Test chip for bump bond yield evaluation in high density flip chip technologies

Modern flip chip technologies for imaging applications have achieved a very high integration level together with the possibility of large assemblies. These developments have resulted in an enormous increase in the total number of bump bonds per assembly. As a result, yield tests become more difficult, and an accurate measurement of it is often discarded. This problem is aggravated in medical applications, as the critical information can be limited to a few pixels, and therefore, yields should be very close to 100%. In these cases, a difference of a few tenths percent in bump bond yield can make the difference between a usable and a nonusable assembly. For this reasons, quantitative and precise measurements of bump bond yield are needed to characterize the quality of any high density flip chip technology. In this contribution, we present a newly developed test chip for quantitative electrical characterization of the bump bond yield of high density flip chip technologies, allowing optimization and statistical control of the process. This test chip facilitates the identification of possible technological problems with precise quantitative yield measurements. It also allows to pin point any localized systematic failure in the bump-bonding process. The test chip has been used to evaluate the yield of different flip chip technologies and has contributed to their fine optimization