Negative photo-resist dry film doesn't stick on PCB! - Page 1
Forum section: electronics / general

author: Tommy1984
author_rank: Regular Contributor
timestamp: August 02, 2017, 05:52:03 pm
content: Hello everyone, this is my first topic and hope I'm in the right place.This isn't my first time with PCB's etching, but, my first time with the negative photo-resist dry film method. The film which I used from eBay China, a really cheap one I know.I didn't use a laminator (because I don't have one), I used an iron. I saw a dozen of videos on YouTube, people used an iron and it went very good. BUT NOT WITH MEAfter the exposure, and when I put my PCB in the developer, the film simply peels off by itself.What I tried up to now:- Different ironing time.- Different ironing temperature.- Drying the PCB in the oven after pressing the film with a roller carefully and getting rid of all the bubbles.Had anyone had some same issues?Any help or tip is very appreciated!Tommy

author: Fortran
author_rank: Regular Contributor
timestamp: August 02, 2017, 05:58:16 pm
content: Did you peel off the protective film?Did you rough up the surface first?Cleaned the copper very thoroughly with acetone?

author: wraper
author_rank: Unknown
timestamp: August 02, 2017, 06:20:34 pm
content: I hope you don't use NaOH as developer. Tell what are you using for developing and concentration. Also if you don't expose it enough it will peel off as well.

author: wraper
author_rank: Unknown
timestamp: August 02, 2017, 06:22:51 pm
content: Quote from: Fortran on August 02, 2017, 05:58:16 pmThis is what should be avoided as much as possible. Surface must be clean and smooth, not rough. If copper is not heavily oxidized, sandpaper should stay away from it.

author: ruffy91
author_rank: Regular Contributor
timestamp: August 02, 2017, 06:29:24 pm
content: Do you see the pattern after exposing? If all peels off you most probably did not expose long enough.

author: M4trix
author_rank: Frequent Contributor
timestamp: August 02, 2017, 06:31:05 pm
content: Quote from: wraper on August 02, 2017, 06:20:34 pmProbably this is the cause.Edit: Besides @Tommy, if you don't have a proper laminator, you should ditch the dry film photoresist. If it's a small PCB volume then better use already presensitized boards. Here is an example of proper applying the dry film photoresist. No air bubbles with this method.

author: Fortran
author_rank: Regular Contributor
timestamp: August 02, 2017, 06:57:45 pm
content: Quote from: wraper on August 02, 2017, 06:22:51 pmReally? I think almost every how-to video I've seen does it.I wouldn't use 80 grit sandpaper but maybe something less aggressive. Like scotch brite.If all else fails.

author: M4trix
author_rank: Frequent Contributor
timestamp: August 02, 2017, 07:52:59 pm
content: I forgot to mention. I had similar peeling off problems but the reason was a nearly expired dry film photoresist. I bought a bunch of sheets from a Chinese supplier and kept some of them almost 4 years in the fridge. All manufactures specify 6 months as shelf life so I thought, heck this stuff probably doesn't work anymore and couple of days ago, I did a exposure test.... it was still 30 seconds like the first day ! I was shocked ! But I noticed it drastically lost its adhesion strength. It easily peels off while developing. After some reading, manufacturers recommend keeping the laminated boards in a dark place couple of hours before exposing it. Tried this and the peeling problem was gone. Anyways in the meantime I got a roll of fresh dry film photoresist and of course, it doesn't peel off unless you use a stripper.

author: wraper
author_rank: Unknown
timestamp: August 03, 2017, 05:12:44 am
content: Quote from: Fortran on August 02, 2017, 06:57:45 pmMost of those how-to don't produce high quality boards. First of all, you unevenly remove a large portion of already thin copper. Secondly, you get grooves under the photoresist. This will result in either unfilled groove or varying thickness of photoresist. Very likely traces will have rough edges after etching.

