JPH02206709A - Solder fillet inspection device - Google Patents

Abstract

PURPOSE:To decide the propriety without scarcely requiring human intervention by detecting the dislocation of a soldered part from the image signal of a front fillet image by an image processor, allowing a positioning controller to execute a position correction and deriving the degree of deformation of a fillet shape from the image signal of a side face fillet image. CONSTITUTION:An image processor brings the front fillet image of a soldered part 4 to image pickup from an image signal, and controls a positioning device 9 so that an image come exactly to an alignment reference in a visual field. Subsequently, a light source 5-1 is turned off, and a fiber illuminator 6-1 is operated. A light beam radiated from the fiber illuminator 6-1 is reflected by a reflecting mirror 6-2, and also, diffused by an optical diffusion plate 6-3, and illuminates the soldered part 4 from the side face. The light beam which transmits through the outside of the soldered part 4 is reflected to an image pickup device 7 by a reflecting mirror 6-4, a fillet image seen from the side face is brought to image pickup by the image pickup device 7 and inputted to the image processor 8, and the device 8 compares the pattern of an inputted side face silhouette image with the pattern of a reference silhouette and evaluates the degree of deformation, and decides the quality of the soldered part 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] This invention relates to a solder fillet inspection device that determines the acceptability of the fillet shape of a soldered portion on a printed circuit board.

The purpose is to completely automate the inspection of the bouillette shape of the soldering part and enable high-quality and highly efficient inspection.

a first optical means that indirectly illuminates the soldered portion of the component lead through the printed circuit board to generate a front fillet image of the soldered portion; The image processing device includes a second optical means for generating the front fillet image, an imaging device for capturing the front fillet image and the side fillet image and converting them into image signals, an image processing device, and a printed circuit board positioning device. The positional deviation of the soldered part is detected from the image signal of the fillet image, and the positioning control device performs position correction, and the degree of deformation of the fillet shape is determined from the image signal of the side fillet image, and the quality is judged.

[Industrial application field]

The present invention relates to a solder fillet inspection device that determines the quality of the fillet shape of a soldered portion of a component lead on a printed circuit board used in information equipment such as computers and various home appliances.

Visual inspection of the soldered parts of parts bonded on printed circuit boards is becoming more and more important as the density of printed circuit boards rapidly increases.

Automation is strongly desired in terms of both inspection accuracy and inspection speed, and it is necessary to replace the conventional ambiguous sensory inspection conducted by visual inspection by an operator with a high-speed, high-precision automatic inspection using inspection equipment. To provide useful inspection equipment.

[Prior art and problems to be solved by the invention] Fig. 9 is a cross-sectional view of the soldered portion of a component soldered to a printed circuit board, where 1 is a printed circuit board, 2 is a component, and 3 is a soldered part of a component soldered to a printed circuit board.
is a lead, and 4 is a soldered part.

The leads 3 of the component 2 pass through holes in the printed circuit board 1 and are joined to the printed circuit board 1 by soldering portions 4 on the back side. The cross section of the soldered part 4 is shown with diagonal lines, and when soldered normally, its fillet shape (shape with flesh) has an appropriate inclination angle as shown in Figure 1. It has a beautiful conical shape.

On the other hand, FIG. 10(a) shows an example of the fillet shape of the soldered portion when inappropriate soldering is performed.

Mountain 1. +c+ shows (al, tbl, (cl
In each case, the solid line figure is a cross-sectional image of an inappropriate solder fillet shape.

The dotted line figure shows a cross-sectional image of a suitable solder fillet shape. Of these, fat is an example of insufficient solder.

The bonding strength is low and can easily cause connection failures (also known as peaks)
C1 is an example of excessive solder, which tends to bridge with other wiring parts and cause poor insulation, and (C1 is an example of solder chipping or poor wetting, which is likely to cause poor connection as in (a). .

Conventionally, defects in these soldered parts were discovered by visual inspection of the fillet shape, but this had the following problems.

111 Occurrence of Inspection Errors Due to inspector fatigue and monotony, defective areas are easily overlooked or misunderstood.

(2) Variation in Inspection Standards Inspection standards vary among inspectors, and even among the same inspectors, they vary over time, making it difficult to obtain high reliability.

