GB 12305.2-1990 Test methods for metal coatings - Gold and gold alloy electroplated coatings - Part 2: Environmental testing GB12305.2-1990 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Metallic coatingswww.bzxz.net
Test methods for gold and gold alloy electroplating
Part 2 Environmental tests
Metallic coatings—Ist methods for electrodeposited gold and gold alloy coatings Pari 2: Environmental tests GB 12305.290
This standard is equivalent to the international standard $04524/2--1985 Test methods for metallic coatings, gold and gold alloy coatings—Part 1 Environmental tests.
1 Subject content and scope of application
This standard specifies the environmental test methods for gold and gold alloy coatings. This standard is applicable to simulated environmental tests on gold and gold alloy coatings used in engineering, decoration and protection. 2 Reference standards
GB2423.19 Basic environmental test procedures for electrical and electronic products Sulfur dioxide test for contacts and connectors GB4623.9 Electrical image test method for porosity of printed board coatings GB12305.3 Test method for metal coatings Gold and gold alloy coatings Part 2 Electrical image test for porosity 3 Overview
This standard has established three tests. Two of the tests are carried out in an atmosphere containing sulfur dioxide and one in an atmosphere containing nitric acid vapor.
The test results are related to the properties of the metal exposed at the discontinuity of the gold bond layer. The effect of various test methods on the coating depends on the properties of the bond layer itself and the content of its alloying elements. When selecting a test method, a method that can clearly expose the base metal or the bottom metal should be selected. For coatings for general purposes, the thickness of the bottom coating should be sufficient to protect the substrate from corrosion, and it is not necessary to consider testing the metal through the bottom coating. Under special conditions of use, special tests can be conducted through negotiation between the two parties. The porosity of the coating can be directly displayed by any of the methods in the electrical image test described in GB12305.3. However, in order to make the corrosion products produced in the parts showing the porosity more similar to the corrosion products produced under the conditions of use, the sample can usually be directly exposed to a moist atmosphere containing polluted gases or vapors, so that these gases can react with the bottom coating or the base metal through the pores of the gold layer. This method is more suitable for parts with complex shapes less than 100mm×100mm. Before the test, the sample should be degreased in 1,1,1-trifluoroethane gas or other appropriate solvents, and the scratched parts on the coating or the unplated parts on the base metal should be protected. 3.1 Engineering Application
Gold and gold alloy coatings for engineering use should have low contact resistance, good solderability and stability to large currents passing through the surface, and can maintain this performance during long-term storage or use
The properties of the corrosion products produced during the test are different from those formed in the actual use environment. If the correlation between the test results and the use conditions is not obtained in advance, these tests are not used to evaluate the electrical contact performance. 3.2 Decorative and protective applications
Approved by the State Administration of Technical Supervision on April 6, 1990 and implemented on October 1, 1991
G12305.2-90
The main requirements for decorative gold plating are: the appearance of the plating should remain unchanged when exposed to the environment for a long time 4 Sulfur dioxide exposure test
4.1 Scope of application
This test is applicable to gold plating on copper and nickel base layers: the effect on gold plating on silver substrates and silver magnetic layers is not obvious. : The test should be carried out in a fume hood.
4.2 Method overview
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Select a container that is easy to control the atmospheric composition. A known reagent is used in the container to produce sulfur dioxide. A bracket is placed in the container, and the sample is suspended on the bracket.
The test temperature and temperature range should be adapted to the test materials and test time, and can be agreed upon by both parties. To prevent local overheating or temperature fluctuations in the test space during the test, airflow and any high-altitude radiation should be avoided from affecting the test container. 4.3 Containers and Reagents
4.3.1 Test vessel A 10L glass desiccator or a polypropylene test vessel with a seal or valve. The sample holder is placed in the test vessel, and the holder is made of non-metallic materials such as glass or polyolefin that do not react to hydrogen sulfide. The sample can be hung with polypropylene fiber or corrugated glass hooks. 4.3.2 Sodium thiosulfate solution Prepare reagent grade sodium thiosulfate into a 200g/L solution. 4.3.3 Dilute sulfuric acid: Dilute 50mL of concentrated sulfuric acid (1.84) to 100mL with distilled water. 4.4 Test steps
Put 200mL of sodium thiosulfate solution (4.3.2) into the large culture towel in the test vessel. Then add 100 mL of dilute sulfuric acid (4.3.3) to the culture medium, place the sample in the container, close the container immediately, and shake gently to mix the two liquids thoroughly. The distance between the sample container and the liquid surface should be not less than 75 mm, and the distance between the sample container and the inner wall should be not less than 25 mm. After the test, the sample is taken out by the experimenter for inspection: two test cycles should be used: 24 h at 25°C and 2 h at 60°C.
