Needle Flame Test> is the main inspection item to test whether electronic products and materials are flame-resistant. Reproduce the actual situation, so as to evaluate the fire hazard of the product with simulation technology. This paper combines IEC 60695-11-5:2004 and IOS 5169.5-2008 to analyze the method requirements of needle flame test, equipment requirements, and confirmation methods of calibration results of main technical indicators, and summarizes Needle flame test chamber> >Precautions for the test process.
1 The main differences between the new and old versions of the standard>
1.1 Expansion of scope of application>
The IOS 5169.5-2008 edition standard expands the scope of application. The Needle Flame Test> not only takes into account that the internal components or components of the product will cause ignition due to failure and cause fire hazards, but also considers that the product’s exterior will also be affected Other equipment causes fire hazard due to overheating. Internal and external fire assessments through simulation techniques to more fully examine the reaction characteristics of complete product components or materials to heat and flame. 1.2 Requirements for Needle Flame Test Chamber>
1) For the needle flame test chamber: IOS 5169.5-1997 version standard has no specific requirements for the volume of the needle flame test chamber, but the new version of the standard clearly stipulates that the volume of the laboratory fume hood/test chamber should be at least 0.5m3 , the color of the inner surface of the box is dark, and the test should be carried out in a non-ventilated environment. The standard specifies the volume of the test chamber in order not to cause oxygen loss due to air convection during the test, which will affect the test results.
2) For burners and flames: The new version of the standard clearly stipulates the gas used by the burner, and can use alkanes or alkanes with a purity of not less than 95%. Butane is a flammable, colorless, easily liquefied gas that most needle flamesButane gas is often used as the experimental rate. At the same time, the requirements for the flame height during the needle hydrocarbon test shall be confirmed by means of the devices and procedures specified in Standard Note A.
1.3 Added device timer requirements>
In the new version of IOS 5169.5-2008, there is a new requirement for the timer of the equipment. The interval of the timer should not exceed 0.5s. There is no such requirement for the timer in the old version of the standard.
1.4 Requirements for new test samples>
In the new version of IOS 5169.5-2008, a description of the test sample is added, requiring that the test sample should be a complete device, component or part. Appropriate interception and dismantling may be carried out where necessary, ensuring that the test conditions do not differ significantly from those which exist during normal use of the product. This clause is added to more realistically simulate the fire effect when the product actually catches fire.
1.5 The evaluation of needle flame test results is revised>
How to determine whether the test sample can withstand the needle flame test, the new version of IOS5169.5-2008 standard is stricter than the old version. The new version of the standard stipulates that after the needle flame is removed, the flame or burning heat of the test sample and the surrounding parts will be extinguished within 30s, and at the same time, the burning of the bottom layer or packaging tissue paper caused by the dripping of the test sample due to burning is also not allowed , it can be judged that the test sample does not meet the requirements. This regulation is to prevent the fire hazard of secondary combustion caused by the flame of product dripping.
1.6 Added test report IOS 5169.5-2008>
The content of the test report has been added to the new version of the standard, mainly including: test sample type and description, preparation method, all pretreatments of the test sample, the number of test samples, severity level, the surface to be tested and the point where the needle flame is applied, for The specified underlayment to assess the effect of burning or glowing particles falling from the test sample, whether more than one point of the test is performed on the same test sample, the test results.
2. Needle flame test process and procedure in needle flame test chamber>
1) The needle flame test is generally carried out on 3 samples (unless otherwise specified).
2) The test sample should be placed in the position where it is most likely to ignite during normal use, and the application of the test flame or the extension of the flame should not be affected when the test sample is fixed. The test flame is applied to the surface part of the sample that is most likely to be affected by the flame. Contact the flame tip with the surface of the sample, adjust the flame height to 12mm+1mm, and the time for the flame temperature to rise from 100°C+2°C to 700°C+3°C is 23.5s+1.0s.
3) During the test period, the test sample will often drip into the combustion tube due to the melting produced by ignition, thusIt will block the cold air supply channel and eventually affect the test results. In order to avoid this situation, the new version of the standard stipulates that the burner can be tilted at an angle of 45°, and at the same time, the distance between the center of the top of the burner and the bottom of the rest of the sample should be kept at 8mm+1mm or Keep a distance of 5mm+1mm on the side.
