Mixed flowing gas (MFG) is a type of laboratory environmental testing for products, particularly electronics, to evaluate resistance to corrosion due to gases in the atmosphere. Mixed Flowing Gas (MFG) test is a laboratory test in which the temperature (°C), relative humidity (%RH), concentration of gaseous pollutants (in parts per billion, ppb or parts per million ppm level), and other critical variables (such as volume exchange rate and airflow rate) are carefully defined, monitored and controlled. The purpose of this test is to simulate corrosion phenomenon due to atmospheric exposure. The electronic product is exposed to gases such as chlorine, hydrogen sulfide, sulfide, nitrogen dioxide and sulfur dioxide at levels in the ppb range, in a controlled environmental chamber. Test samples that have been exposed to MFG testing have ranged from bare metal surfaces, to electrical connectors, and to complete assemblies. In regards to noble metal plated connector applications, MFG testing has been widely accepted as a qualification test method to evaluate the performance of these connectors. With regard to electrical and electronic applications, MFG testing has been widely accepted as a qualification test method to evaluate performance in the presence of environmental pollutants. The MFG exposures are generally used in conjunction with procedures which evaluate contact or connector electrical performance, such as measurement of electrical contact resistance before and after MFG exposure.
With regard to noble metal plated connector applications, MFG testing has been widely accepted as a qualification test method for evaluating the performance of connectors.
Matergenics MFG testing chamber attributes:
In addition to make-up air and water vapor, three or four corrosive gases are typically used. These pre-diluted gases are fed through mass flow meters into amixing chamber prior to introduction into the MFG exposure chamber. The concentration of each gas can be controlled to the part per billion levels usingthese mass flow meters. The gases used in the test are chlorine (Cl2), hydrogen sulfide (H2S), sulfur dioxide (SO2), and nitrogen dioxide (NO2).
All of the gases have natural and man-made sources. Different gaseous pollutants dominate in different field environments. The concentrations of the corrosivegas species can range up to 2 parts per million (ppm) each, or 2000 parts per billion. The relative humidity of the gas mixture is usually maintained between70 – 75%, sometimes as high as 95%, and the temperature between 25 – 40° C (77 – 104° F). The duration of the test is variable, but is usually a maximum of 504=]hours or 21 days.
Several general and industry-specific standards are available for mixed flowing gas testing methods. General standards include the following:
Some industry-specific standards we commonly test to include:
Since the MFG is an accelerated testing method, the determination of acceleration factor would be helpful to understand the durability or reliabilityof the device under test. In other words, if samples can survive a certain number of days in the testing chamber, it would be very useful to approximatelyestimate how many years it can last without corrosion problems in the field.
A correlation has been drawn between accelerated test exposed and long-term field exposed samples and components in the MFG test methods developed by Battelle. This correlation provides an acceleration of 2 days in the MFG chamber for 1 year in the field. Thus, a 14- day exposure test would be equivalent to 7 years in service.
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