Electronics Guide

High Temperature Testing

High temperature tests verify product operation and survival at elevated temperatures. Operating tests confirm functionality at the maximum rated temperature, typically with the product powered and executing its intended functions. Non-operating tests evaluate survival during storage or shipping at temperatures exceeding the operational range. Standard test temperatures follow preferred values such as 55, 70, 85, 100, and 125 degrees Celsius, with dwell times ranging from hours to days depending on thermal mass and test objectives.

IEC 60068-2-2 defines standard high temperature test procedures, while MIL-STD-810 Method 501 provides military-specific requirements. Test chambers must maintain temperature uniformity within specified tolerances, typically plus or minus 2 degrees Celsius, and rate of temperature change must be controlled to prevent thermal shock during transitions.

Low Temperature Testing

Low temperature testing reveals cold-related failure modes including material embrittlement, lubricant solidification, and reduced battery capacity. Products are conditioned at low temperature before operation to identify cold-start issues and verify performance across the specified temperature range. Standard test temperatures include minus 10, minus 25, minus 40, minus 55, and minus 65 degrees Celsius.

IEC 60068-2-1 establishes cold testing procedures recognized internationally. Condensation management becomes critical when testing below ambient dew point temperatures. Products may be bagged with desiccant or the test chamber atmosphere controlled to prevent moisture condensation that could mask actual cold-induced failures.

Temperature Cycling

Temperature cycling tests evaluate product response to repeated thermal transitions between high and low temperature extremes. These tests accelerate failures caused by differential expansion between materials with different coefficients of thermal expansion, particularly solder joint fatigue and delamination at material interfaces.

Key parameters include temperature extremes, dwell times at each extreme, transition rates, and total cycle count. Slow transitions allow thermal equilibrium and stress relaxation, while rapid transitions increase thermal gradients and stress levels. IEC 60068-2-14 defines temperature cycling procedures with various severity levels based on temperature range and cycle count.

Steady-State Humidity

Constant humidity exposure tests reveal product susceptibility to moisture absorption and corrosion under sustained humid conditions. Test conditions typically specify 85 or 95 percent relative humidity at elevated temperatures such as 40, 55, or 85 degrees Celsius. The classic 85/85 test, conducted at 85 degrees Celsius and 85 percent relative humidity, has become an industry standard for accelerated moisture testing.

IEC 60068-2-78 defines damp heat steady-state procedures. Test duration ranges from 48 hours to 1000 hours or longer depending on product requirements. Products may be tested powered or unpowered, with bias applied to accelerate electrochemical migration mechanisms.

Cyclic Humidity Testing

Cyclic humidity tests combine temperature and humidity variations to create condensation conditions that accelerate moisture-related failures. Temperature cycling causes breathing effects that draw humid air into enclosures, while temperature transitions below the dew point produce surface condensation.

IEC 60068-2-30 describes damp heat cyclic testing with temperature cycling between 25 and 55 degrees Celsius at high humidity. The test produces repeated condensation-evaporation cycles that stress seals, coatings, and internal surfaces. MIL-STD-810 Method 507 provides humidity testing procedures for military applications with various severity levels.

Highly Accelerated Stress Testing

Highly accelerated stress testing uses extreme humidity combined with pressure to accelerate moisture penetration into sealed packages. Pressure pot testing, also known as autoclave or HAST testing, exposes products to conditions such as 121 degrees Celsius, 100 percent relative humidity, and 2 atmospheres pressure. These extreme conditions dramatically accelerate moisture-related failures for rapid reliability assessment.

JEDEC JESD22-A110 defines HAST procedures for semiconductor devices. The biased version applies voltage stress during exposure to accelerate electrochemical mechanisms. HAST results require careful interpretation since the extreme conditions may introduce failure modes not representative of actual field exposure.

Liquid-to-Liquid Thermal Shock

Liquid thermal shock provides the fastest heat transfer rates, creating maximum thermal gradients within the product. Products transfer between hot and cold liquid baths, typically using inert fluorocarbon fluids to prevent electrical damage. Temperature extremes commonly range from minus 65 to plus 150 degrees Celsius with transfer times under 10 seconds.

