Lab Companion,Temperature Cycle Test (TCT)

Lab Companion,Temperature Cycle Test (TCT)  

Temperature Cycle Testing (TCT), or simply temperature cycling or temp cycling, determines the ability of parts to resist extremely low and extremely high temperatures, as well as their ability to withstand cyclical exposures to these temperature extremes.  A mechanical failure resulting from cyclical thermomechanical loading is known as a fatigue failure, so temperature cycling primarily accelerates fatigue failures. Thermal Shock Testing (TST) closely resembles TCT and also accelerates fatigue failures.

TCT consists of subjecting the parts to the specified low (or high) temperature then subjecting the same units to the specified high (or low) temperature for a specified number of cycles using an equipment known as a Temperature Cycle Chamber.

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. 

Fig. 1. Examples of Temperature Cycle Machines

Electrical testing of the samples to device specifications shall also be performed to detect electrical failures accelerated by the temp cycle.

Failure acceleration due to Temp Cycling and Thermal Shock 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 temperature cycling 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 1010 and the JEDEC JESD22-A104.

Mil-Std-883, Method 1010 Specs :  Temperature Cycle Test

-  Total Transfer Time <= 1 minute

-  Total Dwell Time >= 10 minutes

-  Specified Temp reached in <= 15 minutes

-  Must be conducted for a minimum of 10 cycles

Table 1. Mil-Std-883 Method 1010 Temp Cycle Test Conditions

JEDEC JESD22-A104 Specs :  Temperature Cycle Test

-  Total Transfer Time <= 1 minute

-  Total Dwell Time >= 10 minutes

-  Specified Temp reached in <= 15 minutes  

-  Recommended for lot acceptance screen :  10 cycles

-  Recommended for qualification :  1000 cycles

Table 2. JEDEC JESD22-A104 Specs  Temp Cycle Test Conditions

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