HERNDON, VA—The International Electronics Manufacturing Initiative (iNEMI) has released two documents to help manufacturers reduce the risk of tin whiskers in lead-free products.

The first is JEDEC standard JESD22A121, "Test Method for Measuring Whisker Growth on Tin and Tin Alloy Surface Finishes," and the second is the updated "Recommendations on Lead-Free Finishes for Components Used in High-Reliability Products," from the iNEMI Tin Whisker User Group. 

The JEDEC standard provides: an industry-standard method of measuring and comparing whisker propensity for different plating or finish chemistries and processes; a consistent inspection protocol for tin whisker examination; and a standard reporting format.

It identifies three test conditions that appear to be suitable for monitoring tin whisker growth (Two provide for isothermal conditions with controlled humidity and the third is a thermal cycling condition).
 
The standard can be downloaded for free (http://www.jedec.org/download/).
 
The iNEMI Tin Whisker User Group has published revised recommendations for lead-free component finishes to be used in high-reliability products. The publication is intended to help manufacturers minimize the risk of failures from tin whiskers.
 
It is the consensus of the iNEMI User Group that pure tin electroplating presents a risk in high-reliability applications, and that cost-effective alternatives can minimize this risk.  The updated document presents recommendations for lead-free finishes for a variety of applications. The group has defined methods and tests intended to minimize the risk of tin whiskers creating functional or reliability problems in electronic products. Their recommendations include a combination of known mitigation practices, process controls and some level of testing.
 
The revision also reflects the uniform test requirements established in JESD22A121. The team has added tables addressing every finish and base material offered commercially and provides user guidelines for the various combinations. They have also added finish recommendations for separable connectors and for buss bars and heat sinks.
 
The User Group recommendations are available at http://www.nemi.org/projects/ese/tin_whisker_activities.html.

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