Masters Theses


"Recent legislation and growing environmental concerns have forced the electronics industry to discontinue the use of tin-lead (SnPb) solder. Although the legislation did not directly affect aerospace and defense industries, future transitions to lead-free (LF) solders are inevitable. Differences exist between these high reliability systems and consumer electronics, first of which is a very small production rate and a long life cycle which often leads to repair or rework procedures which introduce the potential for mixing of SnPb and LF solder. In this study, Sn-3Ag-0.5Cu (SAC305) was mixed with Sn-37Pb solder in amounts of 0, 25, 50, 75, and 100 wt. % SAC305 balance SnPb. The melting characteristics and microstructures were examined before and after isothermal aging at 150°C for 500 hours. It was concluded that the onset of melting of the mixed systems was at 178°C while the liquid's temperature increased with an increase in SAC305 content. Aging did not affect the melting point, but did coarsen secondary phase particles in the microstructure. Another important aspect in the aerospace industry is the reliability of components under harsh vibration conditions. Also presented in this study are results and analysis on the effect of random vibration testing on different sizes of LF ball grid array (BGA) packages assembled with two different surface finishes. The surface finishes utilized were electroless nickel immersion gold (ENIG) and SnPb hot-air solder leveling (HASL). Results indicated that the HASL surface finish performed better than the ENIG finish and rework had little effect on the reliability. The smallest component tested produced very inconsistent results, often times being the first to fail, while all other components had similar performance. Crack propagation through large voids, which were common, was the most common failure"--Abstract, page iv.


OKeefe, Matt

Committee Member(s)

Miller, F. Scott
Kohser, Ronald A.


Materials Science and Engineering

Degree Name

M.S. in Metallurgical Engineering


Air Force Research Laboratory (Wright-Patterson Air Force Base, Ohio)


Missouri University of Science and Technology

Publication Date


Journal article titles appearing in thesis/dissertation

  • Effect of aging on the melting characteristics and microstructures of mixed SnPb + Pb-free solders.
  • Effect of surface finish and rework on the reliability of lead-free solder joints in ball grid array packages during random vibration testing


x, 56 pages

Note about bibliography

Includes bibliographical references.


© 2008 Brandon Lee Brinkmeyer, All rights reserved.

Document Type

Thesis - Open Access

File Type




Subject Headings

Solder and soldering -- Materials
Thermal analysis
Lead-free electronics manufacturing processes
Ball grid array technology

Thesis Number

T 10188

Print OCLC #


Electronic OCLC #


Included in

Metallurgy Commons