[time-nuts] surface mount (was PICTIC II Parts from Mouser)

Joseph M Gwinn gwinn at raytheon.com
Tue Jul 20 16:48:28 EDT 2010


It's amazing what one can do by hand. 

In the 1970s I worked in an electrophysiology lab where we put glass 
microelectrodes into rat neurons.  The microelectrodes were made in the 
lab by heating 1 mm diameter glass tubing to an orange heat and pulling 
abruptly.  (This was done in a simple machine.)  The tube necked down to a 
very sharp point.  Too sharp - needed more tip area to allow for the 3 
molar potassium chloride solution within to make adequate electrical 
contact with whatever was being probed.  The tip was far smaller than a 
wavelength of light.  The tip image degenerates into an interference 
pattern when looked at with an optical microscope.

Solution?  Put the tube on the stage of a 2000x microscope with the tip in 
view.   Take an ordinary glass rod in one hand and manually bring the tip 
into view through the microscope.  Gently tap the tip with the rod, 
breaking the tip back until an adequate opening is achieved.  How is the 
"gently tap" achieved?  One merely thinks of moving the rod.  There is 
enough leakage from intent to action that the rod will move enough to do 
the job, this being a few wavelengths of light.  All this is done 
freehand, although the wrist must be on a rest of some kind.

It turns out that almost everybody can do this, and I was able to do it on 
the first try.  To my considerable surprise.

Joe




From:
David Martindale <dave.martindale at gmail.com>
To:
Discussion of precise time and frequency measurement <time-nuts at febo.com>
Date:
07/20/2010 02:16 PM
Subject:
Re: [time-nuts] surface mount (was PICTIC II Parts from Mouser)
Sent by:
time-nuts-bounces at febo.com



You'll probably also find that your fine motor control improves a bunch 
when
you can actually *see* what you are doing in 3D.  I got a stereo 
microscope
a year or two ago, and I'm amazed at how finely I can control the tip of a
pair of tweezers or a knife point or soldering iron under the microscope.
It works much better than trying to do the same thing with a one-eyed
magnifier like a loupe, partly because a microscope gives you more working
distance, but mostly because of the full 3D view of what you're doing.

My first stereo microscope was a surplus AO 40 that cost $100, so being 
able
to see what you're doing doesn't have to be expensive.

     Dave

On Tue, Jul 20, 2010 at 10:51 AM, Chuck Harris <cfharris at erols.com> wrote:

> Stanley,
>
> Your brain will do an excellent job of translating your finger
> motion to the micro motions necessary to move surface mount parts
> around with tweezers.  Barring disease, the usual solution to finger
> jitter is to keep tweezers pressure light, and lay off the coffee.
>
> Even if you do jitter a bit, there are many tricks you can use to
> keep it to a minimum.  I use the little finger on my tweezers hand
> as a balance point for my hand.  Just the act of having it touch the
> stage, or board removes all of the jitter.
>
>
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