Wear Resistance Characteristics Under Repeated Touchdown Tests of Pogo-Pin Plungers for Semiconductor Package Inspection

The wear resistance characteristics of pogo-pin plungers with different tip geometries were investigated through repeated touchdown tests. Five types of geometries were evaluated: three crown types (60°, 70°, and 90°), a round type, and a cone type. Touch down tests were conducted at an overdrive of 200 μm, 3 Hz, for 100,000 cycles. Contact resistance and contact force were measured in real time, and wear behavior of top plunger of the pogo-pins was analyzed through microstructural and surface observations. Crown-type plunger exhibited superior initial contact characteristics, but showed significant resistance increases after repeated tests, particularly the 70° crown type. In contrast, the round type maintained the most stable contact resistance. Contact force remained nearly unchanged, indicating that resistance variation was mainly caused by wear. Microstructural analysis revealed severe wear in crown types, while round and cone types showed relatively mild wear. Although crown types effectively removed oxide layers, increased wear and non-uniform contact led to degraded contact stability. These results indicate that round-type plungers provide more stable and reliable performance under repeated contact conditions.