Are examples of PCB routing for the MPC5748G 256-pin BFA available? How many layers are required?

[carlvanwormer]

I'm trying to set up a new PCB design.  All of the dev kits for this part are not BGA.  I'd like an example of the BGA escape routing for the 256-pin BGA part.

[lukaszadrapa]

I can see it's 8-layer board:

http://www.nxp.com/assets/downloads/data/en/schematics/X-MPC574XG-256DS_SCH.pdf 

See attachment.

Lukas

[carlvanwormer]

I see the link to the schematic, but I don't see an attachment.  Is there some way I can view the PC board?  Was this board the same BGA size and pattern as the MAPPBGA used by the MPC5748G?  I don't want my PC board layout to start with 6 layers if I will need to change to 8 layers to finish.  I was also hoping to find a generic BGA-256 (16 x 16, 1mm centers) escape example to start with, rather than to invent one on my own.  

Thanks,
Carl

[lukaszadrapa]

You need to be logged in. Then you should see the attachment. This is the direct link:

https://community.nxp.com/servlet/JiveServlet/download/871315-1-399215/GRB-27899_B.zip 

These are the gerber files directly for MPC5748G daughter card in 256BGA package.

Regards,

Lukas

[carlvanwormer]

Thanks for the link to the Gerber files.  The routing around the BGA pads looks quite crowded.  Checking the details shows the BGA land pads for the balls to be 0.71mm, and the thinnest traces at 0,089mm.  Reviewing AN10778 (PCB layout guidelines for NXP MCUs in BGA packages) shows the recommended BGA-256 land pads as 0.45mm and trace/space for single runs between balls at 0.15mm.  Is there a reason that the daughter card was made with bigger pads and smaller traces?  I would prefer the dimensions from AN10778, but I would like to have good reasons for my choices.

I don't want to sound like a grumpy old man, but are there any good examples of an escape pattern MPC5748G 256-pin BGA?

Thanks,
Carl

[lukaszadrapa]

Hi Carl,

I'm afraid that I don't have example for MPC5748G.

Not sure why the daughter card is designed in this way. Considering standard IPC-7351B, land pad should be really 0.45mm if NSMD pad design is used. This is document from Freescale time:
http://www.nxp.com/assets/documents/data/en/application-notes/AN5126.pdf
The only idea I have is that there are larger pads because there's socket on the board - it's not the MCU directly.

Regards,
Lukas

[carlvanwormer]

I'll submit a request for technical support case to be opened from the official support site.  I'll report back if I get more results.

Thanks,
Carl

[lukaszadrapa]

Hi Carl,

useful details about PCB design can be found in this application note:

http://www.nxp.com/assets/documents/data/en/application-notes/AN5220.pdf 

The EVB daughter cards are usually six-layer boards but may not be indicative of routing requirements for a specific application. I will check if I can provide gerber files for 256 BGA daughter card.

Regards,

Lukas