darkest observed part (the part with a brightness of 7 or less) in the detection area B of this point Px is the wetting area of the solder fillet 4. It is detected as part 4a.

Once the position of the welt portion 4a has been determined as described above, the area of the welt portion 4a is determined from the number of pixels with a brightness of 7 or less, and The wetting length l is determined from the number of pixels. Next, based on this area and the size of the welt length l, it is determined whether the shape of the welt portion 4a is good or bad.

(Embodiment 2) FIG. 6 shows the appearance inspection of solder fillets of electronic components such as capacitor chips, resistor chips, and 7 chips. In this electronic component 10, electrode portions 12 and 13 are formed on both sides of the molded body 1l. 14.
15 is a solder firento, which irradiates light from above,
When observed with the upper camera 6, it is observed as shown in FIG.

Similarly to the first embodiment, this search area A is set so that it can sufficiently cover the electrode portion 12.13 and the solder fillet 14.15 even if the electronic component 10 is slightly misaligned. By setting detection area B within area A and scanning this detection area B, detecting the brightness distribution state of each point P1 to Pn and comparing it with the brightness distribution state of the master image. The position, welt area, welt length, etc. of the fillet 14 and 15 are calculated.

In this example, the shape of the solder fillet 14 on the right side is good and has a welt portion 14a that is observed darkly and a tip portion 14b that is observed gray, but the shape of the solder fillet 15 on the left side is good. is defective, and dark, gray, and light portions 15a, 15b, and 15c are observed in a ring shape.

(Effects of the Invention) As explained above, according to the present invention, the position of the wetting part of the solder fillet can be reliably determined, and then from the wetting area and the wetting length of this wetting part, the shape of the solder fillet is good or not. Therefore, the appearance inspection of the solder fillet can be performed reliably and accurately.

Figure 1 is a side view of a solder fillet during visual inspection, Figure 2 is a plan view of the same, Figure 3 is a brightness distribution diagram, Figure 4 is a brightness distribution diagram of the master image, Figure 5 is a grayscale diagram, and Figure 6 is a diagram of the brightness distribution of the master image. FIG. 7 is a side view and a plan view of another embodiment during external inspection,
8 and 9 are a side view and a plan view during appearance inspection by conventional means.

■・・・Substrate 3,12.13... Electrode part 414.15...Solder fillet 6...Camera 10...Electronic parts A...Search area B...Detection area

Claims (3)

[Claims] (1) When observing the solder fillet that bonds the electrode part of the electronic component to the board with the camera above, (i) setting a search area that includes the electrode part and the solder fillet, and (ii) this search area. (iii) scan the detection area within the search area to detect the luminance distribution state inside the detection area at each point; (iv) then set the detection area at each point. Compare the internal brightness distribution state with the brightness distribution state of a preset master image, and (v) Detect the part with low brightness in the detection area of the most matched point by the above comparison as the position of the solder fillet. A solder fillet appearance inspection method characterized by: (2) In the solder fillet appearance inspection method set forth in claim 1, from the length on the bisector of the electrode portion of the portion with low brightness detected in the above (v), A method for visually inspecting a solder fillet, characterized in that the quality of the shape of the solder fillet is determined by detecting the wetting length of the solder fillet. (3) In the solder fillet appearance inspection method described in claim 1, by detecting the wetting area of the solder fillet from the area of the portion with low brightness detected in the above (v). , a solder fillet appearance inspection method characterized by determining whether the shape of the solder fillet is good or bad.