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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


ASHOK DHAWAN

#16764

BGAs centering method | 14 February, 1998

I am beginer in BGA assembly and am confused in selection of pick and place option. As per book on 'implementation of BGA Technology-by 1995 aeic inc. states that BGAs reflow is quite forgiving and you need only Mechanical centering of PBGAs. The IPC-STD-013 states that CPk for a typical 50 mil BGA 256 pin is .68 with mech centering and over 1.5 for BGA ball image alignment .I do not know if somebody is using mechanical centering as alignment method with high BGA yield.Jedec standard the true position of balls wrt edges shows +/-12 mils tolerance in addition to ball dia tolerance.

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ashok dhawan

#16766

Re: BGAs centering method | 14 February, 1998

| I am beginner in BGA assembly and am confused in selection of centering method on pick and place operation.. As per book on 'implementation of BGA Technology-by 1995 aeic inc. states that BGAs reflow is quite forgiving and you can use Mechanical centering of PBGAs. The IPC-STD-013 states that CPk for a typical 50 mil BGA 256 pin is .68 with mech centering and above 1.5 for BGA ball image alignment .I do not know if somebody is using mechanical centering as alignment method with high BGA yield--BGAs one defect means one device rework..Jedec standard the true position of balls wrt edges shows +/-12 mils tolerance in addition to ball dia tolerance which concur that mech centering is not appropriate.

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Scott McKee

#16765

Re: BGAs centering method | 15 February, 1998

| I am beginer in BGA assembly and am confused in selection of pick and place option. As per book on 'implementation of BGA Technology-by 1995 aeic inc. states that BGAs reflow is quite forgiving and you need only Mechanical centering of PBGAs. The IPC-STD-013 states that CPk for a typical 50 mil BGA 256 pin is .68 with mech centering and over 1.5 for BGA ball image alignment .I do not know if somebody is using mechanical centering as alignment method with high BGA yield.Jedec standard the true position of balls wrt edges shows +/-12 mils tolerance in addition to ball dia tolerance.

I've used mechanical centering with great success on my Mydata TP9-2U. The BGA was a ceramic package and the pads were on 50 mil centers.

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