| previous by date | index | next by date |
| previous in topic | topic list | next in topic |
Thanks very much for the Info! A rotary type would also be cheaper to realize, so If I get to build one then I will probably go for a rotary tube one.
Toner transfer is easy to do and cheap, so far I am satisfied with my results I dont have a very high faliure rate.
Photoresist would be another thing to have a look at. PCBs you can get precoated but brass copper and german silver sheet does not come precoated. But there are some Photoresist films out there like pureetch , z-acryl, Image-on and the like. These would surely be easier to apply than coating with laquer. I will have to do some research on these. AFAIK real photo negatives work best as a mask for exposing, I have read in passing ,but with no real focus on this kind of topic, that there could be some problems with laser printed masks not dense enough, but surely this could also be solved.
While reading on some older patents on etching machines I stumbled on something only briefly mentioned, apparently they used a small amount of oil in the etchant (how much and what kind etc was not specified(just : "as known to those familiar with the craft" etc etc.) to lessen the undercut. The oil would cling more firmly to the walls of th etched grooves slowing the etching there while being washed away on the bottom of the grooves by the action of the spray. Ever heard of this?
--- In Homebrew_PCBs@yahoogroups.com, <homebrew_pcbs@yahoogroups.com> wrote:Spray etchers (using diaphram pumps) I have seen have droplets not mist.
The point of the droplets is to have some weight behind the impact to move the insoluble precipitate. I would imagine an atomized mist be very ineffective with FeCl3.
If you look on ebay at the ceramic nozzles for sale for spray etchers, they are definitly not atomizing nozzles. They are a fan pattern
The banding I had with the spray etcher was only in early builds before I found the solution to stop it.
As far as etching the bottom of the plate more. With the spray-tube etcher you can actually etch the top of the plate more depending on motor speed. At lower speeds the bottom etches more. At higher speeds the top etches more. Find the "Sweet spot" for your tube and it is pretty even. Better than most nozzle/pump spray etchers I have seen that don't hold the target horizontal.
If you want to build a pump/nozzle spray etcher that does a better job than the rotary tube types you are GOING to have to move the nozzles or the target. As stated above the proper nozzles are a fan pattern. Large professional ones move the target through the machine. Smaller ones (Adam Seychell) move the nozzles back and forth.
WRT the toner not holding up in electro etch. Have you thought about dropping toner transfer and moving to photo-resist. It's a lot more convenient if you are producing the same design over and over again. It also does MUCH better results on long etches (thick brass)
--- In Homebrew_PCBs@yahoogroups.com, <homebrew_pcbs@yahoogroups.com> wrote:"over here" is germany...sry. There are some commercial suppliers for acid resistant pumps but they are not cheap, quite the opposite.
By spray I mean finely atomized with nozzles, the "etchinator" does make some "spray" of sorts but the droplets are much larger than the spray with nozzles and pump. Both methods work, but all the professional Etching is done with the spray nozzle type.
I have heard some good and some bad from the rotary tube type, there is not overly much to find in terms of user feedback but one of the problems reported was banding in some areas while etching and that the lower parts are always slightly overetched due to the etchant running off downwards when the plates are vertical.
This would also be a concern with the nozzle type, some means of constantly moving either nozzles or the workpiece would be needed to etch a larger plate (A5-a4 size) in an even way.
So far a etching machine of either type is still in the back of my head but I was not willing to go thruh the trouble of building one.
I would rather try and make the electroetch work since it seems to produce less undercut than traditional method is cheaper in the long run and it would be much easier to use a setup with two electrodes(Kathode) and the workpiece(anode) in the middle to make some double sided etching.
I am not sucessful because my toner does not hold up in copper sulfate electolyte, it gets gradually eaten away before the etch is finished. If I can find a toner that will work its by far the easier method.