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Question about dry film negative photoresist...

2013-09-04 by <twgray2007@...>

I recently purchased some of the some of the dry film negative photoresist sheets from:

http://www.digole.com/index.php?productID=228

and am experiencing a problem. The film exposes and develops exactly as advertised...extremely easy to use...but I am having a problem after develping. The film remaining on the board seems flake off in some spots. Is this a product of over-developing? Or, maybe the boards aren't completely dry before laminating the film to the pcb? I suspected this was the problem but then I read somewhere that some people recommend laminating the film to a wet pcb to avoid bubbles.

Any ideas?

I also have a problem where every third or forth attempt to laminate the film to the board it crinkles in spots for no apparent reason, but that is another subject altogether.

Re: [Homebrew_PCBs] Question about dry film negative photoresist...

2013-09-05 by James

Do you mean that after/during development some of the exposed areas
(traces) are lifting off the board? If so, that is most likely down to...

1. Insufficient heat (and less likely, pressure) when bonding the
film to the board
2. Insufficiently clean board (finger oils, dust, oxidation..)
3. air bubble, or blister from too much heat
4. too strong/long developer
5. too short/uneven exposure

Here is a PDF with my current dry film tips:
http://sparks.gogo.co.nz/dry-film-tips.pdf

On 05/09/13 04:32, twgray2007@... wrote:
>
>
> and am experiencing a problem. The film exposes and develops exactly
> as advertised...extremely easy to use...but I am having a problem
> after develping. The film remaining on the board seems flake off in
> some spots. Is this a product of over-developing?
>

> _,_._,___

RE: Re: [Homebrew_PCBs] Question about dry film negative photoresist...

2013-09-05 by <twgray2007@...>

No, after developing and letting the board dry...usually overnight...the resist just flakes off in some spots.

--- In Homebrew_PCBs@yahoogroups.com, <homebrew_pcbs@yahoogroups.com> wrote:

Do you mean that after/during development some of the exposed areas
(traces) are lifting off the board? If so, that is most likely down to...

1. Insufficient heat (and less likely, pressure) when bonding the
film to the board
2. Insufficiently clean board (finger oils, dust, oxidation..)
3. air bubble, or blister from too much heat
4. too strong/long developer
5. too short/uneven exposure

Here is a PDF with my current dry film tips:
http://sparks.gogo.co.nz/dry-film-tips.pdf

On 05/09/13 04:32, twgray2007@... wrote:
>
>
> and am experiencing a problem. The film exposes and develops exactly
> as advertised...extremely easy to use...but I am having a problem
> after develping. The film remaining on the board seems flake off in
> some spots. Is this a product of over-developing?
>

> _,_._,___

Re: [Homebrew_PCBs] Question about dry film negative photoresist...

2013-09-05 by James

The points I gave still apply, they are the reasons for easy to remove resist.

Although I wonder if you may be doing something a bit weird, no need to "let the board dry overnight", if you're leaving it wet with developer, that would be a problem ("developer" works as a stripper too, given time), rinse with water and dry it off with a paper towel as soon as you have developed it.

To give you an idea...

Clean blank PCB: 3 minutes
Attach film: 5 minutes
Dark Rest: until cooled (5-10 minutes)
Setup for exposure: 3 - 5 minutes
Expose: 2.5 minutes
Dark Rest: 3 - 5 minutes (if you bother, I don't)
Develop: 2 - 5 minutes in 20g/L warm Sodium Carbonate solution
Etch: depends on etchant
Strip: 10 minutes - 30 minutes in hot strong Sodium Carbonate solution

from a dirty blank PCB, to an etched board ready to drill, it takes about an hour including messing around with artwork etc...

On 05/09/13 13:30, twgray2007@... wrote:

No, after developing and letting the board dry...usually overnight...the resist just flakes off in some spots.

RE: Re: [Homebrew_PCBs] Question about dry film negative photoresist...

2013-09-05 by <twgray2007@...>

No, I don't leave the developer on the board after developing. The last stage of developing is rinsing in cool water to wash the unexposed areas of the film off. The dry film I am using clearly suggests letting the board dry after developing, preferably overnight.

One possible problem is that I only put the board through the laminator one time, rather than several passes, so it may not be bonding as well as it should.

Thanks for the info.

At any rate, I am going to give it another go today

--- In Homebrew_PCBs@yahoogroups.com, <homebrew_pcbs@yahoogroups.com> wrote:

The points I gave still apply, they are the reasons for easy to remove resist.Â

Although I wonder if you may be doing something a bit weird, no need to "let the board dry overnight", if you're leaving it wet with developer, that would be a problem ("developer" works as a stripper too, given time), rinse with water and dry it off with a paper towel as soon as you have developed it.

