PCB manufacturing increasingly needs high aspect ratio, small hole PCB electroplating process.It is the driving force for the development of multi-layer PCB manufacturing technology.Because of the reliability of the hole coating, it plays a key role in the PCB application.How to ensure high aspect ratio deep hole electroplating is the most important problem that must be faced by all printed circuit workers.For this, a lot of research departments begin to carry on planned development and development.There are many methods to extract striatas from current scientific data, including pulsed electroplating, chemical vapor deposition, solution impact electroplating, all-chemical copper plating and advanced (high acid and low copper) air stirring.This part of the technology is introduced as follows:
Pulse electroplating technology
Pulse electroplating technology, already used in electroforming process, is a mature technology.However, a lot of process tests must be carried out to apply in high aspect ratio hole electroplating.Because of pulse power supply is different from general dc power supply, it is through a switch element makes the speed of the rectifier to US on/off, to provide cathodic pulse signal, when the rectifier is in a state of closed, it is more effective than direct current to the hole of the boundary layer added copper ions, so that the high aspect ratio of the printed circuit board more uniform sediment.At present, the developed pulse rectifier is used in the closed horizontal electroplating production line.
The "timing counter-pulse" is used to make the current alternately electroless and electroless (that is, anodic dissolution) in the mode of power supply according to time, so that the deposition of electroplated copper is difficult to obtain the corresponding thickness of copper layer in the conventional power supply mode.When the printed circuit board on the cathode is in the reverse current, the copper layer in the high-current density area of the orifice can be dissolved rapidly. Due to the effect of additives, the influence on the low-current density area is very small. Therefore, the thickness of copper layer in the orifice and the thickness of the plate surface will gradually become equal.