IEC 60068-2-14 Test Na defines liquid-to-liquid thermal shock procedures. This severe test reveals weaknesses in solder joints, wire bonds, die attach, and other interconnections sensitive to rapid thermal expansion differentials. The test also identifies materials susceptible to thermal shock cracking.

Air-to-Air Thermal Shock

Air thermal shock uses heated and cooled air chambers with rapid product transfer between them. While heat transfer rates are lower than liquid methods, air thermal shock avoids fluid compatibility concerns and allows testing of products that cannot tolerate immersion. Transfer times of 1 minute or less maintain significant thermal shock severity.

Two-zone chambers use a basket mechanism to transfer products between adjacent hot and cold zones. Three-zone chambers add an ambient zone for more complex temperature profiles. Typical test ranges span minus 55 to plus 125 degrees Celsius with hundreds to thousands of cycles depending on reliability requirements.

Neutral Salt Spray

Neutral salt spray testing per ASTM B117 or IEC 60068-2-11 uses a solution pH between 6.5 and 7.2 at 35 degrees Celsius. Products are positioned in the spray chamber at angles that prevent solution pooling and ensure consistent exposure. Test durations range from 24 hours to several thousand hours depending on corrosion resistance requirements.

The test evaluates protective coatings, plating, and inherent corrosion resistance of materials. Results are typically evaluated based on visible corrosion, coating degradation, and functional performance after exposure. While widely used, neutral salt spray provides limited correlation to actual field corrosion since real environments involve additional factors including pollutants, temperature cycling, and wet-dry transitions.

Cyclic Corrosion Testing

Cyclic corrosion tests improve field correlation by combining salt spray with humidity cycling and drying periods. These complex profiles more realistically simulate actual environmental exposure. Standards including GMW14872 and SAE J2334 define cyclic corrosion procedures used extensively in automotive applications.

Cycles typically include salt spray exposure, high humidity periods, and ambient drying phases over 24-hour periods. The wet-dry cycling promotes different corrosion mechanisms than continuous salt spray, often producing corrosion products more representative of actual field failures.

Sinusoidal Vibration

Sinusoidal vibration testing applies single-frequency vibration across a range of frequencies to identify resonances and evaluate fatigue resistance. Sweep testing transitions through frequencies while monitoring product response, while dwell testing maintains specific frequencies to evaluate resonant response or accumulate fatigue damage.

IEC 60068-2-6 defines sinusoidal vibration procedures. Test parameters include frequency range, amplitude in terms of acceleration, displacement or velocity, sweep rate, and duration. Products must typically survive specified vibration levels without mechanical damage or performance degradation.

Random Vibration

Random vibration testing applies simultaneous excitation across a broad frequency spectrum, more realistically simulating actual transportation and operational environments. The power spectral density profile defines acceleration levels as a function of frequency, with overall levels expressed as root mean square acceleration.

IEC 60068-2-64 establishes random vibration procedures. Common profiles simulate road transportation, rail transport, aircraft cargo, and various operational environments. Random vibration excites all product resonances simultaneously, providing more efficient testing than swept sinusoidal methods for general durability evaluation.

Mechanical Shock

Mechanical shock testing evaluates product response to sudden acceleration pulses representing drops, impacts, and other transient events. Standard shock pulses include half-sine, trapezoidal, and sawtooth waveforms with specified amplitude and duration. Drop testing provides another form of shock testing using actual free-fall impacts.

IEC 60068-2-27 defines mechanical shock procedures with various severity levels. Test parameters include peak acceleration, pulse duration, pulse shape, and number of shocks applied in each axis. Products must survive specified shock levels without physical damage or permanent performance degradation.

Low Pressure Testing

Low pressure tests evaluate operation and survival at reduced atmospheric pressure. Standard test altitudes include 4,572 meters, 9,144 meters, 12,192 meters, and 21,336 meters for different application categories. IEC 60068-2-13 and MIL-STD-810 Method 500 define altitude testing procedures.

