PCB Technical - "Fingerprints" in PCB circuit board pads

"Fingerprints" in PCB circuit board pads

In the PCB circuit board industry, the "fingerprints" in the surface treatment pads are a major scourge of circuit boards, and it is also one of the main reasons for the poor scrapping of PCB circuit boards and the deterioration of end-user reliability. However, almost every link in PCB circuit board manufacturing runs through manual operations. Only when every member of the electronics manufacturing industry develops a good habit and prevents bare hands from touching the board, can the harm of fingerprints on the circuit board be reduced or eliminated. In the circuit board manufacturing process, the hands and the board contact frequently, so fingerprints have become the most difficult problem in the industry. Let's talk about the causes, hazards and avoidance methods of "fingerprints" that can lead to poor PCB circuit boards:

1. Surface treatment pad fingerprints: Fingerprints are hand sweat stains, and their 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 hazards of fingerprints in the circuit board manufacturing process

1. . The bare hand touching the board before the solder mask will cause the solder mask to fall, causing the adhesion of the green oil to deteriorate, and it will bubble and fall off during the hot air leveling;

2. . During the process of the immersion gold board after solder mask and before packaging, touching the board surface with bare hands will cause the board surface to be unclean and cause poor solderability or poor bonding;

3. . The bare object touches the board in a very short time to make the copper on the board surface chemically react, causing the copper surface to oxidize. After a longer time, obvious fingerprints will appear after electroplating, and the uneven coating will cause serious defects in the appearance of the product;

4. . Printed wet film or silk-printed circuit and PCB circuit board surface before lamination has fingerprint grease, which can easily cause the adhesion of dry/wet film to decrease, and lead to infiltration and plating separation during electroplating, and gold plate is easy to The pattern of the board surface is formed, and the board surface is oxidized after the solder mask is completed, and the color of yin and yang appears.

If the above phenomena are not standardized and eliminated, it will damage the qualified rate of the product and the one-time pass rate, resulting in a long production and processing cycle, a high rework rate, and a low on-time delivery rate, which will damage the company's image in the eyes of customers.

3. How to prevent bare hands from touching the board is the key to radically eliminating fingerprints

1. . Every employee is required to develop a good habit of picking and placing boards;

2. . Carry gloves and finger cots with you;

3. . Always wear gloves (such as cloth gloves, rubber gloves, finger cots, etc.) in the process where gloves can be worn;

4. . Lead by example, teach by example, set up a role model, and engrave a jingle in your mind: "Hold the edge of the board in both hands, lay flat, palm as the axis, and rotate coaxially."

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