Fanout Question - Advanced PCB Layout - Lesson 3

[Tom Yunghans]

Hi Robert,

When you talk about "fanout of the BGA", what exactly does that mean? For signals we intend to connect directly to another component on the same layer (no vias needed), I assume we should complete at least the portion of the route to that component. But how about the rest of the BGA pads? Is it sufficient just to think about how we are going to route the signal, and just drop the via(s) to get access to the appropriate layers? Or should we be routing the signal until it is clear of the BGA?

As an example in Lesson 3, the HDMI signals connect all the way from the bottom to the top. Is it important to route those tracks under the BGA at this initial stage? If so, should we be connecting them all the way to the connector (as shown in the snap-shot below), or just routing them to the point that they are clear of the BGA, leaving the connection to the connector until later?

Thank you!

[robertferanec]

fanout BGA

- You are right, maybe fanout term may be a little bit confusing as it is often used for very short track with VIA. When I say in the video fanout, I mean, take out BGA pad outside of the BGA package and stop routing. So, routing until it is clear of BGA.

The files for practicing are not real progress how the board is routed - the files for practicing were prepared from finished files and some parts were deleted. If you would like to see how exactly the board was routed, this is the video: https://youtu.be/FtWm8Mm6ZPY