In recent years, with the rapid development of giant computer and modern communication field, the design of PCB is more and more high density interconnection, and continuously improve the quality of PCB requirements, the design of high density interconnection PCB manufacturing is facing a serious challenge many technology problems. The design of PCB high density interconnect leads to PCB deep hole copper plating, and the deep hole electroplating technology with high aspect ratio is one of the key problems. Copper plating is a key process in PCB process. As a metallization hole to realize the conduction between PCB layer and layer, the single copper thickness requirement can not reflect the hole performance, especially the reliability. At present, the detection methods for the reliability of PCB hole wall are also booming, such as fast thermal cycle (HATS), internal interconnect stress test (IST), hot and cold cycle (THERMALSHOCK), etc.. It is found that the thickness of electroplated copper is only an index affecting the surface performance of the PCB, but the ductility of the coating is the direct influence on the reliability of the hole.
Evaluation of plating performance indicators is usually available:
Copper thickness (including copper thickness uniformity, hole copper uniformity, deep plating ability)
Coating ductility (IST or hot and cold cycles, thermal shock, etc.)
The copper thickness and the ductility of the coating are the key to the electroplating performance. In the copper thickness, deep hole electroplating processing difficulty is decided Kong Tong uniformity is deep plating ability; coating ductility is the core coating reliability lies, so it is necessary to do further research on these two aspects. The plating properties mentioned herein refer to the ability of deep plating and the ductility of the coating.
The key factors that affect the electroplating performance are concentrated on the process control methods, such as acid copper ratio, current density parameter, light composition ratio, etc.. The development of the law of things or interactive influence expressed by mathematical equations, for us to solve problems, find problems and prevention problems clearly pointed, simple direction.
The thickness and aperture of the plate are designed by customers. In order to improve the deep plating ability, the current density can be reduced and the conductivity of solution can be improved. So the way to improve the deep plating ability is:
1. Appropriate low current density
2, high solution conductivity (high acid low copper, Cl can increase the conductivity of solution)
3, the plate according to the plate thickness and thickness diameter ratio classification processing
The appropriate low current density and low current density will seriously affect the crystallization of copper plating, which is further described in the part of the ductility of the coating.
1) the problem of deep hole electroplating is characterized by deep plating ability and coating ductility.
2) the method of solving the deep plating capacity: the appropriate low current density; the ratio of high acid and low copper; looking for the appropriate low current density and limiting current density method: polarization curve method.
3) solution of coating ductility: as high as possible current density. Find the highest current density method: measure the polarization curve and find the limit current density.