Homebrew PCBs

----- Original Message ----- 
From: "Adam Seychell" <a_seychell@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Thursday, April 12, 2007 6:26 AM
Subject: Re: [Homebrew_PCBs] Re: Newbie questions


> Andrew wrote:
>>
>>
>>  > Russell wrote:
>>  >
>>  > I use 10% Na2CO3 sodium carbonate for
>>  > the developing. Unlike NaOH, it's much
>>  > less reactive to skin.
>>
>> Does anyone use sodium silcate?
>>
>> I beleive that is what is in the little
>> packets I get from computronics.
>
> Positive resists use a much stronger alkaline developer, like 1% NaOH or
> Na2SO3. Negative dryfilm resist require a much gentler alkaline like 1%
> Na2CO3. I gave up on positive resists years ago, but been told silicate
> is much easer to use than the hydroxide.

It's actually sodium metasilicate. It has a lot more latitude than NaOH. I 
prefer NaOH because it's a lot cheaper and I can buy it from a local 
hardware shop.

Leon