In the manufacturing process of PCB, immersion gold is a crucial surface treatment link, which is related to the subsequent performance, appearance and reliability of electrical connection of PCB board.
In the actual operation process, there are often some problems related to immersion gold such as leakage plating, false leakage plating, short circuit of continuous pieces and burrs of infiltration plating. Let's analyze the causes of leakage plating and false leakage plating (gold is applied but the color is obviously different) in depth as follows:
Poor pretreatment
If the surface of the PCB board is not cleaned before immersion gold, there are oil stains, oxides or impurities, which will affect the deposition of gold ions, resulting in some areas unable to be plated with gold normally, resulting in leakage plating. As for the color difference problem in false leakage plating, it may be that the surface state of different areas is changed inconsistently during the pretreatment process, which makes the adhesion and growth of the gold layer different during the subsequent immersion gold, and then presents color differences.
Abnormal plating solution composition
Imbalanced proportions of the various components in the plating solution, such as too low gold salt concentration, inappropriate complexing agent content, insufficient or ineffective additives, etc., will affect the gold deposition effect, resulting in missed plating or poor quality of the deposited gold layer, resulting in color differences.
Poor conductivity
During the electroplating process, if the contact between the PCB board and the hanger is poor, resulting in uneven current distribution, some parts cannot obtain enough current to drive gold ion deposition, and missed plating is likely to occur.
Unreasonable process parameters
If the electroplating time is too short, the current density is too small, etc., the gold layer will not be able to completely cover the area to be plated, resulting in missed plating; and unstable or inappropriate parameter settings may also cause uneven growth of the gold layer, causing false missed plating with color differences.
Mask problem
If a mask is used to limit the gold immersion area, and the mask is damaged or not tightly fitted, it may cause gold to be plated in areas that should not be plated, or affect the plating effect of normal areas, resulting in missed plating and color abnormalities.
All kinds of problems that arise in the immersion gold process have their complex causes, which require us to carefully investigate and analyze from multiple aspects, whether it is pre-treatment, plating solution composition, process parameters, or graphic transfer, design links, etc., any negligence may lead to problems.
