Toner detaches from copper during etching! Help!

[ChildOfVision]

Hi! After laminating (toner transfer method) everything seems fine: toner is very firmly glued to copper - you can scratch it very hard, scrape as much as you want, and even the finest tracks remain intact. BUT when you put the PCB in acid some of the tracks are detached in part or completely leaving unprotected copper at the mercy of acid!!! Why is this happening? THX!

 

[kasamiko]

What etchant you are using?

 

[Boncuk]

Use ferric chloride instaed of sulfur acid.

 

[ChildOfVision]

What etchant you are using?

I'm using HCl + H2O2 .

 

[kasamiko]

try ferric chloride..

i'm using HCL+ hydrogen peroxide with good result...

 

[evaine23]

how are you prepping the copper before you transfer the toner? Have you removed any surface oxidation and oil? How thick are the traces that are etching off, could they be undercut? I've had great results with the HCL + H2O2 and I have to scrub to remove the toner after etching. Try scrubbing the copper with a 3m pad and some dish soap before transferring, maybe some oil from your fingers is causing the traces to detatch.

 

[ChildOfVision]

how are you prepping the copper before you transfer the toner? Have you removed any surface oxidation and oil? How thick are the traces that are etching off, could they be undercut?

First, I clean copper with fine sand paper, then clean (as you said) with dish-soap, and finally, thoroughly clean the PCB with acetone. I don't touch copper (or toner) with fingers at all after that! I will try to attach picture of my test-PCB:

**broken link removed**

On the left is PCB after laminating and cleaning with an old toothbrush and dish soap - as you can see all traces seem to be firmly "glued" to copper. On the right is PCB after etching (pic. isn't too good I know) - there you can see U-shaped trace (width 0,2mm (8 mils)) that is completely etched (because the toner fell off), while, surprisingly, very close neighboring traces of the same width reamained intact!? That's why I would exclude contamination od copper in such a narrow and long path. You can also see a fraction 0,4mm (16 mils) trace that is detached.
Note the rest of the PCB (on the lower part): traces of 0,15mm width (only 6 mils!) that pass between SMD-IC pads and 2 traces (of the same width) that pass between normal IC pads remained properly etched! So, I will also rule out undercuting. Furthermore the pitting is minimal.
Therefore I wonder why toner did not fell off during the very intense (even aggressive) cleaning, if it was not well sealed or dirty???
(sorry for my poor english!)
PS: I don't see the link for picture, I don't know why... Well, it's OK now!

 

[evaine23]

I don't know if its possible, but can you increase the dpi or the toner darkness of your printer? I do see small pits in the large areas of copper that might be due to small holes in your toner mask. I try and print with my printer set to 1200x1200 with the darkest toner setting. Maybe your running low on toner and even though it's seems to have transfered properly there are small holes to let the acid though. How are you removing the paper after transferring the toner to the coper? Have you tried to use a different type of paper? I was having substandard results until i switched to some hammermill color laser gloss paper. I typically run it though my laminator 10 to 16 times rotating the board every few passes. I remove the paper by soaking in warm water and swirling lightly. The paper normally floats off and I etch from there without any scrubbing. Also you said you use the HCL and H2O2 etching method, what ratio are you mixing these two chemicals together and what are the concentrations of each. I use 28% HCL and 3% H2O2 and i believe i use 1 part HCL to 2 parts H2O2. If the mix is wrong i apologize, I reuse my etchant and only add a little more h2o2 as i go.

 

[ChildOfVision]

I don't know if its possible, but can you increase the dpi or the toner darkness of your printer? I do see small pits in the large areas of copper that might be due to small holes in your toner mask.

Hi, evaine23! I'm using Samsung ML-1640 with 600 dpi and "economy mode" off. This printer has also 1200 dpi capabilities, but i don't see any differences in final result. Toner is far from exhausted (almost new). As for pitting the PCB looks a lot better in reality than on this really bad picture. For example, larger area of copper on the bottom of the PCB has no pitting at all - what you see is just dirt from my fingers. Yet, there is some pitting in central area.

How are you removing the paper after transferring the toner to the coper? Have you tried to use a different type of paper? I was having substandard results until i switched to some hammermill color laser gloss paper.

I tried different types of paper, except inkjet glossy paper. So far proved to be the best is gummed paper that I used in this test. It is dextrin coated paper like Pulsar's "Toner Transfer Paper" (like mail stamps) that accepts toner very well. After laminating dextrin is easily dissolved in water leaving pure toner on copper without paper residues! Paper that I use is a cheap children's collage paper with these water activating coating. I intend to try also laser glossy paper, but it is very hard to find it cheap where I leave.

I typically run it though my laminator 10 to 16 times rotating the board every few passes.

If you can please tell me what kind of laminator you use (I use GBC brand)!

The paper normally floats off and I etch from there without any scrubbing.

Does this mean that you do not have grayish paper residues with this (laser glossy) paper?

...you said you use the HCL and H2O2 etching method, what ratio are you mixing these two chemicals together and what are the concentrations of each...

