Graham Interesting, but is this not exactly what I have been saying since 1987? (Not blowing my trumpet, but simply stating how long it takes for a new idea to become more universally accepted). Brian Graham Naisbitt wrote: > Hello folks Here is a rather belated observational input on the recent > exchanges re SIR test results. I've been kinda pre-occupied with > urgent stuff. Anyhow, Jarmo Kiiski asked about the statistical > evaluation of data and I must point out that recent research data has > proven that existing flux characterisation tests are....well, here is > what has been put out by the British National Physical Research > Laboratory: "The present standard method for evaluating board > reliability and for flux qualification uses inappropriate test > conditions, and hence provides unrealistic test data often with > exceptionally high and misleading SIR values. This is the far reaching > conclusion of a landmark European collaborative programme led by NPL > which has now proposed a credible replacement test method"... (sic) > that is "using finer pitches on the test coupons, lower voltages > reflecting the actual device field strength and frequent monitoring to > detect transient effects such as dendrite formation, as the key > elements for a new test method. Another benefit is that test times can > be reduced from 7 days to 3 days." I believe that what Jarmo, Cara and > Amanda may be seeing/have seen, is "blips" in the occasional readings > they have taken which may actually be dendrites forming and/or > collapsing but largely missed because the measurements have been taken > too infrequently - or did I miss something? Brian certainly hits the > nail on the head by suggesting that the sample size is perhaps too > small - he hit a few other things too, I guess! My view is that your > measurements are insufficient to yield you the results you seek i.e. > choosing the right process material. I certainly could not contribute > to the debate on statistical interpretations. However, I would also > suggest that unless you make a test of all process materials on a > coupon that is more representative of your full production process you > will continue to get unreliable results from both your material tests > and the end product in the field. If its reliability matters, then you > really should take note. Regards Graham Naisbitt > [log in to unmask] > www.concoat.co.uk > Concoat Ltd > Alasan House, Albany Park > CAMBERLEY GU15 2PL UK > Tel: +44(0)1276691100 > Fax: +44(0)1276691227 ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8d ############################################################## 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 Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ##############################################################