Tin Whiskers, Part 4: Causes and Contributing Factors


Reading time ( words)

In this installment of the tin whisker series, we'll take a look at causes and factors that have been found or are considered to contribute to the appearance of tin whiskers. In the remaining installments, we will address “Tin Whiskers - Plausible Theory,” “Tin Whiskers - Impact of Testing Conditions,” and “Tin Whiskers - Preventive and Mitigating Measures.”   

As all-encompassing tests to confirm or deny the culprits that cause tin whiskers are prohibitively costly and time-consuming, my thoughts focus on the logical causes and contributors. Fundamentally, the tin whisker follows the basic physical metallurgy in its principles on nucleation and crystal growth through the classic theories of dislocation dynamics and of other lattice defects in tin crystal structure. Thus, for whiskers to appear from the tin-plated (or tin-coated) surface, the causes and contributing factors should be intimately related to the nucleation sites creation and the subsequent growth paths after the coating process. However, for tin whisker due to tin’s intrinsic characteristics, the actual processes of nucleation and grain growth are dauntingly complex.

Nucleation and growth can be encouraged by stresses introduced during and after the plating process. The sources of these stresses come from multi-fronts. This includes residual stresses caused by electroplating and/or additional stresses imposed after plating, and/or the induced stresses by foreign elements, and/or thermally-induced stresses. Specific causes and contributing factors are outlined below.

Read the full column here.


Editor's Note: This column originally appeared in the March 2014 issue of SMT Magazine.

Share

Print


Suggested Items

Solder Paste Printing From the Stencil’s Perspective

02/19/2020 | I-Connect007 Editorial Team
Jeff Schake of ASM Assembly Systems discusses the complications surrounding printing and solder paste that he sees from his perspective as a stencil expert.

PCB Repair: Thoughtful Best Practices

12/31/2019 | Barry Matties, I-Connect007
Barry Matties recently spoke with Curtis Smith of Huntron about the critical factors that somebody needs to understand about the plant maintenance regarding the PCB repair process. The PCB repair process is not just a matter of just getting the equipment anymore but finding the right people with a troubleshooting mindset that can do it. A failed PCB can bring down an entire manufacturing line, and companies need to be able to repair the board and keep their manufacturing going.

Book Summary: The Printed Circuit Assembler’s Guide to…Process Validation

12/19/2019 | I-Connect007 Editorial Team
The latest book in I-Connect007’s "The Printed Circuit Assembler’s Guide to…" series is authored by Gen3’s Graham Naisbitt. With his deep background in process validation and standards work, Naisbitt is uniquely qualified to explore achieving acceptable electrochemical reliability using both CAF and SIR testing. This eBook is a perfect present for the holidays.



Copyright © 2020 I-Connect007. All rights reserved.