Oxidation analysis and improvement methods of Immersion pcb board

Oxidation analysis and improvement methods of Immersion pcb board

Immersion gold PCB board oxidation instructions:

The oxidation of the gold-plated circuit board of the circuit board manufacturer is that the gold surface is contaminated by impurities, and the impurities attached to the gold surface are oxidized and discolored, which leads to the gold surface oxidation which we often say. In fact, the statement of gold surface oxidation is not accurate. Gold is an inert metal. Under normal conditions, oxidation does not occur. The impurities attached to the gold surface, such as copper ions, nickel ions, and microorganisms, are easily oxidized and deteriorated under normal conditions to form gold surface oxidation. Object.

Through observation, it is found that the oxidation of the gold plate has the following characteristics:

1. Improper operation causes contaminants to adhere to the gold surface, such as: dirty gloves, finger-contact gold surfaces, gold plates and dirty countertops, gasket contact pollution, etc.; such oxidation area is large, may occur at the same time On a plurality of adjacent pads, the appearance is lighter and easier to clean;

2. Half plug hole, a small range of oxidation near the via hole; this type of oxidation is caused by the yao water in the via hole or the half plug hole not being cleaned or the residual water vapor in the hole, and the yao water slowly diffuses along the hole wall in the storage stage of the finished product to The surface of the gold forms a dark brown oxide;

3. Poor water quality causes impurities in the water to be adsorbed on the gold surface, such as: water after immersion gold, water washing of the finished washing machine, such oxidation area is small, usually appear at the corners of individual pads, which is obvious The water stains; the gold plate will retain water droplets on the pad after washing. If the water contains more impurities, the water will quickly evaporate and shrink to the corners when the plate temperature is high. After the water is evaporated, the impurities will solidify. At the corners of the pad, after washing with gold, the main pollutants of the washing machine of the finished washing machine are micro-bacteria, especially the tank using DI water is more suitable for fungus reproduction. The best test method is bare touch. The dead angle of the groove wall to see if there is a feeling of slipperiness, if any, indicating that the water body is already contaminated;

4. Analysis of the customer return board, found that the gold surface is poorly densified, the nickel surface is slightly corroded, and the oxidation contains an abnormal element of Cu, which is most likely due to the poor density of gold nickel and the migration of copper ions. After such oxidation is removed, it will still grow and there is a risk of reoxidation.