Yes, what you have been told is correct.  However, I personally recommend a
0.005" thick stencil for better paste release out of such a small aperture;
especially if you have fine pitch on the same board.  Many of us are using
square apertures as well, also for better paste release and more solder
volume, without a significant increased risk of bridging.

Thanks

Ryan Grant
Advanced Technology Engineer
MCMS
(208) 898-1145
[log in to unmask]


> -----Original Message-----
> From: Kubes, Romeo (NM75) [SMTP:[log in to unmask]]
> Sent: Tuesday, August 29, 2000 4:43 PM
> To:   [log in to unmask]
> Subject:      [TN] 1 mm PBGA solder joint design requirements
>
> What are the requirements for a proper solder joint design for a 1 mm
> pitch
> PBGA.?
> (Package ball land is 0.018" dia;  ball dia is 0.026"; placed on a mixed
> technology board)
>
> I've been told to:
>
> use an equivalent 0.018" dia pad on the PWB.
>
> solder paste stencil would have 0.018" aperature dia,
>
> aperature wall will be tapered 0.001" total,
>
> Stencil thickness = 0.006"
>
> Is this industry std?
>
> R Kubes
> Honeywell
>
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