(3) Inspection speed There are many inspection points and high-speed inspection is difficult for humans.

(4) Inspection Accuracy Human inspection resolution is relatively low, and inspection accuracy cannot be improved.

Therefore, it is an object of the present invention to completely automate the inspection of the fillet shape of the soldered part, thereby completely automating the inspection of the fillet shape of the soldered part, thereby enabling high quality and highly efficient inspection. do.

[Means to solve the problem]

The present invention is equipped with means for detecting a front silhouette image of the soldering part viewed from directly above and a side silhouette image of the soldering part viewed from the side.First, the front silhouette image is detected and positioned, and then the side silhouette image is detected. The present invention aims to solve the above-mentioned problems by realizing an inspection device that detects images and determines the quality of fillet shapes.

FIG. 1 is a diagram showing the basic configuration of a solder fillet inspection device according to the present invention.

In FIG.

■ is a printed circuit board.

2 is one part.

3 is a lead for three parts.

4 is a soldering part.

5-1 is a light source for obtaining a front fillet image.

5-2 is a condensing lens.

5-3 is a mask that is opaque at the center and transparent at the periphery.

5-4 is a projection lens.

6-1 is a fiber illuminator for obtaining a side fillet image.

6-2 is a nine-reflection mirror.

6-3 is a light diffusing plate.

6-4 is a two-reflection mirror.

7 is an imaging device such as a video camera for inputting the fillet image as an image signal.

8 is an image processing device that detects the position of the soldering part 4 and the degree of deformation of the fillet image.

Reference numeral 9 denotes a three-dimensional positioning device that performs movement control to set each soldering portion 4 on the printed circuit board 1 to an inspection position.

Note that each of the elements 5-1 to 7 is integrally constructed.

Further, by arranging a plurality of sets of elements 6-1 to 6-4 at equal intervals on the same circumference (for example, three sets), it is possible to obtain fillet images from a plurality of directions.

[Effect]

In FIG. 1, the inspection device is first placed at
In order to control the positioning directly above the two soldering parts 4, the light source 5-1 is turned on.

The light emitted from the light source 5-1 is passed through the condenser lens 5-2. Mask 5-3. The printed circuit board 1 is irradiated through each projection lens 5-4. in this case.

Due to the effect of the opaque part at the center of the mask 5-3, the soldered area 4 is not directly irradiated from directly above, but the light transmitted from the peripheral area of the soldered area 4 into the printed circuit board as shown in FIG. The soldering part 4 is indirectly illuminated from the back in such a way that the light is re-radiated. The light emitted from the printed circuit board 1 in this manner forms a front silhouette image of the soldering portion 4, and the imaging device 7 images this and sends an image signal to the imaging device 8.

The image processing device identifies the front fillet image of the soldering portion 4 from one image signal, as shown in FIG.

The positioning device 9 is controlled so that this fillet image accurately aligns with the alignment reference within the field of view.

Next, the light source 5-1 is turned off and the fiber illuminator 6-1 is operated. The light emitted from the fiber illuminator 6-1 is reflected by a single reflection mirror 6-2.

The light is further diffused by the light diffusing plate 6-3 and illuminates the soldering portion 4 from the side. The light transmitted through the outside of the soldering part 4 is reflected by the single reflection mirror 6 - 4 to the imaging device 7 , and a fillet image seen from the side is captured by the TI imaging device 7 and input to the image processing device 8 .

As illustrated in FIG. 10, the fillet image viewed from the side shows that the soldering of the soldered portion 4 exhibits various patterns depending on the state. The image processing device 8 evaluates the degree of deformation by comparing the input side silhouette image pattern with a reference silhouette image pattern as shown in FIG.
The quality of the soldered part 4 is determined.

When the fillet images on the side surface of the soldered part 4 are detected from a plurality of directions, the degree of deformation of each fillet image pattern is evaluated, and the quality of the soldered part is determined overall.

〔Example〕

FIG. 5 is an overall configuration diagram of a solder fillet inspection apparatus according to an embodiment of the present invention.

In FIG.

10 is an xyz table.

11 is a printed circuit board.

I2 is a soldered part to be inspected.

Reference numeral 13 denotes a first optical system that indirectly illuminates the soldering portion 12 from the printed circuit board 11 in order to take a front fillet image of the soldering portion 12 viewed from directly above.

