Electroless nickel plating solderability issues

A. The most aggressive flux you can find is the best. I believe it is called an RMA flux, I am not totally sure. There are also things that can be done after electroless nickel plating to greatly enhance solderability.

A. In general, low phos and especially electroless nickel borons are considerably solderable. Todd's 'RMA' flux refers to Rosin - Mildly Activated and is typically the most aggressive permitted in electronic applications. Type 'RA' fluxes are the most aggressive but are too acidic for use in electronics. Weaker Type R's, straight rosin, won't cut it with any electroless nickel. Mid and high phos EN's are far worse for solderability.

A. Bob,

EN can be difficult to solder to and I suspect you are limited as to the flux you can use. As the EN ages soldering becomes more difficult. A nickel overcoat may be helpful but may have some of the same solderability issues as EN to a lesser degree. I would suggest tin plating over fresh EN, but with all the issues with tin whiskers a tin/lead may be the toxic answer (97% Sn,3% Pb) or better a tin/bismuth bath. Hope you get more feedback on this, as my mind's database on this stuff is close to the recycle bin.

Second thought, if larger PCB is harder to solder than smaller PCB. Are you using the same soldering tool? I large PCB may "drawup" more heat than a smaller one. Try a non-contact infra-red temp senor, RAYTEC makes a great "MiniTemp" $75.00 Do you see cold solder joints on large PCB? Can you use a stronger flux?
R=Rosin
RMA= Rosin Mildly Activated
RA= Rosin activated, also slang is Rosin Acid

Stronger fluxes can have a negative impact on component needs; follow specifications.

Jon,

Thanks for your suggestions. We currently are using an RMA flux, but soon we will have to switch over to a "no clean" solder system. Doing so will make the soldering even more difficult. We do this process on a hot plate and make sure everything is up to temperature before we start the soldering process.

A. From our own experience, using a high phosphorous content electroless nickel solution achieves good solderability. (High P EN).

! ! I don't have personal experience in soldering electroless nickel, but Poobalan's statement is directly contradicted in letter 34791 and several other threads with repeated assertions that mid phos is generally easier to solder than high phos, low phos is generally easier than that, and electroless nickel boron is the best choice when solderability is the major concern.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
January 30, 2013

A. Nickel oxidizes with age. Fresh EN should solder well, while stuff that has been on the shelf for a year probably will not.

A. The avoidance of problems soldering EN is generally in getting the correct flux for the EN alloy you are working with (presuming you have a viable EN plate to work with).

A. I realise an extra process adds to the cost but immersion gold gives superb solderability for many weeks. You can use it to avoid flux. You can be selective about where the solder goes by selectively masking the gold to be preserved and immersing in gold stripper for a few seconds.

A. Hi. I could be in error, but I don't think you are supposed to apply a rust preventative to electroless nickel if you intend to solder it. Immersion gold (ENIG) sounds like a much better idea. Good luck.

Regards,