Reduced air density decreases convective cooling, potentially causing thermal failures not seen at sea level. Corona and arcing thresholds decrease at low pressure, affecting high voltage circuits. Sealed enclosures experience differential pressure that may cause leakage or structural deformation.

Rapid Decompression

Rapid decompression testing evaluates response to sudden pressure changes that occur during aircraft cabin pressure loss or explosive decompression scenarios. Products must survive the mechanical stress of rapid pressure change and continue operating at the resulting low pressure.

Test procedures specify initial and final pressures along with decompression time, typically a few seconds or less for severe tests. Sealed enclosures may experience significant stress during rapid decompression, and pressure relief features must function properly to prevent damage.

Blowing Dust

Blowing dust tests expose products to fine particles carried by air flow, simulating conditions in desert and industrial environments. IEC 60068-2-68 and MIL-STD-810 Method 510 define procedures using controlled particle sizes, concentrations, and air velocities. Standard test dust includes specified particle size distributions designed to challenge enclosure sealing.

Test severity depends on particle concentration, air velocity, and exposure duration. Products are evaluated for particle ingress, functional degradation, and ability to continue operating during and after exposure. Ingress protection ratings per IEC 60529 specify dust resistance requirements for various application categories.

Settling Dust

Settling dust tests evaluate effects of dust accumulation in low air movement environments. Particles settle on surfaces over extended periods, potentially blocking ventilation, insulating heat-generating components, and providing conductive paths when combined with moisture. Testing involves dust exposure in enclosed chambers allowing particle settling over days or weeks.

Thermal Effects

Solar heating tests expose products to simulated sunlight while monitoring temperature rise. Dark surfaces may reach temperatures well above ambient under solar loading. IEC 60068-2-5 defines solar radiation procedures including spectral content and intensity requirements. Lamps must reproduce the heating effect of actual sunlight, requiring proper spectral distribution from ultraviolet through infrared wavelengths.

Photodegradation

Ultraviolet exposure testing evaluates material degradation from UV radiation. Plastics, coatings, and other organic materials may experience discoloration, embrittlement, and property changes from UV exposure. Accelerated UV testing using high-intensity sources provides faster results but requires careful correlation to actual outdoor exposure.

Rain Testing

Rain tests evaluate water resistance under various precipitation intensities. IEC 60068-2-18 and MIL-STD-810 Method 506 define rain testing procedures ranging from dripping water to driving rain conditions. Test parameters include water delivery rate, drop size, wind velocity, and exposure duration.

Products may be tested in operating or non-operating states. Water intrusion is evaluated by visual inspection, weighing to detect absorbed water, and functional testing after exposure. Ingress protection ratings IP X1 through IP X6 specify increasingly severe rain and spray resistance requirements.

Immersion Testing

Immersion testing evaluates performance during and after water submersion. Temporary immersion tests per IPX7 involve submersion to specified depth for limited duration. Continuous immersion per IPX8 requires operation during extended submersion, with specific depth and duration defined by the manufacturer.

Test water may be fresh water or include salt or other contaminants depending on intended application. Water temperature and dissolved gas content can affect results. Products are typically evaluated for water ingress, electrical safety, and functional performance after immersion.

Icing Conditions

Ice accumulation tests expose products to conditions that produce ice coating, including freezing rain and supercooled water spray. IEC 60068-2-1 and MIL-STD-810 Method 521 address various icing scenarios. Products must survive ice loads without mechanical damage and may need to function during or after ice accumulation.

Frost Effects

Frost formation testing evaluates products that experience repeated freeze-thaw cycles in humid environments. Frost accumulates on cold surfaces when ambient humidity condenses and freezes. Testing involves thermal cycling across the freezing point under controlled humidity to evaluate frost effects on ventilation, seals, and surface functions.