14 is a second optical system that transmits illumination of the soldered part 12 in order to collect a side fillet image of the soldered part 12 viewed from the lateral direction; It includes a fiber illuminator, a corresponding reflecting mirror, and a light diffusing plate (detailed configuration will be described later with reference to FIG. 6).

15 is a video camera.

Reference numeral 16 denotes nine image processing sections, which are composed of an A/D converter 16a1, an image memory 16b, a processing section 16c, and a RAM 16d.

17 is a system control unit.

18 is a table control unit that controls the three-dimensional movement of the xyz table 10.

FIG. 6 is a detailed configuration diagram of the second optical system 14 in FIG. This makes it possible to obtain side fillet images of.

The elements of these three optical systems are identified by reference numbers with the suffixes a, bC, respectively, and the respective transmitted illuminations achieved are represented by arrows AB,C. Here, 14-18 to 14-IC are fiber illuminators, 14-2a to 14-2c are reflection mirrors that direct the light incident from the fiber illuminators 14-1a to 14-IC toward the side surface of the soldering part 12, and 143a to 14-3c are reflective mirrors 14-2a to 1, respectively.
A light diffusion plate that converts the light reflected by 4-2e into diffused light,
14-4a to 14-4C are light diffusing plates 14-, respectively.
reflective mirrors 14-58 to 14-5c for reflecting the diffused light from 3a to 14-3c through and illuminating the soldering portion 12 and the light transmitted to the opposite side toward the video camera 15;
shows side fillet images obtained in three directions, respectively.

Next, the functions of the image processing section 16 shown in FIG. 5 will be explained.

The image signal of the front fillet image or each side fillet image outputted from the video camera 15 is an analog format signal, which is converted into a multilevel digital signal by the A/D converter 16a and stored in the image memory 16b.

The processing unit 16C binarizes the multivalued digital signal in the one-image memory 16b and stores it in the RAM 16d.

For binarization, first, the values (density values) of the multivalued digital signal are identified pixel by pixel, a density histogram is created, and the optimal slice level for separating the fillet image area and the surrounding area is determined. Second, this slice level is compared with the multilevel digital signal to perform binarization processing.

Figure 7 shows an example of a method for binarizing a multi-value digital signal using a density histogram. ) is a density histogram of a multivalued digital signal of a side fillet image captured by transmitted illumination. The horizontal axis represents the brightness level, the vertical axis represents the number of pixels, and the shaded area represents pixels in the fillet image (silhouette).

The areas without diagonal lines correspond to each group of pixels in the remaining part of the field of view, and TI and T2 indicate determined slice levels.

In the case of indirect illumination shown in figure (al), the level of the light re-emitted from the printed circuit board is lower than that of the light emitted from the light diffuser plate in the case of transmitted illumination shown in (bl).

In the case of the density histogram in Fig. 1al, since the surface filling of the soldered part is known, the number of pixels in the density histogram is calculated from the darker level, and the pixel level when it matches the area of the soldered part is calculated. This is determined as the slice level TI. In addition, in the case of the density histogram (return), the slice level T2 is set approximately at the center of the two peaks.

By determining the slice level and performing binarization using such a method, it becomes possible to perform optimal binarization depending on the state of the printed circuit board.

The image processing unit 16 further performs alignment, calculation of the degree of deformation of the fillet image, and determination of the quality of the soldered portion using the binarized image data.

The operation of the embodiment apparatus shown in FIG. 5 will be explained according to the flow of the inspection process shown in FIG.

■ Hold the printed circuit board 11 on the XYZ table 10 with the soldered side facing up, and the system control unit 17:
Instruct the table control unit 18.

The XYZ table 10 is moved so that the optical axes of the video camera 15 and the first optical system 13 coincide with one soldering part 12 to be inspected.

■ Turn on the light source of the first optical system 13 and turn on the 2 indirect lighting
Make it. At this time, the transmitted illumination by the second optical system is OFF.
It is.

■ The front silhouette image of the soldering part 12 is the video camera 1.
5, and the image signal is sent to the system control unit 1.
The image is captured into the N image processing unit 16 by an image capture signal (not shown) from 7. This image signal is A/D converted by the A/D converter 16a as described above and stored in the 1-image memory 16b.

