Homebrew PCBs

Hey guys,

I have had a good run with toner transfer but the more I get into these small packages, the more failures I am getting.  The surface mount chips (100 pin qfp) are just too demanding.

I have tried using that dry-film etch resist that you buy on a roll, apply it to the board with a laminator and have had mixed results.  

Today it took me all of 7 hours to make a small board that is only 60 MM X 60 MM.

I am wondering what it a more reliable method to try next.

Chris

On Tue, 04 Aug 2009 22:54:17 -0000
"lcdpublishing" <lcdpublishing@...> wrote:

> Today it took me all of 7 hours to make a small board that is only 60
> MM X 60 MM.

You do not specify which part of the process is failing.

Though I don't make production runs (but then TT isn't suitable for that),
results here are certainly acceptable, with moderate care and
experimenting.

John

"lcdpublishing" <lcdpublishing@...> writes:
> I have tried using that dry-film etch resist that you buy on a roll,
> apply it to the board with a laminator and have had mixed results.

If you mean photofilm, it took me a while to get reliable results from
it.  Some thoughts...

It wants around 220-240 F temperature, far cooler than most
laminators.  I added the temp control to mine just for this purpose.

I cut the film a few inches longer than needed so I can hold it up and
pulled away from the board during lamination, letting the rollers be
the first to press them together.  Far fewer air bubbles this way.
Adam's wet lamination gets the same results, for mostly the same
reasons, using a wet squeegie.

I have to bloat all my prints by 2 mils per edge (think "bigger
copper") to get the resulting sizes I want.

Don't forget the 15 minute wait between exposure and peeling the
backing film off!

I ended up writing my own software to do the prints for this.  Using
either Silkjet or Jetstar films, I can put down a 100% ink coating at
2880 DPI, which is good for 8 or so steps on a 21 step transmission
wedge.

Very important to get the exposure right!  I use a step transmission
wedge (step gauge) to make sure I'm giving it the right amount of
exposure time.  To little and you risk breaks; too much and you risk
shorts.

I did a 6/6 board recently that had a grand total of one gap, due to
one air bubble I didn't catch (the gap is just left of dead center):
http://www.delorie.com/electronics/sdram/sdram-toppcb.jpg

----- Original Message ----- 

From: "lcdpublishing" <lcdpublishing@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Tuesday, August 04, 2009 11:54 PM
Subject: [Homebrew_PCBs] Need better reliability than I am getting with 
toner transfer - what's next?


> Hey guys,
>
> I have had a good run with toner transfer but the more I get into these 
> small packages, the more failures I am getting.  The surface mount chips 
> (100 pin qfp) are just too demanding.
>
> I have tried using that dry-film etch resist that you buy on a roll, apply 
> it to the board with a laminator and have had mixed results.
>
> Today it took me all of 7 hours to make a small board that is only 60 MM X 
> 60 MM.
>
> I am wondering what it a more reliable method to try next.

I use photo-etch with pre-coated boards and don't have any problems with 0.5 
mm spacing QFP parts.

Leon

The link below just gives a warning "please do not hotlink to this site"


--- On Wed, 8/5/09, DJ Delorie <dj@...> wrote:

From: DJ Delorie <dj@...>
Subject: Re: [Homebrew_PCBs] Need better reliability than I am getting with toner transfer - what's next?
To: Homebrew_PCBs@yahoogroups.com
Date: Wednesday, August 5, 2009, 12:53 AM






 




    
                  

"lcdpublishing" <lcdpublishing@ yahoo.com> writes:

> I have tried using that dry-film etch resist that you buy on a roll,

> apply it to the board with a laminator and have had mixed results.



If you mean photofilm, it took me a while to get reliable results from

it.  Some thoughts...



It wants around 220-240 F temperature, far cooler than most

laminators.  I added the temp control to mine just for this purpose.



I cut the film a few inches longer than needed so I can hold it up and

pulled away from the board during lamination, letting the rollers be

the first to press them together.  Far fewer air bubbles this way.

Adam's wet lamination gets the same results, for mostly the same

reasons, using a wet squeegie.



I have to bloat all my prints by 2 mils per edge (think "bigger

copper") to get the resulting sizes I want.



Don't forget the 15 minute wait between exposure and peeling the

backing film off!



I ended up writing my own software to do the prints for this.  Using

either Silkjet or Jetstar films, I can put down a 100% ink coating at

2880 DPI, which is good for 8 or so steps on a 21 step transmission

wedge.



