My engineering task poses a problem with sulfur damaging electronic components. There are enclosed gas volumes which contain sensitive electronic devices as well as NBR sealings and gaskets. The sealings can evaporate sulfur in different compounds, the most dangerous seemingly beeing hydrogen sulfide. I have two options protecting the electronics.

  1. geometric separation by confining the electronics in separate housings. This might be possible but is very difficult due to the geometry of all devices.

  2. removal of evaporating sulfur compounds from the air surrounding the electronics.

I want to evaluate option 2.

My first question is about the getter material in general. I know of only two usable materials: silver and zinc carbonate. Are there other usable (solid) materials?

Silver could be applied as a foil inside the common housing exhibiting a considerable surface to the gases. Zinc carbonate must be applied in a permeable containment like a paper or Tyvek bag, similar to desiccant bags.

I assume, the number of sulfur compounds which can eventually evaporate from some sealings, is rather limited. But the evaporation will probably never cease to happen. Hence the getter must be active for the whole product lifetime. Is there any mechanism that could prevent this? E.g. oxidation of silver or weird reactions of zinc carbonate?

I understand by using a getter, I cannot prevent the effect of the detrimental gasses on the sensible equipment in total, but I can limit concentration and time to extend the period until the destruction of the electronics. I assume, that by exposing a silver foil to the gas mixture with a surface n-times as big as that of the semiconductor, the resorbed sulfur will at least n-times as much as that of the semiconductor? So if I increase the surface of the silver foil the amount of sulfur likely absorbed by the semiconductor will decrease by the same factor, given a constant evaporation rate (ev=const [mol/s]).

I guess this is difficult to formulate for a bag of zinc carbonate, isn't it? Might the surface of the bag correlate the same way?

It seems, after installing sulfur sources and sinks, an equilibrium will establish. Given a constant gas concentration around getters and sensitive equipment, I want to make further considerations. Silver surfaces can bind sulfides directly while the housing of electronics has to be traversed by diffusion. Is it fair to assume that due to the presence of uncovered getters the mass flow by diffusion through the housings is reduced by much a greater degree than just by the proportion of surfaces between getter and electronics? Can I hope that this reduction is one or more orders of magnitude?


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