Touching the pcb by hand may bring serious consequences, which may cause bad scrap of the PCB and end user reliability. As a PCB design engineer, it is unavoidable to directly touch the PCB board by hand during the work process. However, only the good habit of wearing gloves can still reduce or cure the "skin contact" on the PCB board. Let's talk about the reasons why fingerprints can lead to bad PCBs, the hazards, and how to avoid them.
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, various types of dirt touched by bare hands (or dirty gloves)
Fingerprinting hazards in the PCB manufacturing process
A. The bare board touches the copper on the board surface in a very short time and causes the copper surface to oxidize. After a long time, the fingerprints became obvious after electroplating, and uneven plating caused severe bad appearance on the appearance of the product.
B. The bare hand touch panel before solder resisting will result in solder masking, which will cause the adhesion of green oil to deteriorate and will cause blistering and falling off during hot air leveling.
C. After the solder plate has been soldered and resisted to the process before packaging, touching the surface with naked hands can cause the board surface to be dirty, resulting in poor solderability or poor bonding.
D. Fingerprinting grease on the surface of the printed circuit board before wet film or screen printing, which can easily cause the adhesion of the dry/wet film to fall. During the plating process, the plating and plating are separated, and the gold plate can easily cause the board surface. Patterns, after the completion of solder mask production, the board surface oxidation, there yin and yang.
If the above phenomena are not standardized and eliminated, the qualified rate of products will be damaged, and the one-time pass rate will result in a long production and processing cycle, high rework feed rates, and low on-time delivery rates, which will damage the company’s image in the eyes of customers.
3, how to put an end to the naked hand touching the board is the key to cure finger printing
A. Each employee is required to develop a good habit of taking and placing boards B, carrying gloves and finger cuffs C, and wearing gloves (such as cloth gloves, rubber gloves, finger sleeves, etc.) when wearing gloves.
D. Lead by example, precept and example, establish an image model, and engrave a mouthful in the mind. “Two hand-held plates, flat and flat, palm as axis, coaxial rotation”.