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PCB Land Patterns for Surface Mount Packages and Eagle Libraries

Former Member

Hi,

 

If you look at the Interconnnecting and Packaging Electronic Circuits (IPC) document IPC-7351, it appears that the footprint (PCB land pattern) required for any given SMD component will depend on the soldering method used in the underlying PCB assembly procedure. Specifically, Reflow Soldering will require a slightly different land pattern than Wave Soldering for the same device.

 

Now there is a naming convention for IPC footprints, of which RESC2013X65N is an example. Such a name does not appear, on the face of it, to have any field to distinguish which soldering method is foreseen for it. Furthermore, such names are in use in package definitions in Eagle Libraries, without any indication even in the comment lines about the soldering procedure foreseen.

 

Do potential users of the Eagle Libraries, for example those made available by Element14, just use those footprints without question or is there a commonly held understanding about the assumptions used to define the geometries of the land patterns?

 

Many thanks for any light you may be able to cast on this,

 

John.

  • Hi John,

     

    The supplied libraries are ok for general hobbyist use if checked first, but ordinarily people create their own footprints, to suit their needs (and intended use-case, reliability needs, etc). Some hobbyists appear to use the packages/footprints without question, which is not good.This applies to any CAD system, not just EAGLE. That doesn't mean the supplied ones are all useless, but not all will be useful.

    Having said that, I quite like the R_EU and C_EU sets of packages in the supplied RCL library, I have my favourites there and they get used all the time for generic sized SMT Rs and Cs. Anything else, I'll create from scratch.

    You can also write tools to speed up your workflow (in any language of your choice) because of the script execution capability in EAGLE. For any SOIC/TSSOP/QFP/QFN style package, I auto-generate the land pattern to exactly suit the specific requirements, so takes me less than a minute.