Solder Assessment Study
POC: Matt Rothgeb, NASA TEERM Principal Center (321-867-8476)
matthew.j.rothgeb@nasa.gov
Background
Soldered assemblies
pervade many forms of electronic platforms used by the NASA. Any change in
soldering technology therefore would have major implications for aerospace
operations. Such a challenge is now facing NASA in the push towards lead-free
solder fuelled by impending legislative restrictions on the use of lead and
increasingly, by commercial and marketing activities overseas.
While lead free
solders are purported to reduce their environmental and health risks, these new
solders present certain technical risks. First, the reliability of most
lead-free solders is not known for high-reliability applications. Electroplated
tin is more prone to the phenomena of whiskering, which can lead to electrical
shorting. Lead free solders also require different processing conditions, such
as higher melting temperatures.
Whatever the
driver, it is probable that lead-free soldering will become the norm for
commercial applications before 2006-2007, and will shortly thereafter push for a
similar switch to lead-free solder for high-reliability electronics (as is seen
in most NASA applications), which commands less than 1% of the total electronics
market and therefore has little say over the direction of the overall industry.
Because of these pending changes and short timeframe, an assessment was
conducted considering the current usage of solder across NASA's Centers in order
to determine the nature and magnitude of the risk to NASA today and should the
electronics industry follow through with a complete changeover to lead-free
solder.
In 2002 and 2003, a
study was performed by NASA TEERM (formerly AP2) to determine the types and
severity of risk relating to electronics manufacturing with lead-free solders to
NASA programs both present and future. Because of recent legislation overseas
and the electronics manufacturing industries recent interest in converting to
lead-free electronics systems as opposed to currently manufactured lead based
systems, a risk to high-reliability electronics such as aerospace equipment has
become evident. Several site visits were performed within NASA Center shops that
used the highest volume of lead based solders in previous years. If site visits
could not be arranged, telephone interviews were performed with shop owners and
personnel within the five NASA Centers that were assessed.
Objective
Kennedy Space
Center, Johnson Space Center, Jet Propulsion Laboratories, Goddard Space Flight
Center and Marshall Space Flight Center were assessed for solder usage,
procurement, quality assurance, quality control and programs each supported.
Risk was assessed on two levels, quantitative and qualitative. Quantitative risk
was determined by calculating the number of solder joints accomplished annually
at the Centers assessed and estimating the total number of joints that NASA
accomplishes annually. Through this estimation, it was determined that NASA
accomplished between 8 and 12 million solder joints in 2002. Qualitatively, each
Center’s programs were reviewed for the risk of intrusion of lead-free systems
into their process lines and/or the risk to NASA of obsolescence should the
electronics industry shift to lead-free systems in the near future.
Conclusions
NASA's highest risk
exists in future programs should the industry convert to completely lead-free
systems. Currently, there are not enough resources within NASA to support the
construction of a next generation reusable launch vehicles or to maintain those
systems without the involvement of outside electronics manufacturers. Should the
electronics industry discontinue support of conventional lead solders and an
alternative to conventional lead-based systems is not qualified for aerospace
(manned and non-manned systems), all of NASA's high-reliability systems
currently under construction and all future systems will be compromised.
Engineers involved
with construction of existing aerospace systems and the planning of future space
transport systems need to be involved in the research, demonstration and
validation of lead-free solders and electronics components. Mission preparedness
and success depend upon this if foreign and domestic electronics manufacturers
continue to aim toward the goal of conversion to lead-free systems as the norm
of the industry.
Achievements
- Assessments performed at 5 NASA Centers.
- On-Site visits were performed at 3 of the 5 NASA Centers.
- Over 14 shops were reviewed during study.
- Completed final report in April 2003
Next Steps
- The completion of this project helped
solidify the importance of NASA being an active participant in the “Lead Free
Solder Testing for High-Reliability” and the “Lead Free Solder Body of
Knowledge” Projects.
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