Very important to get the exposure right!  I use a step transmission

wedge (step gauge) to make sure I'm giving it the right amount of

exposure time.  To little and you risk breaks; too much and you risk

shorts.



I did a 6/6 board recently that had a grand total of one gap, due to

one air bubble I didn't catch (the gap is just left of dead center):

http://www.delorie. com/electronics/ sdram/sdram- toppcb.jpg


 

      

    
    
	
	 
	
	








	


	
	


      

[Non-text portions of this message have been removed]

http://www.delorie.com/electronics/sdram/sdram-toppcb.jpg
      is the correct link and brings up the image correctly.


On Wed, Aug 5, 2009 at 7:14 AM, Malcolm Parker-Lisberg <
mparkerlisberg@...> wrote:

> The link below just gives a warning "please do not hotlink to this site"
>
>
> --- On Wed, 8/5/09, DJ Delorie <dj@...> wrote:
>
> From: DJ Delorie <dj@...>
> Subject: Re: [Homebrew_PCBs] Need better reliability than I am getting with
> toner transfer - what's next?
> To: Homebrew_PCBs@yahoogroups.com
> Date: Wednesday, August 5, 2009, 12:53 AM
>
>
>
> "lcdpublishing" <lcdpublishing@ yahoo.com> writes:
>
> > I have tried using that dry-film etch resist that you buy on a roll,
>
> > apply it to the board with a laminator and have had mixed results.
>
>
>
> If you mean photofilm, it took me a while to get reliable results from
>
> it.  Some thoughts...
>
>
>
> It wants around 220-240 F temperature, far cooler than most
>
> laminators.  I added the temp control to mine just for this purpose.
>
>
>
> I cut the film a few inches longer than needed so I can hold it up and
>
> pulled away from the board during lamination, letting the rollers be
>
> the first to press them together.  Far fewer air bubbles this way.
>
> Adam's wet lamination gets the same results, for mostly the same
>
> reasons, using a wet squeegie.
>
>
>
> I have to bloat all my prints by 2 mils per edge (think "bigger
>
> copper") to get the resulting sizes I want.
>
>
>
> Don't forget the 15 minute wait between exposure and peeling the
>
> backing film off!
>
>
>
> I ended up writing my own software to do the prints for this.  Using
>
> either Silkjet or Jetstar films, I can put down a 100% ink coating at
>
> 2880 DPI, which is good for 8 or so steps on a 21 step transmission
>
> wedge.
>
>
>
> Very important to get the exposure right!  I use a step transmission
>
> wedge (step gauge) to make sure I'm giving it the right amount of
>
> exposure time.  To little and you risk breaks; too much and you risk
>
> shorts.
>
>
>
> I did a 6/6 board recently that had a grand total of one gap, due to
>
> one air bubble I didn't catch (the gap is just left of dead center):
>
> http://www.delorie. com/electronics/ sdram/sdram- toppcb.jpg
>
>


[Non-text portions of this message have been removed]

--- In Homebrew_PCBs@yahoogroups.com, DJ Delorie <dj@...> wrote:
> 
> I did a 6/6 board recently that had a grand total of one gap, due to
> one air bubble I didn't catch (the gap is just left of dead center):
> http://www.delorie.com/electronics/sdram/sdram-toppcb.jpg
>

Out of curiosity, why do you have the traces that are right of center doubling back on themselves. Are you trying to equalize path lengths?

I get the same response, using Firefox. Here is a screen shot of the error message. http://rotordesign.com/delorie.jpg

But I get a very large pcb pic using IE 7.0.

That is one heck of a nice board!

Mike



--- In Homebrew_PCBs@yahoogroups.com, Malcolm Parker-Lisberg <mparkerlisberg@...> wrote:

