Homebrew PCBs

I was wondering if this may ne a reasonable approach:

1 - Drill the blank copper clad board with slightly oversize holes.

2 - Squeeege conductive epoxy into the holes. Cure

3 - re drill the holes to the correct size

4 - electroplate, photo mask, then etch.

This assumes a CNC based drill with good repeatability. It could 
work with LPKF and other grinders, as well as home brews

I prefer the approach of not bothering to plate through my holes or
use eyelets.  I just make a via and take the trace to the "solder
side".  Stick some wire in the via and solder both sides.  This is
only necessary when you can't solder the pin on the component-side. 
Its not as pretty as PTHs but its pretty easy and quite reliable.

eyelets or plating through just seem to be a lot of extra work.

thespeakerguy wrote:
> 
> I was wondering if this may ne a reasonable approach:
> 
> 1 - Drill the blank copper clad board with slightly oversize holes.
> 
> 2 - Squeeege conductive epoxy into the holes. Cure
> 
> 3 - re drill the holes to the correct size
> 
> 4 - electroplate, photo mask, then etch.
> 

Lets assume this method can make reliable through holes it would require 
more work than conventional PTH processes. The step of "making holes 
plateable" is only just part of the overall PTH process.

That sounds like an interesting approach to getting a plated through hole.  However, any epoxy smeared on the surface of the board will kill the etching process - you won't be able to etch the base foil.

Otherwise this is what was known as "tent and etch."  Just use a good heavy dry film that will cover and protect the through hole plating. 

  ----- Original Message ----- 
  From: thespeakerguy 
  To: Homebrew_PCBs@yahoogroups.com 
  Sent: Tuesday, October 19, 2004 2:20 AM
  Subject: [Homebrew_PCBs] An alternative TP hole approach?



  I was wondering if this may ne a reasonable approach:

  1 - Drill the blank copper clad board with slightly oversize holes.

  2 - Squeeege conductive epoxy into the holes. Cure

  3 - re drill the holes to the correct size

  4 - electroplate, photo mask, then etch.

  This assumes a CNC based drill with good repeatability. It could 
  work with LPKF and other grinders, as well as home brews





  Be sure to visit the group home and check for new Bookmarks and files:
  http://groups.yahoo.com/group/Homebrew_PCBs 


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

--- In Homebrew_PCBs@yahoogroups.com, "thespeakerguy" 
<thespeakerguy@y...> wrote:
> 
> I was wondering if this may ne a reasonable approach:
> 
> 1 - Drill the blank copper clad board with slightly oversize holes.
> 
> 2 - Squeeege conductive epoxy into the holes. Cure
> 
> 3 - re drill the holes to the correct size
> 
> 4 - electroplate, photo mask, then etch.
> 
> This assumes a CNC based drill with good repeatability. It could 
> work with LPKF and other grinders, as well as home brews


I would think the holes would need to be large.  If the hole were 
thin, it would not stand up to the presures in re-drilling and would 
probably rip out of the hole.  I think I would put a hole next to a 
hole.  The first for epoxy to make a bridge, then one for the part.  
That way, re-drilling is not critical.

Considder what Stefan said many months ago.

Look at your board.  A resistor can be soldered on both sides, thus 
connecting traces, thus eleminating a thru hole for that trace.    
With a cap and diode and transistor, it is quickly found that the 
unconnected traces are so few that the fix of bridging those 
remaining are not a problem.

If you look at your epoxy idea, that could be for those hard to 
connect traces.    My question is the reliability of the epoxy joint 
on conductivity.

Dave

IMO, plated through holes are more trouble than they're worth for small home projects.  Most of my designs have at most 12 ICs and are only a few inches on a side.  If you only need a few holes, it's easier just to route the circuits to a convenient spot and solder a wire from side to side.  You probably can get away with using resistor and cap leads for vias, but I wouldn't want to heat an active component lead twice.  If you have a lot of holes to do, consider going to a prototype shop.   They may cost a bit, but you'll avoid going nuts.  Even the Chinese have given up on using eyelets because it's too labor intensive.

Electroless copper is not a process for home brew boards.  Even the top notch pros have problems getting that process to work reliably.  After surface contamination, electroless copper was my biggest source of problems.

  ----- Original Message ----- 
  From: Adam Seychell 
  To: Homebrew_PCBs@yahoogroups.com 
  Sent: Tuesday, October 19, 2004 4:31 AM
  Subject: Re: [Homebrew_PCBs] An alternative TP hole approach?


  thespeakerguy wrote:
  > 
  > I was wondering if this may ne a reasonable approach:
  > 
  > 1 - Drill the blank copper clad board with slightly oversize holes.
  > 
  > 2 - Squeeege conductive epoxy into the holes. Cure
  > 
  > 3 - re drill the holes to the correct size
  > 
  > 4 - electroplate, photo mask, then etch.
  > 

  Lets assume this method can make reliable through holes it would require 
  more work than conventional PTH processes. The step of "making holes 
  plateable" is only just part of the overall PTH process.


  Be sure to visit the group home and check for new Bookmarks and files:
  http://groups.yahoo.com/group/Homebrew_PCBs 


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              ADVERTISEMENT
             
       
       


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

Agreed, a difficult and time consuming process. I make many boards 
with fine pitch SMT such as 0.5mm lead pitch QFNs, and it would be 
nice to not lose the vias every time you change the IC.

Signed;

Still searching in Silicon Valley :-)