Homebrew_PCBs

> Has anyone ever tried to homebrew a flex circuit. It would seem to be a
> similiar process except for finding copper coated kapton film. I wonder
> if one could get prelaminated kapton, or if one has to do it themselves.
> The copper bonding is probably a real pain due to the slipperiness of
> kapton. I'd like to give it a try, but any pointers would be appreciated.
>
> Thanks
> Ron
>
> [Non-text portions of this message have been removed]
>
>
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----- Original Message -----
From: "Stefan Trethan" <stefan_trethan@...>
To: <homebrew_pcbs@yahoogroups.com>
Sent: Wednesday, July 16, 2003 3:02 PM
Subject: Re: [Homebrew_PCBs] flex circuits by hand?


> never did. never thought of.
>
> i wonder what use you might have for this?
> i think it would be damn hard to get components on it so they don't peel
> off the copper film when bent.
> and if only used stationary, at a certain amount of bending, i see no
> reason why not using thin fr4.
>
> please tell me what you want to use it for.
>
>
> regards
> stefan
>
> On Wed, 16 Jul 2003 11:03:39 -0500, Ron Amundson
<ron_amundson@...>
> wrote:
>
> > Has anyone ever tried to homebrew a flex circuit. It would seem to be a
> > similiar process except for finding copper coated kapton film. I wonder
> > if one could get prelaminated kapton, or if one has to do it themselves.
> > The copper bonding is probably a real pain due to the slipperiness of
> > kapton. I'd like to give it a try, but any pointers would be
appreciated.
> >
> > Thanks
> > Ron
> >
> > [Non-text portions of this message have been removed]
> >
> >
>
Why flex circuits:
Packaging issues and cost, they are pretty common in consumer goods, and
extremely common in the world of hard drives etc. One gets rid of a lot of
connections and can make the circuitry far smaller than would be possible
with a rigid board. As far as componenets and pcb fracturing, with the
commerical boards, its not a problem, but it may be a huge exercise in
frustration from a DIY standpoint, as I wonder if they do some type of
annealing of the copper prior to lamination to the kapton.

Thin FR4 does not lend itseof to the bend radius I need. You are correct
that one would not want the circuit to flex in the vicinty of components.
However the IO leads can flex as long as the component area is held
stationary.

I can get some proto's done for around $1500, and it seems worth trying to
homebrew it, as If I can acheive success in a couple days its worthwhile,
otherwise there goes my $1500...

Thanks
Ron

On Wednesday 16 July 2003 09:03 am, Ron Amundson wrote:
> Has anyone ever tried to homebrew a flex circuit. It would seem to be a
> similiar process except for finding copper coated kapton film. I wonder if
> one could get prelaminated kapton, or if one has to do it themselves. The
> copper bonding is probably a real pain due to the slipperiness of kapton.
> I'd like to give it a try, but any pointers would be appreciated.
>
> Thanks
> Ron

--- In Homebrew_PCBs@yahoogroups.com, Brian Pitt <bfp@e...> wrote:
> I tried a crude test that didn't work out too well so I can tell ya
one
> way that wont do it :)
>
> I used 'slug tape' its an adhesive backed copper foil the critters
don't
> like to crawl over and stuck a strip of it down on a sheet of paper
thinking
> I could laser print the traces directly and etch , I would have
used overhead
> transparency film for the backing if it worked
> unfortunately the toner doesn't stick well to the copper so it
would get
> layed down in the right place then either stick to the hot roller
and get
> redeposited further down the page or just barely stick to the copper
> and peal off once it came out
>
> it might have worked better if I had roughed up the copper surface
a bit
> but I had a feeling it wasnt going to do that much better
>
> it was worth a shot anyway ,maybe if you used a photo resist
instead?
>
> Brian
> --
> "Nemo me impune lacesset"
>
> On Wednesday 16 July 2003 09:03 am, Ron Amundson wrote:
> > Has anyone ever tried to homebrew a flex circuit. It would seem
to be a
> > similiar process except for finding copper coated kapton film. I
wonder if
> > one could get prelaminated kapton, or if one has to do it
themselves. The
> > copper bonding is probably a real pain due to the slipperiness of
kapton.
> > I'd like to give it a try, but any pointers would be appreciated.
> >
> > Thanks
> > Ron

----- Original Message -----
From: "Stefan Trethan" <stefan_trethan@...>
To: <homebrew_pcbs@yahoogroups.com>
Sent: Thursday, July 17, 2003 4:33 AM
Subject: Re: [Homebrew_PCBs] flex circuits by hand?


> thanks for that info about the purposes.
> i still do not like this flexible stuff.
> not for soldering components on it. as cable it is ok.
> but thats only my opinion.
>
> i guess you already read this:
>
> http://www.pcbspecialist.com/EBasematerial.htm
>
> search for flexible.
>
> may need writing some mails but may result in some samples?
>
>
> especially this note may be interesting: (Rolled ultra thin FR4 for
> flexible applications).
> it at matsushita...
>
> i would try this if it is flexible enough/can be used as cable/connector.
> because it should be the same to use as thick fr4, i do not trust this
> plastic foil things very much ;-).
>
> keep us informed please if you get something.
>
>
> there are loads of "flexible material" providers in the above list url.
> if you check all homepages and write a mail to every interesting one you
> get some samples for sure.
>
> check all and choose the best. i think the materials may need photoresist
> coating done by you.
> this is no problem i think. but putting the copper on i would not think to
> be possible so easy.
>
>
> hope you find some material...
>
> regards
> stefan
Stefan, thanks for the URL, (I had missed it) it is very informative. The
best part is that a number of the companies are local, and I guess i never
even thought that they made flex materials. I toured Isola during one of our
IEEE meetings a couple years ago, looks like I will need to talk with them
again.

You might be onto something with the soldering. In reflow, the temps are
failry well controlled, but during hand operations, it would seem pretty
easy to over temp the laminate and cause all sorts of failure modes.

You also asked about my applications. The first one is a dual planar
antenna. I'd rather use a flex circuit in that the mechanical geometries are
easier to deal with, and I want to find out the effective impedance as a
function of physical distortion. It doesn't lend itself to modeling at least
not with my old version of NEC, and hopefully I can play with the geometry
such that when I switch to FR4 and recalculate the basic geometry, I will
find critical areas where tolerance must be held. Otherwise, I would
probably go through a whole panel of FR4 planar antennas trying to determine
the critical geometry, as the antenna will be a 3D structure.

The 2nd application is a flexible light bar, sort of along the line of a
roll up keyboard, but that can be bent to fit into small recesses on my car
when doing repair work. I played with a fleixble exit sign light that uses
incandescents in a fleixible plastic tube, but the illumination is not very
uniform.

Thanks
Ron