What ratio - I really have no idea. I do a very roughly mixture ("judged by eye") of 20% HCl and 12% "pharmacy purity" H2O2 without additional water. Ratio is maybe 5 parts of HCl to 1 part of H2O2.
And to add at the end, I have a habit of first pour the HCl into the pan, then put the PCB inside, and then add H2O2 over all, while the reaction starts. Maybe then some harmful reaction appears? It seems to me that detaching of toner starts when i add H2O2, BUT I'M REALLY NOT SURE! I tried to put the PCB separately in HCl and H2O2 and nothing happened.

 

[evaine23]

The laminator I use is a PL100 seen here **broken link removed**. Its sold under many different names, but if that is the one you have, I use the foil setting.

Does this mean that you do not have grayish paper residues with this (laser glossy) paper?

My copper is probably a bit dull from the clay (or whatever it is they use to coat the paper) being left behind, but it doesn't seem to affect the etching.

I think i normally use 1:2 HCl:H2O2, but your H2O2 is much stronger than mine. After doing some searching it looks like some people are using up to 35% H2O2 so that might not be a problem even though that is the oxidizing agent.

I don't have too many more ideas unless you start swapping out elements and see if something works. Could you be cutting the boards too aggressively possibly separating the copper from the PCB before you etch. Are you taking the board out as soon as the etching process is complete or leaving it in for an extended period after it should have been complete. I suppose you could try a different source of copper clad or try some standard 3% H2O2 but that shouldn't be the problem.

If you want to try a new type of paper look for the cheapest glossy laser paper you can find and that should just float off after soaking.

Also like some others suggested, maybe try a different type of etchant to see if thats the problem.

 

[ChildOfVision]

@evaine23: thank you, pal, for your suggestions. I will consider them carefully and report results! Just one thing: you have not mentioned how prominent is pitting with glossy laser paper (if any). So, please, when you catch the time, let me know about this! Bye!

 

[evaine23]

I rarely see any pitting using the glossy laser paper, but I don't normally have large ground planes where they would be a little more obvious. I think the pitting would be caused by small pin holes in your toner mask. After removing the paper, I never see any toner remaining so I suppose at that point it just depends how heavy and uniform your pattern was printed. One other thing you could try if you think pitting may be an issue is to coat your traces where possible with a sharpie perminant marker. I used to draw my pcb's by hand using a marker and it does provide some decient protection from etching.

 

[kasamiko]

I totally agree...using large plane and some pitting will be visible...

here using muriatic acid and hydrogen peroxide as etchant with good result...

**broken link removed**
**broken link removed**

 

[ChildOfVision]

Has anyone tried to expose the PCB (with toner on it) to vapors of nitro-thinner (or similar), as it does with templates for photo-process, in order to get leveling of toner and thus sealing of pores???

(hope, you will understand my ugly english )

 

[kasamiko]

nitro-thinner <<<<<---- What is the common commercial name of this chemical??

 

[ChildOfVision]

Well, I really don't know what is commercial name of "nitro-thinner" in other countries, but this should be very usual chemical everywhere! I tried to "google-translate" this word and I only get "nitro-thinner". I found this definition on the web page of manufacturer in my country: "Universal NITRO thinner is a mixture of organic solvents. It is used for thinning nitro and similar coatings, degreasing of metal prior to coating application and for washing tools". It is synthetic thinner for all kind of paints; it consists of "mixture of aromates, esters, alcohols, ketones, and aliphatic carbohydrates". It is colorless, yellowish, clear liquid with very strong smell. It is very volatile, and therefore can be used for exposure of the toner on a transparent film (for photo-method) to its vapors (in a sealed metal box, with a little thinner on a piece of cotton, without direct contact with thinner)! Toner then becomes darker and less transparent!
I hope this is helpful!

 

[kasamiko]

Is this same as LACQUER THINNER?

 

[ChildOfVision]

Yes, I'm 99% sure! Look at wikipedia under "Lacquer thinner" - there says: "Lacquer Thinner is usually a mixture of solvents able to dissolve a number of different resins or plastics used in modern Lacquer. ... Twentieth-century lacquer thinners frequently contained alkyl esters like butyl or amyl acetate, ketones like acetone or methyl ethyl ketone, aromatic hydrocarbons like toluene, ethers such as gylcol cellosolves, and or alcohols." And look at the composition which I gave: "mixture of aromates, esters, alcohols, ketones, and aliphatic carbohydrates" - (I wrote "aliphatic carbohydrates" instead of "aliphatic hydrocarbons" which is the same)!!! Therefore, "nitro-thinner" is the same as "lacquer thinner" (99,9% )!

 

[evaine23]

I've never tried it myself, I would think that would help with pinholes in your toner mask but i'm not sure how that would help for traces that just lift off. I don't remember if you mentioned it or not, but how do you cut your pcb before etching? Did you say you saw the toner detach from the copper while etching or if the copper being etched out from under the toner and then the toner falls off?

 

[3v0]

When the toner does not stay on the PCB nost of the time the problem is that the laminator is not getting hot enough.

You could also try hitting the PCB with 600 grit sandpaper to give the toner a better surface to stick to.

New cartridges provide more toner and help prevent pin holes. Using a hatched pattern for a pour (eagle has this) can help. You can get a green foil from pulsarProFx.com that is laminated to the top of the toner to seal pin holes. (not missing spots of toner)

Last keep you fingers off the PCB surface after cleaning to prevent transfer of body oils.

3v0