Filing SRBP boards / used shears

[jamesgarvin54]

I am interested to know what is the best type of file for filing edges of rough cut SRBP boards. Is a dreadnought file any better. Does anyone know a used source of PCB shears. Does anyone use an Exakt saw for cutting PCBs.

[marce]

Are you cutting unpopulated boards?
For FR4 based products tend to route out the board using a fish tail milling bit, or use bacon slicer type cutter. The routing option is best for populated boards, especially with SMD components as it puts the least stress on these components.
The dust is not very nice if you have to file them, again if unpopulated do it wet, keeps the dust down and increases life of tool, I use diamond files, again the glass makes PCB. For phenolic paper, I've used all sorts, but quite often wet and dry paper taped to a flat surface, I could experiment with different grits to cater for different qualitys of SRBP.
I always found gentle was best, but havn't used phenolic paper since the early 90's, so my experience with it is not recent
Exakt saws with the correct blade work, sawing is also less stressful than sheering.

[jamesgarvin54]

Yes, just unpopulated boards.

[jamesgarvin54]

Just found the rest of the reply. I take your point - not nice to file boards but covers up bad sawing. I need tiny boards cut 10x30mm for bolt together prototyping construction like Radionic kits.*A shear would be ideal and quick but maybe get an Exakt later. Interested to hear that sawing was actually less stressfull.

[marce]

Quite often PCB's are panelised with 2-10+ PCB's per panel, some SMD components (MLCC's) can be damaged by the stress of de-panelising PCB's.
These type are quite bad (bacon slicers):
http://www.pts.com.sg/pdf_files/V_Gr...iserDP1800.pdf
Laser routers are best, though for an unpopulated board it isn't as critical.
http://www.lpkfusa.com/datasheets/microline/ml350ci.pdf

[jamesgarvin54]

Interesting.

[jamesgarvin54]

marce - have you tried removing material with an abrasive block - are they simular to wet and dry. you have got me thinking.

[jamesgarvin54]

I have solved the problem of cutting tiny PCBs neatly - MINIATURE MITRE BOX AND RAZOR SAW.

[Buriedcode]

Razor saws are awsome, but even on SRBP boards, you'll soon either have to resharpen it, or replace the blade (they're usually replaced). I used to use them for FR4... which gave me around 5 cuts because it was compeltely blunt.

Although its time consuming, for large boards/cuts, I use a snapped off craft knife to score a line in the copper, and on the other side. Because the tip of the blade is snapped off, it starts to 'gouge' a thin trench, which means that when you break the pieces over the edge of a table, its generally clean. Then a few strokes with a needle file, and its done.

For FR4, the 'score n snap' method is much more forgiving, as it generally breaks along a relatively clean line, but SRBP requires deeper scoring.

Failing that, a dremel with a mini circular saw works wonders for non-FR4 boards, I use that when I have to break up a panel of 10+ boards of different sizes.

[dangus]

If you have to resort to filing, laying the file flat on the work surface and pushing the board back and forth makes for a smooth finish. Emery cloth on a smooth hard surface also works.

A sheet-metal shop might allow you to use a foot-operated shear if you have a whole lot of boards to do. A box of donuts (or other pastry as appropriate) might be sufficient payment. When I sheared glass-epoxy boards, the edges were rough enough that I still filed them smooth.