Double sided PCB, how to?

[Kain]

I guess many people in this forum would like to use sometimes less space for PCB in their projects meaning that they will be trying to achieve higher PCB density. Sometimes it works with very good placement of the components, but I noticed that even if this is the case most components have to be horizontally placed; therefore they will be still taking more space than needed for many projects. I encountered this problem few times already, so I wonder if there is any good way, or nearly perfect way to create double sided PCB since this definately allows for high density PCB. The hardest part to me seems the allignment of both layers since the rest is basically done by the PCB server of the software that people use. There is an article about allignment for 2 layers that I haven't tryed yet:
http://www.robotroom.com/PCB2.html
Please if you have some experience or knowledge on this topic share it :)

[MP]

The method in the article you posted will work fine for larger pads. There is nothing to cause precision and in the taping process, there is usually a small factor of mis-alignment. But for smaller pads, you might want to consider this method:

Pre-drill or punch the mounting pads on your board and punch the holes in your transparency film as well. Use short pieces of wooden dowel of the same size to connect the transparency and board together. If you have been precise in your location of the mounting holes in both copper clad and transparency, your artwork will be perfectly aligned.
metal dowel pins are even better because they will not wear over time like the wooden ones. There are tools available for PC Board manufacturers which have two punches in it set at exact locations to punch the pc board and transparency in the exact same place. You could make such a tool and use it for all of your two-sided projects.

MP