Process atmosphere reactions cooling rates, effect

In addition to the metallurgical aspects discussed above, process parameters can have important effects on reliability as well. Good-quality paste printing, peak reflow temperature, dwell time above the liquidus temperature, cooling rate, and solder atmosphere reactions all affect the microstructure of solder joints and ultimately their reliability. Higher processing temperatures increase the dissolution rates of metal finishes and/or conductor metals (i.e., minor elements) into the solder and can increase the rate of intermetallic compound formation in the bulk solder. This increases the joint stiffness (i.e., reduces the compliance). 

---