[Elecraft] SMT - Was Re: Wayne on KNBx

[Craig Rairdin]

> Like it or not, we are seeing another transition in kit building. Just 
> as some of us witnessed the transition from tubes to transistors, we 
> are now seeing the beginning of the transition from parts with leads 
> to SMT.  I would guess that in ten years or so it will be 
> increasingly difficult to find parts with leads.

There's a fundamental difference between the two watershed moments you
describe. The shift from tubes to transistors brought new capabilities.
These were primarily the result of the need for less power and the dramatic
change in size. Being able to do the same thing in a smaller package that
required less power and dissipated less heat brought about lots of
innovation.

The shift from leaded parts to surface-mount parts is different. It is a
change of form to accommodate automated assembly. There is some change in
size but overall it's the same stuff in a different-looking package. There
are things the old parts can do that the new ones can't. For example I have
resistors in my airplane soldered inline with fuses. It would be impossible
to replace this with a leadless part and impractical to design a circuit
board to hold a resistor and a fuse for the sole purpose of using a
surface-mount part.

One could argue that the shift from tubes to transistors is no different.
Transistors weren't plug-n-play compatible with the tubes they replaced, so
it was probably imagined that tubes would be around for a while. The problem
is that there was no application (other than repairing existing units) where
tubes had an advantage. In the case of leaded vs. leadless parts, there are
clear examples of the benefit of keeping around the old human-handlable
parts.

Surface-mount is the antithesis of kit building by its very nature. The
devices were built for the very purpose of being installed onto circuit
boards by machines, not people. Kit building is driven precisely by the
desire to create something by hand, without the use of machines.

This is (one of the reasons) why I don't get excited when I see kits like
the Sienna (www.getboost.com/dz). It's all preassembled. 

Surface-mount technology has been in practical use for a very long time and
hasn't yet supplanted leaded parts. I can imagine there could come a time
when it won't be financially practical to manufacture every variety of IC in
both SMT and DIP formats, I'm having a harder time imagining leadless
resistors and capacitors replacing their leaded counterparts.

Write back in ten years and we'll see how it turned out. :-)

Craig
NZ0R
K1 #1966
K2 #4941