What puzzles me is that that my topic is pretty generic, nevertheless I didn’t find it on the net. It is as follows.
When I have a DIP socket on my board I can only solder the back side because the front is covered by the socket. Nevertheless the corresponding footprints (e.g. Package_DIP:DIP-14_W7.62mm_Socket_LongPads) allow trace connections on both sides. Inhibiting connections on the front could reduce accidental mistakes considerably.
I tried to edit a standard library footprint accordingly, but i didn’t find a strict forward way. So what am I missing?
I’m not sure I understand why you want to limit yourself that way. The front and back pads are linked by plated through holes so does not require soldering the pin on both sides to ensure a through connection. You are free of course to not put traces on one side.
Your first problem is you tried to modify a footprint from a Kicad library. These are read only, and cannot be modified.
You need to place the Kicad footprint into a personal library before you are able to modify it.
I find videos hard to see and follow, but I think I am repeating @BlackCoffee .
You need to go into Pad Properties and change “Copper Layers” to “Connected Layers Only”
This means there will only be a pad if a track is connected to that pad and only on the layer the track is placed.
You can prove this by using the board flip function in View and by switching off the layer on which the track is connected.
@hreba, I think this relates to single sided PCBs, right? Everyone’s forgotten about those, double sided PCB with plated holes are the standard today, as ordering custom prototype PCBs has become so cheap and easy.
If you really want to make single sided PCBs, just turn off the top layer, aka F.Cu (click the “eye” icon in the layers list on the right) and work on B.Cu only. That’s the easiest way.
I don’t think so.
With single sided PCB’s (one copper layer, not footprints on one side) there would never be copper on the top layer at all, and thus no pads.
with a dual layer PCB, pads on the top are probably required because of the ways PCB’s are manufactured. Normally they do:
Start with thin copper layers on both sides.
Drill the holes and make inside conductive.
Electrolytically plate the holes, which also deposits copper on both outsides.
Print the mask for the tracks.
Etch the PCB.
Apply solder mask and silkscreen.
If there are no annular rings on the top side, then 4 would be difficult. You would have to plug the hole with some mask to prevent the etchant from entering the hole in step 5. Although I’m not sure how they normally prevent the etchant from etching the copper inside the via holes.
A typical dip socket footprint has lands on both the top and the bottom, as well as plating inside the hole. When soldering from the back side, most of the time the solder wicks to near the top pad.
While I agree with you that “hobby” boards should not have clad under the socket (or chip) for flexibility reasons, there is no reason you cannot use the current foot print and simply do not put traces on the top side.
On single-sided boards I simply ignore the front layer or use it to model zero-ohm-resistors. Double-sided boards are the problem, when you discover that your have to throw away your nearly finished board (populated and partially soldered) because you cannot access some pins on the front side.
You are perfectly right, I could simply not put traces there. Fact is that after a lot of hours in front of the PC, late at night it happens, nobody warns you and in the end, after a lot more working hours you throw away a nearly finished board.
@hreba : I assume this is for self-etched boards, where you are able to produce double-sided boards, but no plated-through-holes. You connect your vias all actually by solderwire.
For this approach I understand the restriction for connecting pads only at the bottom side. This affects also other parts, like THT-relay or some THT-inductors. (I have done this method also in previous times).
I see two solutions:
use the standard footprints from the standard libraries and in the check all THT-pads if they got connection tracks on the topside. As you mentioned this could produce human errors
built your own footprint-library for the parts in question. This still doesn’t prevents you from using the standard footprints, so this is also not foolproof. And building your own footprints is work.
To modify a footprint for your needs you have to add a rule-out area around each pad.
This must be done on your personal version of this footprint (don’t modify the standard libraries). The rule-out area must belong to top copper layer and should only have the “disallow tracks” checkbox set.