The full name of SPI is ‘Solder Paste Inspection System’, which is a solder paste detection system. The main function is to detect the quality of the printing of solder paste, including volume, area, height, XY offset, shape, bridge, etc. The general methods for detecting the tiny solder paste quickly and accurately are PMP and Laser.
1. Laser Triangulation Technology
Use laser as the detection light source. Distortion of laser beam will be different at different height plane. The detector heads move continuously in a certain direction and the camera takes photos at set time intervals to obtain a set of laser distortion data. Then the calculation is carried out to obtain the test results.
2. PMP (phase modulation contour measurement technique)
1) The solder paste is measured by the phase change of the structure grating using a white light source
2) The high precision value is obtained by measuring the change of the gray-scale of the structure grating.
3) With the change of phase, each solder paste is sampled 8 times, which ensures the high repeatability.
Components on PCB, such as BGA, CSP, PLCC chip, etc., cannot be detected by AOI after the backflow of the patch due to the light occlusion caused by their own. SPI can minimize these defects. As electronic products become more and more precise and solder lead-free, the patch components become more and more miniature. Therefore, the quality of solder paste printing is becoming more and more important. SPI can ensure the good quality of solder paste printing and greatly reduce possible defects in products. As a means of quality process control, quality hidden danger can be found in time before backflow welding. Therefore, there is almost no possibility of repair cost and scrap, the cost has been effectively saved.