To give you an idea...

Clean blank PCB: 3 minutes
Attach film: 5 minutes
Dark Rest: until cooled (5-10 minutes)
Setup for exposure: 3 - 5 minutes
Expose: 2.5 minutes
Dark Rest: 3 - 5 minutes (if you bother, I don't)
Develop: 2 - 5 minutes in 20g/L warm Sodium Carbonate solution
Etch: depends on etchant
Strip: 10 minutes - 30 minutes in hot strong Sodium Carbonate solution

from a dirty blank PCB, to an etched board ready to drill, it takes about an hour including messing around with artwork etc...

On 05/09/13 13:30, twgray2007@... wrote:

Â

No, after developing and letting the board dry...usually overnight...the resist just flakes off in some spots.Â

Re: Question about dry film negative photoresist...

2013-09-05 by tda7000

I am currently using similar resist I got on eBay.
I have not yet had problems with it flaking off.

I follow a procedure much the same as James detailed.

However... to test some exposure times I laminated a scrap bit to an old piece of board. The board was dirty and after testing I left it lying around... the sunlight baked the resist very well after a few days.. the whole lot flaked off easily after that.

So maybe your board is not clean enough or you have some solvent residue or such or you are over-exposing.

Re: [Homebrew_PCBs] Question about dry film negative photoresist...

2013-09-06 by Misc Clark

James! Thanks for that PDF!

Clark Cone

On Wed, Sep 4, 2013 at 9:16 PM, James <bitsyboffin@...> wrote:

Do you mean that after/during development some of the exposed areas
(traces) are lifting off the board? If so, that is most likely down to...

1. Insufficient heat (and less likely, pressure) when bonding the
film to the board
2. Insufficiently clean board (finger oils, dust, oxidation..)
3. air bubble, or blister from too much heat
4. too strong/long developer
5. too short/uneven exposure

Here is a PDF with my current dry film tips:
http://sparks.gogo.co.nz/dry-film-tips.pdf

On 05/09/13 04:32, twgray2007@... wrote:
>
>
> and am experiencing a problem. The film exposes and develops exactly
> as advertised...extremely easy to use...but I am having a problem
> after develping. The film remaining on the board seems flake off in
> some spots. Is this a product of over-developing?
>

> _,_._,___

RE: Question about dry film negative photoresist...

2013-09-10 by <rcbuckiii@...>

I bought some of the dry film from the same ebay vendor last month. I have not had any problems with it. Make sure the board is clean. I use Bar Keepers Friend and a scrub brush to clean the board. After cleaning and rinsing, I blow dry the board with a hair dryer and only handle it by the edges.

When laminating the board I work under an orange CFL 13 watt bulb that I bought at Home Depot. The brand name is Feit and I have it about 4 feet from my work area.

I have a Scotch TL901 laminator that I use for laminating the board. I put it on the 5 mil setting which is the highest heat. I pass the board through the laminator once, flip it over, and pass it through a second time. By then the board is pretty warm (almost too hot to hold).

I have four FT15T8/BL bulbs mounted in a wooden frame. I expose the board at a distance of 4 inces from the bulbs for 2 minutes. I then let the board sit for 15 minutes before developing. My developing solution is 100% sodium carbonate that I bought at a pool supply house. The name on the container is Pool Season and the product name is pH UP. The ratio is the 20g/L mentioned above. The developer is heated to around 90 degrees F for best results.

I picked up my process from this site: http://www.thinktink.com. They have several tutorials on their site that were very helpful in getting my process down to where it is alway 100% reliable.

Ray

--- In homebrew_pcbs@yahoogroups.com, <clark.cone4@...> wrote:

James! Thanks for that PDF!
Clark Cone

On Wed, Sep 4, 2013 at 9:16 PM, James <bitsyboffin@...> wrote:

Do you mean that after/during development some of the exposed areas
(traces) are lifting off the board? If so, that is most likely down to...

1. Insufficient heat (and less likely, pressure) when bonding the
film to the board
2. Insufficiently clean board (finger oils, dust, oxidation..)
3. air bubble, or blister from too much heat
4. too strong/long developer
5. too short/uneven exposure

Here is a PDF with my current dry film tips:
http://sparks.gogo.co.nz/dry-film-tips.pdf

On 05/09/13 04:32, twgray2007@... wrote:
>
>
> and am experiencing a problem. The film exposes and develops exactly
> as advertised...extremely easy to use...but I am having a problem
> after develping. The film remaining on the board seems flake off in
> some spots. Is this a product of over-developing?
>

> _,_._,___