Automatic control systems above solder paste applying help to minimize the number of defects in the product before performing mounting and soldering operations. This leads to a significant reduction in the time and cost of already assembled printed circuit repairing. Quality inspection of the solder paste applying can be made as to each contact pad as well as selected critical zone (to increase the inspection rate). Applying of paste on the pad is controlled through the following analyses: measuring displacement by axes (X/Y/R), measurement of the thickness of the print (Z), checking the amount column of the paste, fill area measurement contact and verification print form. SPI system, other than tools for a full analysis of the quality of solder paste applying, equipped with functions adjustment offsets while applicating the material to the contact pads. Offset correction is performed on the basis of statistical quality assessment applying paste to the previous PCB. Through these functions is provided the maximum possible efficiency of the manufacturing process for the production of high-quality electronic products.
Screen Printing Defects |
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Description |
Reasons |
Elimination of defects |
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Not enough solder paste |
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1. Stencil aperture clogging |
1.Clean stencil often and better |
Excess solder paste |
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1. Low squeegee pressure on the stencil |
1. Increase squeegee pressure |
Paste offsets from pads |
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1. Low precision alignment of the stencil and the printed circuit board on board or stencil |
1. Check coordinates and sizes of reference marks and train them |
You can also familiarize yourself with other elements of the section Inspection of PCB assembly.