Wafer-level chip scale packaging (WL-CSP) has been intensively being
developed because of its advantages such as miniaturizing, thinning
and lightening packaged chips, also realizing low manufacturing cost.
Therefore, methods have been proposed for production of wafer-level
chip scale packages. Fujikura has developed a novel structure and
fabrication process of WL-CSP, build up with metal-covered polyimide
post. A distinctive feature is a structure of the post is composed
of elastic polyimide and copper cap. Elasticity of the core leads
to absorb thermally induced strain between maintaining good mechanical
properties. Furthermore, thick redistribution trace lower electrical
resistance, resulting decrease in power consumption.
