[time-nuts] pcb question

[SAIDJACK at aol.com]

Hi Norm,
 
yeah, that was not one of my prettier boards, just a very quick hack  
(litterally). With a bit of time and prior planning this process can look  much 
better.
 
Some hints:
 
* yes 0603 etc are english sizes, they are the length and width of the  
component in mils (more or less). Sometimes I even use 0402, but that is  
definitely a challenge, the parts get damaged easily.
 
* Use small pieces of Kapton tape to insulate components and pins from the  
ground plane. That's pretty resistant to soldering. Use the same tape to hold  
down the thin wiring after you are done routing.
 
* Use Kapton tape to route 50 Ohm transmission lines. The Kapton tape can  
help you separate wiring from the ground plane to achieve your desired  
impedance.
 
* You definitely want to get a stereo microscope to do this work, even if  
you have perfect vision. It just makes life so much easier, and also prevents  
you to breathe the fumes (to a certain extend it will shield you)
 
* I use wire-wrap wiring (the very thin red wire) that' about 20 years  old. 
You can get this from a transformer winding etc, but please be aware that  
removing the lacker with the solder-iron (tinning the leads) releases fumes that  
can be toxic
 
* I prefer lead solder, it just makes life so much easier, but may be hard  
to get in Europe etc
 
* I use a Metcal iron with sufficiently thick tip for this. If the tip is  
too small the Copper ground plane will just suck all the heat out of it, and the 
 solder won't flow well. I use a 50W Weller station with wide tip for large  
objects such as the TO-200 7805 regulator's thermal tab.
 
* To add connectors, I usually use SMA or SMB type connectors. You can  
solder them down on their side (right angle) at the edge of the board, then  route 
the center pin with the wire-wrap wiring.
 
* You need to create a stress-relief island with the exacto knife somewhere  
at the edge of the board for wiring that goes off the board. Then route the 
thin  wire-wrap wire to these islands. You may even drill holes into the PCB and 
feed  the wires through these for added stress relief. That allows you to 
pull on the  wires without yanking off components from the PCB
 
hope that helps,
bye,
Said 
 
 
 
 
In a message dated 6/7/2008 08:03:50 Pacific Daylight Time,  
normn3ykf at stny.rr.com writes:

Said,
Gotta love the pics. Cute way to solder together a  7805!
One last question. 0603 and 0805 are english not metric sizes,  right?

There's a lot of smt prototyping info on the net. Lots of people  are 
doing it with good success and lots of fun ideas involving dremel  tools 
and x-acto knives.
Thanks for the help.
Norm  n3ykf





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