Refer to this article in the October '08 issue of Circuits Assembly. http://www.circuitsassembly.com/cms/magazine/198/7205-october-2008-issue . LGAs should not be used "as is" for military or high-reliability applications. If you want to get compliant leads or solder balls attached to an LGA or BGA, I suggest you have someone like Analog Technologies do it with their laser attachment process. They use a laser soldering machine they developed along with a proprietary qualified process to do the ball or compliant lead attachment. Their process does not use nitrogen, but uses a special anti-oxidizing compound that leaves an amazingly pristine solder sphere or solder joint. The BGA or LGA component body never gets hot during the ball/lead attach process; they embedded thermocouples in the component body, and measured a 1 degree C. increase from ambient during the laser soldering process. The solder spheres or compliant leads are heated from the inside out. Provided the component is later soldered to the PWB using a good, well controlled conventional convection process later, the mean time before failure is nearly doubled for BGAs, and for LGAs with compliant leads or columns the number of cycles to failure can be extended up to 10 times that of the same component soldered directly to the PWB. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Lee Whiteman Sent: Thursday, April 16, 2009 10:06 AM To: [log in to unmask] Subject: Re: [TN] LGAs in a military environment? Wayne, Be careful about making this type of part a BGA through re-balling. We tried that with a similar package (not as many I/O). To get the balls to solder to the component, the refinishing supplier over heated the components, destroying much of the lot. I would prefer to have it packaged as a BGA instead of trying to fix it into a BGA scheme via refinishing. Lee Whiteman, PMP Senior Member Engineering Staff L-3 Communications East Telephone: (856) 338-3508 FAX: (856) 338-2906 E-Mail: [log in to unmask] -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Thayer, Wayne Sent: Thursday, April 16, 2009 10:47 AM To: [log in to unmask] Subject: Re: [TN] LGAs in a military environment? Why aren't these parts BGA's anyway? Is it just the extra inductance? Or is it because putting on solder balls costs money? I'd send them out and get real balls put on them. You may need to limit the solder joint height due to potential parasitic issues, but I'm guessing that 0.15mm (6mils) joint height would not kill the performance and would substantially improve all aspects of reliability. (Underfill may be required to achieve thermal rqmts) Wayne Thayer -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Temkin, Gregg Sent: Thursday, April 16, 2009 10:29 AM To: [log in to unmask] Subject: Re: [TN] LGAs in a military environment? Our failures were by analysis only. We did not go into production with these parts. We were evaluating the fatigue reliability of the solder joints. We tend to be very conservative in our design approach, but we have to be, since we're building hardware that controls the primary power systems in aircraft. We also have generally steered away from QFN parts for the same reasons. At my former employer we designed a product with QFN microcontrollers. We had a very high percentage of failed solder joints after ESS. That company's quality systems and ethics were pretty sketchy, so the parts would go through a rework cycle and if they passed ESS after that, the product was shipped. No cause was assigned, everything was considered an "isolated failure". That product hasn't yet made it to the field (tied to a long development military helicopter program) so the field failure rate is yet to be seen, but it's obviously not going to be good. Fortunately it's not too critical a piece of hardware. Gregg -----Original Message----- From: kwood716 [mailto:[log in to unmask]] Sent: Thursday, April 16, 2009 6:40 AM To: 'TechNet E-Mail Forum'; Temkin, Gregg Subject: RE: [TN] LGAs in a military environment? Gregg, What were the failures? I'm interested because I see LGA usage picking up steam here. Ken -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Temkin, Gregg Sent: Thursday, April 16, 2009 9:22 AM To: [log in to unmask] Subject: Re: [TN] LGAs in a military environment? We just designed out similar LGAs made by Linear when a reliability analysis showed VERY EARLY failures probabilities for our typical operation cycle over a 20 year life. You can certainly get them soldered and have them pass a screen but that may not be the whole picture. Depends on your operating environment/life requirements. Suggest having someone who is good at analysis run the numbers. Gregg -----Original Message----- From: Graham Collins [mailto:[log in to unmask]] Sent: Thursday, April 16, 2009 3:32 AM To: [log in to unmask] Subject: [TN] LGAs in a military environment? Hello Technet! One of our designers is advocating using a LGA component in a military product. Anyone out there doing it? I'm wondering (worried) about the reliability since it has a very low standoff. And cleaning issues? An example of the parts I'm referring to: http://www.linear.com/designtools/packaging/lga/05081807_a_lga66.pdf A Linear Technologies p/n LTM4604 regards, Graham Collins Halifax Production Engineering (902) 873-2000 ext. 6215 --------------------------------------------------- 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 ----------------------------------------------------- --------------------------------------------------- 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 e-mail and any files transmitted with it may be proprietary and are intended solely for the use of the individual or entity to whom they are addressed. 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