Low-temperature storage testing verifies whether products, components, and materials can withstand prolonged exposure to cold environments—such as unheated warehouses, winter transport, and high-altitude cargo holds—without damage or performance loss. This article explains the essential requirements of low-temperature storage inspection based on standards such as IEC 60068-2-1, GB/T 2423.1, and ISO 16750-4, covering sample preparation, test severities, test procedures, and acceptance criteria.
Technical Overview
Low-temperature storage testing, also known as cold storage testing or low-temperature exposure testing, is an environmental reliability test that evaluates the ability of a specimen to endure extended periods at sub-ambient temperatures while in a non-operating state. The test simulates real-world cold scenarios such as winter storage, refrigerated logistics, outdoor installation in cold climates, and air transport, after which the specimen is inspected for physical damage and functional degradation.
The most widely applied framework is IEC 60068-2-1 (Environmental testing — Part 2-1: Tests — Test A: Cold), in particular Test Ab, which covers cold exposure of non-heat-dissipating specimens with the power switched off. Equivalent national adoptions include GB/T 2423.1, EN 60068-2-1, and JIS C 60068-2-1. Sector-specific variants include ISO 16750-4 for automotive electrical and electronic equipment, IEC 62133 and UL 1642 / UL 2054 for rechargeable cells and batteries, and ASTM D4332 for conditioning packaging before cold-environment testing.
Cold exposure accelerates several characteristic failure mechanisms: embrittlement and shrinkage of polymers, differential thermal contraction between dissimilar materials, hardening of elastomeric seals and lubricants, changes in electrolyte behavior within cells, condensation during recovery, and cracking of solder joints or adhesive bond lines. A well-defined low-temperature storage inspection program therefore specifies not only the exposure conditions but also the post-test measurements used to detect these latent defects.
Testing Samples
Electronic Components and Assemblies
Printed circuit board assemblies, connectors, relays, switches, passive components, displays, and power modules are commonly subjected to cold storage at −25 °C to −55 °C to confirm that packaging, marking, solder joints, and material interfaces survive storage and distribution before the product is put into service.
Batteries and Energy Storage Products
Lithium-ion cells and battery packs must satisfy low-temperature storage and thermal test requirements under IEC 62133 and the UN 38.3 transport regulation (Test T.2, which exposes cells to −40 °C and +72 °C). Post-test checks cover open-circuit voltage retention, capacity recovery, case integrity, and the absence of leakage, deformation, or venting.
Automotive and Transportation Equipment
Under ISO 16750-4, electronic control units, sensors, lighting devices, displays, and wiring harnesses for road vehicles are stored at low temperature—typically −40 °C for 24 h in the unpowered state—prior to functional assessment. Rail, marine, and outdoor-installed equipment follow equivalent climatic specifications.
Packaging, Polymers, and Materials
Shipping containers, labels, tapes, adhesives, sealants, coatings, rubber parts, and plastic enclosures are conditioned at low temperature in accordance with ASTM D4332 and product-specific material standards, then evaluated for brittleness, delamination, seal strength, and dimensional stability.
Sample quantity and pre-test conditioning are defined by the product specification; at least three identical specimens are generally recommended. Specimens should first be stabilized in the standard laboratory atmosphere (23 °C ± 2 °C, or 23 °C ± 5 °C for inspection only, with relative humidity typically between 45 % and 75 %).
Testing Items
A complete low-temperature storage inspection typically covers the following test parameters and measurement items:
- Exposure temperature (severity level): commonly −10 °C, −20 °C, −25 °C, −30 °C, −40 °C, −55 °C, or −65 °C, selected according to the intended storage and transport environment.
- Exposure duration: commonly 24 h, 48 h, 72 h, or 96 h, counted only after the specimen reaches temperature stabilization.
- Appearance inspection: cracks, crazing, blistering, deformation, discoloration, marking legibility, corrosion, and integrity of coatings and platings.
- Functional verification: correct operation of all functions and normal mechanical movement of hinges, latches, connectors, and seals after recovery.
- Electrical performance: continuity, insulation resistance, dielectric withstand, contact resistance, and drift of key electrical parameters against specification limits.
- Mechanical and material properties: tensile and impact behavior, seal or peel strength, hardness changes, and dimensional measurements.
- Battery-specific items: open-circuit voltage, remaining capacity, internal resistance, and evidence of leakage, swelling, or venting.