>
> The link below just gives a warning "please do not hotlink to this site"
> 
> 
> --- On Wed, 8/5/09, DJ Delorie <dj@...> wrote:
> 
> From: DJ Delorie <dj@...>
> Subject: Re: [Homebrew_PCBs] Need better reliability than I am getting with toner transfer - what's next?
> To: Homebrew_PCBs@yahoogroups.com
> Date: Wednesday, August 5, 2009, 12:53 AM
> 
> 
> 
> 
> 
> 
>  
> 
> 
> 
> 
>     
>                   
> 
> "lcdpublishing" <lcdpublishing@ yahoo.com> writes:
> 
> > I have tried using that dry-film etch resist that you buy on a roll,
> 
> > apply it to the board with a laminator and have had mixed results.
> 
> 
> 
> If you mean photofilm, it took me a while to get reliable results from
> 
> it.  Some thoughts...
> 
> 
> 
> It wants around 220-240 F temperature, far cooler than most
> 
> laminators.  I added the temp control to mine just for this purpose.
> 
> 
> 
> I cut the film a few inches longer than needed so I can hold it up and
> 
> pulled away from the board during lamination, letting the rollers be
> 
> the first to press them together.  Far fewer air bubbles this way.
> 
> Adam's wet lamination gets the same results, for mostly the same
> 
> reasons, using a wet squeegie.
> 
> 
> 
> I have to bloat all my prints by 2 mils per edge (think "bigger
> 
> copper") to get the resulting sizes I want.
> 
> 
> 
> Don't forget the 15 minute wait between exposure and peeling the
> 
> backing film off!
> 
> 
> 
> I ended up writing my own software to do the prints for this.  Using
> 
> either Silkjet or Jetstar films, I can put down a 100% ink coating at
> 
> 2880 DPI, which is good for 8 or so steps on a 21 step transmission
> 
> wedge.
> 
> 
> 
> Very important to get the exposure right!  I use a step transmission
> 
> wedge (step gauge) to make sure I'm giving it the right amount of
> 
> exposure time.  To little and you risk breaks; too much and you risk
> 
> shorts.
> 
> 
> 
> I did a 6/6 board recently that had a grand total of one gap, due to
> 
> one air bubble I didn't catch (the gap is just left of dead center):
> 
> http://www.delorie. com/electronics/ sdram/sdram- toppcb.jpg
> 
> 
>  
> 
>       
> 
>     
>     
> 	
> 	 
> 	
> 	
> 
> 
> 
> 
> 
> 
> 
> 
> 	
> 
> 
> 	
> 	
> 
> 
>       
> 
> [Non-text portions of this message have been removed]
>

I went back to Firefox. Deleted the letters jpg at the end of the "http://www.delorie.com/electronics/sdram/sdram-toppcb.jpg" URL, then typed them back in and hit enter and got the pcb pic to show up. 

Mike



--- In Homebrew_PCBs@yahoogroups.com, Malcolm Parker-Lisberg <mparkerlisberg@...> wrote:

>
> The link below just gives a warning "please do not hotlink to this site"
> 
> 
> --- On Wed, 8/5/09, DJ Delorie <dj@...> wrote:
> 
> From: DJ Delorie <dj@...>
> Subject: Re: [Homebrew_PCBs] Need better reliability than I am getting with toner transfer - what's next?
> To: Homebrew_PCBs@yahoogroups.com
> Date: Wednesday, August 5, 2009, 12:53 AM
> 
> 
> 
> 
> 
> 
>  
> 
> 
> 
> 
>     
>                   
> 
> "lcdpublishing" <lcdpublishing@ yahoo.com> writes:
> 
> > I have tried using that dry-film etch resist that you buy on a roll,
> 
> > apply it to the board with a laminator and have had mixed results.
> 
> 
> 
> If you mean photofilm, it took me a while to get reliable results from
> 
> it.  Some thoughts...
> 
> 
> 
> It wants around 220-240 F temperature, far cooler than most
> 
> laminators.  I added the temp control to mine just for this purpose.
> 
> 
> 
> I cut the film a few inches longer than needed so I can hold it up and
> 
> pulled away from the board during lamination, letting the rollers be
> 
> the first to press them together.  Far fewer air bubbles this way.
> 
> Adam's wet lamination gets the same results, for mostly the same
> 
> reasons, using a wet squeegie.
> 
> 
> 
> I have to bloat all my prints by 2 mils per edge (think "bigger
> 
> copper") to get the resulting sizes I want.
> 
> 
> 
> Don't forget the 15 minute wait between exposure and peeling the
> 
> backing film off!
> 
> 
> 
> I ended up writing my own software to do the prints for this.  Using
> 
> either Silkjet or Jetstar films, I can put down a 100% ink coating at
> 
> 2880 DPI, which is good for 8 or so steps on a 21 step transmission
> 
> wedge.
> 
> 
> 
> Very important to get the exposure right!  I use a step transmission
> 
> wedge (step gauge) to make sure I'm giving it the right amount of
> 
> exposure time.  To little and you risk breaks; too much and you risk
> 
> shorts.
> 
> 
> 
> I did a 6/6 board recently that had a grand total of one gap, due to
> 
> one air bubble I didn't catch (the gap is just left of dead center):
> 
> http://www.delorie. com/electronics/ sdram/sdram- toppcb.jpg
> 
> 
>  
> 
>       
> 
>     
>     
> 	
> 	 
> 	
> 	
> 
> 
> 
> 
> 
> 
> 
> 
> 	
> 
> 
> 	
> 	
> 
> 
>       
> 
> [Non-text portions of this message have been removed]
>

