LEAD FRAME

PURPOSE:To contrive the formation of a bonding part having good bonding characteristic by a method wherein an oxide film 80Angstrom or less in thickness and 0.25mum or less in surface roughness is formed on the surface of a lead frame. CONSTITUTION:A Cu plating of 1-5mum thickness is applied on the surface of the lead frame made of Cu alloy by electroplating using e.g. a bath of cupric sulfate. Next, the surface roughness is adjusted to 0.25mum or less by treatments such as buffing, mirror rolling, chemical polishing, and electrolytic polishing. The method of ultrasonic heating thermocompression bonding, high-frequency heating, or laser heating is adopted as the means of bonding Au wires to the lead frame, at the time of thermocompression bonding, the bonding part is sealed with an inert gas of N2 or Ar, or the inert gas is sprayed there. Bonding is carried out by setting the pressure at 15-60g, the output in ultrasonic heating at 0.1-1.0W, and the time at 10-60ms, and the oxide film 80Angstrom or less in thickness is formed on the surface of the lead frame. This manner yields bonding strength and excellent interface-exfoliation resistance.