Hello TechNetters,

I have some questions regarding design and manufacture of flex-rigid PCB.
IPC 2223 recommends to keep a clearance between PTH, placed at the rigid
area, and rigid-to-flex interface. What about SMT pads? Should I consider
the same clearance? Is it possible that coverlay and no-flow prepreg, used
in the middle of 8-layers board, may introduce non uniformity at the
transition region and, therefore, affect the ability to manufacture good
and reliable SMT pads?
Regarding the manufacturing process, I was told that the best way to make a
flex-rigid build up is by joining a flex laminate to a one-sided rigid
laminate by a no-flow prepreg and only after that I can use a copper foil.
However, such a build up results in at least 6 mil dielectric thickness
between "rigid" to "flex" layers and forces my laser micro via between
these layers to be quite large. ( I have 8-layers pcb with a flexible
laminate at layers 4 and 5; laser drills between L1-L2-L3-L4 and
L5-L6-L7-L8 and PTHs). Is it possible to manufacture a reliable flex-rigid
PCB using only copper foils attached to the flex laminate by the prepreg,
in order to reduse the dielectric thickness at the joint?

Thank you,
Yulia.


______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________