Aluminium wedge-wedge wire bonding on thermoplastic substrates made by LPKF-LDS® technology

Due to its high capability for miniaturisation as well as for reducing the number of components and process steps, MID (Moulded Interconnect Devices) technology is a very interesting alternative for packaging of miniature devices. Meanwhile several MID based products have been introduced to industry mainly in the field of medical technology, automotive engineering, automation and communication technology. Laser based MID technologies enable the fabrication of fine pitch circuitry in three dimensions on complex thermoplastic devices. The assembly of bare dies extends the application range of MID as a system carrier for micro systems and micro mechatronic systems. Wire bonding is an important assembly technology for bare dies. However for wire bonding the roughness of the electroless plated conductor path on the MID substrate has to be minimised. In this paper we report on basic investigations of aluminium wedge-wedge wire bonding on laser patterned and metallized MID using LPKF-LDS® technology. Comprehensive studies have been carried out to optimize the set of laser parameters with regard to roughness and adhesion of electroless plated Cu/Ni/Au layers on MID substrates. Furthermore the influence of CO₂ snow jet cleaning or stamping after laser patterning have been investigated as leveling steps in order to decrease roughness. A significant reduction of the average surface roughness was achieved for different laser-activatable thermoplastics. The feasibility of aluminium wedgewedge wire bonding on leveled and electroless plated laser-activatable substrates has been tested successfully.