JPH04350506A - Method for inspecting lead soldering and solder surface - Google Patents

Abstract

PURPOSE:To enable whether soldering state is proper or not to be judged accurately by setting a height for obtaining a section in height direction for a group of legs which are aligned in one line and then comparing the number of sections which were obtained with the number of legs at the time of an improved packaging soldering. CONSTITUTION:An image processing part 5 sets a leg group inspection region based on a leg group inspection region data which is taught previously. A height of a substrate height detection point of a printed wiring board is measured, thus enabling a height H0 of the substrate to be set. An offset height di for obtaining a sectional image of a lead leg which is set previously is added to the height H0, thus enabling a level H1 for obtaining the sectional image to be determined. A height data within an inspection region is binary coded in reference to the level H1 and an area of each binary-coded image is counted. The number of sections which are larger than an area which is taught previously out of this area value is counted. These processings are executed for all sectional images. The number of sections of this counted digitized image is compared with the number of reference legs within the inspection region which was taught previously and then soldering failure is determined when it is not equal to a reference.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a lead soldered portion of a flat package IC mounted and soldered on a printed wiring board using a three-dimensional image obtained by a measuring device that determines the height by optical triangulation. This invention relates to a solder surface inspection method for inspecting solder surfaces.

0002

[Prior Art] Inspection of the lead soldering portion of a flat package IC mounted and soldered on a printed circuit board is performed by applying a light to detect high-intensity points seen in the solder fillet, as disclosed in Japanese Patent Application Laid-Open No. 1-260586. Inspection has been carried out by detecting the lead, or by projecting a line light parallel to the side surface of the lead, as disclosed in Japanese Patent Laid-Open No. 2-216005, and inspecting the state of the waveform of the cutting line.

0003

[Problems to be Solved by the Invention] However, with these conventional methods, the high brightness point and its light intensity are not stable depending on the shape and surface condition of the solder fillet, and the distinction between flux and solder cannot be determined based on the external shape. Therefore, there was a problem in that it was not possible to accurately inspect the lead soldering portions of flat package ICs.

The present invention has been provided in view of the above-mentioned points, and it is possible to accurately determine the soldering state by three-dimensionally measuring the lead soldering portion of a flat package IC mounted and soldered on a printed wiring board. The object of the present invention is to provide a solder surface inspection method that allows for accurate quality determination.

[0005]

[Means for Solving the Problems] The present invention provides a three-dimensional image obtained by three-dimensionally measuring the lead soldering portions of a row of lead legs of a flat package IC mounted and soldered on a printed circuit board. After binarizing the height image based on the height of the printed circuit board within the inspection area that includes all the foot groups set in advance, count the number of lands and compare them with the reference value. If they are not equal, it is considered a soldering defect. It is characterized by the following.

[0006] According to a second aspect of the present invention, in an inspection area including a binarized image obtained by binarizing the height image, a middle position of the area is set as a lead tip edge search line, and an edge is found by differentiating the height on the line. This method is characterized in that if no edges are found during processing, the solder shape is determined to be good. In claim 3, in a three-dimensional image obtained by three-dimensionally measuring the lead soldering portion of a flat package IC mounted and soldered on a printed wiring board, a point slightly returned to the lead side from the lead tip edge is detected. This method is characterized in that the height of the tip of the lead leg is determined from the height, and the quality of the floating lead leg is determined by comparing it with a reference height.

Further, in claim 4, in a three-dimensional image of a lead soldering part of a flat package IC mounted and soldered on a printed wiring board, the height and brightness of the measurement location are measured by a measuring device that measures the height and brightness. measure the
The feature is that solder and flux are distinguished from this height and brightness to judge whether the soldering is good or bad. In claim 5, the quality of soldering is determined by measuring the amount of light in a direction parallel to the lead end surface of a flat package IC mounted and soldered on a printed circuit board, using the height and brightness data obtained by the measuring device. It is characterized by determining.

[0008] In claim 6, the ends of the soldered parts at the tips of the leads are measured on a three-dimensional image obtained by three-dimensionally measuring the soldered parts of the leads of a flat package IC mounted and soldered on a printed circuit board. The quality of the solder amount is determined by excluding the solder amount and measuring the amount of solder on the printed wiring board in the lead width direction. In claim 7, when an edge is found in claim 2 after the inspection of the foot group according to claim 1,
Tests according to claims 3 to 6 are carried out.

[0009]

[Operation] Then, for the three-dimensional image of the flat package IC obtained by three-dimensional measurement, the height for obtaining a cross-section in the height direction of the legs arranged in a row is set, and the obtained cross-section is Compare the number of legs with the number of legs during good mounting soldering,
In order to judge the quality of soldering, it is possible to judge the quality of soldering in a short time without considering misalignment of the object to be measured.