Malcolm Parker-Lisberg <mparkerlisberg@...> writes:

> The link below just gives a warning "please do not hotlink to this site"

It's web mail.  Replace ".jpg" with ".html" for any image I post and
it will work.  My server thinks your webmail is trying to embed my
photos in your web pages.

http://www.delorie.com/electronics/sdram/sdram-toppcb.html

"javaguy11111" <javaguy11111@...> writes:
> Out of curiosity, why do you have the traces that are right of
> center doubling back on themselves. Are you trying to equalize path
> lengths?

Yes.  It's an SDRAM chip on the right so I took the time to
length-match all the traces.  They're within 0.6 mil of each other :-)

TO clarify,  using the dry film type stuff, I would get blisters - sometimes.  Nothing consistant about it from what I could determine.  I could easily manipulate the dry film onto the board without bubbles (small boards) but after running through the laminator, blisters would appear and those never turned out good.

Other times I would have a simple break in a trace as if there was a cut line in the resist material (toner or dry film).  

Toner works great sometimes and others it simply will not stick to the PCB.  I have been usint the same: printer, toner, PCB material, paper, iron settings, cleaning process, etc. for over a year now.  Sometimes it works great. somedays like the past few, nothing seems to work.

I ran over to Fry's electronics this morning and picked up some positive resist coated material.  My first board failed in that I didn't expose long enough but otherwise the board looked great after etching (except where the resist didn't come off).  I am currently exposing my second board and will know within a half hour or so if this one works out.  So far it is actually a faster process than any of the others.  I know that it comes at a cost (more expensive stock) but if it removes the problems it will save sanity. In some cases, it will actually be cheaper too if I am not trying and failing time after time wasting PCB stock, transparancy films, etchant, etc.

Hopefully this will work out and I can move on.

BTW, on my best day, I have never had a board look as good as yours.

Chris

It's not the webmail, I copy and pasted the link into a blank browser
page and got the same error. Deleting the jpg on this page and
re-typing it worked and the pasted link then also worked when pasted
into another new  blank page.


--- On Wed, 8/5/09, DJ Delorie <dj@...> wrote:

From: DJ Delorie <dj@...>
Subject: Re: [Homebrew_PCBs] Need better reliability than I am getting with toner transfer - what's next?
To: Homebrew_PCBs@yahoogroups.com
Date: Wednesday, August 5, 2009, 5:15 PM






 




    
                  Malcolm Parker-Lisberg <mparkerlisberg@ yahoo.com> writes:



> The link below just gives a warning "please do not hotlink to this site"



It's web mail.  Replace ".jpg" with ".html" for any image I post and

it will work.  My server thinks your webmail is trying to embed my

photos in your web pages.



http://www.delorie. com/electronics/ sdram/sdram- toppcb.html


 

      

    
    
	
	 
	
	








	


	
	


      

[Non-text portions of this message have been removed]

"lcdpublishing" <lcdpublishing@...> writes:
> TO clarify, using the dry film type stuff, I would get blisters -

If you lay the film flat on the pcb and run it through the laminator,
you're going to get blisters.  You've got to either get the air out
ahead of time (Adam's wet method) or keep the film OFF the pcb until
the laminator presses it down (my method).

Details of my method:

I flip the PCB over and lay the film next to it, with a 1/2 inch
overlap, and press the overlap part down.  Now I flip the PCB over and
fold the film along the attached edge.  Feed the attached edge into
the laminator and IMMEDIATELY grab the other two corners of the film
and peel it off the PCB.  Pull gently away from the laminator, and
apart, to keep the film smooth, and pull up some to keep it off the
pcb.  You want the film's first contact with the PCB to be at the
laminator's roller, so that no air bubbles are trapped.

Malcolm Parker-Lisberg <mparkerlisberg@...> writes:
> It's not the webmail, I copy and pasted the link into a blank browser
> page and got the same error. Deleting the jpg on this page and
> re-typing it worked and the pasted link then also worked when pasted
> into another new  blank page.

