THERMAL RELIF
Thermal reliefs can be safely omitted for vias that stitches ground planes together. Thermal relief setting menu for a ground plane generation part of a layout editor can often differ between less expenseive CAD software and the big one's. The more complex programs offers a rich variety of options for vias, thru hole components and SMD's. Also the width, angle and number of traces can be varied. If the hole is a via to a power plane, the heat relief tracks can be safely omitted. If the hole belongs to a hole mounted component, the heat relief tracks are a MUST. The mounting of SMD's rely heavily on heat relief tracks, since it is important that the two pads of eg. a 0402 sized component must be heated equally in time or else tomb-stoning may occur. For RF and especially high power RF the situation is a bit more difficult, since every mm of trace means some 1nH in series inductance, which often can not be allowed. In such cases, the CAD designer must sometimes cover specific connections with static copper in order to "override" the heat relief tracks generated by the CAD program.