Cutting pre-sensitized PCB - Page 1
Forum section: electronics / projects

author: Harvs
author_rank: Super Contributor
timestamp: February 24, 2014, 08:43:18 am
content: I'm referring to the Kinsten pre-sensitised PCBs while they're in their unused state (i.e. plastic overlay still on.) e.g.http://kinsten.co/pcb/gd/At the moment about the best thing I've found is a large set of aircraft metal shears which cut the 0.8mm board easily. The downside is they rip about a cm of the photoresist off each side of the cut. It's ok, but leads to quite a bit of wastage (if you only need a 50mm square board you've lost more than that to the ripping of the resist.)I've also tried scoring with a blade and breaking, which didn't work much better.Anyone have any better ideas?Anyone know how they cut these in the factory while preserving the photoresist right to the edge?

author: Psi
author_rank: Super Contributor
timestamp: February 24, 2014, 09:12:05 am
content: Bandsaw or scrollsaw.You can get small hobby ones, i think dremel make one.If cutting double-sided PCB you might want to put a piece of something on the underside so it doesn't get scratched while moving it on the saw.

author: Harvs
author_rank: Super Contributor
timestamp: February 24, 2014, 09:18:14 am
content: Yeah it's always double sided.Dremel make a scroll saw if that's what you mean?Are you sure that's any better though WRT not ripping up the resist? Would you leave the protective layer on while cutting?

author: Psi
author_rank: Super Contributor
timestamp: February 24, 2014, 09:19:32 am
content: Yeah, the dremel scrollsaw is what i meant.Yes, i would leave all protective layers on while cutting.With the correct blade type in the scrollsaw you should be able to get a nice cut finish.(I know with my jigsaw the blade makes all the difference between a rough and clean cut finish)

author: BravoV
author_rank: Super Contributor
timestamp: February 24, 2014, 09:20:08 am
content: Credit goes to Alan (w2aew)

author: sleemanj
author_rank: Super Contributor
timestamp: February 24, 2014, 09:33:04 am
content: Quote from: Harvs on February 24, 2014, 08:43:18 amI think that scoring and breaking is your best option for a clean cut, but you REALLY have to score fibre based boards DEEP, and you must do it on both sides. I bought some "hook knives" from China, this is the knife that the taobao vendors etc use to cut up blanks, and it does work pretty well (when I can find it, when I can't I just resort to a normal craft knife, but takes more scoring passes).Start the score with the tip, then switch to the hook and rip it down. Clamp the pcb with a ruler along the score line. Also works good for acrylic sheets.(NB: I haven't tried cutting board with resist already on it, so no idea how cleanly it cuts in that situation)I see there's a couple on eBayhttp://www.ebay.com.au/sch/i.html?_from=R40&_sacat=0&_nkw=pcb+hook+knife&rt=nc&LH_PrefLoc=2Or... get yourself some dry film and laminate the board after you've cut it :-)/Aside: resin type boards (phenolic) are so much easier for the hobbiest, score score snap done, and much easier on drill bits, one of these days I'm going to see if I can track down double sided phenolic.

author: Harvs
author_rank: Super Contributor
timestamp: February 24, 2014, 09:38:50 am
content: It's really keeping the photoresist intact that I'm trying to get at. Scoring and snapping PCB material works fine, but it does tear the resist very easily.A quick price check of the local hardware store shows it's a similar price to buy a proper scroll saw than one of the dremel attachments, so I might just go and do that. Then I can use it for other things as well.

author: AlfBaz
author_rank: Super Contributor
timestamp: February 24, 2014, 09:42:54 am
content: Quote from: Harvs on February 24, 2014, 08:43:18 amI use Kinsten boards exclusively and have to say I get good result just scoring the board with a Stanley knife and a new blade. I cut from the copper side without removing the plastic protective sheet and run it through multiple times so you are not having to snap to much fr4. Holding the board over a nice sharp edge and pushing down on the board with a steel rule right on that edge makes it that little bit easier.A flat 2nd cut file then makes short work of the remaining ruff edgesSome things don't always work out perfect the first time you try them but repeated attempts help you get "the knack"

author: Psi
author_rank: Super Contributor
timestamp: February 24, 2014, 09:53:04 am
content: I couldn't resist making this

author: AlfBaz
author_rank: Super Contributor
timestamp: February 24, 2014, 10:09:20 am
content: @ PSI

author: Harvs
author_rank: Super Contributor
timestamp: February 24, 2014, 10:12:30 am
content: Quote from: AlfBaz on February 24, 2014, 09:42:54 amOk you're right, it does work fine. I mustn't have had a sharp enough blade or something last time I tried it.This time I use a new blade, then on the start of each new cut I touched up the blade with a diamond file so it was sharp as new. Just broke down a 300x150 into 100x75mm without any tearing.Thanks for showing me the error of my ways...

