Formula Accuracy Print E-mail
User Rating: / 0
Written by Dr. Ron Lasky   
Tuesday, 01 June 2010 09:50

Ken writes:

Dr. Ron, Thanks for your helpful post. I get close (-1.1%) with your formulas for an alloy I am working with. I think the crystal lattice packing factor for some of the individual elements is throwing off the result since it is different than the alloy. I tried to take this into account, but I get an error on the opposite side (+1.6%) of the actual. Any thoughts on if your formula can be made more accurate by taking element and alloy crystal lattice packing factors into account?

The solder alloy calculation assumes that the metals mix with no interaction, much as miscible liquids, of different densities would. There are numerous phenomena that could cause errors. They include:

1. Metals can come from different crystal systems. Lead, silver and copper are face-centered-cubic, whereas tin, the base metal for most solders, is of the tetragonal system.

2. Some metals form intermetallics with tin, such as copper and silver. These intermetallics have different densities than the metals or the resulting alloy.

3. Grain boundaries can leave some (probably small) empty space.

So I think Ken's 1% accuracy is very good. The biggest mistake one can make however, is the most common: assuming that the density is simply given as the sum of the metal mass fractions times the metal densities. To many, it seems logical, but it is wrong. 

My original posting on how to derive the formula for solder alloy density is here


Dr. Ron


Last Updated on Thursday, 08 July 2010 09:41


Eastern-US: China’s New Competitor?

Parity emerges among EMS Factories from Asia, Mexico and the US.

For the first time in years we see parity in the Eastern US among EMS factories from Asia, Mexico and the US. This EMS market condition will permit American OEMs (the EMS industry refers to OEMs as customers) to have more EMS pathways to choose from. Now more than ever, such EMS assignments will require deeper investigation relating to the OEMs’ evaluation of manufacturing strategies.

The Human Touch

For those who count on the electronics industry for big feats, it’s been a remarkable couple of years.



Advances in Concentration Monitoring and Closed-Loop Control

Contaminated bath water skews refractive index results. New technology can accurately measure aqueous cleaning agent concentration.

Circuits Disassembly: Materials Characterization and Failure Analysis

A systematic approach to nonconventional methods of encapsulant removal.





CB Login



English French German Italian Portuguese Russian Spanish


Yincae Rolls Out ACP120 Solderable Coating
ACP 120 series anti-oxidation solderable coatings replace nanofilm gold. Are for anti-corrosion and anti-rusting on solderable surfaces on which solder paste, solder preform or a solder ball can be...