V-scoring and Tab Routing - Page 1
Forum section: electronics / general

author: gnuarm
author_rank: Super Contributor
timestamp: January 22, 2021, 08:45:26 pm
content: I have a board I've produced for years that has two connectors mounted right at the edge of the board. This is an unfortunate requirement as this board is form compatible with a customer's chassis. That is a mistake they made and I have to live with.The problem this causes is the panelization the CM uses is V-scored and the connectors get in the way of running these boards through the machine. So I'm looking for a way to mitigate this issue. I'm actually surprised no one has raised an objection to this. Seems like CMs just grin and bear it a lot of times.It occurred to me that even though they are V-scoring the boards, the part of the outline at the two connectors at issue could be either routed along that portion, or they could at least be drilled around that portion. The drilling (like tab routing without the routing) might be a problem since it leaves a jagged edge and the boards are already a problematic fit even without making the edges irregular. Smaller drill sizes and closer spacing minimize this issue. Anyone know how close they can put holes for tab routing? The smallest drill size on the board is the 10 mil vias which get rounded up by some fab houses to 13 mils.Routing the board outline for an inch near the connectors also is not without problems. I don't know how much the CM spaces the boards for V-scoring but it is not much if anything. The routing bit has a minimum diameter which will cut into the separation of traces/components from the edge of the board. If the board is being redone, this can be dealt with, but I'm not sure how large that minimum route dimension is. I also do not know if an inch is enough length. The separating tool has fairly large cutting wheels. The connector is a bit under 5 mm tall, so I could calculate the required distance if I knew the wheel diameter. I will need to ask the CM about this next time I have their attention.I looked at the JLC capabilities and they don't mention the minimum route width that I found. Anyone know a typical number? Any other ideas? This is not a critical issue as we have made thousands of boards this way, but this is one of the few manufacturing issues I'm aware of and I'd at least like to consider options. With a board respin in the future it is something that should be dealt with as much as possible.

author: Feynman
author_rank: Regular Contributor
timestamp: January 23, 2021, 09:35:07 am
content: Well, I'm afraid the only solution to this is: Talk to your CMOnly you and your CM can bring your respective requirements together.Quote from: gnuarm on January 22, 2021, 08:45:26 pmBoard-to-board spacing is usually 0. That's more or less the whole point of V-scoring.QuoteA 2 mm milling tool diameter is pretty much standard and should not cause additional cost with most manufacturers. Typical milling tool diameters might go down to 1 mm, but are likely to increase cost. Tool diameters < 1 mm will most likely increase cost. Please keep in mind that these are ballpark figures, that depend on the specific manufacturer, of course.

author: gnuarm
author_rank: Super Contributor
timestamp: January 23, 2021, 08:13:58 pm
content: Quote from: Feynman on January 23, 2021, 09:35:07 amYes, but that is a double indirect. The CM doesn't make the PCBs. There are general guidelines as everyone uses the same router bits.Quote from: Feynman on January 23, 2021, 09:35:07 amPossibly. The V groove is not a near perfect cut like a routed edge. Over the years I've run into all manner of guidelines about pushing back from the edge of the board. Since the edge of the V groove is not square, I don't know if they let it eat into the margins or if they let the unevenness extend beyond the defined outline.Quote from: Feynman on January 23, 2021, 09:35:07 amThat's the sort of info I'm looking for. Thanks