Homebrew PCBs

Much of what you need has already been worked-out, and worked  
with.........

How about this bit of detail on a fellows working etch system ????

**********from etch1...

"I also made a tank with a higher-pressure pump, and plastic nozzles  
to spray the ferric chloride onto the sheet, with a clip to suspend  
the sheet vertically in the tank above the surface of the acid. This  
worked much better (about 4 times faster than the circulating tank!)  
and I even had to dilute the ferric chloride about 1:1 with distilled  
water to slow down the etching action. The surface finish was much  
smoother also. But, the etching was "directional" due to the acid  
running off the surface in one direction. I had to keep stopping the  
pump, and rotating the sheet 1/4 turn every so often to even out the  
directionality."...................
"There are two nozzles (equivalent to #H-83251-00 on pg. 1123 of the  
1995 Cole-Parmer laboratory products catalog) in the wall of the tank  
directly across from one another, each fed by an oscillating pump.  
These pumps (equivalent to #H-07101-01 on pg. 1113 of the Cole-Parmer  
catalog) are made for laboratory use, and have all rubber/plastic  
internal parts. Unfortunately, the pumps do not put out enough  
pressure to completely atomize the etchant, but the spray is fine  
enough for the finest etching I do. I can turn each pump on  
individually, to fine-tune the double-sided etching. All plumbing is  
vinyl tubing with plastic fittings and hose clamps."

"A shaft (titanium, to resist the acid, as even stainless steel will  
dissolve in the ferric chloride eventually) comes in the side next to  
one nozzle, so I can hold the sheet in the middle of the tank, and  
turn it continuously while etching. To hold the brass while etching,  
I drill a ~2mm hole near each corner. A four-armed titanium wire  
"spider" with hooked ends engages these holes, and applies outward  
tension to keep the sheet from bowing. The plastic hub of this spider  
presses onto the titanium shaft."

**********from etch2......
"I am using a 300W aquarium heater, built like a long test tube with  
the power cord and temperature adjustment knob coming out a plastic  
cap on the end. Although it is completely submersible, I did not want  
to take chances. I drilled a hole in the side of the tank (adjacent  
to the bypass outlet) and used silicone caulk to seal the heater in,  
with just the plastic head outside the tank. A small plastic bracket  
glued onto the inner wall of the sump supports the other end of the  
heater. It is just a 1/4" thick piece of acrylic with a hole in it."

"The new tank worked very well, but I had two failures where the  
outlet tubing slipped off the barbed fittings, even though I was  
using the nylon "snappy" hose clamps. I replaced all the outlet  
plumbing with 1/2" PVC pipe, glued. I turned up an adapter from PVC  
barstock that plugs into the pump outlet port (duplicating the stock  
adapter) and has a spud to glue into the PVC fitting."

**********

http://www.prototrains.com/etch1/etch1.html
http://www.prototrains.com/etch2/etch2.html

I think he got his titanium from Smallparts.com ...... at least they  
have it for sale.

"This article is ©1998-2007 Randy Gordon-Gilmore. No part of this  
article may be republished without permission. Private copying for  
non-profit-making purposes is permitted, as long as credit is given.  
Last updated: 26 Feb 2007."

Best to ya'
Mike Bauers
Milwaukee Wi, USA


On Apr 29, 2008, at 5:27 AM, Leon wrote:
> Has anyone tried ultrasonics? The cavitation on the copper surface  
> should
> speed up the etching process considerably.
>
> Leon