Photoresist developer

Status
Not open for further replies.

Thread Starter

sirket

Joined Mar 7, 2009
11
I'm loathe to use straight NaOH or KOH as a developer because I would prefer to have a buffer when developing. As I want to be able to use this in a spray etcher I am building, a buffer would be really helpful.

I've never been able to find silicate developer solution so that leaves me with making it as the only alternative (and that's fine- I'd prefer to understand what's going on anyway). That said- can anyone explain the chemical processes at work during developing?

I've read the Moorshead recipe but without understanding what does what- it just seems arbitrary. It seems like a regular NaOH developer with sodium silicate as a buffer and nothing else. Is it that simple? The silica developer sold by Rapid Electronics does not contain NaOH so I suspect it's a very different animal.

Any help would be appreciated.
 

jpanhalt

Joined Jan 18, 2008
9,681
I'm loathe to use straight NaOH or KOH as a developer because I would prefer to have a buffer when developing. As I want to be able to use this in a spray etcher I am building, a buffer would be really helpful.
Welcome to the forum.

The OP for this thread has not been back in awhile. It would probably be best for you to start a new thread on the exact subject that concerns you.

I agree that on the surface, using a buffer has certain appeal for maintaining consistency. It also appears that different formulations of photoresist require different developers. For example, I use Injectorall. It is orange, not green. As a developer, I use 0.4 M KOH. There is quite a window in time (several minutes) between under development and over development.

I have tried several silicate recipes, and could not get any of them to work. The reason is simply that the conjugate acid of even silicates is too strong. Thus, any pH at which there is buffering capacity is insufficient to develop the Injectorall photoresist.

To move forward, you need to know more about the photoresist you are using. Can it be developed in a silicate buffer? Can you think of any other acid that is sufficiently weak to give buffering at the pH needed to develop your brand of board? I considered some of the organic alcohols (e.g., methanol), but did not pursue it as the alcohol might soften the photoresist. Of course, I suspect you want to stay away from oxides of heavy metals too.

John
 
Last edited:

jpanhalt

Joined Jan 18, 2008
9,681
I think you ignored my statement that the chemistry of the different resists is somewhat different. Try the Moorshead formula. If it works for you, use it. I don't see how you can dismiss something like that without knowing details of the chemistry of the resist you are using, which I suspect you do not know. This is not a theoretical discussion.

sirket said:
I've read the Moorshead recipe but without understanding what does what- it just seems arbitrary. It seems like a regular NaOH developer with sodium silicate as a buffer and nothing else.
What else are you looking for? Can you suggest another buffer to use?

John
 

jpanhalt

Joined Jan 18, 2008
9,681
I did not ignore your statement. In fact- I'd like you to elaborate on it. Different how?
1) They are different colors.
2) They differ in photosensitivity based on user reports on this forum.
3) They differ in developer sensitivity. Some can be devoloped with carbonate buffers; others require sodium or potassium hydroxides.
4) Check out this link for a brief review of Novolak resins. Some produce carboxylic acids, which implies greater sensitivty of basic developers than those that produce phenolic residues.

The Rapidonline developer is sold as "Suitable for use with all alkaline developed, positive photo resists and fully aqueous dry film photo resists." My experience has been that every positive resist I've used can be developed with NaOH or KOH. Considering the Rapidonline folks also claim their developer works on all positive photoresists I'm not sure the specific resist chemistry is all that different from one company to the next.
I am not sure what you are trying to say. It either works or it doesn't.

That's not to say I don't care about the chemistry- I do. But blind faith is not what I'm looking for. I'm looking for someone that knows the specific chemical reactions that are taking place and can list and or explain them.
The general reactions are well known. Apparently, you want proprietary information, which you are not likely to get.

I have used it and it does work. I want to know why it works and what it's doing. It starts with Sodium Silicate- and adds NaOH. Does the NaOH just sit there or does it react with the sodium silicate to form a different compound?
Apparently you don't understand fundamental acid-base chemistry.


The Rapidonline developer contains _no_ NaOH and yet still claims to work with all positive resists- why?
Money? I suspect it will not work with Injectorall, unless it is more alkaline than sodium silicate, i.e., has KOH of NaOH.


I'm building a spray etcher and the less accurate I have to be with temperate and time- the easier it is to automate the process. NaOH is still way too sensitive for me right now.
You seem confused between the etching process and the developing process. How much experience do you have with either?

Perhaps you can elaborate on the chemistry of the resist you are using and how it reacts with the developer.

What sodium silicate developer did you try? NaSi02? NaSi03? NaSi05H2O? There are a ton of variations on sodium silicate and I'd like to know more about their differences.
Read up on silicates. You will find it is complex and in general, there is no way to answer that question.

I'm not looking for the sodium silicate to act as a buffer- I'd like it to be the developer itself- and I'd like to know more about the chemistry.
What's the difference?

If you want to wave your hands and say "it's complicated" or "You just don't understand the chemistry of your resist" - well that doesn't help me.
Why don't you call the manufacturer and ask it for the details? Say I sent you. You still won't get them.

John
 

thingmaker3

Joined May 16, 2005
5,084
A modicum of civility is called for here. We are discussing technical matters, not trading flames. This is your one and only warning.
 

Thread Starter

sirket

Joined Mar 7, 2009
11
Moderators: Can you please delete this thread- It's devoid of technical information and of no value to the forum community. I'll start another post when I have more useful information to share.
 
Last edited:
Status
Not open for further replies.
Top