The Customer: The CSR and Motorola, Inc., under a Cooperative
Research and Development Agreement (CRADA), evaluated the reliability of printed wiring boards (PWBs) manufactured with low-residue soldering technology in a wave soldering application. Low-residue soldering
eliminates the use of chemical solvents used for post-solder cleaning by eliminating the need for cleaning altogether. This project proved that the reliability of PWBs produced with the low-residue process was at least
as good as that of PWBs soldered with the traditional rosin flux/solvent cleaning process. The project gained wide national attention and resulted in Sandia receiving more than 350 inquiries about implementing
low-residue soldering. These inquiries indicated that gaining military acceptance of low-residue technology was a major concern. To address this concern, the CSR formed the Low-Residue Soldering Task Force (LRSTF)
consisting of 11 organizations, including the tri-services and the Department of Energy (DOE), to conduct an extensive evaluation of low-residue soldering technology for military electronics applications. These
organizations were:
Industry Partners
Texas Instruments (CRADA)
Hughes Electronics (CRADA)
Alliant Techsystems (CRADA)
Military Organizations:
NAWC - China Lake
NAWC - Indianapolis
US Army MICOM
USAF Materiel Command
EMPF - Indianapolis
DOE/DP:
DOE/DP TTI HQ
AlliedSignal (DOE facility)
The Work: The LRSTF solicited input from a wider set of
electronics manufacturers and military electronics customers to determine key customer requirements and to develop a test program to thoroughly evaluate low-residue soldering. The test program included the design
and manufacture of a multifaceted test PWB as well as the use of IPC B-24 coupons for surface insulation resistance (SIR) testing and Y-pattern coupons for conformal coat adhesion testing. Four major sections of
circuitry are contained on the test board: high current, high voltage, high speed digital, and high frequency. Each section had plated through hole and surface mount components forming separate functional
circuits. Along with the standard rosin flux/solvent cleaning processed control boards, a wide spectrum of low-residue soldering processes, materials, reliability tests, and responses was incorporated into
experimental designs to evaluate and compare the reliability of low-residue soldering technology. General linear models were used to analyze the large volume of data to determine any significant site, solder
process, conformal coating, substrate, cleaning, and component effects on hardware reliability.
Key Benefits:
Low-residue soldering eliminates the use of chemical solvents, specifically chlorofluorocarbons (CFCs) and also speeds up production by eliminating the
cleaning operation, significantly minimizing waste streams, and significantly reducing costs.
The highly cooperative effort accomplished far more than any one company could have accomplished alone.
The CSR within Sandia served as an independent evaluator of the process reliability.
Results:
Performance of the low-residue soldered boards was comparable to the rosin flux/solvent cleaned control boards in all tests.
Texas Instruments used the test program and results to gain military acceptance of the low-residue process on 66 major military contracts, fully converting to low-residue soldering, which has reduced their annual
cost of materials used in processing by 96%.
Low-residue soldering is now a standard industrial and military electronics manufacturing process, with an estimated 80% of electronics manufacturers using low residue processes.
The project won a U.S. Environmental Protection Agency Stratospheric Ozone Protection Award and the Sandia President's Gold Quality Award.
Reports on both the project with Motorola and the LRSTF evaluation are available from the CSR.
The LRSTF Test Board |
