Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, Gavin Dingley <dingley76@...> wrote:
>
> Hi Lanny,
> I was just wondered what frequency you will be operating the
microwave circuit, and what board you are using. As I understand it
you can use FR4 up to 2GHz, beyond this you need special board which
is made of a low-loss dielectric material. Also if you are using
standard FR4, is there not a problem due to tolerances/variations
associated with the board thickness over an area, as this will change
the characteristic impedance of micro-strip lines - along the line (if
you can see what I mean).
> 
> Cheers,
> 
> Gavin
> 

FR4 can be used up to 4GHz if you reduce the size & the thickness of
the PCB. In addition to those Er's effect, the thickness of the PCB
affects the trace width and the size of the PCB affects the trace
length hence phase delay, loss etc. Above that 4 GHz, I plan to use
Rogers, Taconic materials. I try to mill the PCB before but my milling
machine doesn't have precision Z axis so I can't mill the thin PCB and
also it creates variable depth along the trace when removing copper
around the trace, causing me a lot of headaches.

I'm making test board to find out the most economical way to produce a
small size PCB for our small quantity purpose. I used to send out
simple board 1"x1" using Roger 4350 material and it costs $1000 to do
just that. I'm sure I can beat that $1000 cost per job.