Quantifying the Rates of Sn Whisker Growth and Plastic Strain Relaxation Using Thermally-Induced Stress

In certain applications, IC packages may be exposed to extreme temperatures and knowledge of thermally induced stress aids the prediction of performance degradation or failure of the IC. In the devices that are used in extreme conditions, the stress is caused mainly by the mismatch in expansion of various materials triggered by the different coefficients of thermal expansion. This work performed in this study is conducted using NMOS current mirror circuits that are cycled through a wide temperature range of −180°C to 80°C. These circuits are highly sensitive to stress and provide well-localized measurements of shear stress. The sensors are fabricated in such a way that the effects of certain stress components are isolated. These sensors are also temperature compensated so that only the effect of mechanical stress components is observed and changes in device performance due to temperature changes are minimal. Current readings obtained from the sensors are used to extract the shear stress component. Finite element simulations, using expected materials performance parameter information were also performed for similar packages and these results are compared to the measured results.

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The Effect of Micro-Alloying of Sn Plating on Mitigation of Sn Whisker Growth

Journal of Electronic Materials ◽

10.1007/s11664-009-0915-z ◽

2009 ◽

Vol 38 (12) ◽

pp. 2726-2734 ◽

Cited By ~ 12

Author(s):

Aleksandra Dimitrovska ◽

Radovan Kovacevic

Keyword(s):

Whisker Growth ◽

Sn Whisker

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Effect of Environment on Sn Whisker Growth during Welding of Electronic Wires

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1110.235 ◽

2015 ◽

Vol 1110 ◽

pp. 235-240 ◽

Cited By ~ 1

Author(s):

Tomomi Sakakida ◽

Tatsuo Kubouchi ◽

Yasuyuki Miyano ◽

Mamoru Takahashi ◽

Osamu Kamiya

Keyword(s):

Energy Balance ◽

Weld Metal ◽

Whisker Growth ◽

Weld Zone ◽

Electrolytic Capacitor ◽

Sn Whisker ◽

Sn Whiskers ◽

Weld Metal Microstructure ◽

Short Circuits ◽

Metal Microstructure

In Pb-free Al-Sn welding of electrolytic parts, single-crystal Sn whiskers easily form and can cause problems such as short circuits. Here we report that the growth of Sn whiskers in the weld zone of Al electrolytic condenser leads was suppressed in a vacuum environment. We examined the effect of the environment and weld metal microstructure in order to understand how to control and prevent whisker growth. In vacuum, the weld zone did not form whiskers after more than 100 h, whereas in air, whiskers grew within several hours. This suggests that whiskers require oxygen to form. The growth can be explained by the energy balance between the potential energy of the weld metal and the surface energy of the whisker. Our results will contribute to developing techniques for suppressing the formation of Sn whiskers during the percussion welding of Al electrolytic capacitor leads.

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Towards improving the physical basis for ice-dynamics models

Annals of Glaciology ◽

10.1017/s0260305500013999 ◽

1997 ◽

Vol 25 ◽

pp. 177-182 ◽

Cited By ~ 7

Author(s):

J. A. Richter-Menge

Keyword(s):

High Frequency ◽

Low Frequency ◽

The Arctic ◽

Frequency Content ◽

Ice Dynamics ◽

Relative Significance ◽

Thermally Induced ◽

Induced Stress ◽

Dynamics Models

In situ measurements of ice stress were made on a multi-year floe in the Alaskan Beaufort Sea over a 6 month period, beginning in October 1993. The data suggest that, in this region of the Arctic during this experiment, there were two main sources of stress: a thermally induced stress caused by changes in air temperature, and a stress generated by ice motion. Due to the natural damping of the snow and ice above the sensor, the thermally-induced stresses are low frequency (order of days). Stresses associated with periods of ice motion have both a high-frequency (order of hours), and low-frequency, content. The relative significance of these sources of stress is seasonal, reflecting the changes in the strength and continuity of the pack.

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