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Re: A few extra component footprins


On Sat, 28 Aug 2010, Alex G wrote:

I've looked at some of the datasheets above, and I think the datasheet
http://pdfserv.maxim-ic.com/package_dwgs/21-0137.PDF is wrong
- the difference between the variants seems to be the size of
the exposed pad (D2,E2), but 21-0137.PDF lists them as identical.

I'm not sure what you mean.
http://pdfserv.maxim-ic.com/package_dwgs/21-0137.PDF lists the size of
the exposed pad as identical for variations of the same N. For N=14 D2
is 1.7mm instead of 1.5mm.

Well, that's what I meant - 21-0137.PDF lists _all_ dimensions for
the "same N variations" as identical, which doesn't make sense.
The other datasheets on maxim-ic.com
lists varying sizes for the thermal pad.

Oh, I see what you're confused about. there are indeed several
variations of the package, but they all fit on the same land pattern.
Who cares if the footprint pad is larger than the pad on the package? It
won't interfere with the soldering process. This makes life easier for
us since we only need one footprint, and considering the 3D Viewer in
kicad is more of a convenience than a CAD feature, it's safe to only use
one 3D package per N, perhaps the one with the larger pad.

Yes, that explains it :-)

I think there are also larger packages as well;

Yes, much larger - up to 56 "pins" :-)

AFAIK, TDFN only goes to 14 pins. TQFN on the other hand, does go to 56.
I think you're referring to TQFN. I'll look over the .dim and see if I
can get some dimensions in (If I can't then I should probably try to fly
to save the world from an idiot mind :p ).

You're right - I overlooked the TDFN vs.
TQFN when searching for the max size :-(

Still, the varying packages sizes for TDFN8, for example, might be a bit
of a headache. Perhaps we should adopt a naming of
TDFN8-M065-3X3, TDFN8-M065-3X2, etc...

Yes, although I would place the size first, I think:
TDFN8-3X3-M065, as the pitch is given (not always,
but mainly) by package size and pin count.

Ref 5 looks interesting, but www.uspro.com times out :-(


Yep, the file http://www.uspro.org/documents/IGES5-3_forDownload.pdf
looks interesting - seems to be the full IGES 5.x specs,
i.e. just what we need, so if anyone's got this file, or has
more luck accessing www.uspro.org, let's have a copy, please ...

www.iges5x.org also had some interesting info, I
think, but that DNS domain is pending deletion :-(

I haven't understood what all the numbers and fields means yet, but
as freecad can read IGES (*), the freecad source should also contain
some useful info for writing a script to convert IGES to VRML.

(*): Well, sort of - freecad is definitely alpha code:
I've tried feeding the simple example on the Wiki to freecad,
and it gets the coloring wrong - the points, arcs and lines
should be yellow, red and green, but they're all shown in black.
Also, Wiki Ref 6: http://www.wiz-worx.com/iges5x/wysiwyg/f214x.shtml
is totally wrong (most of it is missing).
Fortunately, the missing stuff is 2D graphics, and the Molex
connectors shows up just fine (except for the coloring).

Hmm, I just noticed that IGES contains color information. If it's any
consolation, not even Inventor can get the color right (well, except for
the yellow lines).

I found an open source (Java) IGES viewer on
but unfortunately, it's 2D only.

It does get the colors right, though, so I'll
take a look at the source when I get the time.

This page has some interesting "things":

"This release of WISLjr?, the freeware (Lite) version of the WiZ WORX
IGES Source Library, requires the libplot function library included with
the GNU Plotting Utilities"

And I would also like to point out and emphasize:

"will feature libiges-1.0 [..], and hopefully destined to become the GNU
standard for importing IGES files"

I can't see any download link, so I have no idea what they really mean
by that.

They do have a package, igesgump, that can be downloaded,
and it contains an IGES file peeker and a viewer (2D only),
but it was last changed in 2004, and they want USD5000 (!)
for the source code, so nothing interesting there ...

IGES contains a lot of advanced features, such as
spline curves and surfaces, so how easy it is to translate
an IGES file to VRML depends on which features are used.

As KiCad only understands VRML IndexedFaceSet and materials,
any 1D and 2D info (points, lines, arcs, etc.) in an IGES
file will get lost - only the 3D faces can be converted.
However, that should be enough for kicad, I think.

Yes, the 3D faces are all that's needed in kicad. I'm not sure how the
pieces are supposed to be colored; Inventor displays the body and pins
as one piece, in one color.

Worst case scenario, there's also the possibility of converting PRO/E or
STEP files, as molex provides all three variations (though I think STEP
is binary).

... or create the 3D view ourselves from perl :-)

Have you seen how complex the pieces are? Ok, just kidding, some
capacitors in your library are far more complex than that.

Well, they're not _that_ complicated - no
round holes or double-curved surfaces :-)

I'll have a go at deciphering the IGES format - if we can
extract as a minimum a point cloud from IGES, we can use the
coords to get the correct dimensions of a package, including
details like mounting/guide pins, locking tabs and other such
stuff that's usually not specified in detail in the datasheets.

I don't know which will be easiest, as that depends on the
available info on the file formats - probably not much :-(

I thought that converting some faces from an *existing* model would be
the easiest route. If we end up generating the models from Perl, we
could include the metal piece in the middle of the hole, which, for some
reasom, Molex seems to have overlooked.

I say let's keep the focus on generating the footprints, those are the
heart of the matter. The 3D packages can be added after the footprints
are done. That is of course, if you have no preference on getting both
ready at the same time :).


Having looked a bit more at the IGES files, I think the DIY approach is
the easiest, at least unless we can get hold of the full IGES specs :-(

STEP is also a no-go - it's an ISO standard, and thus not free.
Even if we _did_ manage to write a STEP to VRML converter, we
probably couldn't release the source because of license issues :-(

Also, blender can read PRO/E .slp files, but the PRO/E files provided
by Molex are called .prt, and blender can't read those :-(

The igespeek program (igesgump package from wiz-worx) lists these
entities in the IGES file for the two-pin, right angle Molex Microfit:

count   type   description
  30  100:0000 Circular Arc
   5  102:0000 Composite Curve
 373  110:0000 Line
   9  120:0000 Surface of Revolution
  30  124:0000 Transformation Matrix:Right-handed (default)
 130  128:0000 Rational B-Spline Surface - <computationally derived>
   1  186:0000 Manifold Solid B-Rep Object
   3  314:0000 Color Definition
   2  402:0007 Associativity Instance:Unordered Group Without Back Pointers
   4  406:0015 Property:Name
   1  502:0001 Vertex:MSBO Vertex List
   1  504:0001 Edge:MSBO Edge List
 144  508:0001 Loop:MSBO Loop
 139  510:0001 Face:MSBO Face
   1  514:0001 Shell:MSBO Shell - Closed

So, I'm pretty sure, that the missing package bits you (don't)
see are simply stuff that freecad can't do, and thus ignores ...

Colors in IGES are not RGB values, only indices - the standard colors are:
  0 = black
  1 = black
  2 = red
  3 = green
  4 = blue
  5 = yellow
  6 = magenta
  7 = cyan
  8 = white
In addition, there's a type 314 (Color
Definition), for redefinition of a color.


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