Wire-bonding machine optimization using Taguchi method

Wire-bonding is a complex process due to the variety of parameters an the new automated machines. The need for high bonding yields of the costly ceramic VLSI packages requires the beat possible process optimization Such an optimization seeks for complementary objectives - to define the best parameter levels (power, head force, time, others...) with regards to the highest yield, - to minimize process parameters change from one series to another, - to learn about parameters interdependency, in order to use a relevant procedure for special series needing accurate optimization. The high interdependancy of the parameters, the large number of pieces needed in a conventional optimization experiment plan and the lack of any clear performance criteria show how the objectives above are difficult to achieve. A two-step TAGUCHI experiment gave us the following information: - comparison of the interest of two performance criteria pull-test and bond width, -.definition of the best parameter levels with regards to reproducibility, - demonstration of significant parameter interactions, - influence of die lots on process parameters. The study presented here, using less then 30 packages, enabled us to set-up a wire-bonding machine in a short time with a minimized cost.