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Last Guide to the Temperature Humidity Vibration Combined Test

Last Guide to the Temperature Humidity Vibration Combined Test You’ll Ever Need

Classification of Environmental Tests

Environmental tests are roughly divided into three categories:

  • Mechanical environmental test
  • Climate environmental test
  • Comprehensive environmental test

As shown in Figure 1.

 Figure 1 Classification of Environmental Tests

  1. The mechanical environmental stresses include: vibration, shock, collision, constant acceleration, noise;
  2. The comprehensive environmental stresses include: environmental factors that combine mechanical and climatic environments;
  3. The climate and environmental stresses include: temperature, humidity, low pressure, salt spray, rain, mold, solar radiation, dust;

It is well known that environmental stress can cause product failure. The technical information of a well-known foreign electronic equipment company clearly shows the relationship between environmental stress and failure and its related proportion. As shown in Figure 2, among the effects of various stresses, failures caused by temperature, humidity, and vibration environmental stresses account for 88% of all environmental stresses.

Figure 2 Proportion of Various Environmental Stresses in Failure

Relationship Between Temperature, Humidity, Vibration Stress & Failure

Relationship Between Temperature Stress & Failure

The data show that temperature stress is the most important factor causing product failure, as shown in Table 1.

Table 1 Main Types of Failure Caused by Temperature Stress

Lapse Environmental stress conditions Sensitive components & materials
classification Subdivision Reason Failure mode
High Temperature  

 

 

 

 

 

High Temperature Aging

Aging Tensile strength aging Insulation aging Temperature + Time Plastic, resin
Chemical Reaction Thermal decomposition Temperature Plastic, resin
Softening, melting, vaporizing, sublimation Distortion Temperature Metal, plastic, thermal fuse
High temperature oxidation Oxide layer formation Temperature + Time Connection point material
Thermal diffusion Lead break Temperature + Time Heterometallic connection
Heat build-up Remaining heat burning Combustion Heating + Drying + Time Wood material with vinyl and polyurethane paint
Migrate Electromigration Break lead Temperature + Current Tungsten, copper, aluminum (especially aluminum leads in integrated circuits)
Spread Metal Fatigue, damage Temperature + Stress +Time Springs, structural elements
Plastic Fatigue, damage Temperature + Stress + Time Springs, structural elements
Low Temperature Brittle at low temperatures Metal Damage Low Temperature Zinc, titanium, magnesium and their alloys
Plastic damage Low Temperature Low elasticity amorphous
 

Temperature Cycling or Thermal Shock

Expansion & contraction Different materials have different expansion coefficients Peeling, cracking Temperature + Times Paint coating
Mechanical displacement Electrical performance changes Temperature + Times Adjustable resistance, potentiometer
Different materials have different expansion coefficients Deformation of seals Temperature + Times Hermetically sealed container

Relationship Between Humidity Stress & Failure

Moisture is also one of the main environmental stresses that cause product failure.The product is in a humid environment, and the moisture absorbed by the material will cause expansion, decrease in strength, and change in performance, and the insulation material will cause reduction in electrical performance. The details are shown in Table 2.

Table 2 Main Types of Failure Caused by Humidity Stress

Lapse Environmental stress conditions Sensitive components & materials
Classification Reason Failure mode
Water vapor absorption or diffusion Diffusion Swell Humidity Components encapsulated, covered, or constructed using low crystallinity resin materials
Microburst Poor insulation performance and deliquescence
Corrosion Electrolytic corrosion Increased impedance Humidity + DC electric field Resistance, integrated circuit
Crack corrosion Solder joint cracking Humidity Solder joint
Stress corrosion Color changes Humidity Alloy
Migrate Ion migration Short circuit Humidity + DC electric field

 

Copper, lead, tin, zinc
Poor insulation performance Humidity + DC electric field + halogen ion Metals such as gold and platinum that migrate when coexisting with halogens
Mold Deterioration of insulation performance Temperature +Humidity Plastic material rubber material

Relationship Between Vibration Stress & Failure

The impact of vibration stress (vibration, shock, collision, constant acceleration, etc.) on the product is also one of the main factors causing product failure, as shown in Table 3.

Table 3 Main Types of Failure Caused by Vibration Stress

Lapse

Environmental stress conditions

Sensitive components and materials

Classification

Reason Failure mode

Resonance

Produce displacement Loose, separated Vibration + shock Material connection
Poor contact Vibration + shock Solder joint
Abrasion Vibration Material connection

Resonance, durable vibration

Strength Fatigue, deformation, bending Vibration + shock Metal structure
Cracking Vibration + shock Metal structures, plastic structures, cables and wires

Relationship Between Comprehensive Application of Three Kinds of Stress & Product Failure

Applying separate environmental stresses to the product can trigger product failure. Then applying 3 different environmental stresses to the product can easily achieve 3 to 5 times the acceleration effect. At the same time, by combining different environmental stresses, failures that cannot occur when individual stresses are applied can be stimulated.

Assume that X, Y, and Z are failure modes that occur when stress factors A, B, and C are applied. X, Y, Z, XY, YZ, and XZ modes appear under the combination of two stress factors. Then under the combined situation of the three stress factors, a new XYZ mode will appear. At the same time, X, Y, Z modes are also accelerated. In addition, the environment where the stress factors A, B, and C are comprehensively applied is closer to the product use environment than the environment where the stress factors are applied alone. Therefore, better results can be achieved through comprehensive environmental tests.

In the comprehensive experiment of simultaneous application of three kinds of stress: temperature, humidity, and vibration, from the mechanism of failure occurrence, the product undergoing temperature cycling expands and contracts due to the difference in the expansion coefficient of the material, and loosens at the joint. At this time, if humidity and moisture are applied, it will invade from the gap and reduce the friction coefficient of the joint and the joint. When vibration stress is applied, the resonance phenomenon of the product will occur with respect to a specific frequency. Through the repetitive processes of motion, moisture absorption, freezing, and resonance, the emergence of new failure modes (caused by the greatly accelerated single-factor failure mode and the combined effect of the three factors) becomes possible.

Figure 3 Mechanism of Failure Caused by Comprehensive Stress Application

Summary

Because the temperature, humidity, vibration three comprehensive test is very close to the product use environment test. And this test can very effectively provoke product failure problems. Therefore, in recent years, this test technology has been widely used in engineering.

Our company has this Temperature Humidity Vibration Combination Test Chamber, which meets the following standards:

  • IEC68-2-1 (GB2423.1-2008)
  • IEC68-2-2 (GB2423.2-2008)
  • IEC68-2-3 (GB2423.3-2006)
  • IEC68-2-30 (GB2423.4-2008)
  • IEC68-2-14 (GB2423.22-2008)
  • MIL-STD-810D (GJB150.3A-2009)

3 thoughts on “Last Guide to the Temperature Humidity Vibration Combined Test You’ll Ever Need

  1. Milton says:

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