4) Tightly wrap a smooth wooden board with a thickness of about 10mm with a layer of paper, and place it 200mm+5mm below the test sample to which the needle flame is applied. 5) After the flame temperature reaches, start the test switch to conduct the test, observe the test sample, surrounding parts and the laying layer, and record the test flame
The duration of burning (tb) from the moment of removal to the complete extinguishment of the flame and the test sample, specified sub-layer or nearby parts do not see the burning phenomenon.
3. Method for confirming equipment calibration results>
The main performance parameters of needle flame test equipment include box size, burner size and inclination angle, timer, flame height, and temperature calibration.
1) Box size. There are clear regulations on the volume of the test chamber. The volume of the test chamber should not be less than 0.5m3. The test chamber should be dark enough. In case of disputes, the light with an illumination of 20Lux should be used to facilitate the experimenters to more accurately measure the flame height. Make adjustments and observe how the sample burns.
2) Burner size and inclination angle. Use a needle gauge to measure the aperture of the burner. The aperture of the tube is required to be 0.5mm±0.1mm. Use a vernier caliper to measure the length and outer diameter of the burner tube. It is required that the length ≥ 35mm and the outer diameter ≤ 0.9mm to meet the requirements. Use a universal angle ruler to measure the inclination angle of the burner. The standard stipulates that the burner can be inclined 45° from the vertical to prevent materials from falling into the combustion tube, so the inclination angle of the burner should reach 45° to meet the requirements.
3) Timer. Use an electronic stopwatch to calibrate the time point of applying flame, the time point of continuous flame and the time point of heating up, and the error of the timer should be ±0.5s, which meets the standard requirements.
4) Flame height. During the needle flame test, a vernier caliper can be used to measure the flame height, and a height of 12mm±1mm meets the standard requirements.
5) Temperature calibration. The new standard stipulates that the material of the temperature-sensitive copper block for the flame confirmation test is: CU-ETP UNS C11000, the diameter of the copper block is 4mm±0.01mm, and the mass is 0.58g±0.01g. The standard clearly stipulates the requirements for copper blocks, which is not only conducive to the repeatability and comparability of the test, but also conducive to the improvement of the accuracy of the test results. After inserting the thermocouple for temperature measurement to the full depth of the hole, squeeze the copper block to fix the thermocouple, but do not damage the thermocouple, put it into the heating pot, set 100°C and 700°C respectively, and read the temperature on the thermometer for three times Display value, take the average value as the actual display value of temperature, when the temperature test results are at 100°C+5°C and 700°C+3°C, it is considered valid
4. During the needle flame testPrecautions>
1) The test equipment should meet the volume requirements of IOS 5169.5-2008 standard, and the door of the test chamber should be locked during the test to avoid the loss of oxygen caused by air circulation, which will affect the test results.
2) There are requirements for the gas supplied to the burner. When the gas source changes, it will inevitably affect the flame temperature. Therefore, the flame test must be reconfirmed when the gas source is changed.
3) Before the test, the test samples and the used bottom layer (wooden board and silk paper) should be pretreated according to the temperature and mixing degree specified in the standard. Generally, it is required to be placed in the environment for at least 24 hours.
4) When it is required to conduct multi-point tests on the same sample, it is necessary to ensure that the deterioration caused by previous tests will not affect the test results to be carried out.
5) Pay attention to keep the inside of the equipment clean, and clean it in time after the test; check the pinhole of the burner before each test to avoid being blocked by molten droplets, which will affect the full combustion of the flame.
>Needle flame test is an important test item to test the fire hazard of electrical and electronic products and their materials. Inspectors must have a deep understanding of the standards, understand the differences between the old and new standards, and master the operation methods proficiently to avoid and reduce the impact as much as possible Factors of test results, thereby improving the accuracy of needle flame test conclusions. This will not only help to improve the quality of the company's products, but also help to effectively control the company's costs, thereby more effectively improving the overall quality of electrical and electronic products.