In the PCB circuit board industry, "finger prints" in surface-treated pads are a major hazard to circuit boards, and are also one of the main reasons for defective PCB circuit boards to be scrapped and end-user reliability to deteriorate. However, almost every link of PCB circuit board manufacturing runs through manual operations. Only when every member of the electronics manufacturing industry develops good habits and prevents touching the board with bare hands, will the harm of finger prints on the circuit board be reduced or eradicated. In the process of circuit board manufacturing and processing, there are frequent opportunities for hand and board contact, so finger prints have become the most difficult problem in the industry. Let's talk about the reasons, hazards and avoidance methods of "finger prints" that can lead to bad PCB boards:
1. Surface treatment pad fingerprints: Fingerprints are hand sweat stains, and its main components are as follows:
①. Water;
②. Cosmetics and skin care products;
③. Inorganic salts (such as Nacl, etc.);
④. Fatty oils (non-mineral);
⑤. All kinds of dirt touched by bare hands (or dirty gloves).
2. The harm of finger prints in the process of circuit board manufacturing
①. Touching the board with bare hands before solder masking will lead to solder masking, resulting in poor adhesion of the green oil, which will bubble and fall off during hot air leveling;
②. In the process of immersion gold board after solder masking and before packaging, touching the board surface with bare hands will cause the board surface to be unclean, resulting in poor solderability or poor bonding;
③. When the bare object touches the board, the copper on the board surface undergoes a chemical reaction in a very short period of time, causing the copper surface to oxidize. After a long time, there will be obvious fingerprints after electroplating, and the uneven coating will cause serious defects in the appearance of the product;
④. Printing wet film or silk screen circuit and the surface of PCB circuit board before film lamination have fingerprint grease, which can easily cause the adhesion of dry/wet film to decrease, and lead to seepage and plating separation during electroplating. Gold plate is easy to cause The pattern on the board surface oxidizes the board surface after the solder mask is made, and the yin and yang colors appear.
If the above phenomena are not standardized and eliminated, it will damage the pass rate of the product, the one-time pass rate will cause a long production and processing cycle, a high rate of rework and replenishment, and a low rate of on-time delivery will damage the company's image in the minds of customers.
3. How to prevent bare hands from touching the board is the key link to eradicate finger prints
①. Each employee is required to develop a good habit of taking and putting boards;
②. Carry gloves and finger cots;
③. Be sure to wear gloves in the process where gloves can be worn (such as cloth gloves, rubber gloves, finger cots, etc.);
④. Lead by example, teach by example, establish an image model, and engrave a jingle in your mind: "Two hands hold the edge of the board, put it flat, and the palm is the axis, and rotate on the same axis".