5 Industrial atmosphere test
This test can be used to evaluate the effect of the atmosphere containing combustion products on the material when hydrocarbons containing sulphur are burned. It has been found that it is suitable for providing information on the performance changes of materials in polluted atmosphere on the basis of comparative tests. GB2423.19 provides the equipment and operating instructions required for the test.
In a test box with a capacity of 200 L, a probe device is installed to enable the sample to move in the test atmosphere at a speed of 11±3 mm/s. The test chamber contains 25±5cm/m* of sulfur dioxide, relative humidity is 70% to 80%, preferably around 75%, and the chamber temperature is maintained at 25±2℃. The gas flows in the test chamber, and the flow rate is required to replace the gas in the chamber 3 to 5 times per hour. The test gas can be generated by mixing the necessary gas components, or by burning propane, butane, or natural gas with carbon disulfide added. Then the combustion products are passed through air and steam to generate the gas. If the contact resistance change is measured, the gas is passed through the chamber. Contact resistance should be measured from the finished product before and after the test. 6 Nitric Acid Test
6.1: Equipment and Reagents
8.1.1 Test Container: The requirements for the test container are the same as those for the sulfur dioxide exposure test in the wood standard, but only glass containers and glass stands can be used. The volume of the container (in cm) should not be greater than 25 times the surface area of ​​nitric acid (in cm). It is not required to accurately control the filtration degree. The test temperature should be 23±3℃.
6.1.2 Oven: Control the temperature at 1253℃. 6. 1.3 Reagents, concentrated nitric acid 65%~71% (p=I, 101.12 island/mL) 6.2 Test steps
GB12305.29
Add 250 mL of concentrated nitric acid to a 10 L desiccator and cover the container. After 30 minutes, carefully lift the cover, put in the sample and cover it again. Generally, for gold plating on copper or copper-metal intermetallic, the test time is 60±10 minutes. If there are special requirements, it shall be agreed upon by the supplier and the buyer. After the test, take out the sample and put it in an oven at 125±3℃ for 30 minutes. min, then take out the sample and inspect the surface under a 10x magnifying glass. The corrosion products formed by the gold plating on nickel may be transparent, and it is recommended to check under lighting. For example, a parallel treatment with an inclination angle of less than 15° can be used, so that it is possible to see the corrosion products from the outside of the pores. After the test, the nitric acid in the instrument is discarded. Note that this experiment is not applicable to the gold layer on the substrate or silver bottom layer. Some gold coatings with high gold content, especially gold alloy coatings with a copper content of more than 10%, may have stress corrosion cracks that significantly increase the surface defects when conducting nitric acid tests. During the test, a partial vacuum may be generated in the test container. To solve this problem, a tetraethylene fluoride tube can be inserted or a valve can be installed. Do not pass it through the nitric acid test. The pressure is adjusted by heating the nitric acid solution in the container, which will cause a violent spray. The test should be carried out in a fume hood.
7 Test report
The test report should at least include the following contents: the relevant contents of this standard, including the terms of the specific test method used; the test results and the expression of the test results; h.
Abnormal band phenomena observed during the test; d.
Any operation not included in this standard and the referenced standards: other relevant information required by the requirements.
Additional remarks:
This standard was proposed by the Ministry of Machinery and Electronics Industry of the People's Republic of China. This standard is under the jurisdiction of the National Technical Committee for Standardization of Metallic and Non-metallic Micro-coatings. This standard was drafted by the Technology Research Institute of the Ministry of Machinery and Electronics Industry, and the main drafters of this standard were Han Shumei and Yue Jinying.
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