Power durability testing under mechanical shock evaluates whether electronic components can maintain safe and stable electrical performance while simultaneously subjected to mechanical shock pulses and rated electrical loading. This combined-stress reliability test is critical for varistors, resistors, capacitors, and surge protective devices deployed in automotive, industrial, and aerospace environments. Accredited third-party laboratories conduct this testing in accordance with IEC 60068-2-27, GB/T 2423.5, ISO 16750-3, and related component-level specifications.
Technical Overview
Power durability testing under mechanical shock is a combined environmental and electrical stress test designed to verify that a component remains electrically safe and functionally stable when mechanical shock is applied while the component is energized at its rated voltage or power. In real-world service, electronic parts in vehicles, aircraft, rail systems, and industrial machinery routinely experience impact events such as road shocks, door slams, cargo handling, and assembly drops while carrying electrical load. A ceramic body with a latent crack or a weak internal electrode connection may survive a shock test alone, yet fail catastrophically once voltage is present across the defect.
By superimposing the rated electrical load onto the mechanical shock sequence, this test exposes failure modes that single-stress testing cannot detect, including internal short circuits, intermittent contact, insulation breakdown, and thermal runaway triggered by shock-induced structural damage. The mechanical shock portion of the test is typically performed according to IEC 60068-2-27 or its Chinese equivalent GB/T 2423.5, while component-specific acceptance criteria are defined in product standards such as IEC 61051-2 and GB/T 10193 for varistors, IEC 60384 for capacitors, ISO 16750-3 for automotive electrical equipment, and UL 1449 for surge protective devices.
Testing Samples
Metal Oxide Varistors (MOV)
Surge suppression varistors are among the most frequently tested components for this condition, because a cracked varistor disc under continuous voltage can overheat, crack further, or catch fire. Testing verifies that the varistor voltage and leakage current remain within tolerance after shock under load.
Thermistors (NTC and PTC)
Inrush-limiting and protection thermistors are tested to confirm that mechanical shock does not fracture the ceramic pellet or disturb the lead attachment while the device dissipates rated power.
Fixed and Power Resistors
Thick-film, thin-film, and wirewound resistors are evaluated for resistance drift, open circuit, and coating integrity when shock is applied during rated power dissipation.
Ceramic and Film Capacitors
Multilayer ceramic capacitors are particularly sensitive to mechanical stress, which can propagate delaminations or cracks that short under applied DC or AC voltage.
Surge Protective Devices and Modules
Complete SPD assemblies and power distribution modules are tested to confirm that terminals, internal connections, and disconnect devices remain secure and safe when shocked in an energized state.
Testing Items
The test assesses both structural survival and electrical stability under combined loading. Typical measured and inspected items include:
- Electrical continuity, confirming no open circuit occurs during or after the shock sequence
- Short-circuit behavior, confirming no dielectric breakdown or internal shorting develops under load
- Varistor voltage (measured at a specified DC test current) and its rate of change relative to the initial value, typically limited to within ±10 percent
- Leakage or current consumption at rated DC voltage after recovery
- Insulation resistance between live parts and accessible conductive parts
- Dielectric withstand (electric strength) verification after the shock exposure
- Visual inspection for cracks, chipping, breakage, lead loosening, coating damage, or marking illegibility
- Absence of smoke, flame, arcing, or abnormal temperature rise during energized shock exposure
Testing Methods
Sample Preparation and Initial Measurement
Samples are selected according to the sampling plan of the applicable product standard, conditioned at standard atmospheric conditions, and measured for baseline parameters such as varistor voltage, resistance, capacitance, or leakage current. These initial values establish the reference for post-test comparison.
Mounting and Fixture Requirements
Each specimen is rigidly mounted on the shock test table or shock machine using fixtures that replicate normal installation, with leads or terminals secured in a manner representative of end use. Improper fixture stiffness can amplify or attenuate the transmitted pulse, so fixture resonance verification is recommended.
Shock Condition Parameters
The classical half-sine pulse is the most common waveform, though trapezoidal and final-peak sawtooth pulses are also permitted under IEC 60068-2-27. Typical severity levels include:
- 15 g peak acceleration with an 11 ms pulse duration, common for general industrial and consumer equipment
- 30 g with an 18 ms duration, frequently specified for ground-mounted electronics in transportation environments
- 50 g and above with shorter durations, specified for aerospace, military, and severe automotive applications per ISO 16750-3
- Shocks applied in three mutually perpendicular axes and in both directions, commonly three consecutive shocks per axis for a total of 18 pulses
Electrical Loading During Shock
While the shock sequence runs, the specimen is continuously energized at its rated voltage or rated power dissipation through a monitored supply circuit. Current and voltage monitoring during the pulses allows detection of transient interruptions, intermittent conduction, or breakdown events that occur at the instant of impact, which is precisely the failure signature this test is designed to capture.
Recovery, Final Measurement, and Judgment
After the final shock, samples are allowed to recover under standard atmospheric conditions, then remeasured using the same parameters and methods as the initial measurement. The sample passes if it shows no visible damage, no open or short circuit, no hazardous event under load, and parameter drift within the tolerance band defined by the governing product specification. A test report issued by an accredited third-party laboratory documents the pulse waveform, achieved acceleration and duration, axis-by-axis shock counts, loading conditions, and all measured results.
Applications
Power durability testing under mechanical shock supports reliability qualification across a wide range of industries:
- Automotive electronics: engine control units, onboard chargers, battery management systems, and lightning protection components qualified to ISO 16750 and GB/T 28046 shock profiles
- Electric vehicle charging infrastructure: varistor and relay modules that must resist transport and installation shocks while energized
- Rail transit and heavy equipment: control cabinets and trackside power devices exposed to coupling shocks and impacts
- Renewable energy: surge protection in photovoltaic inverters, combiner boxes, and wind turbine control systems
- Industrial automation: drives, PLC I/O modules, and power supplies in shock-prone factory environments
- Aerospace and defense: avionics and power distribution units requiring combined shock and load verification per MIL-STD-style programs
- Telecommunications: base station power protection and remote outdoor cabinets subject to transport and service shocks
FAQ
Why apply electrical load during a mechanical shock test instead of testing shock alone?
Shock alone only reveals structural damage. When voltage or power is present, a shock-induced micro-crack or loose internal connection can immediately conduct, arc, or overheat, producing failures that remain hidden in an unpowered test. The combined condition reproduces the actual risk scenario in which energized equipment experiences impact.
Which standards govern this test?
The shock excitation is normally generated per IEC 60068-2-27 or GB/T 2423.5, with automotive severities drawn from ISO 16750-3 or GB/T 28046. Acceptance limits come from component or equipment standards such as IEC 61051-2, GB/T 10193, IEC 60384, IEC 61643, and UL 1449, depending on the product type.
What are typical pass criteria?
Common criteria include no visible cracking or breakage, no open or short circuit, no smoke or flame under load, a varistor voltage or resistance change within ±10 percent of the initial value, leakage current and insulation resistance within specification, and dielectric withstand verified after the shock sequence.
How many shocks and directions are required?
Most specifications require three shocks in each of six directions, corresponding to both polarities of three orthogonal axes, for 18 shocks in total, although severity and count vary by product standard and application environment.
Can this test be combined with other environmental stresses?
Yes. Sequential programs often add vibration per IEC 60068-2-6, temperature cycling, damp heat, and surge current endurance, allowing accredited third-party laboratories to build a complete reliability profile demonstrating long-term robustness of the component under combined mechanical, climatic, and electrical stresses.
