Problem With etching!

[Warlord_1011]

I made two PCB's around December, and have recently been planning some new ones to make. I went to etch them, and on two separate occasions each with new Ferric Chloride mixture (of the correct measurements), a discolourment will occur and the PCB will turn a tint black, then after a while it sometime hours turns green, or drys to a dark brown. What is going wrong??? i made two PCB's a few months ago with the same HP photo Paper, and the same ratio on the Mixture. Also I have used the same iron, attempted to keep the temperature the same and it still wont work??

Pictures:

(top clean piece of Copper with a attempted etch)

**broken link removed**

**broken link removed**


please help I am wasting materials and i don't know why!!!


By the way, discolourment usually appears within the first 10 minutes, both pictures are after 40 min - 80 min in Ferric Chloride around 20 deg

 

[ericgibbs]

hi,
Look here.
DIY PCB Manufacturing

I would say you are under exposing the PCB's to the UV light, it should not take more than about 15 mins in the Ferric solution to etch away the exposed copper.

 

[Warlord_1011]

I am using the Iron on method

 

[shortbus=]

How warm is your ferric solution? It should be around 100F. What kind of water are you using? Distilled water will give better results than tap water. I found that using a disposable foam paint brush to wipe the copper every couple of seconds helps to etch faster. Or at least keep the solution moving slightly to keep fresh etchant in contact with the copper.

 

[Warlord_1011]

well its room temperature what is about 20 degrees Celsius so 68F, I am using Tap water but its from the same tap all my others have been, unless the water company has changed its chemical composition

 

[QuietMan]

Warming FeCl will speed the process a lot, and give it less time to go wrong. Of course, if it goes wrong it does so faster.

Lately I've been using 2 parts Hydrogen peroxide to 1 part muriatic acid (a swimming pool chemical, 33% hydrochloric acid) with good results. Definitely more hazardous as chemicals go, but it works well.

How I make PCBs

I got the idea for wax paper from Ron, an active member of both sites. He mentioned here just over a year ago.

 

[DirtyLude]

The etchant just isn't strong enough. Heat it, make it stronger, agitate the mixture (you can't just let it sit there in the solution, move it around). Any or all of these things.

 

[DirtyLude]

Just looked at this again and realized I will lightly scuff the top copper with a bit of scotchbrite before I iron on the etch resist. I'm not certain if you do this, but there might be something coating the top of the copper.

 

[jbeng]

After the scotchbrite treatment, I would also wipe it down with a solvent to get any oils off the copper. My solvent of choice is acetone.

With new FeCl solution at about 130F, my etching step is usually complete in about 6-7 minutes.

 

[lilimike]

I normally use about 2 oz of Fe-Cl for 9sq inch of copper, I warm up the Fe-Cl using a 60 watt light bulb for 10 minutes, then I hold the PCB at a 45 angle with one hand (rubber glove) while I wipe it using a sponge soaked in the Fe-Cl, I turn the PCB around after about 30 seconds and wipe the other way and I am done within 1 to 2 minutes.
I used to just leave the PCB in a small bowl with half inch of Fe-Cl, rocked the bowl every minute or so and it was taking about 20 minutes.

I have a feeling if you get the results you showed after 80 minutes you have a contaminated Fe-Cl or it just went bad with time. Not that I've seen that happen though.

Mike