As I continue to assemble my SMT tools, supplies and processes, I was looking at acquiring some solder paste. Unfortunately, there are several kinds of solder paste? What are the pros and cons? Should I consider water soluble paste? Does the tin vs lead vs copper mixture have a significant impact on my selection?It looks like shelf-life is limited, should that be a factor in my selection?Any input on this matter would be greatly appreciated.Thanks.FP