Sophisticated HDI flexible substrates for advanced applications

Miniaturization driven PWBs used for implantable medical devices, hearing aids and other medical and scientific applications, as well as for advanced products in the printing and telecommunication industry, ask for finer and finer structures. Via/pad geometries down to 40/100 microns with 20 microns line and spaces are required, for example, in advanced medical ultrasound probes and for detectors in particle accelerators. State‐of‐the‐art image transfer processes allow extremely dense and precise conductor geometries on very thin flexible circuits with one to six or even more copper layers. These modern image transfer processes, together with an optimised plating process and the combination of UV‐YAG laser and microwave plasma drilling for mass microvia formation, result in a very efficient manufacturing technology for highly reliable HDI boards. This HDI manufacturing technology, applied to polyimide materials that can operate over a wide range of temperatures and to new flexible liquid crystalline polymer (LCP) materials with outstanding radio frequency properties, opens up a completely new world of exciting opportunities.