does anyone sell larger presensitized double sided boards then 6x9''?  - Page 1
Forum section: electronics / projects

author: sarepairman2
author_rank: Frequent Contributor
timestamp: September 27, 2015, 06:05:45 pm
content: I want to make my own PCB, fitting my device on a 9x6 PCB is like fitting 10 pounds of shit in a 8 pound bag.Does anyone make 1/16th of an inch FR4 double sided presensitized PCB that is maybe, 12''x12'' or even 9''x9''?And no, I do not want to get a board made. I'm just gonna ignore people that demand I buy a premade one.Why? because I can.I found just copper clad 12x12s. How hard is it to presensitize them?I also found this, but its mysterious as you don't know the thickness or material..http://www.circuitspecialists.com/gd1212.htmlOtherwise I will just make a frankenboard out of 2 6x9's and copper tape/epoxy ribs

author: nctnico
author_rank: Super Contributor
timestamp: September 27, 2015, 06:20:48 pm
content: Back in the old days I recall being able to buy large A4-ish (30x22cm / 12x9") sized boards. If you have a laminator you can apply etch resist yourself.

author: IconicPCB
author_rank: Super Contributor
timestamp: September 27, 2015, 09:58:59 pm
content: I can supply you with a double sided panel, 1.6mm thick in half ounce copper or heavier in a 600mmx 500mm size.Unsensitised

author: sarepairman2
author_rank: Frequent Contributor
timestamp: September 27, 2015, 11:13:18 pm
content: No, I want presensitized, I can get regular copper sheet 12x12'' x 1/16th on ebay.

author: CrashO
author_rank: Unknown
timestamp: September 27, 2015, 11:29:45 pm
content: Search for GC Electronics 21-357If you checkthis spec sheet, they should be Positive Pre-Sensitized double sided 12"x12" boards, with 1 oz. copper (0.0014") on a 1/16" (UL 94V-O)epoxy-glass FR-4 board.A quick google found a few possible suppliers, but since you have not filled out your profile but are using 1/16" instead of 1,6mm, i'm guessing you are from the US.Newark has them:http://www.newark.com/gc-electronics/21-357/pcb/dp/94F4079out of stockOr a lot cheaper here:http://www.onlinecomponents.com/gc-electronics-21357.html?p=11394539Or good ol eBay, although expensive:http://www.ebay.com/itm/GC-21-357-Pre-Sensitized-Positive-Acting-Epoxy-Glass-FR4-Board-Size-12x12-/321221461211

author: sarepairman2
author_rank: Frequent Contributor
timestamp: September 27, 2015, 11:53:56 pm
content: What is positive vs negative? invert the transparencies ?

author: CrashO
author_rank: Unknown
timestamp: September 28, 2015, 12:05:24 am
content: Positive resist will get soft (and get rinsed away) when exposed to UV light. e.g. You can print a `normal` looking mask, where it is black, copper will remain.Negative resist requires a inverted image. Everything black will go away and the parts hit with UV will keep the copper.

author: sarepairman2
author_rank: Frequent Contributor
timestamp: September 28, 2015, 01:10:53 am
content: are they pretty much as easy to etch as the other type?

author: Siwastaja
author_rank: Super Contributor
timestamp: September 28, 2015, 07:06:46 am
content: A bit off-topic, not answerring your exact question, sorry 'bout that, but I'd suggest getting some Dry Film Photoresist (many Ebay sellers selling the official Dupont Riston stuff, used by PCB industry), and a standard office laminator. Then you can use any copper clad and it will be much easier to source in any size you want, you'll also save in the long run. This is because these are standard PCB industry supplies used in large quantities, whereas "presensitized" boards are a niche product for a smallish hobbyist segment.For us (a club), finding the dry film photoresist (which is negative-working, by the way, so you need to "flip" the colors of your mask before printing) was the breakthrough which made the DIY PCB process easier. The yield went from about 70-90% to about 99% - it just works.

author: tautech
author_rank: Super Contributor
timestamp: September 28, 2015, 07:21:00 am
content: This thread's been annoying me since I saw it this morning. Had a look on AliE but must have used the wrong keywords, then I found this:http://www.aliexpress.com/wholesale?spm=2114.01020208.8.56.7uGlMm&initiative_id=QRW_20150928001335&SearchText=pcb+photoresist&productId=32319806163Rolls of resist film.Roll your own.

author: sleemanj
author_rank: Super Contributor
timestamp: September 28, 2015, 07:23:23 am
content: Quote from: tautech on September 28, 2015, 07:21:00 amTake care buying resist film from china that you read the feedback carefully to be sure it's shipped properly, having some clueless reseller fold it up like a sheet isn't unheard of :-/

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: September 28, 2015, 07:43:36 am
content: Up to 510x1150mmhttp://megauk.com/pcb_laminates.php

author: KL27x
author_rank: Super Contributor
timestamp: September 28, 2015, 08:27:05 am
content: QuoteIf you're going to use a laminator, anyway, you might want to give toner transfer a(nother) try.My yield is 99%, typically 12mil/12mil SSOP. Down to 8-9 mil for MSOP when necessary, with no worries. I haven't run into my limit, yet. I haven't needed to go any smaller, even on professionally fabbed boards. But if you're doing 6 mils with UV at 99% yield, I guess if it ain't broke...The main concerns with toner transfer:1. With certain pcb software, certain layer settings will cause a hatchy pattern vs completely solid. Change layers and/or layer colors to get solid patterns.2. Pre etch the board. One difference between UV and toner transfer, is that in UV the mask is exposed AFTER transferring. So the way the UV mask goes on doesn't matter, as long as it sticks. With toner transfer you can get fattened traces during the transfer. Pre etching gives the surface some texture to hold excess toner and when used with a laminator, this practically eliminates fat traces. Pre-etching will also clearly show if your board is clean enough. If you have left oil contaminates, you will see it in the pre-etch and you can avoid wasting time with a failed transfer.3. Use dextrin coated paper for the best results. No fibers, no fuss.4. Shoot the board with a heat gun while it's going thru the laminator.5. Don't run thin traces alone. The thinner the trace, the thinner the space between it an the next trace and/or plane. 12 mil traces, keep spaced to 12 mil max. 8 mil traces, space to 8 mils, etc. This is important for the etching to occur, evenly.I don't wash the copper clad with solvents. I don't use gloves. I just wash the board with stainless steel wool pot scrubbers and dish soap on a cutting board in the kitchen sink. Then rinse. Then pre-etch, rinse, dry with heat gun. Double-sided boards are no problem. I drill some landmark holes in the printed transfers. Transfer one side, drill thru the copper clad, then line up and transfer the second side. I never have any problem with the second transfer despite mild handling of the board.