SMTA International Conference Proceedings

Can Sintered Silvers Be Used in Surface Mount Applications

Author: C.P. Hunt & L. Crocker
Company: National Physical Laboratory
Date Published: 9/28/2014   Conference: SMTA International

Abstract: The current RoHS recast Directive 2011/65/EU have a number of exceptions, and virtually all these can potential expire and full compliance with the directive will be required in 2016. A significant impact to industry will be the banning of the high melting point high lead solders used in level 1 die attach and power semiconductors. Although there have been high temperature applications, such as down hole drilling, the requirements for operating at higher temperatures are increasing with electric transport and renewable energy.

A number of solutions are being pursued, and one that offers some promise is the use of sintered silvers. Sintering of nano sized powders can be accomplished at 250ºC and less, and potentially can be used for surface mount applications.

This paper reports an investigation into the practicalities of the assembly process, with consideration to the metallurgy of the component and PCB metallisation.

Since the sintering process does not go through a liquid phase a tin termination is in principle is left intact, however data show that the tin can potentially adversely affect the silver layer.

Assemblies have been tested, including some that have been conditioned, with shear, and hot shear testing, with additional testing that explores the creep and relaxation of single lap shear joints by mechanical testing. Characterisation of the interconnect microstructure, and determination of degradation mechanisms are discussed.

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