Can I use CFL tube light as a UV source to make PCB?

[Willen]

I don't have Ultraviolet source to expose PCB. I want to make PCB using UV expose method. I think normal home use CFLwill produce UV? How long time should i have to expose in this UV source? Guide me!!

 

[picbits]

Yes it will work - boards I've left under flourescent lights have eventually exposed but that was more by accident than design.

You want to take a strip of PCB, mask it with a piece of thick card and leave a little bit (1cm) of board exposed. Expose by say 5 minutes then move move it by another 1cm. Keep going until you've exposed the last part of the board.

This will let you calibrate your CFL for exposure time. You may need 5 minutes, you may need a couple of hours.

Some people use a 500w halogen bulb with success as well.

 

[ericgibbs]

I don't have Ultraviolet source to expose PCB. I want to make PCB using UV expose method. I think normal home use CFLwill produce UV? How long time should i have to expose in this UV source? Guide me!!

hi,
Its possible to use exposure to sunlight to make a pcb, support the pcb face at right angles to the sun.

Depending upon the intensity of the sunlight the exposure time will vary. In the UK on a sunny day [ rare has hens teeth] it takes about 20 to 30 minutes.

Try a few sample pieces of pcb in order to get the time right.

 

[jpanhalt]

When discussing photoresists, it is important to say what type you are using. There are positive resists and negative resists, and among each of those categories, there are different types.

Assuming you are using a positive photoresist based on Novolak resin with a napthoquinone diazide photosentizer, the answer is yes. Here is why. Novolak resin does not absorb sufficiently in the near UV to work by itself. A photosensitizer is added to absorb the light energy. It then transfers that energy to the novolak resin where a change occurs that makes it more soluble in aqueous base. Here are the absorption spectrums of novolak resin and the sensitizer.

View attachment 66794

I use UV fluorescent lamps with a phosphor (BL = "Blacklight", e.g., F15T8-BL by GE) that produces quite a bit of energy between 380 and 395 nm or so. That is effective for exposure because of the the broad absorption of the sensitizer in the same region. Note, however, that the absorption extends into the visible as far as 436 nm (G band of mercury).

Here is a link to a Scientific American article that gives the emission of CFL lamps: https://blogs.scientificamerican.com/solar-at-home/2011/03/21/a-better-kind-of-lightbulb/

Here is the spectrum reported:

View attachment 66795

A CFL does put out a small amount of its energy at about that wavelength. As noted, exposure time may be quite a but longer.

For judging exposure, I find that using a pattern is more effective than just seeing whether the plate is exposed or not. The pattern I use is just two arrows heads pointed toward each other, like this: ><

Make each leg about 1 cm long and have the tips just touch. That design allow you to grade whether the exposure is over, under, or just right.

John

 

[Willen]

I am little new about UV PCB making.
Can I expose in general PCB or should I have to use photo sensitive PCB to expose in UV?

 

[jpanhalt]

The PCB used must be photosensitive. A bare PCB will not work.

You can buy pre-sensitized blank PCB's from most electronic suppliers. The most common variety of pre-sensitized board has a "positive" resist, which means that the areas shaded from light are NOT removed during photodevelopment ("development"). Thus, the developed board will show a pattern of the circuit you want. The positive-resist developer is usually an aqueous base, such as sodium carbonate or sodium hydroxide in water.

One can also buy a photosensitive film that you laminate to a bare board prior to exposure to light and development. Such films are usually "negative" resists. That is, the shaded areas ARE removed in development. DuPont makes a series of such films and they are available in small amounts on eBay. Your image must be a negative of the final PCB. The developers are proprietary and usually contain a particular organic solvent (check the MSDS's for more information). You must also consider the absorption spectrum of the resist and any photosensitizer included in it.

Since you are a beginner with little experience in UV or photochemistry, I strongly recommend that you buy a pre-sensitized, positive-resist board and use the commercial developer that is available with it.

John

 

[Willen]

The PCB used must be photosensitive. A bare PCB will not work.

You can buy pre-sensitized blank PCB's from most electronic suppliers. The most common variety of pre-sensitized board has a "positive" resist, which means that the areas shaded from light are NOT removed during photodevelopment ("development"). Thus, the developed board will show a pattern of the circuit you want. The positive-resist developer is usually an aqueous base, such as sodium carbonate or sodium hydroxide in water.

One can also buy a photosensitive film that you laminate to a bare board prior to exposure to light and development. Such films are usually "negative" resists. That is, the shaded areas ARE removed in development. DuPont makes a series of such films and they are available in small amounts on eBay. Your image must be a negative of the final PCB. The developers are proprietary and usually contain a particular organic solvent (check the MSDS's for more information). You must also consider the absorption spectrum of the resist and any photosensitizer included in it.

Since you are a beginner with little experience in UV or photochemistry, I strongly recommend that you buy a pre-sensitized, positive-resist board and use the commercial developer that is available with it.

John

But I heared that I can expose in general PCB by applying somthing..... um....positive 20spray (?) before expose. They say that we can convert general PCB into photosensitive by applying some chemical using spray. Can I use general paint in spray or is it special chemical?
My big confusion is about this spray and its chemical. Please guide as basic way.

 

[jpanhalt]

Please read my replies again and take that advice.

1) NO, regular paint won't work. Some experimenters do use regular paint and ablate it with a CNC laser, which you are not doing. I don't think you have or are likely to get that equipment very soon.

2) Yes, you can buy the photoresist as a liquid and try to coat you own plates. You will get lousy results and not save any money.

3) As mentioned in post #6, you can buy photosensitive film and laminate it to the board. If you go that route, you will probably need to deal with a negative resist and special developers.

