Some Physical Properties of Wiping Solders

The plasticity of a number of solders at wiping temperatures has been determined by compression tests between parallel plates. The character of the flow is found to be that corresponding to a linear relation between shearing stress and a fractional power of the velocity gradient. This corresponds approximately to a relation between rate of compression (dh/dl) and sample height (//) given by the equation: dh/dt = kh , in which k and b are constants, of which b is independent of the test conditions. For viscous materials b = 5.0; for most solders b is greater than 5.0, and increasing values of b are associated with lower temperature gradients of plasticity. It is shown that a solder must have a low temperature gradient of plasticity in order to be properly wiped, and that determination of the value of b by means of a plasticity test can therefore be used to evaluate the working properties of a solder. A number of factors upon which the plasticity of wiping solders and the porosity of wiped joints may depend have been investigated. In particular, it is shown that segregation is not responsible for porosity, but that the latter may be dependent upon the particle size of the solid phase at wiping temperatures. The relation of particle size to the wetting power of the liquid phase is discussed. b is in joining sections of (or lead alloy) piping sheathing, such as that used for A WIPING solderormustone used sheathing readily, mustleadtelephone cables. As such, it wet the be coherent and plastic enough to be worked with the hands over a considerable temperature range, and must form a strong, non-porous joint.