PCB Technical - Why is the edge of the high-frequency circuit board burnt during electroplating

Since electronic products require sophisticated technology and a certain degree of environmental and safety adaptability, it has promoted considerable progress in high-frequency circuit board electroplating technology. In the electroplating of high-frequency circuit boards, the chemical analysis of organic matter and metal additives is becoming more and more complicated, and the chemical reaction process is becoming more and more precise.

But even so, high-frequency circuit boards will still have the problem of scorching the edges of the board from time to time during electroplating. So what is the source of the problem?

The reasons for the scorching of the edges of the high-frequency circuit board during electroplating are roughly as follows:

1. Insufficient tin and lead metal content

The metal content is insufficient, the current is slightly larger, H+ is easy to be discharged by the machine, and the diffusion and electromigration speed of the plating solution body become slow, resulting in scorching.

2. The tin-lead anode is too long

When the anode is too long and the workpiece is too short, the power lines at the lower end of the workpiece are too dense and easy to scorch; 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 easy to scorch.

3. The current density is too high

Each plating solution has its best current density range.

If the current density is too low, the grains of the coating will become coarse, and the coating cannot even be deposited. When the current density increases, the cathodic polarization effect increases, so that the coating is dense and the coating speed increases. But if the current density is too large, the coating will be burnt or scorched;

4. Insufficient bath circulation or stirring

Stirring is the main means to increase the speed of convective mass transfer. Using the cathode to move or rotate, there can be a relative flow between the liquid layer on the surface of the workpiece and the plating solution at a distance; the greater the stirring intensity, the better the convective mass transfer effect. When the stirring is insufficient, the surface fluid will flow unevenly, which will cause the coating to burn.

5. Insufficient additives

In simple salt electroplating, if the additive is added too much, the additive film layer produced by adsorption is too thick, and the main salt metal ions are difficult to penetrate the adsorption layer and discharge, but H+ is a small proton that easily penetrates the adsorption layer and discharges hydrogen, and the coating is easy Burnt. In addition, too many additives have other side effects, so any additives and brighteners must adhere to the principle of adding less frequently.

In addition, the cause of the scorch is

Organic matter pollution; metal impurity pollution; excessive lead in the coating; anode mud falling into the tank; fluoroboric acid hydrolysis produces adhesion of lead fluoride particles.

ipcb is a Printed Circuit Board(prototype & standard PCB) Fabrication and PCB Assembly(PCBA) manufacturer. Specialized in manufacturing Microwave PCB, HDI-Multilayer PCB, IC Substrate, IC Test board, and Rigid-Flex PCB