Testing Methods
Initial Inspection and Conditioning
Specimens are documented with serial numbers and photographs, then subjected to initial visual, dimensional, functional, and electrical measurements. Establishing baseline data before exposure is essential for quantifying parameter drift after the test.
Exposure Procedure
Specimens are placed in a climatic test chamber in the unpowered (storage) state. Good practice limits the total specimen volume to no more than one-fifth of the chamber working volume, keeps specimens clear of chamber walls and airflow obstructions, and avoids overlapping of specimens. The chamber is then brought to the specified severity—either by transferring pre-stabilized specimens into the cold chamber or by ramping the temperature at no more than 1 K/min where a gradual transition is required. The dwell time starts only after the specimen reaches thermal stabilization, and the target temperature is maintained within a tolerance typically of ±2 K to ±3 K for the specified duration.
Recovery
After exposure, specimens are removed and allowed to recover under standard atmospheric conditions. Recovery lasts until thermal stabilization—commonly 1 h to 2 h for small specimens and longer for thermally massive assemblies. If condensation could affect the evaluation, specimens should remain in a closed container or protective covering until they reach room temperature before being unwrapped.
Final Inspection and Acceptance Criteria
Final inspection repeats the initial measurements. Acceptance criteria, defined by the applicable product standard or specification, typically require: no visible damage such as cracks or permanent deformation; full functional compliance; electrical parameters within the specified drift limits; intact seals and interfaces; and, for batteries, voltage and capacity retention within limits with no leakage. Any deviation is recorded, photographed, and assessed against the pass/fail criteria.
Equipment and Laboratory Requirements
Test chambers shall cover the required temperature range (typically down to −40 °C or −70 °C) with temperature uniformity and stability compliant with IEC 60068-3-5, and shall be calibrated at regular intervals. Testing performed by accredited third-party laboratories operating under ISO/IEC 17025 ensures traceable measurements and internationally recognized test reports.
Applications
Low-temperature storage inspection is applied across industries in which products must survive cold supply chains or cold service environments:
- Consumer and industrial electronics: verification of storage robustness for computers, household appliances, instrumentation, and telecom hardware installed outdoors.
- Automotive and electric vehicles: qualification of electronic control units, sensors, connectors, displays, and traction battery components per ISO 16750-4.
- New energy and energy storage systems: cells, modules, and battery management hardware evaluated under IEC 62133 and applicable transport regulations.
- Aerospace and defense: equipment qualified for high-altitude and arctic deployment, often combining cold storage with low-pressure and vibration sequences.
- Packaging and cold-chain logistics: insulated shippers, labels, and adhesives used in refrigerated and frozen distribution channels.
- Medical devices and pharmaceutical delivery systems: products that must remain intact after storage or shipment under refrigerated conditions.
FAQ
What is the difference between low-temperature storage testing and low-temperature operation testing?
In storage testing, the specimen is unpowered and must only survive the exposure and function normally after recovery; this corresponds to IEC 60068-2-1 Test Ab for non-heat-dissipating specimens. In operation testing, the specimen remains powered and must perform its intended functions while still at the low temperature, which is addressed by procedures such as Test Ad for heat-dissipating, energized specimens.
Which temperature level and duration should be selected?
Severity is chosen based on the worst-case storage environment defined in the product specification. Common commercial levels are −20 °C to −40 °C for 24 h to 48 h; automotive electronics typically use −40 °C for 24 h per ISO 16750-4; and military or extreme-climate applications may require −55 °C or −65 °C. When the service environment is uncertain, manufacturers select the nearest higher severity to provide design margin.
Are GB/T 2423.1 and IEC 60068-2-1 equivalent?
GB/T 2423.1 is technically aligned with IEC 60068-2-1, so the test conditions, severity levels, and procedures are essentially equivalent. Reports referencing either standard are normally accepted interchangeably, although the applicable edition should be confirmed with the end customer or purchasing specification.
Why is the recovery period before final measurement important?
Measurements taken while the specimen is still cold can show transient parameter shifts and condensation effects that do not represent permanent damage. Evaluating the specimen after thermal stabilization in the standard atmosphere distinguishes recoverable transient behavior from true degradation caused by the cold exposure.
How many samples are required, and what happens if a sample fails?
Most specifications require a minimum of three identical specimens for statistical confidence. If any specimen exhibits cracking, functional failure, or out-of-tolerance parameters after cold storage, the batch is typically considered non-conforming, and failure analysis is performed to identify the root cause before design or process corrective actions are implemented.