Forming High Aspect Ratio Bumps Available Bonding at Low Temperature on Fine Pitch Line Wire by Gravure Offset Printing
In recent years, increased use of FHE where printed electronics and conventional silicone IC-chips technology fused is expected. Flexible boards with IC-chips are being explored for the development of wearable devices, sensor tag which can be installed in the curved surface, and IoT. The wire bonding method has been common for the mounting to the rigid board, but the mainstream is moving to flip-chip method with boards becoming flexible. Demand to fine pitch line and bumps increases with IC-chip refining and becoming highly functional. It is required to perform the heat-treatment at low temperature to bond IC-chips to a low-cost and flexible substrate such as PET or PEN. These plastic films cannot be used in a conventional method with solder ball or solder paste because the method needs a high temperature of more than 200 degrees Celsius.