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From: "Michael A. Terrell"
Subject: Re: Using QX3 microscope for SMT
Date: Fri, 04 Oct 2002 23:54:52 -0400
Organization: I'm trying!
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References: <email@example.com> <3D9E2EBF.535EE22A@mfi.net> <3D9E50EE.181E992D@webaccess.net>
Chuck Simmons wrote:
> "Michael A. Terrell" wrote:
> > Ivan wrote:
> > >
> > > I was thinking about getting Intel's QX3 toy microscope to do some
> > > fine pitch soldering instead of buying a magnifying lamp or a real
> > > microscope. Has anyone tried this? Any opinions?
> > >
> > > Ivan.
> > The thing has too much magnification, and very poor lighting. (10X,
> > 60X, 200X)
> > I tried the same idea a couple years ago. Now it sits on the shelf
> > next to the computer and all I use it to read part numbers. The frame
> > rate is very slow, so any movement causes jumpy images. Also, since it
> > isn't a stereo scope it has terrible depth of field. Only part of a part
> > is in focus at a time. I have some images I can post if you want to see
> > the image quality.
> The depth of field problem exists with all microscopes. If a small NA is
> used, the illumination is dismal but the depth of field large. A large
> NA will do better for illumination but at the expense of depth of field.
> It gets worse. Standard microscopes all have a 160mm tube length which
> means that the NA of the objective is related to its power. The higher
> the NA, the higher the power of the objective. For example, a 4X
> standard objective has an NA of 0.1 typically. A 40X is has an NA of
> maybe 0.65. A 100X objective may have an NA of 1.25 but an NA greater
> than 1 requires immersion oil.
> In general, you want a moderate NA not high) to get depth of field and
> built in top illumination to get a bright field. Microscopes in this
> class are non-standard but available new for about $200US and up.
> Younger people and myopic people can get by with low powers like 2X or
> 3X for 0.5mm pin pitch. The reason myopia can help is that the myopic
> has a very short working distance with the uncorrected eye. My
> comfortable working distance without glasses is about 3 inches. I need a
> lot of light to get good depth of field with my unaided eye.
> ... The times have been,
> That, when the brains were out,
> the man would die. ... Macbeth
> Chuck Simmons firstname.lastname@example.org
Chuck, I used a stereo inspection microscope on my bench for almost
four years to do rework myself, rather than wait for the usual rework
cycle. I could do it on the fly, sometimes without unhooking the board
or module i was working on, then go right back to testing. Then the
board went to the cleaning room before going to QC.
My uncorrected vision is poor. It was 20/200 and 20/400 when I went
into the service in 1972, and its worse now. I have lost the fine
focus, so even though I can see things close up, I can't make out the
details without the microscope. I have lineless trifocals for normal
work and driving, but they have to come off to do the fine stuff. I'm
trying to get a good stereo microscope with zoom so I can work from
home. Hopefully, I can talk the VA into getting me one when they finally
get my medical benefits straightened out. I have most of the other
tools I need, and I am going to try to set up a board repair service, if
the VA can help me with the constant migraines.
Take care, and God bless!
Michael A. Terrell
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