One of the unique processes in flexible printed board manufacturing is the processing of the cover layer. There are three methods for processing the cover layer: cover film, screen printing, and photocoating. Newer technologies have been developed to offer more options.
The processing of FPC cover film is divided into three parts: 1. Screen printing of FPC overlay 2. FPC cover film 3. FPC photocoating layer
Screen Printing of FPC Overlay:
The lack of cover layer in screen printing results in inferior mechanical properties compared to laminated cover film, but it is more cost-effective. This method is commonly used in civilian products and flexible printed boards in automobiles that do not require frequent bending. The process and equipment used are similar to printing solder mask on rigid printed boards, but the ink materials are different. It is important to select inks suitable for flexible printed boards.
UV curable and heat-curable inks are available in the market. UV-curable inks offer quick curing times but may have poorer mechanical and chemical resistance properties. They may not be suitable for bending or harsh chemical environments. It is especially crucial to avoid electroless gold plating with UV-curable inks, as the plating solution can seep into the cover layer and cause it to peel off. Thermosetting inks require 20-30 minutes for curing, requiring longer drying tunnels for continuous curing, typically using intermittent ovens.
The processing of FPC cover film is divided into three parts: 1. Screen printing of FPC overlay 2. FPC cover film 3. FPC photocoating layer
Screen Printing of FPC Overlay:
The lack of cover layer in screen printing results in inferior mechanical properties compared to laminated cover film, but it is more cost-effective. This method is commonly used in civilian products and flexible printed boards in automobiles that do not require frequent bending. The process and equipment used are similar to printing solder mask on rigid printed boards, but the ink materials are different. It is important to select inks suitable for flexible printed boards.
UV curable and heat-curable inks are available in the market. UV-curable inks offer quick curing times but may have poorer mechanical and chemical resistance properties. They may not be suitable for bending or harsh chemical environments. It is especially crucial to avoid electroless gold plating with UV-curable inks, as the plating solution can seep into the cover layer and cause it to peel off. Thermosetting inks require 20-30 minutes for curing, requiring longer drying tunnels for continuous curing, typically using intermittent ovens.
