Tin Whiskers, Part 5: Impact of Testing Conditions

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In this installment of the tin whisker series, we'll take a look at the impact of testing conditions, and follow-up with this statement from Part 4: “…all-encompassing tests to confirm or deny the culprits for tin whiskers are prohibitively costly and time-consuming…”

The JEDEC Solid State Technology Association (formerly known as the Joint Electron Device Engineering Council) has published several documents that address and/or are related to the testing of tin whiskers, which are good guidelines with which to start.

• JEDEC Standard No. 201: Environmental Acceptance requirements for Tin Whisker Susceptibility of Tin and Tin Alloy Surface Finishes.
• JEDEC Standard No. 22A12: Measuring Whisker Growth on Tin and Tin Alloy Surface Finishes.
• JEDEC Standard No. 22-A104D: Temperature Cycling.

Primarily, three sets of testing conditions are included in the JEDEC documents: ambient temperature storage, elevated temperature storage and temperature cycling, with the following parameters:

Room  Temperature Humidity Storage
30 ± 2°C and 60 ± 3% RH
(1,000 hrs interval inspection/3,000 to 4,000 hours total duration)      

Temperature Humidity Unbiased
60 ± 5°C and 87 + 3/-2% RH
(1,000 hours interval inspection/3,000 to 4,000 hours total duration)      

Temperature Cycling
Lower end temperature: -55 to -40 (+0/-10)°C
Higher end temperature: +85 (+10/-0)°C
(500 cycles inspection /1,000 to 1,500 cycles duration/air to air/5 to 10 minute soak/three cycles per hour)

Read the full column here.


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

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