JPH04257291A - Inspection apparatus for printing plate - Google Patents

Abstract

PURPOSE:To provide an inspection apparatus for a solder cream printing plate which is capable of previously obviating defective printing such as a blur or a smear. CONSTITUTION:A pair of image pick-up apparatus 3a and 3b are disposed above and below a printing plate 2, which is used in printing a solder cream on a printed wiring board 1, in such a manner as to face each other with the printing plate 2 interposed therebetween. Images of the printing plate 2 which are shot both from a top and a bottom angle by the apparatus 3a and 3b are compared respectively with a reference image by means of a decision means 4, thereby deciding whether or not a solder cream 7 remains on the print board.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates primarily to a solder cream printing apparatus for printed wiring boards, and more particularly to a solder cream printing plate inspection apparatus.

0002

[Prior Art] Generally, in a solder cream printing device for printed wiring boards, a screen-like printing plate is applied to the top surface of the printed wiring board, and the solder cream supplied to the top surface of the printing plate is applied to the holes of the printing plate using a squeegee. A screen printing method is used in which the adhesive is rubbed onto the top surface of the printed wiring board, and then the printing plate is lifted upwards. The procedure for printing solder cream on a printed wiring board using this screen printing method includes, for example, placing the printed wiring board on a predetermined printing stage, and approaching the top surface of the printed wiring board from a standby position above the printed wiring board. The solder paste placed on the printing plate is rubbed against the printing plate with a squeegee to print.After this, the printing plate is raised to the standby position and the printed wiring board is removed from the printing stage. The procedure used is to lower it and place it on a stage for the subsequent process (component mounting).

0003

[Problems to be Solved by the Invention] As electronic devices become smaller and lighter, technology for mounting surface-mounted components such as QFP (quad flat package) on the surface of printed wiring boards, that is, surface-mounting. Technology (
SMT) is rapidly developing, and circuit density is becoming finer pitch (for example, footprint width 0.3 mm,
1.6 mm in length and 0.6 mm in pitch) is being rapidly developed. For this reason, there is a need to further improve the printing accuracy of solder cream. However, it has been found that the more fine pitch printing plates are made, the more frequently printing defects such as so-called printing blur and bleeding occur.

The cause of such printing defects is that the aperture ratio (ratio of depth to opening area) of the printing plate increases as the opening area and opening pitch of the printing plate holes become finer, as shown in FIG. As shown in part (a) of Fig. 4, the solder cream 7 may not come out easily and remain in the plate hole 2a, or as the printing is repeated, the solder cream 7 remaining in the plate hole 2a may be removed as shown in Fig. 4 (a). b) Printing plate 2 as shown in part
It has been found that the problem is that the particles wrap around the hole 2a on the bottom surface of the plate. That is, when the solder cream 7 remains in the plate hole 2a, the amount of the solder cream 7 adhering to the surface of the printed wiring board 1 decreases, and so-called printing blur occurs, which weakens the adhesive strength of the parts. Otherwise, it may cause anxiety about electrical continuity. In addition, when the solder cream 7 remaining in the plate hole 2a is pushed out to the bottom surface of the printing plate 2 during subsequent printing, it wraps around the plate hole 2a and adheres to the printed wiring board 1, so it adheres to the printed wiring board 1. The outline of the solder cream 7 becomes unclear, so-called bleeding occurs, and the solder cream adheres between the footprints, resulting in a short circuit between the footprints, a so-called bridging phenomenon. .

Conventionally, such printing fading or blurring is detected by inspecting the printed wiring board 1, and the printing is corrected if necessary, or the printed wiring board is removed if it cannot be corrected. It is being disposed of. That is, since defective products with printing defects are produced and then detected, man-hours are wasted and resources are wasted.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a printing plate inspection device that can prevent the occurrence of printing defects such as blurring and bleeding.

[0007]

[Means for Solving the Problems] In order to achieve the above object, a printing plate inspection device according to the present invention is provided with a printing plate used in a solder cream printing process of a printed wiring board 1, for example, as shown in FIG. A pair of imaging devices 3a and 3b arranged above and below the printing plate 2 compare images of the upper and lower surfaces of the printing plate 2 captured by the imaging devices 3a and 3b with respective reference images to determine the solder cream 7. and determination means 4 for determining whether or not any of the components remain on the printing plate 2.

[0008]

[Operation] In the present invention, before printing, images of the upper and lower sides of the printing plate 2 are photographed by a pair of imaging devices 3a and 3b,
By comparing these images with their reference images,
It is possible to determine the presence or absence of solder cream remaining in the plate hole, the presence or absence of solder cream leaking from the plate hole to the surrounding area, etc. Furthermore, it is possible to stop printing, clean the printing plate, etc., and prevent printing fading, blurring, etc. Necessary measures can be taken to prevent the occurrence.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A printing plate inspection apparatus according to an embodiment of the present invention will be described below with reference to the drawings. In this device, Fig. 3(b)
As shown in (d), the surface mounting printed wiring board 1 is placed on a predetermined printing stage, and then
As shown in c), the printing plate 2 is lowered from the upper standby position to a position close to the top surface of the printed wiring board 1, and then a predetermined amount of solder cream 7 is supplied to the top surface of the printing plate 2. A squeegee 8 made of rubber or the like is rubbed against the top surface of the printing plate 2 by moving it back and forth several times to remove the solder cream 7.
The printing plate 2 is rubbed into the hole 2a of the printing plate 2 to be attached to the upper surface of the printed wiring board 1, and then the printing plate 2 is returned to its original standby position.

