Hi Vlad - If I care about the interface being formed between the solder and
the board pad, I do care about the dissolution rates and their impact on
the IMC formation. I wasn't talking about metal dissolution to the point of
pad destruction, I was talking about the formation of IMC layer itself.
Copper/tin IMC is inherently better than nickel/tin due to crystallographic
details. Does that IMC difference have an impact on solder joint integrity
in many product applications? No, but it doesn't mean I should'nt pay
attention to it and understand it so when it does matter I don't neglect
it. And yep, I keep an eye on Alloy 42/Kovar for the same reason. And I
don't need to do a ton of changes for the reflow profiles because of the
plating but we do stay knowledgeable.

Dave

On Thu, Nov 10, 2016 at 2:29 PM, Vladimir <[log in to unmask]>
wrote:

> ‎Hi Dave,
>
> You know that difference in the dissolution rates of Cu and Ni shouldn't
> even be considered. Following that path, what would one  recommend for
> soldering to alloy 42 :-).
>
> Regards,
>
> Vladimir
>
> Sent from my BlackBerry 10 smartphon!e on the Rogers network.
>   Original Message
> From: David Hillman
> Sent: Thursday, November 10, 2016 14:50
> To: [log in to unmask]
> Reply To: TechNet E-Mail Forum
> Subject: Re: [TN] Reflow Profile using HASL or ENIG
>
> Hi folks - lots of good comments, just one more to add: copper diffuses
> faster than nickel so some folks increase their reflow temperatures 5-10C
> and/or slow down the belt speed 3-6 inches per minute. It isn't necessary
> to do this but it does have some good metallurgical basis. Werner
> Englemaier used to advocate doing this when a board finish involved nickel
> (Werner and I discussed this at length, very fun conversations). I set my
> reflow profile based on the board thermal characteristics and the solder
> paste material but being aware of the plating metallurgy impacts (such as
> the gold embrittlement Wayne detailed) is always a good idea.
>
> Dave Hillman
> Rockwell Collins
> [log in to unmask]
>
> On Thu, Nov 10, 2016 at 1:33 PM, Jose A Rios <[log in to unmask]> wrote:
>
> > The reflow profile is typically not a function of the final finish of the
> > pwb. If it is thats news to me.
> >
> > José (Joey) Ríos, Sr QA Engineer
> > Mission Assurance
> > Kavli Institute for Astrophysics & Space Research
> > Massachusetts Institute of Technology
> > [log in to unmask] <mailto:[log in to unmask]>
> > (617)324-6272
> >
> >
> >
> > > On Nov 10, 2016, at 2:17 PM, Wayne Thayer - EXT <
> [log in to unmask]>
> > wrote:
> > >
> > > Those two finishes are fairly similar from a wettability perspective,
> > assuming the ENIG is done properly and that no contamination or
> significant
> > oxidation occurs.
> > >
> > > If you are putting down some high-Au parts, such as leadless ceramic
> > packages, then the reduction in solder volume will make joint
> > embrittlement/stalled flow (due to AuSn being formed) more likely, so you
> > may want to adjust stencil apertures if you have those parts.
> > >
> > > But profile should probably be good. Might be able to reduce time above
> > liquidus slightly to reflect the fact that with ENIG there is no oxide to
> > strip.
> > >
> > > Wayne
> > >
> > > -----Original Message-----
> > > From: TechNet [mailto:[log in to unmask]] On Behalf Of Blair Hogg
> > > Sent: Thursday, November 10, 2016 11:01 AM
> > > To: [log in to unmask]
> > > Subject: [TN] Reflow Profile using HASL or ENIG
> > >
> > > Hi Technetters,
> > >
> > > Would a reflow profile need to change based upon the finish of the
> > board? If we switch from HASL to ENIG would we need to change any
> > parameters? (I know, probably too broad of a question)
> > >
> > > Thanks!
> > >
> > > Blair
> >
>