Hello davide, the biggest advantage you'll find with a complete N2 tunnel is the minimization of oxidation during board preheating. Using only an inerted solder pot allows the oxidation to build up throughout the preheat stages and introduces contaminants during wave soldering. N2 tunnel setup would very likely reduce dross buildup in the pot and decrease maintenance frequency. Let me know if you require additional assistance. Thanks!
Hello Kris, No, it's not necessary to have a nitrogen tunnel setup. A nitrogen tunnel allows a process to go the extra step in providing higher quality through less defects. I can't really speculate on it's use in contract manufacturers mainly because it's an advancement in wave technology and don't know how many CM's have justified it as a means of reducing defects and improving their process.