GB/T 2424.11-1982 Basic environmental testing procedures for electrical and electronic products - Guidelines for sulfur dioxide testing of contact points and connectors
Some standard content:
National Standard of the People's Republic of China
Basic environmental testing procedures for electric and electronic productsGuidance for sulphur dioxide testforcontacts and connections
UDC 621.3
GB 2424.11—82
The good performance of contacts and connections during their expected life depends on many parameters, some of which are determined by their design (such as type, material, force, etc.) and others by the environment that affects them. Considering the impact of the environment, special attention should be paid to the pollutants contained in the atmosphere (usually in small amounts). Sulfur dioxide is one of the most important pollutants in urban and industrial atmospheres. 2 Sulfur dioxide in the atmosphere
Atmospheric corrosion of metals is usually caused by humidity and pollutants in the atmosphere. One of the main sources of pollutants is the combustion products of mineral fuels. The corrosive components of these combustion products are mostly sulfur dioxide (SO,). Very low concentrations of sulfur trioxide (SO), nitrogen and chlorine oxides can also be detected.
Table 1, Table 2, Table 3 lists the concentration of sulfur dioxide in the atmosphere of cities and industrial areas, which is generally 1 to 100 ppb (1 ppb is 10-9 volume ratio), and its peak value is equal to or greater than 1 Ppm (1 ppm = 10-6 volume ratio) in some local areas. In humid atmosphere, sulfur dioxide corrodes all metals except precious metals and silver, and has a significant impact on the performance of temporary contact points. In some cases, the accumulation of corrosion products hinders the contact between metals, causing the contact point to open. Table 1 Sulfur dioxide concentration in the atmosphere of Shanghai area Sulfur dioxide concentration in the atmosphere
Average value
mg/m3
Industrial area
Commercial and transportation area
Residential area
Clean area
Issued by National Bureau of Standards on September 23, 1982
mg/m3
Implemented from June 1, 1983
New York City office building
New Jersey chemical plant
New Jersey refinery
Los Angeles office building
Tractor foundry
Yala Paqiao Papermaking!
Total number of observation days
Average total concentration
Monthly average maximum concentration
Daily average maximum concentration
Hourly average maximum concentration
30-minute
Average concentration at individual monitoring stations
One-day
Concentration at individual monitoring stations>0.14ppm
Ratio of concentration in winter and summer
*Urban area.
GB 2424.11-82
Table 2 Sulfur monoxide concentration in the atmosphere of six locations Sulfur dioxide concentration in the atmosphere (ppb)
Average value
Day × monitoring station
ppb (volume)
ppb (volume)
ppb (volume)
ppb (volume)
Venice, Italy SO, pollutant data
Normalized to one year
Normalized to one year
Number of observations
|Typical mixed area dominated by cities.
*Mixed area dominated by industry.
**Industrial area.
4 ****
3 Test purpose and scope of application
3.1 Types of contacts and connectors
GB 2424.11--82
This test is specifically for fixed-type contacts and connectors (except for fusion welding and welding). It is helpful to briefly describe these types of contacts and connectors.
Contact points and connectors can be divided into two types: permanent or temporary. In both types, the metal surfaces are bonded together by the outside.
The external force of permanent connectors is very large, which often causes permanent deformation of the metal and may even cause partial welding. Such connectors must not be disconnected during their service life. Permanent connections include wrapping and wrapping. Temporary connectors have a relatively light force on the contact metal. Naturally, these connectors can be connected or disconnected many times during their service life. Temporary connectors include connectors, switches, and relays. In temporary connectors, the metals in contact are sometimes referred to as contact points. The contact points or contact surfaces of temporary connections can be made of various metals depending on the load and application. Most metals except precious metals are subject to atmospheric corrosion. When the contact material corrodes, the contact resistance increases. The widespread use of precious metal contacts is expensive, so in many applications, precious metal alloys or precious metal and alloy coatings on the base metal are usually used as contact materials.
