Bond strengths to Ni /ENIG will be low with Bi/Sn without due attention to
process (profile and flux type).
I have to say I think I differ from the AWS (trembling).....
Not only a lower activation temperature flux, but likely a "slow" flux too.
At the lower temperatures and diluted tin content involved, joints are
slower to form, so the flux has to release its activity at a lower
temperature and maintain its effectiveness over a longer period.
If a typical Sn/Pb profile is /\ lets say a tent/wigwam. Then a typical
Bi/Sn profile /¯¯\, is a marquee. Some [OA] water washable fluxes have the
low temperature activity, but getting satisfactory results from a resin
material requires a specialist supplier. For ENIG (nickel) this is even more
the case. Ni oxide is hard to remove at these low temps and solubility of Ni
is slow too.
Regards
Mike
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Guy Ramsey
Sent: 27 August 2009 20:57
To: [log in to unmask]
Subject: Re: [TN] Soldering tin-bismuth alloys
Two thoughts from the American Welding Society: Soldering Handbook.
The flux activation temperature is often overlooked vis-à-vis the solder
alloy melting temperature when developing a soldering process. For example,
low melting temperature solders . . . may experience poor solderability when
used with rosin-based fluxes because the process temperatures are actually
below the activation temperature of the flux.
The handbook does not recommend, in general prolonged hold times for a
variety of reasons.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Gumpert, Ben
Sent: Thursday, August 27, 2009 2:34 PM
To: [log in to unmask]
Subject: [TN] Soldering tin-bismuth alloys
Technetters,
Anyone have experience using tin-bismuth solder?
Should the dwell time at TAL+20° in my reflow profile be longer (compared to
a eutectic SnPb profile) because of the lower peak temperature?
How long should it be for soldering to nickel?
Thanks,
Ben
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