PCB Fabrication

Fingerprints are one of the main reasons that cause bad scrap after PCB processing and end-user reliability degradation

by:A-TECH      2021-03-23
'Fingerprint' is a major scourge of PCB processing, and it is also one of the main causes of poor PCB scrapping and end-user reliability degradation. And almost every link in PCB board manufacturing runs through manual operations, and only every member of the manufacturing industry develops Good habits, to prevent bare hands from touching the board, will reduce the hazards of fingerprints to the PCB. During the PCB processing process, the hands and the board have frequent opportunities to contact the board, so fingerprints have become the most difficult problem in the industry. Let’s talk about fingerprints that can lead to PCBs. Causes, hazards and avoidance methods of bad plates:   1. Fingerprints: Fingerprints are hand sweat stains. Its main components are as follows:    A, water B, inorganic salts (such as Nacl, etc.)    C, fatty oils (non-minerals) D, cosmetics and skin care products E, all kinds of dirt touched by bare hands (or dirty gloves) 2, the hazards of fingerprints in the PCB manufacturing process A, bare objects touch the board in a very short time to make the board surface The copper undergoes a chemical reaction, causing the copper surface to oxidize. After a longer time, it will show obvious fingerprints after electroplating, and the uneven plating will cause serious defects in the appearance of the product.    B. The bare hand touching the board before the solder mask will cause the solder mask to fall, As a result, the adhesion of the green oil deteriorates, and it will blister and fall off during the hot air leveling. C. During the process of the gold plate after the solder mask until the packaging, the bare hand touches the plate surface, which will cause the plate surface to be unclean and cause poor solderability. , Or poor bonding.    D, printed wet film or silk-printed circuit and the board surface before lamination has fingerprint grease, which can easily cause the adhesion of the dry/wet film to decrease, and cause the penetration and separation of the coating during electroplating. The gold plate is easy to cause the pattern of the plate surface, and the surface of the plate is oxidized after the solder mask production is completed, and the yin and yang color appears.    If the above phenomenon is not standardized and eliminated, it will damage the pass rate of the product and the one-time pass rate, resulting in a long production and processing cycle and rework. The high material rate and the low on-time delivery rate are detrimental to the company's image in the eyes of customers.    3. How to prevent bare hands from touching the board is the key link of fingerprints A. Every employee is required to develop a good habit of taking and releasing boards. B. Carry gloves and finger cots with you C. Always wear gloves (such as cloth gloves, rubber gloves, finger cots, etc.) in the process where you can wear gloves.    D. Hold the edge of the board, lay it flat, palm as the axis, and rotate coaxially'.
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