Dear Marcelo, Yes, it is possible to measure SIR under a flip chip. If the comb pattern you use is beneath a flip chip then any influences on the SIR across that comb pattern will be detected just as if it were a standard IPC or MIL coupon being measured in a more standard style of test. In fact we mount QFP's over our process validation test comb patterns to provide a contamination entrapment space and cleaning challenge. We think this makes it a better model for SMT process validation, and so your idea is not at all far fetched. It may take longer for moisture to penetrate to the comb pattern and lower the SIR (if this is what occurs) but then this reflects the real application. In terms of voltage, and the comb design the important factor is voltage gradient. You must look at the minimum track spacing (not so much the track width) that is present in your application and the maximum voltage that is likely to be applied across this space. From this you get the maximum field gradient (V/mm) for your application, and it is this field gradient that you should apply to your customised comb pattern. Thus the voltage will depend upon the spacing on the comb pattern you decide to use. By using the field gradient appropriate to your application you are less likely to promote failure mechanisms that would not be relevant. As an example on a B24 coupon (spacing 0.5mm) a bias voltage of 50V gives a field gradient of 100V/mm. In terms of using a bare board as a control, this is a very good idea, and you should put a control in the chamber and actually test simultaneously whenever you run a SIR test. This way any external and unwanted influences due to chamber failure, condensation etc. can be accounted for. Using an Auto-SIR(tm) unit you could take frequent readings (e.g. 128 test points, 10 minutes intervals) and monitor the SIR over the whole test period. You should try and stick to a standard to make your readings more comparable with others e.g. IPC-TM-650. You should start monitoring, heat up the chamber, and then apply humidity. This way the effects of volatile materials can be seen, and the progress of moisture penetration may also be seen effecting the SIR as the test progresses. Alan Brewin Concoat Ltd Concoat Ltd Email: [log in to unmask] Alasan House, Albany Park Tel: +44 (0)1276 691100 Camberley, Surrey GU15 2PL UK Fax: +44 (0)1276 691227 -----Original Message----- From: Chan, Marcelo Sent: Wednesday, November 05, 1997 10:01 PM To: 'Graham Naisbitt' Subject: RE: [TN] [AS] What parameters do other companies use when evaluating the e ffectiveness of Assembly h ouses builds Hi Graham, I have an interest on your Auto-Sir technology.... Is it possible to verify the cleanliness under a flip chip prior to reflow if I place a modified SIR pattern under the flip chip.... I do not need absolute numbers, just relative to another SIR pattern that I would place on a QFP and on the bare board.... how would I do it and how would you measure it? What would be the widths and space on the SIR pattern and what voltage would do it at... Marcelo > -----Original Message----- > From: Graham Naisbitt [SMTP:[log in to unmask]] > Sent: Wednesday, November 05, 1997 4:31 PM > To: [log in to unmask] > Subject: Re: [TN] [AS] What parameters do other companies use > when evaluating the e > ffectiveness of Assembly houses builds > > Max, > > Have you previously received info about our Auto-SIR tester? > > Our technique will facilitate an identification of when and where any > defects > occur. > > If you would like more, please contact me off line. > > Graham Naisbitt > > > Concoat Ltd Email: > [log in to unmask] > Alasan House, Albany Park Tel: +44 (0)1276 > 691100 > Camberley, Surrey GU15 2PL UK Fax: +44 (0)1276 691227 > > > -----Original Message----- > From: TechNet On Behalf Of Max Bernhardt > Sent: Tuesday, November 04, 1997 10:23 PM > To: [log in to unmask] > Subject: [TN] [AS] What parameters do other companies use when evaluating the effectiveness of Assembly house builds > ############################################################## 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. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ##############################################################