JP2001050730A - Soldering inspection method and device for both-side mounting board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a soldering inspection method for both-side mounting board detecting a deformation of a print circuit board to correct the deformation, and inspecting soldering state affected by the deformation of the print circuit board without an error by subtracting a single-side mounting image from a both-side mounting image. SOLUTION: A first image obtained by irradiating X ray on a print circuit board 11 with parts mounted on one side, and a second image obtained by irradiating X ray on the print circuit board with parts mounted also on the other aide are stored in an image memory 4. A position deviation is obtained from the first and the second images. The first, or the second image is interpolated as much as the amount of the position deviation. An image on the opposite side is obtained by subtracting the first image from the second image to determine the state of soldering.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of irradiating a mounting board, in which mounting parts such as ICs are soldered to both sides of a printed circuit board, with X-rays, and determining a soldering state of the electronic parts on both sides from a transmission image of the X-rays. A method and apparatus for testing.

[0002]

2. Description of the Related Art In recent years, in order to make effective use of the area of a printed circuit board as the density of a printed circuit board increases, a ball grid array type or a lead having ball terminals on the back surface of the main body is used instead of an IC lead. J-lead type I bent inward
C has been developed, and this IC has been developed by soldering and mounting it on a printed circuit board.

[0003] Such an IC cannot be inspected by a television camera or a conventional method of sweeping a laser beam because the ball terminals and leads are not visible from the outside. Therefore, as a method for inspecting the soldering state of such a mounted component, there is a method of irradiating a printed circuit board with X-rays to obtain a transmission image, and judging the quality of the soldering from the transmission image.

By the way, recently, the density has been further increased,
Components such as ICs have been soldered to both sides of a printed circuit board. In order to inspect the soldering state of such a printed circuit board soldered to both sides, it is possible to judge the soldering state that the solder portions are overlapped by using the X-ray as described above. Disappears.

Therefore, as a method for inspecting the soldering state of such a double-sided mounting board, for example, Japanese Patent Laid-Open No. 8-51
There is one disclosed in Japanese Patent Publication No. 276. This method uses the X in a state where components are mounted on one side (A side) of a printed circuit board.
A line image is obtained, then an X-ray image is obtained in a state where components are mounted on another surface (surface B), and an image of surface B is obtained by subtracting an image of surface A from this image.

[0006]

By the way, since the image on the surface A is subtracted from the image on the surface B and the image on the surface B is obtained from the displacement of the entire image, the printed circuit board is partially If distorted, this distortion becomes a large error. The reason why the distortion occurs is that, in order to mount the component on the printed circuit board, the component is placed on the surface A, passed through a reflow furnace, heated, and mounted.
This is because the printed circuit board is distorted by heat because the component is placed on the surface and passed through the reflow furnace again.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to detect a distortion of a printed circuit board due to heat, correct the distortion, and convert a single-sided mounted image from a double-sided mounted image. It is an object of the present invention to provide a method for inspecting the soldering of a double-sided mounting board by which the state of soldering due to the distortion of the printed board can be inspected without error by subtracting.

[0008]

SUMMARY OF THE INVENTION A method for inspecting the soldering of a double-sided mounting board according to the present invention is intended to achieve the above-mentioned object, and the means for irradiating a printed board having components mounted on one side with X-rays. Storing the first image obtained by the irradiation and the second image obtained by irradiating the printed board on which components are mounted on the other side of the printed board with X-rays, in an image memory; A position shift amount is obtained from the second image, the first or second image is distortion-corrected by the obtained position shift amount, and the first image is subtracted from the second image to obtain an image on the other surface. And the state of soldering is determined.

Further, the determination of the amount of displacement is performed by dividing the first and second images into small areas in a state where the first and second images are partially overlapped, and distorting the first and second images in the small areas. It is desirable to obtain a vector, set the obtained distortion vector as a distortion vector of a small area central pixel, and obtain distortion vectors of other pixels by two-dimensional interpolation using distortion vectors of adjacent small areas, Further, as the first and second images, two types of X-rays having different wavelength distributions are irradiated on the printed circuit board to capture two images, and a difference operation between the two images is performed to convert the images to the printed circuit board. It is characterized by using an image in which the contained solder component is extracted.

