Generally, immersion gold treatment can be divided into these stages: pre-treatment (degreasing, micro-etching, activation, post-immersion), and post-treatment (washing waste gold, washing with DI water, and drying).
It should be noted that in the chemical nickel-gold process, because there are small holes, water washing between each step is necessary, and special attention should be paid.
Between the microetching agent and the palladium activator, after the microetching, the copper is easy to fade. In severe cases, the palladium plating layer will be uneven, which will cause the nickel layer to malfunction. If the circuit board is not washed well, the oxidant from the microetching will prevent the palladium from deteriorating. As a result, the deposition affects the effect of the immersion gold, thereby affecting the quality of the board.
Between the following palladium activator and chemical nickel, palladium is the most dangerous impurity in the chemical nickel process. Very small amounts of palladium will cause the bath to decompose naturally. The concentration of palladium is very low, but it should be washed well before entering the electroless plating tank. It is recommended to use two washings with air stirring.
Between these two steps, the transfer time will easily passivate the nickel layer, resulting in uneven immersion gold and poor bonding force. This is easy to cause dumping of gold and tin.
After immersion in gold, in order to maintain solderability and ductility, fully wash with water after gold plating (distilled water can be used for the last wash), and completely dry, especially in the hole.
The pH and temperature of the nickel-immersed tank should be increased, adjusted with less than 50% ammonia water, and lowered, adjusted with 10%V/V sulfur 0 acid. All additions must be poured slowly and continuously stirred. PH value measurement should be carried out when fully agitated to ensure a balanced plating solution concentration. The higher the temperature, the faster the plating speed. When plating a thick layer, the low temperature is used to slow down the needle emergence. When not in operation, do not keep the temperature at the operating temperature, which will cause the decomposition of the reducing agent and stabilizer components.