- Author
- Isaksson, S.
- Title
- Paverkan av rok pa elektronik. [Influence of Smoke on Electronic Circuits.]
- Coporate
- Swedish National Testing and Research Institute, Boras, Sweden
- Report
- SP Report 2000:19, 2000, 27 p.
- Distribution
- For more information contact: SP Swedish National Testing and Research Institute, Box 857, SE-501 15 BORAS, Sweden. Telephone: +46 33 16 50 00, Fax: +46 33 13 55 02, Email: info@sp.se Website: http://www.sp.se/eng/default.htm
- Keywords
- electrical circuitry | smoke | leakage | risk analysis | damage | electronic equipment
- Identifiers
- leakage currents; electronic circuits; electronic components; corrosivity
- Abstract
- ONLY ABSTRACT IN ENGLISH: The scope of this project has been a literature review of state-of-the-art on acute damage to energized electronic equipment influenced by a fire and possible protective measures. A fire produces smoke, heat and water etc. which all are detrimental to the function of electronic equipment. Corrosion and increased contact resistance cnuscd by soot and chlorides are well known problems. What has been more recently discovered are the acute failures that may be caused by leakage currents between leads or to ground. Studies have shown that modern digital technology is more sensitive to this type of influence than previous generations of electronics. The standardised classification of the environment for electronics does not include fire influence as a parameter. In general the environment is adjusted to suit the electronics, not the other way around. This makes the equipment more sensitive to abnormal situations such as for example a fire. Tests have shown that leakage currents can develop after a short time during a fire. The leakage can be either through the smoke in the gas phase or via deposits. The design of circuits does affect the sensitivity. Also, some types of components are more sensitive than others. Electric current and circuit impedance are also important factors. A general conclusion is that a shorter distance between leads increases the sensitivity. The electric fields around DC-leads has been shown to attract soot, creating carbon bridges and uneven soot depositions. It has been shown that choice of for example cable insulation material or the application of conformal coatings on circuits can affect smoke damage potential. The degree of protection varies though, implying that testing is needed. Traditional fire protection techniques can also be used, but the protection objectives must be chosen carefully. During one test intended to investigate smoke effects a broken circuit was observed at a moderately elevated temperature of 75°C. The fault was not possible to find when the circuit was examined later. The acceptance criteria for fire barriers is usually 180°C, i.e. a much higher temperature than most electronics can tolerate.