Solder composition

DETAILED DESCRIPTION OF THE INVENTION The present invention comprises lead-free solder formulations with melting and flow characteristics similar to the 50/50 tin-lead solders but without the toxic element, lead.
The composition is not listed in current federal, military or commercial solder specifications.
There are no phase diagrams readily available from which to determine new alloy compositions.
This problem was compounded by the vast number of mathematical combinations involving various elements and percentages.
Tin-antimony solder compositions have relatively high liquidus temperatures.
The addition of 0.
1-3% silver to tin/antimony does lower the liquidus temperature below that of the tin/antimony solder.
In order to approach the performance of the 50/50 solder, however, it would be desirable to provide an even lower and wider melting range.
We have found that the addition of a small amount of zinc to this blend accomplishes this purpose.
Zinc is not generally present in solders with the exception of a zinc-aluminum alloy which melts at 720.
degree.
F.
which is unsuitable for low temperature copper soldering and a tin-zinc alloy which melts at 390.
degree.
F.
and is difficult to apply.
Because of their unmanageable characteristics, zinc-aluminum and tin-zinc alloys have been used almost exclusively on aluminum joints.
Replacing lead with selected amounts of zinc, silver and antimony in a tin base is a new approach.
The addition of copper to this composition results in bridging characteristics which approximate those of 50/50 tin-lead solders.
The solder composition found to exhibit the desired melting range and wetting and flow properties is comprised by weight as follows:
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Antimony (Sb) 0.
5%-4.
0%
Zinc (Zn) 0.
5%-4.
0%
Silver (Ag) 0.
1%-3.
0%
Copper (Cu) 0.
1%-2.
0%
Tin (Sn) Remainder
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EXAMPLE A Example A was prepared, by weight, as follows:
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Antimony (Sb) 4