IEC 60749-25-2003 pdf – Semiconductor devices – Mechanical and climatic test methods – Part 25: Temperature cycling
1 Scope This part of IEC 60749 provides a test procedure for determining the ability of semiconductor devices and components and/or board assemblies to withstand mechanical stresses induced by alternating high and low temperature extremes. Permanent changes in electrical and/or physical characteristics can result from these mechanical stresses. This test method is in general accord with IEC 60068-2-14 but, due to specific requirements of semiconductors, the clauses of this standard apply. This test method applies to single, dual and triple chamber temperature cycling and covers component and solder interconnection testing. In single chamber cycling, the load is placed in a stationary chamber and is heated or cooled by introducing hot, ambient or cold air into the chamber. In dual chamber cycling, the load is placed on a moving platform that shuttles between stationary chambers maintained at fixed temperatures. In triple chamber temperature cycling, the load is moved between the three chambers. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 60068-2-14:1984, Basic environmental testing procedures – Part 2: Tests – Test N: Change of temperature 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 load sample(s) and associated fixtures (trays, racks, etc.) in the chamber during the test 3.2 working zone volume in the chamber(s) in which the temperature of the load is controlled within the specified conditions
3.3 sample temperature T s temperature of the samples during temperature cycling, as measured by thermocouples, or equivalent temperature measurement apparatus, affixed to, or imbedded in, their bodies NOTE The thermocouple, or equivalent temperature measurement apparatus, and whichever attachment or embedding method is used, ensure that the entire mass of the sample(s) reaches the temperature extremes and the soak requirements. 3.4 maximum sample temperature T s,max maximum temperature experienced by the sample(s) as measured by thermocouples (see 3.3) 3.5 minimum sample temperature T s,min minimum temperature experienced by the sample(s) as measured by thermocouples (see 3.3) 3.6 load transfer time time taken to physically transfer the load from one temperature chamber and introduce it into the other NOTE Load transfer applies to dual and triple chamber cycling. 3.7 maximum load largest load that can be placed in the chamber and still meet the specified temperature cycling requirements as verified by thermocouples (see 3.3) 3.8 sample temperature differential ∆T difference between specified T s,max and specified T s,min for the temperature cycling test condition (see Table 1) 3.9 soak time total time the sample temperature is within a specified range of each specified T s,max and specified T s,min NOTE This range is defined as the time T s is at between –5 °C and either +10 °C or +15 °C (dependent on the test condition tolerance) of specified T s,max for the upper end of the cycle and the time T s is at between +5 °C and –10 °C of specified T s,min for the lower end of the cycle. 3.10 soak temperature temperature range that is between −5 °C and either +10 °C or +15 °C (dependent on the test condition tolerance) of specified T s,max and between +5 °C and –10 °C of specified T s,min 3.11 cycle time time between one high temperature extreme to the next, or from one low temperature extreme to the next NOTE For a given sample, see Figure 1.
3.12 ramp rate rate of temperature increase or decrease per unit of time for the sample(s) NOTE 1 Ramp rate should be measured for the linear portion of the profile curve, which is generally in the range of between 10 % and 90 % of the test condition temperature range (see points a) and b) in Figure 1). NOTE 2 Ramp rate can be load dependent and should be verified for the load being tested. 3.13 test conditions various temperature cycle range options listed in Table 1 3.14 soak mode minimum soak time at soak temperature (maximum) and soak time (minimum). Each test condition will have four possible soak modes. These soak modes are listed in Table 2. The soak mode selected is dependent on the failure mechanism of interest. 4 Test apparatus The chamber(s) used shall be capable of providing and controlling the specified temperatures and cycling time in the working zone(s), when the chamber is loaded with a maximum load. Direct heat conduction to sample(s) shall be minimized. The capability of each chamber achieving the sample temperature requirements shall be verified across each chamber for a given load by one or both of the following methods: a) Periodic calibration using instrumented parts and a maximum load, and continual monitoring during each test of such fixed tool thermocouple temperature measurement(s) as adequate to ensure run-to-run repeatability. b) Continual monitoring during each test of an instrumented part or parts placed at worst- case temperature locations (for example, this may be the corners and middle of the load).