GB/T 2423.22-2012Environmental testing - Part 2: Test methods - Test N: Change of temperature (English PDF)

Foreword

This part is the 22nd part of the GB/T 2423 standard. The components of the GB/T 2423 standard are listed in the informative appendix NA. This part is drafted in accordance with the rules given in GB/T 1.1-2009. This part replaces GB/T 2423.22-2002 "Electrical and Electronic Products Environmental Test Part 2. Test Method Test N. Temperature "Changes" and GB/T 2424.13-2002 "Electrical and Electronic Products Environmental Testing Part 2. Test Methods Temperature Change Test Guide". This part is mainly based on GB/T 2423.22-2002, which integrates part of GB/T 2424.13-2002 with GB/T 2423.22- In.2002, compared with GB/T 2424.13-2002, the main technical changes and editorial changes are as follows:

--- Test Na and test Nb, remove the relevant requirements for absolute humidity, tank wall temperature and air flow rate of the test chamber (see 7.2.1, 8.2.1);

--- Test Na, the provisions of the test chamber allowed to use a rapid temperature change rate are increased (see 7.2.1);

--- Test the severity of the Na and test Nb, increasing the "exposure duration" parameter (see 7.2.3, 8.2.3);

--- Test Na, deleted the "conversion time should be. (2 ~ 3) min, (20 ~ 30) s, < 10s" provisions, replaced by "conversion time T2 should not exceed 3 minutes" (see 7.2.5);

--- Test Nb, increased two preferred values of temperature change rate. (10 ± 2) K/min and (15 ± 3) K/min (see 8.2.3);

--- Test Nc, deleted two sets of standardized duration parameters;

--- The unit of temperature deviation replaces "°C" with "K";

--- Deleted the contents of

3.4.2 and Chapter 4 of GB/T 2424.13-2002;

--- Updated the contents of

3.3 of GB/T 2424.13-2002;

--- Updated all the diagrams;

--- Combine the contents of the test Na, the test Nb, and the test Nc "initial and final test" into a separate chapter 6;

1 Scope

GB/T 2423.22 specifies Test N, change of temperature, one of the most used environmental tests there is. It is not the same thing as a high or low temperature test: what it looks for is the damage done by the change itself, the differential expansion between materials in an assembly, the cracking of seals and solder joints, the condensation that forms when a cold item is brought into warm air. The standard defines the several variants of the test, the slow change at a specified rate, the rapid change with two chambers between which the specimen is transferred, the rapid change by immersion in liquid baths, and the specification of each: the temperature extremes, the rate of change, the dwell time at each extreme, the number of cycles, the transfer time, the conditions before and after the test and the recovery period, together with the requirements on the chambers and the mounting of the specimen and on the severities to be selected. It is aligned with IEC 60068-2-14. For a manufacturer, a specification writer or a test house in China, this is the referenced procedure.

4.6 Application limits for temperature change tests Within the test sample, the rate of temperature change depends on the thermal conductivity of the test sample material, the spatial distribution of the test sample heat capacity, and the test. Sample size. The temperature change at a point on the surface of the test sample generally follows an exponential law. Within the large test sample, such an alternating exponential rise And falling results in a periodic, approximately sinusoidal temperature change that is much lower than the magnitude of the alternating temperature applied. The heat transfer mechanism between the test sample and the conditioning medium in the tank or tank should be considered. The flowing liquid causes the surface of the test sample to be very high The rate of temperature change, while still air causes a very low rate of change. The two-tank method (test Nc) with water as the medium of regulation should be limited to sealed test samples or test samples with water-insensitive properties. Product, because the performance and characteristics of the test sample may be degraded by water immersion. In certain cases, such as test samples that are sensitive to water, it is necessary to stipulate the use of other liquids that are not water for testing. When designing this test During the inspection, it should be considered that the heat transfer characteristics of the liquid used may be different from water.

Note. The evaluation results obtained from Test Q. Seal (IEC 60068-2-17) may be helpful in evaluating the applicability of the two tank method.

2 Na test cycle

7.3 Recovery At the end of the test cycle, the test sample shall be held for a sufficient period of time under test standard atmospheric conditions to achieve temperature stability. For a particular type of test sample, the relevant specification can specify a specific recovery time.

7.4 Information to be given in the relevant specifications When the relevant specification contains this test, any of the following applicable details should be given.

a) type of test;

b) pretreatment;

c) initial detection;

d) installation and support details;

e) low temperature TA, high temperature TB;

f) exposure duration t1;

g) the number of cycles;

h) detection and/or load during the conditional test;

j) final detection;

k) Any deviation from the program agreed between the customer and the supplier.

