When making power polygon , making polygon on the smd-pad has any problems?

Question

I'm now making 4 layer PCB and my PCB has one Power plane (L3) and one GND plane (L2).
Now I just make a connection with inner layer (L3) with Top plane(L1).

At this point, I'm curious that what is the best connection for supplying power.

In the picture, Left one is that making polygon on the component's smd pad. and right one is that first I'm making polygon and routing wires to polygon. I'm new to 4 layer PCB. so I want to know what is the common way for this. I use DC power and this is 3.7 to 4.2 voltage comes from Lithium Battery. I hope many experts may help me.

Thank you for reading.

Answer 1

Thermal reliefs (image 1) are better for manufacturability, as it minimizes the effect of the copper pour as a heat sink. If you have large traces coming off of an SMD pad, the heat will be wicked away more quickly and make it more difficult for the solder to melt. When done on SMD passive components (capacitors, resistors) and similarly-shaped devices, they tend to "tombstone", or stand up on end on the side without the pour:

Photo source: https://www.eurocircuits.com/blog/tips-tricks-why-do-components-tombstone/

Unless performance is a serious concern, I would strongly recommend using option #1 and keep the thermal reliefs.

Answer 2

From left to right I would say that there is no noticeable difference between the 2 especially if this is a low speed circuit.

Generally you work faster by doing the left one because you can do big polygons and make all the connections according to your design rules. By connecting in multiple directions (as in the left) the loop-currents will have more directions to go which could minimize current-loop distance (a good thing).

Depending on your thickness of copper you can calculate the current handling of these bridges. If you supply much more current than the copper can handle then you have a problem of course.

At my university I was advised to do "full-connect" instead of "thermal-relief" because it is an optimization of performance. But it is miniscule and unrealistic for a real-world design in my experience.