In the past few years, the focus of the PCB market has shifted from computers to communications. The use of HDI boards in mobile terminals has become the main point of PCB growth. Mobile terminals represented by smart phones are driving HDI boards at higher density and lighter weight.
I. Development trend of printed circuit boards
(a) thin line
All PCBs are developing toward high-density thin lines, and HDI boards are particularly prominent. Ten years ago, the HDI board was defined as having a line width/line spacing of 0.1 mm/0.1 mm or less, which is currently 60 μm in the industry and 40 μm in the advanced industry.
The PCB circuit pattern is formed. Traditionally, the photoetching after chemical etching process (subtraction method) is performed on the copper foil substrate. This practice involves many processes, difficulties in control, and high costs. Current fine line production tends to semi-additive or improved semi-processing methods
(B) Semi-additive method lamination substrate
The semi-additive hotspot is now using insulating dielectric film lamination. SAP is more advantageous than MSAP in terms of fine line implementation and manufacturing cost. The SAP layer is made of thermosetting resin, and the via hole and the circuit pattern are formed by electroplating of copper after laser drilling.
At present, the international HDI layered materials use epoxy resin with different curing agents to add inorganic powders to improve the material rigidity and reduce the CTE, and also use glass fiber cloth to enhance the rigidity.
The future development trend. The BGA and CSP fine-pitch carrier boards will continue, while the non-core boards and four- or more-layer carrier boards will be used more. The roadmap shows that the feature sizes of the carrier boards are smaller and the performance focuses on low dielectric properties and low Thermal expansion coefficient and high heat resistance, in pursuit of performance goals based on the pursuit of low-cost substrates.
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