Irregular SMD shape

Amer wrote:

Hello,

  I am trying to built a Linear Tech part which has DFN14

package(http://www.linear.com/designtools/packaging/dfn/DE14.pdf).  The

central pad is no rectangular.  When I place an SMD pad, it is

rectangular and cannot be mitered. Does this mean I need to use a

polygon and draw the shape in the signal, cream and stop layers? If so,

how far does the solder mask be from the actual pad?

 

Thank you,

 

-- A

Type "help smd" into the command line of your library editor (without

the quotes).  Look for the roundness parameter.  I think that is what

you are looking for.  It's ok if the pad on the board is rounded on all

four corners while the part has one corner chamfered.

  Tom Sneddon

Type "help smd" into the command line of your library editor (without

the quotes).  Look for the roundness parameter.  I think that is what

you are looking for.  It's ok if the pad on the board is rounded on all

four corners while the part has one corner chamfered.

 

  Tom Sneddon

Thank you.  That will work.  Is this the only way to make irregularly

shaped SMDs?

With the roundness parameter, how do you make sure that you have a

specific radius?

Amer wrote:

Type "help smd" into the command line of your library editor (without

the quotes).  Look for the roundness parameter.  I think that is what

you are looking for.  It's ok if the pad on the board is rounded on all

four corners while the part has one corner chamfered.

 

  Tom Sneddon

 

Thank you.  That will work.  Is this the only way to make irregularly

shaped SMDs?

With the roundness parameter, how do you make sure that you have a

specific radius?

You can not add "named" copper to a lib footprint without DRC errors but

you can make the soldermask and cream layers to the shape you need and

then add a polygon for the ground plane under the part and it will be a

better heat sink then just that pad.

Paul R.

You can not add "named" copper to a lib footprint without DRC errors but

you can make the soldermask and cream layers to the shape you need and

then add a polygon for the ground plane under the part and it will be a

better heat sink then just that pad.

 

Paul R.

So is this how you would create the following part?

http://www.linear.com/designtools/packaging/dfn/DJC22.pdf

Thank you,

A

Amer wrote:

You can not add "named" copper to a lib footprint without DRC errors

but you can make the soldermask and cream layers to the shape you need

and then add a polygon for the ground plane under the part and it will

be a better heat sink then just that pad.

 

Paul R.

 

So is this how you would create the following part?

http://www.linear.com/designtools/packaging/dfn/DJC22.pdf

 

Thank you,

 

A

I would make the solder mask and cream outline equal to the copper

outline of the body pad shown on the pdf. Then use a larger polygon

named what ever net that pad is.

If you add a pin to the part for the substrate then you could use a SMD

pad centered on that area but smaller then any of the edges.

Paul R.