Effect of onion-like carbon on the resistance and adhesion of pogo pins with titanium adhesive layer of varying thicknesses

Abstract

A test probe is a component used to attach microchips to a semiconductor testing device. Pogo pins are one of the several types of probes available on the market. However, probes exhibit some drawbacks, such as high manufacturing costs, low test lifespan, and susceptibility to sticking. In this study, a dual-layer structure that can enhance the wear resistance and anti-sticking properties of gold (Au)-plated pogo pins, as well as overcome surface adhesion issues, is proposed. Oxygen plasma cleaning is first performed for 30 min. Subsequently, a direct current plasma of 250 W is applied to deposit a titanium (Ti) layer to enhance the adhesion of onion-like carbon (OLC) on the surface. The four thicknesses of the deposited Ti metal are 20, 30, 50, and 70 nm. Finally, extremely hard and conductive OLC with a thickness of 110 nm is deposited on the Ti/Au-plated pogo pin surface by physical vapor deposition. Results reveal that most of the area of OLC with the Ti adhesion layer remains on the substrates even after cycle testing at 200 K. Nanoindenter measurements reveal that with an increase in the Ti thickness, the probe hardness increases; in particular, at a thickness of 70 nm, the hardness is 121 % greater than that of the as-grown probe. Furthermore, under the 200 K wear test, the probe with 70 nm Ti exhibits ∼9 % reduction in surface wear in comparison with that of the as-grown probe. Finally, while the resistance of the dual-layer coated probe is greater than that of the as-grown probe at 0 K, its resistance becomes markedly less than that of the as-grown probe after undergoing a 200 K cycle test. On the basis of these results, a mechanism of adhesion, hardness, and wear resistance improvement by the OLC/Ti dual-layer structure is proposed.