Influence of Leg Shape and Solder Joint Metallurgy on Surface Mount Solder Joint Strength,
Abstract
An experimental program was done to determine the effect of surface mount leg shape on the tensile pull strength of the solder joint. The three leg shapes evaluated were the gull wing, modified gull wing (similar to a J), and butt shape. The tensile test was done at two set speeds using two different solder alloys, 60% Sn/40% Pb and 62% Sn/36% Pb/2% Ag. It was shown that the tensile strength depends little on leg shape, but is strongly dependent on the size of the heel fillet which supports the applied load. From these experimental results, the tensile strength is predicted as a function of leg position on and above the pad surface. The metallurgy of the solder joint is discussed in detail. The role of the copper-tin intermetallic is evaluated, identifying the fracture initiation point as near the intermetallic solder interface. In general, samples soldered with the silver bearing solder were stronger. Speculation on the reasons for the increased strength based on microstructure analysis are provided. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 1987
- Accession Number
- ADP005197
Entities
People
- Joseph Hoyt