Oxidation analysis and improvement method of immersion gold pcb board?

Oxidation analysis and improvement method of immersion gold pcb board?

1. Poor oxidation picture of immersion gold plate:

2. Description of immersion gold plate oxidation:
The oxidation of the immersion gold circuit board of the circuit board manufacturer is that the surface of the gold is contaminated by impurities, and the impurities attached to the gold surface are oxidized and discolored, which leads to the oxidation of the gold surface that we often say. In fact, it is not accurate to say that the gold surface is oxidized. Gold is an inert metal and will not oxidize under normal conditions, and impurities such as copper ions, nickel ions, and microorganisms attached to the gold surface are easily oxidized and deteriorated under normal conditions to form gold surface oxidation. thing.

3. Through observation, it is found that the oxidation of immersion gold circuit board mainly has the following characteristics:
1. Improper operation causes contaminants to adhere to the gold surface, such as: unclean gloves, finger cots touching the gold surface, gold plate contacting with unclean countertops, backing plates, etc.; such oxidation area is large and may occur at the same time On multiple adjacent pads, the appearance color is lighter and easier to clean;
2. Half-plugged holes, small-scale oxidation near the vias; this type of oxidation is due to the fact that the water in the vias or half-plugged holes is not cleaned or the water vapor remains in the holes, and the water slowly diffuses along the hole wall during the storage stage of the finished product. A dark brown oxide is formed on the gold surface;
3. Poor water quality leads to the adsorption of impurities in the water body on the gold surface, such as: washing after gold immersion, washing with a finished plate washer, this type of oxidation area is small, usually appearing at the corners of individual pads, which is more obvious After the gold plate is washed with water, water droplets will remain on the pad. If the water body contains a lot of impurities, the water droplets will quickly evaporate and shrink to the corners when the plate temperature is high. After the water evaporates completely, the impurities will solidify in At the corners of the pad, the main pollutants in the washing after gold sinking and the washing of the finished plate washer are microorganisms, especially the tank body using DI water is more suitable for the reproduction of fungi. The best inspection method is to touch with bare hands. Dead corners of the tank wall, to see if there is a feeling of lubrication, if there is, it means that the water body has been polluted;
4. After analyzing the customer’s returned board, it is found that the gold surface has poor compactness, the nickel surface has slight corrosion, and the oxidation place contains an abnormal element Cu, which is most likely due to the poor compactness of gold and nickel and the migration of copper ions. After such oxidation is removed, it will still grow and there is a risk of re-oxidation.

4. Analysis of fishbone diagram of immersion gold plate oxidation (according to human, machine, material, method and ring):

Post time: Mar-28-2022