Eagle won’t let me put a via on top of a pad. Do ordered PCBs connect components to the top and bottom layer by default, or do I have to put a via next to each component pad in order to connect it to the top layer?
It’s not a good idea to put a via on a pad, it will wick the solder away resulting in a poor joint.
Just put the via close to the pad with a track joining them.
Leon
fair enough. so in eagle, the pads that are placed automatically by the component packages are attached to the bottom layer only, right?
when I use vias, Eagle doesn’t seem to recognize that they connect the bottom trace to the top one: the airwires still show up. What am i doing wrong?
Good idea or bad, if you want a through hole at an SMD pad, why don’t you make a variant of the device using a “pad” (eagle for TH pad). In general SMD pads are on the top layer and TH pads connect to all signal layers.
How are you creating vias? just dropping them on the board? try naming them a signal. I often drop a via on a board and then name it gnd. I use this for bridging gnd on both sides of a board. on the whole however, I don’t recommend doing it this way for arbitrary signals. The simplest way to add a via is to route a line on one layer, switch to another layer and continue routing. A via will automatically be added. Another way to create a via is to use change/layer and click on a routed segment. Vias will appear at each end of the segment.
ah, I see i should have been clearer. This is a through-hole design, not surface mount. So all my through hole pads connect to both layers? Then I don’t need vias at all…
sorry, im clearly “new”. ive used Eagle to do single sided boards before, and i’m concerned that ill get this all set up and when I recieve my boards, the top layer won’t be connected to anything.
So, assuming pads connect all layers, do the pads themselves appear on both layers, or are they only on the bottom of the board and merely connect to the trace on the top?
The pads for vias and through-hole leads should appear on both the top and bottom layers. I don’t know about Eagle but the Pulsonix software I use lets me switch layers on and off - if you can do that you should be able to check that they are both present. I can also flip the board so that the underside becomes the top. You could also look at the Gerber files produced with a Gerber viewer like GC-Prevue.
Leon
That's correct -- the fabricator SparkFun uses (Olimex? I forget...) actually plates *all* holes (even ones with no copper around the top or bottom). Through-hole pads have copper on top & bottom, and the walls of the hole are plated so that the top & bottom pads are electrically connected.amaurer:
So all my through hole pads connect to both layers? Then I don’t need vias at all…
In Eagle, pads and vias have their own display layers and can be turned on or off separately, but in the final Gerber files, they end up being just a bit of copper on the top and/or bottom of the board. I don't see any option to turn off visibility of only one layer of a pad or via, though. If you're still seeing airwires after routing, it may be because the schematic wires aren't connected properly. I've seen that problem occasionally if I delete a part and drop in a new part. Sometimes you have to delete the wires and re-draw them to get them to connect.amaurer:
So, assuming pads connect all layers, do the pads themselves appear on both layers, or are they only on the bottom of the board and merely connect to the trace on the top?
amaurer:
ah, I see i should have been clearer. This is a through-hole design, not surface mount. So all my through hole pads connect to both layers? Then I don’t need vias at all…sorry, im clearly “new”. ive used Eagle to do single sided boards before, and i’m concerned that ill get this all set up and when I recieve my boards, the top layer won’t be connected to anything.
So, assuming pads connect all layers, do the pads themselves appear on both layers, or are they only on the bottom of the board and merely connect to the trace on the top?
It will work exactly as you think it should. In eagle, pads are in a different layer (17) from signals (1-16). When you produce a gerber, you need to include the pads, vias and top (or bottom) layers to get a correct gerber. Interestingly, smd pads are actually in the signal layer (top or bottom).
I would take a little time to get familiar with the display/hide layers dialog and what the various layers mean.
by the way, ripup on the airwire should fix the problem caused by leftover traces from deleted components.