■ The image data in the multivalued digital signal format stored in the image memory 16b is represented by, for example, 8-bit density, and the processing unit 16C counts the number of pixels for each density level and calculates the number of pixels as shown in FIG. 7 (al). Create a density histogram as shown.

From now on, as described above, determine the slice level T1, binarize the image data, find the centroid position of the group of 1" pixels in the binarized image data, and calculate the difference with the alignment standard shown in Fig. 3. seek.

This difference is sent to the table control section 1B via the system control section 17, and one position correction is performed. Also after this,
The second optical system 14 is lowered to the printed circuit board surface.

(2) Select transmitted illumination A for the second optical system 14 shown in FIG.

■ Turn on the fiber illuminator (one of 14-1a to 14-1c in Figure 6) corresponding to the selected transmitted illumination,
Turn it on. At this time, indirect illumination by the first optical system 13 is turned off.

(2) A side fillet image based on transmitted illumination is captured by the video camera 15, and the image data is captured into the image memory 16b of the 1-image processing unit I6 in response to an image capture signal from the system control unit 17.

(2) The processing section 16c of the image processing section 16 creates the density histogram shown in the seventh output from the nine image data, determines the slice level T2, and binarizes the image data.

Next, the contour line of the side fillet image is obtained and the degree of deformation such as the slope and complexity of the three curves is quantified. In this case, techniques commonly used in the general pattern recognition field are used.

■ Store data on the imaging direction and degree of deformation in RAMl6d.

(2) The first step is divided into one of Φ' and Φ'[F] depending on whether the transmitted illumination selected immediately before is A, B, or C.

Select Φ′ transmitted illumination B and return to step (■).

■Select #transmitted illumination C and return to ■.

Therefore, the deformation degree data of the side fillet images obtained from each imaging direction are comprehensively evaluated, and defects such as insufficient solder, excessive solder, chipping, and insufficient wetting are detected.

■ Output the data when a defect is detected.

[Phase] The system control unit 17 executes an inspection by repeating the process from ■ for all soldered parts,
The process ends when all tests are completed.

[Effects of the Invention] According to the present invention, it is possible to quickly and accurately inspect the fillet shape of the soldered portion of a printed circuit board without requiring much human labor, thereby improving reliability and reducing costs. reduction is possible.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the basic configuration of the present invention, Fig. 2 is an explanatory diagram of indirect illumination for obtaining a front fillet image in the configuration of the present invention shown in Fig. 1, and Fig. 3 is an explanatory diagram of positioning control according to the present invention. , FIG. 4 is an explanatory diagram of a reference side silhouette image according to the present invention, FIG. 5 is a configuration diagram of a solder fillet inspection apparatus according to an embodiment of the present invention, and FIG. 6 is an illustration of the second optical system in FIG. A detailed configuration diagram, FIG. 7 is an explanatory diagram of a method for binarizing a multilevel digital signal, FIG. 8 is a flow diagram of an inspection process according to an embodiment of the present invention, and FIG. 9 is a cross-sectional view of a soldered part on a printed circuit board. FIG. 10 is an explanatory diagram showing an example of an inappropriate fillet shape of a soldered portion. In Figure 1. 1 Niblint board 4: Soldering part 5-1: Light source 5-3: Mask 6-1: Fiber illuminator 6-2.6 = 4: Reflection mirror 6-3: Light diffusing plate 7: Lifting device 8: Image Processing device 9: Positioning control device

Claims (1)

[Claims] In a solder fillet inspection device for determining the quality of soldered parts of component leads on a printed circuit board,
) to indirectly illuminate the soldering part (4).
A first optical means (5-1) for generating a front fillet image of
~5-4), and a second optical means (6-1 to 6-4) that transmits and illuminates the soldering part (4) from the side to generate a side fillet image of the soldering part (4), An imaging device (7) that captures a front fillet image and a side fillet image and converts them into image signals, and an image processing device (
The image processing device (8) detects the positional deviation of the soldering part (4) from the image signal of the front fillet image and controls the positioning control device (9). ), the solder fillet inspection device is characterized in that it performs position correction, determines the degree of deformation of the fillet shape from the image signal of the side fillet image, and determines the quality of the fillet.