Mr Walton Sounds like your process was robust. The 'big issue' on which I would like to hear your opinion is if any of the reliability models were able to actually indicate relative lifetimes and/or failure rates of systems or components for a defined environment.
Based on (anecdotal) experience from my last three employers, the models are not always useful, other than to meet contractual requirements. I agree with the process of grabing an AQL group, stress the crap out the units, test again, repeat until significant margin verified. It would seem that the market segments where EMI problems would cause the most problems and be made most public, aviation and medical, should be the least likely to fail. This equipment is supposed to be subject to more stringent periodic maintenance and calibration. Brian From: [email protected] [mailto:[email protected]]On Behalf Of Derek Walton Sent: Tuesday, June 15, 2010 1:54 PM To: Mark Schmidt Cc: [email protected]; [email protected] Subject: Re: [PSES] EMC Performance Changing With Age Of Product Hi All, just throwing in my 10 cents from when I worked for an automotive component manufacturer. Contary to what a so called expert has written recently, we were required to test the stuffing out of out parts. Specifically: We tested 5 parts from a sampled lot of 60. Before we began the EMI testing, our 5 parts were sent through some of the environmental tests to simulate product lifetime. The goal was to age the parts.... The very first test we did was ESD, to wicked levels including the pins. This was to simulate being installed in dry climates with no protective measures. The after sales market was seen as the most severe requirements. Some of the ceramic caps we initially used showed ESD induced cracks and electromigration. Our tests included 200 /m testing up to 18 GHz. While this may not be truly representative of lifetime testing, it was recognizing that it was important. Cheers, Derek Walton L F Research On 6/15/2010 2:10 PM, Mark Schmidt wrote: Just throwing this out there - how about Safety and EOL (End of Life). Let’s see quarterly inspection. Recertification (CB SCHEME) certs every three years, possible re-evaluation even though nothing has changed. More money spent. What’s the difference between this and EMC? Maybe I am missing something. In many cases the potential for EMC profile changes are greater due to the newer technologies and obsolescence of digital components. Yet no need to control EMC performance with the exception of the good honest integrity of most Regulatory Compliance (EMC) personnel/departments. Why is it different for Safety? Safety people have just as much integrity? Thoughts? Regards, Mark From: [email protected] [mailto:[email protected]] On Behalf Of [email protected] Sent: Tuesday, June 15, 2010 1:08 PM To: [email protected] Subject: Re: [PSES] EMC Performance Changing With Age Of Product Even if it were found necessary to control EMC performance of a product over its functional lifetime, I don't see how that could be done in practice. If it were common place that older electronic products became a RF nuisance, surely they would be evidence by an abundance of complaints to the authorities. Electrolytic capacitors and solder or mechanical connections do fail over time, but I suggest when they do the device likely also fails to function and is taken out of service. The apparent lack of legal control of EMC of products over their service life may simply indicate that none is warranted. _______________________________________ _____________________________________________ Ralph McDiarmid | Schneider Electric | Renewable Energies Business | CANADA | Compliance Engineer From: John Woodgate <[email protected]> To: [email protected] List-Post: [email protected] List-Post: [email protected] List-Post: [email protected] Date: 06/15/2010 03:44 AM Subject: Re: [PSES] EMC Performance Changing With Age Of Product In message <[email protected]>, dated Tue, 15 Jun 2010, "Pawson, James" <[email protected]> writes: >EMC performance of a product is likely to vary with age as the physical >characteristics change e.g. caps dry out, metal junctions oxidise, etc. > >Obviously the product is designed with the intention of consistent >compliance over the life of the product, but are there any requirements >or guidance relating to preventing or controlling this change in EMC >performance over time? Americas or Europe? I don't want to comment on the Americas position. For Europe, there seems to be an on-going problem that no-one wants to resolve, at least in some countries. For example, in UK, the Wireless Telegraphy Acts (WTA) used to apply legal controls to sources of interference, regardless of the age of the product or anything else. When the (second) EMC Directive was introduced, applying to products in general, not a specific range, those parts of the WTA seem to have been repealed. However, the EMC Directive applies requirements to *manufacturers (and/or their agents)* only. It isn't helpful to ask whether the Directive applies to newly-sold products or throughout their life. The requirements for manufacturers can only possibly apply *while the product is under the manufacturer's control*. It is reasonable to hold that the manufacturer must not neglect the reliability of any parts that affect EMC, but it is not possible to ensure that a given part will not fail very early in life. It is also not possible for the manufacturer to control what a user might do to or with the product (e.g. just connect a signal generator to an antenna and modulate it with audio). So effectively there appears to be no legal control in UK of the EMC performance of products during their life, and the same applies to any other EU state that changed its legislation in the way the UK did. If anyone believes differently, please respond (politely). -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK I should be disillusioned, but it's not worth the effort. - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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