Journal of SMT Article


Authors: Matthew Kelly, et al.
Company: IBM Corporation
Date Published: 1/31/2008   Volume: 21-1

Abstract: Since 1999, many OEM firms and their contract manufacturing partners have been converting their product portfolios to comply with EU RoHS regulations. Significant investment has been made within the electronics industry for the development of new lead-free materials and assembly processes suitable for consumer electronics applications. As a result, the majority of the industry’s material, process, and reliability studies to date have focused on low-to-medium complexity products with only moderate field reliability requirements.

Many firms competing in storage array and server markets continue to take advantage of the “lead in solder” exemption permitted by the EU RoHS directive for these product segments. This exemption allows for the continued use of Pb bearing solder alloys in the manufacture of server and storage array products. In addition, the RoHS directive also states that reviews will be conducted at least every four years to assess the continued technical justification for such exemptions. Consistent with this global drive for ever more aggressive environmental stewardship, IBM is therefore actively exploring lead free alternatives for servers and storage array products.

This paper outlines the process used to qualify a lead-free entry level server complexity PCBA card. It highlights both the successes and technical challenges that remain to produce high reliability, high complexity, lead-free PCBAs (printed circuit board assemblies). It describes the end-to-end lead-free process qualification approach used including a summary of materials compatibility, primary attachment and rework assembly processes, in-circuit and functional test performance, time zero quality assessments, thermal fatigue reliability performance, and mechanical fragility issues.

This work serves as a foundation for further material, process and reliability studies that may ultimately enable a range of server products to confidently convert to lead-free card assembly. With the numerous technical and supply chain challenges that remain, continued industry development is required to ensure high quality and high reliability performance for complex PCBAs.

Keywords: server complexity PCBAs, Pb-free, reliability, server exemption, Pb-free assembly qualification.

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