JP3031956B2 - Solder amount inspection method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for inspecting the amount of solder in a soldered portion in the field of image processing.

[Prior Art] Patent applicant filed Japanese Patent Application No. 2-2749 (Japanese Patent Application Laid-Open No. 3-206907).
No.) proposed a solder inspection method. The solder inspection method irradiates the surface of the soldering portion formed between the lead end and the conductive pattern by irradiating the irradiation light by switching from different directions, and illuminating the surface of the soldering portion for each illumination light. Before and after the switching of the illumination light, the shape and amount of the soldering portion are estimated from the moving direction and the moving amount of the two luminescent spots, and the quality is determined.

[Problems of the prior art]

If the soldering portion is always adhered to the end surface of the lead to a fixed height position, the above-mentioned method makes it possible to grasp the shape of the solder and the amount of solder almost exactly. However, when the position of the solder with respect to the end surface of the lead changes in the height direction of the lead, that is, in the thickness direction, the shape and amount of the solder can be accurately determined only by the moving direction and the moving amount of the bright spot before and after the switching of the illumination light. It becomes impossible to discriminate, and the reliability of the test result decreases.

In addition, a concave surface rather than a convex surface tends to be used as a good surface form of the soldered portion. Also, due to conditions at the time of soldering, in particular, soldering temperature and supply control of the amount of solder, etc. Are increasing in shape.

[Object of the invention]

Therefore, an object of the present invention is to make it possible to accurately grasp the amount of solder in the field of image processing irrespective of a change in the attachment position of the soldering portion to the lead end surface, targeting the concave soldering portion. is there.

[Solution Means and Action of the Invention]

To this end, the solder amount inspection method of the present invention provides an image processing system in which illumination light is switched from different directions onto a surface of a soldered portion formed between an end portion of a lead and a conductive pattern and irradiated. While using the conventional basic principle of generating a bright spot for each illumination light on the surface of the soldering portion, the amount of movement of the two bright spots before and after the switching of the illumination light, and each bright spot from the end face of the lead. The average distance to a point is measured in the field of image processing, and the amount of soldering is determined from the measured value and a relational expression of the amount of solder corresponding to the measured value.

Here, the amount of movement of the luminescent spot and the amount of soldering for a certain average distance from the end face of the lead to each luminescent point are determined by the relational expression as described above. In addition to the volume calculation formula obtained by the above, a data table which is previously tabulated as volume data by actual measurement or the like is included.

According to this solder amount inspection method, the soldering amount can be accurately detected as long as the surface shape of the soldering portion is concave, even if the position of attachment of the soldering portion to the lead end surface changes in the thickness direction.

〔Example〕

 FIG. 1 shows an outline of the image processing system 1.

The soldering portion 2 to be inspected is formed as a concave surface between the end face of the lead 3 such as an IC package and the conductive pattern 4 such as a circuit board, and the light sources 5a and 5b as irradiation means slightly obliquely upward. Is switched, the light is radiated by irradiation light in different directions, and bright points Ra and Rb are generated on the surface thereof for each of the illuminating lights. The two light sources 5a and 5b are selectively switched by a switching device 14 as switching means.

The soldering section 2 is converted from an optical image into an electric image by the upper imaging camera 6, and is converted by the A / D converter 7.
The analog signal is converted into a digital signal and stored in the image memory 8. Here, the imaging camera 6 and the A / D converter 7 constitute an imaging unit.

Then, the image processing is performed by the CP connected to the memory 10, the display 11, the input unit 12, and the like as storage means.
It is executed by U (central processing unit) 9. Here, the CPU 9 also serves as an image processing unit and a calculation unit. These are controlled by the control circuit 13 under sequence control (synchronization / interrupt control).

When the soldering part 2 to be inspected is positioned within the field of view of the imaging camera 6, the imaging camera 6 photographs the soldering part 2 to be inspected together with the lead 3 and a part of the conductive pattern 4, and converts the optical image into an electric image. The analog image signal is converted into a digital image signal by the A / D converter 7 and then stored in the image memory 8. In the first imaging, the illumination light from one light source 5a is used, and in the next imaging, the illumination light from the light source 5b is used.