author: sleemanj
author_rank: Super Contributor
timestamp: August 03, 2017, 02:51:13 pm
content: I use sandpaper, fine grit like 240-1500, works fine. Fine grit will not leave any marks deep enough to cause a problem for the film in diy setting.Sand. Wipe down with acetone, wipe down with water. Get a "spritzing" type travel bottle (i got like 3 for a dollar) and spritz the pcb with a fine mist of water, doesn;t need to be too even. Peel off inside-of-curl of film, lay on the wet pcb, the water helps get it down without air, squish out the water from center out with squeege, or just a paper wad, you can easily lift and reposition. Use clothes iron, warm not hot, 50-70 degrees C, press and iron, until pcb is fully heated, pay special attention to edges. Careful not to overheator blistring of the film will occur. You can test adhesion at this point, failed adhesion can be down to cleaning, or insufficient heating.Allow to cool. Expose.Develop in sodium carbonate or percarbonate 30g per litre, gently rubbing with fingers when it starts to work. If it takes more than 3-4 minutes your exposure is too long (or you forgot to remove the top protective layer aftr exposing :-)). I use an old electric toothbrush to assist, especially with close traces.Now the real trick, re-expose, without the mask for about twice as long, after this second "uv baking" any residue which was left over from developing will be obvious and if necessary you can put in the developer again for 30 seconds to clean it up.Etch.Drill if necessary (drill before you strip, makes it easier to see), and then just before you are ready to start soldring, strip it in an acetone bath for a couple minutes, the resist will literally curl up and die.

author: Tommy1984
author_rank: Regular Contributor
timestamp: August 04, 2017, 12:15:19 am
content: Quote from: Fortran on August 02, 2017, 05:58:16 pmFirst of, thank you for your reply!Yes! I peeled off the protective film, smoothed the copper surface first well and cleaned it with acetone!

author: Tommy1984
author_rank: Regular Contributor
timestamp: August 04, 2017, 12:16:20 am
content: Quote from: wraper on August 02, 2017, 06:20:34 pmFirst of, thank you for your reply!Yes I did expose it with NaOH, was it wrong? I got it in small envelope with the dry film

author: Tommy1984
author_rank: Regular Contributor
timestamp: August 04, 2017, 12:17:56 am
content: Quote from: ruffy91 on August 02, 2017, 06:29:24 pmFirst off, thank you for your reply!Yes I saw it, dark and light blue (or some light yellow if I expose it so long)

author: sleemanj
author_rank: Super Contributor
timestamp: August 04, 2017, 12:23:15 am
content: Quote from: wilfred on August 03, 2017, 10:48:36 pmNaOH is too aggressive, it will strip off the bits you wanted to keep in short order.Sodium Carbonate (or Percabonate/Peroxyhydrate) - aka Washing Soda, as found in pretty much every laundry powder, at about 30g/L is much less aggressive, it gives you a much more workable buffer time between "developed" and "stripped". Also, less hazardous.

author: Tommy1984
author_rank: Regular Contributor
timestamp: August 04, 2017, 12:27:05 am
content: Thank you all guy!So now, can I understand that the problem is with the developer? Is it wrong to use NaOH?( I guess yes, because as soon as I put the PCB in it, the dry film or the UV material dissolves quickly)If so, any recommended solution?Tommy

author: sleemanj
author_rank: Super Contributor
timestamp: August 04, 2017, 12:34:50 am
content: I currently use "Sard Wonder OxyPlus"

author: Tommy1984
author_rank: Regular Contributor
timestamp: August 04, 2017, 12:42:48 am
content: Quote from: sleemanj on August 04, 2017, 12:34:50 amThank you...I'll google it when I'm home, give it a try and give a feedback!Tommy

author: sleemanj
author_rank: Super Contributor
timestamp: August 04, 2017, 12:47:16 am
content: Quote from: Tommy1984 on August 04, 2017, 12:42:48 amIt is nothing more than a common laundry powder.Have a look in your laundry room, or your supermarket's laundry aisle, for various laundry powders, the "whitening" or "soaking" ones, look for the to see if they contain sodium carbonate or percarbonate, almost certainly they do. Often it will be written in a small writing somewhere on the label.In the case of the above Sard product, it's 26.5% sodium percarbonate by mass.I actually just use 30g/L of whatever it is regardless of it's concentration, it's not that critical, so I guess I'm actually using like 8g/L of percarbonate plus whatever else is in there for this product.

author: M4trix
author_rank: Frequent Contributor
timestamp: August 04, 2017, 01:42:11 am
content: or buy Baking soda (sodium bicarbonate ) and bake it in a crumb tray at 100 °C for an hour. It turns into pure anhydrous Sodium carbonate.

