There are four main methods of removing gold from circuit boards, each with its pros and cons. The most effective, and most time-consuming, method is scraping with a device like a paint scraper. The amount of gold collected using this method is greater when compared to other methods. The aqua regia technique is also an efficient method but is not popular because it involves the use of concentrated hydrochloric and nitric acids which emit highly corrosive fumes and require very careful handling. The CBX method and the StripFree method are most commonly used.
Put on rubber gloves and eye goggles. Combine one jar of CBX circuit board stripping powder with water in a large, deep container to prepare 1 gallon of solution.
Dip the edges of the circuit boards in this solution and allow to stand for six to eight hours. Remove the boards from the solution and rinse.
Filter the solution and collect the flakes of gold that have detached from the boards.
Cut a square piece of stainless steel screen smaller than the inside of the plastic/glass pan. Position the screen in the bottom of the pan. Fold one side of the screen upward so it is projecting a bit over the pan top.
Insert as many circuit board parts and chips as possible into the lower part of the screen in the bottom of the pan. Align the parts such that the chip legs face upward through the surface of the screen to display the gold squares on them.
Hang any conductive method above the pan containing this assembly; it will function as a cathode. Do not use metal for the cathode as the gold tends to stick to it. Connect the red wire from a battery charger to the topmost part of the bent area of the screen projecting out of the pan. Connect the black wire of the charger to the cathode.
Transfer a sufficient amount of StripFree into the flat pan to totally cover the circuit boards.
Switch on the battery charger. As the cathode begins bubbling, the gold starts softening and dissolving into the StripFree and then slowly starts collecting on the surface of the cathode.
The CBX solution is highly acidic -- use rubber gloves on your hands and protect your eyes with goggles while using it. The use of this method should be restricted to the edges of circuit boards. In the other portions of the board, the CBX solution is used up to dissolve other metallic parts that may be present. In the StripFree method, avoid using a cathode made of metal -- it will bond to the gold and separating this is an additional step in the gold recovery process. To view the level of current required to separate the gold, use a battery charger that has an inbuilt ammeter. Using StripFree is economical because the same solution can be reused time and again until it gets contaminated.