Can you list out the Difference b/w OSMT vs SMT , OSMB Vs SMB layers in the PCB.
Iam getting a gerbers from our client like this, i need to know what is the difference b/w these layers & why do we need [OSMT, OSMB] these layers in the gerbers.
Please find attached zip file also have OSMB & OSMT Layers, looking these layers are similar to SMT & SMB layers but I would know why they call it has OSMB(Original Solder Mask Bottom) & OSMT (Original Solder Mask Top).
What I suspect:
If they are using the name "origional SMT" etc then I suspect these are the output solder mask data done to IPC standard and is 1:1 to the pads (cant confirm without view) or some other standard increase on pad sizes. Now most PCB manufacturers will enlage the solder mask opening (especially if done to the IPC-7351 standard) to be commensurate with their process capabilities. Thus this ammended layer can be renamed to just SMT SMB etc, to differentiate the data sent and the actual data used to create the PCB.