For permanent connections, precious metals are usually not used. General corrosion of the surface caused by sulfur dioxide is expected. In properly designed and manufactured wrapping or wrapping connections, no corrosion occurs between cold welding and high-voltage contact surfaces. However, when the connection is made very tight or the connection is weakened due to temperature cycling, corrosive gases will penetrate these contact surfaces, resulting in an increase in contact resistance. 3.2 Test Purpose bzxZ.net
This test is used to study the following:
a. The effect of sulfur oxide pollution on the contact resistance of precious metal* or precious metal coating contact points and connections. b. The effectiveness of wrapping and wrapping.
This test can be used for acceptance testing of parts or equipment finalized by the manufacturer, or as a comparative test for selecting materials, process and design (see Chapter 8). In the acceptance test, the corresponding aging test precedes: sulfur dioxide test (mechanical endurance test to wear the contact surface, thermal cycle test). The main basis for judging their performance in a "sulfur dioxide atmosphere" is the increase in contact resistance. 4 Test parameters
The main parameters of the test are:
a. Sulfur dioxide (SO2) concentration:
b. Relative humidity;
c. Temperature;
Flow rate;
Test duration.
4.1 Sulfur dioxide concentration
Based on a lot of experience and several years of testing, 25ppm was selected from many recommended concentrations. This concentration is sufficient to produce a reasonable acceleration effect on the test and is also =The corrosion mechanism in use shall not be altered. Small amounts of sulfur trioxide are of minor importance.
To ensure stable conditions of sulfur dioxide concentration in the test chamber, regular checks shall be made throughout the test period. The sulfur dioxide concentration may be determined by any known method which measures the specified concentration with sufficient accuracy. 4.2 Relative humidity
* Silver and certain alloys are not considered noble metals for the purpose of this test, since the sulfur oxide test will produce valid results for these materials or contacts using them as transition layers, i.e. they are not corroded by sulfur dioxide, only their Other pollutants (such as hydrogen sulfide) are very corrosive to them. ** Mechanical durability test has fewer operation times and shorter aging time in acceptance test than in type test. GB2424.11--82
When the relative humidity is lower than 170%, almost no corrosion occurs. When the relative humidity exceeds 80%, the structure of the corrosive product changes significantly. When the relative humidity is 75%, the properties of the corrosion products are similar to the corrosion products formed naturally on site in most cases. It is necessary to ensure the relative humidity stability in the test chamber (same as the corrosive agent concentration) ). Regular checks should be made throughout the test period. Any known method can be used to determine the relative humidity, as long as it has sufficient accuracy to measure the specified allowable error. The ten-ball filter method is satisfactory for measuring relative humidity. The wet-bulb gauze should be changed frequently and the measuring instrument should be calibrated before and after each test. 4.3 Temperature
When the test temperature is higher than 30°C, there is a tendency to change the natural corrosion mechanism. When the temperature is lower, the test time is too long; 252°C is the most satisfactory moderate solution. In order to keep the relative humidity within the specified range, the temperature must be strictly controlled. 4.4 Flow rate
Use a continuous air flow through the test chamber. In this way, even if the sulfur oxide concentration is constant, it will not be reduced by the absorption of gas by the adsorption surface in the chamber. By moving the sample or stirring the gas in the chamber, the relative velocity between the test gas and the sample is within the specified range. This can avoid the local low concentration caused by the static gas pocket in the test chamber. Care must be taken to ensure that there is a gas flow around the sample in the chamber and that the chamber is not overloaded. In order to ensure that all samples are under the same test conditions during the entire test period, the above measures are necessary. 4.5 Test duration
The corrosion and test contact performance degradation caused by exposure to the test gas increase with the increase of exposure time. Although the relationship is not proportional, different test severity can be obtained by extending the exposure time. See Chapter 5 for details. 5 Test severity
In principle, the test conditions cannot be the only accelerating factor, because the acceleration depends on the structure, materials and service conditions of the specimen. This document is developed based on previous experience. General guidelines. This guideline will be improved as test experience accumulates. The following considerations should be made when evaluating test results or selecting the appropriate test duration for special occasions. If the contact surfaces are shielded or unsealed, and they are exposed to the circulating test gas!, then the corrosion rate is directly related to the concentration of the corrosive agent.
