Temperature cycling vs thermal shock: what's the difference?

How each one is produced

Temperature cycling uses a single chamber. The product stays where it is, and the chamber drives the air around it between the two extremes at a controlled rate, with a dwell at each end. Hanse TC thermal chambers and VTC HALT/HASS chambers cycle this way, cooling by liquid-nitrogen direct injection, and reach a 70 °C/min product change rate*.

Thermal shock uses two zones, one hot and one cold, each held at its temperature. The product is moved from one zone to the other, typically in a basket, so the transition is as fast as the transfer. Hanse builds air-to-air thermal shock chambers, from −150 to +200 °C with baskets sized to the product, as custom builds: see Built to your specification.

*Measured 4” above center of table, −65 °C to +100 °C.

Which one a standard asks for

Both are qualification tests: the standard or the product’s test specification sets the extremes, the transition and the number of cycles, and the product passes or fails.

• IEC 60068-2-14, Test N: change of temperature, is the IEC test for changes of temperature. The current edition, 7.0 of 2023, has two tests. Test Na, rapid change of temperature with prescribed time of transfer, moves the specimen between two chambers held at the two temperatures: thermal shock. Test Nb, change of temperature with specified rate of change, keeps it in one chamber while the temperature changes at a set rate: temperature cycling. The product’s test specification says which applies and at what severity. Issuer: IEC webstore.
• MIL-STD-810H, Method 503.7, is temperature shock. Issuer: DLA ASSIST.

The standards guide summarizes both standards and where they fit.

Which one your product needs

Repeated temperature cycling works on fatigue. The materials in an assembly expand and contract by different amounts for the same change in temperature, so each cycle adds strain to solder joints and interconnects until a marginal one opens. Thermal shock asks a different question: whether the product survives an abrupt change of temperature at all. Which one you need depends on the environment the product will see in service and on the standard or customer specification it has to meet.

How this relates to HALT

HALT uses rapid thermal transitions as one of its stresses, cycling at the fastest rate the chamber can deliver between temperatures inside the limits the HALT has found. Its purpose is to find the product’s limits, not to reproduce a cycling or shock test from a standard, and a HALT result does not demonstrate compliance with one. See What is HALT testing? and the standards guide.