Cheap FR-2 manufacture

Just get routed edges. They're still a bit sharp on the corners but there are no loose fibers. Does it really need to be snap-apart at all?

I quite like doing V-scored tabs, so you get a routed perimeter for the most part, then on the straight sides, the material breaks away with a minimal amount of loose burring. This might not be adequate for you though (there are still some loose fibers).

As for source, just look on pcbshopper.com. You can't select substrate unfortunately, but the top names in the list should give you some idea of which ones are the cheapest and most capable.

Tim

-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Design Website:

The issue is quickly distributing complete sets of 1" square boards to a whole classroom of kids. 2 of these, 2 of those, 3 of these, one of those, etc, 30 times. Rather than assemble kits beforehand, it's better if they come attached.

I'll have a think about that, I might be able to make it work. I don't know whether V-scoring a panel into a 1" grid would be cheaper than full routing, but I'm sure the machine would do it quicker.

Indeed - I had looked at the most promising three Chinese outfits from there, but none advertise FR-2 though.

Clifford Heath.

Just because it's not on their website, doesn't mean they don't do it. It might mean you need big enough orders to avoid grouping with other orders for a run of full-size sheets. Certainly one can find plenty of that material in high-volume products.

Have you seen V-groove in FR-2? Usually I see punched and mouse bites. Last time I bought them, which was many years ago, we had all the holes and th e outlines punched. Single layer of course. They warm the phenolic so it wi ll punch nicely and not crack.

Single sided boards are normally done in a different factory from double la yer boards and yet another from multilayer, but often they're related under one owner. They tend to be priced by the square meter, which gives you som e idea of the quantity they'll be expecting.

Tim's suggestion is a good one, just get the boards with routed ONLY edges. The V-groove edges (and sheared edges, for that matter) are nasty. Also th e material is fragile and the copper adhesion tends to be sub-par. The pric e per m^2 can't be beat though.

--Spehro Pefhany

st time I bought them, which was many years ago, we had all the holes and the outlines punched. Single layer of course. They warm the phenolic so it will punch nicely and not crack.

layer boards and yet another from multilayer, but often they're related und er one owner. They tend to be priced by the square meter, which gives you s ome idea of the quantity they'll be expecting.

s. The V-groove edges (and sheared edges, for that matter) are nasty. Also the material is fragile and the copper adhesion tends to be sub-par. The pr ice per m^2 can't be beat though.

FR2 is prone to warp over time & isn't as rigid as FR3,4 etc. And the coppe r tends to come off when desoldering. And it can't handle plated thru holes . I wouldn't go as far as to call it fragile though. It's still functional when warped. Should be quite adequate for school projects. And don't mount heavy items on it like 50/60Hz mains transformers, severe warping can resul t.

NT

Thanks all. I think I'll just suck it up and go with mostly-routed FR4 for now. If it get to a high enough volume, we can reconsider. A row of punched holes in FR2 might make it snap ok (it doesn't need to be tidy, just safe!) but that needs more experimenting to be sure that 10yo's can do it reliably.

Clifford Heath.

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Last time I bought them, which was many years ago, we had all the holes an d the outlines punched. Single layer of course. They warm the phenolic so i t will punch nicely and not crack.

e layer boards and yet another from multilayer, but often they're related u nder one owner. They tend to be priced by the square meter, which gives you some idea of the quantity they'll be expecting.

ges. The V-groove edges (and sheared edges, for that matter) are nasty. Als o the material is fragile and the copper adhesion tends to be sub-par. The price per m^2 can't be beat though.

Snapped FR2 tends to break, how can I put it, so as to make blade-like shap es.

NT

OK, I'm going to chime in here. My own scored PCBs and others I've received from China, haven't shown very serious fibre issues. However, I like to give them a quick finishup step after breaking apart. If I'm energetic and have a low to do, I go downstairs and use a belt sander, very quick. Otherwise I use a small hardware store sanding block. Easy.

My suggestion, don't be tempted to take the easy way out and distribute boards by the sheaf. Break them up, apply the finishing step, and distribute them as individual pieces. Or, if you must send them in bulk to a teacher, instruct them to do the step. You could even include a sanding block with the first order.

A mostly cut FR2 should snap ok, eg a row of 4mm holes (or slots) with 1mm bridges between.

Veroboard doesn't snap along hole lines reliably, but that stuff is more like 1mm hole and 1.54mm bridge, but drill out every second hole in a line to 3mm (1/8") and see what happens.

It's not really in the budget to do four sides of ten boards manually for a total mfg cost under $5, even if the teacher does it. I think it's better that I just mostly-route and ignore the hazard of exposed fibres