"Fingerprint" hazards and avoidance methods in PCB board pads

Author:ComeFrom:Date:2019-04-23 11:54:26Hits:150
In the PCB industry, "fingerprints" in surface treatment pads are a major hazard to PCBs and one of the main causes of poor PCB waste and degraded end-user reliability. PCB board manufacturing is almost every step of the manual operation. Only members of the electronics manufacturing industry can develop good habits and eliminate the bare touchpad to reduce or eliminate the damage of fingerprints on the board. Fingerprint and board contact opportunities are frequent during board manufacturing and processing, so fingerprinting has become the most difficult problem in the industry. The following are the causes, hazards, and avoidance of "fingerprints" that cause poor PCB boards.
1. Surface treatment pad fingerprint: Fingerprint is hand sweat stain, its main components are as follows:
(1) water;
Cosmetics and skin care products;
(3) inorganic salts (such as Nacl, etc.);
(4) fatty oil (non-mineral);
(5) Various dirt (or dirty gloves) that are touched by bare hands.
2. The harm of fingerprints in PCB manufacturing
(1) The bare hand contact plate before welding will cause poor adhesion of green oil under the welding resistance, and will foam and fall off during hot air rectification.
(2) During the process from soldering resistance to pre-packaging, the exposed touchpad surface may result in unclean surfaces and poor solderability or adhesion;
(3) The nude touches the board in a short period of time, causing a chemical reaction of copper on the surface of the board, resulting in oxidation of the copper surface. After a period of time, the fingerprints were obvious after electroplating, and the uneven coating caused the appearance of the product to be seriously bad.
(4) The fingerprint grease on the wet or silk screen board and the surface of the PCB circuit board before embossing tends to cause the adhesion of the dry/wet film to decrease, resulting in separation of plating and plating during the plating process. The gold plate is easy to form a pattern on the surface of the board. After the welding resistance is completed, the surface of the board will be oxidized and a cloudy color will appear.
If the above phenomenon is not standardized and eliminated, the pass rate of the product will be damaged. The one-pass rate will lead to long production and processing cycles, high rework and replenishment rates, and low on-time delivery rate, which will damage the company's image in the eyes of customers.
3. How to eliminate the bare touchpad is the key link to eliminate fingerprints
(1) Require each employee to develop good habits of taking and going to bed;
(2) Carry gloves and gloves with you;
(3) Wear gloves (such as cloth gloves, rubber gloves, gloves, etc.) during the wearing of gloves.
(4) Lead by example, set the image model, and engrave a smooth slogan in the mind: "Two hand-held edges, plane, center of the palm is the axis, coaxial rotation".

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