High-speed gold laser-plating on nickel-plated copper leadframe toward flip-chip packaging

High-speed laser plating (HLP) of gold nanoparticles on a nickel-electroplated copper leadframe has been developed. Dot patterns with a diameter of around 100 μm are formed using an inkjet printer on the substrate, being locally heated with a near-infrared laser in air for a short-time irradiation of less than 1 s. The resulting HLP gold film with a thickness of about 0.3 μm has a bulky structure as well as a high adhesion to the substrate. The successful bonding of gold wire with the gold pad can be utilized to form a stud bump, the height of which can be adjusted to around 60 μm. A flip-chip LED package has been successfully fabricated by employing the present HLP-based method, but reliability tests still need to be done for practical application.