In some sw products you can turn this off , creating plated through holes in a home lab is not a easy task.
The easiest way to do so is to create a set of masks with alignment holes, you start out with a blank sheet of FR4, you then drill the holes where you want them including the index holes, them after deburring the holes you coat the board on both sides with a photo pos coating, your mask needs to be reversed meaning that where you want holes and traces you will have the light going trough !
You then basically expose and develop your board, you now have blank copper where the traces and holes are going, now you need to put the board in a primer bath, the primer basically adds conductivity to the holes but its a higher resistance than copper, unfortunatly i cannot remember the chemical used for that, alternativly you can also do that after you drill the holes and before exposure, now you put the PCB in a gold or silver plating bath and apply curent (you electroplate) after a few hours you revove the board and water it, you now see the traces in gold and you can measure continuity in between the two layers, the last step is to strip the photo resists and etch the board in a mild etching solution ( no ferric cloride) , you can also electroplate the holes with copper and then plug them with silicone and remove after etching but thats a pain.
All in all this yields nice plated trough boards but be warned that the chemicals involved are not enviromently friendly and need to be disposed off properly, also plating through hole stuff for gold plating isnt cheap.
--- On Thu, 10/16/08, Harvey White <madyn@...> wrote:
From: Harvey White <madyn@...>
Subject: Re: [Homebrew_PCBs] double sided boards and through plating
To: Homebrew_PCBs@yahoogroups.com
Date: Thursday, October 16, 2008, 6:21 PM
On Thu, 16 Oct 2008 14:39:35 -0700, you wrote:
>Most pcb programs assume holes are through plated which isn't the case
>when I make my own double sided board. Do you guys usually solder
>both the top and bottom of a pin that's through plated?
No. Some items (IC sockets) cannot be treated that way. Some items
are designed to be soldered on one side only (resistor networks).
I use separate VIAS, and do not allow a wire to terminate at a
component pad for any layer other than the bottom.
>
>If anyone is using Eagle, in the Single Sided demo, whenever I
>autoroute it, it knows to generate wire bridges for the top layer.
>
>I use the same CTL file but whenever I generate my own board, it seems
>to assume plated through holes.
>
>I checked the DRC and they seem to be the same.
>
>How do I get Eagle to treat the board like in Single Sided demo and
>not plated through holes? Thanks.
Other than copying the rules over, that's all I know.
Harvey
>Henry
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