Reg: PCB fabrication terminologies

[sandeepkiranv]

hello there, can anyone please help me in understanding start cu(copper) thickness and finish cu(copper) thickness in the below invoice. I need to fabricate a PCB with copper thickness of 35 microns. If we consider the start cu(copper) thickness is 17.5mm and finish cu(copper) thickness is 35 microns then what will be the overall copper thickness.

 

[FvM]

"Finished" value is the overall thickness to be accounted for trace resistance, current rating etc.

Consider that the usual additive process for outer layers starts with a copper foil (of start Cu thickness) that is growing by galvanic copper deposition when making the via connections. The start thickness is of course 17.5 µm, not mm.

 

[sandeepkiranv]

"Finished" value is the overall thickness to be accounted for trace resistance, current rating etc.

Consider that the usual additive process for outer layers starts with a copper foil (of start Cu thickness) that is growing by galvanic copper deposition when making the via connections. The start thickness is of course 17.5 µm, not mm.

Thank you for the reply. Sir, so first the manufactures takes a PCB board with copper thickness of 17.5 microns , then they will add another copper layer on top of original 17.5 microns such that the finished copper trace is 35 microns. Is my interpretation correct sir?

 

[KlausST]

Hi,

Yes.

The PCB manufacturers buy standard PCB material with solid 17.5um copper (on both sides).
(then they drill the vias and through plated holes, then they run through some chemistry and)..
then they galvanically add another 17.5um copper.
(Then they etch non used copper, to get the traces)

Klaus

 

[AmitThePCBGuy]

Start copper thickness is the base copper weight measured before the start of PCB fabrication. For outer layers (top and bottom copper layers), the finish copper weight is the sum of the base copper weight plus the plated copper (added during manufacturing process). Example: The base copper weight is 17.5microns and another 17.5microns copper is plated, the finish copper weight is 35 microns.

On inner layers (for a normal through-hole board), the start and finish copper weight would be same as no copper plating is done.