Thermal Shock Testing

Thermal shock testing moves a product between a hot chamber and a cold chamber fast enough that the two halves of an assembly cannot expand and contract together. It is called out by IEC 60068-2-14 Test Na, MIL-STD-810 Method 503, MIL-STD-202 Method 107 and MIL-STD-883 Method 1011, and it is the test that finds cracked solder joints, failed seals and delaminated coatings that a slow temperature cycle will pass. Megalab runs it on two dedicated air to air chambers, accredited to ISO/IEC 17025 by A2LA.

Every assembly is made of materials that expand at different rates. A ceramic package on an FR-4 board, a potted connector, a coated casting: each pair of materials moves at its own speed when the temperature changes. Given time, they move together and the stress stays low.

Thermal shock removes the time. The transfer between zones happens in seconds, so the outside of the part reaches the new temperature while the inside is still at the old one. The strain concentrates exactly where a product fails in service, which is why qualification programs use it as a screen rather than as a simulation of any real environment.

The failures it surfaces are consistent: solder joint fatigue, wire bond lift, seal and gasket leaks, cracked encapsulant, coating delamination, and glass to metal seal failure.

Both take a product between temperature extremes, and specifications use the words loosely, so it is worth being exact.

• Temperature cycling: ramps a single chamber up and down at a controlled rate, so the whole part follows the ramp together. Run to IEC 60068-2-14 Test Nb or MIL-STD-883 Method 1010.
• Thermal shock: holds two zones at their setpoints and physically moves the sample between them. There is no ramp. Run to IEC 60068-2-14 Test Na or MIL-STD-810 Method 503.

If a specification gives a transfer time, it means shock. If it gives a ramp rate in degrees per minute, it means cycling. When a specification is ambiguous, send it to us and we will tell you which one it describes before anything is quoted.

Both systems are vertical air to air designs with a moving basket. The zones stay at temperature and the sample travels, which is what keeps the transfer time short.

• Large chamber: a 25 inch cube basket taking up to 54 kg, running -65 C to 200 C, with transfer in 10 seconds or less. Liquid nitrogen assisted cooling lets the cold zone recover between transfers on a heavy load.
• Small chamber: a 25 x 14 x 14.5 inch basket taking up to 45 kg, running -73 C to 215 C, with transfer in about 8 seconds.

Accredited by A2LA to ISO/IEC 17025 under certificates 5179.01 and 5179.02. See our accreditations.

Electronics and semiconductor manufacturers qualifying boards, packages and modules. Connector and cable assembly makers working to EIA-364 and MIL-STD-1344. Aerospace and defence suppliers with a MIL-STD-810 or DO-160 program. Medical device manufacturers proving a sealed enclosure. Automotive component suppliers, where thermal shock is a standard part of a validation plan.

Thermal shock rarely arrives alone. Most programs pair it with temperature testing or with vibration and shock, and enclosed products usually add ingress protection.

• The standard and method, or your internal specification
• Overall dimensions and weight of the sample, so we can confirm basket fit
• Number of samples
• Whether the sample is powered or monitored during the test, and what the fixturing needs to be
• The temperature extremes and the number of cycles your specification calls for
• Whether you need a functional check between cycles, and who performs it

Send us the specification and we will confirm the requirement and quote it.