SMTA International Conference Proceedings


Authors: George J.S. Chou, Ph.D. and Robert D. Hilty, Ph.D.
Company: Tyco Electronics Corporation
Date Published: 9/25/2005   Conference: SMTA International

Abstract: Although compliant pin (or press-fit) connector systems may be exempted from the WEEE and RoHS directives, OEM’s are still continuing their demands for the lead-free products. The current study has conducted statistical analyses on the multi-level full factorial DOEs from new data and a previous investigation on lead-free compliant pin connections. The DOE data were from the mechanical characterization of the lead-free connection using eye-ofthe-needle (EON) compliant pin.

The DOEs include the variables: PTH finish (HASL, galvanic Au, OSP, immersion Sn, immersion Au, and immersion Ag), PTH size, compliant pin finish (bright tin-lead, bright tin, matte tin, and gold) over nickel, pin stock thickness, and installation/repair. The effects from these variables and their interactions have been analyzed to assess the impact to the lead-free EON compliant pin connections. The PTHs with inserted pins were also cross-sectioned and evaluated to assess the deformation and distortion by the compliant pins. Another key issue with press-fit connector systems is concern about the formation of tin whiskers.

Since complaint pin products employ significant compressive stress to the tin plating, tin whisker growth can be accelerated. The results summarized here include the tin whisker testing as per the iNEMI tin whisker test methods on matte tin over nickel, bright tin over nickel as well as bright tin-lead over nickel as applied to compliant pin connector systems.

Key words: lead-free, compliant pin, press-fit, connector, tin whisker.

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