Electrical Characterization of Test Sockets With Novel Contactors

Novel spring contactors were designed and characterized for wafer-level interposer and high-speed package test system applications, especially for wafer-level packages. These contactors can be used as replacement for vertical wafer probes as well as test sockets used in the final test. The contactor pin consists of a plunger section made of beryllium copper and a plated helical stainless steel spring wire. It is 5 mm in uncompressed total length, including the plunger and the spring. The overall diameter of the spring wire section was 0.51 mm. The design of the contactor is much simpler and more scalable than that of traditional spring pins called Pogo pins used in package tests. A test socket containing 36 contactor pins was constructed for tests and measurements. The experimental characterization shows -1-dB bandwidth of 3.73 GHz for 0.8-mm pitch, measured by the direct contact method. This experimental result correlates well with the simulated results. The rise time was 82 ps as measured by TDR, and the propagation delay was 23 ps. The electrical conduction path is through the pin and the spring, making it a reliable contact. However, the electrical path is known to be through the barrel, not the spring for the regular spring pins.