[0010] Further, the soldering inspection of the double-sided mounting board is performed as follows.
A first image obtained by irradiating a printed circuit board with components mounted on one surface with X-rays and a second image obtained by irradiating X-rays on a printed circuit board with components mounted on the other surface of the printed circuit board
An image memory for storing the images of the first and second images, a position shift amount determining unit for obtaining a position shift amount between the first and second images stored in the image memory, and a shift amount obtained by the position shift amount determining unit. Image correction means for correcting distortion of the first or second image by an amount, difference processing means for subtracting a first image from the second image to obtain an image of the other surface of the printed circuit board, A pass / fail determination means for inspecting the soldering state of the other surface.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method and an apparatus for inspecting soldering of a double-sided mounting board according to the present invention will be described below with reference to the drawings. FIG. 1 shows a circuit block diagram illustrating the device of the present invention,
1 is an X-ray generator, 2 is an X-ray transmission image reader, 3 is A /
The D converter 4 stores an A image obtained by mounting components on one side (hereinafter referred to as A side) and an AB image obtained by mounting components on the other side (hereinafter referred to as B side). Memory, 5 is A
A positional shift amount determining means 6 for determining a shift amount between the image and the AB image, 6 is a CPU, 7 is an image correcting means for correcting the AB image from the positional shift amount obtained by the positional shift amount determining means 5, and 8 is a corrected image. Difference processing means 9 for subtracting the A image from the AB image is a pass / fail judgment means for judging the quality of the soldering state from the B image obtained by the difference processing means 8.

In FIG. 1, reference numeral 11 denotes a multilayer printed circuit board, and reference numerals 12 and 13 denote ball grid type ICs which are mounted on the printed circuit board 11 by soldering. ing.

Hereinafter, the operation based on the above configuration will be described with reference to the flowchart of FIG. First, the printed circuit board 1
When the X-ray generator 1 irradiates X-rays in a state where the IC 12 is mounted only on the A-side surface of the IC card 1, an X-ray transmission image composed of the ball grid of the IC 12 and the circuit pattern of the printed board 11 (not shown) is received by the reading device 2. Is done. Then, the image received by the reading device 2 is stored in the image memory 4 via the A / D converter 3 (Step S).
1).

Next, in a state where the IC 13 is also mounted on the B side of the printed board 11, the X-ray generator 1
When the line is irradiated, an X-ray transmission image including the ICs 12 and 13 and the circuit pattern of the printed circuit board 11 is received by the reading device 2. Then, as described above, the image received by the reading device 2 is stored in the image memory 4 via the A / D converter 3 (step S2).

The image A and the image AB stored in the image memory 4 are described in Japanese Patent Application Laid-Open No.
An image obtained by extracting a solder portion included in a printed circuit board by the energy subtraction processing disclosed in Japanese Patent Application Laid-Open No. 0-253550 can be used.

The energy subtraction process is a process of irradiating an electronic component with X-rays having at least two types of wavelength distributions and capturing an image thereof, and trying to extract a solder in a test object by a mutual operation thereof. is there. And if this energy subtraction process is performed,
This removes components other than solder contained in the inspection object, and can obtain an image in which only a specific substance is present.

Next, in the A image and the AB image stored in the image memory 4, since the printed board 11 is distorted when passing through the reflow furnace when the IC is mounted, the displacement is caused. The determination means 5 detects the amount of positional deviation. That is, the A image and the AB image are divided into a plurality of small areas, and the respective small areas are overlapped.

Then, a distortion vector (position shift) between the A image and the AB image in the small area is obtained. The obtained distortion vector is used as the distortion vector of the small region center pixel, and the distortion vectors of the other pixels are calculated using the distortion vectors of the adjacent small regions. That is, as shown in FIG. 3, the distortion vector indicated by the dotted line is predicted from the distortion vector indicated by the solid line, and the overall displacement amount in the image is obtained (step S3).

