Homebrew PCBs

0.5mm spacing is no problem, even with TT, but you need at least 600dpi on  
the printer side.

As you say the bigger challenge is the no-PTH thing. In your case you  
should be fine, but some of the QFNs and other cases with exposed thermal  
pad for cooling are problematic. Also, the newer chips that use these  
small cases are sometimes really fast and some have very strict  
layout/decoupling requirements, to the extent that it is recommended how  
to run supply traces, where to put vias and capacitors, and the lot. Some  
even use vias as part of filters for the supply. Those recommendations are  
always assuming you have industrial boards and automatic  
placement/soldering. I can't always folow them but so far everyhthing  
still worked.

BGAs are another thing, i see no way to use them if they have "surrounded"  
contacts. But luckily it looks as if they are not that popular anymore  
with ics up to say 50 pins.

ST

On Tue, 31 Jan 2006 16:34:22 +0100, leon_heller  
<leon.heller@...> wrote:

> As an experiment, I'm designing a home-made single-sided PCB for a
>
> Philips LPC2106 ARM device. It has an LQFP48 package (0.5 mm pin
>
> spacing). I've just made a test PCB (no tracks), there were no shorts
>
> visible between the pads so it looks like my technique is viable for
>
> fine-pitch devices.
>
>
> I used the rather expensive JetStar Premium film in my Epson Photo 780
>
> inkjet printer, UV exposure onto Economy Fotoboard PCB material, and
>
> FeCl3 etchant.
>
>
> Although the Philips LPC21xx chips can run at 60 MHz, all the
>
> high-speed stuff is inside the chip, so it should work OK on a simple
>
> single-sided PCB, given adequate decoupling for the 1.8 V and 3.3 V
>
> supplies. They work fine on properly designed double-sided PCBs.
>
>
> Leon
>