High Temperature Storage (HTS)

The High-Temperature Storage (HTS)  test is performed to determine the effect on devices of long-term storage at elevated temperatures without any electrical stresses applied.  HTS is similar to Stabilization Bake (Mil-Std-883 Method 1008), except that HTS is done over a much longer period of time (1000 hours vs. 24 hours for Stab Bake at 150 deg C).  The purpose of HTS is to assess the long-term reliability of devices under high temperature conditions while that of Stabilization bake is merely to serve as part of a screening sequence or as a preconditioning treatment prior to the conduct of other tests.

Both HTS and stab bake consist of storing the parts at the specified ambient temperature for a specified amount of time.  The devices must be allowed to reach the specified temperature before the duration starts counting.  End-point measurements must be conducted within 96 hours after the specified test conditions are removed.  For HTS, end-point measurements include external visual inspection and electrical testing.

HTS is not a substitute for burn-in because it does not subject its samples to electrical stresses.  Nonetheless, HTS is effective for the reliability testing of samples in terms of mechanisms accelerated by temperature only, e.g., oxidation, bond and lead finish intermetallic growths, etc.  Any oven or chamber capable of providing controlled elevated temperature may be used for HTS (see example in Fig. 1).

Figure 1.  Example of a Bake Chamber/Oven that can be used for High Temperature Storage

Summary of industry-standard HTS conditions: 1000 hours at 150 deg C.

Mil Std 883, Method 1008, Stabilization Bake Specs :

-  storage at a high temperature for a specified duration

-  Test Condition A :  75 deg C / 24 hours minimum

-  Test Condition B :  125 deg C / 24 hours minimum

-  Test Condition C :  150 deg C / 24 hours minimum

-  Test Condition D :  200 deg C / 24 hours minimum

-  Test Condition E :  250 deg C / 24 hours minimum

-  Test Condition F :  300 deg C / 24 hours minimum

-  Test Condition G :  350 deg C / 24 hours minimum

-  Test Condition H :  400 deg C / 24 hours minimum

Reliability Tests:   Autoclave Test or PCT;  Temperature Cycling;  Thermal Shock; THB;  HAST;  HTOL;  LTOL;  HTS;  Solder Heat Resistance Test (SHRT); 

Other Reliability Tests