A - Remove the "chip" from the circuit board. This can be with 30 to 40 seconds with a heat gun and prying the chip from the board with a box knife.
B - Cut extraneous material from the sides of the chip. I use a Dremel cutting disk. This reduces the amount of work the Nitiric Acid will ave to do.
C - Dissolve the epoxy package surrounding the chip. Ideally you could do this with 90% plus Fuming Nitirc Acid, which is almost impossible to obtain to a private user. So I have to setle for 70% Fuming Nitric Acid.
I have done a number of experiments of ways to increase the activity of 70% Nitric Acid for my purposes. I started with coffee cup warmers, but the temperature was ineffective. Then I went to gravy warmers. The temperature was higer and vey effective, but the condensate dissolve the top of the warmer.
This is my present slow cooker, and it works very well--
This is a consumer gravy warmer available at store such as Bad Breath and Beyond. I have put a dish on top of the heating plate to protect it from the Nitric Acid condensate which woul dissolve the heating plate ofthe warmer.
On the heating plate is a beaker in which the Nitric Acid and the "chips" will be positioned.
The "dome placed over the beaker will 1)prevent heat from bleeding off the beaker and 2) conserve heat, thereby increasing the efficiency of the activity of the Nitric Acid.
As the dissolving process continues, the "chips" may be taken out
of the beaker to have some of the epoxy capsule brushed away. I have found a quarter inch SYNTHETIC artits brush is ideal. "Hair" brushes are dissolved by the acid.
It is important to wear rubber gloves through all of these steps since even the fumes of Nitirc Acid can "tan" your skin.
You may have to dump and refresh the acid over a day or two to totally clean the chip.
I have confined my work area to a 16x20 inch darkroom tray. I have desktop fan to blow the fumes away and keep my setup in my garage with the door open.
Michael Reese Much FRMS `EMS
