Etching your own Prototype PC Boards

PCB etching is as simple as immersing it in the etchant solution and agitating it to keep sludge from inhibiting further etching. This can be done in plastic or glass trays, vertical etching tanks, or spray etchers. The goal of all of these methods is to dissolve all of the exposed copper and leave all of the unexposed copper. The difference is throughput.

Etching your own Prototype PC Boards

A hobbiest is most likely to use a tray or a vertical tank, so I will concentrate on those. In both cases the method is to have the printed circuit board entirely covered by etchant, and agitated to keep fresh etchant in contact with the surface. See the page on etchants for differences between them.

Tray Etching

Tray etching can be approached from two directions. The first is to completely cover the printed circuit board, copper side up, and rock the tray to keep the etchant from saturating directly over the surface of the circuit board. Another way is to suspend the circuit board copper side down, and let the etching turbulence and gravity move the loaded etchant away from the printed circuit board. This method may etch faster, and more evenly, but it is difficult to see the progress. Either way is suitable and very easy to do. I think everyone gets their start on the first, and some eventually go to the second. I didn't, because I want to see it in case there is trouble.

The PCB etching process will go more quickly if the (FeCl3) PCB etchant is heated to slightly less than 55°C (130°F). There are studies that show the temperature could be as high as 71°C (160°F) while maintaining a linear increase in etch rate with temperature.

Vertical Etching Tank

The tank etchers have all of the benefits of both tray methods, in that you can see the PCB etching, and the sludge tends to drop to the bottom of the tank. The drawback is the amount of etchant typically required to fill the tank. There should still be agitation with a tank, but rocking the tank will to little or nothing to agitate it, and rocking the board requires getting in the etchant and contacting it without disturbing the PCB etching process. Usually the board is lifted into and out of the solution occassionally to remove the stale etchant from the surface. The best solution is an aerator, which solves another problem if you are using cupric chloride etchant - it oxidizes the solution.

Another benefit of vertical PCB etching tanks is the possibility of adding aeration and temperature controls to the tank itself and not rely on external processes, like microwaving the etchant, or rocking the tray. The ideal etcher might be one that includes both heat and aeration, and doubles as the storage tank.

Spray Etching

There are two forms of spray etching. One is done in a tank and one is done on a conveyor. Both are beyond the current scope of this site.