Now, in this device, as shown in FIG.
Imaging devices 3a and 3b facing the printing plate 2 above and below the printing plate 2 located in the standby position, and an imaging device 3
determining means 4 for determining whether or not solder cream remains on the printing plate 2 by comparing the images of the upper and lower surfaces of the printing plate 2 taken by a and 3b with respective reference images; When it is determined that there is residual on the printing plate 2, the apparatus includes a notification means 5 for notifying the determination result, and a display means 6 for displaying the detection result of the determination means 4 as an image.

As the imaging devices 3a and 3b, known devices such as a video camera with a built-in CCD array may be used. FIG. 2 is a block diagram showing the determining means 4. The image data obtained from the imaging devices 3a and 3b is converted by a binarization circuit 41 into binary image data in which, for example, the holes in the printing plate are set to "1" and the other parts are set to "0". It is stored in the storage means 42. This storage means 42 is configured to store a reference image 42a that is an image of a printing plate serving as a reference, and a comparison image 42b that is an image of a printing plate after printing. Image data of reference image 42a and comparison image 4
It is compared with the image data of 2b by a comparison circuit 43, and the presence or absence of a defective part is detected.

A display means 6, for example a CRT device 6a, for displaying an image of the detection result of the determination means 4 is, for example, an image pickup device 3.
In order to display the images of the upper and lower sides of the printing plate 2 photographed by a and 3b, and to make it easier to distinguish between these images and the parts different from the reference image and other parts, for example, the photographed printing plate 2 The positional data of the locations where the images of the upper and lower sides of the photographed printing plate 2 differ from the corresponding reference images are displayed, for example, as coordinates, and the images of the upper and lower sides of the photographed printing plate 2 differ from the corresponding reference images. The location is configured to be displayed in a different color from other locations. Further, the display means 6 for displaying the detection results of the determination means 4 as an image enlarges and displays the portions where the photographed images of the upper and lower surfaces of the printing plate 2 differ from the corresponding reference images, if necessary. It can be configured as follows. Furthermore, in addition to the above-mentioned CRT device, it is also possible to provide a printer 6b capable of outputting the state of the printing plate including the above-mentioned defective portion as an image.

In this printing plate inspection apparatus, before the first printed wiring board 1 is carried into the printing stage, images of the top and bottom surfaces of the printing plate 2 (printing plate 2 before printing) serving as a reference are captured by an imaging device. 3a and 3b, and the determination means 4
is input. This image data is then binarized by the binarization circuit 41 in the determination means 4 and stored in the storage means 42 of the determination means 4 as image data of the reference image 42a. Thereafter, the printed wiring board 1 is carried into the printing stage, printing is completed, and each time the printed wiring board 1 is carried out from the printing stage, an image of the upper and lower surfaces of the printing plate 2 which has returned to the standby position is captured by the imaging device 3a. 3b and input to the determination means 4, and this image data is also binarized in the same way as above and stored in the storage means 42 as a comparison image 42b. After that, the determining means 4 compares the image data of the newly input comparison image 42b and the image data of the reference image 42a to determine whether there is a different part (defective part) between the two image data, and if there is a defective part, In this step, the CRT device 6a displays the position data of the defective part, and the defective part is displayed in a different color from other parts. Note that by printing an image representing the defective portion on a transparent sheet using the printer 6b and superimposing it on the printing plate, the defective portion can be easily found.

[0014] This makes it possible to easily detect defective parts. In addition, by specifying and enlarging the displayed defective part based on the position information and the displayed image, it is possible to check the remaining state of solder cream 7 in the plate hole 2a of the defective part and the solder on the bottom surface of the printing plate 2. The state of the cream 7 being spread can be confirmed. Then, based on such observation results, it is possible to instruct the parts of the printing plate 2 that require cleaning and to efficiently clean the printing plate 2, thereby preventing the occurrence of printing defects in subsequent printing. can.

Although only the solder cream printing plate has been described, it goes without saying that the present invention can also be applied to printing plates for circuit patterns on ceramic substrates.

[0016]

As described above, in the printing plate inspection device of the present invention, the printing plate is photographed by an imaging device every time printing is performed once or every time, and the image is compared with a reference image to determine whether the printing plate is printed. It is possible to inspect whether solder cream remains in the plate holes or wraps around the bottom surface of the printing plate, etc., which may cause defects. Therefore, the cause of defective printing can be detected before it occurs, and based on the detection of the cause of printing defects, the printing plate is cleaned and the cause of the printing defects is removed, thereby reliably preventing the occurrence of printing defects. This can significantly reduce the incidence of printing defects, as well as reduce man-hours and wasteful use of resources.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a printing plate inspection apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram of determination means of the present invention.

FIG. 3 is an explanatory diagram of an example of a printing plate inspection procedure to which the present invention is applied.

FIG. 4 is a schematic diagram showing causes of printing defects.

[Explanation of symbols]

1 Printed wiring board 2 Print version 2a　Print hole 3a/3b Imaging device 4 Judgment means 6 Display means 7 Solder cream

Claims (3)

[Claims] 1. A pair of imaging devices (3a) and (3b) arranged above and below a printing plate (2) used in the solder cream printing process of a printed wiring board (1), and an imaging device. The images of the upper and lower surfaces of the printing plate (2) captured by (3a) and (3b) are compared with the respective reference images to determine whether solder cream (7) remains on the printing plate (2). A printing plate inspection device comprising: determining means (4). [Claim 2] The determining means (4) is a printing plate before printing (
2) The printing plate inspection apparatus according to claim 1, wherein the printing plate inspection apparatus is configured to store images of the upper and lower surfaces of the image forming apparatus as respective reference images. 3. The printing plate inspection apparatus according to claim 1, further comprising display means (6) for displaying an image of the inspection result of the determination means (4).