Solder paste automatic 3D-inspection (SPI)

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



Elimination of defects

Not enough solder paste


1.   Stencil aperture clogging
2. Scooping pasta with a squeegee
3. Stencil separation speed is too fast
4.Not enough paste on the stencil

1.Clean stencil often and better
2. Reduce squeegee pressure
3. Reduce stencil separation speed from PCB
4.Check the amount of paste on the stencil

Excess solder paste


1. Low squeegee pressure on the stencil
2. The paste is too thin
3. Stencil separation speed is too slow
4.Squeegee Wear
5.Below board support not configured
6. Bad stencil tension

1. Increase squeegee pressure
2. Change pasta
3.Increase the speed of separation of the stencil from the board
4.Check squeegee
5.Check bottom board support
6. Check the quality of the stencil tension

Paste offsets from pads


1. Low precision alignment of the stencil and the printed circuit board
2. Poor benchmarks

on board or stencil

1. Check coordinates and sizes of reference marks and train them
2. Make sure the stencil is securely mounted in the frame
3. Carry out diagnostics of the machine, perform calibration


You can also familiarize yourself with other elements of the section Inspection of PCB assembly.

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