Time, time, time. There just never seems to be enough!!! Eh?
You�re correct. Depending on the material, some trays can take a high temperature bake, while other trays, in addition to tubes, and reels, require a low temperature bake. With this later group of carriers, long storage times at elevated temperatures can cause deformation of packaging, reduced solderability of components, and deterioration of the antistatic properties of the shipping carriers. The 40�C value you see quoted for low temperature baking is derived from properties of the material used to fabricate these carriers.
Get a copy of J-STD-033 [http://www.jedec.org/download]. It talks to bake times based on component thickness.
Consider these alternatives:
1 Use burn-in carriers.
2 Talk to your carrier supplier to determine the temperature their material can take. [The 40�C value maybe for wimps.] Bake at that temperature. To determine the temperature / time relationship: * Moisture permeability of materials is usually plotted linearly on log/log paper. * Weigh some dry components and compare that to some wet components.
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