Lead Free Rework Process for Chip Scale Packages

Category: No-Lead Soldering
Post Date: July 20, 2004
Author(s): Arun Gowda and K. Srihari, Ph.D., Electronics Manufacturing Research and Services, State University of New York, Binghamton; and Anthony Primavera, Ph.D., Consortium Manager, Universal Instruments Corporation, Binghamton, New York

Description
Legislation against the use of lead in electronics has been the driving force behind the use of lead-free solders, surface finishes, and component lead finishes. The major concern in using lead-free solders in the assembly and rework Chip Scale Packages (CSPs) is the relatively high temperatures that the components and the boards experience. Fine-pitch CSPs have very low standoff heights following assembly making inspection and rework of these components more difficult. One other concern pertinent to rework is the temperature of the neighboring components during rework. These issues, coupled with the limitations of rework equipment to handle lead-free reflow temperatures, make the task of reworking lead-free assemblies more challenging. Useful guidelines for lead-free rework of fine-pitch components and CSPs in particular were developed and are presented in this paper.

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