In this stack-up what are those presented in right-side of picture? enter image description here


The person who respond from manufacturer told me that is "residual copper ratio". But I think she is misunderstood because there is nothing about it on the web! This is from PCBway, and I think it is maybe 4350B since I have other 6layer stackup like in the picture attached, that they have written 4350B next to it's (Roger layer) percent number.

Update regarding to Elmesito's answer: enter image description here Can your theory (%s are the compressing ratio of thicknesses) explain this other stack-up and "residual copper ratio"in last paragraph?

  • \$\begingroup\$ Does it have a title line? \$\endgroup\$ – Eugene Sh. Mar 4 at 20:26
  • \$\begingroup\$ Looks a like an academic published table not a PCB Fab dwg or stackup readme file. Rogers makes dozens of different PTFE's, FR4's and Ceramic.. I suspect the L refers to 4 conductive layers and who knows what the % means \$\endgroup\$ – Sunnyskyguy EE75 Mar 4 at 21:31
  • \$\begingroup\$ If the context does not discuss it, what are the specs? =tbd \$\endgroup\$ – Sunnyskyguy EE75 Mar 4 at 21:36
  • \$\begingroup\$ Any idea which Rogers material they're talking about? \$\endgroup\$ – The Photon Mar 4 at 21:41
  • \$\begingroup\$ I agree , the vague use of the Brand name without a part number makes the % number meaningless. maybe its the speed of light %c due to e. \$\endgroup\$ – Sunnyskyguy EE75 Mar 4 at 21:43

The percentage shown is most likely the thickness left over once the PCB is pressed.

Rogers is a ceramic material, which doesn't shrink however the resin that sticks the layers together does. That also explains why FR4, a woven and resin filled material shrinks more compared to Rogers.

It is strange, however, that the two 1080 prepregs that are in the middle, which have an initial thickness of 75 micron each, and a final thickness of 70 micron each once pressed, have not been specified as percentage. Maybe the shrinkage is already included in the figures listed for the outer layers.

  • \$\begingroup\$ Rogers also uses FR4, glass and PTFE. I suspect this is PTFE|PP|FR4 \$\endgroup\$ – Sunnyskyguy EE75 Mar 4 at 21:28
  • \$\begingroup\$ Another possibility is it's the resin content if this is an epoxy-fiberglass material. That number can be used as an input to working out the geometry for controlled impedance lines. \$\endgroup\$ – The Photon Mar 4 at 21:40
  • \$\begingroup\$ Can "residual copper ratio" in the updated part of question, help understand the question better? or are you sure? \$\endgroup\$ – mohammadsdtmnd Mar 5 at 9:03
  • \$\begingroup\$ Question update according to your answer \$\endgroup\$ – mohammadsdtmnd Mar 5 at 11:06

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