author: wraper
author_rank: Unknown
timestamp: August 04, 2017, 10:40:09 am
content: Quote from: wilfred on August 03, 2017, 10:48:36 pmNaOH is used as negative photoresist stripper after board etching. It does not develop negative photoresist, just removes it as flakes. Potassium carbonate (K2CO3) of sodium carbonate (Na2CO3) must be used in correct proportion with distilled water.Don't confuse with positive photoresist where NaOH can be used as developer, but generally with awful results if your process is not extremely tight. Sodium silicate is much better for that.

author: Tommy1984
author_rank: Regular Contributor
timestamp: August 04, 2017, 02:14:29 pm
content: Quote from: wraper on August 04, 2017, 10:40:09 amYou are right!NaOH is used as a developer for positive photoresist!Because I'm new to this method, I just used the envelop which I got with the dry film. The stupid seller on eBay sent it to me and it was labeled ( the envelop which contained the NaOH) as a DEVELOPER!!!!STUPID eBays SELLERS & BUYERS

author: Tommy1984
author_rank: Regular Contributor
timestamp: August 04, 2017, 02:18:35 pm
content: Quote from: sleemanj on August 04, 2017, 12:47:16 amI googled it, but, couldn't find it in a local store. Because I live in Sweden, I found many alternatives (such as Vanish, Clever attack..etc).I'll try to check carefully the label and be sure about the 26.5% of sodium as you mentioned

author: wraper
author_rank: Unknown
timestamp: August 04, 2017, 08:05:50 pm
content: http://www.ebay.co.uk/itm/Sodium-Carbonate-Fine-Powder-100g-Soda-Ash-Light-/290988693403?epid=1788432297&hash=item43c047179b:g:6FUAAOxyg7xSaBA5

author: M4trix
author_rank: Frequent Contributor
timestamp: August 04, 2017, 08:14:28 pm
content: @wraper,what if someone on Swedish customs thinks it's heroin and tries to taste it ?

author: Fortran
author_rank: Regular Contributor
timestamp: August 04, 2017, 08:32:44 pm
content: Quote from: M4trix on August 04, 2017, 08:14:28 pmThen Tommy only have 80g left?I don't see how it would affect a Swedish customs worker.

author: wraper
author_rank: Unknown
timestamp: August 04, 2017, 09:20:01 pm
content: Quote from: M4trix on August 04, 2017, 08:14:28 pmUK is still in EU, no customs.

author: M4trix
author_rank: Frequent Contributor
timestamp: August 04, 2017, 10:06:57 pm
content: Well, seriously, how do on customs know what's the substance inside the package when coming from outside EU or any other country ? Do they justbelieve what's written on the label ? or they simply think... who's that dumb to send drugs over ebay !Any customs worker on EEVBlog btw ?

author: wraper
author_rank: Unknown
timestamp: August 05, 2017, 11:28:57 am
content: Quote from: M4trix on August 04, 2017, 10:06:57 pmThey have dogs to sniff the parcels.

author: Tommy1984
author_rank: Regular Contributor
timestamp: August 06, 2017, 12:45:36 am
content: Quote from: M4trix on August 04, 2017, 08:14:28 pm

author: janoc
author_rank: Super Contributor
timestamp: August 06, 2017, 10:05:28 am
content: Quote from: wilfred on August 03, 2017, 10:48:36 pmSodium hydroxide is commonly used as a stripper for dry resist. I guess it is obvious why that would be a bad idea to use as a developer.Hydroxides are used as developer for the positive pre-sensitized boards, if I remember right, but that is a different type of resist.

author: jh15
author_rank: Frequent Contributor
timestamp: August 11, 2017, 03:51:22 am
content: What is a spritzing travel bottle?

author: jh15
author_rank: Frequent Contributor
timestamp: August 11, 2017, 04:27:41 am
content: what does it spritz normally? I remember as cross country passenger in our station wagon, going through New Jersey we sprayed aerosol deodorizer cans that size on rags to our face to make it through. Lots of oil burning flares etc.

author: sleemanj
author_rank: Super Contributor
timestamp: August 11, 2017, 04:39:28 am
content: Quote from: jh15 on August 11, 2017, 04:27:41 amhttps://youtu.be/mD95BLpEUcE