Negative Photoresist PAINT ?

[ChildOfVision]

Hi to everyone!

I decided to try out negative dry-film photoresist foils, and I accidentally found this thing: Negative Photoresist PAINT! Here is the picture:
View attachment 68243
And here is ebay link:
**broken link removed**
I didn't know such a paints exist, and don't know anything about it!
So I need your observations and advice!

1) Is that paint better (or at least the same) as dry negative film?
2) Does it have shelf life (undiluted)?
3) On ebay listing there is description how to use it, BUT: they said I have to dilute that paint in 1:3 ratio BUT with what thinner/diluter? They also said: if you dont have proper thinner, just use "banana-oil"!? What banana-oil - never heard about it! So if somebody knows what can one use as a thinner (easy-to-find chemical!) - please, let me know!
4) What developer can I use for that stuff? Of course, I contacted seller, but no response by now! They are selling also developer for this, it is not expensive, but I have package of standard negative developer (sodium-carbonate - Na2CO3), can I use it? I even scan pictures of developer bag with OCR software and I (with alot of efforts) translated Chinese hieroglyphs: "Analytical grade, Developer powder" - nothing else!
I noticed also that "thinning ratio" is 2:100 (say 2 g to 100ml water), and Na2CO3 is usually diluted at ratio 1:100!

Of course, I can buy cheap Chinese (or expensive DuPont) foils, but that paint seems very "handy" to me, even for non-PCB related things!

So what do you guys (and girls) think?
Any opinion appreciated!

 

[jpanhalt]

1) First, I would not recommend using it for the same reason not to use positive resist paint. You cannot get a good, uniform layer reproducibly.

2) Second, ask for the MSDS. No MSDS, then don't buy it.

3) Shelf-life is hard to say without knowing what the resist is. It may simply be a chromate-modified gel as is used in silk screening and so forth. Those are pretty stable.

4) As for thinner reducer, you need to know what the material is. They do give a hint, "banana oil." If they mean some sort of oil for cooking, I have no idea what they mean. If they are referring to the smell, then it is likely a sweet smelling ester, such as ethyl butyrate. Wikipedia lists isoamyl butyrate as "banana oil." Ethyl acetate might work as might some acrylic enamel thinners or lacquer thinners that have a lot of ethyl acetate or ethyl butyrate in them. The simple esters I mention all have similar solvent properties, but vary in volatility. Ethyl acetate is the most volatile. The more carbons in the ester, the less volatile it will be. Having less volatility will help you get a more even layer, but it will take longer to dry.

5) Developer -- demand that the seller tell you. Dupont negative-resist developer is not simply sodium carbonate. It has an essential organic component. Check out its MSDS. Since this seller's developer is made in only water from a dry solid, the likelihood that it is simply sodium carbonate is higher.

6) Finally, Although negative films are more sensitive to visible light than positive resists are, you need to know the excitation needed for this resist. Positive resists all contain a photosensitizer that moves their excitation maximum to longer wavelengths as well as maybe facilitating a different type of chemical reaction. Again, in the absence of information, you are left to experiment. The lamp shown in the ebay listing looks like a near UV lamp (F15T8-BL ???) judging from the amount of visible light present.

John

 

[ChildOfVision]

Thank you very much, John, for quick and expert answers!

I don't care too much for non-uniform "layering", but for absolute absence of very essential info!
I must tell you that I ask MSDS for DuPont-Riston films from European sellers! One of them tell me that developer for those films is (pure) sodium-carbonate. Also, in DuPonts datasheet, if I understood correctly, recommended developer can be sodium-carbonate, OR sodium-carbonate monohydrate (Na2CO3xH2O) OR one more chemicals which I can't recall right now. As remover, standard chemicals are NaOH or KOH.

If I would have enough money, I would buy that complet, NOT FOR PCBs, but experimenting - I was thinking - maybe I could made mixture of that paint with silicone rubber and get cheap photopolymer plates (for diy-stamps for example)!
But I don't have money for experimenting, so I will most probably buy no-name Chinese foils and try my luck with these.

Btw, ALL photoresist sellers tell me that those foils have NOT shelf life if stored properly (in dry and cold place without light, of course), but I don't think so, maybe 6 months...

 

[jpanhalt]

You are correct about Riston using sodium carbonate. I had confused it in my mind with MG Chemicals' negative resist (https://www.electro-tech-online.com/custompdfs/2012/10/720.pdf) that includes cyclohexanone and other organics. MG Chemicals makes several developers. That is just one of them.

BTW, here is a nice Dupont application note: https://www.electro-tech-online.com/custompdfs/2012/10/Dry_Film_Photoresist_Tech_forPCB.pdf


John

 

[ChildOfVision]

Well, if sodium-carbonate is good enough for Riston, it must be good for Chinese foils as well!
If I can ask, John, can I rely to that Chinese foils?

(Thanks for PDF, it will be useful to me!)

 

[jpanhalt]

There is no way to know if you can rely on them.

John

 

[darkenedforest]

One eBay description I read said to use banana oil or lacquer thinner to thin it.

 

[jpanhalt]

Welcome to ETO.

This is a bit of an old thread.

However, banana oil may be a lay translation for butyl acetate. Just checked Wikipedia. It calls banana oil, isoamyl acetate. That is butyl with one more carbon. Both are an excellent solvents, but lacquer thinner/reducer is probably more readily available to you. I believe lacquer thinner will evaporate more rapidly, which is perhaps one advantage to using butyl acetate/isoamyl acetate, if you are preparing your own sensitized plates.

For rapid and complete removal of the resist after etching, I recommend using just a more concentrated base. For example, if you use 0.5 M NaOH for your developer, just add an extra few grams of NaOH to 100 mL, and it will remove all of the resist.

John

Edit: added comment about isoamyl acetate