I don't think you'ld develop any dangerous intermettallics BUT I would
not suggest touching up one alloy with another unless you know (from a
design perspective) why the Sn95Sb5 was used.  As other noted, it may be
due to a need for a higher melting point or some other related physical
property.  In touching up with a lower melting point solder, the new
joint's properties will be SOMEWHERE between Sn63 and Sn95Sb5 and where
would depend on the how much alloy you add and how well it is "mixed
into" the matrix during touchup.

We looked into doing this once and the control of volume/mixing is
tricky.  I suggest you touchup with the original alloy and avoid any
potential issues.

===============================
Jim Maguire
Senior Principal Engineer
Boeing Defense & Space Group
PO Box 3999  M/S 3W-97
Seattle, WA  98124-2499
Phone (206)657-9063     Fax 657-8903
Email:  [log in to unmask]
================================

> ----------
> From:         Sheila Smith[SMTP:[log in to unmask]]
> Reply To:     TechNet Mail Forum.;Sheila Smith
> Sent:         Tuesday, October 21, 1997 7:05 AM
> To:   [log in to unmask]
> Subject:      [TECHNET] ASSY:  Solder compatibility
>
> Hello TechNet ..
>
> Does anyone have any experience with possible intermetallics formation
> if I
> use Sn62Pb362Ag to touchup voids in a Vapor phase reflowed Sn95Sb5
> solder
> joint ???  Especially after 100 temp cycles from -55C to 120C?  Thanks
> for
> any help!
>
> Sheila Smith, Tracor AES
>
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