Homebrew PCBs

----- Original Message ----- 
From: "fenrir_co" <fenrir@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Saturday, June 17, 2006 12:25 AM
Subject: RE : [Homebrew_PCBs] Re: Board Image from Brother Laser printer on 
catalog paper


> --- In Homebrew_PCBs@yahoogroups.com, Robert Hedan <robert.hedan@...>
> wrote:
>
>> ...
>> > aquarium pump and heater can be had at a pet store for those
>> > undertaking a similar but cheaper route.
>> >
>> > http://www.web-tronics.com/lowcosetsysw.html
>> >
>>
>
> I have found that any kind of vertical tank system, the area closer to
> the bottom of the tank will etch faster than the part near the top.
> This is made even worse with a tank with a bubbler. The bottom half of
> the board will be finished, while the top half will still have copper.
> So you have to flip the board around at the exact halfway point to
> make sure it etches evenly. Otherwise you'll have one side majorly
> undercut by the time the whole board finishes. The most even etch I've
> gotten is with a tank with the board face down towards the ground.
> This, of course, makes it difficult to check the progress without
> making a mess.
>
> Even with a face down tank, if you use a bubbler, the board will etch
> faster where the bubbles directly hit the board. Unless you can build
> a system where the air is distributed evenly over the whole face of
> the board, a bubbler is generally a bad idea. A better system would be
> something that agitates the solution without bubbles so that the fluid
> circulates to let fresh etchant touch the board.

I think that is one reason why spray etching is usually used by the board 
manufacturers.

Leon