For MCMs and BGAs, the important elements of the simulation are the dielectric
stackup definition and the description of a 3D structure in two dimensions.
But these simple devices were ill-equipped to put precision holes in multiple-material
stackups without running at the slowest safe speed and without frequent stoppages to sharpen drill bits.
Always seek approval from the fabricator after estimating impedance
stackup solutions.
For an inner layer, sandwiched between a uniform ground layer and a plane with multiple power islands, a logical strategy is to design the
stackup with the inner signal layer placed close to the solid ground and far from the split power plane.
Next, the designer must review layer sequence to include symmetrical and asymmetrical layer
stackup. Lastly, spacing between layers must be considered to include embedded capacitance and impedance control.
Again, this example was designed for a 0.03[inches] offset stripline
stackup of a Teflon-based material ([[Epsilon].sub.r] [approximately equal to] 3).
For instance, during
stackup, a fabricator subjects the various layers of a PCB to multiple lamination cycles, where the prepreg and epoxy-glass (or other substrate material) bond under heat and pressure.
All the other information--function of images and image elements,
stackup, materials, colors and general instructions--is, frankly, a confusing mess that forces CAM engineers to search for, interpret or even guess designers' intentions.
To combat this problem the design team has had to take into consideration, and therefore need to control, the effects of the board
stackup, routing, placement, etc.
Other features include PCB
stackup visualization, a bidirectional interface to create, predict and define all materials and configurations of PCB materials; PCB batch card management; and mechanical CAD management.
* Elimination of tolerance
stackup or accumulation from the nonfunctional surface.
DUE TO ITS effect on both a PCB's electrical and mechanical performance, a sound PCB
stackup strategy is vital to creating a reliable PCB.