On Thursday 12 April 2007 19:57, Brent Brown wrote:
> Hi,
>
> Because it's round then you don't have much choice except a routed board
> outline! Vee-groove can only do straight lines and lines must go right
> across the panel (can't start and stop).

Actually, V-groove could've worked since I don't mind a few straight sections 
around the circle.  But I still can't use it for the other reasons.


> I've done a similar board/panel (boards were 34mm diameter). Four breakout
> areas or "bridges". Each breakout area is two 0.8mm drilled holes
> ...

Sounds good.


> Other general tips for panels:
>
> - Leave room for panel to be held in assembly jig. Typically a 10mm
> "salvage" strip at least on top and bottom edges of panel, often on all 4
> sides to increase rigidity of board.

That's seems to be about the size of the ones on the current panel I have 
(which was panelized by a CEM).  But there are only 2 side rails on this one 
-- see here... http://narwani.net/neil/stuff/Panel_2x5-b.jpg


> - Put a mounting hole in each corner of the board for the assembler to use.
> I typically use 4.1mm unplated holes and locate them on the salvage strips.

Ah-ha!  This is exactly the type of info I need.  I see holes in the corners 
-- is 4.1mm a standard or common size?


> - For machine assembly each board must have "fiducial" marks for the
> pick-n-place machine to register to. Usually 3 marks so it can't get the
> board round the wrong way. Fiducials are usually a round pad with solder
> mask relief to increase contrast. Bottom left fiducial makes a good x=0,
> y=0 reference for pick-n-place coordinates. If components are on both sides
> of the board then you need fiducials on both sides. Very fine pitch
> components may need their own fiducials. Also put fiducials on the panel,
> usually on the slavage strip.

On my individual PCB, I originally had a small fiducial (so 10 available on a 
full panel), which the CEM said they would not use.  Instead, they put their 
own on the rails.  Again, is there a "universal" size that most places can 
work with?  I see Eagle has circles, squares, cross-hairs, etc.  Not sure if 
all CEM's can work with all of those.


> - Size the panel to best suit your assemblers requirements and PCB
> manufacturers capabilities. Assemblers don't like panels too big as they
> flex too much.

This 4.5" x 10" size (full panel) is relatively small I'm sure.  I would like 
to remove the "bridges"/supports on the sides of each circular board so that 
it's only supported by the upper and lower bridges.  This is to make it 
breakaway easier.  Not sure if that will cause a problem, but I would 
think/hope not, as the 2 long side rails will provide horizontal rigidity and 
the bridges on the upper/lower side of each circular board will provide 
vertical rigidity.

>
> - Protel/Altium Designer has a "place embedded board" function, that
> inserts a PCB file in a step and repeat fashion, you specify the spacing,
> rotation, number of x and y steps. Panel file is linked to PCB file so any
> updates are reflected. Eagle and other CAD programs may have something
> similar. Else you are stuck with copy and pasting which is time consuming,
> makes really big files, and can often have issues with duplication or
> incrementing of component designators.

IIRC there is a script for Eagle that automates the panelization as you 
describe, but the cut/paste process is simple enough that I haven't bothered.


One other thing I am wondering about is specifying the routing lines -- if I 
place a line (using the Milling layer) for the board-house to route along, 
they will *center* the cutting-bit there, rendering the individual boards too 
small.  Is there a standard cutter diameter I can calculate/compensate for?  
Or can I specify the cutter size?


> Hope this helps! Brent.

Tremendously!  Thanks,
-Neil.
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