Tin Whisker Testing
Omar Al Taher, Applications Engineer
In order to evaluate the tin whisker growth on pure tin and tin lead plated capacitors Johanson Dielectrics performed tin whisker testing on various sizes of capacitors using iNEMI and JESDA121 test methods.
The following samples were tested:
- 0805 X7R Pure Matte Tin Finish with nickel barrier
- 1210 X7R Pure Matte Tin Finish with nickel barrier
- 1210 X7R Tin Lead Finish with 5% minimum lead content (same lot as pure tin part)
- 1812 X7R Pure Matte Tin Finish with nickel barrier
Two different tests were performed:
- Temperature Cycle Test:
Temperature Cycle per JESD22-A104 Test Condition A Soak Mode 3 1000 cycles SEM inspections per JESD22-A121. The parts are temperature cycled from -55C to 85C, with a minimum of 10 minutes soak time at the minimum and maximum temperatures.
- Temperature Humidity Test:
4000 hours at 60 C and 93% relative humidity per iNEMI recommendations.
The capacitors were inspected by SEM before and after each test at 250 and 2500 magnification.
The parts were evaluated to the requirements of Class 2 devices as stipulated by iNEMI 'Tin Whisker Acceptance Test Requirements', July 28, 2004, paragraph 18.2.3. The maximum acceptable whisker length is 40 um.
The whisker length reported is the total axial whisker length as per JEDEC standard JESD22A121 definition 3.1. Although only whiskers of 10um or greater in length are classified as 'true' whiskers as per JEDEC standard JESD22A121 definition 3.2, whiskers of all lengths are reported below.
|Part Description||Number of parts tested||Temp Cycling (1000 cycles)||Temp Humidity (4000 hrs)||Meets iNEMI Class 2C(ref)|
|0805 Pure Tin||15||4||No Whiskers Present||Yes|
|1210 Pure tin||9||14||1||Yes|
|1812 Pure Tin||9||17||No Whiskers Present||Yes|
|1210 Tin Lead||9||No Whiskers Present||No Whiskers Present||Yes|
0805 size pure tin 2500x magnification time 0
0805 size pure tin 2500x magnification 1000 Temperature Cycles
0805 size pure tin 250x magnification 1000 Temperature Cycles