This is coming from a beginner that uses the HCL/Peroxide method. You have much to study and re-read if you have already read. (I'm not insulting you btw, just a friendly tip is all). First, any board you plan on removing gold from MUST have the solder/lead/tin removed. Remove anything manually you can from the board i.e. capacitors (they have aluminum), flatpacks, chips, etc. Yes it's labor intensive and a pain in butt but if the gold is what youre after then thats what you need to do. I did the same thing when i started btw. What i had was a mash of gold with all kinds of surface mounted components and junk, Thought i was doing it right(didnt read enough)
. Upon precipitating my gold, to my dismay, I had black powder and nothing in mass compared to what I put into solution. Oh yeah I was dismayed. Then i learned more by studying. So here's the tips I'll give you that I have learned and if they are wrong I'm sure someone on the forum will call me out. (which is constructive criticism and I don't mind). I'm all about the learning. When you tried to ride a bike did you fall? Probably, but after a few tries you got it. The same applies here.
1) Scratch the greenstuff on the board(solder mask) See if it glints like gold. It comes off easier than copperclad boards do. a jewelers flat blade screw driver is good for that.
2) Remove any or all components you can by hand or use alternative methods presented here in the forum. Save your chips and pins in separate jars to accumulate over time until you decide to learn those processes. Pins, Chips, Processors, fingers, and boards all have different processes to use for the best yields. Make sure you remove any steel/aluminum/tin components or flashing prior.
3) if "said" board contains gold under the solder mask, look up Removing solder mask. (scratching it off is a waste of time) You will find lye is the answer for that.
4) Once all the components have been removed its time to remove the tin/solder/lead. Use straight Hydrochloric acid and immerse your boards. Your gold plate will appear as if it dissolved off or even black. This is a common reaction at this stage. It rubs/washes off. (I freaked out the first time) about a day or so depending on temp.
5) Remove the boards from the HCL and see if the surface mounted chips come off easily by hand or a toothbrush. Let them (components) stay in the hcl for further processing later. (just dont introduce aluminum or steel in the mix).
*6) Now for the beginning stage of recovery.
7) Make sure all boards are clean of ANY surface mounted items. Place your boards in a Very Clean glass container. Add your HCL and just a bit of Hydrogen Peroxide. When I say a bit i mean just a small amount. a couple splashes to get things started. Your solution will turn an emerald green color over time. This is the copper being taken into solution and this is good! Remember that your HCL/H202 solution will take in some of your gold in the beginning of the process but as copper is absorbed it will precipitate it back out in the form of black powder.
8) if your solution turns brown it lacks oxygen in the solution. A few dashes of peroxide will remedy this...or a bubbler.
9) You will start seeing gold being lifted off and floating...thats a good sign. Just keep your solution Green.
10) Once your boards are barren of gold remove them by spraying them down one by one to remove any gold trapped on or in them. Once your solution is free of the boards you can now allow your solution to settle and pour it off into another container (with a funnel and filter to catch anything floating). This was the easy part. The rest You need to study up on if you havent done so already. just don't go walking into this blind. It's more difficult than you think. Also dont forget to learn about stannous chloride to check your solutions for the presence of Gold and other PM's.
If I have missed something in these processes or have erred in some fashion, please point it out to me. I'm far from perfect but learning