Are you trying to make a PCB for an electronic project, or are you trying to study all the different ways to make a PCB. If it is the latter, there are other ways we have not yet discussed.

John

 

[Willen]

Please read my replies again and take that advice.

1) NO, regular paint won't work. Some experimenters do use regular paint and ablate it with a CNC laser, which you are not doing. I don't think you have or are likely to get that equipment very soon.

2) Yes, you can buy the photoresist as a liquid and try to coat you own plates. You will get lousy results and not save any money.

3) As mentioned in post #6, you can buy photosensitive film and laminate it to the board. If you go that route, you will probably need to deal with a negative resist and special developers.

Are you trying to make a PCB for an electronic project, or are you trying to study all the different ways to make a PCB. If it is the latter, there are other ways we have not yet discussed.

John

I used toner transfer method before to make PCB. Now I want to make PCB from UV expose for better qualiy. Photosensitive PCB is nore expensive in market, so I want to expose in general PCB.
OK I will use photoresist liquid as you said.


-What is the name of photoresist liquid in market?
- Almost how much time it takes to expose in general CFL (15 or 20 watt) bulb?
- What happens if I expose more than necessary?

 

[Willen]

Please read my replies again and take that advice.

1) NO, regular paint won't work. Some experimenters do use regular paint and ablate it with a CNC laser, which you are not doing. I don't think you have or are likely to get that equipment very soon.

2) Yes, you can buy the photoresist as a liquid and try to coat you own plates. You will get lousy results and not save any money.

3) As mentioned in post #6, you can buy photosensitive film and laminate it to the board. If you go that route, you will probably need to deal with a negative resist and special developers.

Are you trying to make a PCB for an electronic project, or are you trying to study all the different ways to make a PCB. If it is the latter, there are other ways we have not yet discussed.

John

I used toner transfer method before to make PCB. Now I want to make PCB from UV expose for better quality. Photosensitive PCB is more expensive in market, so I want to expose in general PCB.
OK I will use photoresist liquid as you said.


-What is the name of photoresist liquid in market?
- Almost how much time it takes to expose in general CFL (15 or 20 watt) bulb?
- What happens if I expose more than necessary?

 

[jpanhalt]

-What is the name of photoresist liquid in market?

MG Chemicals may still sell the liquid. I am not sure. I am not aware of a specific brand name. I would not consider even trying to do it. It is difficult to get a uniform coating. Spinning is probably the easiest -- check out YouTube for some examples. Again, I would not recommend making your own positive photosensitized boards. We do not know your location, so shipping of the liquid may present an additional problem.

- Almost how much time it takes to expose in general CFL (15 or 20 watt) bulb?

That will depend on the resist that you get. I use Injectorall. My exposure with three, 15W BL bulbs runs about 12 minutes. From what I have read from people who use the MG boards, their exposure time would be less. With the same wattage of CFL, it will be longer than that. See the curves I posted.

- What happens if I expose more than necessary?

You will get poor resolution. In fact, if it is over-exposed enough, the whole image may wash off. That is why I recommended using some sort of character and trial run to judge the exposure time needed.

John

 

[Boncuk]

I strongly recommend to use readily made photoresist material for PCBs. I further recommend to stay with the brand you have purchased, tested and found good for you.

Using liquid photoresist you end up with a pretty messy work place and NO result at all. Liquid photo resists requires 24 hours of baking at 70°C and a slow cooling period in absolute darkness.

The same applies to Positive20 a sprayable photo resist made by Kontakt Chemie, Denmark.

I prefer to go the somewhat more expensive way (shipping) and purchase photo resist basic material at BUNGARD (https://www.bungard.de)

Bungard PCBs are the Mercedes class boards amongst boards.

Bungard photo resist has not been changed for years, which means you might omit any dry runs when using different brands of PCB material. The film coverage is even all over the board area leaving no "clouds" after development. "Clouds" can be seen after rinsing the developed PCB with water and dunking it into the etchant for a short moment and checking for shiny areas which are commonly found within large copper areas.

Those clouds take very much time to get etched burying the risk of under etching fine traces and making the board unusable.

My last advise: Don't think to save money when buying cheaply. By the time you've got a successful result you will have

- spent more money for new raw material
- gained more gray hair
- your hair pulled out several times
- and you'll have had several heart attacks (Remember: The fourth one is deadly! )
- risked the partnership with your wife
- become a stranger for your kids.

Regards

Boncuk

 

[picbits]

Using liquid photoresist you end up with a pretty messy work place and NO result at all. Liquid photo resists requires 24 hours of baking at 70°C and a slow cooling period in absolute darkness.

The same applies to Positive20 a sprayable photo resist made by Kontakt Chemie, Denmark.

Positiv 20 is actually 15 minutes at 70 degrees C

Datasheet here : https://www.electro-tech-online.com/custompdfs/2012/09/87-0705t.pdf

 

[Boncuk]

Positiv 20 is actually 15 minutes at 70 degrees C

Datasheet here : https://www.electro-tech-online.com/custompdfs/2012/09/87-0705t.pdf

just to add: ... with the PCB material absolutely horizontal.

 

[picbits]

I must get round to having a play with the can of Positiv 20 I bought a while ago - it's meant to be good for custom made panels etc.

 

[stevetaylor]

Hi,
Yes, you can use CFL tube light to expose PCB. Indeed people have even used a halogen bulb to do the same and it worked perfectly fine.

All is dependent on intensity of the tube light you've been using and the exposure time. Note one thing PCB must be photosensitive unless it will not work.