[SI-LIST] Re: BGA Breakout.

  • From: Surita Chandani <surita.chandani@xxxxxxxxx>
  • To: si-list@xxxxxxxxxxxxx
  • Date: Thu, 14 Jan 2010 13:19:36 -0800 (PST)



Thanks Roy.

 

 

 

2. When you say â??place them
diagonally to the bga padsâ?? you are referring to the top layer only which 
needs
the BGA pads. Have I understood that correctly?.  Isnâ??t there some kind of 
PCB fabrication
process in which the Ball can sit right on the Via pad?. This would eliminate
the dog-bone structure on the top layer.

 

If I do have the dog-bone structure,
I can connect to the outer row only on the top layer. What are the pros and
cons of connecting to the Via pad v/s the BGA pad?.

 

3. I can see the math when you have a
16 mil pad, however what kind of additional cost should I expect as compared to
a more standard via of let us say 10 mils with 20 mils pad?

 

Thanks.

 

Surita.



--- On Thu, 1/14/10, RRoy@xxxxxxxx <RRoy@xxxxxxxx> wrote:

From: RRoy@xxxxxxxx <RRoy@xxxxxxxx>
Subject: RE: [SI-LIST] BGA Breakout.
To: surita.chandani@xxxxxxxxx
Date: Thursday, January 14, 2010, 6:27 PM

Hi Surita,

1. Add a note on the PCB dwg that you send to the board shop specifying to 
remove all unused pads from the inner layers.

2. For your vias, use a drill of 8mil and pads of 16mils outer and inner and 
place them diagonally to the bga pads, also cover them with solder mask and do 
not use thermals on the pwr planes.

3. 39 (pitch) - 16 (via pad) = 23mils (clearance). You can run 2, 4mil tracks 
at 5 mil spacing.

Richard Roy





      
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