TEDDINGTON, UK – The higher the concentration of silver in a lead-free alloy, the better the performance at high frequencies.
 
That’s one finding of a just-released National Physical Laboratory report on vibration in lead-free alloys. 
 
The NPL this week released a report on its high frequency testing of lead-free solder alloys, using a reproducible model solder joint as the sample, to which well-controlled vibration was applied.
 
The frequencies tested were 400 and 800 Hz, corresponding to acceleration in the range of 10 to 20 g. The study highlighted the different behavior of various alloys when subjected to vibration, in particular the superiority of the SnPb alloy, especially at higher frequencies. This method was shown to be useful in characterizing and ranking various materials, says NPL. Tests could be repeated with a range of conditions, targeted at specific industrial applications.
 
The method is versatile, and the equipment could easily be modified for testing at high temperatures, says NPL.
 
This work has been aimed at studying lead-free solder alloys in an environment above 100 Hz, using SnPb alloy as a benchmark. Many previous studies on high-cycle fatigue have been focused on studying the effects on a full PCB. That assessment method, however, is not suitable for characterizing solder performance, as the approach is geometry and condition-specific.
 
The lifetime of the joint was recorded, as well as the material properties’ response to the vibration. For a copy of this report, please contact Ling Zou at ling.zou@npl.co.uk.