Sodium Hydroxide or PhotoResist Developer and Drain Cleaner

[johnnyfp]

I need some advice in making some Positive photoresist developer.

From what I can find a commercially bought Photoresist developer contains around 5% Sodium Hydroxide (shown here) which has to be diluted with 4 parts water. (as detailed here).
Now I have some drain cleaner bought from a Hardware store that contains 16% W/W Sodium Hydroxide. So for me to mix a batch up that will compare to the commercially bought one do I need to add 12.8parts water? Based on
16%/5%*4

Or is my maths wrong?

Thanks

[Mike Warren]

I experimented with that about 18 years ago and never got as good results as the proper developer. There seemed to be too little difference in how it attacked the exposed vs unexposed areas. I concluded that for $2 a packet it wasn't worth stuffing around with. I'd mix up a litre and it would last in a sealed bottle for at least 6 months. Just don't mix used developer back in with unused.

[notsob]

Have a read of the 'developing' section of Mike's article

http://www.electricstuff.co.uk/pcbs.html

[poorchava]

I used to make experiments with photosensitive laminate from Bungard (some people fabricate such laminate themselves with photosensitive spray).

I had some drain cleaner which according to the sticker was like 70-80% per weight NaOH. I found it extremly hard to mix correctly working solution. According to various manuals, general guideline is about 7g of pure NaOH per liter of water.

And ofc - 80% NaOH can burn you skin really badly - don;t ask how I know that :/

[Gavinredelman]

Your piping system can be very much neglected in many households. Like an appliance, pipes must be kept clean so they can function at optimum conditions. Intake pipes pose no problem because they carry only clean water. On the other hand, drain pipes and sewers can be as dirty as you can imagine.

[mcinque]

Imho the "proper developer works well" is a myth. Most commercial developing solutions are simpy Sodium Hydroxide to be diluted in water.

I've never tried or needed a silicate based product.

I've always used with success 1 teaspoon (about 10 Grams) of dry Sodium Hydoxide (you can find it at your local houseware) into 1 Liter of tap water at 20°C. You don't have to be too accurate (there is no need to weigh the Sodium Hydroxide, a teaspoon will do the trick), the Bungard photoresist can tolerate the developing solution very well.

The only real secret is to make dissolve very, very well the Sodium Hidroxide in the water, or you will have spots on your pcb.

About 10/15 seconds in this solution, and your exposed photoresist will be developed.

Any changes in water temperature or concentration, will influence the developing times and results.

I repeat: 1 teaspoon in 1 Lt at 20°C. Move your pcb in the water and use your fingers (of course use proper gloves) to remove any air bubbles that will appear on its surface. It's easy and works well. Trust me.

[flolic]

I've never tried or needed a silicate based product.

You really should try silicate based developer.
I have used NaOH for years, but now I don't want to touch it any more.

[mcinque]

I accept your advice. I'll try it in the next months.

[mikeselectricstuff]

I've never tried or needed a silicate based product.

You really should try silicate based developer.
I have used NaOH for years, but now I don't want to touch it any more.

Silicate developer is way better, for 2 reasons :
1) HUGE margin between "Develop" and "strip", so you don't need to worry much about temperature, concentration and differences between laminates, you can use it really strong for quick 5-10 sec developing and still  run minimal risk of stripping for up to a minute or so - this is also helpful if your UV box output isn't very uniform.
2) Solution has infiinite shelf-life - NaOH goes funny^*after a while - less of an issue if you make it up fresh, but if you have a permanent tank setup, with NaOH you need to drain & refill regularly. With silicate you just chuck some more in when dev times get longer.

^* Excuse my lack of chemisty knowledge

[mcinque]

I always make fresh NaOH and I've never used another product simply because I never had any issue using it, call me lucky but I've never stripped a pcb  .
Reading that silicate based products has infinite shelf life it's indeed interesting...

[orin]

I've always used MG Chemicals boards and developer.  I mix up a batch of developer and reuse it until it gets kind of green and icky or developing a board takes too long.  Never had any problems with boards stripping (apart from the very first board I did when I used old instructions and mixed 5:1 instead of 10:1). 

According to the MSDS, the developer is 7-11% sodium hydroxide with deionized water.  Yep, good old drain cleaner.  Hmm, suspect 11% probably wouldn't do a very good job as drain cleaner.

I don't know why an NaOH solution would go bad unless it was open to the air and absorbed CO2 producing sodium carbonate precipitate.

Orin.

[mamalala]

I used to make experiments with photosensitive laminate from Bungard (some people fabricate such laminate themselves with photosensitive spray).

I had some drain cleaner which according to the sticker was like 70-80% per weight NaOH. I found it extremly hard to mix correctly working solution. According to various manuals, general guideline is about 7g of pure NaOH per liter of water.

And ofc - 80% NaOH can burn you skin really badly - don;t ask how I know that :/

Are you sure that you used NaOH to develop the laminate (Tenting laminate/resist)? Tenting is photonegative and uses Na2CO3 as developer (also known as soda, sodium carbonate). Presensitzed PCB's usually are photopositive, and that uses NaOH (sodium hydroxide). Using NaOH on photonegative resist is normally used to strip it.

For NaOH, use 10-20 grams per liter of water for developing photopositve material or Alucorex, 30-50 grams per liter for stripping Tenting and Dynamask. For Na2CO3, use 10-20 grams for developing photonegative Tenting/Dynamask.

Greetings,

Chris

[mrflibble]

You can do it with NaOH, but in my experience it's rather touchy. Very sensitive to concentration and temperature. Concentration is not much of a problem, but the temperature sensitivity makes it annoying. And it's very easy to over/underdevelop.

I'd say try it once with NaOH and once with a silicate based solution, and then decide what you prefer. Or more likely, try it several times with NaOH just to get it right, and then try once with silicate, and then decide.

[Dago]

You guys make developing photoresist sound hard!

I've always just mixed KOH drain cleaner with water to form (IIRC) about 1% solution and I reuse it for tens of times without any problems. With the correct solution the board develops in around ten seconds or so but even if you leave it in the solution for minutes it still doesn't seem to "strip" it at all. I also store the (used) solution for years and it seems to work fine every time.

Never found it to be touchy at all, just keep the solution at room temp and it works fine every time.

[Simon]

The drain cleaner works nice and slow if you don't make it too hot but past a certain temperature it goes fast. I gave up, but then I'm not much of a chemist and hate having to judge it just right.

[Dago]

The drain cleaner works nice and slow if you don't make it too hot but past a certain temperature it goes fast. I gave up, but then I'm not much of a chemist and hate having to judge it just right.

No need to heat it up. Just adjust the solution so that it works like it should in room temp. I also had problems when I tried to heat it up... no way to get it working consistently like that without some kind of real temp control.

[Simon]

I found that heating it increased it's speed of reaction drastically to the point it was so fast I couldn't get it out in time. warming slightly is a good idea else it can take stupidly long, can't remember what temp i used when happy but a cold winters day in the shed was definitely "unreactive"

[Dago]

Then the solution wasn't strong enough. With a suitable solution developing takes 10-30s in room temp.

[poorchava]

With the drain cleaner you need to be very careful about its chemical composition. They quite often add stuff like aluminum powder to make the reaction inside the drain faster.

It's best to use chemical-grade NaOH. It can be bought without restrictions in most countries, because it's widely used for example in food preparation and as a cleaning agent. If I was able to buy a kilo of it in Poland for like 1.5€, the you can probably buy it anywhere.