Advanced plating photoresist development for advanced IC packages

The advanced IC packaging technologies such as 3D-TSV, 2.5D interposer, PoP and Flip-Chip wafer micro-bumping are being implemented for consumer electronic products like as mobile phones, tablets, and so on. The form factor of consumer product trends toward small and thin which driving IC packaging toward smaller, thinner and more complicated. A negative tone photoresists has been developed for re-distribution metal layers, C4 and micro bumps by alloy solder plating used in 3D-TSV, 2.5D interposer, PoP and Flip-Chip packages. The key technology of plating photoresists for advanced packages is high resolution allowing for high aspect ratio patterning capability that covers a wide range of film thicknesses. An example of such applications is in advanced PoP packaging designs which require a thick film material that has high resolution capability, along with high aspect ratio performance. The THB series is an acrylate cross-linker system negative tone photoresists with photo radical initiator. The formulation shows excellent chemical resistance with good stripability to various plating solutions such as Cu, Ni, Sn/Ag and Au. In TSV process, via filling and high dissolution rate are key processes to form micro-bump. The high resolution photoresists can be used to create fine pitch conditions for package downsizing. The THB series shows good patterning performance from below 10um to above 100um film thickness conditions. The material design and key properties of plating resist with high resolution and high aspect ratio performance with a wide range film thickness ranges are studied and discussed.