Homebrew_PCBs

Hi, Markus

I am also a homebrewer and like to handle the PTH thing also myself.

Got on this moment only two questions:
1: the cuvets (fluid units)where they made off and how they glued
together (type of gleu)

2: chemical 1# part, is it electroless chem. cu. because some systems
use a pasta
if it is possible the names of the chems.

i already use dry film - spray etch and cnc drilling and works for
several years now .

many greatfull thanks in adv.

Roel

--- In Homebrew_PCBs@yahoogroups.com, Markus Zingg <m.zingg@n...>
wrote:

> >Markus, and others who have done these things on a limited budget:
> >Would you please describe your process, or provide a pointer to

some

> >such description on the web?
>
> Adam and I both have independantly developped a through hole plating
> setup. I can't tell much about Adam's (I figure though he will give
> you informations) but I do have a page set up that showes the

station

> I built on my own.
>
> www.myhome.ch/mzingg/pcbstuff/tps
>
> The pages are not absolutely up to date but should give lot's of
> information. With my "apraoch" the key point to understand is that I
> do not mix my chemicals "on my own" but use the same chemistry as

it's

> deliverd to board houses. I have mine from Bungard, but it seems

like

> they have it from "J-Kem International" (who ever this might be). I
> don't care cause those huge firms usually don't deliver small enough
> quantities as Bugnard does. Another way might be to contact a board
> house and ask if they mey sell some of their chemistry. I figure

they

> may do once they understand that this is about hobbyists use etc.
>
> The remaining part then is to create the tanks and the electronics
> needed for agitation and mainly for the electrolytic process itself.
>
> Once these "investments" are made, producing throughplates PCB's
> becomes very cheap, painless and fast. All you need is copper clated
> material and of course laminate. There is thin copper clated FR4
> material available also at reasonable prices. I use 0.5mm for the
> inner layer and 0.3mm for the outer layers in case of a four layer
> board thereby getting four layer board of the same thinkness as

those

> made by boardhouses.
>
> The process is not that different from creating double sided PCB's

in

> that you first laminate, expose and developp and etch the inner

layer,

> then glue the outer layers onto the two sides. Then you drill holes
> (not before this) so as the drill goes through the copper of the

inner

> layers at those places where it should (the layout must be made so

as

> the pads don't have holes). If you then through plate this "stack"

the

> outer surfaces are conneted to the inner layers whre they should.

From

> this point on there is no difference in createing a double sided

PCB,

> that said you simply laminate the outer layers, expose and developp
> and etch it.
>
> A key point is aligning the layers. I do this with two special
> diagonaly psoitioned holes of 3mm diameter that I drill through all
> the layers as the first step. The films I use to expose also get

those

> holes. My english is unfortunately not good enough to describe how I
> manage to create precisely positioned 3mm diameter holes into the
> films but I "stamp"? them out using a little tool I built by myself.
> To create this tool I used 3mm diameter silver steel and used a

center

> drill to drill a hole into one end. This results in a very sharp

edge.

> Anyways, once the holse are within the layers and the films, all can
> be precisely alligned using 3mm sized pin's. Since I do not have a

CNC

> drill yet (well, I'm in the process of building one myself but since
> I'm currently held busy with other stuff it's laying around for some
> months now) I'm actualy laminating a layout to one of the outer

layers

> at an early stage using a film where the holes of the vias and pads
> are not covered. This laminate get's then only exposed and

developped

> and then serves as a help in hand drilling the holes into the

propper

> places. Btw, this method of using pin's works so nicely that I also
> use it for double sided PCB's to alling the film which before always
> used to be a bit trickey.
>
> An important thing is also the glueing. It's very important to make
> sure that glue is everywhere and that there are no air inclusions
> between the layers. I asure this by glueing both sides in one shot,
> applying the glue to the INNER layer only and by only applying a
> fairly thinn layer of glue (2 components glue that dryes in 5

minutes

> from the hardware store is fine. I.e. 5 min epoxy or similar). The
> reason why I apply the glue to the inner layer is that it's

structured

> by the artwork and by doing so it's obvious that those parts without
> copper get enough glue so as there is no air at those spots later

on.

> After having applied the glue to the inner layer, I position the

outer

> layers again using the two 3mm pins and apply as much pressure as I
> can. I created a little wooden construction for this purpose that
> holds two vices positioned in such a way so as I can apply pressure

to

> an as big area of the PCB as possible. Of yourse, during this

process

> the PCB is covered by two wood pieces so as it does not get

scratched

> or bent by the vices and also to more evenly apply the pressure.
>
> That's mostly it. It sounds a lot more complicated than it actually
> is. In fact the key point is to have a through hole station. The

very

> same principle can be used to create 6 layers or more. The only
> difference is that you have to glue twice. The holes are however
> always only drilled after glueing the most outher layers.
>
> If you also apply a solder stop mask to the outer layers (I do have
> one that can be laminated, exposed an developped - again Bungard is
> your friend) the look and feel of such a PCB is identical to one

made

> by a board house. Since I most often use this only for prototypes I
> don't apply solder stop mask very often but it works quite well.
>
> >I have made a few small double sided boards using photosensitized
> >boards, but haven't attempted PTH's or multilayers.
>
> I figure you are in the same boat as most homebrewers here then.
>
> >I have heard of a product that might be of use in making

multiplayer

> >boards: There are thin sheets of copper on some sort of insulating
> >backing material. The sheets are thin and flexible enough that

they can

> >be run through a laser printer. (Small pieces can be cut out and

taped

> >to a full-size sheet of paper before sending through the

printer.) The

> >laser toner protects the copper, so the copper sheet can then be

etched

> >immediately. I read about this product and how to use it in a

hobbyist

> >electronics magazine around 1995. Some hobbyist supply company

offered

> >to sell small quantities of the material. The cost for ten 8 ½ x

11

> >inch sheets was less than $100 – maybe much less, I don't remember.
>
> I never heard of such a product, but IMHO $100 for this size is way
> too much. For that price I would have my boards made by a board

house.

>
> As stated in my other post, I have a hard time to understand why
> people seem to be so shy of using this aproach. Hey, it's nothing

more

> than 5 tanks with chemicals in them - really no rocket sience to

just

> use it this way.
>
> Markus