Breda, The Netherlands – Ineke van Tiggelen-Aarden, Technical Director for Cobar Europe BV, will present a paper, Thixotropy of Solder Paste Impacts Repeatability and Reproducibility of Rheometric Results in Technical Session S25, New Developments in Solder Paste, at APEX 2007 in Los Angeles. The paper is co-authored by Cobar President Eli Westerlaken and Mrs. Van Tiggelen-Aarden. The paper describes the latest advancements in solder paste characterization, a necessary requirement for repeatability, reduced defects, and printing and soldering process stability especially with the new lead-free SAC-based solder pastes.

“SPC data has shown that the solder paste printing process is the primary source of soldering defects in SMT assembly. Consequently, verification of the specified printing properties of solder paste is of paramount importance in the pursuit of higher quality goals and higher overall yields” Westerlaken says. “In recent years, quality management standards such as ISO/TS 16949 have been driving the development of a reproducible rheometric methodology to characterize and quantify these solder paste properties. In the course of this development, we have learned that the thixotropic history of a solder paste has a major impact on the repeatability and reproducibility of its rheometric characterization.”

The paper, he continues, describes the differences between the various rheometric measuring principles such as the spindle, spiral pump and plate/plate method. It also introduces the development and implementation of a sample preparation method to reduce the impact of the thixotropy of a solder paste in conjunction with enhanced plate/plate rheometry.

The technical session is on Wednesday, 2/21/2007, from 1:30 PM - 3:30 PM and is Chaired by Russell Nowland, Lucent Technologies; for more information, or to sign up to attend, visit www.goipcshows.org.