Practical Application and Analysis of Lead-Free Solder for Hearing Aids
Authors: Youngtak Lee, Doug Link Company: Starkey Hearing Technologies Date Published: 9/17/2017
Abstract: Rapid growth in the consumer electronics industry continues to drive market demand for electronic devices with smaller form factors, lower costs, higher power performance, and increased power efficiency. Over the years several packaging technologies have been developed to meet the market’s needs, including flip chip interconnection and System-in-Package (SiP). The RoHS directive introduced in the early 2000’s restricts the use of lead in all electronics and electronics packaging technologies. However, a surprising amount of surface mount technology (SMT) defects are associated with the use of lead-free solder paste and the methods by which the paste is applied, including solder extrusion and tombstoning. This paper will examine the failure modes of solder extrusion and tombstoning that occurred when two different types of leadfree solders, Sn-Ag-Cu (SAC) and bismuth-silver solder paste were used for passive component attachment within a SiP for hearing aid applications. A design of experiments (DOE) was performed to identify the causes of the lead-free solder defects. The practical application and analysis of lead-free solder in hearing aids will include a comprehensive failure analysis of the SMD components and compare the two different solder types through component and hearing aid system level tests.