The test in humid environment under temperature cycling condition is a dynamic test. Its fundamental difference from the steady-state test is that it cycles between two limits at high humidity. This test method is more commonly used to uncover or detect the following potential spoilage factors.
Determine the sensitivity of housing materials to thermal expansion, hygroscopicity, and dimensional stability.
The degree to which electrical connector system is affected by oxidation process in wet environment is determined by a limited method.
The extent to which contact surfaces are subject to abrasion (because moisture accelerates the oxidation process) during thermal cycling.
The process of oxidation in contact with material and wear debris or particles attached to its surface in damp conditions.
More stringent test conditions are commonly used for temperature/humidity testing
Condition 1 : testing under conditions that are controllable and shielded.
Conditions 2 , 3 : test conditions are not controlled but shielded.
The duration of the cycle test is usually random and the duration of the stay at high and low temperatures is approximately equal. If the equipment used in the test (DUT) has established a law of reaction to heat, the cycle may proceed at a faster rate. The limited requirement is that the DUT reaches thermal equilibrium in the expected time per cycle.
The traditional cycle used in special situations may be limited by the conditions required by the actual environment which is difficult to meet, because when the temperature is lower than 5℃ or higher than 100℃, the humidity does not exist, so the number of temperature rises may increase and the number of temperature drops will be reduced.
The method of durability testing may vary depending on the purpose of the test. Standard durability tests are as follows
1-48 to 96 hours: test in a steady wet environment.
2-240 hours: test in a humid environment under temperature cycling conditions.
3-500 to 1000 hours: test in a humid environment under temperature cycling conditions.
Among of them, test condition 1 is used for the evaluation of plastics, and test condition 2 is used for the evaluation of plastics and to determine whether there is a major catastrophic problem. Test condition 3 is used to determine whether the product under test is subject to mechanical failure over time (e.g. oxidation and/or abrasion corrosion in wet conditions). If it lasts less than 300 hours, it is thought that these temperature conditions can promote its failure over time.
Insulation resistance (IR) is used to evaluate the properties of plastic housing. Resistance (CRCR or LLCR) is used to evaluate the stability of contact surfaces and electrical properties.