Panelising PCB's - Page 1
Forum section: electronics / general

author: mrpackethead
author_rank: Super Contributor
timestamp: September 05, 2019, 04:05:03 am
content: Tiny PCB's are difficult to work with and handle.. And while you can get tiny pcbs made, there is no economic benefit in making them smaller than 100x100mm, as pcb fabs on the whole use 100x100 as their smallest chargeable unit.So, I think its better to take a little time and panelise them.This is a little board i made the other day, and it demonstrates what I often do. This panel is 100x100mm* Each corner of the panel has a R2 concave cut into it. That provides a place for my Stencil printer to key into. Four pins and we are done. If you just leave straight edges it is easy for the pcb to move around.* A 3mm tooling hole is on the bottom two corners, 5 mm in from each corner. Thats there for my PNP line, it has a pin that will come up, and hole the board on the conveyor.* 2mm slots are used to route out around the pcb, and then mouse bites are set up so, the break point ends up inside the main outline of the pcb. If you have a case or similar, this means you dont' have another proecess to clean up the break point.* You'll note that the tab routes go right across the width of the full board. This means we can easily break off the left and right parts first, the the top and bottom, and then seperate the pcbs after assembly. This is somethign people often forget to do.. In this case probably could have got three pcbs on the panel, but this is a prototype and i only need a few.The general concept works well for scaling up to production panels.

author: Styno
author_rank: Regular Contributor
timestamp: September 05, 2019, 09:50:53 am
content: Thanks for sharing that.Our old pick and place would have serious trouble identifying those fiducials that are partly buried in mounting holes. Does that work well on yours?The large amount of unused pcb in that panel seems unnecessary to me, even though manufacturers use a larger size for pricing than your pcb size doesn't mean you should claim it just for the sake of it. This just produces more waste and I wouldn't recommend it.The panels I get back from JLCPCB only have a 5 mm edge rail on the X-axis including panel fiducials and small (2 mm, I'm not sure) registration holes. These panels measure about A4 size (+/-20 cm by 30 cm), these use v-scoring mostly and produce hardly any waste material.

author: mrpackethead
author_rank: Super Contributor
timestamp: September 05, 2019, 11:10:14 am
content: Quote from: Styno on September 05, 2019, 09:50:53 amNo problems at all.Quotesmaller panels get more diifcult to process. having a wide margin around the boards ( i'd generally want 10mm ) makes stenciling easier as the stencil stays flat. I have a min width of 65mm to go through my PNP line.. and i need tooling strips of at least 8mm.. I generally make my 10mm.. When i make production panels the waste % goes down a lot of course.Quoteif you can use a 5mm edge, thats great. Not enough for my machinery. my registration holes are 3mm because again thats what fits the line.QuoteI also generlaly make production panels about A4 size, its a sensible size to easyily handle. I used to use vscoring but its problematic,as the stress it can cause on components is enough to cause faults.

author: mairo
author_rank: Unknown
timestamp: September 05, 2019, 11:43:31 am
content: mrpackethead, what is the via size & pitch b/w vias on the mousebites and how much inside from the PCB edge are they located? Do you break them by hand?

author: mariush
author_rank: Super Contributor
timestamp: September 05, 2019, 12:12:10 pm
content: As these boards are rectangular, wouldn't it make sense to just use V-scoring? A few lines on the horizontal over the whole panel, a few vertical lines and you're done. Just gently bend the circuit board to snap them off and maybe optionally have some kind of sanding paper wheel to sand down the edges if needed.If you want curved corners, maybe have them routed? Would take less time to route just around the corners.In this particular case, it seems like you would be able to make 3 holes in the stencil and use 3 short screws or nylon standoffs/spacers or something to center the stencil over the pcb

author: SMTech
author_rank: Frequent Contributor
timestamp: September 05, 2019, 12:27:31 pm
content: As a general rule we only rout & mouse bite when the design requires it due to being a funny shape or having overhanging devices like connectors that would get ripped off if someone snapped a scored board up instead of down.We also like panels around A4 with a 10mm border. Our line doesn't use registration holes as we're not conveyored, but the conveyor option would also likely not require them (I think its more common on older machines). A 10mm border gives you decent piece of unpopulated board to hold onto when required as well as some support during printing prior to the printing area and is more than enough to cover the 3-5mm typically specified by most equipment as required by equipment. You might want larger borders if you have particularly large overhanging through hole parts (e.g BNC or Phono) & use wave soldering, just to make sure pre-heat or the wave doesn't get to them. We can and do handle much larger panels (or rather more typically single boards) but A4 is nice and easy to handle for manual processes as well. Somewhere around 45-50mm is a very common minimum size for all conveyor based systems.A few PCB suppliers seem to add their own registration holes in panel borders and also fiducials, I'm looking at a HX one like that now, its a harmless enough thing for them to do as its clearly unused space. When it can get annoying is if you choose to use them and then find they move batch to batch.The most common fiducial type we use or suggest to clients is 1mm circle, it seems just as reliable as any other, naturally you need to make sure its location not near anything it could be confused with. Like many other systems, when a fiducial is defined a search area is part of the definition as well as tolerances for size. The board I'm building currently has slightly unusual fiducials - a 2mm circle inside a 5mm circle I ginore but the system has no issue finding it. Oddly the customer only used this on a single design, no idea where it came from.

