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Subject: 0.5mm BGA - tracking - via criteria?
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cartouche
Posts: 14
Online: User is Offline
7/05/2006 8:52 AM  
Does anyone have a recommended rule set for tracking out of a .5mm BGA. Its only the two outer rows that are used.  I'm trying to find manufacturers recommendations but so far no joy.

Specifics.

Would you use microvias to escape from the 2nd row, or go between the outer pads on the 'top' layer?
What is the recommended pad size?  (ball dia = .25-.35) but theres nothing about the 'pad' size on the bga which connects the ball.

Thanks..
SiP
Posts: 0
Online: User is Offline
7/07/2006 1:34 PM  
Route between if possible. Microvias are expensive. You will need fine line substrate supplier which is also expensive. Pad size depends on solder mask defined pads or non-solder mask defined pads which again depends on the substrate supplier. Your trying to design in a vacuum. (no offence) You need to identify a substrate supplier and an assembly supplier and obtain their design rules.
tonykara
Posts: 1
Online: User is Offline
11/29/2006 6:36 PM  
So what did you eventually do?? We're curious.
siriusbliss
Posts: 6
Online: User is Offline
12/12/2006 9:54 AM  
I've always been forced to use microvias, because they are more common and slightly more reliable than really narrow traces - as far as reliability and yield is concerned.

.5mm is a pain, but doable.

Greg
cadpro2k
Posts: 0
Online: User is Offline
12/12/2006 12:00 PM  
For .5mm BGAs, only outer 2 rows used, I'd tend to go with .003+ traces and not uVias. There are plenty of companies that will do .003" lines using 3/8oz CU. Some might even try using 1/2oz if they're good. I've got 2 suppliers in So. CAL that do it for me at the moment. Getting really good results.

Good day.
Mitch
chenli
Posts: 9
Online: User is Offline
12/12/2006 11:55 PM  
Hi cartouche,
You can try the following link:
http://www.pcblibraries.com/resources/GEN-docs.asp
there are many useful tips aboult BGA layout rules!

chenli
dgstan
Posts: 7
Online: User is Offline
12/13/2006 3:16 PM  
Yeah, we've found that 3 mil lines/spacing is preferred (i.e. cheaper) than micro-vias. This is especially true in high-volume production overseas. As micro-vias become more prevalent, that may change.

At first, I was reluctant to use them (I thought it would be more difficult to design with them), but after doing umpteen boards with micro/blind/buried vias, I practically beg marketing to let me use them.
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Forums > Silicon-package-board > PCB Design > 0.5mm BGA - tracking - via criteria?


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