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Solder ball bridging under BGA

Masdi Muhammad

#14456

Solder ball bridging under BGA | 2 September, 1998

Hi, We are having problem with yield loss due to electrical fail. Further investigation shows that the failure is due to solder bridging under BGA. Has been there any study or experience on how this could occur and what we can do to prevent it. Thanks for all the help. Masdi

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Kelly Morris

#14457

Re: Solder ball bridging under BGA | 2 September, 1998

| Hi, | We are having problem with yield loss due to electrical fail. Further investigation shows that the failure is due to solder bridging under BGA. Has been there any study or experience on how this could occur and what we can do to prevent it. | Thanks for all the help. | Masdi

I have been experiencing the same problem lately. I thought I would pass on some info I picked up yesterday. A BGA manufacturer's customer applications engineer told me that approximately 80% of the time where solder shorts are reported back to them, they find out that the root cause is moisture entrapment in the parts. I guess, the parts crack & release pressure during the reflow process (popcorning). He said on BGAs the crack is almost exclusivly underneath, hence normal X-ray or visual inspection will not recognize it. I was told that an acoustic microscope could be used to evaluate defective samples for this phenomenon. If you do not have access to one of those, you might try baking your parts prior to use. Contact the part manufacturer for the appropriate time and temperature.

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Magnus

#14458

Re: Solder ball bridging under BGA | 11 November, 1998

| | Hi, | | We are having problem with yield loss due to electrical fail. Further investigation shows that the failure is due to solder bridging under BGA. Has been there any study or experience on how this could occur and what we can do to prevent it. | | Thanks for all the help. | | Masdi | | I have been experiencing the same problem lately. | I thought I would pass on some info I picked up yesterday. A BGA manufacturer's customer applications engineer told me that approximately 80% of the time where solder shorts are reported back to them, they find out that the root cause is moisture entrapment in the parts. I guess, the parts crack & release pressure during the reflow process (popcorning). He said on BGAs the crack is almost exclusivly underneath, hence normal X-ray or visual inspection will not recognize it. I was told that an acoustic microscope could be used to evaluate defective samples for this phenomenon. If you do not have access to one of those, you might try baking your parts prior to use. Contact the part manufacturer for the appropriate time and temperature.

We�ve had similar problems. We also had problems with BGAs that got warped when reflow-soldering them. This meant that the corners got pressed downwards, hence shorting the corner-bumps. This was solved by using a different package. The problem with moisture within the package resulted in non-working devices, but we�ve never experienced any shorts or bridges. I agree that you should consider baking your components.

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