In a message dated 97-10-04 11:33:10 EDT, you write:

>1.  What would the advantage be of using both chemicals?  Cost savings don't
>seem to be too likely, since you are replacing one chemical with another.
>
You use much less Sodium Hydroxide (NaOH) than Sodium Carbonate (Na2CO3)

>2.  What are the potential dangers of using sodium hydroxide in a developer?
> What effects could it have on photoresist?
>
The REAL problem is that you do not use enough water.  Or in other words,
Sodium Carbonate is real cheap, and the real goal here is to keep the
dissolved resist concentration in the developer down.  Using Sodium Hydroxide
really means that you use less Sodium Carbonate solution, and thus the
dissolved resist concentration becomes unacceptably high, thus cutting the
quality of developing.

What we are really talking about here is saving a few pennies, and noticably
cutting into the quality of developing, this does not sound like a good trade
off, when we are talking about creating rejects in expensive parts.

>3.  Does the addition of sodium hydroxide cause bicarbonate to be converted
>to carbonate?
>
Yes, exactly.

 NaOH      +   NaHCO3    ---> Na2CO3   +  H2O
Hydroxide +  Bicarbonate     Carbonate + Water
(Could this be called "Cyber chemistry?)

>4.  How many people are using this type of system in production?
>
A few of my customers have tried it, all, that I am aware of, are now back to
using straight Carbonate.

A good idea, in theory, a less than wonderful idea in practice.

Rudy Sedlak
RD Chemical Company

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