Fungus Resistance

Fungus testing per IEC 60068-2-10 or MIL-STD-810 Method 508 exposes products to selected fungal species under conditions favorable for growth. Products are inoculated with fungal spores and incubated at high humidity and temperature for 28 days or longer. Evaluation assesses fungal growth extent and any resulting degradation.

Material selection significantly influences mold resistance. Many plastics, coatings, and other materials are inherently resistant or can be treated with fungicides. Products incorporating vulnerable materials require protective measures including conformal coatings and proper material treatment.

Intrinsic Safety Testing

Intrinsically safe equipment limits electrical energy to levels incapable of igniting specific explosive atmospheres. Testing per IEC 60079-11 verifies that even under fault conditions, the equipment cannot release sufficient energy for ignition. Tests include spark ignition testing in actual explosive mixtures to verify safety margins.

Explosion-Proof Testing

Explosion-proof enclosures contain any internal explosion and prevent flame propagation to the surrounding atmosphere. Testing per IEC 60079-1 verifies enclosure strength and flame path characteristics. Actual explosions are initiated inside test enclosures to verify containment and evaluate flame path performance.

Temperature-Altitude Combined Testing

Combined temperature-altitude testing evaluates products under conditions found at high altitude, where low pressure accompanies cold temperatures. MIL-STD-810 Method 520 defines combined temperature-altitude procedures. The interaction of thermal and pressure effects may reveal failures not seen in separate temperature or altitude testing.

Temperature-Humidity-Vibration Testing

Combined THV testing subjects products to simultaneous thermal, humidity, and vibration stresses. This severe combination reveals weaknesses in materials and structures under realistic stress combinations. Specialized test chambers with vibration capability enable combined testing without removing products between stress types.

HALT and HASS Applications

Highly accelerated life testing applies combined thermal cycling and vibration at extreme levels to rapidly identify design weaknesses. HALT testing pushes products beyond specification limits to find fundamental failure modes. Highly accelerated stress screening uses similar but less severe combined stresses in production to screen for latent defects.

Sequential versus Parallel Testing

Sequential testing applies multiple stresses to the same samples in a defined order. This approach reveals cumulative damage effects and requires fewer total samples but takes longer to complete. Parallel testing uses separate sample sets for different tests, providing faster results but potentially missing cumulative damage interactions.

Standard Test Sequences

Many industry standards define recommended test sequences optimized for specific product types. MIL-STD-810 provides tailoring guidance for selecting appropriate tests and sequences. RTCA DO-160 defines specific test sequences for airborne equipment. Following established sequences ensures thorough evaluation and regulatory acceptance.

Test Sample Allocation

Sample allocation strategies must balance statistical confidence with practical constraints. Minimum sample sizes depend on acceptable confidence levels and expected failure rates. Samples must be representative of production to ensure test results predict field performance. Sample conditioning and handling procedures maintain consistency between test units.

IEC 60068 Series

The IEC 60068 series forms the foundation of international environmental testing standards. Individual parts address specific environmental tests including cold, dry heat, damp heat, shock, vibration, and many others. These standards are adopted by national standards bodies worldwide and referenced by product standards across industries.

MIL-STD-810

MIL-STD-810 defines environmental engineering guidelines for military equipment. Beyond specific test procedures, the standard emphasizes tailoring test conditions to actual life cycle environments rather than applying generic test levels. This philosophy has influenced commercial testing practices and the standard is widely referenced outside military applications.

Industry-Specific Standards

Many industries maintain specialized environmental test standards addressing their unique requirements. RTCA DO-160 covers airborne equipment, ISO 16750 addresses road vehicle electronics, and Telcordia standards apply to telecommunications equipment. These standards reference foundational IEC and MIL-STD procedures while specifying application-specific test conditions and acceptance criteria.

Accreditation and Certification

Test laboratories performing environmental testing typically maintain accreditation per ISO 17025, demonstrating technical competence and quality management. Accreditation scope specifies the particular test methods each laboratory is qualified to perform. Products requiring third-party certification must be tested by appropriately accredited laboratories with witnessed or verified test data.