Add a ground plane in altium designer 17
Padcap technology offers a high degree of protection in hostile environments because all of the tracks are inside the board.įigure 2.24. Padcap boards are distinguished by the fact that the outer surfaces of the board only carry pads, while any tracks are exclusively created on inner layers and connected to the pads by vias. Additionally, in the case of wave soldering, so much heat would be absorbed by the power and ground planes that all of the layers forming the board could separate, in a process known as delamination.Ī special flavor of multilayer boards known as Padcap (or Pads-Only-Outer-Layers) are sometimes used for high-reliability military applications. This would cause the solder to cool and form plugs in the vias resulting in unreliable, high-resistance connections. If the thermal relief pads were not present, the power and ground planes would absorb too much heat too quickly. The use of thermal relief pads ensures good electrical connections, while greatly reducing heat absorption. The amount of copper contained in the power and ground planes can cause problems because it causes them to act as thermal heat sinks. The solder must be drawn all the way through to form reliable, low-resistance connections. 18 When the solder is applied, a surface-tension effect known as capillary action sucks it up the vias and plated through-holes. Thermal relief pads are necessary to prevent excessive heat from being absorbed into the ground and power planes when the board is being soldered. The spokes in the thermal relief pads are large enough to allow sufficient current to flow, but not so large that they will conduct too much heat. These patterns, which are referred to as thermal relief pads, 17 are used to make electrical connections to the power and ground planes. The power plane has a special pattern etched around the hole associated with lead 8 (the power lead), and a similar pattern is present on the ground plane around the hole associated with lead 4 (the ground lead). Similarly, the power plane has an anti-pad associated with lead 4 (the ground lead), and the ground plane has an anti-pad associated with lead 8 (the power lead). These etched-away areas, which are referred to as anti-pads, are used to prevent connections to the planes when the holes are plated. In the case of component leads 1, 2, 3, 5, 6, and 7, both the power and ground planes have copper removed around the holes. Also note that the holes shown in the prepreg in the exploded view would not be drilled and plated until all of the sub-boards had been bonded together. Power and ground planes thermal relief and anti-pads.įor the sake of simplicity, the exploded view in Figure 18.19 shows only the central sub-board carrying the power planes the sub-boards carrying the signal layers would be bonded to either side. However if you gave a 10 mil design rule and used a 4 mil line to separate planes, you should get an error when you run batch DRC.Figure 18.19. What you draw is what you are telling the tool you want to build. 100 mils (2.5 mm) is most likely sufficient for all but the most sensitive circuits.Ĭan anyone advise if this is expected behavior of the CAD package, or am I somehow missing some feature that I need to enable or turn on? How much will depend on the exact details of your design. If the analog power supplies are exceptionally sensitive (for example, you're doing 20-bit or more conversions) then increase the gap between analog supply voltages and other nets.
My designs are usually 5V mixed signal circuits. If you are using heavier copper, you may need to increase the spacing - contact your vendor for details. 4 mil or 0.1 mm is a reasonable choice if you haven't chosen a vendor yet and are using 1/2 or 1 oz copper weight. Can anyone advise what the minimum distance should be between planes on an internal split plane layer? My designs are usually 5V mixed signal circuits.Īs far as manufacturability goes, the minimum is usually the same as the minimum spacing on any other layer.