"I was thinking if I can bring pads to the edge of board on both boards and be able to connect them together." Do you mean that you push the board edges together then solder them to each other? That type of joint will be brittle and will break very easily. For example as the boards expand and contract with temperature. It will therefore be unreliable. Or will you still use wired links? Please show us an example of what you wish to achieve?

i am open to ideas, i dont like unsolded connectors and not sure what else can I do.  I don't have to connect board side by side, I can create lip on one board that connect on top of other. See the pic bellow of espmodule and note how the edge is soldable <br> 

What you are asking about is this: [https://images.app.goo.gl/vYHmMJp7QHTdDJWJ7](https://images.app.goo.gl/vYHmMJp7QHTdDJWJ7)<br> <br> Please see: Castellated holes in: [https://jlcpcb.com/capabilities/Capabilities](https://jlcpcb.com/capabilities/Capabilities)<br> <br> [https://jlcpcb.com/quote/pcbOrderFaq/Castellated%20holes#:~:text=What%20is%20Castellated%20holes%20%2F%20half,a%20PCB%20to%20another%20one](https://jlcpcb.com/quote/pcbOrderFaq/Castellated%20holes#:~:text=What%20is%20Castellated%20holes%20%2F%20half,a%20PCB%20to%20another%20one)<br> <br> [https://easyeda.com/forum/topic/castellated_holes-z82k0wc6o](https://easyeda.com/forum/topic/castellated_holes-z82k0wc6o)

Thanks thats exactly what i was looking for