Emerging Technologies Conference Proceedings

Reduced Oxide Soldering Activation (ROSA): Enabling Technology for Soldering of Flip Chip Assemblies

Author: David Hillman
Company: Rockwell Avionics & Comm.
Date Published: 10/20/1997   Conference: Emerging Technologies

Abstract: According to a survey in the 1995 Best Manufacturing Practices Report, the number one concern of people in the electronics industry is solderability, followed closely by compliance to environmental regulations. Consequently, there is a pressing need for a solderability restoration technology that is both environmentally benign and reliable. For flip chip assemblies, the solderability of the printed wiring board and the presence of flux residue are key issues. Loss in solderability translates into lower process yields, increased rework, and reduced field reliability. It is generally accepted that reworked solder joints are less reliable. For less demanding commercial applications, solderability restoration technology could significantly reduce costs by eliminating consumable fluxes and lowering scrap rates. The availability of such technology also enables solderability problems to be addressed proactively. A team of commercial and military electronics manufacturers (Rockwell Collins Inc. , Northern Telecom, Allen Bradley, CSL Inc., Rockwell Science Center & SEHO USA Inc.) under a DARPA funded program has been investigating the use of an environmentally friendly, closed loop restoration system for use on Flip Chip technologies. The paper will present the DARPA ROSA program flip chip test results utilizing a benchtop application restoration system in three areas: (1) Demonstration of the applicability of the restoration process for Flip chip technology after storage degradation for tin-lead surfaces, (2) Demonstration of the potential for the ROSA restoration process to effectively restore bare and Organic Solderability Preserved (OSP) copper surfaces, (3) Characterization of process residues, solder joint metallurgical quality and environmental process issues. Key Words: Flip Chip, Design of Experiments (DOE), Fluxless Soldering, Electrochemical Reduction

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