Homebrew PCBs

Using, in this example, a 2 sided positive acting pre-sensitized board. I have well constructed frame to hold the pcb and film in place while exposing to light.  
How would you go about getting both sides ready for etching?  So far I see side 1 being exposed.  After that comes ( and this is where I am asking about the process order) developing of side 1 circuit, drilling registration holes, exposing side 2, developing side 2.  Last step of course is etching.  
I am concerned about the handling of the board during these processes.  The frame is tight, and I don't want to be scratching or scraping away any of the resist while messing around.

As an example, do I drill registration holes prior to any exposure at all, side 1 or side 2?  Do I develop both sides at same time? 
Or, do I do side 1 exposure, develop, drill registration, and then move to side 2?  This makes me wonder, can I develop side 1 and later do side 2?  Will that double dipping mess up the first developing?

Regarding the registration.  How will I keep the film from sliding around and become off target while placing in the exposure frame.  Can't use pins, unless I cut them short enough to hold the film to the board, but not extend pass the board.  Do I glue the film to the board?  Tension on the pcb/film is supplied by the frame via sliding the back panel of the frame across the back side of the pcb.  This creates a shear that will move things around.

Barry,
I have done a lot of DYI two sided boards. My tecnique was to form a envleope or pocket from the top and bottom side films.  Its best to have the films 50 to 100 percent larger than the board outline.  Lay the films emulsion side to emulsion side together on a light table and register the two sides.  Then scotch tape them on together on 3 sides to form the envleope.  I would then slip the board in the film envelope centering it on my board outline tick marks. I had a two sided UV exposure box that would clamp the film and board between two pieces of glass so I could expose both sides at once.  Then develop and etch. Worked great, registration was perfect.

Craig

--- In Homebrew_PCBs@yahoogroups.com, "demers_barry" <sdad@...> wrote:

>
> Using, in this example, a 2 sided positive acting pre-sensitized board. I have well constructed frame to hold the pcb and film in place while exposing to light.  
> How would you go about getting both sides ready for etching?  So far I see side 1 being exposed.  After that comes ( and this is where I am asking about the process order) developing of side 1 circuit, drilling registration holes, exposing side 2, developing side 2.  Last step of course is etching.  
> I am concerned about the handling of the board during these processes.  The frame is tight, and I don't want to be scratching or scraping away any of the resist while messing around.
> 
> As an example, do I drill registration holes prior to any exposure at all, side 1 or side 2?  Do I develop both sides at same time? 
> Or, do I do side 1 exposure, develop, drill registration, and then move to side 2?  This makes me wonder, can I develop side 1 and later do side 2?  Will that double dipping mess up the first developing?
> 
> Regarding the registration.  How will I keep the film from sliding around and become off target while placing in the exposure frame.  Can't use pins, unless I cut them short enough to hold the film to the board, but not extend pass the board.  Do I glue the film to the board?  Tension on the pcb/film is supplied by the frame via sliding the back panel of the frame across the back side of the pcb.  This creates a shear that will move things around.
>

Just sent off a post reply talking about the sandwich method.  I'll need to
try that.  Double sided exposure.  I will need a different press for holding
the work while exposing.  Mine has a metal back.  What do you use? Homemade,
or commercial?  In fact, now that I think a bit more, my exposure is
vertically oriented, in other words I place my light horizontally 12" above
the pcb. which I have sitting on the counter top.  Your method will require
the lights and the pcb to be standing up, not lying down.  At least, that is
the way I'm envisioning it.  Thats ok, no biggy, just trying to get a feel
for this.  That double light thing is exciting me, gotta do that.
Please fill me in on your clamping method.

On Fri, Feb 12, 2010 at 3:33 PM, designer_craig <cs6061@...> wrote:

>
>
> Barry,
> I have done a lot of DYI two sided boards. My tecnique was to form a
> envleope or pocket from the top and bottom side films. Its best to have the
> films 50 to 100 percent larger than the board outline. Lay the films
> emulsion side to emulsion side together on a light table and register the
> two sides. Then scotch tape them on together on 3 sides to form the
> envleope. I would then slip the board in the film envelope centering it on
> my board outline tick marks. I had a two sided UV exposure box that would
> clamp the film and board between two pieces of glass so I could expose both
> sides at once. Then develop and etch. Worked great, registration was
> perfect.
>
> Craig
>
> --- In Homebrew_PCBs@yahoogroups.com <Homebrew_PCBs%40yahoogroups.com>,
> "demers_barry" <sdad@...> wrote:
> >
> > Using, in this example, a 2 sided positive acting pre-sensitized board. I
> have well constructed frame to hold the pcb and film in place while exposing
> to light.
> > How would you go about getting both sides ready for etching? So far I see
> side 1 being exposed. After that comes ( and this is where I am asking about
> the process order) developing of side 1 circuit, drilling registration
> holes, exposing side 2, developing side 2. Last step of course is etching.
> > I am concerned about the handling of the board during these processes.
> The frame is tight, and I don't want to be scratching or scraping away any
> of the resist while messing around.
> >
> > As an example, do I drill registration holes prior to any exposure at
> all, side 1 or side 2? Do I develop both sides at same time?
> > Or, do I do side 1 exposure, develop, drill registration, and then move
> to side 2? This makes me wonder, can I develop side 1 and later do side 2?
> Will that double dipping mess up the first developing?
> >
> > Regarding the registration. How will I keep the film from sliding around
> and become off target while placing in the exposure frame. Can't use pins,
> unless I cut them short enough to hold the film to the board, but not extend
> pass the board. Do I glue the film to the board? Tension on the pcb/film is
> supplied by the frame via sliding the back panel of the frame across the
> back side of the pcb. This creates a shear that will move things around.
> >
>
>  
>



