I just got my E-Series evaluation kit and finally started trying to do a surface mount layout - so I took a look at the Eagle layout and wow…
It’s not clear to me why you have such an intense ground plane arrangement since the Electron doesn’t seem to have any high frequency issues. The layout I’m currently using for the Electron is very simple and seems to work flawlessly with a 2-layer board where the bottom layer is mainly ground plane but without much in the way of inter-vias. Are there concerns with the E-Series and radiation under the chip or are you just using a ‘stick vias everywhere’ arrangement? Are you just worried about stuff coming back up into the chip? Is there any hope of using this with a 2 layer board?
I also don’t get the pins on the bottom of the chip. I’d like to hand-solder my first few prototypes but that’s fundamentally impossible when you have three ground connections inside the chip boundary on the bottom. It looks like the prototype layout doesn’t connect to them but I could be missing something.
What’s the deal with the various ground pins? Is the assumption that we connect to them if we want or must we connect to them? Even on the Electron you have two ground pins and I’ve never understood if one or both should be connected to the ground plane. Both seems wrong fundamentally but ?
I’m not entirely sure I know what you mean by ‘as advised’. Is there a document describing how to do a layout? In particular (a) whether the ground pins underneath need to be connected and if so to a ground plane with specific characteristics and (b) if you need a ground plane completely covering a layer and with the via arrangement shown in the evaluation board? If the ground plane does have to look like the evaluation board is there a requirement for board composition, copper thickness, and board thickness?
It’s entirely possible there is a document that I just haven’t seen. I looked around but there’s a lot of online content.
Hello @MarkZ,
Excellent list of concerns here! The E Series evaluation board is designed to be as a standard reference guide. You do not have to use a 4 layer stack up, but it is encouraged based on your end product. There are on board switching regulators that can lead to increased EMI if one follows a poor lay out method.
The additional ground pads underneath the module help keep it centered during reflow. You can still have a functional design if your choose to hand solder the module and not solder these GND pads.
The two GND pins on the Electron are provided to help during breadboarding. They are both tied to the same GND internally. Bringing power in and out of the board is always easy when power and GND pins are exposed next to each other.