Flexible High Performance TAB Inner Lead Bonding with a Laser Available to Purchase

MCC has been developing the use of flashlamp pulsed Nd:YAG laser technology to bond TAB leadframes to bumped IC die. With basic equipment, the process has been proven in a laboratory scale environment. As a result, MCC recently licensed a vendor to manufacture the equipment so that it can be used in prototype and later in production environments. This project was initiated to develop a benign alternative for thermocompression gang bonding, particularly for applications where IC bond pads would be located over active circuitry. In addition, because the laser beam's positions are computer controlled, the process has shown to be very desirable for bonding conventional devices with peripheral pads, especially in high product mix applications. Bond rates of 40 bonds/second have been demonstrated at MCC. The first production prototype will bond at 60–80 bonds/s and it is anticipated that, with further development, the full production equipment will bond at 200 bonds/s. The process that is most mature at the time of writing is for bonding tin plated copper leads to gold bumps. This system allows formation of reliable bonds because the formed bonds consist primarily of copper and gold. The bonds are at least as strong and reliable as with other methods of TAB bonding. Bonds with this metallurgical system have been subjected to severe environmental testing without failure. This paper will present results of laser inner lead bonding, the equipment used to develop it and the expectations of the future equipment as well as the future of the technology itself.