What is the shelf life of tin plating?
The “shelf life” of the solderability of tin plating is affected by two main factors: storage conditions and plating specification. Storage conditions with elevated temperatures and high humidity will cause faster oxidation of the surface of the tin plating. A thin tin deposit will obviously be sacrificed to the elements faster than a thick one. So a heavier deposit will generally enjoy longer shelf life for solderability. Tin plating will form an inter-metallic layer with the base metal. This is desirable for adhesion purposes. Over time, this process continues and reduces the thickness of the pure tin layer from the underside of the deposit. This is especially true of zinc in brass alloys. The use of ASTM-specified under-plating will control this effect.