Sounds like your browser is trying too hard to preserve the referrer
info, which is what my server uses to try to guess if you're using my
images in your web page (I get a lot of people stealing my bandwidth
by doing that).

Anyway, replace the .jpg with .html and it always works.

Thanks for describing your process. If I try the dry film again, I will give that a try.

The pre-coated board sure worked good.  My exposure time ended up being 11 minutes per side with a dual bulb, 18 watt flourescent light.  The results were very good. I will have to do some experimenting with different light sources to see if I can speed up the exposure time but overall I am really happy with the results I got so far.  I just hope it wasn't beginners luck.

Chris




--- In Homebrew_PCBs@yahoogroups.com, DJ Delorie <dj@...> wrote:

>
> 
> "lcdpublishing" <lcdpublishing@...> writes:
> > TO clarify, using the dry film type stuff, I would get blisters -
> 
> If you lay the film flat on the pcb and run it through the laminator,
> you're going to get blisters.  You've got to either get the air out
> ahead of time (Adam's wet method) or keep the film OFF the pcb until
> the laminator presses it down (my method).
> 
> Details of my method:
> 
> I flip the PCB over and lay the film next to it, with a 1/2 inch
> overlap, and press the overlap part down.  Now I flip the PCB over and
> fold the film along the attached edge.  Feed the attached edge into
> the laminator and IMMEDIATELY grab the other two corners of the film
> and peel it off the PCB.  Pull gently away from the laminator, and
> apart, to keep the film smooth, and pull up some to keep it off the
> pcb.  You want the film's first contact with the PCB to be at the
> laminator's roller, so that no air bubbles are trapped.
>

I just got the "do not hotlink message" at the "correct link" so I'm giving up on it.

Donald.

----- Original Message -----
From: "Jack" <jack@...>
To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, August 5, 2009 8:40:09 AM GMT -05:00 US/Canada Eastern
Subject: Re: [Homebrew_PCBs] Need better reliability than I am getting with  toner transfer - what's next?

http://www.delorie.com/electronics/sdram/sdram-toppcb.jpg
      is the correct link and brings up the image correctly.


On Wed, Aug 5, 2009 at 7:14 AM, Malcolm Parker-Lisberg <
mparkerlisberg@...> wrote:

> The link below just gives a warning "please do not hotlink to this site"
>
>
> --- On Wed, 8/5/09, DJ Delorie <dj@...> wrote:
>
> From: DJ Delorie <dj@...>
> Subject: Re: [Homebrew_PCBs] Need better reliability than I am getting with
> toner transfer - what's next?
> To: Homebrew_PCBs@yahoogroups.com
> Date: Wednesday, August 5, 2009, 12:53 AM
>

[snip]

Thanks for the tip, Mike.  I got to see that which I had give up on and it is quite beautiful!

Donald.

----- Original Message -----
From: "Mike Phillips" <mikep_95133@...>
To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, August 5, 2009 11:28:01 AM GMT -05:00 US/Canada Eastern
Subject: [Homebrew_PCBs] Re: Need better reliability than I am getting with toner transfer - what's next?

I went back to Firefox. Deleted the letters jpg at the end of the "http://www.delorie.com/electronics/sdram/sdram-toppcb.jpg" URL, then typed them back in and hit enter and got the pcb pic to show up. 

Mike

[snip]

--- In Homebrew_PCBs@yahoogroups.com, "lcdpublishing" <lcdpublishing@...> wrote:
>
> TO clarify,  using the dry film type stuff, I would get blisters - sometimes.  Nothing consistant about it from what I could determine.  I could easily manipulate the dry film onto the board without bubbles (small boards) but after running through the laminator, blisters would appear and those never turned out good.
> 
> Other times I would have a simple break in a trace as if there was a cut line in the resist material (toner or dry film).  
> 

I had similar problems. The wet method did not work well for me. What did work for me is a J-roller. This is normally is used for applying laminate to counter tops. You should be able to find it at any hardware store.

You do not use the roller  to push the bubbles out like you would do with a counter top. Instead hold the resist at the edge of the board and off the board. Push forward with the J-roller and let it press the photoresist on to the board. No air bubbles can get trapped. 

You still need to run the board though the laminator to activate the adhesive.

Once I started doing it this way, I have had no problem with air getting trapped under the photoresist.