Homebrew PCBs

The big boys use some kind of through-hole plating... solder should work
-----Original Message-----
Date: Tuesday, December 15, 2009 11:26 pm
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] 4 Layer boards
From: "Piers Goodhew" <piers@...>

Not that I have the remotest plan to make a 4-layer board, but with the
epoxy sandwich method, how do you get any electrical connection between
either side of the fibre glass cloth?

PG

On Wed, Dec 16, 2009 at 3:55 PM, Adam Seychell <a_seychell@...>wrote:

>
>
> Trevor White wrote:
> >
> >
> > Hi all.
> >
> > I have been looking into making 4 layer boards. I have most stages
> > sorted but the big stumbling block is the bonding of the layers
> > together. It seems a special press is required that has enough pressure,
> > exhausts the gases away and generates the correct temperatures. I am
> > surprised its so difficult. I have been told second hand presses cost
> > \ufffd4000 to \ufffd5000. This is totally out of budget for me. Has anyone any
> > experience/thoughts /comments on bonding boards together?
> >
> > Thanks
> >
> > Trev
>
> Hi, I've done a number of 4 layers, its very laborious (about 5 hours
> was my record time to make a 4 layer from printing the artwork to the
> final solder mask bake)
> As for lamination, you can use room temperature curing liquid epoxy
> and a layer of fibre glass cloth for separation of inner layers. My
> method cheats, and uses two DS 0.8mm boards bonded together, so inner
> layers are about 0.2mm apart.
>
> 4 layer steps (over simplified)
> ------------------
> * cut two pieces of 0.8mm double sided board
> * protect outer layers from etchant with self adhesive book covering.
> * drill 4 or more registration holes
> * print and etch inner layers (clean, photoresist, expose, develop & etch)
> * place one board on aluminium plate
> * place sheet of class cloth,
> * pour epoxy
> * place 2nd PCB, align with pins on holes
> * place 2nd aluminium plate
> * place some bricks
> * place on top of electric hot plate and heat PCB to 90C to 110C, 30
> minutes.
> * cool, trim sides, remove self adhesive film.
> * process like an ordinary plated through PCB.
>
> To improve copper/epoxy bond you can make it black oxide by wiping it
> with strong bleach solution with 10% NaOH for a few seconds. this
> improves bond a lot.
>
>  
>


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