Test chambers electronic devices

Bias is frequently added for testing of electronic devices, printed wiring boards, and assemblies of electronic equipment. The 85°C, 85 % RH, bias test has been the predominant one in electronics for many years [8], While it sometimes misses failure mechanisms that later occur in the field, it also finds many weak points in new products. It is especially useful for quality control of seasoned devices for which long-term reliability is known to be high if the product passes this test. There are many commercial suppliers of temperature/humidity/bias test chambers and software is widely available to automate the operation, data collection, and data interpretation. Attention to data management is mandatory when hundreds of devices are tested simultaneously. This is frequently required in electronics to obtain sufficient data to make statistically valid predictions of lifetime and failure rate under use conditions. 

Testing of Electronic Office Equipment This is a relatively new application of chamber testing and mainly applied to laser printers and hardcopy devices. In contrast to the testing of building products the available time frame is relatively short because a printing event normally proceeds within ten minutes. VOCs, ozone and particles are typically measured (see also Chapter 17). 

With the aid of emission test chamber measurements (see Chapter 5) emissions from electronic devices can be determined without any environmental influences affecting results. Such investigations aim at determining device-specific emission rates under standardized environmental conditions. Using these emission rates it is possible to make comparisons between the emission characteristics of different devices not only qualitatively (the composition of the emissions) but also quanti-... 

After switching on (pre-operating phase), the emissions of the device increase and under the boundary conditions of the test (air exchange rate) an equilibrium concentration Cpre establishes on top of the background concentration Cbg of the emission test chamber. During the operating phase there occur the emissions from consumables and heated electronic components. Once the operation has... 

Wensing, M., Kummer, T., Riemann, A. and Schwampe, W. (2002a) Emissions from electronic devices examination of computer monitors and laser printers in a 1 m3 emission test chamber. Proceedings of the 9th International Conference on Indoor Air and Climate, Monterey, Vol. 2, pp. 554-9. 

In the second test (ASTM D-5901, IP 434), an automated optical method is used for the temperature range to -70°C (-94°F). In this method, a 25-min portion of the fuel is placed in a test chamber that is cooled while continuously being stirred and monitored by an optical system. The temperature of the specimen is measured with an electronic measuring device, and the temperatures when crystals first appear and then, on warming, disappear are recorded. 

Braungart et al. (1997) have also investigated emissions from 11 electronic devices in their desiccator. All products were operated during or immediately before the test. Unit-specific emission rates ranged from 5.9 pg/h (cellular phone) to 206 pg/h (electric shaver). Emission rates of 7 products were below 27 pg/h. Typical VOCs detected in the chamber air were aliphatic hydrocarbons (C10-C18), aromatic hydrocarbons (toluene, o-, m- and p-xylene, C3-/C4-benzenes), 2-ethyl-1-hexanol, BHT (2,6-di-tert- butyl-4-methylphenol) and cyclohexanone. One electric shaver emitted large amounts of methylnaphthalenes. Emission rates of single compounds were well below 10 pg/h apart from one case in which the emission of 23 pg/h naphthalene from an electric hair drier was measured. 

There are currently no standards tests for measuring the thermal expansion of plastics in ISO or in BS 2782. In ASTM, test method D696 [124] uses a relatively thick test piece, which is placed in a chamber whose temperature can be controlled. This is shown schematically in Fig. 23. The expansion of the sample is transmitted to a remote dial gauge via a quartz rod that has a very low expansion coefficient. This same technique is applied in modern thermomechanical analyzers (TMA). but the dial gauge is replaced by linear displacement transducers or other electronic devices capable of detecting smaller dimensional changes. In turn this allows thinner specimens to be tested and permits wider temperature ranges to be examined. There are developments wnthin the ISO to provide a standard for these types of instruments. 

Development of a suitable test chamber for evaluating the effects of submicron particles on indoor suifaces, including electronic equipment and devices, requires (1) the capability to produce suspended ionic particles that accurately simulate the composition and size distribution of airborne particles responsible for the observed effects (2) designing a chamber that combines continuous air-recirculation, filters out all background and once-through particles, and provides parallel airflow with miiform particle concentration over the flow cross section of the test area (3) fabrication and evaluation of suitable test samples or devices and... 

In both groups of tests described here, standard metal coupons should be included in each test to ensure that the test chamber is giving reproducible results. Copper coupons are a good standard because copper is commonly used in electronic devices, it is sensitive to most corrodents, and its oxide thickness is easily measured by coulometric reduction. 

Development of a suitable dry-deposition test chamber for evaluating the effects of submicron particles on indoor surfaces, including electronic equipment and devices, requires ... 

Before the regulating rod was used with its servo mechanism as a control device, experiments were devised to measure its response time. The test consisted in unbalancing the electronic system with an applied voltage (instead of an ion chamber signal) and measuring the time required for rebalancing The response time for the maximum unbalance was found to.be about 0.1 sec and is considered adequate for control of known MTR instabilities. 

Following particle deposition, the test specimens should be evaluated in a temperature/humidity environmental chamber. With electronic equipment, bias should be applied to the specimen as well, and the device or equipment assembly should imdeigo a foil series of functional tests. 

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