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 Gravity 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

Solder comes in many forms based upon the end use. Bar solder is extruded and shipped for use with solder bath or solder pot use or even Hot Air Solder Leveling or HASL machines. Solder Paste is used in screening applications for reflow oven soldering, Solder 'wire' is used for hand soldering with a soldering iron or pencil, by electronics hobbyists and assemblers and for rework. Aids to soldering like water soluble soldering flux, rosin core solders, different size soldering irons for different soldering jobs, cleaners, no-clean fluxes, solder wick for hand touch up or removal of solder, solder suckers, Also lead -free solders for compliance with the European RoHS directive due to be enforced after June 2006.

Much can be found on-line on the subject.

http://www.solderchemistry.com/en/solder.html

http://www.solderchemistry.com/en/lead_free.html

 

Solder Types

Many metals and their alloys can be used as solders. The following table gives a quick overview of various solder materials and their applications:   Solder Applications Characteristics Bismuth Low temperature soldering Deforms easily. Needs Aggressive fluxes. Cadmium-Silver High temperature applications Toxic. Good tensile strength Cadmium-Zinc Soldering aluminum Toxic Indium Low temperature soldering, wets glass Deforms easily Lead-Silver High temperature applications Good high temperature properties, good fatigue strength. Medium or low flow properties Tin-Antimony High temperature and food industry applications Non-toxic. Good high temperature properties. Better electrical conductivity and strength than tin-lead solders. Good wetting. Tin-Antimony-Lead General purpose. Improved mechanical properties over Tin-Lead solders. Can not be used with zinc due to brittle zinc-antimony inter-metallic compounds Tin-Lead General purpose, and the most widely used solders. Good process characteristics and the best understood solders. Tin-Silver Used for soldering medical or high precision instruments. High temperature applications Non-toxic but expensive. Good high temperature properties. Tin-Zinc Soldering aluminum   Zinc-Aluminum Soldering aluminum