Lab Companion,Thermal Shock Test (TST)
Thermal Shock is performed to determine the resistance of the part to sudden changes in temperature. The parts undergo a specified number of cycles, which start at ambient temperature. The parts are then exposed to an extremely low (or high) temperature and, within a short period of time, exposed to an extremely high (or low) temperature, before going back to ambient temperature.
After the final cycle, external visual examination of the case, leads, and seals shall be performed at 10 X to 20 X. The marking shall also be inspected at no greater than 3 X. An illegible mark and/or any evidence of damage to the case, leads, or seals after the stress test shall be considered a failure.
Electrical testing of the samples to device specifications must also be performed to detect electrical failures accelerated by the temp cycle.
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Fig. 1. A Thermal Shock Chamber
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Failure acceleration due to Thermal Shock and Temp Cycling depends on the following factors: 1) the difference between the high and low temperatures used; 2) the transfer time between the two temperatures; and 3) the dwell times at the extreme temperatures.
Failure mechanisms accelerated by thermal shock include die cracking, package cracking, neck/heel/wire breaks, and bond lifting.
For reliability testing or qualification of new devices, 1000 temp cycles are usually performed, with interim visual inspection and electrical test read points at 200X and 500X.
Two industry standards that govern Temp Cycle Testing are the Mil-Std-883 Method 1011 and the JEDEC JESD22-A106.
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Mil-Std-883, Method 1011 Specs : Thermal Shock Test
- Total Transfer Time < 10 seconds
- Total Dwell Time > 2 minutes
- Specified Temp reached in < 5 minutes
- Must be conducted for a minimum of 15 cycles
Table 1. Mil-Std-883 Method 1011 Thermal Shock Test Conditions
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Condition
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Low Temp
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High Temp
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A
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-0 (+2/-10) deg C
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100 (+10,-2) deg C
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B
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-55 (+0/-10) deg C
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125 (+10,-0) deg C
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C
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-65 (+0/-10) deg C
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150 (+10,-0) deg C
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JEDEC JESD22-A106 Specs : Thermal Shock Test
- Total Transfer Time < 10 seconds
- Total Dwell Time > 2 minutes
- Specified Temp reached in < 5 minutes
- Must be conducted for a minimum of 15 cycles
Table 1. Mil-Std-883 Method 1011 Thermal Shock Test Conditions
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Condition
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Low Temp
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High Temp
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A
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-40 (+0/-30) deg C
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85 (+10/-0) deg C
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B
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-0 (+2/-10) deg C
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100 (+10,-2) deg C
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C
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-55 (+0,-10) deg C
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125 (+10,-0) deg C
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D
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-65 (+0,-10) deg C
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150 (+10,-0) deg C
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