What is the relative humidity inside my package?
The relative humidity of air is the percentage of moisture contained in the air relative to the fully saturated state of the air and is a function of both pressure and temperature. For a finite volume (such as a semiconductor package) we can look up the low temperature, saturated steam tables in the Handbook of Physics and Chemistry and determine the vapor pressure of water at a given temperature. However, finding information on the equilibrium characteristics of the environment may prove difficult. It is possible, for example, to have a closed environment maintain 100% RH over a wide temperature and pressure range and yet never have a liquid condensate present. The materials used in modern semiconductor devices can include epoxies, polyamides, desiccants, adhesives, and other materials which can take up or release water and maintain equilibrium with the closed environment over a broad range of pressures and temperatures. The concept of relative humidity is difficult to apply to a clos
