Tom
03-21-2002, 01:36 PM
Hi Tom.
The PowerPCB stock library has no solder mask or paste mask on the pads, but the pcbstandards.com libraries do. How would it help to have all of our parts have a soldermask layer on the pads?
Jesse Thomas
Peregrine Semiconductor
Jesse,
We added Solder Mask to the library padstacks in PowerPCB V3
because there was absolutely no way to suppress soldermask on
part pins in the post processor.
There are many uses for having the solder mask built into the padstack.
1. Most BGA's require unused pins to have a test point. Since PowerPCB cannot support single pin nets and each BGA unused pin needs an isolated net (I.E.: you cannot fanout the unused pins of a BGA to a single net called "Unused") because the test people want each Unused pin to be in it's own net. The solution is to have the engineer add a test point in the schematic and have single pin library parts to form a two pin net. When you placed all the single pin test points under the BGA there was no way of covering them with soldermask. If they are not covered on the top side with solder mask, they cannot be assembled.
2. Some board assemblies require certain parts on the design not be assembled and the manufacturer tells us to cover those part pins with solder mask so that they will pass inspection without a bunch of questions. The only way to control this was to remove the solder mask layer in the padstack. In PowerPCB V4 you can now suppress ref des in CAM when producing solder mask, but it's still nice to have the option to control that in the PCB design.
3. We believe that every PCB designer should have total control over the solder mask process. PowerPCB only allows users a "Global" over sizing. This is unacceptable because each board manufacturer has their own tolerances and solder mask capabilities. We asked many different PCB fab shops what they prefer and they all said the same thing "Please provide us with a 1:1 scale solder mask and let us do the over sizing. We know what we're doing and we know our processes. If you give us over sized solder mask data then we cannot adjust it to fit our process.
Conclusion: The only way to give the PCB designer full control of the solder mask process is to have them built into the land pattern padstack. This was the preferred application by the top managers of Innoveda. The reason why the PowerPCB stock libraries do not have solder mask built in is because Toby Byrd of Red River CAD in Texas built that library and sold it to PADS many years ago and they have not maintained it.
The PowerPCB stock library has no solder mask or paste mask on the pads, but the pcbstandards.com libraries do. How would it help to have all of our parts have a soldermask layer on the pads?
Jesse Thomas
Peregrine Semiconductor
Jesse,
We added Solder Mask to the library padstacks in PowerPCB V3
because there was absolutely no way to suppress soldermask on
part pins in the post processor.
There are many uses for having the solder mask built into the padstack.
1. Most BGA's require unused pins to have a test point. Since PowerPCB cannot support single pin nets and each BGA unused pin needs an isolated net (I.E.: you cannot fanout the unused pins of a BGA to a single net called "Unused") because the test people want each Unused pin to be in it's own net. The solution is to have the engineer add a test point in the schematic and have single pin library parts to form a two pin net. When you placed all the single pin test points under the BGA there was no way of covering them with soldermask. If they are not covered on the top side with solder mask, they cannot be assembled.
2. Some board assemblies require certain parts on the design not be assembled and the manufacturer tells us to cover those part pins with solder mask so that they will pass inspection without a bunch of questions. The only way to control this was to remove the solder mask layer in the padstack. In PowerPCB V4 you can now suppress ref des in CAM when producing solder mask, but it's still nice to have the option to control that in the PCB design.
3. We believe that every PCB designer should have total control over the solder mask process. PowerPCB only allows users a "Global" over sizing. This is unacceptable because each board manufacturer has their own tolerances and solder mask capabilities. We asked many different PCB fab shops what they prefer and they all said the same thing "Please provide us with a 1:1 scale solder mask and let us do the over sizing. We know what we're doing and we know our processes. If you give us over sized solder mask data then we cannot adjust it to fit our process.
Conclusion: The only way to give the PCB designer full control of the solder mask process is to have them built into the land pattern padstack. This was the preferred application by the top managers of Innoveda. The reason why the PowerPCB stock libraries do not have solder mask built in is because Toby Byrd of Red River CAD in Texas built that library and sold it to PADS many years ago and they have not maintained it.