In claim 2, the inspection area of each solder joint is determined from the cross-sectional image obtained in claim 1 with respect to the three-dimensional image obtained by three-dimensional measurement, and the height of the area on the center line is determined. If the lead tip edge cannot be found in the process of finding the lead tip edge using the differentiation of can be done.

[0011] According to claim 3, the edge is determined by the process of determining the lead tip edge described in claim 2 for a three-dimensional image obtained by three-dimensional measurement, and the height near this edge is determined as the height of the lead tip. By doing so, it is possible to accurately determine lead foot floating defects. In claim 4, if the relationship between the height data near the lead tip and the brightness data in the three-dimensional image and brightness image obtained by optical three-dimensional measurement is higher than the standard if the measurement target is solder. If the brightness is lower than the standard brightness, and if the flux is higher, it is brighter than the reference brightness, so from this characteristic, the shape of the solder joint and the quality of the constituent materials can be determined at the same time.

[0012] In claim 5, a plurality of inspection points are set near the lead tip for the brightness image obtained by optical three-dimensional measurement, and the brightness data is used to determine the shape of the solder joint. The degree of solder wetting can be determined by Claim 6
In the three-dimensional image obtained by three-dimensional measurement, the shape near the lead corner changes due to the influence of the joint shape on the side of the lead, and the amount of solder at the lead tip cannot be measured within a stable range. By measuring the solder amount at the center excluding the solder joints near the lead corners and determining the quality, the solder amount can be accurately inspected.

[0013] According to the seventh aspect, since the three-dimensional image and the brightness image obtained by optical three-dimensional measurement are used, it is possible to accurately determine the quality of the soldered portion, and to accurately determine the quality of the soldered state.

[0014]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 11 shows the configuration of an inspection system that employs the method of the present invention, and FIG. 12 shows an overall flowchart of the inspection system. A three-dimensional image detection device 1 is a device for three-dimensionally measuring, by optical triangulation, a lead soldering portion of a flat package IC mounted and soldered on a printed wiring board.

This three-dimensional image detection device 1 shines a spotlight from directly above on the height of a lead soldering portion on a printed wiring board to be inspected, detects the spot light from an oblique direction, and detects the height of the lead soldered portion on a printed wiring board to be inspected. The height is measured using a configuration in which the height is the position of the upper spot light, and three-dimensional data is obtained by moving the printed wiring board using the moving mechanism 2 and changing the measurement location.

Furthermore, brightness data can be obtained by measuring the amount of spot light when the height is determined. The three-dimensional data is stored in the image memory 3, and the brightness data is stored in the image memory 4. The image processing section 5 performs an inspection judgment on a series of legs of the flat package IC, and the image processing section 6 determines an inspection area to be used. Further, the image processing section 6 performs inspection and determination of each lead soldering part within the inspection area determined by the image processing section 5.

The movement control section 7 controls the movement mechanism 2, and the overall control section 8 controls the three-dimensional image detection device 1, the image memories 3 and 4, the image processing sections 5 and 6, and the movement control section 7. It controls the entire system including the section 7. Next, an embodiment of the inspection method of the present invention using the above system will be described based on a flowchart.

First, the flat package IC 10 (FIG. 2
) The image processing unit 5 that performs an examination on a group of feet arranged in a row will be described based on the flowchart shown in FIG. The image processing unit 5 starts processing in step 100, and in step 101 sets a foot group inspection area based on the foot group inspection area data taught in advance. Step 1
In step 02, the height of the board height detection point of the printed wiring board is measured to determine the board height H0. Next, in step 103, a preset offset height di for obtaining a cross-sectional image of the lead leg is set to the substrate height H0.
, and determine the level H1 at which the cross-sectional image is obtained.

In step 104, the height data in the foot group inspection area is binarized based on level H1, and step 1
05, the area of each binarized image is counted. In step 106, if this area value is smaller than the previously taught area for determining noise, it is not used as a cross-sectional image. In step 107, the number of cross sections that satisfy the conditions in step 106 is counted up. These processes are executed for all cross-sectional images.

The number of cross sections of the binarized image counted in step 109 is compared with the reference number of legs within the inspection area taught in advance, and if the number is not equal to the reference, the number of sections between the legs as shown in FIG. 2(a) is compared. It is determined that the soldering is defective because a bridge has occurred or the leg has come off due to a mistake during mounting as shown in (b). Next, in step 110, a circumscribed rectangle of each cross section is found, and as shown in FIG. The inspection area is shown in the inspection flowchart for each lead in FIG. 3.