3 Nb test cycle

8.3 recovery At the end of the test cycle, the test sample shall be held for a sufficient period of time under test standard atmospheric conditions to achieve temperature stability. For a particular type of test sample, the relevant specification can specify a specific recovery time.

8.4 Information to be given by the relevant specifications When the relevant specification contains this test, any of the following applicable details should be given.

a) type of test;

b) pretreatment;

c) initial detection;

d) installation and support details;

e) low temperature TA, high temperature TB;

f) exposure duration t1;

g) temperature change rate;

h) the number of cycles;

i) detection and/or load during conditional testing;

k) final detection;

l) Any deviation from the program agreed between the customer and the supplier.

4 General

4.1 Design of temperature change test Tests Na, Nb, and Nc include alternating high temperature and low temperature periods, and the conversion from one temperature to another is also well defined. From the laboratory ambient temperature to the first condition test temperature, then to the second condition test temperature, and then back to the laboratory ambient temperature The knot process is considered a test cycle.

4.2 Test parameters Test parameters include the following.

---Test room ambient temperature;

---high temperature;

---low temperature;

---Exposure duration;

--- Conversion time or rate of change;

---The number of test cycles. High temperature and low temperature refer to the ambient temperature, which is reached by most test samples, but the time is delayed. Only in exceptional cases can the high temperature or low temperature be specified for normal storage or outside the operating temperature range of the test sample. Since the number of sudden changes in temperature during a given time is greater than the number of occurrences of field conditions, the test is accelerated.

4.3 Purpose of the test and selection of test methods It is recommended to select the temperature change test as follows:

--- Evaluation of electrical properties under temperature changes, select test Nb;

--- Evaluation of mechanical properties under temperature changes, select test Nb;

---Evaluate the electrical performance after a specified number of rapid temperature changes, select test Na or test Nc;

---Evaluate whether the mechanical parts, materials and material combinations are suitable for withstanding rapid temperature changes, choose test Na or test Nc;

--- Evaluate whether the structure of the component is suitable for withstanding artificial stress, and choose test Na or test Nc. The temperature change test specified in GB/T 2423 is not used to evaluate the test sample to work under two extreme conditions of extreme temperature. Material stability or electrical performance differences.

5 Test Type Selection Guide

The severity of the test increases with temperature differences, rate of temperature change, and heat transfer to the test sample. Test N is preferably used as part of the sequence test. Some types of damage may not be obvious in the final test of test N, but only Will appear in subsequent tests (for example, Test Q. Seal, Test Fc. Vibration or Test Db. Alternating Damp Heat 1)). The temperature change test Nc (two-tank method) should not be used instead of the test Q (sealing). When specifying a temperature change test, attention should be paid to the characteristics of the test sample affected by temperature change conditions and their possible failure mechanisms. Reason. The initial test and the final test should be accordingly specified accordingly.

6 Initial detection and final detection

The requirements for initial and final testing of tests Na, Nb and Nc are as follows: 1) IEC 60068-2-14.2009 original text is "Test F. Vibration or Test D. Accelerated Damp Heat", but in the test method specified in IEC 60068, there is no "test" Test D. Accelerate damp heat, "Test F" is also divided into several methods, so it is still corrected here as IEC 60068-2-33.1971.

6.1 Initial detection The test samples shall be visually inspected and tested for electrical and mechanical properties in accordance with the relevant specifications.

6.2 Final inspection The test samples shall be visually inspected and tested for electrical and mechanical properties in accordance with the relevant specifications.

7 Test Na. specifies the rapid temperature change of the switching time

7.1 Test Overview This test determines the ability of components, equipment, or other products to withstand rapid changes in ambient temperature. Exposure time required to achieve this Depends on the nature of the test sample. The test sample shall be in a state of being unpackaged, not energized, ready for use, or otherwise specified by relevant specifications. The test sample is exposed to rapidly changing air or a suitable inert gas and is alternately exposed to high temperatures and low temperatures.

8 Test Nb. temperature change specifying the rate of change

8.1 Test Overview This test determines the tolerance and normal function of components, equipment or other products under ambient temperature changes. The test sample shall be in a state of being unpackaged, not energized, ready for use, or otherwise specified by relevant specifications. The test sample is exposed to temperature-changing air in the test chamber, the test chamber is maintained at the specified temperature value, and is controlled at a controlled rate. Chemical. The performance of the test sample can be monitored during the exposure.

9 Test Nc. rapid change of temperature in two-tank method

9.1 Test Overview This test determines the ability of components, equipment, or other products to withstand rapid temperature changes. This test procedure results in severe thermal shock and is suitable for glass-to-metal seals and similar test specimens. The test samples were alternately immersed in two tanks, one tank containing a low temperature TA liquid and one tank containing a high temperature TB liquid.