Explanation of SPI and AOI in SMT process

AOI, an automatic optical detector, is used to check the quality of solder printing and verify and control the printing process, identifying potential factors that contribute to this trend before the quality exceeds the range. AOI checks for poor installation and welding, such as the control parameters of the printing machine. By comparing good and bad images, under different lighting conditions, the defects will present different images, such as short circuits, offset, and slow speed. Then make timely adjustments using image contrast.

SPI (Solder paste inspection), identifying trends in quality changes and providing hints on the types of defects that are defective. SPI refers to a series of solder paste inspections, also known as automatic optical inspection. In the SMT production process, there will be various types of installation and welding defects, while AOI detects device installation and solder joints, which is inefficient and leads to maintenance. Nowadays, electronic components are becoming smaller and smaller due to factors such as tombstones and solder paste changes. Through a series of solder joint inspections, defects such as incorrect parts, extreme reactions, human factors, empty welding, and missing parts. SPI can intuitively tell users that SPI is a quality inspection for solder printing and verification and control of printing processes. Its basic function is to promptly detect defects in printing quality.

The difference between SPI and AOI

Quality control:

Some defects that are often overlooked during manual visual inspection include: component misalignment, insufficient soldering, short circuit of solder joints, faulty soldering, component reversal, component misalignment, component deformation, component missing, and component erection.

Process control

AOI is equipped with an information analysis terminal (IAT) to monitor the quality of solder joints in real time, generate Chart in real time, and feed back the type and frequency of failures and other information to the production control department in real time, so that the department can find problems in the production process in time and correct them as soon as possible, so as to minimize the loss of time and materials.

Process parameter verification and others

For a new type of single board to be processed, from printing process parameters to reflow soldering process parameters, careful modulation is required. The rationality of these parameter settings ultimately depends on the quality of welding, and this process must undergo multiple tests to achieve. AOI provides an effective means of verifying experimental results.

After SPI is applied to the printing machine, the quality inspection of solder printing and the verification and control of printing process parameters are carried out.

Solid SPI plays a significant role in the entire SMT production. AOI is divided into two types: pre furnace and post furnace, with the former detecting device mounting and the latter detecting solder joints.