JPH07273500A - Mounted printed circuit board automatic inspection device - Google Patents

Abstract

(57) [Summary] [Purpose] It is possible to accurately measure lead displacement even when the lead floats from the pad or solder is applied to the lead. A mounted printed circuit board automatic inspection device equipped with a measuring means for determining a volume centroid of a measured object by an optical cutting method and measuring a positional deviation of leads of electronic components mounted on a printed circuit board pad in a three-dimensional direction. Is.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatically mounted printed circuit board for automatically inspecting whether or not the lead position of an electronic component mounted on the printed circuit board is correctly mounted on each pad of the printed circuit board. Regarding inspection equipment.

[0002]

2. Description of the Related Art A conventional inspection device of this type is shown in FIG. This inspection device
The lead b ₁ of the electronic component b mounted on the printed board a is photographed by the camera c, and it is detected by pattern recognition whether or not each lead b ₁ is correctly mounted on the pad a ₁ of the printed board a. It was

[0003]

By the way, in the above-described planar detecting device, since there is solder on both the lead and the pad, it is difficult to discriminate by the difference in reflectance or the difference in luminance. However, there is a problem that the detection accuracy becomes unstable.

In addition, there is a problem in that the lead deviation cannot be correctly measured with respect to a factor in the three-dimensional direction, such as a case where the solder is on the lead or the case where the lead itself is floating from the pad. there were.

The present invention is intended to solve the above-mentioned problems, and an object of the present invention is to accurately measure a lead deviation even when a lead is lifted from a pad or solder is placed on the lead. It is intended to provide an automatic inspection device for a mounted printed circuit board that can be mounted.

[0006]

SUMMARY OF THE INVENTION The mounted printed circuit board automatic inspection system of the present invention is intended to achieve the above-mentioned object. The means is to obtain the volume centroid of the measured object by the optical cutting method in the three-dimensional direction. The measuring means for measuring the positional deviation of the lead of the mounted electronic component with respect to the pad of the printed circuit board.

In addition to the first aspect of the present invention, the present invention further comprises a measuring means for obtaining the area center of gravity at the center of the lead and measuring the positional deviation of the lead in the two-dimensional direction.

[0008]

In the mounted printed circuit board automatic inspection apparatus of the present invention configured as described above, the reflected light obtained by irradiating the lead of the electronic component on the mounted printed circuit board with a laser beam is applied.
With the D camera, the locus is captured and image processing is performed to obtain a volume centroid, and this value is compared with a preset volume centroid value, and when it is determined to be within a threshold value, it is determined to be normal. It is a thing.

If it is determined that the value is equal to or more than the threshold value, it is determined that the lead is floating, then the area center of gravity at the lead center is obtained, and this value is compared with the preset value of the area center of gravity. When it is determined to be within the threshold value, it is determined to be normal, and when it is equal to or more than the threshold value, it is determined to be a lead shift.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the mounted printed circuit board automatic inspection apparatus according to the present invention will be described with reference to FIG. Reference numeral 1 is a laser light source for irradiating a lead of an electronic component mounted on a printed circuit board with a laser beam, and reference numeral 2 is, for example, a CCD camera capable of identifying the brightness of light reflected by the lead radiated by the laser light source 1. An image input device 3, an image processing device for processing luminance information obtained by analog / digital conversion of the output of the image input device, and 4 an image processing device 3
5 is a control device for controlling on / off and sweeping (control of the XY table) of the laser light source 1 in accordance with the image capturing timing. .

Next, the principle for measuring the deviation of the leads B _{1 to} Bn with respect to the pads A _{1 to} An of the present invention will be described with reference to FIGS.
It will be described together with FIG. Significance of measuring the displacement with the volume centroid. Obtaining the volume centroid has the meaning of grasping the lead displacement as a whole. Specifically, when the laser is swept as shown in FIG. 2 and the locus thereof is read by the image input device 2, the cross-sectional areas S _{1 to} Sn of the locus as shown in FIG. 3 are obtained.

In order to calculate the volume V from the above information, for example, regarding the lead B ₁ , it can be obtained by the following equation. V = (S ₁ + S ₂ + ... Sn) × P Note that P is the sweep width. The volume centroid is calculated as the centroid of the cross section S ₁ + the centroid of S ₂ + ... the centroid of Sn / the number of sweeps.

Significance of measuring the displacement by the area center of gravity When solder is placed on the lead and this portion is measured as a volume, an error occurs in the measurement of the center of gravity of the volume. In this case, more accurate measurement can be performed by slicing the locus at a height of about half of the height (thickness) of the lead after the three-dimensional measurement as described above and determining the area centroid of this portion. .

