Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.

Fibres Under BGA's



Fibres Under BGA's | 17 March, 2004

I'm hit with the above problem and found out that the BGA's themselves have fibres on their solder balls. I have soldered some without having the knowledge of the above fibres and found that the fibres are caught between the PCB pad and the BGA solder ball. I understand that this is equivalent to a micro-crack between the pad and the ball but would like to inquire if there is a standard that would say what is the allowable or acceptable width of fibre or crack between the pad and the bga ball. We are using IPC Class 3 and would like to get your help in defining which is pass or fail.

thanks in advance,


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Fibres Under BGA's | 24 March, 2004

Without a proper picture, I'd reject the parts that you describe based on IPC-A-610, 7.2, which says words to the effect: Defect - Class 1,2,3 - Dirt and particulate matter on assembly, eg, dirt, lint, dross, metallic particles, etc.

Absence or prescence of an available standard chapter and verse or not, accepting fiberous material between the pad and the solder ball seems like a very bad idea.

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Fibres Under BGA's | 24 March, 2004

Where is the fibres comeing from. Most of the time fibre is comeing from the stencle wiping process. If useing paper or cloth fibres will shear off in appature of stencle. If this is the case and you are useing an automated printer with a quality wiping cloth then reduce wiper bar pressure. If you are useing a table printer and hand wiping then use a foam wipe. If the print wipe is not the source you can look at clenlyness of the pcb before printing. Fibres do not come with BGA's and dose not come in the paste. Locate the source of the fibre and eleminate it at that source.

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