Placement

[Nguyenvanhieu]

I try to completely place all components on iMX6 board.I see that its difficult.I have some questions:.
1What is the ordering of your placement?I will group all component in 5 type : 1.Processor and big(key) component,connector,mouting hole.2 decoupling capacitor of processor.3 crystal/osc of processor.4 precise resistor,pull up/down,zero ohm res,termination res of processor. 5 other component.Do you order placement is 1-2-3-4-5?
2.Other question,Do you fanout BGA after place key component to see how many space we need or you fanout BGA after place all component?If you do the second way,i think you need re place all the component under CPU.Its ime-consuming.But if I do in the first way,I dont have enough space for these important component.
3.Some of my result is on picture(the left is mine,the right is your).What do you think?Is it ok?Or some recommend?

[Nguyenvanhieu]

And thank you for answering me.

[robertferanec]

Nguyenvanhieu,

1) You may want to start with defined components and positions (board shape, mounting holes, connectors), then continue with CPU + memories, other chips, power supplies (chips, inductors, big capacitors), finish with small components.

2) I do fanout and placement at the same time. Initially I do simple placement under CPU (just to see how many components we have to place there), then I move everything what should be under CPU out of the board and start from middle placing VIAs and components back.

3) I would not do it this way - at least, the memories are too close to each other (you will not have space to route tracks between them) and power supply placement can be improved - especially one of the power is quite bad transistor + inductor + capacitors should be close to each other.

Detailed answers to all your questions are covered in Advanced PCB Layout course Lesson 1 and 2.

[Nguyenvanhieu]

Hi robert,
I understand your answer.But i have another question.I can fanout all the decoupling capacitor near the processor PIn which they need to.So what is your priority?220nF,100nF,10uF,220uF?

[robertferanec]

This is how I place them: nF closest to the pins, XXuF a little bit further (or around BGA), XXXuF around the BGA or/and on the way from Power to BGA.