One of my customer asking me about my capability on soldering nickel strip onto the PCB pad. Given the size of the pad of 80 mil X 80 mil, and he want to ensure that we can pass 4.5kg peel force(solder wire Sn63/Pb37). Anybody with this experience ?
Your customer's question is reasonable. Soldering to nickel is not always a walk on the beach [can of corn, or whatever]. This issue is flux not solder. Your Sn63 will have plenty of strength, providing the solder connection is well formed. You should expect the pad to come off the board before solder failure.
Nickel forms a fairly tenacious oxide. Gold is plated over nickel in ENIG solderability protection to prevent nickel oxidation.
So, you need to select and qualify: * A flux that can remove this oxide and then allow soldering to the nickel. * A cleaning process to remove the residues from this flux. [It will not be one of those limp wristed low-res fluxes. Trust me.]
The first place to start is your solder flux supplier.