GARTHWILSON wrote:
However, if he were to swap the lower signal layer and the Vcc layer, the Vcc layer's distance to the ground plane won't be much different, and all signal traces can then reference the ground plane. The normal stack-up on 4-layer boards is this way
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with .010" separation between layers 1 & 2, .040" separation between layers 2 & 3, and .010" separation between layers 3 & 4. I asked DirtyPCBs what the normal stackup was for 1.2mm-thick and 1.6mm-thick boards in 4-, 6-, and 8-layer, and here's the answer I got:Quote:
4-Layer, 1.2mm (.047") stackup:
1oz copper | 0.21mm FR4 | 0.5oz copper | 0.7mm FR4 | 0.5oz copper | 0.21mm FR4 | 1oz copper
Layer spacing in inches: .0083", .028", .0083"
4-layer, 1.6mm (.062") stackup:
1oz copper | 0.21mm FR4 | 0.5oz copper | 0.107mm FR4 | 0.5oz copper | 0.21mm FR4 | 1oz copper
Layer spacing in inches: .0083", .042", .0083"
6-layer, 1.2mm (.047") stackup:
1oz copper | 0.1mm FR4 | 0.5oz copper | 0.35mm FR4 | 0.5oz copper | 0.11mm FR4 | 0.5oz copper | 0.35mm FR4 | 0.5oz copper | 0.1mm FR4 | 1oz copper
Layer spacing in inches: .0039", .0138", .0043", .0138", .0039"
6-layer, 1.6mm (.062") stackup:
1oz copper | 0.1mm FR4 | 0.5oz copper | 0.55mm FR4 | 0.5oz copper | 0.11mm FR4 | 0.5oz copper | 0.55mm FR4 | 0.5oz copper | 0.1mm FR4 | 1oz copper
Layer spacing in inches: .0039", .0217", .0043", .0217", .0039"
8-layer, 1.2mm (.047") stackup:
1oz copper | 0.1mm FR4 | 0.5oz copper | 0.2mm FR4 | 0.5oz copper | 0.11mm FR4 | 0.5oz copper | 0.2mm FR4 | 0.5oz copper | 0.11mm FR4 | 0.5oz copper | 0.2mm FR4 | 0.5oz copper | 0.1mm FR4 | 1oz copper
Layer spacing in inches: .0039", .0079", .0043", .0079", .0043", .0079", .0039"
8-layer, 1.6mm (.062") stackup:
1oz copper | 0.12mm FR4 | 0.5oz copper | 0.3mm FR4 | 0.5oz copper | 0.15mm FR4 | 0.5oz copper | 0.3mm FR4 | 0.5oz copper | 0.15mm FR4 | 0.5oz copper | 0.3mm FR4 | 0.5oz copper | 0.12mm FR4 | 1oz copper
Layer spacing in inches: .0047", .0118", .0059", .0118", .0059", .0118", .0047"
Note that the inside layers' copper thickness is only half that of the outside layers', ½oz instead of 1oz, meaning .0007" instead of .0014".
I drew this up approximately to scale, to give a better visual idea. (I did not do the 1.2mm 8-layer.)Attachment:
layerSpacing.gif [ 32.68 KiB | Viewed 1148 times ]