than plain copper tips are now commonly used but
they also fail eventually (usually by cracking of the
plating) and then erode rapidly unless Savbit solder
is used.
It has also been proved that the use of Savbit
alloy can improve the strength and reliability of
soldered joints very considerably. This is because
ordinary tin/lead alloys can erode thin copper wires
(as used for leads of electronic components) and
thin copper films (as used on printed circuit
boards.) This erosion is between 50 and 100 times
slower at normal soldering temperatures when
Savbit alloy is used.
Savbit solder with Ersin 362 flux has special
M.O.D. approval DTD 900/4535. At high soldering
temperatures (above 350°C) Multicore HMP alloy
gives the best strength.
HMP SOLDER
The presence of 1.5% silver substantially improves
strength and wetting power compared to 5/95
Sn/Pb solder.
Applications
Making nearby soldered joints: A useful
application of a high melting point alloy is the
soldering of joints close to each other in such a
way that the first joint is not re-melted while the
later joint, or joints, are being made. The first joint
is made with HMP alloy (296-301°C) and the
further joints are made with successively lower
melting point alloys, for example - 60/40 tin/lead
alloy (183-188°C) and good control of soldering
temperatures.
Service at high temperatures: The maximum
safe service temperature for any solder alloy
subjected to stress is about 40°C below the solidus
melting temperature, HMP alloy can therefore be
relied upon in service up to about 255°C compared
with about 145°C for the common tin/lead alloys.
HMP alloy is consequently particularly suitable for
soldering electric motors, car radiators, high
temperature lamps and other products which are
likely to meet relatively high temperatures during
their working life.
If HMP is used to solder tin/lead coated
components, the resulting soldered joint will be a
new alloy with a lower melting point than HMP
alloy. This will depend on the thickness and
composition of the coating. The coating itself could
therefore be HMP alloy if necessary.
Service at very low temperatures: Tin/Lead
alloys containing more than 20% of tin become
brittle at temperatures below about -70°C. The
HMP alloy containing 5% of tin remains ductile
(non-brittle) down to below -200°C. Multicore HMP
alloy is also recommended therefore for service in
extremely cold conditions.
Creep strength of HMP alloy: From information
supplied, it is clear that an outstanding feature is its
very great improvement in resistance to creep by
comparison with the tin/lead solders, both at
normal and at elevated temperatures. At 150°C for
example, a 50/50 tin/lead solder will fail under a
load of 0.7 N mm-2 in approximately 10 hours. The
following results were obtained with HMP alloy at
the same temperature.
Load (N mm-2) Time to failure
3.4 150 hours
1.7 about 1 year
0.7 no creep
96S TIN/SILVER SOLDER
Multicore 96S alloy is the pure tin/silver eutectic
alloy; like pure tin, it is bright, hardly tarnishes, is
lead-free and non-toxic, but unlike pure tin it is
relatively strong.
It has higher electrical conductivity than other soft
solders and a melting point approximately 40°C
higher than either 60/40, 63/37 or LMP alloys. For
one or more of these reasons it finds uses, despite
its higher cost, in the form of ERSIN Multicore
Solder Wire usually in Electronics applications. The
alloy itself is however used more extensively for
non-electrical applications in the form of Multicore
ARAX Acid-cored Solder, particularly for soldering
stainless steel.
96S has better wetting power on stainless steel
than other solders. Note the silver in 96S does not
suppress absorption of silver from silver plated
surfaces or metallisations into the solder, so 96S is
not suitable for soldering to such surfaces.
Sn62 SOLDERS
Applications
Soldering silver-plated surfaces: The presence
of the 2% silver in Sn62 alloys suppresses
absorption of silver from silver-plated surfaces into
the solder. A good joint is thus obtained. If an
ordinary tin/lead alloy is used on silver-plated
surfaces, the silver can be lifted from the surface
and dissolved into the solder so that a good joint is
unlikely. The attachment of terminations in the
manufacture of silver ceramic capacitors is a
typical application.
95A, 97Cu AND 99C SOLDERS
Applications
Lead-free plumbing solders: 97Cu and 99C are
lead-free (non toxic) plumbing solders with superior
wetting and capillary filling characteristics.
Lead-free high temperature solder: 95A is a high
melting point solder suitable for general purpose
soldering where a lead-free alloy is require