Due to the precise technology and certain environmental and safety adaptability required for electronic products, significant progress has been made in the electroplating technology of circuit boards. During PCB electroplating, the chemical analysis of organic compounds and metal additives is becoming increasingly complex, and the chemical reaction process is becoming more precise.

However, even so, the problem of burnt edges still occurs occasionally during electroplating of circuit boards. So what is the root cause of the problem?

The main reasons for the burnt edges of circuit boards during electroplating are:

1. Tin lead anode too long

If the anode is too long and the workpiece is too short, the power lines at the lower end of the workpiece will be too dense, which is prone to burning; When the distribution of anodes in the horizontal direction is much longer than the length of the workpiece placed horizontally, the power lines at both ends of the workpiece are dense and prone to burning.

2. Insufficient tin lead metal content

Insufficient metal content and slightly high current make it easy for H+to discharge by chance, resulting in a decrease in the diffusion and electromigration speed of the plating solution, leading to burning.

3. The current density is too high

Each plating solution has its optimal current density range.

The current density is too low, the coating grains become coarse, and even the coating cannot be deposited. When the current density increases, the cathodic polarization effect increases, resulting in a denser coating and an increase in plating rate. But if the current density is too high, the coating will be burnt black or burnt;

4. Insufficient circulation or stirring of the tank solution

Stirring is the main means to improve the convective mass transfer rate. By using cathode movement or rotation, relative flow can occur between the liquid layer on the surface of the workpiece and the plating solution slightly away; The greater the stirring intensity, the better the convective mass transfer effect. When the mixing is insufficient, the surface liquid flows unevenly, leading to the burning of the coating.

5. Insufficient additives

In simple salt electroplating, if too many additives are added, the additive film layer generated by adsorption is too thick, making it difficult for the main salt metal ions to penetrate the adsorption layer and discharge. However, H+is a small proton that is easy to penetrate the adsorption layer and discharge hydrogen, and the coating is prone to burning. In addition, excessive additives have other side effects, so any additives or brighteners must adhere to the principle of adding less and more frequently.

In addition, there are other reasons that can cause burning

Organic pollution; Metal impurity pollution; Excessive lead content in the coating; The anode mud falls into the tank; The hydrolysis of fluoroboric acid produces the attachment of lead fluoride particles.