JPH04355311A - Device for detecting lift of lead of surface-mount ic - Google Patents

Abstract

PURPOSE:To enable a lift of lead after soldering to be detected highly reliably by using a lighting device which causes positive reflection to be produced when a soldering surface is flat for an image pick-up device and an lighting device which causes positive reflection to be produced when a soldering surface is at a certain inclination angle and then by picking up a soldering portion at a tip of a lead of a surface-mount IC. CONSTITUTION:A CPU 8 selects or switches an upper-stage lighting 12 and a lower- stage lighting 13 through an external equipment control unit 9 for using lightings with different angles, allows an image or reflection lights 17 and 18 which are reflected from a surface of a solder fillet 15 to be picked up by a TV camera 1 and to be input to and recorded at a memory 10 through an image input/output unit 7. An image according to lighting is read out of the memory 10 and the fillet 15 is segment into an inclined surface portion and a flat portion. Then, the CPU 8 performs a second-order approximation of a boundary between the inclined surface portion and the flat portion by an expression. It examines whether the second-order coefficient of the obtained second-order curve is equal to or less than a certain value or not and then determines that the product is a confirming article without any failure such as non-connection and lift of lead in the case of YES in the above.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic component mounting board inspection apparatus, and more particularly to an automatic inspection of lead floating states of multi-pin surface mount components mounted on a board.

0002

2. Description of the Related Art Conventional soldering visual inspection apparatuses inspect the presence or absence of solder, excess or deficiency of solder, but do not detect changes in soldering patterns due to floating leads of multi-pin surface mount components.

0003

[Problems to be Solved by the Invention] In the above-mentioned prior art, detection of floating leads after soldering was not considered.

SUMMARY OF THE INVENTION An object of the present invention is to provide a surface mount IC lead floating detection device that can detect lead floating after soldering with high reliability in order to solve the problems of the prior art. .

[0005]

[Means for Solving the Problems] The above object is to provide an illumination device that has an illumination angle that causes specular reflection when the solder surface is flat with respect to the imaging device, and a lighting device that has an illumination angle that causes specular reflection when the solder surface is flat with respect to the imaging device. By using a lighting device that causes specular reflection at certain times to image the soldered area at the tip of the lead of a surface-mounted IC, and detect the distribution state and distribution area of the flat and sloped areas in the soldered area. achieved. That is, the present invention includes a positioning device for a printed circuit board, a device for capturing an image of the printed circuit board, a circuit for inputting an image captured by the image capturing device to a control device, and a circuit for controlling the positioning device and processing the input image. A system comprising a control device and an illumination device with different irradiation angles on the inspection surface side of the board surface,
Surface mount IC that is the object to be inspected in the captured image
This is a lead floating detection device for a surface mount IC, which detects a lead floating state based on a two-dimensional distribution state of a constant slope of a solder surface of a lead tip in the image.

[0006]

[Operation] Lifting of the leads of multi-pin surface mount components causes problems such as unsoldered connections on the corresponding leads during component mounting, and problems with connection strength even when electrical connections are made. Lifted leads of multi-pin surface mount components are measured as irregularities in the lead rows, but after soldering and mounting, inspection is required from the viewpoint of the soldered connection state.

[0007] The above-mentioned lead misalignment of multi-pin surface mount components is caused by surface mount component mounting machines that have a function to measure the misalignment before mounting, but as mentioned above, the connection state after soldering However, there remains a possibility of soldering defects due to floating leads, and detection of floating leads after soldering has been an issue in achieving highly reliable soldering inspection. .

Therefore, in the present invention, an illumination device has an illumination angle that causes regular reflection when the solder surface is flat with respect to the imaging device, and a lighting device that has an illumination angle that causes specular reflection when the solder surface is flat with respect to the imaging device. Lighting devices that cause reflections are
The flat and sloped parts of the soldered parts at the tips of the leads of a surface-mounted IC are revealed. The distribution of flat parts and sloped parts of the soldering part differs as follows when the lead part is in contact with the soldering pad part on the board and when the lead is separated from the soldering pad part. When the lead portion is in contact with the soldering pad portion on the substrate, as shown in FIG. 3, the sloped portion of the solder is distributed near the tip of the lead and on the side surface of the soldering pad. When the lead floats from the soldering pad portion while maintaining the solder connection, the solder is sucked between the lead and the pad, and an inclined portion is distributed around the lead, as shown in FIG. When the lead is completely separated from the soldering pad and the solder connection is broken, and the solder spreads over the entire pad, the sloped portion of the solder is distributed around the edge of the pad, as shown in FIG. Even if the lead is completely separated from the soldering pad and the solder connection is broken, if the solder does not spread over the entire pad as shown in Figure 5, a flat part will be detected between the sloped part of the solder and the lead. . In this way, in the lead floating state, the distribution state of the flat part and the slope part of the soldering part is different, so the method of making this change in the distribution state obvious is to use quadratic curve approximation of the slope distribution area and the slope area and the slope area. Lifting of the leads can be detected by measuring the area of the flat area between the leads.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings showing examples. FIG. 1 shows the configuration of a lead floating appearance inspection device embodying the present invention. 4 is a printed circuit board to be inspected, on which a flat package 5 to be inspected is mounted and soldered. A printed circuit board 4 to be inspected is placed on an XY table 3 and moved according to an inspection sequence. 2 is for illuminating the object to be inspected; the illumination device has an illumination angle that causes specular reflection when the solder surface is flat with respect to the imaging device, and the illumination device has a certain inclination angle where the solder surface is relative to the imaging device. It consists of a lighting device that sometimes causes specular reflection, and is installed above the substrate as shown in FIG. 1 is a TV camera, which images the part to be inspected of the printed circuit board illuminated by the illumination 2;
The image signal is input to the image input unit 7. 3 XY
Table control and lighting control of the lighting device 2 are processed by an external device control unit 9. 6 is a control device of this system, 8 is a CPU, 10 is a memory, and 11 is a bus.

