Homebrew PCBs

DJ,

Your site mentions making four layer boards.  How do you make them?  Are
they two two layer boards glued together?  How do you handle vias?  

"The test board is a four-layer board because it vastly simplifies the power
system, and I can make them at home as long as they're not too complex."

http://www.delorie.com/electronics/sdram/

Jeff

"'Jeff Heiss' jeff.heiss@... [Homebrew_PCBs]"
<Homebrew_PCBs@yahoogroups.com> writes:
> Your site mentions making four layer boards. How do you make them? Are
> they two two layer boards glued together? How do you handle vias? 
>
> “The test board is a four-layer board because it vastly simplifies the
> power system, and I can make them at home as long as they're not too
> complex.”
>
> http://www.delorie.com/electronics/sdram/

Double-sided sticky tape.  Really.  I got some sheets of 3M double-sided
adhesive film on eBay (the stuff they use to stick front panels on
stoves, etc).  IIRC for that project I etched four single-sided 0.005"
or so thick single-sided "boards" (this is the prepreg they use for
many-layer boards, also from eBay).  I then pre-drilled the outer layers
for the blind and buried vias (the inner layers were just vcc and gnd,
so I was just exposing them so I could solder to them), taped the layers
together, and drilled the through-holes.

Note: stick the tape to the outer layers FIRST, then drill the clearance
holes in those layers (i.e. you're drilling through the tape).
Otherwise you expose copper that's still covered with tape ;-)

It might be better in the long run to use a standard two-sided board and
tape two prepregs to it, as four taped prepregs gave me a pretty
flimsy/flexible resulting board, which led to some solder breakage over
time.

For the blind vias, no through-hole was drilled.  I just shoved some
solder paste in the clearance hole in the top layer, poked in some 30ga
wire, and melted it with a small soldering iron tip, soldering the top
copper to the exposed copper right under it.

For "buried" vias (outer layer to far-side-power), I just drilled a big
hole in the (unused) far layer to expose the vcc/gnd pad, and treated it
like a through-via.

I’m contemplating blind vias by running wire though all layers, soldering the wires on the inner layers, and lastly soldering the outer layers.  I think your idea is better though.

 

I don’t see prepreg on Ebay.  Does it have any other names?

 



 

Jeff

From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com] 
Sent: Tuesday, January 26, 2016 7:23 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] homemade four layer boards

 

  


"'Jeff Heiss' jeff.heiss@comcast.net [Homebrew_PCBs]"
<Homebrew_PCBs@yahoogroups.com> writes:
> Your site mentions making four layer boards. How do you make them? Are
> they two two layer boards glued together? How do you handle vias? 
>
> “The test board is a four-layer board because it vastly simplifies the
> power system, and I can make them at home as long as they're not too
> complex.”
>
> http://www.delorie.com/electronics/sdram/

Double-sided sticky tape. Really. I got some sheets of 3M double-sided
adhesive film on eBay (the stuff they use to stick front panels on
stoves, etc). IIRC for that project I etched four single-sided 0.005"
or so thick single-sided "boards" (this is the prepreg they use for
many-layer boards, also from eBay). I then pre-drilled the outer layers
for the blind and buried vias (the inner layers were just vcc and gnd,
so I was just exposing them so I could solder to them), taped the layers
together, and drilled the through-holes.

Note: stick the tape to the outer layers FIRST, then drill the clearance
holes in those layers (i.e. you're drilling through the tape).
Otherwise you expose copper that's still covered with tape ;-)

It might be better in the long run to use a standard two-sided board and
tape two prepregs to it, as four taped prepregs gave me a pretty
flimsy/flexible resulting board, which led to some solder breakage over
time.

For the blind vias, no through-hole was drilled. I just shoved some
solder paste in the clearance hole in the top layer, poked in some 30ga
wire, and melted it with a small soldering iron tip, soldering the top
copper to the exposed copper right under it.

For "buried" vias (outer layer to far-side-power), I just drilled a big
hole in the (unused) far layer to expose the vcc/gnd pad, and treated it
like a through-via.

"'Jeff Heiss' jeff.heiss@... [Homebrew_PCBs]"
<Homebrew_PCBs@yahoogroups.com> writes:
> I don’t see prepreg on Ebay. Does it have any other names?

It's hard to find but I search for "copper clad laminate fr4 single" or
variations on those terms.  The most common thickness is 1.5mm (1/16")
but some places offer thinner ones.  Example:

http://www.ebay.com/itm/120802756087

> Ever considered to make an Instructable on your method? 
> Would be great!

I did it once to see if I could.  I could.  It's generally not worth the
effort though, and the vias were a nightmare.