Failure detection technique for 2/2um RDL on FOPLP

This paper introduces the test technology of redistribution layer used in FOPLP. In order to lower costs, FOPLP needs to adopt the RDL first process. In addition, it is necessary to guarantee that the package such as 2.5D that formed RDL is non-defective before mounting ICs. Since RDL is mounted on a carrier such as glass, double-sided inspection of the package becomes difficult. It is capacity inspection that can be proposed as this solution. In our work, we have improved the micro capacity tester to the accuracy below femto farad. Using this tester, we have demonstrated defect detection between RDL vias, formation defects of plating etc., in the package manufactured in an actual process. This method also allowed us to consolidate probing on one side. We introduce technologies for solving 40 um fine pitched micro pad probing problems as well as achieving a lower cost of test for a line and space 2/2 um FOPLP.