Richard, Why bake every 12 months? Moisture absorption only presents a problem during reflow, where you can delaminate the component. Provided you bake before assembly, the length of time between bakes becomes irrelevant. In addition, if you store the components at 5%RH, they should be able to be stored indefinitely without absorbing a significant amount of moisture. Thanks Ryan Grant Process Development Engineer MCMS (208) 898-1145 FAX (208) 898-2789 [log in to unmask] >-----Original Message----- >From: Richard Tilbrook [SMTP:[log in to unmask]] >Sent: Tuesday, November 16, 1999 5:05 AM >To: [log in to unmask] >Subject: [TN] Long term storage of electronic components > >Hello again, > >Our company manufactures PCB's for use in military equipment to conform >with ANSI-J001B standard. > >Every once in a blue moon, a customer asks us to do something that isn't >entirely normal, at least in the normal electronics manufacturing world. >We can mostly solve the problem or cater for the request, but in this >case we need to do more research. > >We have been asked to store all the components (including bare boards) >for a military project spanning 5 years. I had previously been >researching into moisture sensitive components, as some of you may know, >and was not entirely surprised to be given this project. > >We will be doing solder tests every 12 months to check for solderability. >We will probably be doing a bake every 12 months too. The idea behind >such a wide gap between bakes being to avoid as much as possible the >formation of intermetallics, which would compromise the quality of >manufacture. > >The storage cabinets we are looking at claim a dryness giving a -15deg.C >dewpoint with 5%RH. What temperature did they say? Good question. > >I would like to store the components at room temperature, unless you >reckon that the intermetallics are a major problem, where we might >consder researching into something lower. > >Have any of you out there stored components fo such a long time? What >procedures did you follow / intend to follow? How effective were these >measures? What do you recommend? > >Thankyou for reading this e-mail, > >Best Regards, > >Richard Tilbrook, >Student Engineer > >############################################################## >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. >If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or >847-509-9700 ext.5365 >############################################################## ############################################################## 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. If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or 847-509-9700 ext.5365 ##############################################################