author: AlfBaz
author_rank: Super Contributor
timestamp: February 24, 2014, 10:18:34 am
content: I'm just happy I'm not the only one using kingsten

author: Harvs
author_rank: Super Contributor
timestamp: February 24, 2014, 10:25:58 am
content: Quote from: AlfBaz on February 24, 2014, 10:18:34 amI just ordered their exposure box. Kind of hurt shelling out that much for a light box, but I've heard good things, and it would have paid for itself on a job a few weeks back.Shame though that they're getting rid of all their Australian stock and it'll all come from Asia now.

author: AlfBaz
author_rank: Super Contributor
timestamp: February 24, 2014, 10:30:34 am
content: Quote from: Harvs on February 24, 2014, 10:25:58 amI have one, it's excellent bought it 10 to fifteen years ago from WA. Just tried theirshortcutin my Favourites and its gone

author: Harvs
author_rank: Super Contributor
timestamp: February 24, 2014, 11:11:48 am
content: Quote from: AlfBaz on February 24, 2014, 10:30:34 amMust have been a little while since you ordered from himThis has been the website for a while:http://www.kinsten.com.au/He's got deals on all the remaining PCB stock, then we have to order throughhttps://kinsten.co/their international store. I guess it's just the economics of it all.However, it's not like it's not going to be available, we'll just have to add a few days extra for postage.Can I ask what you use for developing in? Anything special? It's the only part of the process now which I don't have the "proper" tool for (I just use an old piece of tupperware.)

author: AlfBaz
author_rank: Super Contributor
timestamp: February 24, 2014, 12:58:54 pm
content: I usedtheir developer and their etchant.I also boughttheir plastic etching tankscomplete with heater as I couldn't find anything in the fish tank heater range that could be easily modified to get the heat required. They also sell the air pump but I scored one from an aquarium shop.I'd set up both tanks running from the same pump, one with the developer and one with etchant and the heater. The air pump is a must for agitation unless you want to stand there and shake the tankIf you use an inkjet or bubble jet printer a good trick to prevent the artwork from sticking to the pre-sensitised surface is to coat the art work with talcum powder which gives you the added bonus of making the artwork nice and opaque giving you a much better yield for fine tracks. I'd sprinkle it on straight after printing whilst the ink was still wet that way ehe talc would stick to the wet ink

author: AlfBaz
author_rank: Super Contributor
timestamp: February 24, 2014, 01:02:50 pm
content: Quote from: Harvs on February 24, 2014, 11:11:48 amThere use to be this cool little electronics store here in Wollongong called Vimcom. I'd get the PCB's and chems from there. They were the ones who gave me the contact details of the supplier in WA.

author: Harvs
author_rank: Super Contributor
timestamp: February 24, 2014, 01:41:46 pm
content: Quote from: AlfBaz on February 24, 2014, 12:58:54 pmThat's an interesting tip for the inkjet. At the moment I'm just using a laser with the Kinsten paper base. It's not that great, when you have areas of high density (e.g. ground planes), the laser printer doesn't apply enough toner. I don't know enough about laser printers to know what the deal is, but it seems to be a consistent thing with a number of printers I've tried.So yeah, considering how cheap inkjet printers are to buy I'm considering getting one to try out.

author: AlfBaz
author_rank: Super Contributor
timestamp: February 24, 2014, 02:45:15 pm
content: Yeah the lack of opaqueness in the artwork was always a problem regardless of what type of printer I used which meant you had to be very careful with exposure times. I tried the talc to prevent the artwork from sticking to the PCB, that box your getting as a vacuum pump that sucks a plastic film over the pcb/artwork sandwich. I was quite elated to find that it also solved my opaqueness problem