author: ddavidebor
author_rank: Super Contributor
timestamp: September 05, 2019, 03:08:33 pm
content: Quote from: mrpackethead on September 05, 2019, 04:05:03 amHello,That is a REALLY bad example of a panel. Issue I see:the fiducials are too close to other pads to be usable. You should place them on the panelno reason to use mouse bites there where you could have used vslots saving space and hassle separating the boardsthat panel has a 50% surface yeld. That's "you're fired" yeldlack of pass/fail markingkinda square. panels should be rectangular with two side rails, not for.

author: mrpackethead
author_rank: Super Contributor
timestamp: September 05, 2019, 07:49:15 pm
content: Quote from: mairo on September 05, 2019, 11:43:31 am.7mm holes.. ( not plated ), spaced 1.2mm apart. the centre of the hole is offset .2mm inwards from the edge of the pcb. I generallly break them with a pair of flat nosed plyers..

author: mrpackethead
author_rank: Super Contributor
timestamp: September 05, 2019, 07:59:04 pm
content: Quote from: mariush on September 05, 2019, 12:12:10 pm

author: mrpackethead
author_rank: Super Contributor
timestamp: September 05, 2019, 08:11:47 pm
content: Quote from: SMTech on September 05, 2019, 12:27:31 pmMy Yamaha line can be set up not to use them, but i've found its more reliable to use them. the 'spike' that comes up through the hole. ( its a pin thats got a conical end, like a pencil ) is located at the machines absolute zero as well. I'm not sure if its a newer/older thing, Maybe more of a difference between brands..QuoteYes. means fingers dont' go places they dont' need to.... If i need to take a board off teh line for a bit of Manual TLC, after its been placed, but not reflowed.. its deftinaly a good thing.The most common fiducial type we use or suggest to clients is 1mm circle, it seems just as reliable as any other, naturally you need to make sure its location not near anything it could be confused with. Like many other systems, when a fiducial is defined a search area is part of the definition as well as tolerances for size. The board I'm building currently has slightly unusual fiducials - a 2mm circle inside a 5mm circle I ginore but the system has no issue finding it. Oddly the customer only used this on a single design, no idea where it came from.I generally use 1mm circle, and if i can, make sure that there is at least a .5mm pull back of mask.. It gives the machines the best chance of sucess. If i put panel fids on as well, ( i'll do that for produciton panels ), they are generally 2mm circles.. and i also have 1/2mm squares for bad blocks... ( a bad block is a way to tell the machine that you have a X-out pcb in your panel, so you dont' manually have to work around it. For prototype qnty boards, the fabs, never send X-outs.. For production quanties, it saves you quite a bit if you allow X-outs.

author: mrpackethead
author_rank: Super Contributor
timestamp: September 05, 2019, 08:19:03 pm
content: Quote from: ddavidebor on September 05, 2019, 03:08:33 pmQuoteNot an issue at all. Thousands of boards made like this.QuoteSee above. Vscoring comes with a whole bunch of issues in itself.QuoteIf it was a production panel, i'd probably be more like 95%+ This is a prototype panel. It costs no more or no less to make it smaller. Making it smaller makes it harder to handle.QuoteYes, if this was a production panel it would have bad block fids.Quotehaving four sides makes a considerable improvement to the ridgigity of the panel during prodution.. Thats a big help, at both stenciling time and placement. I'm more than happy to have it there. As for square vs rectangule.. Not an issue to me.

author: D3f1ant
author_rank: Frequent Contributor
timestamp: September 06, 2019, 04:43:25 am
content: Nothing wrong with those panels, very similar to what I would do, and for production too. Perfect for prototypes...and you remembered to add fiducialsI rarely make v-scored panels. Unless you have a proper depanel machine, the amount of clearance required to not risk cracking mlc caps makes for much wasted board space if strictly following mlc capacitor manufacturer recommendations.Places like JLC don't charge more or less for routing vs V cut so even less reason pick one over the other.Those of us with own gear know what works for us but that might not work for someone else. It is really important to check the requirements of your particular contract manufacturer. What works perfectly for one might not work for another so check before before ordering your boards.

