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Combining single layer pcb's

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Jon Slaughter

Jan 1, 1970
0
I only have some single layer pcb's at the moment and would like to create
some double sided for a pcb fab in a day or so. Anyone have any good ideas
how to bond them? I doubt it is difficult and I imagine roughing up the
sides will work but I rather than go down that route unless it has to be
done.

Will most adheasives do the trick?
 
D

DJ Delorie

Jan 1, 1970
0
I have a stack of 3M double sided sticky tape sheets I use to do that.
It works, but the resulting PCB is only as rigid as the individual
layers were. I know others use epoxy, which adds rigidity.
 
J

Jon Slaughter

Jan 1, 1970
0
Tim said:
These are homemade boards so no solder mask right?

Right.

FR4 or G-10 is microscopically rough and epoxy adheres very very well.
It's a joy to build up assemblies out this stuff by using epoxy glue.

Would superglue work? I have various types of adheasives but don't want to
really test them out(stuff like that always turns into a mess).
Other crappy phenolics are sometimes mirror-smooth and you'll have to
rough it up for some adhesives. Spray-on contact adhesive will
probably work pretty good on smooth stuff, even without roughing it
up.

You don't give a damn about UL94-V0, right?

Right. I'm only interested in creating a double sided board so I don't have
to use wire traces and just for fun for testing. I have a lot of single
sided boards so I thought I'd give it a shot as it would be easier than
running a but of wire traces. on the back side of the board... Ok, not sure
if it would be easier or not but...
 
S

Spehro Pefhany

Jan 1, 1970
0
You could just use carpet (double-sided) tape. I'm sure it will work
well enough. Cut some pieces up and avoid the drilled holes otherwise
the leads will push adhesive onto themselves as they go through and
adversely affect the solderability.

Epoxy and cyanoacrylate (superglue) glues are brittle and may not
adhere as well to the PCB material.
 
K

krw

Jan 1, 1970
0
I only have some single layer pcb's at the moment and would like to create
some double sided for a pcb fab in a day or so. Anyone have any good ideas
how to bond them? I doubt it is difficult and I imagine roughing up the
sides will work but I rather than go down that route unless it has to be
done.

Will most adheasives do the trick?

I college we had a lathe that turned out single-sided boards. To make
double-sided we glued two together, as you propose. At the time
(early '70s), all the epoxies we found were too brittle, so we ended
up using RTV. The white RTV worked very well (clear less so) but,
unfortunately I was very sensitive to the acetic acid. I say
unfortunately because I was the undergrad grunt technician and the
boss didn't much care if I broke out in hives. :-( Today's RTVs
don't seem to use acetic acid, so... ;-)
 
A

Archimedes' Lever

Jan 1, 1970
0
Would superglue work? I have various types of adheasives but don't want to
really test them out(stuff like that always turns into a mess).


Right. I'm only interested in creating a double sided board so I don't have
to use wire traces and just for fun for testing. I have a lot of single
sided boards so I thought I'd give it a shot as it would be easier than
running a but of wire traces. on the back side of the board... Ok, not sure
if it would be easier or not but...

Use epoxy. It has better rigidity and better thermal characteristics
than some other adhesive would.

I would also work out the traces, and etch the boards BEFORE joining
them, as you do not want the etchant to migrate between them at all.
You should also do all your drilling, as punching through from the other
side will rip off traces. All drilling should be done through the copper
first, and very carefully using a sharp bit (plural for high hole count).
Fiberglass is harder than steel, and that is the predominate cause of
damage to boards by cheap PCB houses that are too damned scrooged up to
replace their bits at the right interval to keep the holes nice and
clean. You could do all your drilling prior to any etch cycle too, so
that you can insure match-ups between "layers". :)

I would take the finished boards (etched, drilled, etc.), add solder to
any traces that you feel need additional current carrying capacity,and
laminate strips of a cheap roll of 1" Kapton tape over those traces, or
the hole board if you want. This acts as a solder mask, AND insulated
traces from contact by components, etc. The only thing left exposed
would be the pads, annular rings and vias. The rest would have a nice
blanket over it. However... BEFORE your tape it up, take the ready
board with the HASLd traces :) and clean it very good in aqueous bath
if the flux was water clean, or hot alcohol if it was RMA flux. I would
not use no clean for any work other than spot level rework sessions.

ANYWAY, the idea is to get VERY clean boards *before* you laminate them
together. Final clean is in fresh, hot 99% alcohol, then BAKE the PCBs
for an hour in a minimum 60°C dry oven. PCB media is VERY hygroscopic,
so you want any and all trapped water out of the boards before you go
slapping them together for keeps.

After that final bake start using gloves to handle them.

Liquid nails sounds like a good choice, but you may want a good two
part construction epoxy. That way, YOU initiate the polymerization.
Liquid nails and off-the-shelf single part glues may not cure right.

OK, put epoxy on both mating faces. ALMOST squeegee off all of it from
both. Just don't push hard on the squeegee, which can be any clean line
edge on a piece of plastic. A plastic milk carton (jug) wall. Cut the
straight squeegee edge in one motion so it is a clean squeegee face.

Then, the amount you leave on the board will relate to the amount of
pressure you squeegee with.

Be sure to do the requirements analysis and think about any tie wrap
holes or the like you might want the board to have for strain relief of
incoming wires/cables, etc.

