First question I have for you is: Are you assuming that standard precautions are in place at your facility to minimize moisture content i.e. air- deionizers, vacuum sealed packaging, humidity control in storage and manufacturing?
You do not mention geographic region you are in. Some parts of the world have high humidity, causing bigger concerns. We are also coming into the winter months which will also raise the possibility of humidity in the air. These are seemingly plain, obvious questions - but are commonly overlooked by non-technical types. In other words, did you apply common sense before you asked these questions?
To be specific regarding your question # 1: Baking will create some oxidation, it is a natural occurance. Normally, the amount of oxidation is negligible, barely measurable and is easily corrected by the reaction with flux. Flux in solder is there to clean, etch or prepare the mating surfaces, it dissolves the oxidation. Depending on your environment (high humidity), you may need to consider a more aggressive flux to overcome oxidation. Check with your paste supplier - they should be able to tell you what is normal for your region.
Question #2 - expected Life of Product should give you some indication of solderability expectations. Generally, you should warranty for craftsmanship defects as you cannot control the abuse of your work in the outside world. Can you guarantee that the product will always be safe from humidity or other sources that will accelerate oxidation?
Question #3 - recycled solder paste? Who is doing the recycling? Are you receiving this from a certified supplier? If so, the amount of oxidation present should be near zero, as long as the flux is still active. If you are recycling your own, from old dried out paste, you will probably be doing yourself more harm than good by trying to save a few bucks here. Can you guarantee the right amount of flux to solder spheres? Can you accurately measure your paste viscosity? If you say no to either of these questions, pass on using recycled solder pastes.
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