Finalize the FoS test setup and procedure. Determine the threshold relative humidity below which creep corrosion will not occur even in corrosive environments high in sulfur-bearing gases and chlorine.
Electronic hardware can be susceptible to creep corrosion in corrosive environments. Creep corrosion is the corrosion of metallization (generally copper and silver) and the migration of the corrosion product (typically copper and silver sulfides) across the printed circuit board (FR-4 and solder mask) surfaces. In environments high in sulfur-bearing gaseous contamination, the extent of creep corrosion may be so high as to electrically short circuit adjacent pads and traces, causing the circuit boards to malfunction.
To help eliminate creep corrosion, industry has initiated significant effort to better understand its cause and mitigation. iNEMI had an experimental program studying creep corrosion since October 2009. The iNEMI project on creep corrosion testing using mixed-flowing gases (MFG) was successful in identifying the role of finishes and fluxes on creep corrosion. MFG test is complex and expensive. Only a handful amongst the major electronics companies worldwide have MFG test capability. The MFG chamber (iNEMI creep corrosion test condition: H2S = 1200 ppb; NO2 = 200 ppb; Cl2 = 20 ppb; SO2 = 200 ppb; 40?, RH 70-75%) has copper corrosion rates much higher than silver corrosion rates. However, indoors, the copper corrosion rate is much lower than silver corrosion; whereas, outdoors, the opposite is true. There is motivation to explore the use of flowers of sulfur chambers as a means of qualifying PCBs that will survive the harsh, corrosive field environments without suffering creep corrosion.
Significant experiments have been done in Phases 1 and 2 to design the FoS test chamber, and to develop the test procedures to demonstrate creep corrosion and to compare with field failures. The major remaining challenge is to control the humidity level within sulfur-bearing gases and chlorine gas. If we can run the FOS test at much lower humidity, then the FoS test could be used to determine the threshold relative humidity below which creep corrosion will not occur even in corrosive environments high in sulfur-bearing gases and chlorine.
Objectives of Phase 3