As you can tell the question of shelf life and storage conditions for electronic components and assemblies is a very complex issue. One of the criteria to consider is the fact that most ICs are classified as moisture-sensitive devices (MSD). This means that the components are shipped from the manufacturer in a sealed dry bag with desiccant and a warning label. The label includes two important pieces of information relative to the safe storage of these components. First the seal bag date provides an indication of the actual shelf life of the sealed bag itself. Since a Moisture Barrier Bag is never perfectly hermetic, it will absorb some moisture from the ambient air and eventually the desiccant will saturate and moisture will exceed the safe level for the components. By definition, the packaging guidelines included in the joint IPC/JEDEC standard J-STD-033A guarantee a shelf life of at least 12 months at conditions of less than 40C/90%RH. This is conditional upon using the proper type of dry bag (Water Vapor Transmission Rate WVTR is less or equal to 0.002 gm/100in2 in 24 hres ar 40C) and the proper amount of desiccant (Ref. J-STD-033A, section 3.3.2.2). The second important information is the maximum floor life of the components once they are removed from the sealed bag, prior to reflow. This can vary from a few hours to a few months. An important consideration is the fact that if you are re-sealing components that have previoulsy been exposed to ambient conditions, the moisture gradient that was previoulsy absorbed will continue to diffuse towards the die interface and may eventually exceed the critical limit. In other words, re-sealing MSDs in a dry pack does not necessarily stop the floor life clock and your components may expire while they are stored in a re-sealed bag. This would be applicable in the case of assembled PCBs being placed in re-sealed dry bags for example. Of course it is always possible to re-set the floor life clock by completely baking the components and boards prior to re-sealing them in dry bags. Once again the guidelines for baking components and boards are included in J-STD-033A. On the subject of vacuum, this is not required for dry storage of MSDs. A simple heat seal with the proper quantity of desiccant will provide the protection required. I suggest that you familiarize yourself with J-STD-033A since the Moisture-sensitive components will most likely be your most critical components. This document is a free download at www.jedec.org. Once you define a process that meets the requirements for MSDs, everything else should be much simpler. I hope this information is helpful, do not hesitate to call or e-mail if you have any questions on the above. Francois Monette Cogiscan Inc. Tel : 450-534-2644 [log in to unmask] www.cogiscan.com ------------------------------ Date: Sun, 27 Apr 2003 10:27:35 +0300 From: Reuven ROKAH <[log in to unmask]> Subject: Expiry time in vacuum package Hello Technet forum, Pls reply how long Active component of assembled PCB / system can be stored in sealed / vacuum package before use / operating the system / component. Best Regards ROKAH Reuven --------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e 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/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------