A bump transfer method for flip chip assembly

In this paper we describe the development of a new chip/wafer bumping technique for flip chip assembly using a bump transfer approach. In this method, high melting temperature bumps such as copper, nickel and gold bumps are fabricated on a low cost, flexible carrier and then transferred onto the target chip/wafer/board for flip chip assembly. Gold bumps and copper and nickel bumps with gold bonding layer have been fabricated on polyimide substrates. The aluminum pads on test chips were re-metallised with electroless nickel and gold layers to facilitate the bonding of bumps to the chips using thermocompression bonding. Parallel bonding and transfer of up to 40 bumps has been achieved.