JPS61293659A - Method for inspecting soldering appearance - Google Patents

Abstract

PURPOSE:To inspect the deviation and soldering condition of packaged parts with high accuracy by providing two windows to the soldering parts to be inspected and inspecting the soldering condition from the sum and ratio of the measurement areas in the respective windows. CONSTITUTION:The soldered parts 5 of chip parts 4 packaged and soldered onto a printed wiring board 6 are subjected to falling illuminating 3 via the two windows 2 provided above said parts. A television camera picks up the image thereof and applies a signal to a binary coding part 11. The signal is compared with the a prescribed binary coding threshold level in said part and is converted to the binary coded image. The image is inputted to an area measuring part 13. The area of the binary coded image within the region assigned by a window generating part 12 is measured in the part 13. The output from the part 13 is inputted to an arithmetic discrimination part 14 where the measured value is compared with the value stored in a standard table 15 and the normality or abnormality is discriminated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a method for inspecting the appearance of soldering on a printed wiring board using a television camera to inspect the condition of soldering.

(Background technology) When automatically soldering printed wiring boards on which components are mounted,
Abnormalities occur with soldering such as insufficient solder or excessive solder, so it is necessary to inspect the soldering condition after mounting.

Generally, visual inspection is carried out manually, but since the judgment criteria are not constant depending on the operator, there is no big difference in the judgment criteria for abnormal soldering such as missing solder, but there is no big difference in the judgment criteria. There was a drawback that if delicate soldering such as insufficient solder or excessive solder became abnormal, a large difference would occur, making it impossible to conduct accurate inspections.

On the other hand, in some cases mechanical visual inspections are also carried out.
There were problems with inspection accuracy for subtle soldering abnormalities such as insufficient solder or excessive solder.

(Object of the Invention) The present invention has been proposed in view of the above points, and its purpose is to accurately inspect whether the amount of solder is too much or too little in the soldering area on a printed wiring board. The objective is to provide an inspection method.

(Disclosure of the Invention) The basic feature of the present invention is that soldering is performed by setting in-toes independently at the center and outer edges of the inspection area, and measuring the area of the binarized image using epi-illumination in each window. By using the sum of the values and their ratio, it is possible to check whether the amount of solder is too much or too little.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to drawings showing embodiments.

FIG. 1 shows the configuration of an inspection device embodying the present invention. In the figure, 4 is a chip component that is mounted and soldered on a printed circuit board 6, and the soldering is performed by epi-illumination 3 on the part 5 from above by the illumination part 2, and from further above the illumination part 2. A television camera 1 is arranged to take an image. The signal from the television camera 1 is given to the binarization unit 11, where it is compared with a predetermined binarization threshold level and converted into a binarized image.
The output is input to the area measuring section 13, and the area measuring section 13 measures the area of the binarized image within the area designated by the window generating section 12. Next, the output of the surface S measurement section 13 is input to the calculation/judgment section 14, which compares the measured value with the value stored in the standard table 15 to determine whether it is normal or not.
It is designed to determine abnormalities and output the determination results. Note that 10 is a control section that controls the operation of each section.

When epi-illumination 3 is applied to the illumination unit 2 and the chip component 4 is imaged and binarized with a television camera 1, as shown in FIG. A flat metal part like this is obtained as an image. In the case of obvious solder shortage (Fig. 2 C), a single window is set at the inspection point as in the past, and a judgment can be made based on the size of the measured area value, but in the case of a subtle solder shortage (Fig. 2 B) In such cases, the area alone indicates normal soldering (Figure 2 A).
cannot be distinguished and cannot be determined.

Therefore, in the present invention, in the case of slight solder shortage (Figure 2B) or excess solder (Figure 2D), the third As shown in figure (a), soldering is performed independently on the outer edge and center of the window a,
By setting b, the accurate soldering state is detected from the area value of the image within each inspection window.

Specifically, surface 8 in Figure 1! In measurement 13, the areas of the binarized images in the outer edge window ram and the center window b are simultaneously measured, and from the obtained areas S, , Sl, the first
The calculation/judgment unit 14 shown in the figure performs the following processing to make a determination.

■Sum of areas S of windows a and b, , s' 5iib.

and measurement area S in windows a and b, sum S of pS5
seek.

■ Find the ratio S/S of the measured area sum S to the window area sum S of the inspection location, and if this value is larger than the standard value α, the soldering is determined to be abnormal (obvious solder shortage (Fig. 2 C).
)in the case of. ) If the sum of the measured areas S is smaller than the standard value α and the measured area Sb at the center is smaller than the standard value β, it is determined to be normal (if the soldering is normal (Fig. 2 A)).

) ■If the sum of the measurement areas S is small but the measurement area Sl at the center is large, the measurement surface 'IaSI at the center.

The ratio of the measured area S, of the outer edge to S, /S.

If this value is larger than the standard value γ, it is determined to be normal, and if it is smaller, it is determined to be abnormal.

In other words, Fig. 3 (B) shows the state of the binarized image within the inspection window in each case of A, B, and C in Fig. 2, and the area of the binarized image is overwhelmingly large in solder deficiency C. Therefore, it can be determined by the process of ■ above, and normal A and insufficient B
is the surface 81If of the binarized image! Although it is not possible to distinguish between the two, in the case of deficiency B, the ratio S, /Sb of the measured area S of the outer edge to the measured area Sb of the center becomes small, so it is normal A.
can be clearly distinguished.

The flow of the above calculation and determination process is shown in FIG.

(Effects of the Invention) As described above, in the present invention, soldering is performed at two locations to be inspected.
Two windows were set up, and the soldering condition was inspected based on the sum of the measured areas and the ratio of the measured areas within each window. Therefore, in addition to inspecting for abnormal soldering, noticeable soldering such as lack of solder is also detected. , it becomes possible to inspect subtle soldering abnormalities such as excessive solder, and
Since the algorithm is simple, it has the effect of allowing high-speed inspection.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of the detection/judgment mechanism, Figure 2 is the state of each solder on a chip component and the binary image detected at that time, Figure 3 is an example of a window and a binary image detected within the window, Figure 4 is a flowchart of calculation judgment line processing. 1...TV camera, 2...Lighting section,
3... Epi-illumination, 4... Chip parts,
5... Soldering part, 6... Printed wiring board, 7... Reflected light, 10... Control part,
11...Binarization section, 12...Window generation section, 13...Area measurement section, 14...
...Calculation judgment section, 15...Standard table

Claims (1)

[Claims] In a method of inspecting the soldering condition on a printed wiring board, an inspection window is set up in advance at the inspection location, with the center and outer edges separated, and a binarized image of the image obtained from a television camera is used with epi-illumination. Measure the binarized image area within the inspection window, and calculate the ratio of the sum of the measured areas within each inspection window at the center and the outer edge to the sum of the window areas,
A soldering appearance inspection method characterized by inspecting whether a soldering condition is normal or abnormal based on the ratio of the measured area within an outer edge inspection window to the measured area within a central inspection window.