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Russell Bull
02/27/06 04:02
Read: 546 times

#110842 - Solder mask expansion
Responding to: Suresh R's previous message

The size of the pad should be obvious depending on the component as should the hole size. The solder mask is usually slightly larger so that manufacturing tolerances won't have it overlap the pad. This varies depending on the soldermask technology employed by your manufacturer.

Hole sizes are usually 'as finished' that is the hole size you expect when the board is finished. The manufacturer will compensate for the plating (assuming the board has plated through holes).

Pad sizes are usually bigger is better. Obviously it can't be TOO big! The pcb manufacturer will normally specify a minimum annulus size (around 10thou/0.25mm). Again, the manufacturer will normally specify the soldermask expansion.

So my suggestion is to speak with the pcb manufacturer who will most likely be able to tell you what you need to know. You can also refer to the IPC specifications. see

List of 4 messages in thread
Padstack measurement for new footprint      Suresh R      02/26/06 23:45      
   Solder mask expansion      Russell Bull      02/27/06 04:02      
   Try this link      Joseph Hebert      02/27/06 14:09      
      Thank u joe. the links are useful.      Suresh R      03/01/06 04:51      

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