It doesn't look bad at all, particularly considering that you are looking at the projection, not a 3D image. Regards, Vladimir Vladimir Igoshev, Ph. D. Senior Materials Researcher Research in Motion 451 Phillip St. Waterloo, ON, N2L 3X2 Voice: (+1) 519-888-7465, ext. 5283 Fax: (+1) 519-886-0863 E-mail: [log in to unmask] -----Original Message----- From: [log in to unmask] [mailto:[log in to unmask]] Sent: Tuesday, July 19, 2005 1:52 PM To: TechNet E-Mail Forum; Vladimir Igoshev Cc: [log in to unmask] Subject: Re: [TN] BGA voids...some pictures Since I started this thing, I'll share the images that I was talking about. When I first saw these, I was kind of suprised...and a little concerned. As I said earlier, I had never seen voiding like this with my present x-ray system... I really don't know if it's capable of resolution like the system has that took these images. Anyway, when I did see the voids I asked the question if there was a problem with voids like this, and was told no. I was told that the voiding that is in the images are pretty typical, and really don't warrant any concern. In fact I was told that the x-ray images showed that BGA soldered very good. You can see the images at; http://www.stevezeva.homestead.com then click on Picture Page 2, and then look for Pre Void Calculation, and then Post Void Calculation. The system software calculated that the voids within that sphere were 5.3%...and that sphere represented the worst one as far as voiding was concerned in that BGA. Almost all the spheres did have some voiding. Kind regards, -Steve Gregory- Senior Process Engineer LaBarge Incorporated Tulsa, Oklahoma (918) 459-2285 (918) 459-2350 FAX |---------+----------------------------> | | Vladimir Igoshev | | | <[log in to unmask] | | > | | | Sent by: TechNet | | | <[log in to unmask]>| | | | | | | | | 07/19/2005 10:43 | | | AM | | | Please respond to| | | TechNet E-Mail | | | Forum; Please | | | respond to | | | Vladimir Igoshev | | | | |---------+----------------------------> >--------------------------------------------------------------------------------------------------------------| | | | To: [log in to unmask] | | cc: | | Subject: Re: [TN] BGA voids | >--------------------------------------------------------------------------------------------------------------| Hi Werner, That is exactly the point I wanted to make. Every time a crack "coalesce" with a void, it would have to re-nucleate again and it's not an easy thing to do. There is one sentence in your e-mail I'd be very cautious about. Some people (and a very limited number of them) they do report the presence of voids at the interface and for some strange reasons call them Kirkendall voids. As far as I know, it have not been any data published, which would show that the presence of those voids were due to the difference in the diffusion rate in between 2 different materials. So, I wouldn't call them Kirkendall voids, just now. :-) Regards, Vladimir Vladimir Igoshev, Ph. D. Senior Materials Researcher Research in Motion 451 Phillip St. Waterloo, ON, N2L 3X2 Voice: (+1) 519-888-7465, ext. 5283 Fax: (+1) 519-886-0863 E-mail: [log in to unmask] -----Original Message----- From: [log in to unmask] [mailto:[log in to unmask]] Sent: Tuesday, July 19, 2005 11:33 AM To: Vladimir Igoshev; [log in to unmask] Subject: Re: [TN] BGA voids Hi Vladimir, You are correct. I have never seen an overstress failure of a solder joint that involved voids in the solder joint bulk volume. I have seen creep-fatigue failures in SJs with voids that did not involve the voids at all, or that went through the voids, but were not caused by them. I have even seen SJs with cracks in them where the cracks stopped at a void. Overstress failures invariably involve the interfaces of solder joints where for a variety of reasons really weak 'links' were created; that includes interfacial failures due to Kirkendall voids. Regards, Werner Engelmaier --------------------------------------------------------------------- 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. Any use of this information by anyone other than the intended recipient is prohibited. If you have received this transmission in error, please immediately reply to the sender and delete this information from your system. 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