The vast majority of contacts inside actual specimens are usually partially sealed or shielded by the structure of the parts or components. The corrosion rate of such specimens is limited by the amount of contaminants that migrate from the atmosphere to the contacts (i.e., the concentration of sulfur dioxide close to the contact surface is lower than that around the specimen). This test has a smaller accelerating effect on unshielded contacts and connectors than on shielded or sealed ones. GB2423.19-81 recommends 4, 10 and 21 days as the preferred test severity levels, with 21 days for acceptance tests on precious metal or precious metal-plated contacts, and shorter durations of 4 and 10 days for comparison tests of new designs and different materials. The relevant standards should specify the test durations for selection, otherwise it shall be agreed upon by the relevant parties. 6 Test gas generation method
GB2423.19-81 recommends the following test gas generation method: Before the test gas is passed into the test chamber, sulfur dioxide, water vapor and air must be directly mixed to ensure a uniform mixture, so that the factory can obtain a uniform mixture. A small amount of "sulfur oxide" is mixed with a large amount of air, which may require graded mixing. GH2423.19-81 lists suitable devices for the method of generating test gas by electrons in the appendix. 7 Evaluation of test results
The main evaluation criteria of the test are the change in contact resistance, followed by the change in appearance. It must be pointed out that most metals and alloys except precious metals are corroded in this test, and this corrosion is expected. Therefore, their performance is judged based on the change in contact resistance. When the permanent connectors of the package and wrap are tested, the resistance of the tested contacts will change. If the joints are not airtight or poorly connected, the contact resistance will increase significantly. When the temporary connectors are tested, the contacts can be in contact or non-contact state (i.e. closed or open). The contact resistance of the contacting contacts (closed state) must be measured without interference after the test is completed. The contact resistance of the non-contacting contacts (open state) is measured at the first contact after the test is completed. 568
GB 2424.11—82
The measurement method of contact resistance shall be in accordance with the relevant standards. This test is mainly designed for contacts, which are used to transmit low current and low voltage signals. In order not to destroy the generated corrosion film, a low voltage and low current measurement method (maximum value is 20mV, 50mA) must be used.
8 Notes for testers and standard setters This test provides an accelerated means for evaluating the impact of sulfur dioxide-containing atmosphere on contact points and connectors. It is particularly suitable for use as a comparative test.
The relationship between the test results and the service life is affected by many factors. Only a rough estimate can be made based on the experience of many years of testing and the on-site working conditions. Therefore, it is not expected that this test will directly and accurately determine the actual service life of the test contact points and connectors used in any natural atmosphere. This test is not suitable as a "general corrosion test", that is, it cannot predict the corrosion effect of most corrosive agents in the atmospheric composition that are different from sulfur dioxide (compare GB2424.10-81 "General Guidelines for Accelerated Tests of Atmospheric Corrosion"). In addition, this test is very suitable for comparing the performance of mass-produced components with that of similar components. Eventually, people may find that this test has other uses.
