How to route a circular PCB in rectangular carrier? - Page 1
Forum section: electronics / general

author: SL4P
author_rank: Super Contributor
timestamp: May 02, 2014, 06:44:17 pm
content: Altium ---Can someone please lead me through the basic steps to place the routing arcs needed for a 'pop-out' circular PCB manufactured within a square 'carrier' - that would eventually be panelised with V-scoring (I'm ok with the panel and scoring..?)thanks

author: DerekG
author_rank: Frequent Contributor
timestamp: May 03, 2014, 12:29:12 pm
content: Quote from: SL4P on May 02, 2014, 06:44:17 pmThere are several ways to do this. I have designed circular pcbs for autogas senders in the past & the method I chose was to use three 120 degree arcs on the mechanical layer (just a touch less than 120 degrees actually). Leave just 0.6mm (I'm assuming you are using 1.6mm substrate) between each arc segment. This will give you three "snap outs" for your circular pcbs (which you would cut with a pair of side cutters).You can V-groove if you actually require a square/rectangular pcb, however if you just want a round pcb, do away with the V-grooving all together.Generate the gerbers in the usual way & advise the board shop that the mechanical layer is being used for circular routing. The board shop will advise you their preference for the drill diameter, however 2.0mm or 2.5mm is fairly usual.I laid out the entire panel for them with fiducial marks & panel mounting holes by cutting & pasting 1 circular array, then 2 then 4 then 8 etc.You could do it using "rooms" now if you want.Hope this helps.

author: SL4P
author_rank: Super Contributor
timestamp: May 04, 2014, 09:16:48 am
content: @DerekG - thanksI was probably over-complicating it in my mind !Easy - so simple arcs, and tell the board fab - that's it!(good point about the scoring - it's irrelevant unless needed for some other reason)I expected there may be some 'protocol' to specify arbitrary routing, but your advice suits me perfectly ! thanks again.

author: DerekG
author_rank: Frequent Contributor
timestamp: May 04, 2014, 10:34:16 am
content: Quote from: SL4P on May 04, 2014, 09:16:48 amYes, 3 simple arcs leaving say 0.6mm between them to use as snap outs (if you are using 0.8mm substrate instead of 1.6mm, then increase the spacing between the arcs to 1.0mm to ensure the round pcbs don't break out accidently during handling).No need for any V-grooving if you only want the round circular pcbs. This will save lots of panel space which may mean you get more pcbs per panel.For an ordinary pcb, there will often be no reason to supply a mechanical layer gerber to the manufacturer. As soon as they receive one, they will be saying "what is this for." You will supply a short explanation as to what you want them to do with it & they will then understand fully. Perhaps just confirm first what diameter routing bit they prefer to use (this is important to know if you are laying out the entire panel). On one hand a small diameter routing bit will save board space & produce less dust. On the other hand, there is considerable sideways force on it (they will probably stack up a number of panels to drill & route at the one time) & they must slow down the routing operation (with small diameter routing bits) to ensure they do not break.If you are laying out the entire panel, ask the panel shop if they have any objections to you overlapping the circular arcs between each circular pcb. This will minimise wasted panel space. Once you have their answer to this & their answer to their preferred routing bit diameter, you will be in a position to layout the entire panel with multiple pcbs.If you are using a contractor to load your SMD boards, just check with them if they want any fiducial marks & mounting holes (& their positions & diameters) on your panels.Also check the maximum panel size their SMD robot & infrared reflow oven will accept.

author: SL4P
author_rank: Super Contributor
timestamp: May 04, 2014, 04:00:03 pm
content: Thanks - all good.I place usully 3 fiducials poer panel, and an 8-10mm margin for clamping and tool clearances.Excellent response. Thanks again