PCB Technical - The quality of etching process in PCB circuit board proofing

In the proofing of the PCB circuit board, the copper foil part that needs to be kept on the outer layer of the board, that is, the pattern part of the circuit, is pre-plated with a lead-tin anti-corrosion layer, and then the remaining copper foil is etched away by chemical means, which is called Etching.
As the last step of the circuit board from the light board to showing the circuit pattern, what quality issues should be paid attention to in etching?
The quality requirement of etching is to be able to completely remove all copper layers except under the resist layer. Strictly speaking, the etching quality must include the consistency of the wire line width and the degree of side etching.
The problem of undercutting is often raised for discussion during etching. The ratio of the undercut width to the etching depth is called the etching factor; in the printed circuit board industry, a small undercut or low etching factor is the most satisfactory. The structure of the etching equipment and the etching solutions of different compositions will affect the etching factor or the degree of side etching.
In many ways, the quality of etching has existed long before the circuit board enters the etching machine. Because there are very close internal connections between the various processes of PCB proofing, there is no process that is not affected by other processes, and does not affect other processes. Many of the problems identified as etching quality actually existed in the process of removing the film or even before.

Theoretically speaking, PCB proofing enters the etching stage. In the pattern electroplating method, the ideal state should be: the total thickness of the electroplated copper and lead tin should not exceed the thickness of the electroplating photosensitive film, so that the electroplating pattern is completely covered on both sides of the film. The "wall" blocks and is embedded in it. However, in actual production, the plating pattern is much thicker than the photosensitive pattern; because the plating height exceeds the photosensitive film, a tendency of lateral accumulation occurs, and the tin or lead tin resist layer covering the lines extends to both sides to form "Edge", covered a small part of the photosensitive film under the "edge". The "edge" formed by tin or lead tin makes it impossible to completely remove the photosensitive film when removing the film, leaving a small part of "residual glue" under the "edge", causing incomplete etching. The lines form "copper roots" on both sides after etching, which narrows the line spacing, causing the printed board to not meet customer requirements and may even be rejected. Rejection will greatly increase the production cost of PCB.
In PCB proofing, once there is a problem in the etching process, it is bound to be a batch problem, which will eventually cause great quality risks to the product. Therefore, it is particularly important to find a suitable PCB proofing manufacturer. ipcb is committed to solving the pain points of difficult, precision boards and special boards in PCB proofing. In every aspect of PCB proofing, the technology can be well controlled, and high-quality PCB proofing Products are delivered to customers.