Keep in mind that not every PCB contains all the layers listed â the need for different layer types depends on the specifics of your design. Single layer boards typically include: a mechanical layer, a keep out layer, a routing layer, an overlay layer, a solder mask layer and a solder paste layer.
An austenitic (300 series) stainless steel will outlast both aluminum and steel exposed to rain or salt spray. Steel without a protective coating will do poorly in both environments but if properly plated or painted, may last a long time. The aluminum alloys likely to be found in many consumer products may develop âlawn chair diseaseâ exposed to at least urban rain and condensation but possibly also in cleaner environments as well (up to you to test).
The surface of aluminum metal is covered with a thin layer of oxide that helps protect the metal from attack by air. So, normally, aluminum metal does not react with air. If the oxide layer is damaged, the aluminum metal is exposed to attack. Aluminum will burn in oxygen with a brilliant white flame to form the trioxide aluminum(III) oxide, Al2O3. Aluminum metal is obtained from the pure hot molten Al2O3 by an electrolytic method.