A study of flip-chip direct attachment LED COBs with metal core print circuit boards

One of the most critical reliability problems that the LED COBs are facing is the failure of wire bonding connections. The LED COBs would easily break down due to the mechanical shocks or material stress on the gold wire in conventional package roadmaps. Flip chip technologies are excellent options for solving this problem. This paper has been focused on the challenges during the design and manufacturing of flip chip LED COBs based on metal core print circuit boards (MCPCBs). The properties of solder paste, Au/Sn eutectic, and ceramic buffer die-bonding structures are studied. It is found out that the former two COBs have better thermal and optical performance, while the last COB shows good reliability with low leakage current.