You could use the table in IPC-SM-785 which lists worst case use environments. Step outside that range for the class of product and you could call that harsh. I believe Engelmaier is a big proponent of this document. The work done with COTS (Commercial Off The Shelf) has some information also. I have a chart that shows temp-humidity curves for the U.S. , world, and mil specs. Glenn David Douthit <[log in to unmask]> Wrote: | | Technetters, | | I would like some expert opinions on what constitutes a "harsh | environment". | In order to stimulate some debate the following is one proposed | definition. | | "Due to the highly competitive nature of the electronics industry and | costs of coating the issue of whether coating is required or not can | become a hotly debated topic. The primary issue is "What is a harsh | environment?". | | The following general rules can be considered as the boundary line | condition for a "harsh environment". There are three minimum conditions | which must exist in the localized area of the circuitry at the same time | with or without power applied: | 1. A relative humidity of 60% or higher. | 2. Temperatures above 0 degrees C. | 3. The deposition of ionic contaminates on the circuitry surface which | will exceed 1.5ug | of NaCl or its' equivalent per square cm during the expected | lifetime of the product. | | Consideration of these conditions must also include shipping, storage, | and handling of the product. These conditions are a reference point and | exceptions are possible. Researching these environments are required to | determine if these conditions exist." | | Thank you for your time. | | D. A. Douthit | | ############################################################## | TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c | ############################################################## | To subscribe/unsubscribe, send a message to [log in to unmask] with following text in | the body: | To subscribe: SUBSCRIBE TECHNET <your full name> | To unsubscribe: SIGNOFF TECHNET | ############################################################## | Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional | information. | If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or | 847-509-9700 ext.5365 | ############################################################## | ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c ############################################################## To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TECHNET <your full name> To unsubscribe: SIGNOFF TECHNET ############################################################## Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information. If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or 847-509-9700 ext.5365 ##############################################################