problem in exposing solder mask

[mov-jump]

hello
 
I am in the way of exposing pads for the final step of creating PCB at home.
I tried too many time :
fix glass sheet on the pcb which is etched and turn light on>>> after 45 min put the pcb into sodium carbonate for 5-7 min with brushing pcb but every I follow this way I  couldn't catch the goal of exposing solder mask to make pad copper visible.

please help me from this mind blowing thing.

Notice that:
I try the step of lightning for 5 times:
1- 10 min (LED lamp position)
2- 30 min (LED position)
3- 30 min (Lamp position)
4- 45 min (LED lamp position)
5- 1 and a half  (sun and lamp position)

[mov-jump]

Nobody can help ?? 

[Psi]

You need to use a PCB which is designed for this purpose. It needs to be Photosensitive.

Regular copper clad pcb isn't photosensitive

[mov-jump]

You need to use a PCB which is designed for this purpose. It needs to be Photosensitive.

Regular copper clad pcb isn't photosensitive

I see . And of course I am using a photosensitive sheet to cover my copper clad pcb

[jpanhalt]

@mov-jump
My first post, so apologies for technical problems.

I have used a photoresist method for making PCB's for many years.   I start with a blank PCB that is coated with the resist.  One can also start with a plain PCB and laminate a photosensitive resist to it.   Your post cannot be answered, because it is not really clear what you are doing.

1) Are you laminating a photoresist onto a blank PCB?
2) Or, is your PCB precoated with the photoresist?

For either answer, what brand of product are you using?   The methods can be quite different depending on the brand.  If you are familiar with the terms "positive -resist" and "negative-resist," which are you using?

Regards, John

[sleemanj]

I see . And of course I am using a photosensitive sheet to cover my copper clad pcb

If you *are* sensitizing using dry-film or other, then sounds to me like you are over exposing.  1 to 3 minutes is a normal exposure time, 10 minutes is likely over exposed.

for dry film, see my tips http://sparks.gogo.co.nz/dry-film-tips.pdf

[mov-jump]

@mov-jump
My first post, so apologies for technical problems.

I have used a photoresist method for making PCB's for many years.   I start with a blank PCB that is coated with the resist.  One can also start with a plain PCB and laminate a photosensitive resist to it.   Your post cannot be answered, because it is not really clear what you are doing.

1) Are you laminating a photoresist onto a blank PCB?
2) Or, is your PCB precoated with the photoresist?

For either answer, what brand of product are you using?   The methods can be quite different depending on the brand.  If you are familiar with the terms "positive -resist" and "negative-resist," which are you using?

Regards, John

Is there difference between laminating photoresist onto a blank PCB & PCB precoated with the photoresist?
If there is so I am using the first one.

And I don't know any thing about positive resist and Negative resist >> could you attach a link for me to know about it?

Regards, Mostafa

[sleemanj]

And I don't know any thing about positive resist and Negative resist >> could you attach a link for me to know about it?

Dry film is negative ("copper is transparent" on artwork), pre-sensitised is usually positive ("copper is opaque" on artwork).

You are almost certainly exposing for far too long.

See the PDF I already posted.

[mov-jump]

And I don't know any thing about positive resist and Negative resist >> could you attach a link for me to know about it?

Dry film is negative ("copper is transparent" on artwork), pre-sensitised is usually positive ("copper is opaque" on artwork).

You are almost certainly exposing for far too long.

See the PDF I already posted.

At the first thanks you for short but complete answer to my question.

I am using fluorescent lamp and found that by these lamps and the dry film which I am using, it takes about 20 min to expose .
1-3 min is good for UV lamps.

Now I am confused that although pads are exposed but in the sodium carbonate step I can't expose pads complete to see copper, places of pads got thin film but not complete expose.

[sleemanj]

You should develop it longer, or expose it shorter, or both.

Note that:

It sounds like you are using Dynamask or similar to create a soldermask on an already etched PCB, rather than an etch resist to do the etching in the first place.

Your PADS should be black and the rest (every where you want there to be soldermask remaining) should be transparent

Pictures of what you are doing may help.

[mov-jump]

You should develop it longer, or expose it shorter, or both.

Note that:

It sounds like you are using Dynamask or similar to create a soldermask on an already etched PCB, rather than an etch resist to do the etching in the first place.

Your PADS should be black and the rest (every where you want there to be soldermask remaining) should be transparent

Pictures of what you are doing may help.

I am now in the step of developing pads:
http://s7.picofile.com/file/8245350242/IMG_%DB%B2%DB%B0%DB%B1%DB%B6%DB%B0%DB%B3%DB%B3%DB%B1_%DB%B1%DB%B5%DB%B2%DB%B7%DB%B2%DB%B0.jpg
And the final step is having something like below picture:
http://s6.picofile.com/file/8245349950/Untitled111111.jpg
And the picture below is my glass sheet (I draw pads onto it by permanent marker):
http://s7.picofile.com/file/8245347884/IMG_20160331_135643.jpg

Although I tried the developing pads step almost 20 times but I could catch goal of having this final result:
http://s6.picofile.com/file/8245349950/Untitled111111.jpg

[ruffy91]

Your marker is too transparent. The pads are exposed through the marker. Try exposing it shorter. Also use nail lacquer if you really want to draw them by hand.

[sleemanj]

And the picture below is my glass sheet (I draw pads onto it by permanent marker)

The marker is probably too transparent to UV as ruffy91 says.

Also be sure that the artwork (the ink in your case) is against the board.

   WRONG:       PCB GLASS|INK LIGHT
   CORRECT:     PCB INK|GLASS LIGHT

[mov-jump]

And the picture below is my glass sheet (I draw pads onto it by permanent marker)

The marker is probably too transparent to UV as ruffy91 says.

Also be sure that the artwork (the ink in your case) is against the board.

   WRONG:       PCB GLASS|INK LIGHT
   CORRECT:     PCB INK|GLASS LIGHT

yes it's too transparent but I used double glass sheet to have darker pads.

[sleemanj]

And the picture below is my glass sheet (I draw pads onto it by permanent marker)

The marker is probably too transparent to UV as ruffy91 says.

Also be sure that the artwork (the ink in your case) is against the board.

   WRONG:       PCB GLASS|INK LIGHT
   CORRECT:     PCB INK|GLASS LIGHT

yes it's too transparent but I used double glass sheet to have darker pads.

Unless glass is a mis-translation, that would never work,  light will just go in between the glass layers.  print  the artwork same as you do for etching.

[Fred27]

I had great results with Dynamask dry film solder mask. I used a Canon MG5250 ink jet printer in T-shirt mode onto transparencies. It left a nice thick opaque layer of ink. Printed straight from Eagle.