In each photographing process, as shown in FIG. 2, the bright spots Ra and Rb are generated at different positions on the surface of the soldering part 2, so that the illumination light is switched from the light source 5a to the light source 5b. The bright spot Ra appears to move to the position of the bright spot Rb. The image memory 8 stores images including these bright points Ra and Rb, respectively.

In the subsequent image processing stage, the CPU 9 executes the image processing program, cuts out only the soldered portion 2 to be inspected as a window having a size of, for example, about 40 × 40 [dots], and outputs the image by the light source 5b. Of the image by the light source 5b, the position thereof is determined, and the movement amount d of both the bright points Ra and Rb, and the respective bright points Ra, The average distance x to Rb is determined in image processing from the number of dots and the like.

Thereafter, the CPU 9 determines the values of the movement amount d and the average distance x after the measurement and the soldering amount Q set in advance for each of these values.
The soldering amount Q of the soldering portion 2 to be inspected is determined from the relational expression. Here, the movement amount d and the soldering amount Q corresponding to the average distance x are set in advance as a data table based on a relational expression, that is, a volume calculation expression obtained by theoretical calculation, or experimental data, and stored in the memory 10 or the like. Have been. Therefore, the CPU 9 calculates the movement amount d on the image.
After the determination of the average distance x, the soldering amount Q is determined from the position where the corresponding numerical value coincides with the calculation based on the volume calculation formula or with reference to the data number table.

Note that the ridge line of the soldering portion 2 differs depending on the lead shape, the material of the conductive pattern, and the like, but generally, as shown in FIG.
It can be approximated by a curve of Y = be- ^ax . The movement amount d
Is increased as the value of the point b with respect to the Y axis decreases as shown in FIG. Therefore, the movement amount d and the average distance x are used as elements for determining the curve.

〔The invention's effect〕

In the present invention, the form of the soldering part is specified based on the movement amount of the bright spot on the surface of the soldering part formed by the illumination light from different directions and the average distance from the lead end face to each bright spot. Since the amount of soldering is determined from the relational expression, even if the attachment position of the soldering portion changes in the thickness direction of the lead end face, the amount of soldering can be grasped almost accurately regardless of the change, and the amount of soldering can be reduced. Inspection reliability is increased.

[Brief description of the drawings]

FIG. 1 is a block diagram of the image processing system, FIG. 2 is an enlarged plan view of a soldering portion, and FIG. 3 is a graph of a curve on a surface of the soldering portion. DESCRIPTION OF SYMBOLS 1 ... Image processing system, 2 ... Soldering part, 3 ... Lead, 4 ... Conductive pattern, 5a, 5b ... Light source, 6 ... Imaging camera, 7 ... A / D converter, 8 ... Image memory, 9
... CPU (central processing unit), 10 ... memory, 11 ...
Display, 12 Input unit, 13 Control circuit,
14 ... Switch.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-67949 (JP, A) JP-A 1-219547 (JP, A) JP-A-3-206907 (JP, A) JP-A-2-206 234053 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01N 21/84-21/958 H05K 3/34 G01B 11/24

Claims (1)

(57) [Claims] 1. A storage means for previously obtaining a relational expression for calculating a soldering amount from a movement amount of a bright point and an average distance from an end face of a lead to each bright point, and storing the obtained relational expression;
Illumination means having different directions for irradiating the surface of the soldering portion formed between the end of the lead and the conductive pattern, switching means for switching the illumination means, and light generated on the surface of the soldering portion by the illumination means Imaging means for taking in an image of a bright point into an image memory; image processing means for obtaining the moving distance of the bright point before and after switching of the illumination light and the average distance from the end face of the lead to each bright point by image processing; Calculating means for calculating the amount of soldering by referring to the above relational expression from the amount and the average distance from the end face of the lead to each bright spot; and the lighting means, the switching means, the imaging means, the image processing means and the calculating means. In an image processing system comprising control means for controlling the sequence of operations, the illumination light from the illumination means is applied to the surface of a soldered portion formed between the end of the lead and the conductive pattern. The illumination is switched by the switching means from a certain direction, and a bright point is generated for each illumination light on the surface of the soldering portion, and the two bright points before and after the switching of the illumination light are taken into the image memory by the imaging means. A solder amount inspection method, wherein the image processing means and the arithmetic means determine a soldering amount based on a movement amount of the two bright points and an average distance from an end face of the lead to each bright point.