-- 
Thank you,

Barry


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

My exposure box was about 20" long and about 12" wide and 8" tall.  It was fabricated out of some 3/4" pine with 1/4 plywood bottom painted white on the inside. It was built in two sectons, upper and lower both had plywood bottoms.  Three 18" UV FL tubes were mounted (actually just glued with RTV) to the plywood bottoms on both the upper and lower box. (6 total tubes)  The lower box had a lip cut in the edge of the sides so a piece of glass would sit down flush with the top edge of the sides. I had a second piece of 1/4" glass to drop down on top of the first to sanwich the board and envelope between the glass.  The upper glass sheet was drilled for four clamping screws but I would not do that again, too easy the break the glass. I would come up with some external clamping system.   To use, you lift of the upper box, take off the upper glass, put you board and envelope on the lower glass aligning the board in the envelope, place on the upper glass and clamp down.  Set the upper box on top and turn on the timer.  Was easy to build, only things I had to buy was the lamps, balasts and glass; had the timer and wood.

Sad thing, I threw it in the dump about 8 years back when I didn't think I would be doing any more boards, now I wish I still had it as I have started doing boarda again.  My current plan is to go to direct UV immaging of the dry film or AQ3000 spun coated boards from the Gerber file and skip the film all together.

Craig

Craig




--- In Homebrew_PCBs@yahoogroups.com, Barry Demers <sdad@...> wrote:

>
> Just sent off a post reply talking about the sandwich method.  I'll need to
> try that.  Double sided exposure.  I will need a different press for holding
> the work while exposing.  Mine has a metal back.  What do you use? Homemade,
> or commercial?  In fact, now that I think a bit more, my exposure is
> vertically oriented, in other words I place my light horizontally 12" above
> the pcb. which I have sitting on the counter top.  Your method will require
> the lights and the pcb to be standing up, not lying down.  At least, that is
> the way I'm envisioning it.  Thats ok, no biggy, just trying to get a feel
> for this.  That double light thing is exciting me, gotta do that.
> Please fill me in on your clamping method.
> 
> On Fri, Feb 12, 2010 at 3:33 PM, designer_craig <cs6061@...> wrote:
> 
> >
> >
> > Barry,
> > I have done a lot of DYI two sided boards. My tecnique was to form a
> > envleope or pocket from the top and bottom side films. Its best to have the
> > films 50 to 100 percent larger than the board outline. Lay the films
> > emulsion side to emulsion side together on a light table and register the
> > two sides. Then scotch tape them on together on 3 sides to form the
> > envleope. I would then slip the board in the film envelope centering it on
> > my board outline tick marks. I had a two sided UV exposure box that would
> > clamp the film and board between two pieces of glass so I could expose both
> > sides at once. Then develop and etch. Worked great, registration was
> > perfect.
> >
> > Craig
> >
> > --- In Homebrew_PCBs@yahoogroups.com <Homebrew_PCBs%40yahoogroups.com>,
> > "demers_barry" <sdad@> wrote:
> > >
> > > Using, in this example, a 2 sided positive acting pre-sensitized board. I
> > have well constructed frame to hold the pcb and film in place while exposing
> > to light.
> > > How would you go about getting both sides ready for etching? So far I see
> > side 1 being exposed. After that comes ( and this is where I am asking about
> > the process order) developing of side 1 circuit, drilling registration
> > holes, exposing side 2, developing side 2. Last step of course is etching.
> > > I am concerned about the handling of the board during these processes.
> > The frame is tight, and I don't want to be scratching or scraping away any
> > of the resist while messing around.
> > >
> > > As an example, do I drill registration holes prior to any exposure at
> > all, side 1 or side 2? Do I develop both sides at same time?
> > > Or, do I do side 1 exposure, develop, drill registration, and then move
> > to side 2? This makes me wonder, can I develop side 1 and later do side 2?
> > Will that double dipping mess up the first developing?
> > >
> > > Regarding the registration. How will I keep the film from sliding around
> > and become off target while placing in the exposure frame. Can't use pins,
> > unless I cut them short enough to hold the film to the board, but not extend
> > pass the board. Do I glue the film to the board? Tension on the pcb/film is
> > supplied by the frame via sliding the back panel of the frame across the
> > back side of the pcb. This creates a shear that will move things around.
> > >
> >
> >  
> >
> 
> 
> 
> -- 
> Thank you,
> 
> Barry
> 
> 
> [Non-text portions of this message have been removed]
>