A lot of small quantity PCBs come individually routed these days, but when they get too small or come in larger quantities, panels can be very nice to have. When you have your PCBs panelized, what’s your preferred method? And why?
We get questions about this reasonably often: “What’s the best way to panelize my boards?” For our shop, we have some guidelines on how to go about it (make sure to follow the specific guidelines from whatever manufacturer is assembling your boards), but the guidelines don’t specify whether you should use V-score or tab routed. That’s a decision left to you.
What if you don’t know? Well, it depends then, but you can easily eliminate a few options. For example, if you have curves in your board outline, you can’t V-score. V-scoring only works in straight lines. With curves or odd shapes, you have to use tab-routed. If your outline is a pure rectangle, V-scoring tends to require less board-edge, so you can get a bit more out of your PCB real estate. But it’s more difficult to deal with on very thin boards and V-scoring leaves a rougher edge after snapping the boards apart.
Two of the key disadvantages of tab-routing are the greater waste area and the nubs that stick out after separating the boards. You can leave the nubs, sand them down or use a clean-up router.
Here’s my take on it: A) If it truly doesn’t matter, use whichever method is less expensive or that you think looks prettier. B) If you have curves or other odd shapes, you’ll probably need to go with tab-routed. C) If your boards are rectangles and you can deal with the less-smooth board edge, go for the V-score.
Tab. Not Diet Coke.
The “V” scored boards can be trimmed apart via a “pizza cutter” machine. The large, round blades will allow a cleaner cut than breaking the PCBs apart.
Likewire, the routed boards, especially those with some straight edge, can use a nibbler-type machine. The blade is as wide as the route, and a notched side goes over the tab. The machine then is actuated and shears the tab away. IF the blade is close to the same size as the route and IF the blade uses good geometry, the shear will be quite clean.
Personally, we have our baords panellised in the tab route form, but we don’t pmass produce PCB units. This approach doesn’t have to end up with a small stud you have to file as you can add mousebites on the edge of the board outline. Once you break the board out there’s only a little bit of mess which is easily dismissed or removed as appropriate.
It seems that V scored panels are used only in big mass production to save on material waste. This is ok but there are a couple of issues:
The term breakout really should be dropped becasue there’s on thing I’ve learned – never breakout out V scored boards by literally bending and breaking as this will almost certainly damage components, indeed I’ve seen them ping off.
The edge is even when cut is rough to the touch which can cause people in manual assembly to get splinters. More seriously the jagged edge allows moisture to get into the baord from the side more easily that routed edges, with serious effect on the circuit operation if this happens.
The key in my experience really is to talk to the fabricator about your requirements and come up with what’s best. But the details should be marked on the master drawing somehow and must never be left to chance!