[Lead-Free Transition] | [Lead-Free Repair]
With the advent of RoHS (Restriction on Hazardous Substances) and other similar legislation around the world that bans the use of lead in electronic products sold into certain markets, there has been a great emphasis placed on the development and qualification of lead-free solder. Whether an organization's products are exempt or non-exempt from RoHS they are being forced to transition their products to lead-free as tin-lead solder finish electronic parts become unavailable.
The work summarized here focuses on determining the economic consequences of transitioning to and supporting systems with lead-free solder.
There are significant cost and risk implications associated with making the transition to lead-free. The path taken by an organization to deal with lead-free parts and the unavailability of conventional tin-lead parts will have long-term financial ramifications for the organization, and the degree to which industry coordinates the requirements passed to their supply chains will financially impact everyone. This research describes a cost model developed in collaboration with the Lead-free Electronics in Aerospace Project (LEAP) Working Group to assess the ramifications of the lead-free transition. Organizations will be presented with many options on how to adapt to the new lead-free situation. In this research, three basic scenarios are considered: 1) an all lead-free assembly process using lead-free parts as soon as they are available (tin-lead parts are reprocessed into lead-free parts when required); 2) an all tin-lead process (re-process lead-free parts when necessary into tin-lead parts and use them in conventional assembly processes); and 3) a qualified mixed assembly of tin-lead and lead-free parts assembled with tin-lead solder. In order to aide organizations in choosing the approach to take, the model predicts the cumulative costs for each of these options over a 10 year period by taking into account all costs involved in sustaining each of the options.
P. Sandborn and R. Jafreen, "Cost
of Accommodating the Transition to Lead-Free Electronics," Proceedings
of the 2007 Aging Aircraft Conference, Palm Springs, CA, April 2007.
The conversion from tin-lead
to lead-free electronics has created concern amongst engineers about the
reliability of electronic assemblies and the ramifications that reliability
changes may have on the life cycle cost and availability of critical systems
that use lead-free electronics. In order to analyze the
impact of the tin-lead to lead-free electronics conversion in terms of life
cycle cost and availability, a simulation of fielded electronic systems to and
through a board-level repair facility was created.
Systems manufactured with tin-lead parts or lead-free parts that are
fielded, fail and have to be repaired are modeled.
The model includes the effects of finite repair process capacity, repair
prioritization, multiple possible failure mechanisms, no-fault-founds, and
un-repairable units. The model is
used to quantify and demonstrate the system- and enterprise- level risks posed
by the conversion from tin-lead to lead-free.
Example analyses were performed on electronic assemblies that use SAC
(tin, silver and copper) and tin-lead solder using a repair process modeled
after a NSWC Crane Aviation Repair Process (8000 assemblies with 30 year support
lives were modeled). The components
considered consisted of BGA, CSP and TSOP packaged parts that experienced three
different thermal cycling profiles. The
case studies revealed that when exposed to usage profiles characteristic of
consumer electronics, low maximum and mean thermal cycling temperatures with
long dwell times, SAC exhibited significantly reduced repair costs compared to
tin-lead. For usage profiles
characteristic of aerospace and high performance applications, high maximum and
mean thermal cycling temperatures with short dwell times, SAC exhibited
significantly increased repair costs when compared to tin-lead.
A.
Chaloupka and P. Sandborn, “The
Ramifications of Lead-Free Solder on the Electronic Assembly Repair Process,”
accepted for publication IEEE Transactions on Electronic Packaging
Manufacturing.
Lead-Free Repair
Peter Sandborn
University of Maryland
Last Updated: January 13, 2011
Emails:
sandborn@umd.edu
Home Page:
http://www.enme.umd.edu/ESCML