Combining single layer pcb's

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.

e

deas

These are homemade boards so no solder mask 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.

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?

Tim.

Some epoxies have more flex that others.

D from BC Amateur smps designer. British Columbia, Canada Posted to usenet sci.electronics.design

Right.

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...

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.

o

Superglue and hotmelt glue are both TERRIBLE at solder temperatures. Gummy floods and vapors that repel solder and flux.

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... ;-)

I tried hardware store RTV and in my case my complaint was it took too long to cure. However, iirc I spotted 2 part silicone in my travels.

D from BC Amateur smps designer. British Columbia, Canada Posted to usenet sci.electronics.design

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.

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

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.

Seems like a small market for that.

That is not what I identify as the primary characteristic of that term

--nor even a necessary characteristic. When I think of this technique, I envision the skyline of NYC. That is, the components are stood on their ends:

This can be done with standard perfboard or with a purpose-built PWB (for a small footprint).

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.

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

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. ;-)

That's the common terminology in amateur-radio homebrewing circles, where such construction is relatively common.

It's also sometimes referred to as "ugly" construction.

--
Dave Platt                                    AE6EO
Friends of Jade Warrior home page:  http://www.radagast.org/jade-warrior
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You can see photos of it here:

And this site shows it sort of step by step with photos:

Enjoy.

Ed

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I would not even bother, i would just buy some double sided.