Hi Dave,

Everyone should know what he or she is soldering to. What I meant is that if one uses same re-flow profile for ISn‎ (or OSP; IAg) and ENIG instead of raising temperature/time above liquidus for ENIG, then a difference in the intermetalli thickness on ENIG boards for both scenarios would be minuscules with absolutely no impact on relaiability.

Cheers,

Vladimir. 

Sent from my BlackBerry 10 smartphone on the Rogers network.
  Original Message  
From: David Hillman
Sent: Thursday, November 10, 2016 15:57
To: TechNet E-Mail Forum; Vladimir Igoshev
Subject: Re: [TN] Reflow Profile using HASL or ENIG

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
>