A flowers of sulfur corrosion chamber for testing electronic hardware

Abstract

A flowers of sulfur (FoS) corrosion test chamber has been developed by the iNEMI taskforce on creep corrosion on printed circuit boards (PCBs). Besides testing for creep corrosion, the FoS chamber has the potential of replacing the mixed-flowing gas (MFG) chamber as an industry-standard, general-purpose corrosion chamber for testing a whole range of electronic components and assemblies. The iNEMI FoS chamber consists of a 300-mm cube acrylic sealable box maintained at a constant 50°C. A large area flowers of sulfur tray is the source of sulfur vapor. Household bleach containing sodium hypochlorite provides the chlorine gas. A saturated salt solution dominates the relative humidity in the chamber at its deliquescence relative humidity. The iNEMI FoS chamber can control the sulfur and chlorine concentrations and the temperature and relative humidity (RH) at the desired values. The chamber reaches steady state in a few hours. The paper will describe the details of the chamber design and operation and its use as a low-cost, convenient and easily maintainable replacement for the MFG chamber for a whole range of testing of electronic hardware. Three examples of the use of the chamber will be provided: (1) Effect of relative RH on creep corrosion; (2) Mapping the corrosion rates of silver as a function of temperature and RH; and (3) Characterization of conformal coatings. Progress on the use of the chamber for qualifying surface-mount miniature resistors will also be presented.