DIY production of PCBs

[alifred]

Hi,

Now I have a break from school (half term holiday) I am embarking on another one of my probably slightly too ambitious electronics projects!

In the past I have created my own PCBs using the toner transfer method but I have successfully created PCBs for SMD components before but I want to move on to the UV exposure method and apply a soldermask layer to the PCBs. This helps enormously when soldering components in very small packages by hand.

I am really chucking myself in at the deep end with the UV exposure method and I wondered if anyone has any experience with it because when looking around equipment seems very expensive for what it is! For example I was looking at Mega (Mega-UK - Home) and they want £649 (ex. VAT) for an A3 laminator to laminate on the soldermask film! I have contacted them and they will give me a 5% student discount but £649 – 5% + 17.5% = £724.45. This much for a laminator, it must be made of gold!

I would really like some information especially about applying a solder mask and where to get (or how to make) this rather specialist equipment. I suppose it is not vital so I may just not apply a soldermask in the end. Plenty of solder flux will probably have the same effect in resisting solder.

Thanks for any light shed on the subject.

Fred

 

[Hero999]

The UV method is quite easy.

An exposure can be made out of an old scanner (ask Thunderchild who had a spare one but he might've already got rid of it) and UV LEDs or black light fluorescent tubes.

I've never made a solder mask before, does it involve UV exposure? I would've thought you could buy a spray on solder resist.

Have you tried making a silk screen?

I have. I used the toner transfer method and covered the toner with a thin conformal coating to protect it.

 

[DirtyLude]

This is the best DIY soldermask I've seen so far.
https://www.electro-tech-online.com/threads/diy-solderstop-mask.99502/

Personally I've done many 0.5mm lead chips on boards with both mask and no mask and I don't find the mask to be any benefit. Only issue I have without the mask is sometimes the leads can get stuck between the pads a bit so it's not so easy to slide into place.

EDIT: Many people here use standard cheap laminators for ironing etch resist. I don't see why this wouldn't work for your soldermask. Some can be temperature adjusted.

 

[Hero999]

The process is pretty much as I expected except I'm surprised to see film and a laminator.

The cost of the laminator puts me off.

Can you buy a spray solder resist which can be developed in a similar manner?

 

[alifred]

The only thing with making a exposure unit is getting the brightness and exposure times right. I suppose I can just have a play with a bit of trial and error! Correct me if I am wrong but I thought that you cannot use black light tubes for UV exposure because it is the wrong wavelength?

I have never tried applying a silk screen but may do with the toner transfer method. The only downside is that it would be black! Ideally I would want a white one like the professionals!

Applying the soldermask just consists of laminating it on and then exposing the bits you want to stay to UV light. Then develop like you would do with photoresist.

I cannot find anyone who self any other kind of soldermask. A spray-on one would be good but others seem to be peelable! I dont really want that!

Thanks

 

[vne147]

The process is pretty much as I expected except I'm surprised to see film and a laminator.

The cost of the laminator puts me off.

Can you buy a spray solder resist which can be developed in a similar manner?

I have just used green spray paint before. I think I normally use **broken link removed** color. When soldering in components, the paint covering the pads vaporizes when the solder touches it. I have never had a problem with not getting a solder joint because of the paint covering the solder pad.

I am kind of interested in this method that DirtyLude linked to.

A little off topic but I want to talk about it anyway is that I have also in the past tried to make labels on the component side of my boards using the toner transfer paper and the white film. It comes out pretty good but if I spray paint over it, the white lettering turns light green. It's readable, but doesn't look good. I have also tried to put the labels on the board after spray painting but that was a mess becaue the heat from the laminator made the paint tacky again.

I have also tried actually silk screening the labels onto the PCB before using a kit from this site but it wasn't very EZ for me. Never got it to work right. I still haven't yet found an easy way to put white labels on the component side of a green PCB.

 

[alifred]

I have seen other people use green spray paint before but all with varying degrees of sucess/failure! If the paint vapourizes with solder then it must not be very good as being a soldermask!

Thanks very much DirtyLude for that link. I will investigate that further any maybe give that soldermask method a go!

 

[Hero999]

Exactly, I've seen the spray on green conformal coatings before which aren't resistive to solder but never spray on solder resist; does it exist?

 

[alifred]

I looked into the German method of soldermask and I think I will import some of the soldermask from them. It also seems very cheap.

The question is now what do people use as a laminator for their 1.6mm and 0.8mm PCBs? Normally I use 1.6mm boards so which laminators do you use that can accomodate that sort of thickness?

Also what do people use as improvised UV exposure units as UV LEDs are very expensive and I cannot find anyone supplying UV tubes that are not black light.

Thanks for everyones help!

 

[alifred]

Hey

If any of you have made a UV exposure unit, could you please tell me what bulbs you used and where you got them from. This would help me a lot as there are so many that output a range of different wavelengths from 250nm to about 500nm!

Could someone please tell me the difference and which one would be best.

Thanks

 

[DirtyLude]

I don't use the photo method myself, but I know it's been talked about before.

https://www.electro-tech-online.com/threads/uv-sensitive-pcb-material.100438/
https://www.electro-tech-online.com/threads/making-a-uv-box-how-many-w-cm2.96813/
https://www.electro-tech-online.com/threads/yaet-yet-another-etching-thread.88830/
https://www.electro-tech-online.com/threads/photoresist-pcbs.40999/

 

[3v0]

Several things.

I am not convinced that a solder mask is needed. I use a solder paste mask to apply solder paste and then reflow in a fry pan. If you do not have too much solder there are not bridges. The solder is attracted to the metal.

Even with hand soldering you can do without a mask. Again the key is not using too much solder and removing it if you did. I like to use solderwick with hot air for this.

I have had good luck painting the top side of SS PCBs with Crylon Fushion paint intended for plastics. So far I have only tried white. The key is to use Pulsar paper to transfer the black lettering to the painted surface. Even if the laminator heats the paint the pulsar paper will release it when wet. Great stuff.

For boards that I am not going to reflow I use clear acrylic spray. Like another member said you can solder through it. Just use a thin coat. You can add to it after the board works if you want.

 

[alifred]

Thanks 3v0

Can I ask which laminator you use? I presume you use standard 1.6mm board with it?

Thanks

 

[geko]

Thanks 3v0

Can I ask which laminator you use? I presume you use standard 1.6mm board with it?

Thanks

**broken link removed**

http:/picprojects.org.uk/projects/ir/sirc10f/sirc10c1.jpg

I keep the paper from Laser labels after the labels have been printed/used. This has a shiny finish to it that the laser toner releases from easily. I print a mirror image of the overlay onto this, then with a normal household clothes iron I 'iron' it on to the laminate. Only needs a very light rub over and the image transfers on to the PCB laminate.


Giving the board a quick rub with some fine sandpaper to help the toner key to the surface also helps.

Quick, simple and cheap.

 

[alifred]

If I do laminate on the soldermask then could I 'wet laminate' it on?

What would the advantages and disadvantages of this be?

 

[DirtyLude]

Nice silkscreens geko and 3v0. I just really started putting some silkscreens on. Not so much for component placing, but labeling header pins on devel boards.

 

[3v0]

allfred

I use .4 mm and .8 mm stock mostly. I a bit of heavier stuff from the 80's left over but it will not fit through any of my laminators.

I have collected a few laminators. My best ones are made by GBC..

GBC H210
GBC Personal H65

If you keep you eyes open you can get good new laminators on ebay. They sold off a lot of H65's for $25 each.

With an unknown brand it is a crap shoot because you do not know if it will get hot enough.