Hany: In response to your questions:
1- In a double wave solder M/C, is possible to completely eliminate the second wave without affecting the quality of the solder joints?
Many w/s machines have a turbulent wave and a smooth wave. The turbulent wave is closer to the fluxer. The smooth wave is closer to the exit conveyor. � Narrow turbulent wave wets all connections. � Wide smooth wave forms fillets and removes excess solder. Generally, people use their turbulent wave on second side SMT boards only. They use the smooth wave on all boards.
Bottom line: If you get good solder connections running only one wave, DO IT!!! If nothing else, it�ll reduce the amount of solder you ship to your recycler with your dross. Nothing says you have to run both of your waves. What you have to do is produce good solder connections. I know some shops that run both waves all the time, but then again there�s a lot of maroons out there that never come-off their high beams at night.
2-From a quality control perspective, what is the minimum accepted length of DIP component leads on the solder side after wave soldering?
Whatever it says in IPC-A-610, do it!!! As minimum, you have to able to see the shape of the lead protruding through the surface of the solder fillet, regardless of the type of component leads, regardless if it is being wave soldered or any other kind soldering.
3-Is there any technical reference or quality standards for the PCB assemblies curvature after wave soldering?
Check IPC-A-600 for flatness requirements.