Corrosion inhibition encapsulants

This can be combatted by compounding corrosion inhibiting chemicals in the encapsulating resin. 

Ferrous corrosion products do not have a biocidal effect however, iron corrosion tends to form a much more extensive and encapsulating matrix. This corrosion matrix, which is principally formed of iron oxides, hydroxides, and soil minerals, will encapsulate any organic materials. This usually takes the form of a negative cast (Keepax 1975), provided that the primary layer of corrosion product has been laid down prior to any extensive degradation of the organic material, then fine surface detail will be preserved in the corrosion cast. Because the iron corrosion will not inhibit degradation... 

It appeared to us that if we could add aluminium corrosion inhibitors to the encapsulating resin it was possible that diffusing moisture would transport the inhibitor to the chip surface so that the aluminium conductors would experience an inhibited electrolyte rather than an agressive electrolyte and corrosion would thereby be reduced. It should be noted that this mechanism does not operate in the absence of diffusing moisture but that it is not needed in those circumstances because corrosion would not normally occur. For this approach to be successful the following conditions must be met ... 

Parts that are totally and continuously immersed in oil or grease (preferably inhibited), and those embedded in encapsulate or moisture-proof compound, need not necessarily be given any further protection. Local apphcation of oU or grease, however, does not automatically provide good corrosion protection. 

---