Fingerprint "is a major scourge of PCBs and one of the main reasons for poor scrapping of PCBs and deteriorating reliability of end users. And almost every step of PCB manufacturing involves manual operations. Only by cultivating good habits among every member of the manufacturing industry and preventing bare hands from touching the board, can the harm of finger marks on PCB boards be reduced or eradicated. During PCB processing, there are frequent opportunities for hand to board contact, making finger printing the most challenging issue in the industry. Here are the reasons, hazards, and avoidance methods for finger prints that can lead to poor PCB boards:

    1. Finger prints: Finger prints are hand sweat stains, and their main components are as follows:

    A. Water

    B. Inorganic salts (such as NaCl)

    C. Fatty fats (non mineral)

    D. Cosmetics and skincare products E. Various types of dirt touched by bare hands (or dirty gloves)

    2. The Harm of Finger Printing in PCB Manufacturing Process

    A. The bare object touching the board causes a chemical reaction of copper on its surface in a very short time, leading to oxidation of the copper surface. After a slightly longer period of time, obvious fingerprints appear after electroplating, resulting in uneven coating and causing serious defects in the appearance of the product.

    B. The bare hand touching the board before the solder mask can cause the solder mask to fall off, resulting in poor adhesion of the green oil and blistering and detachment during hot air leveling.

    C. During the process from soldering resistance to packaging, touching the surface of the gold plate with bare hands can result in unclean surface and poor solderability or bonding.

    D. The wet film or silk screen printing circuit and the surface of the board before pressing have fingerprint like grease, which can easily cause a decrease in the adhesion of the dry/wet film. During electroplating, it can cause infiltration and separation of the coating, and the gold plate can easily cause surface patterns. After the completion of resistance welding production, the board surface oxidizes, resulting in negative and positive colors.

    If the above phenomenon is not standardized and eliminated, it will damage the qualified rate and one-time pass rate of products, resulting in long production Makespan, high rework and replenishment rate, and low on-time delivery rate, which will damage the company‘s image in the eyes of customers.

    3. How to Prevent Bare Hand Touching the Board is a Key Link in Radical Treatment of Fingerprint

    A. Require each employee to develop a good habit of picking and placing boards. B. Carry gloves and fingertips with you. C. Always wear gloves (such as cloth gloves, rubber gloves, finger covers, etc.) in processes where gloves can be worn

    D. Set an example, lead by example, set a good example, and imprint a catchphrase in your mind: "Two handheld edges, flat and flat, palm axis, coaxial rotation.