Thermal shock test (gas):
There are two ways to achieve, one is manual conversion, which converts the product between a high temperature box and a low temperature box; the other is an impact test box, which realizes temperature conversion by opening and closing the circulating air door of the heating and cooling chamber or other similar means. The upper temperature limit and the lower temperature limit are the storage limit temperature values of the product. See the figure below for specific methods.
Thermal shock test (liquid):
This test is derived from IEC 60068-2-14 test method N: Nc in temperature changes. The realization method is a hanging basket, where the product is placed in the hanging basket and immersed in liquids of different temperatures as required. It applies to glass-metal seals and similar products, so this item will not be assessed in electrical products.
Difference and application analysis
Among the above two test items, it is recommended to use IEC 60068-2-14, Na for testing. This test item is an accelerated test product
test. The recommended number of cycles in the IEC 60068-2-14, Na and ISO 16750-4 cold and thermal shock tests is 5, which is too few in actual applications. It is recommended to use the parameters in Table 3.
Here to clarify that the number of cycles required for cold and heat shock in IEC 60068-2-14, ISO 16750-4, MIL-STD-810F and GJB150 are all within 5 cycles. The reason is that the three types of standards for this test It is defined as: to determine whether the equipment can withstand the rapid changes in the surrounding atmospheric temperature without physical damage or performance degradation. The simulated situation is: air transportation of products, air drop-off and other products transfer from different temperature areas. Therefore, in order to assess such conditions, the test is carried out as a sample storage test. During the test, the product does not work. The number of temperature shocks of the product is subject to the number of times the product will actually be used. This type of test item is a kind of product reliability .
From the above analysis, we can see that when implementing this standard for our automotive products, the parameters need to be changed because the simulation conditions we assess are different. The main variable parameters are: the number of cycles increases (because it is applied to automotive electrical products for accelerated aging test , So the number of cycles generally exceeds 100).
Analysis of important parameters
This test has several important parameters to consider: number of cycles, temperature conversion time, temperature holding time, temperature limit value (so the test is a storage type test, so its limit value is the storage limit temperature value). The reference parameter settings are shown in Table 3. The specific cycle number source is an empirical value calculated by the acceleration model, which will not be detailed in this article for the time being.