PCB News - Related detection technology in SMT patch processing

Related detection technology in SMT patch processing

With the development of SMT chip processing technology (circuit board) and the continuous improvement of SMT assembly density, as well as the thinning of circuit patterns, the fine-pitch of SMD, the invisibility of device pins and other features, the SMT is patched. The quality control of processed products and the corresponding inspection work have brought many new technical problems. At the same time, it also makes the use of appropriate testability design methods and detection methods in the SMT process a crucial task.

It is very important to prevent various defects and unqualified risks from flowing into the next process through effective inspection methods in each step of SMT chip processing (circuit board). Therefore, "detection" is also an indispensable and important means in process control. The inspection content of SMT patch processing plant includes incoming material inspection, process inspection and surface assembly board inspection. Wear anti-static gloves and PU coated gloves.

Quality problems found in process inspection can be corrected through rework. The rework cost of unqualified products found after incoming inspection, solder paste printing, and pre-welding inspection is relatively low, and the impact on the reliability of electronic products is relatively small. However, the rework of unqualified products after soldering is quite different, because rework after soldering requires re-soldering after unsoldering. In addition to requiring man-hours and materials, it may also damage components and printed circuit boards.

Since some components are irreversible, such as Flip chips that require underfilling, and BGA and CSP that need to be re-balled after rework, it is more difficult to repair products such as embedding technology and multi-chip stacking, so the rework loss after soldering is relatively large. Anti-static gloves and PU coated gloves are required. It can be seen that process inspection, especially the first few process inspections, can reduce the defect rate and scrap rate, reduce rework/rework costs, and at the same time prevent quality hazards from the source as early as possible through defect analysis.

The final inspection of the surface mount board is also very important. How to ensure that qualified and reliable products are delivered to users is the key to winning in market competition. There are many final inspection items, including appearance inspection, component location, model, polarity inspection, solder joint inspection, electrical performance and reliability inspection, etc.

Testing is an important part of ensuring the reliability of SMT. The content of SMT inspection technology is very rich, the basic content includes: testability design; incoming raw material inspection; process inspection and assembly inspection after assembly, etc.

The testability design is mainly the PCB circuit testability design carried out in the PCB patch processing circuit design stage, which includes test circuits, test pads, test point distribution, testability design of test instruments, etc.

The incoming inspection of raw materials includes the inspection of PCB patch processing and components, as well as the inspection of all SMT assembly process materials such as solder paste and flux.

The process inspection includes the process quality inspection of printing, patching, welding, cleaning and other processes. Component inspection includes component appearance inspection, solder joint inspection, component performance testing and functional testing.

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