Hi Gordon, "1. The process by which reliability distinctions get into standards. 2. The relative merits of making the distinctions on the basis of consequences vs. risk of failure." I'll try to explain from another side of Reliability and Product Safety. Reliability - Bellcore is a private set of standards (in other words they are not enforced by law) covering telecommunications equipment. Technical Reference TR-NWT-000332 "Reliability and Quality Generic Requirements". From this, through complicated math, failure rates of each component are used for the calculation of the entire assembly. FITs "Failure in Time" are used as well as MTBF "Mean Time Between Failures". A FIT = 1 is one failure in 10^9 hours. Typically say, a 1/4W carbon composition resistor has a FIT = 1. MTBF = (10^9 hours)/FITs. Unfortunately, MTBF doesn't say anything about MTTF "Mean Time to First Failure". These FIT or MTBF numbers are supplied by either Bellcore from charts for standard parts (such as the resistor above) or from the mfr using accelerated tests and calculations. No where in this document are any calculation based on any flux residue analysis nor processes related to boards. The construction of boards as such is covered in another Bellcore document TR-78 soon to be GR-78. The purpose of all this number chrunching is to give the Telco customer (like NYNEX or Ameritech to name some) a "reasonable" estimate that indicates how long a device will last. This is driven from the service provider handling 911 calls for example. Another would be simply comparison - one piece of equipment has a one failure in 100,000 hours, another one has one failure in 500,000 hours. Safety - All of the product safety testing I've had done for UL never addresses board construction, i.e. flux residue, etc. They do approve clearances between traces and CTI (Comparative Tracking Index) of the material used. Failure analysis is done at a first level stage - something shorts, something opens, something overheats. It is motivated by "end user" safety. How all these things get into the standards be they public standards or private standards is driven basically by us - the industry. If enough of us get on the bandwagon, we can pursuade ANSI or law itself to either rewrite an old or write a new standard. Think of ANSI as a clearing house for standards. If enough people have caused a fuss, they are charged with getting it written. They will turn toward an established organization for tha actual dirty work. You will see ANSI standards with a ANSI/xxxx. The "xxxx" is the actual commitee that performed the work. I don't know if I really answered your questions. Regards, Doug ************************************************************ ------------------------------------------------------------ The comments and opinions stated herein are mine alone, and do not reflect those of my employer. ------------------------------------------------------------ ************************************************************ *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************