This is a
first for us. Our customer has specified
"Capacitance between layers 4 and 5, and layers 6 and
7, shall be greater than 250pf per square inch, assuming unperforated
planes".
Layers 4 5
6 and 7 are all plane layers (ground/voltage pairs each).
Now, I
understand the concept of capacitance but I have not come across, nor can I seem
to source any info telling me how to ensure that we are manufacturing to this
specification. I have the IPC-2141 which makes reference to controlled
capacitance lines (not planes) but does not seem to provide any useful info from
a manufacturing perspective.
Can anyone
help?
Regards
John
Parsons