BLAZE Minimum Layers

[PaulBoston]

I work for a company where the dollar is king.
I have just completed my first PCB design using BLAZE router.
A small board 200mmX80mm a BGA and a few bits and pieces.
The BGA 196pin 14x14 with 1mm pitch.

I had no trouble routing the board with 6 layers and .15mm trace/space

BUT I am no being asked to route the board as 4 layer
inner layers being power/ground.
ANY COMMENTS? Can I do it?

Thanx
Paul

[Tom]

Paul,

I hate when management asks you to do something AFTER you have successfully completed a project.

Anyway, I would ASCII out just the data that you need and import it into a 4 Layer Start File. Throw it into BlazeRoute just to prove to management that it can't be done.

Basically you must conclude that the 196-pin 1mm pitch BGA requires Inner Layers to solve all the connections. I.E.: You must prove that the routing solution on 2 layers is a physical impossibility. Now on the other hand maybe it's possible if you reduce your trace width from 0.15mm to 0.1mm so you can achieve 2-trace technology.

You need to sacrifice somewhere and the 0.1mm trace on 4 layers will be cheaper than a 0.15mm trace on 6 layers. I'll attach a 1mm pitch BGA showing 0.1mm traces. The via size is 0.5mm Pad, 0.25mm hole and a 0.7mm Anti-pad.

[PaulBoston]

TOM
WOW
THANKS AGAIN
Paul
I was heading in the 0.1trace/space area. Tho I was caned for
using 3.9mils instead of 4mils. It is a worry?

[Tom]

No worry at all and besides, you have to use a 0.1mm trace/space because you are using a 0.5mm via pad placed on 1mm centers. this leaves 0.5mm space in-between the vias and that's equal to two traces and 3 spaces.

And besides, the difference between .0039" and .004" is so small that's it's totally invisible to the human eye. Even under a normal magnifing glass.