Recent Advances in Mitigation of Whiskers from Electroplated Tin

Abstract

Tin whiskers pose an electrical reliability risk in the form of potential short circuits. This problem was solved in the past by adding a few percent of Pb during Sn electroplating, but with the ban on Pb in Europe and elsewhere, it has resurfaced. While various mitigation strategies have been formulated based on known whisker growth mechanisms, the electronic industry is still awaiting a satisfactory solution to the whisker growth problem in Pb-free electronics. Recent advances in the understanding and mitigation of whiskers are reviewed herein. The effects of various alloying elements/dopants are discussed in terms of the mechanisms that impact whisker growth kinetics and mitigation. Most recently, indium addition to Sn has been found to eliminate whiskers with even better mitigation performance than Pb addition. The mechanisms are discussed, and the important role of indium on the surface oxide and subsurface enrichment is highlighted.

Strategies towards enabling lithium metal in batteries: interphases and electrodes

“…Although whisker growth is not fully understood, the general consensus is that there are necessary conditions for it to occur, such as (1) in-plane compressive stress gradients as a driving force for growth, (2) a fast self-diffusion mechanism for matter transport, and (3) limited surface diffusion, i.e., by a passivating surface layer. 59 As stated, there is evidence that lithium whiskers originate from the same underlying features. 10,50,54 The much earlier nucleation and fast growth of lithium whiskers could be related to a lower activation energy for self-diffusion of lithium, as lithium has the comparably lowest melting point (180.5 1C).…”

“…For tin whiskers, the formation of intermetallic compounds leads to volume expansion and stress build-up. 59 What are the contributing factors to the stress build-up for lithium? For tin whiskers, the grain boundary structure underneath the whiskers is known to be prominently V-shaped.…”

Surface Embedded Metal Nanowire–Liquid Metal–Elastomer Hybrid Composites for Stretchable Electronics

“…In this work, Ag–In alloying to form intermetallic compound (IMC) is responsible for whisker growth. During the IMC formation, in-plane compressive stresses build up in the film due to the large volume expansion. , To relieve these in-plane compressive stresses, a diffusion of Ag and In atoms occurs across the AgNW-LM interface to the surface, leading to the formation of whiskers. Whiskers appear at higher AgNW:LMP weight ratio (i.e., 1:2.4 and 1:4) due to increased number of reaction sites and availability of more In to continue the diffusion process.…”