Interconnection of Cu wire/Au plating pads using parallel gap resistance microwelding process

Because of the complicated configuration in MEMS devices, significant technical challenges are presented for the interconnection of dissimilar materials. Since tin soldering is an effective method for joining dissimilar materials, there are still some reliability problems in later service process, such as remelting of Sn solder, excessive microstructure evolution. In the present work, a parallel gap resistance microwelding method was developed for forming reliable Cu wire/Au plating interconnection. In an attempt to avoid fragile electronic components, an ohmic contact tip onto the electrodes was utilized. Experimental results revealed that solid state welding was obtained with a relatively electric current intensity within 20 ms. No weld nugget was generated at the Cu/Au interface. The joule heat-induced temperature affected microstructures as well as mechanical properties of the joints, mainly depending on three parameters (welding voltage, welding time and electrode force). The maximum joint breaking force was 24 g with the welding voltage of 0.5 V for 16 ms and under the pressure of 0.56 N. The ANSYS simulation results indicated that the weld geometry changed with welding time.