Tin-Lead Solders
engineering fundamentals Tin-Lead Solders
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Introduction
Tin, lead and their alloys, due to their low melting temperatures and wide availability, are the most commonly used solder materials. In fact, lead has been used as a soldering metal for water pipes (also made of lead) even in Roman times, hence the scientific name for lead, Plumbum.
Mechanical Properties
Tin
(wt.%)
Tensile
Strength

(MPa)
Shear
Strength

(MPa)
Elongation
(%)
Elastic
Modulus

(GPa)
Izod
Impact
Strength

(J)
Stress to
produce
0.01%/day
creep rate

(kPa)
0 12 12 55 18.0 8.1 1700
5 28 14 45 18.5 9.5 1400
10 30 17 30 19.0 10.8  
20 33 20 20 20.0 15.0  
30 34 28 18 21.0 16.3 790
40 37 32 25 23.7 19.0  
50 41 36 35 26.9 20.3 860
60 52 39 40 30.0 20.3  
63 54 37 37 31.5 20.3 2300
70 54 36 30 35.0 19.0  
 

As can be seen from the above table, the 63% tin 37% lead solder alloy results in the maximum tensile strength, shear strength, impact strength, and resistance to creep. This 63-37 composition is also known as the eutectic point of the alloy, where the alloy behaves like a pure metal having a single melting (solidification) temperature (176ºC / 349ºF). This is a good operational feature. Once the solder melts on application of heat, it solidifies immediately on removal of heat, without going through a pasty stage like other alloys. This allows for predictable soldering and fast cycle times.

Physical Properties
Tin
(wt.%)
Specific
Gravigy
Electric
Resistivity

(10-9ohm-m)
Thermal
Conductivity

(W/m-K)
Thermal
Expansion
Coefficient

(10-6/°C)
0 11.34 212 34.8 29.3
5 10.80 207 35.2 28.4
10 10.50 204 35.8 27.9
20 10.40 192 37.4 26.6
30 9.66 180 40.5 25.6
40 9.28 166 43.6 24.7
50 8.90 153 47.8 23.6
60 8.52 145 49.8 21.6
63 8.34 144 40.9 21.4
70 8.17 134 30.0 20.7
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