Tin Whiskers

Gideon Analytical Labs performed analysis on several Melexis US2881 Sensors when the designer found shorts on the returned product from the field.

Melexis US2881 sensors are bipolar Hall-effect switches designed in mixed signal CMOS technology. They have a wide voltage operating range from 3.5V to 24V, have high magnetic sensitivity, and a chopper-stabilized amplifier stage, and are suitable for automotive or consumer applications.

Analysis revealed tin crystals (whiskers) spread throughout the top and bottom of the PCB, shorting out the MOSFET as well as the Hall sensor. Micrograph (left) and SEM-EDS analysis confirmed the presence of tin whiskers causing a short in both positive and negative leads. The tin whisker growth took place over several days to develop without voltage and with conditions known to promote growth.

The failure analysis demonstrated that not only does the company have a potential process concern but the environment in which this Melexis US2881 sensor, thus, the printed circuit board, is installed in contributes to the growth of the tin whiskers.

Gideon Analytical Laboratories can solve many organic and inorganic problems causing circuit corrosion and leakage current between components on the PCB. We inspect to class I, II, and III levels. We do work for different sectors in the industry using electronics in their designs. We can reverse engineer, design, or review schematics and perform the analysis also.

Micrograph of tin growth

Micrograph of tin growth

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