Next, the solder surface inspection method for each lead by the image processing section 6 will be explained based on the flowchart of FIG. The process starts in step 200, and in step 201, the center line of each lead-specific inspection area determined by the image processing section 5 is determined. In step 202, as shown in FIG. 4(a), the tip edge of the lead 11 is moved to the starting point
From, the current point i on the center line and the forward point j
In step 203, if the difference is larger than a value that can be considered as a lead tip edge, point i is determined as an edge.

If it is not determined to be an edge, move the current reference point i to the forward point j used in step 202, and repeat steps 202 and 203 until the forward point reaches the end point q of the center line. If no edge is found, the shape changes smoothly from the lead 11 to the soldered part of the solder 12 as shown in FIG. 4(b), so in step 207, this soldered shape is determined to be a good product. do.

If an edge is found, the height of the point that is back above the lead by dL from the edge is determined in step 208, as shown in FIG. In step 210, the difference between the height of the printed wiring board 13 and the height of the lead tip is determined. In step 211, to check for lead foot floating,
The lead tip height is compared with a pre-taught lead foot reference height, and if the measured value is greater than the reference value, it is determined to be defective.

[0024] Here, this measuring device can measure height and brightness optically using the principle of triangulation using a laser spot light with a minute diameter. Because most of the components are the same, internal reflection of the target occurs due to differences in the transmittance of the light from the target, increasing or decreasing the amount of light of the diffuse component, and differences in the direction of specular reflection occur depending on the shape within the laser spot diameter, resulting in diffuse reflection. Differences in brightness may occur even at the same height due to changes in the amount of component light.

Using these measurement results, the solder wetting test shown in FIG. 7 will be explained based on the flowchart shown in FIG. Processing begins at step 300. Solder 1 located dL2 away from the lead tip edge in step 301
An inspection line for measuring brightness data is set at the wetted area of step 2.

In step 302, height data on the inspection line is measured, and in step 303, brightness data on the inspection line is measured. In step 304, the height data is compared with a preset solder wetting reference height, and if it is larger, it is determined that the soldering shape is good, and if it is good, the brightness data is preset in step 305. The test line is compared with a brightness standard value for good soldering, and if the brightness on the inspection line is below the brightness standard value that is considered to be solder, it is determined that it is solder.

Next, in step 307, the lead 1 is attached to the wetted part of the solder 12, which is dL3 away from the lead tip edge.
An inspection line for measuring solder wetting defects that occur parallel to the lead end surface from the brightness data is set with a length that divides the lead end width into three equal parts. As mentioned above, the brightness of the flat part is brighter than that of the convex part, so in step 308 the brightness of each inspection line is measured, and in step 309 it is compared with the preset brightness reference value of the solder wetting part. Comparison is made, and if it is below the reference value, it is determined that the wettability is good.

Next, the determination of the quality of the amount of solder in the solder joint will be explained based on the flowchart shown in FIG. Processing begins at step 400. As shown in FIG. 9, the solder 12 is bonded at the tip end surface of the lead 11 or at the side surface of the lead 11, and in order to judge the quality based on the amount of solder in the inspection area determined by the image processing unit 5, it is necessary to In order to eliminate changes in the amount of solder within an area due to solder joints and to accurately judge the quality of the solder amount, it is necessary to exclude the solder near the lead tip corners from the solder amount measurement target.

Therefore, in step 401, as shown in FIG. 10, dL4 and dL5 are
Reduce the inspection area to the inside and set the solder amount measurement area. In step 402, the difference between the height data of each height measurement point in the solder amount measurement area and the substrate height is determined, and the total is determined as solder. In other words, the amount of solder is calculated by multiplying the area area and height.

[0030] In step 403, the amount of solder is compared with a preset good solder reference value, and if it is less than the reference value, it is determined that the amount of solder is insufficient.

[0031]

Effects of the Invention As described above, the present invention provides a three-dimensional image of a flat package IC obtained by three-dimensional measurement.
In order to determine the quality of soldering by setting the height for obtaining a cross section in the height direction for a group of legs arranged in a row, and comparing the number of obtained cross sections with the number of legs during good mounting soldering,
This has the effect that the quality of mounting soldering can be determined in a short time without considering misalignment of the object to be measured.

In claim 2, the inspection area of each solder joint is determined from the cross-sectional image obtained in claim 1 with respect to the three-dimensional image obtained by three-dimensional measurement, and the height on the center line of the area is determined. If the lead edge cannot be found during the process of determining the lead tip edge using differentiation, it can be determined that the solder is attached smoothly. Therefore, preprocessing that performs inspection based on the lead tip edge can determine the quality of the soldered shape. This has the effect that it can be done.

