Hi,
I have a board with a copper pour on both the top and bottom layers, and i want to place a via for thermal reasons. However, i dont want to have the ring of no copper around the via - i essentially want to create a plated hole straight through the board without changing anything else on either layer. Does anyone have any suggestions on how to do this?
Im using Altium 6, so application specific help would be even more appreciated :)
Asign both copper pours to the same netlist node.
Remove any thermal relief from the pth's or via's selected pattern.
RL
This is called "flooding" in some schools. Basically, have a pad connect to a plane without thermal relief. This might be an option in the pad definition.
-- Mark
Forget your presumed CAD software limitatins for the nonce.
If plain vias are used, there seem to be trade-offs. Large vias have no metal in the middle to conduct heat; only the inner rim does that. That induces one to use a number of small vias which tend to increase the amount of copper top-to-bottom but make for a weaker board, increase of expense as well as blobby solder on the back side that HASL does not eliminate. Ideally, a hole in the PCB should be filled (press-fit) with a plug of *solid* copper - and it seems that nobody has found a way to market such strategies.
Back to the CAD software...some CAD packages will allow what you want IF you put the vias in *after* the copper pour (and one might need to dis-allow re-calculation). Another possible trick might be to create a "users" unique via that has NO pad top or bottom - that is to say, just a plain no-nonsense DRILL HOLE. If the CAD program is really nasty, then use a text editor and add in the drill holes in the drill file(s).
Just keep in mind that "thermal via" means a via with a clearance ring and spokes. It should be called an anti-thermal via. The PADS option for non-thermal vias is called "flood over."
With surface-mount reflow and decent soldering irons, there's not much reason to use thermals any more.
John
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