Homebrew PCBs

Markus,
I would very much be interested in setting up a lab to try out your method.
Please send the information when you can. I have always sent boards out for
through hole plating and, although I wanted to setup to do the plating
in-house, I could never extract the information from anyone on how to do so.
I am sure there are many on this list who would also like to give it a go.
-Mike

----- Original Message -----
From: "Markus Zingg" <m.zingg@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Sunday, May 11, 2003 8:37 AM
Subject: Re: [Homebrew_PCBs] Metalized holes


> Ok, let me get a bit more specific.
>
> The process obviousely depends on wether a two layer or four layer PCB
> is to be made. I use 18um copper plated base material. In case of a
> two layer board this is of 1.5 mm thikness, in case of a four layer
> one 0.5 mm only. First step is to drill all holes through all layers.
> In case of four layers, I screw the layers together using two
> diagonaly positioned screws that I place outside of the final PCB
> area. Then comes the plaiting trhough process of the inner layer
> (obviousely there is only one inner layer with two sided PCB's). After
> this I laminate a photoresist film onto the two sides of the PCB (or
> inner layer respectively). The result is then exposed and etched, then
> the remaining part of the photoresist is removed by exposing the whole
> print once more and develop (which will completely remove the
> remaining parts of the photoresist). If this is going to be a four
> layer PCB, the outer layers are glued onto the two sides of the inner
> layer using a thin film of 5 minute epoxy. The previousely two screw
> holes are now used to propperly align the layers. After this I drill
> all holes once more to remove glue. After this the whole PCB is once
> more through plated, the outer surfaces are laminated with photoresist
> film, exposed, developped, etched and reexposed developped to remove
> the remaining parts of photoresist.
>
> Now to the time it takes:
>
> exposure = 1.5 minutes per run
> develop = 1 minute
> laminateing = ~1.5 minutes per side
> plate trhough run = 30 minutes up to ~1 hour depending on size of pcb
> etching = ~4 minutes.
> drill the holes = ( I do it manually. The photofilm is manually
> alligned so as it matches the alredy present holes) - depending on the
> board but rarely more than 30 minutes.
> Glueing = ~15 minutes
>
> The times needed of course vary depending on the size and complexity
> of the PCB and of course wether its a two layer or four layer one.
> Bigger PCB's may take longer than 3 hours, but I think that 4 hours
> should be sufficient in mostly all cases. I must add though that I do
> not apply a solder stop mask or anything else because the PCB's I
> create are exclusively used for prototypes.
>
> The chemicals I use are partially concentrates and partially ready
> made mixtures which can be bought from Bungard. The photoresist is
> also from Bungard. I will list them in detail later, but they do only
> have "brand kind" of names which don't tell much about what they
> consist of like C400 and names like this.
>
> The method used was shown to me by a friend I got to know through an
> electronic online forum in the internet (in case you read this - thank
> you John). I visited him so as he could show everything to me and he
> was kind enough to explain everything to me in detail. I personally
> asisted a plating through process and the result was simply stunning.
> >From what I understood the speed of the plating through process and
> the quality of the result extremly depends on the chemicals used. He
> had much inferior results before he started to use Bungard chemicals.
> Let me state that neither he nor I are in any ways related to Bungard.
>
> As mentioned, I will post more information including pictures as soon
> as I'm ready.
>
> Markus
>
> >Markus Zingg wrote:
> >
> >[deleted]
> >>The main advantage
> >> however is independancy and the possibility to have a four layer PCB
> >> completed within say 2 - 3 hours....
> >
> >Multilayer in 2 - 3 hours !  No offense, but that statement
> >made me laugh. Even if you had a fully automated machines
> >that did everything from drill to the final dry, it will
> >take much longer than 3 hours.
> >With your experience of the pattern plated through hole, you
> >must of learned to appreciate the complex nature of the
> >process. As you said earlier its not easy, so unless the
> >hobbyist wants convert to PCB making as their primary
> >interest then plated through holes will be best left to
> >professionals or semi-professionals.
> >
> >I appreciate your enthusiasm in attempting to make plated
> >through hole boards at home. I've always had a interest in
> >chemistry and find the inner workings of the PCB process
> >quite fascinating. I'm interested in the basic method you
> >are using or plan to use. Is it the pattern plating process
> >or the "tent and etch" or the "etch back" process ?
> >
> >In the "etch back" process you take a thin copper clad board
> >18 um or less (1/2 oz/ft^2), apply photoresist, expose,
> >develop, and copper plate the tracks so an additional 35um+
> >is added. Remove the photoresists and etch the whole board
> >until the original 18 um copper cladding is completely
> >etched  and so the thicker tracks are not etched. Obviously
> >this requires an etching apparatus capable of uniform etch,
> >something much better than simple bubble tank.
> >
> >Adam
> >
> >
> >
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>
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