What is A SMT Solder Paste Injection System ?

A Solder Paste Inspection system, also known as SPI, is a solder paste detection system. The main function is to detect the quality of the printing of solder paste such as volume, area, height, XY offset, shape, bridge, etc. The most common methods for detecting the tiny solder paste quickly and accurately are PMP and Laser.

To learn about Solder Paste check out this article 

To learn about SMT Solder Paste printing check out this article 

spi laser triangulation

1. Laser Triangulation Technology

This uses laser as the detection light source. Distortion of laser beam will be different at different heights of 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. The calculation is then carried out to obtain the test results.

laser triangulation technology

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.

smt pmp

2) The high precision value is obtained by measuring the changes of the gray-scale of the structure grating.

8 bit gray scale


3) With the change of phase, each solder paste is sampled 8 times, which ensures high repeatability.

8 bit high repeatibility


Components of PCBs, 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, 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, hidden dangers in quality can be found in time before backflow welding. Therefore, there is almost no need for further repair costs and scrap. 


Is quality something you care about in your production? 

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NexPCB places high importance on quality assurance and standards. We offer full inspection before shipping which includes structural reliability and performance testing. All of our facilities are ISO9001 certified. Learn more about our quality assurance technologies here.

You can be assured of the quality of your PCB/PCBA and SMT production. 

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Posted by Liang Guo

Liang Guo

Liang is a skillful Electronics Engineer with an ability to solder almost anything. By anything, we mean 15+ year old shattered HDD Circuitry to retro gaming consoles .