FIG. 2 is a sectional view of the leads and soldered parts. 14 is a lead, 18 is a soldering pad, and 15 is a solder fillet. Reference numeral 12 denotes an illumination device that has an illumination angle that causes specular reflection when the solder surface is flat with respect to the imaging device, and 13 refers to an illumination device that causes specular reflection when the solder surface has a certain inclination angle with respect to the imaging device. It is. Illumination light 17 from the illumination 12 is reflected by the flat part of the solder surface, and is imaged by the TV camera above as a bright part with strong reflection. Illumination light 16 from the illumination 13 is reflected by the slope of the solder surface, and is imaged by the upper TV camera as a bright portion with strong reflection. In the soldered part 15 in the captured image, the parts brightened by the illumination 12 and the parts brightened by the illumination 13 are identified and classified as normal soldering states without floating leads, and the results are shown in FIG. 3(c). Shown below. FIG. 3(a) is a rattan diagram of a normal soldering shape without floating leads, and FIG. 3(b) is a sectional view of a normal soldering shape without floating leads. When the lead portion is in contact with the soldering pad portion on the substrate, the solder shape is as shown in FIG. 3(a), and the sloped portion of the solder is distributed near the tip of the lead and on the side surface of the soldering pad. Figure 3(c)
19 is a sloped portion, and 20 is a flat portion. In a normal soldering state without floating leads, the contour line of the pad tip side of the sloped part 19 (the negative Y direction side of the Y coordinate shown in FIG. 3(d)) (hereinafter this is simply referred to as the contour line of the sloped part) ) is shown in 21 in FIG. 3(d). In the normal state, the contour line 21 is convex toward the lead side, and this is quadratic approximated as shown in Fig. 3.
If expressed as a quadratic equation in the X, Y coordinate system shown in (d), Y=
A×X×X + B×X + C… (Formula 1
), and if TH is the threshold value for A in a normal state, it can be said that there is no lead floating when A≦TH.

When the lead floats from the soldering pad while maintaining the solder connection, the solder is sucked between the lead and the pad, and slopes are distributed around the lead, as shown in Figure 4. 2 of the quadratic approximation formula for the contour line of the slope
The order coefficient A is A>TH.

FIGS. 5 and 6 show the case where the leads are completely separated from the soldering pads and the solder connection is broken, so that they are not connected. In this case, the solder spreads over the pad in a semicircular manner,
The sloped portion exists around the solder and includes a flat portion inside. FIG. 5 shows the case where the solder does not spread over the entire pad, and the flat part 24 is between the sloped part 23 of the solder and the lead.
is detected. From this, the quadratic coefficient of the quadratic curve approximating the contour of the slope is A>TH, and if there is a certain area or more of a flat part between the quadratic curve and the lead, it is determined that the lead is floating (unsoldered). can. When the lead is completely separated from the soldering pad and the solder connection is broken, and the solder spreads over the entire pad, the sloped portion of the solder is distributed around the edge of the pad, as shown in FIG. The phenomenon is the case shown in Fig. 5, but in this case, the sloped part contour line 25 is located at or near the tip of the pad, causing the lead to float (not soldered).
It can be determined that

Next, the operation of the apparatus of this embodiment will be explained based on the flowchart shown in FIG. That is, the CPU 8 is
By selecting or switching between the ring-shaped upper stage illumination 12 and the ring-shaped lower stage illumination 13 through the external device control unit 9, the reflected light reflected from the surface of the solder fillet 15 by each illumination is used. 17,
18 images are captured by the TV camera 1 and input to be recorded in the memory 10 via the image input/output unit 7, and the images under each illumination are read out from the memory 10 and the soldered part 15 to be inspected is identified as the slope part 19. Segment into flat parts 20. Next, the CPU 8 performs a quadratic approximation of the boundary between the slope portion and the flat portion based on the above (Formula 1). It is checked whether the quadratic coefficient A of the obtained quadratic curve is less than a certain value TH, and if YES, the product is determined to be a good product as shown in Fig. 3 without any defects such as unconnected or floating leads. . If this condition is not met, it is assumed that a lead floating defect has occurred. Next, if this condition is not met and the quadratic curve is distributed at or near the tip of the pad, it is determined that the solder has spread over the entire pad 18 and is a lead floating defect where the solder is not bonded, as shown in FIG. Next, if this condition is not satisfied, and furthermore, the flat part 24 between the quadratic curve and the lead has a certain threshold area or more, that is, an area corresponding to this flat part in the image recorded in the memory 10. If the number of pixels exceeds this value, it is determined that the solder does not spread over the entire pad 18, resulting in a floating lead defect as shown in FIG. If this condition is not met, the solder shown in FIG. 4 is considered to be defective in that it is in a bonded state but has floating leads. Generally, one set captured in the memory 10, that is, each image captured by the camera 1 using the upper and lower illuminations shown at 12 and 13 and inputted by the image input/output unit 7, includes a plurality of solder pieces. The attached part is imaged. For each soldered portion captured in this image, a defective inspection for lead floating as shown in FIGS. 4 to 6 is performed using the shape pattern of the solder fillet as described above. If all the soldering inspections in the image are completed and there are still other soldering parts to be inspected, the external equipment unit moves the XY table and continues the inspection according to the inspection sequence.

