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Re: gEDA-user: Open Source mechanical CAD on the horizon
On Mar 10, 2010, at 4:24 AM, Peter Clifton wrote:
Solder mask aperture is important as well as pad size, since the
stencil
opening probably ought never include areas which are solder-masked. It
is possible (although I'm not sure how useful) to set a partially
masked
pad - perhaps as some kind of heat-sink for a transistor, with a
defined
mask opening.
The unixy side is coming out in me.
It sounds like we want arbitrary mask layers in the footprint.
solder paste mask
solder mask mask
Where solder mask is a negative mask and solder paste is a positive mask
Solder paste is a volumetric decision, where solder mask is area.
I propose that the footprint gets a general mask statement.
Mask[ type, polarity, linked name, shape, scale, shape coords... ]
type - specifies what type of mask it is
polarity - specifies positive or negative
linked name - associates the mask to a pin or pad, used for scaling
bounds.
example you wouldn't scale a solder paste mask larger than a pad it
was associated with.
shape - specifies circular, rectangular, or polygon.
scale - specifies how the mask can/should be scaled.
Thoughts on scaling. volume:200pl, uses a stencil thickness specified
as preference. stencil gerber gets the thickness information added.
shape coordinates - depends on shape in line.
circle - center and radius
rectangle - opposing corners
poly - list of three or more points
grid - center of grid, number of columns (number across x), number of
rows(number across y), grids rectangle pair
others?
line - endpoints and thickness
Thoughts?
Steve
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