[SOLVED] OSMT, OSMB Layers in the Gerbers

[anil.rajun]

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.

 

[cyberrat]

What do you mean by OSMB and OSMT layers?

What are they for?
What data is on them?

 

[anil.rajun]

Here is the attachement, it is smiliar to SMT & SMB Layers.

 

[marce]

They look like standard solder mask layers, a screen shot with top copper ASMT superimposed would give us a beter picture.

 

[anil.rajun]

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).

 

[cyberrat]

It is not attached.

Are you making the acronym OSMT and OSMB ? what does i stand for?

I see that SMT = Solder Mask Top and SMB = Solder Mask Bottom (it would be better when asking for help to use the full name).

As already said, showing some of the other layers at the same time might help.

 

[marce]

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.