Homebrew PCBs

Hello people,
  I've been trying to use a flat bed plotter and "pens" to fabricate PCBs for some time now. I've come to the conclusion that all ink pens suck for this method. Even the best pen results fail right before the etching is complete, they just don't have enough bonding strength in acid. I love this PCB fabrication method, I just need a pen that will work. I seem to have the best luck with red pens and I know that red dye has the most solids in it.   Anyway,  In my frustration I decided to try to build a high-resolution paint pen for the plotter. I had my wife bring home some tuberculin syringes with a #25 and #28 needle on them. I cut the needle at the base and polished it with my dremel. I then mounted it in a Roland DXY1100 plotter and filled the syringe via an extra syringe with screen printing ink thinned to right viscosity to produce a drip every 30 seconds or so. This is just the right amount of ink to produce very solid lines with nice heavy ink deposits without
 blotting.  I was getting at least a 0.025" resolution with #25 needle and should be able to do better with a #28. As for the etching I just put the PCB board in some Muratic acid - persulfate is very slow...., Ferric is OK, and Muratic/peroxide mix is very very fast, almost violent, and I like instant gratification ;-) I was etching in my shop with a ambient of 16F last night so even Muratic etching was very slow.  This step was always the 'time of truth' for the pen methods. It always resulted with the ink lifting off the copper just before the PCB was finished etching.  I left my new PCB in acid for 40 minutes and no ink left the PCB with no surface degradation of ink also. This will be my new preferred system from now on. I just want to share my results because I'm sure others are trying the same method.
  Thanks, Dan

 
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On Thu, 11 Jan 2007 16:58:19 +0100, Dan Pickard <dlpwebmail@...>  
wrote:

> Hello people,
>   I've been trying to use a flat bed plotter and "pens" to fabricate  
> PCBs for some time now. I've come to the conclusion that all ink pens  
> suck for this method. Even the best pen results fail right before the  
> etching is complete, they just don't have enough bonding strength in  
> acid. I love this PCB fabrication method, I just need a pen that will  
> work. I seem to have the best luck with red pens and I know that red dye  
> has the most solids in it.   Anyway,  In my frustration I decided to try  
> to build a high-resolution paint pen for the plotter. I had my wife  
> bring home some tuberculin syringes with a #25 and #28 needle on them. I  
> cut the needle at the base and polished it with my dremel. I then  
> mounted it in a Roland DXY1100 plotter and filled the syringe via an  
> extra syringe with screen printing ink thinned to right viscosity to  
> produce a drip every 30 seconds or so. This is just the right amount of  
> ink to produce very solid lines with nice heavy ink deposits without
>  blotting.  I was getting at least a 0.025" resolution with #25 needle  
> and should be able to do better with a #28. As for the etching I just  
> put the PCB board in some Muratic acid - persulfate is very slow....,  
> Ferric is OK, and Muratic/peroxide mix is very very fast, almost  
> violent, and I like instant gratification ;-) I was etching in my shop  
> with a ambient of 16F last night so even Muratic etching was very slow.   
> This step was always the 'time of truth' for the pen methods. It always  
> resulted with the ink lifting off the copper just before the PCB was  
> finished etching.  I left my new PCB in acid for 40 minutes and no ink  
> left the PCB with no surface degradation of ink also. This will be my  
> new preferred system from now on. I just want to share my results  
> because I'm sure others are trying the same method.
>   Thanks, Dan


Hi,

You can actually buy metal-tipped plotter pens. Even with carbide tips.  
They have a little spring-loaded wire sitting inside the thin tube. Some  
also have X shaped grooves on the end to aid in inkflow. I got them from  
ebay.

I tried them with a plotter and staedtler red ink but it would not hold up.


ST

I thought about the same method with using syringes, my wife is a 
nurse.  I have seen some demos of pbc supply houses where they use a 
plotter with a air pressure operated needle to place solder paste, 
screen print liquid and solder mask on boards.

My thought is to use screen print ink or liquid conformal coating in 
the syringe and deposit it by setting the z axis on the cnc plotter 
to dispense the medium.  You would not have to thin it out, just set 
up a separate stepper on the Z axis to press the plunger.  Should 
give good control over the medium.

Just though of something.  What if you did the above,  but deposited 
etching paste to start etching the areas you did not want.  After 
laying down the paste, you could spray the board with acrylic/enamel 
paint as a mask, dry a few minutes with a hair dryer, wash the paste 
off then do your etching.  I will try latter today if I can.

Brian G.

>  Just though of something.  What if you did the above,  but deposited
>  etching paste to start etching the areas you did not want.  After
>  laying down the paste, you could spray the board with acrylic/enamel
>  paint as a mask, dry a few minutes with a hair dryer, wash the paste
>  off then do your etching.  I will try latter today if I can.

Would that not damage the needle? how about a grease before spraying,
can you taste its not butter.....

At 08:07 AM 1/12/2007, you wrote:

> > Just though of something. What if you did the above, but deposited
> > etching paste to start etching the areas you did not want. After
> > laying down the paste, you could spray the board with acrylic/enamel
> > paint as a mask, dry a few minutes with a hair dryer, wash the paste
> > off then do your etching. I will try latter today if I can.
>
>Would that not damage the needle? how about a grease before spraying,
>can you taste its not butter.....


I was going to cut the point off of the needle.  BTW, using soft 
butter maybe a better/cheaper solution to using anything else.  I 
could just wash the board off with a little Dawn dish liquid to 
remove the grease!

Thanks,
Brian G.