photoresist

[impsick]

say what chemical is developer? i ask cause i wonder if there is any house hold solutions.

[richie00boy]

sodium hydroxide AKA caustic soda

[impsick]

thanks richie.

[Conrad Hoffman]

The resists I've used in the past were solvent based, and the thinner you could apply them, the better the resolution. It was common to build a "spinner". This was nothing more than a motor with a plate on the shaft, mounted so the shaft was pointing up. The board was stuck to the plate, and the resist applied to the center and spread around a bit. Then the board was spun, throwing the excess resist off the edges- obviously a guard of some sort is needed- could just be a cardboard ring. This gives a very thin uniform coating for short exposure and high resolution. I don't know if it's necessary or practical for what you'll be using.

[sek]

Hi Stefanoo,

i found very interesting the first brand that you mentioned.
Did you order a small quantity from them?

I buy them in local stores (in as low as single quantity), they are the least expensive quality brand around here.
I've never ordered from them, but e.g. http://www.reichelt.de delivers Bungard material.
Just take care it's not too old. Shelf life of the laquer involved is usally limited to between 6 and 12 months (depending on storage temperature)!

So far only good results, my film quality and exposure timing have always been the limiting factors - as long as the photo resist wasn't over-aged.


Hi Impsick,

say what chemical is developer? i ask cause i wonder if there is any house hold solutions.

The usual developer for positive etch resist laquer is natrium hydroxide (NaOH). Drain cleaner consists of NaOH and Aluminium powder (together with some additives). Some DIYers report good results using drain cleaner with the Al removed. Though NaOH is cheap if you buy at the right places (e.g. not from medical suppliers).

Cheers,
Sebastian.

[impsick]

thanks sek, i was wondering if drain cleaner would work

[sek]

A ten percent solution is recommended. Wait until it is cooled down after solving.

Developing should take no shorter than 20 seconds (and no longer than 60) for best results.

With your preferred drain cleaner, you should do individual research with a scrap piece.

Cheers.

[Nordic]

I get good results giving freshly sprayed boards a 10 minute bake, at the lowest setting that will light the oven's pilot light (about 60C). Then cooling boards for an hour before useing... boards can be given a light coat to cover missed spotlets while its still hot, it will dry quickly.

I agree with the thin coats.. and standing the board on one edge in the oven, helps getting it even... Also rather spray too little and touch up on takeing out of the oven, than too much.

Wish I can get boards developed in 60seconds... always seems to take waaaay longer..unless it all comes off in one shot (too strong solution). I've settled ona bit less than a teaspoon of soda flakes, into 1L of water... the first cup being boiled and the soda mixed into to completely disolve... use something that can stand heat and be carefull... it will boil hard for 5 seconds after you drop the soda in.

I put my boards in for 3 seconds, then run it under the tap to make sure solution is not too strong... else add a tiny bit of water.. or (depending) 2 or 3 flakes of soda diluted in a bit of boiling water, to your solution.

Another common name for caustic soda is lye... and you should get it in any hardware shop... its used for cleaning drains....

I throw a few spoons and plastic kitchenwares in the leftover solution when done developing... you will be amaszed at how much goo comes off things you thought were clean before...

[masood]

dear sir,
which type of chemical is spray on pcb for photo resist?
thanks your ever masood

[sek]

Hello Masood,

I have been using CRC Positiv 20 before, although that seems to be a local product. I don't assume that this one is distributed worldwide.

But as a lot of electronics and PCB manufacturing is going on in India, I'm sure you can find something equivalent.

Good luck,
Sebastian.