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Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


BGA assembly and inspection

cheungs

#3100

BGA assembly and inspection | 7 September, 2000

Does anyone know of a freely-available document which discusses the main considerations of BGA assembly and inspection (x-ray?).

l need to know about pad sizes and inspection standards and when to underfill and when not to etc..

l am looking at assembling a 388-pin BGA:

1mm pitch 0.6mm ball diameter 26x26 array 36 thermal management balls in center 27mmsq package

Cheers m'dears from the old blighty

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Murad Kurwa

#3101

Re: BGA assembly and inspection | 7 September, 2000

Steven,

Try http://www.document-center.com/home. You will find various standards for BGAs freely-available but not for free.

BTW, I have never seen a BGA underfilled. Only FC and CSPs. The standards available will explain when to.....High CTE delta, mechanical strength, etc. You will also need to research the undrfill material aspect as some material cannot be re-worked, i.e., thermoset vs. thermoplastic.

Good Luck Murad

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Keith Ward

#5833

BGA assembly and inspection | 2 April, 2001

Try IPC-7095. It is not free , but discusses in-depth Design and Assembly Process implementation for BGAs. Website is ipc.org

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Philip A. Reyes

#5839

BGA assembly and inspection | 3 April, 2001

Steven,

The design of the PCB BGA pads always depend on the ball size or diameter, i know pin counts and package size doesn't contibute anything about this. The amount of reduction is based on the original ball size, which is used to determine the average land. In determining the relationship between nominal characteristics, a manufacturing allowance for land size has been determined to be 0.1mm between the Maximum Material Condition and the Least material Condition. Try to see the table below for the reduction characteristics, the nominal land size and the target land dimension.

Nominal Ball size Reduction Nominal Land Land Diameter Variation 0.75mm 25% 0.55mm 0.60-0.50mm 0.60mm 25% 0.45mm 0.50-0.40mm 0.50mm 20% 0.40mm 0.45-0.35mm

So for your problem, the 0.6mm ball diameter must have a land pattern or PCB pad of 0.45mm in diameter....this is based from IPC 7095.

And for the inspection criteria... I. Void in ball Class1 Accept Reject 60% 0f ball diameter >60% 36% 0f ball area >36%

Class2 Accept Reject 45% of ball diameter >45% 20.25% of ball area >20.25% Class3 Accept Reject 30% of ball daimeter >30% 09% of ball area >09%

II. Missing Ball

This is prohibited, any evidence is reject.

III. Short ball / Bridging Any evidence is reject.

IV. Open ball

Any evidence is reject.

V. Porcorning

Any evidence is reject

Hope this will help you.... The reference of this is the IPC 7095...try to purchase one, i bought this for only 65U$ i think...this will help you a lot

Phil

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