TIP

TIP #067: Be sure you fanout all the BGA pins and place all the BGA VIAs before you start connecting signals to it.
Why? It is very hard to add something later.
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[@xenofontzaras2741]

I am routing in almost every design big bga chips with >300 pins , and this is exactly the approach, (using mvias to reach the lower layers) One important thing here. Be sure to put vias on everys pad of the bga, but just as low as you need them. Sometimes I oversaw there was some pad(s) with no via, and then it can happen, as you said, you can not route it out anymore, and need to reroute lot of nets again!

[@shadygross9021]

Hi Robert, that is definitely a very good tip. I have a comment regarding the BGA layout shown. I have read in a few app notes and datasheets that each BGA pad whether used or unused should be connected to a single trace and all traces should be of equal width in the vicinity of the pad. The fanout via may be removed for unused pads, but the short fanout trace (equal to the trace between a used pad and its via) should remain. The reasoning given was to balance the solder tension and have good solder joints for all BGA balls. The short fanout trace for unused pads is also supposed to help during BGA rework. The top layer shown in the video might inspire people to go against those recommendations.

[@RobertFeranec]

Thank you Shady Gross. PS: I have not seen any problems with not connecting all the pads. But maybe it could play some role in very high quantities of boards or in high quantities of boards what need to be repaired. But I am not sure - as I said, personally I have not seen any problems with it.

[@LiveEnjoyment]

wish i did this before, have connected almost everything right know, but i fully routed my SDRAM and ftp connection already.

[@simonndungu1196]

A Great one Robert!!!

[@vishnurajr.v308]

Educative

[@omgkingdano]

Good tip.

[@puneetmudgal2464]

I'm just a beginner with BGA and want to rout a 0.4mm pitch 49 pin BGA package... I was doing it in Autodesk eagle but it's not allowing me to place 0.2mm vias b/w the pads...so which pcb design tool should i use....please help me.

[@orbita1]

Try the one in the video..

[@itzalchemy1846]

Wow yes great tip

[@sakshimehra31]

How to do csp pacakge routing

[@saiiabdelkarim8503]

HOW I can do the fanout ??

[@RobertFeranec]

That is a big topic. But basically, this is what I normally do: 1) powers + grounds + decoupling capacitors 2) memory interface 3) differential pairs and other high speed signals 4) rest of the signals How exactly to fanout a BGA, it depends on the technology what you can use (e.g. through hole vias only, uVIAs, vias in pad, how many layers, etc), it depends on BGA pitch, ... a lot of factors. It is not som simple to answer. But, the best is to have a look at reference design and see how they did it.