Documentation required for specifying a flexible pcb


#1

I have some background in electronics and have had some basic rigid prototype boards made. However I am new to flexible circuits and need to design one with an FR4 stiffener. I find very little literature out there for “beginners”… someone with electronics knowledge but little experience all the ins and outs of PCB fabrication. I have been using Kicad and find these forums to be very helpful. I am hoping someone can give some tips or links of what sort of documentation (other than Gerbers) is included when asking for a manufacturing quote? I have seen some stackup drawings but there are many variations and formats. I don’t know how much detail to include. Is more detail better or does being too specific result in higher manufacturing cost? Thanks in advance for any info.


#2

Often I find it’s best to contact the manufacturers that you think you’ll be using to fabricate your boards. Ask them what they can do and see if that matches your desired specs. If it does, add those requirements to your fabrication notes.

Gerbers should contain all the information needed to fabricate a board design.


#3

I have received specs from manufactures and most have capabilities far beyond my needs… I think. Half the terms & abbreviations they use I have to dig and research. Are there some books, tutorials or informative sites on the various manufacturing processes available, the terminology, specifications etch and their impact on cost and performance?


#4

I worked with Circuits, LLC last year when doing my first flex boards. They have a downloadable design guide linked on their site that will probably be helpful. You’ll still want to talk to them after reading the design guide, since there are different design optimizations for a “static” flex (flexed on installation but doesn’t move much afterwards except for equipment vibration) and a dynamic flex that is in motion throughout the equipment’s service life. For example, a static application can live with a via or two in the bend but you really want to avoid them in a dynamic application.

As far as documentation, I just needed the standard Gerbers + drill file and a separate CAD file with the outline of the complete board and the locations/dimensions/fittings for the rigid frame elements and material specifications.

#include < std_disclaimer > // Just a customer


#5

Thanks @RichWebb for the the excellent link. I’ve since found a number of other useful links. Some of the material is specific to the vendor’s capabilities but useful reading nonetheless. Some are free to read online, some you have to register to allow downloading. Here are some of these links, in no particular order offered with the same disclaimer - I’m just a user with zero to gain in offering these resources.


http://www.pcbuniverse.com/pcbu-tech-tips.php
https://www.multi-circuit-boards.eu/en/pcb-design-aid/introduction.html
https://www.sfcircuits.com/pcb-school
http://www.bestfpc.com/design-guide/
http://www.designingflexiblecircuits.com/
http://www.minco.com/ResourceCenter
http://flexiblecircuittechnology.com/flex4/
http://www.epectec.com/guides/


#6

Hiya,

Were you ever able to figure out what is needed for flexible circuits? I am working on a similar project and would love to know the answer. Also, were you able to design the full flex circuit in Kicad?

Thanks!


#7

I found first getting familiar with some of the terminology used in the posted links, then find a manufacturer that lets you ask questions is the best approach. I ended up supplying Gerbers, with drill files. The outline for the integrate stiffener (glued at time of manufacture) was imported into one of the Kicad “spare” layers such as User or Dwg. Be sure to include that layer when you export Gerbers and communicate that in writing to your manufacturer. Also, there are lots of various manufacturing options options out there. I did not have any special needs so I asked the manufacturer to use standard material when quoting. If you do have special requirement then dig deeper into some of the mentioned literature to understand your need and so you can better communicate it to your manufacturer. Good luck!


#8

Were you able to prepare all of the files for your flexible circuit in
Kicad? I am hearing conflicting reports saying it is not possible. Were you
able to? Thanks so much for your help!


#9

Gerber files are all that my manufacturer needed, as long as one of the Gerber layers had the stiffener outline. If you have specific thickness requirements then you may need to create a stack-up drawing. That is something that Kicad does not generate.


#10

Awesome - thank you for your help!


#11

BTW, check out my this other discussion about using Kicad for a rigid-flex design. It has a few images of a stack-up that I simply generated using Excel.
Method of work for generating rigid-flex design


#12

As far as documentation, I just needed the standard Gerbers + drill file and a separate CAD file with the outline of the complete board and the locations/dimensions/fittings for the rigid frame elements and material specifications.