Lignin as Renewable Raw Material for Applications in Electronics

In the long term, renewable raw materials should be used as favorite materials for applications in the electronic industry, but very high specifications for substrate materials make the use of biopolymers in electronics difficult. In this work, thermoplastic lignin is used as renewable raw material for electronic applications, precisely for a substrate material for printed circuit boards (PCBs). The results show that lignin-based substrate materials in a thickness range of 0.5 mm respectively 0.8 mm can successfully be produced via film extrusion using a slot die followed by a calender unit. With a glass fiber reinforcement content of similar to 24 vol. %, the substrate material shows good mechanical behavior (tensile tests and falling dart tests). The water absorption and the adhesion of the copper foil are in the range of FR 4, which is the standard substrate material for printed circuit boards. However, the maximum operating temperature, the time to delamination and the coefficient of thermal expansion are below the values of FR 4. Nevertheless, the developed lignin based substrate material can successfully be used as a prototype circuit board in a non-automated process.