With the rapid development of the PCB industry, PCBs are gradually moving towards high-precision fine lines, small hole diameters, and high aspect ratios (6:1-10:1), requiring 20-25µm of copper penetration at the holes. For boards with a line spacing of ≤4µm, electroplating imperfections are a common problem in PCB manufacturing companies. Below, we will discuss in detail the causes of electroplating imperfections during multi-layer PCB prototyping and how to improve them.

　　Causes of Electroplating Imperfections in Multi-layer PCB Prototyping

　　1. Uneven distribution of board patterns: During the electroplating process, isolated lines may have a high potential, causing the plating layer to exceed the film thickness, resulting in imperfections and short circuits.

　　2. Insufficiently thin resist coating: During electroplating, the plating layer may exceed the film thickness, forming PCB imperfections. This is especially true for boards with smaller line spacing, which increases the likelihood of imperfections and short circuits.

　　Methods to Improve Electroplating Thickness in Multilayer PCB Prototyping

　　1. Increase the thickness of the resist coating: Select a dry film of appropriate thickness. If using a wet film, use a low-mesh screen printing method, or increase the film thickness by printing the wet film twice.

　　2. For uneven pattern distribution on the board, appropriately reduce the current density (1.0~1.5A) during electroplating. In daily production, to ensure output, we usually control the electroplating time as short as possible, so the current density used is generally between 1.7~2.4A.

　　However, the current density obtained in isolated areas will be 1.5~3.0 times that of normal areas. This often results in the plating height in isolated areas with small gaps exceeding the film thickness by a large margin. After removing the film, incomplete removal occurs, and in severe cases, the resist coating may be trapped at the edge of the circuit, causing short circuits. It also results in the solder mask thickness on the circuit being too thin.