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Re: Patches, MSVC and bitmap underlays


Hi Jean-Pierre,

> a background bitmap is more like the grid that can be shown or not,
> but cannot be plotted, and is not a layer.  Layers 29, 30 and 31, not
> yet used in Pcbnew, should be left for something related to the board. 
> A background bitmap is not a board item. 

I'm a long-time kicad user and have been championing the use of
open-source tools (and kicad) at my work.  We are doing very challenging
layouts for high density systems.  Just about every month the question
comes up whether we will need to switch to a commercial program such as
Altium to be able to build the next board. 

The hot points have been: buried vias, controlled annular rings on
BGA pads and two-way interface with mechanical CAD.

I've finessed the annular ring problem by writing a script to generate
custom .mod files based on a textual representation of the required pad
stack.  Neither Pcbnew nor the 3d display allows visualization of the
inner annular rings so we have to plot gerbers to test the output of the
program.  Messy, but our team is still using kicad... 

The requirement for the mechanical CAD is that we are designing boards
to fit into things like portable WMV players and thin laptops.  The PCB
often has intricate 3D interferences and precise connector locations. 
We have to interface with existing holes and flex cables with very
limited tolerance for connector placement. 

Being able to put a precisely scalable bitmap generated from a
photograph or a CAD drawing into the PCB editor allows for documenting
and placing connectors, routes, and mounting holes with respect to the
environment the board is being designed for. 

Another use for a 2d DXF or PNM overlay would be to allow easy reverse
engineering for boards for which CAD files are missing.  I had this task
to do for a company that needed to replicate Silicon Crystal Furnaces
originally built in the early 80's.  (The company owned the rights to
the furnaces, but all documentation had been destroyed during a buy-out
in the 90's).  I had to tediously measure and manually place all the
connectors to fit the legacy mechanical constraints.  A gif underlay of
the old assembly would have made the job trivial and the layout self

kind regards,
Rick Walker

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