[time-nuts] PCB design questions thread II

Bob Paddock bob.paddock at gmail.com
Mon Jun 2 20:34:43 EDT 2008

On Monday 02 June 2008 02:31:18 pm Patrick wrote:

> I have wanted to fabricate my own PCBs for several years now but I have
> never made an attempt. I am set up here to do silk screening and I have
> ovens and a hot-air soldering iron. Has anyone else tried to fabricate
> their own boards or is the price of farming the work out just so low now?

I've played with doing them at work.  Found it better to just farm them out
to the prototype house.  It is tough to get any real consistency from week to 

> If anyone has farmed out work, could you please feedback as to the entry
> level costs and if possible, some suggested companies?

Cheapest place I've come across for easy boards with 10mil or large lines
is this one, but I've not used them yet (probably next month I will):


> > 1. Surface mount or through hole?  I don't have a re-flow oven (or even a
> > hot air soldering system), so my inclination is to use through hole

SMT is actually easier if you have a good magnifying system.  I use 
macro-lenses on the wife's Cam-Corder:

http://www.designer-iii.com/Solder/  Looks better than the picture of the 
screen shows in reality.

http://www.micromark.com/ has the type of tools that you need, like insulated 
and cross-tweezers (squeeze them to open them, the reverse of normal 
tweezers) etc.

Pick up a small convection oven at Wal-Mart or such place.

If your making several get a Stencil:


>   Will using through hole cause me grief?

In the long term, yes.  A lot of older TH parts have not been updated to ROHS 
(Lead Free) and they never will be, they will be discontinued at some point.  
Virtually all new parts are SMT.

> > 2. How many layers?   In an ideal world with money no object, if I
> > understand the current art correctly, I think I'd probably aim for a five
> > layer

I assume that is a typo?  You can not have an odd number of layers.
In this current 3D reality each layer has two sides.  :-)

> > board with Vcc, Digital Ground and Power Ground being separate 
> > internal planes, and trace routing on the top and bottom of the board
> > with as few vias between top and bottom as possible.  Does that sound
> > right?

Separate ground planes, or split ground planes are a bad idea in this context.  
Always think about where the return current is going to flow.
Read the Analog Devices seminar notes on the subject.

is the link to the books but you can find the chapters on line.

Read 7a & 7b if nothing else:


 http://www.softwaresafety.net/ http://www.designer-iii.com/

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