author: mrpackethead
author_rank: Super Contributor
timestamp: September 06, 2019, 06:50:34 am
content: Quote from: D3f1ant on September 06, 2019, 04:43:25 amYup. jsut looks wasteful when you are making protos like this.. but realistically the difference is whos rubbish bin its going in.QuoteYes. and since we all use lots of MLCC caps, its most definately something to consider. I've also seen a few solder joints get cracked, though thats far less likely.. The other thign, the fabs hate using v-scores on small boards, its just not very easy for them. The route out is already happening. 2mm seems to be their preferred width.Quoteironicy, place your vscores at less than 15mm and you'll get additional charge.QuoteYes. absolutely. I'd hate to be CM. Havingt to deal to non optimised panels for my system would be a pita. And as a customer i dont' have to try to understand what they dont' tell me.

author: lilstevie
author_rank: Contributor
timestamp: September 06, 2019, 07:28:58 am
content: Quote from: mrpackethead on September 06, 2019, 06:50:34 amHonestly I'd make things easier for the CMs I use but they don't like sharing this information soHonestly I'd prefer to just bring it all in house, but there's so much crap out there equipment wise I just don't know what to do

author: SteveyG
author_rank: Unknown
timestamp: September 06, 2019, 07:41:50 am
content: Quote from: ddavidebor on September 05, 2019, 03:08:33 pmI'm with you on those points, I'm also not sure of the logic for the placement for the tabs to hold the PCBs onto the panel.If you're concerned with MLCC capacitors, just orientate them in the correct direction if they're near the edge and rig up a tool for breaking the v-scored PCBs rather than flexing the whole PCB which isn't recommended anyway.

author: jmelson
author_rank: Super Contributor
timestamp: September 06, 2019, 10:19:40 pm
content: Quote from: mrpackethead on September 05, 2019, 04:05:03 amWell, I'm not sure this is true at all vendors. I have made a number of small boards as add-on adapters for various things. the smallest is an adapter for a serial PROM only available in SOIC-8. So, I made a board so that I can plug it into a DPI-8 socket. The board is about 10 x 10 mm. My preferred vendor (E-teknet) made these for a pretty low price in 100 piece quantity.Jon

author: mrpackethead
author_rank: Super Contributor
timestamp: September 07, 2019, 01:00:06 am
content: Quote from: SteveyG on September 06, 2019, 07:41:50 amThats ok, your entitled that perspective. I can tell you that;The fids work just fine. Vslots would potentially damage my board, THe yeild is a non issue, its a prototype, and making it smaller is not going to reduce costs, and it woudl make handling harder. It does'nt need pass/fail, and Removing the end rails, just makes the panel less ridgid. Yes, i'm concerned with the caps, and the requirements would mean, i'l end up makign a bigger board.. which in this case, is not an option.. ( this is a replacmetn board going into somethign that already exsits ).. Becuase parts are so close to the edge, getting any tool in to do depaneling is not so practical either

author: mrpackethead
author_rank: Super Contributor
timestamp: September 07, 2019, 01:01:47 am
content: Quote from: jmelson on September 06, 2019, 10:19:40 pmI should have prefaced that, theres no point in trying to make less than 5 pces in total less than 100x100. Sure you can make lots of the same thing......

author: SteveyG
author_rank: Unknown
timestamp: September 07, 2019, 07:11:38 am
content: Quote from: mrpackethead on September 07, 2019, 01:00:06 amThat's fine, for prototypes you can do what you like. I think the reason you may have had some criticism is you've said this scales up for production panels and presented the panel as a definitive guide...

author: Styno
author_rank: Regular Contributor
timestamp: September 07, 2019, 01:49:10 pm
content: Quote from: mrpackethead on September 05, 2019, 08:11:47 pmYes, our old Dima only has a stop pin + microswitch on the conveyor. When the pcb is loaded the pin sticks up to catch the board and the conveyor runs until the microswitch detects the board and then it's clamped. Having the board not exactly at the same position each time isn't a problem imho, as the top camera is always used to determine position, skew on the conveyor and board size.

author: mrpackethead
author_rank: Super Contributor
timestamp: September 07, 2019, 08:47:18 pm
content: The yamaha can use the pin, or 'edge' clamp the pcb.. Its really just two different ways of ensuring that the pcb does'nt move on teh conveyor after placement begins. It does of course use fids to make the adjustments for where the board has 'ended' up. Routing and holes have some variation in absolute placement.. ( perhaps up to 0.1mm hopefully less. )