Abstract
This thesis is dedicated to research the Micro Ball Grid Array (μBGA) technology which can be used in package. When μBGA is used in bonding, different thermal expansion coefficient between different layers will cause a stress between the bonding place as thermal treatment, and then destruct the solder or device structure. In this thesis, we choose Benzocyclobutene (BCB) as the stress buffer layer and dielectric of the solder because of it's several advantage properties：low dielectric constant, low water absorption, low stress, and high bending strength which can efficiently increase the bonding reliability. We use Cr/Cr/Cu/Cu sandwich structure as the Under Bump Metallurgy (UBM) and the redistribution layer. Electroplated copper layer in sandwich structure can achieve enough thickness to be a efficient diffusion barrier. PbSn is deposited by E-Beam Evaporation and reflowed forming a solder. We will discuss the effect of time and temperature on reflow. Finally, we flip chip by solder and measure the relationship between resistance and temperature.