Specifically, the locus is cut at the slice level as shown in FIG. 4, and the area centroid is defined as the midpoint of the line segment L ₁ + the midpoint of the line segment L ₂ + the midpoint of the line segment L ₃ / the number of sweeps. Ask for points.

Next, the operation of the present invention will be described with reference to the flow charts of FIGS. First, the information regarding the lead mounting position of the electronic component is input to the arithmetic unit 4. Next, the printed board to be measured is set on the XY table, the XY table is controlled according to the program stored in the control device 5, and the beam from the laser light source 1 is swept at right angles to the leads (step S1).

As a result of this sweep, the laser light reflected from the lead is input to the image input device 2, so this two-dimensional image signal is sent to the image processing device 3 (step S2).
The image processing device 3 converts the input analog two-dimensional image signal into a digital signal with 256 gradations (step S3).

Then, a light cutting line is extracted from the digital signal having the highest brightness value (step S4), and a high brightness point between the pads is obtained to determine the height of the substrate surface (step S4).
5) Average height between cutting lines in the X direction at or above the reference point of the height of the surface of the substrate The center of gravity x in the X coordinate is obtained and stored from the arithmetic mean value in the Z direction (pixel unit) (step). S6).

Further, the center of gravity at the Z coordinate is obtained from the average of the averages between the cutting lines in the Z direction above the reference point of the height of the substrate surface in the X direction (pixel unit), and the height of the substrate surface is subtracted. The value z is stored (step S7). And
It is monitored whether or not this operation has been performed a preset number of sweeps (N times) (step S8).

[0019] If it is determined that sweeps the number of times set is performed to determine the volume center of gravity of the lead portion from the addition average of the center of gravity z ₁ to z _n of the center of gravity x ₁ ~x _n and Z coordinates of the X-coordinate (step S9 ). Then, the coordinates of the volume centroid stored in advance are compared with the volume centroid obtained as described above (step S10), and if it is determined to be within the threshold value, it is determined to be normal (step S11), and the operation is performed. Ends.

In step S10, if it is above the threshold value, it is judged that there is floating of the lead (step S12), and then the average between the cutting lines at the height approximately in the middle of the leads of the optical cutting line is determined. The area center of gravity at the intermediate position is obtained from the arithmetic mean of the number of sweeps on the X coordinate (step S13).

Then, the area barycenter coordinates stored in advance are compared with the area barycenter determined as described above (step S1).
4) If the comparison result is within the threshold value, it is determined to be normal (step S15), and if the comparison result is equal to or more than the threshold value, it is determined that the lead shift occurs (step S16). ), All measurement operations are completed.

In the same manner, by repeating the above-described measuring operation for each lead of each electronic component, it is possible to detect the floating and displacement of the lead of the electronic component mounted on the printed board.

[0023]

As described above, the present invention obtains the center of gravity of a volume by performing image processing by capturing the locus of the reflected light obtained by irradiating the lead of the electronic component on the mounted printed circuit board with the laser beam. , This value is compared with the preset value of the center of gravity of the volume, and if it is determined that it is within the threshold value, it is determined as normal, so that even if there is lead floating, it can be accurately detected. it can.

If it is determined that the value is equal to or more than the threshold value, the area center of gravity at the center of the lead is obtained, and this value is compared with a preset value of the area center of gravity, and it is determined that the area center of gravity is within the threshold value. In this case, it is determined to be normal, and if it is equal to or more than the threshold value, it is determined that the lead shift has occurred, so even if solder is on the lead, it can be accurately determined and the detection accuracy is improved. I have.

[Brief description of drawings]

FIG. 1 is a circuit block diagram showing an embodiment of a mounted printed circuit board automatic inspection device according to the present invention.

FIG. 2 is an explanatory diagram for explaining an operation showing a basic principle for obtaining a volume centroid.

FIG. 3 is a waveform diagram of the above.

FIG. 4 is a waveform diagram for obtaining an area center of gravity.

FIG. 5 is a flow chart diagram.

FIG. 6 is a subsequent flowchart diagram of the above.

FIG. 7 is an explanatory diagram of a conventional inspection device.

[Explanation of symbols]

 1 Laser Light Source 2 Image Input Device 3 Image Processing Device 4 Computing Device 5 Control Device

Claims (2)

[Claims] 1. A measuring means for measuring the volume centroid of an object to be measured by an optical cutting method, and measuring a positional deviation of leads of electronic components mounted on a pad of a printed circuit board in a three-dimensional direction. Mounted printed circuit board automatic inspection device. 2. The automatic mounted printed circuit board as set forth in claim 1, further comprising a measuring means for determining an area center of gravity at a center of the lead and measuring a positional deviation of the lead in a two-dimensional direction. Inspection device.