Note: Except for Table 1, this standard is consistent with IEC68-2-42 "Guidelines for sulfur dioxide tests on contact points and connectors" (Draft). 569
A.1 This standard should be used in conjunction with the following standards: GB2424.11-82
Appendix A
(Supplement)
GB2421--81 "General rules for basic environmental testing procedures for electric and electronic products"
GB2422-81 "Terms and terms for basic environmental testing procedures for electric and electronic products" GB2423.19-81 "Basic environmental testing procedures for electric and electronic products - Test Kc: sulphur dioxide test method for contacts and connectors"
A.2 This standard is in conjunction with the International Electrotechnical Commission IEC Technical Committee 50, Subcommittee 50B, Central Office 217 Document 68--2-42 Standard "Guidelines for Test Kc: sulphur dioxide test for contacts and connectors" (Draft) [50B (Central Office) 217 Guidance to publication 68--2-42, Test Kc: sulphur dioxide test for contacts and connectors" (Draft) [50B (Central Office) 217 Guidance to publication 68--2-42, Test Kc: sulphur dioxide test for contacts and connectors Additional Notes:
This standard is proposed by the National Technical Committee for Environmental Conditions and Environmental Testing of Electrical and Electronic Products (hereinafter referred to as the Environmental Standardization Committee). This standard was drafted by the Fourth Working Group of the Environmental Standardization Committee. 57010-81 "General Guide for Accelerated Atmospheric Corrosion Testing"). In addition, this test is very suitable for comparing the performance of mass-produced components with that of similar components. Eventually, people may find that this test has other uses.
Note: Except for Table 1, this standard is consistent with IEC68-2-42 "Guide for sulfur dioxide testing of contacts and connectors" (draft). 569
A.1 This standard should be used in conjunction with the following standards: GB2424.11-82
Appendix A
(Supplement)
GB2421--81 "General rules for basic environmental testing procedures for electric and electronic products"
GB2422-81 "Terms and terms for basic environmental testing procedures for electric and electronic products" GB2423.19-81 "Basic environmental testing procedures for electric and electronic products - Test Kc: sulphur dioxide test method for contacts and connectors"
A.2 This standard is in conjunction with the International Electrotechnical Commission IEC Technical Committee 50, Subcommittee 50B, Central Office 217 Document 68--2-42 Standard "Guidelines for Test Kc: sulphur dioxide test for contacts and connectors" (Draft) [50B (Central Office) 217 Guidance to publication 68--2-42, Test Kc: sulphur dioxide test for contacts and connectors" (Draft) [50B (Central Office) 217 Guidance to publication 68--2-42, Test Kc: sulphur dioxide test for contacts and connectors Additional Notes:
This standard is proposed by the National Technical Committee for Environmental Conditions and Environmental Testing of Electrical and Electronic Products (hereinafter referred to as the Environmental Standardization Committee). This standard was drafted by the Fourth Working Group of the Environmental Standardization Committee. 57010-81 "General Guide for Accelerated Atmospheric Corrosion Testing"). In addition, this test is very suitable for comparing the performance of mass-produced components with that of similar components. Eventually, people may find that this test has other uses.
Note: Except for Table 1, this standard is consistent with IEC68-2-42 "Guide for sulfur dioxide testing of contacts and connectors" (draft). 569
A.1 This standard should be used in conjunction with the following standards: GB2424.11-82
Appendix A
(Supplement)
GB2421--81 "General rules for basic environmental testing procedures for electric and electronic products"
GB2422-81 "Terms and terms for basic environmental testing procedures for electric and electronic products" GB2423.19-81 "Basic environmental testing procedures for electric and electronic products - Test Kc: sulphur dioxide test method for contacts and connectors"
A.2 This standard is in conjunction with the International Electrotechnical Commission IEC Technical Committee 50, Subcommittee 50B, Central Office 217 Document 68--2-42 Standard "Guidelines for Test Kc: sulphur dioxide test for contacts and connectors" (Draft) [50B (Central Office) 217 Guidance to publication 68--2-42, Test Kc: sulphur dioxide test for contacts and connectors" (Draft) [50B (Central Office) 217 Guidance to publication 68--2-42, Test Kc: sulphur dioxide test for contacts and connectors Additional Notes:
This standard is proposed by the National Technical Committee for Environmental Conditions and Environmental Testing of Electrical and Electronic Products (hereinafter referred to as the Environmental Standardization Committee). This standard was drafted by the Fourth Working Group of the Environmental Standardization Committee. 570
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