Digital Signal Processing Reference
In-Depth Information
Exposed microstrip
(”outer layer”)
Prepreg
mats
Ground plane
attached to laminate
Laminate
Stripline (”inner layer”)
attached to laminate
Figure 5.1
A six-layer stackup using core construction. Copper traces or planes are shown in black,
and cores are shown in white. Prepreg mats are shaded.
PTH
Blind
Buried
L1
Copper
clad core
L2
L3
L4
L5
L6
Prepreg
Antipad
Figure 5.2
Circuit board vias in a six-layer foil construction board. The PTH connects L1 and L4.
Note the nonfunctional pad on L3. The buried via connects L3 to L4. The blind via connects layer
L1 to L2.
commonly the plating process deposits copper inside the tube, making the plated-
through hole (PTH) a conductor.
The PTHs have circular pads (rings of copper) that connect the via to signal
traces or power/ground planes. Three types of vias commonly found on circuit
boards are shown in Figure 5.2.
This stackup has six copper layers (L1 through L6). Signals are routed on lay-
ers L1, L3, L4, and L6. Layer L2 is a ground plane, while L5 is a power plane.
The PTH passes completely through the board but only connects L1 to L4.
