The only criteria is the hole-fill criteria for Class 1,2,3. Class 3 requires a 75% minimum hole fill with good visible wetting around 360 degrees. Does this mean that large voids seen in the X-ray imply that the 75% minimum hole fill was not achieved, even though a good top and bottom fillet exists? It can be argued that the hole fill did not reach minimum requirements.
While I sort of agree with Dave Hillman that if you have good top and bottom fillets no reliability issues exist, I also agree with Gebhard that the cause of the voiding could be insufficient copper buildup in the hole.
If that is the root cause of the voids, then the reliability could very well be impacted, because without complete solder fill an open could occur in the hole wall breach if it is in an area at an innerlayer trace junction with the barrel.
However, the presence of both a good topside fillet and bottomside fillet with large voids is unusual. Usually some type of pinholes or open voids in the fillets occur. So I am guessing that there is a possibility that the topside fillets were soldered manually first, and then the bottomside solder cannot flow up into the hole due to the gas seal.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Craig Sullivan
Sent: Wednesday, May 16, 2012 7:15 AM
To: [log in to unmask]
Subject: [TN] Through hole barrel voids

Hi everyone, 

 

We have a certain board with several through hole connectors. The customer has provided us x ray images showing voiding in the barrels. Fillets on both sides are acceptable, and the solderability tests are ok. This seems to be isolated to this board because random sampling on other boards shows virtually no voiding. The only voiding "criteria" I can find is related to BGAs. Is there any published criteria / reference material for this type of defect? 

 

Thank you,

Craig Sullivan

Manufacturing Engineer

MPL Incorporated

P: 607.266.0480

F: 607.266.0482

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