IEC 60068-2-38:2021

Overview

IEC 60068-2-38:2021 (Test Z/AD) is an international environmental test standard that defines a composite temperature/humidity cyclic test primarily for component-type specimens. The procedure is an accelerated method to evaluate resistance to deterioration caused by alternating high temperature/humidity and cold (including sub-zero) conditions. This third edition (2021) replaces the 2009 edition and includes updated figures and clarified wording. The standard is part of the IEC 60068 series on environmental testing.

Key Topics and Requirements

• Purpose: Detect defects caused by “breathing” (pumping of moist air into internal voids) and the effects of freeze-thaw cycles on materials and assemblies.
• Test scope: Intended mainly for non-energized specimens during the complete test; specimens may be energized during constant phases only. Measurements are normally taken during constant phases unless specified otherwise.
• Composite cycling: Combines repeated temperature/humidity variations with excursions to sub-zero temperatures to accelerate moisture ingress and freezing-induced damage.
• Mechanisms addressed: Condensation formation, moisture absorption vs. breathing, pressure changes in internal voids, and crack extension due to ice expansion.
• Test sequence elements: Preconditioning, initial measurements, conditioning, cyclical temperature/humidity subcycles, cold subcycles, intermediate measurements, and final measurements.
• Test environment requirements: Specific chamber descriptions for humidity and cold exposure, severities, and tolerances are provided (see Annex A for set points and tolerances).
• Documentation: The standard specifies what information to include in relevant specifications and in test reports.

Applications and Users

• Who uses it: Component engineers, reliability test labs, product qualification teams, and environmental test specialists in electronics, electromechanical devices, and related industries.
• Practical uses:
  • Assessing seal integrity, connector reliability, PCB coatings, and component packaging under cyclic humid and cold conditions.
  • Accelerated qualification for parts expected to experience rapid humidity changes and freezing in service environments.
  • Root-cause investigation of moisture-related failures (corrosion, insulation breakdown, mechanical fissures).
• Why use it: Provides a reproducible accelerated test to reveal moisture ingress and freeze-thaw vulnerabilities that may not appear in steady-state damp heat tests.

Related Standards

• IEC 60068-1 (General and guidance)
• IEC 60068-2-30 (Test Db: Damp heat, cyclic)
• IEC 60068-2-78 (Test Cab: Damp heat, steady state)
• IEC 60068-2-67 (Test Cy: Accelerated damp heat for components)
• IEC Guide 104 (Safety publication preparation)

Using IEC 60068-2-38 supports robust environmental testing plans by specifically targeting moisture “breathing” and freeze-induced damage - key concerns for long-term reliability of electrical and electronic components.