[sdiy] components, smd and pcb

[jhaible]

Refering to the recent thread about obsolence of DIP components,
I thought I'd share a design tip from one of my collegues.

The background is that I start to make pcb layouts again after
many years of veroboard-only. So he told me if you want
to make your boards as unexpensive as possible, then use
a mix of SMD components and ordinary components.
ICs should be SMD, resistors should be ordinary.
The PCB can be single sided. SMD components go on solder
side. Normally you *must* make double sided pcbs (if not
multilayer) when you use SMD, but with a little patience you
can replace the 2nd copper side with resistors.
I tried this on my PS-3100 clone project, and so far (still in
the midst of the first card, the oscillator board) it looks very
good. It's *really* the best of both worlds: The resistors
act as a replacement for the 2nd copper side (compared
to a SMD-only design), and (compared to a traditional
design) now you can connect resistors straight over IC
packages (because these are on the other side now).

Pros:
* I can use SMD parts (availability will be better on the long run)
* One copper layer is enough
* Resistors ar standard (can easily read the value)
* Less holes to drill than with standard components

Cons:
* As the SMD parts are on "the other side" now, I have
   tothink in mirror image when I route the traces.

JH.