Don't count on a large pad area or a soldered edge to be enough to
station an added part. If connectors or other high mechanical stress
components that are typically for plated holes are used, you may need
extra bolstering to keep the soldered connections from failing from
flexure.

Plated holes are relied on for connector stationing in the industry,
and are designed with that in mind, and even your paired faces will
provide nowhere near the same capacity without plated holes. So, I would
think about things like that if you have anything that will be
experiencing any mechanical stresses.
 
E

ehsjr

Jan 1, 1970
0
Spehro said:
You could just use carpet (double-sided) tape. I'm sure it will work
well enough. Cut some pieces up and avoid the drilled holes otherwise
the leads will push adhesive onto themselves as they go through and
adversely affect the solderability.

Epoxy and cyanoacrylate (superglue) glues are brittle and may not
adhere as well to the PCB material.

Superglue works well for Manhattan Construction (I've used it), so it
ought to work for gluing two blanks together (I haven't done it).

For those not familiar with it, Manhattan Construction involves
gluing rectangular or circular PCB material pads onto the copper
side of a blank PCB. Point to point wiring is used between the
pads. If you make the pads from double sided PCB, you can solder
them in place - like surface mount - instead of using glue.

Ed
 
K

krw

Jan 1, 1970
0
I tried hardware store RTV and in my case my complaint was it took too
long to cure.

We'd set it up in the afternoon before goign home and it would be
ready by morning. The non-acetic acid setting silicone may take
longer but IME silicone caulk doesn't seem to.
However, iirc I spotted 2 part silicone in my travels.

Seems like a small market for that.
 
E

ehsjr

Jan 1, 1970
0
JeffM said:
ehsjr said:
[...]Manhattan Construction
involves gluing rectangular or circular PCB material pads
onto the copper side of a blank PCB.


That is not what I identify as the primary characteristic of that term
--nor even a necessary characteristic.

I guess you haven't done any "Manhattan Construction" boards. Using
pads and gluing (or soldering if you want, when pads are made from
double copper sided boards) _is_ what makes it "Manhattan Construction".

See any of the following sites, including the one you posted for the
description of "Manhattan Construction". I'll quote from the site
you mentioned after the list.

http://www.piclist.com/techref/pcb/manhattan.htm
http://www.eham.net/articles/16536
http://www.offcycle.org/index.php?option=com_content&task=view&id=43&Itemid=26
http://www.w7dk.org/ARDF ATTEN PROJ only SCREEN.pdf
http://www.arrl.org/news/features/2002/12/27/1/?nc=1
http://www.k8iqy.com/construction/ConstructionMethods.htm
http://www.cliftonlaboratories.com/Prototyping.htm#Manhattan_Construction_for_RF
http://k7qo.net/lab.pdf


When I think of this technique, I envision the skyline of NYC.
That is, the components are stood on their ends:
http://www.w7zoi.net/bboard.pdf
This can be done with standard perfboard
or with a purpose-built PWB (for a small footprint).

From the site you posted above, read the information it
contains. See page three, figure 2 and the text:
"Several other construction schemes offer similar grounding fidelity,
including those where small pads of circuit board material
are glued or soldered to the ground foil. These pads then have
components soldered to them. I've found this to be useful when a
slightly massive component such as a floating (non grounded) trimmer
capacitor is used. The specific glue type has little impact on
circuit performance. Variations of this method have been called
"Manhattan Construction," and can be mixed with other breadboarding
schemes."

Ed
 
K

krw

Jan 1, 1970
0
Superglue works well for Manhattan Construction (I've used it), so it
ought to work for gluing two blanks together (I haven't done it).

For those not familiar with it, Manhattan Construction involves
gluing rectangular or circular PCB material pads onto the copper
side of a blank PCB. Point to point wiring is used between the
pads. If you make the pads from double sided PCB, you can solder
them in place - like surface mount - instead of using glue.

I've never seen "Manhattan" overloaded for that sort of construction.
"Manhattan Routing" is done using wiring at right angles, rather than
"as the crow flies", and "Manhattan Distance" is the distance from
point-A to point-B at right angles. "Manhattan" here being limited to
the streets and avenues since leaping over tall buildings isn't
allowed. Your "Hanhattan construction" doesn't seem to fit on the
same island. ;-)
 
E

ehsjr

Jan 1, 1970
0
krw said:
I've never seen "Manhattan" overloaded for that sort of construction.
"Manhattan Routing" is done using wiring at right angles, rather than
"as the crow flies", and "Manhattan Distance" is the distance from
point-A to point-B at right angles. "Manhattan" here being limited to
the streets and avenues since leaping over tall buildings isn't
allowed. Your "Hanhattan construction" doesn't seem to fit on the
same island. ;-)


You can see photos of it here:
http://members.ziggo.nl/cmulder/nc20.htm
http://www.qsl.net/k8gd/images/2N2_30_VFO.jpg

And this site shows it sort of step by step with photos:
http://www.piclist.com/techref/pcb/manhattan.htm

Enjoy.

Ed
 
J

JosephKK

Jan 1, 1970
0
I only have some single layer pcb's at the moment and would like to create
some double sided for a pcb fab in a day or so. Anyone have any good ideas
how to bond them? I doubt it is difficult and I imagine roughing up the
sides will work but I rather than go down that route unless it has to be
done.

Will most adheasives do the trick?
I would not even bother, i would just buy some double sided.
 
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