Next, a distortion-corrected image AB ', which is a corrected image obtained by distorting the AB image by the amount of positional deviation from the A image, is obtained from the positional deviation amount obtained as described above (step S).
4). Here, as an interpolation method used when obtaining a distortion vector of each pixel from a distortion vector of a small region typically obtained, linear interpolation using distortion vectors of four adjacent points may be used, If higher-precision interpolation is required, spline interpolation or the like may be used.

Next, the image A is subtracted from the distortion corrected image AB 'to obtain an image of the ball grid of the IC 13 mounted on the surface B and the circuit pattern on the printed circuit board 11 (step S5). Then, the soldering state is determined from the B-side image obtained as described above by a known X-ray inspection method (step S6). Note that the determination of the soldering state of the image of the first side A obtained separately is performed by a known X-ray inspection method separately from the determination of the soldering state of the image of the B side. Is completed.

In the above description of the operation, the case where the distortion-corrected image is created by using the AB image has been described. However, the distortion-corrected image may be created by using the A image. .

[0022]

According to the present invention, as described above, the X-ray images of the single-sided mounting and the double-sided mounting are stored, and thereafter, the amount of displacement of the printed circuit board due to heat during soldering is detected.
This displacement was corrected in one image, and then the one-sided mounted image was subtracted from the two-sided mounted image to obtain an image on the opposite side.Therefore, the soldering state due to the distortion of the printed circuit board should be inspected without error. This has the effect of, for example, Further, by performing a subtraction process on the X-ray image after the single-sided mounting and the X-ray image after the double-sided mounting, the solder connection portion included in the substrate can be inspected with high accuracy.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram showing a soldering inspection apparatus for a double-sided mounting board according to the present invention.

FIG. 2 is a flowchart for explaining the operation of the above.

FIG. 3 is an explanatory diagram for obtaining a displacement amount.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 X-ray generator 2 X-ray transmission image reading device 3 A / D converter 4 Image memory 5 Position shift amount judging means 6 CPU 7 Image correcting means 8 Difference processing means 9 Pass / fail judgment means 11 Printed circuit boards 12, 13 IC

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F067 AA62 AA67 CC14 DD10 GG06 GG09 HH04 KK06 LL16 RR12 RR24 RR30 RR35

Claims (4)

[Claims] 1. A printed circuit board on which components are mounted on one side has an X
A first image obtained by irradiating the X-ray and a second image obtained by irradiating the X-ray to a printed board on which components are mounted on the other side of the printed board; Calculating a displacement amount from the first and second images, correcting the first or second image by the determined displacement amount,
A method for inspecting soldering on a double-sided mounting board, characterized in that an image on the other side is obtained by subtracting a first image from a second image to determine a soldering state. 2. The method according to claim 1, wherein the first and second images are divided into small areas in a state where the first and second images are partially overlapped.
The distortion vectors of the first and second images in the small area are obtained, and the obtained distortion vector is set as the distortion vector of the central pixel of the small area. The distortion vectors of the other pixels are the distortion vectors of the adjacent small areas. 2. The method for inspecting soldering of a double-sided mounting board according to claim 1, wherein the method is obtained by two-dimensional interpolation using the following. 3. The printed circuit board is irradiated with two types of X-rays having different wavelength distributions as the first and second images to capture two images, and the difference between the two images is calculated from the images. 3. The method according to claim 1, wherein an image obtained by extracting a solder component contained in the printed board is used. 4. A printed circuit board on which components are mounted on one side
An image memory for storing a first image obtained by irradiating the X-ray and a second image obtained by irradiating the X-ray to a printed board on which components are mounted on the other surface of the printed board; Position shift amount determining means for obtaining a position shift amount between the first and second images stored in the image memory; and converting the first or second image by the shift amount obtained by the position shift amount determining means. Image correction means for correcting distortion, difference processing means for subtracting the first image from the second image to obtain an image on the other surface of the printed circuit board, and inspecting the soldering state of the other surface of the printed circuit board A device for inspecting soldering of a double-sided mounting board, comprising: a determination unit.