[time-nuts] Parts Selection

[Bob Paddock]

On Fri, Mar 25, 2011 at 5:29 PM, Bob Camp <lists at rtty.us> wrote:

> I don't see a way to reasonably ship a solder mask with each board. I agree
> it would be neat, but it would cost ...

Solder Stencil actually.  The mask is part of the board.

Low use stencils are $25: http://www.pololu.com/catalog/product/446
for each one.

I'll address some other comments I see in this thread, in this one reply.

On the PCB list the consensus is 0402's are the smallest things that
can be done by hand.
0603 are no problem at all to do by hand.

BGA's are actually easier to do than QFN parts, as long as you  accept
the board is now not repairable and is a throwaway item.

Avoid QFN's if at all possible, especially in battery powered
circuits.  The flux gets trapped raising leakage currents.

It doesn't take "a steady hand" it takes a while timed hand, drop as
pass over not hold and aim.  Think Target Shooting rather than holding
absolutely still.

I expect any Time Nut probably has what it takes to cobble together a
video magnifier in their house already, except for maybe the macro
lenses, for example:
http://www.designer-iii.com/Solder/  made from Wife's video camera, RF
Modulator and old color TV.  Check out the Toy Store for Cyclops
Camera or search for AE10324-ND at http://www.digikey.com .
Not the best but works.  Works well mounted on old desk lamp base,
that has a flexible neck to aim and hold, picked up at the Salvation
Army Thrift Store.

Also consider there maybe disruptions in the supply chain due to the
Japan Earthquake at the fundamental material level, as well has the
chip level.  Many fabs are still closed due to damage or lack of
reliable power.

"The glue that holds the electronic industry together falls apart,
Bismaleimide Triazine (BT) resin shortage."
http://blog.softwaresafety.net/2011/03/glue-that-holds-electronic-industry.html



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