Is is possible to do a 16 position BGA on 4 layer board?

blewis999 schrieb:

Can someone please advise me on whether it is possible to use a BGA on

a 4 layer board? The center layers ares Vdd and Gnd. So the signal

layers are top and bottom.

 

The Ball Grid Array is only 4x4 or 16 pins, with a .4mm pitch and ball

of .29mm/.26mm/.23mm (I don't understand this either, is that the max,

avg, min size??).

I assume yes (these are max/spec/min).

I have read through the posts, created the device but can't get it to

route for the two center rows. There is a lot of room on the board.

But just looking at the grid I can't really see how to get the auto

router to do this unless there is a way to do a drill hole in the

center of the Ball and plate that through to the opposite side.

 

But I have no clue on how to get this to work, any advice would be

appreciated. Thank you.

Forget the autorouter and route (at least) this part of the board manually.

Tilmann

On Tue, 12 May 2009 08:03:39 +0200, Tilmann Reh <user@domain.invalid>

wrote:

blewis999 schrieb:

 

Can someone please advise me on whether it is possible to use a BGA on

a 4 layer board? The center layers ares Vdd and Gnd. So the signal

layers are top and bottom.

 

The Ball Grid Array is only 4x4 or 16 pins, with a .4mm pitch and ball

of .29mm/.26mm/.23mm (I don't understand this either, is that the max,

avg, min size??).

 

I assume yes (these are max/spec/min).

 

I have read through the posts, created the device but can't get it to

route for the two center rows. There is a lot of room on the board.

But just looking at the grid I can't really see how to get the auto

router to do this unless there is a way to do a drill hole in the

center of the Ball and plate that through to the opposite side.

 

But I have no clue on how to get this to work, any advice would be

appreciated. Thank you.

 

Forget the autorouter and route (at least) this part of the board manually.

 

Tilmann

Ok, thank you. Even routing this manually has some problems. I use a

6mil trace and the pitch between the balls is .4mm, the max ball is

.29mm, therefore there is a maximum of .11mm between the ball edges,

or 2.7mil. How will this work with a 6 mill or even 5mil trace width?

I also need clearance around the trace?

blewis999 schrieb:

The Ball Grid Array is only 4x4 or 16 pins, with a .4mm pitch and ball

of .29mm/.26mm/.23mm

 

Even routing this manually has some problems. I use a

6mil trace and the pitch between the balls is .4mm, the max ball is

.29mm, therefore there is a maximum of .11mm between the ball edges,

or 2.7mil. How will this work with a 6 mill or even 5mil trace width?

I also need clearance around the trace?

I fear you'll need to contact the inner pads by plugged vias.

(Assume a reasonable pad size of 0.3 mm, which gives you 0.1 mm between

the pads. You could try to route a 40 µm track inbetween, with 30 µm

clearance to both pads...)

Talk to your board house to select a useful (and producable) technology.

And/or try to avoid such extremely tiny packages...

Tilmann