In claim 3, the edge is determined by the process of determining the lead tip edge described in claim 2 for a three-dimensional image obtained by three-dimensional measurement, and the height near this edge is determined as the height of the lead tip. By doing so, it is possible to accurately determine lead foot floating defects. In claim 4, if the relationship between the height data near the lead tip and the brightness data in the three-dimensional image and brightness image obtained by optical three-dimensional measurement is high when the measurement target is solder, the reference brightness is determined. If the flux is higher than the reference brightness, it is brighter than the standard brightness.This feature has the effect that the shape of the solder joint and the quality of the constituent materials can be determined at the same time.

[0034] In claim 5, a plurality of inspection points are set near the lead tip for the brightness image obtained by optical three-dimensional measurement, and the brightness data is used to determine the shape of the solder joint. This has the effect that the degree of solder wetting can be determined by. In claim 6, the shape of the vicinity of the lead corner changes due to the effect of the joint shape of the side surface of the lead on the stereoscopic image obtained by three-dimensional measurement, and the amount of solder at the lead tip cannot be measured within a certain stable range. By measuring the amount of solder at the center, excluding the solder joints near the lead corners, as the amount of solder at the tip of the lead and determining pass/fail, the amount of solder can be accurately inspected.

[0035] According to claim 7, when an edge is found in claim 2 after the inspection of the foot group according to claim 1, the inspection according to each of claims 3 to 6 is carried out, thereby performing optical three-dimensional measurement. Since the three-dimensional image and the brightness image obtained by the method are used, it is possible to accurately determine the quality of the soldered portion, and the soldered state can be accurately determined.

[Brief explanation of drawings]

FIG. 1 is a flowchart of a foot group test according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a lead foot group test.

FIG. 3 is a flowchart of a lead leg floating test.

FIG. 4 is an explanatory diagram of lead tip edge detection.

FIG. 5 is an explanatory diagram of a lead leg floating test.

FIG. 6 is a flowchart of solder wetting inspection.

FIG. 7 is an explanatory diagram of a solder wetting test.

FIG. 8 is a flowchart of solder amount inspection.

FIG. 9 is an explanatory diagram of lead bonding.

FIG. 10 is an explanatory diagram of solder amount measurement.

FIG. 11 is a block diagram of the entire inspection system.

FIG. 12 is a flowchart of the entire inspection system.

[Explanation of symbols]

10 Flat package IC 11 Lead 12 Solder 13 Printed wiring board

Claims (7)

[Claims] Claim 1: All the foot groups preset on a three-dimensional image obtained by three-dimensionally measuring the lead soldering portions of a row of lead foot groups of a flat package IC mounted and soldered on a printed circuit board. After binarizing the height image with reference to the height of the printed wiring board within the inspection area including the printed wiring board height, the number of lands is counted and compared with a reference value, and if they are not equal, it is determined that the soldering is defective. Soldering inspection method. 2. In an inspection area including a binarized image obtained by binarizing the height image, the middle position of the area is set as a lead tip edge search line, and the edge is 2. The solder surface inspection method according to claim 1, further comprising determining that the solder shape is good if the solder surface is not found. 3. With respect to a three-dimensional image obtained by three-dimensionally measuring the lead soldering part of a flat package IC mounted and soldered on a printed wiring board, a point slightly returned to the lead side from the lead tip edge is shown. A solder surface inspection method characterized by determining the lead foot tip height from the height and comparing it with a reference height to determine whether the lead foot is floating. 4. Measure the height and brightness of the measurement point in a three-dimensional image of the lead soldering part of a flat package IC mounted and soldered on a printed wiring board, which is measured by a measuring device that measures the height and brightness. , a solder surface inspection method characterized by identifying solder and flux from the height and brightness and determining the quality of soldering. 5. Based on the height and brightness data obtained by the measuring device, the amount of light in a direction parallel to the lead end surface of a flat package IC mounted and soldered on a printed wiring board is measured to determine whether the soldering is good or not. 5. The solder surface inspection method according to claim 4, further comprising the step of determining: . 6. A three-dimensional image obtained by three-dimensionally measuring the soldered parts of the leads of a flat package IC mounted and soldered on a printed wiring board, excluding the ends of the soldered parts at the tips of the leads. A solder surface inspection method characterized by determining the quality of solder amount by measuring the amount of solder on a printed wiring board in the lead width direction. 7. Claim 1, characterized in that when an edge is found in claim 2 after the foot group inspection according to claim 1, the inspections according to each of claims 3 to 6 are performed.
The solder surface inspection method described in ~6.