Problem with ground plane - Page 1
Forum section: electronics / general

author: x18
author_rank: Contributor
timestamp: March 27, 2012, 04:02:37 pm
content: hi,in the picture you see my problem. i rotated a tqfp package with exposed pad around 45°. but now the vias in the middle of the pad are no longer connected to my ground plane. what can i do to get every via connected to the groundplane?

author: JuKu
author_rank: Frequent Contributor
timestamp: March 27, 2012, 05:10:51 pm
content: Add some tracks manually. Not the most elegant solution, but fast and works.

author: Rufus
author_rank: Super Contributor
timestamp: March 27, 2012, 05:14:46 pm
content: Quote from: x18 on March 27, 2012, 04:02:37 pmIt would be helpful to know what it looked like before rotation.I am not sure you want thermal reliefs on stitching vias for a thermal pad. Making those vias direct connections or reducing the plane clearance should let it pour between the vias.If before rotation the thermal spokes were keeping the plane inside the vias intact then you could try converting the vias to free pads which will allow you to rotate them by 45 degrees and the thermal relief spokes will rotate with them.You could also reduce the remove copper necks setting for the plane which might also make it pour between the vias.

author: hans
author_rank: Super Contributor
timestamp: March 27, 2012, 08:53:46 pm
content: What I often do is add a rule like :IsVia and (Net='GND')And set the polygon connect to no thermals (direct connect). You have to add a rule at Plane->Power Plane/Polygon connect Style. I think in this you need a polygon rule. Add one rule with the query I added above here on first object. Leave second object at 'All'. Set the connect style to Direct Connect. You would have 2 rules now, one that matches (GND) via's, other that matches 'All' (thus the remaining stuff to connect).If it doesn't pick it up correctly, you may have editted the wrong rule (the lower priority one of list). You can either swap them, or explicity force the other rule not to work on these gnd via's any more. So instead of the first object being 'All', it will be:not (IsVia and (Net='GND'))(I don't think the net check is a must, because via's are normally not soldered or used for components).This way, there are no thermal reliefs on the GND via's, and so it won't block the internal via's. I can imagine that you want thermal reliefs if you want to solder through these via's to the QFP heatpad, but I think it should be able to be soldered.. I atleast made it work on a MSOP-10 with heatpad that had no thermal reliefs on bottom and top. I removed the soldermask at the bottom and was able to solder it , even with lead free solder. Had to turn the solder iron up to 400C, though.

author: stefanh
author_rank: Contributor
timestamp: March 28, 2012, 04:18:15 am
content: Similar to what JuKu suggested, I would place a large recantangular fill (rotated 45 degrees) to cover and connect all those vias for a quick and simple solution without altering your design rules.

author: snoopy
author_rank: Frequent Contributor
timestamp: June 05, 2012, 05:33:15 am
content: I assume the vias are part of the footprint.I can only speak for experience with 99SE but it should be similar with Altium.This usually happens when you edit the footprint and update it on the board. Any of the vias lose their net ID so any plane connections are lost as well. The solution in 99SE is to run "Update free primitives from component pads" which believe it or not is also in Altium under Design -> Netlist -> Update Free Primitives From Component Pads...However be careful when you use this function because any non track connected free vias will lose their net ID's even if you have assigned them to a ground plane. Maybe it is different under altium.regardsdavo