Its core steps mainly include the formation of high-precision printed circuits, the manufacturing of micro-via holes, and the electroplating of surfaces and holes.
Ultrafine Circuits

A few high-tech equipment are high integration and miniaturized. The line width/line spacing of HDI circuit boards of some devices has decreased from the early 0.13 mm (5 mil) to 0.075 mm (3 mil) and has become the existing mainstream standard. The high line width/line spacing requirements enhance the most direct challenge of graphic imaging in the PCB manufacturing process. The existing formation process of lines includes laser imaging (pattern transfer) and pattern etching. Laser Direct Imaging (LDI) technology directly scans the surface of the copper-clad laminate with a photoresist to obtain a refined circuit pattern. Laser imaging technology greatly simplifies the manufacturing process and has become a mainstream engineering process in HDI PCB processing.

2. HDI micro-hole processing

An important feature of the HDI circuit board is its micro vias (diameter≦ 0.10 mm), which are all buried blind vias. The buried blind holes on the HDI board are mainly processed by laser, rest is CNC drilling. Compared with laser drilling, CNC drilling also has its own advantages. When laser drilling through holes in epoxy glass cloth dielectric layer, under the condition of the difference in ablation rate between the glass fiber and the surrounding resin, the quality of the hole will not be ferfect, and the residual glass fiber filaments on the hole wall will affect the reliability of the through hole process. Therefore, the advantages of mechanical drilling at this time are presented. Laser drilling and mechanical drilling technologies are steadily improving the reliability and drilling efficiency of PCB boards.

3. Electroplating

It is crucial to improve the plating uniformity and deep hole plating ability in PCB processing and the board’s reliability. High-frequency sound waves can accelerate the etching ability; permanganic acid solution can enhance the decontamination ability of workpieces, and high-frequency sound waves will stir a certain proportion of potassium permanganate plating solution in the electroplating tank, which will help the plating solution flow into the hole evenly. Thus, the deposition ability of electroplated copper and the uniformity of electroplating are improved. Currently, the copper plating and filling of blind holes is also mature, and copper filling of through holes with different diameters can be carried out. The two-step copper plating and hole-filling method are suitable for through holes with different diameters and high aspect ratios. It has a strong copper-filling ability and can minimize the thickness of the surface copper layer. There are many options for the final finish of the PCB; electroless nickel/gold (ENIG) and electroless nickel/palladium/gold (ENEPIG) are commonly used on high-end PCBs.