As described above, the floating state of the lead can be detected based on the shape pattern of the solder fillet. Although this embodiment has been explained using two stages of illumination, it is also possible to use multi-stage illumination to detect the degree of inclination of the solder surface and segment it into flat parts and sloped parts, as shown in 26 in Fig. 7. I do not care. In addition, there are inspection items such as the presence or absence of solder, excess or deficiency, etc., but the optical system for these solder inspections is not limited to the illumination 2 shown in the optical system in Figure 1, and is based on the detection principle. A corresponding optical system may be added to the detection system consisting of the camera 1 and illumination 2 shown in FIG.

[0015]

[Effects of the Invention] According to the present invention, floating leads of surface mount components are detected based on the solder joint state, so in addition to defective electrical connections such as non-bonding, lead floating even when solder joints are present. This makes it possible to detect defects that pose problems in terms of strength, and by combining this with other solder defect detection methods, highly reliable soldering inspection can be achieved. This makes it possible to automate the soldering inspection of mounted components, resulting in labor savings and improved reliability in the soldering process.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an apparatus showing an embodiment of the present invention.

FIG. 2 is a sectional view of a portion to be inspected.

FIG. 3 is a diagram showing a soldering pattern in a normal state.

FIG. 4 is a diagram showing a soldering pattern in which the solder is connected but the leads are floating.

FIG. 5 is a diagram showing a soldering pattern in which the leads are floating and the solder is not bonded.

FIG. 6 is a diagram showing a soldering pattern in which the leads are floating and the solder is not bonded.

FIG. 7 is a diagram showing an alternative optical system.

FIG. 8 is a flowchart of the operation of the apparatus as a whole.

[Explanation of symbols]

1...TV camera, 2...lighting,
3...XY table 4...Printed circuit board, 5...Flat package, 6...Control device 7...Image input/output unit, 8...CPU9...External device control unit, 10...Memory,
11...Bath 12...Upper lighting, 13...
Lower stage illumination, 14...Lead 15...Solder fillet, 16...Irradiation light beam by lower stage illumination 17...Irradiation light beam by upper stage illumination, 18...Soldering pad 19...Slanted part on solder surface, 20 Flat part 21, 22 on solder surface , 23, 25...Boundary of the slope on the solder surface 24...Solder flat part between the solder slope contour line and the lead, 26...Multi-stage annular illumination

Claims (5)

[Claims] 1. A device for positioning a printed circuit board, a device for capturing an image of the printed circuit board, a circuit for inputting an image captured by the image capturing device to a control device, and a control for controlling the positioning device and processing the input image. The system has a device and an illumination device with different irradiation angles on the inspection side of the board surface, and the lead floating state of the surface mount IC to be inspected in the captured image is detected by the solder at the lead tip in the image. A lead floating detection device for a surface mount IC, characterized in that detection is performed based on a two-dimensional distribution state of a constant inclined surface. 2. A means for detecting a lead floating state of a surface-mounted IC to be inspected in a captured image, the means detecting a floating state of a lead of a surface-mounted IC to be inspected includes curvature of a predetermined slope area of a solder surface of a lead tip in the image distributed two-dimensionally. 2. The lead floating detection device for a surface mount IC according to claim 1, wherein the lead floating detection device is of a certain degree. 3. Means for detecting a lead floating state of a surface mount IC to be inspected in a captured image is configured to detect a predetermined slope area of a solder surface of a lead tip in a two-dimensionally distributed image. 2. The lead floating detection device for a surface-mounted IC according to claim 1, wherein the device approximates the following curve and uses its quadratic coefficient. 4. A means for detecting a lead floating state of a surface-mounted IC to be inspected in a captured image, wherein a certain inclined surface area of a solder surface of a lead tip in the two-dimensionally distributed image is configured to 2. The lead floating detection device for a surface mount IC according to claim 1, wherein the lead floating detection device for a surface mount IC detects that the lead is located at the tip of a mounting pad. 5. Lead floating detection for a surface mount IC according to claim 3, characterized in that the area of a flat part of the solder between the lead and a quadratic curve approximating a certain slope area of the solder is detected. Device.