Don't check, just vac bake and test reflow 100 after. Put back in your cabinet with additional absorbert such as mitsubishi stuff. My 2 cents. -------------------------- Sent using BlackBerry ----- Original Message ----- From: TechNet <[log in to unmask]> To: [log in to unmask] <[log in to unmask]> Sent: Fri Aug 14 09:52:43 2009 Subject: Re: [TN] How to check absorbed humidity in IC packages. Checking the weight does not work because minute variance in the material weight (solder ball volume, for example) can represent tons of water. Checking the weight only works for determining the rate of moisture adsorption or removal. Unfortunately, I don't think there is any way to tell what the moisture content is just by weighing one unit and comparing it to one that has been baked out. What you can do is initially weigh a sample, say three or four from each nitrobox, bake them for 1/2 hour at 105 C, weigh again, bake again for another 1/2 hour, and weigh again. If there is a significant delta in the initial reading, the second reading, and the third reading, that may indicate significant moisture adsorption which would mean you may want to bake everything. On the other hand, if the d/dt is constant, indicating very little weight change over time, then the rate of moisture removal is very small, indicating that the parts are relatively dry. This is essentially what you are already doing, and while I understand you don't like it, it is probably the best method. The rate of removal indicates where the moisture content is on the curve. By the way, perhaps you should look into getting dessicators (McDry boxes). No plumbing required, no nitrogen required. You can move them wherever there is 110VAC, and they will actually serve as a long term bake process without the oxidation issues. They pay for themselves very quickly. Not very expensive, perhaps 5K for a very large one. Besides, I never did like putting a bunch of expensive ESD parts inside of a Plexiglas box. Too easy to build up a charge. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Hernefjord Ingemar Sent: Friday, August 14, 2009 7:51 AM To: [log in to unmask] Subject: [TN] How to check absorbed humidity in IC packages. We have a number of Nitrogen cabinets for all SMT components, reels, trays, boxes etc for BGAs, FPBGAs etc...all kind of. The Nitrogen did not flow as usual today, and flow meter did not alarm. We found a regulator issue. The cabinets have been without Nitrogen for a week or more. What is a simple and reliable way to check the moisture content of the components? What sample size do you use? We have taken some five superBGAs, some 20 QFPs and and likewise from a number of cabinets, measured the weight on a 3 decimal balance and placed the samples in a oven at +125 C for the weekend to pass. And we will check weight again on Monday. I'm not happy with this method. Anyone having better idea? To bake out all and everything would take a long time. /Inge --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------------------------- This transmission (including any attachments) may contain confidential information, privileged material (including material protected by the solicitor-client or other applicable privileges), or constitute non-public information. 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