What's the highest magnification you use on a microscope and why?

[badrequest400]

Someone on a different forum was asking for soldering microscope advice. I only ever use my 10x lenses since 20x is unnecessary to me and has too limited a field of view. The person on the other forum ignored this advice and went for a model offering up to ~700x magnification! It made me wonder what that's even useful for. What is the highest magnification people here use [for electronics] and specifically what for?

[jpanhalt]

The resolving power of a light microscope is limited by the wavelength of light used and the optics.  The highest practical resolution of a light microscope used in pathology is about 100X with oil immersion objective, which has a much higher refractive index than air, followed by a 10X eyepiece to give about 1000X magnification.  Many pathologists go no higher than 63X (X10). PS: The shortest wavelength of visible light is about 400 nm = 0.4 micron.  Some bacteria push that limit.  A red blood cell is about 7 micron in diameter.

The magnification can be virtually any claimed number, but that doesn't mean better resolution.  It's like magnifying a bit-mapped image until you are looking at a single pixel.  In my experience, cheap video microscopes (eBay and Amazon) are like pinhole cameras.  They give a lot of distortion and way too much magnification without raising the camera to a height much higher the the tiny stand allows.

I agree with your lower estimate.  With my Nikon dissecting microscope (I prefer light to video), I have 10X eyepieces and usually use 0.9X to 1X for the objective, rarely going above 2X.  The maximum is about 4X.

[thm_w]

700x is usually for biology as mentioned above. I don't even know how you'd use that for soldering.
The most for soldering I'd go to is around 30x for really close inspection (zoom range 3-30x). As you say 10x eyepiece is the one to use.

But if we are talking bare dies, Shariar has some good demos of what is possible. I think he was in the 100x range?

[magic]

Is it a purely optical microscope (you look into a tube with glass in it) or some digital gadget with a screen or USB/HDMI output?

The latter may boast crazy magnification numbers which are not necessarily comparable with traditional magnification specs of optical microscopes. OTOH a conventional microscope with 700x mag is too much for wirebonding, let alone soldering And you likely won't find a stereoscopic microscopes with such magnification, and working distance will be for all practical purposes zero.

BTW, the magnification of optical microscopes (and magnifying glasses) is defined as approximately how larger the object appears to be compared to viewing it with naked eye from 25cm distance.

[joeqsmith]

About 2.5x to 50x depending what I am working on.  There have been times I would have liked to go up higher but not 700x.   

[twospoons]

I work in the range 10x to 40x, depending on what i'm doing.  I use 20x eyepieces and a 0.5x Barlow over the objective for a longer working distance, makes getting the iron in there much easier.

[Zero999]

Note this isn't a matter of the magnification factor, but the smallest detail, which is dependant on the wavelength. Illumination with a violet 400nm LED will be able to achieve much greater resolution, than an incandescent lamp or white LED, which has much longer wavelengths.

[watchmaker]

I have used scopes for at least 20 years in watchmaking.  I do general bench work at about 15x with the scope set at 30X and a .5x barlow (15x widefield eyepieces.  For inspection, I have a SZ7 and we use it to 70x.  At the lathe, I may go to 40X.

It is a function of field of view, magnification/resolution image brightness, working distance, and head position (the lower the barlow, the higher the scope needs to be).  Generally anything that sez it yields over 100x for under a couple grand is a toy.

Change mag range with barlow, not eyepieces  For my money, the BL15X ultrawides are the best value for money. Large exit pupil, field of view and bright. Many are used by astronomers.

I am talking optical scopes by the way.

[Smokey]

I've always found the best stereo inspection microscopes to be the 0.7 to 5x zoom with 10x eyepieces.  That covers like 90% of the soldering and rework jobs.  The other 10% is picked up with a 0.5 barlow.

[Alex Nikitin]

Dewey knows what magnification I likely to use for soldering and inspection  . I do use however up to x400 (x40 x10) magnification on my metallurgical microscope for checking the gap condition on magnetic heads for tape recorders.

Cheers

Alex

[CatalinaWOW]

For soldering and similar fabrication I completely agree that modest magnification is sufficient.  Failure diagnosis also can require finding tiny cracks or voids and really has no limit on magnification which is useful, including use of electron microscopes.  And once upon a time, when manual wire bonding still happened magnifications in between those ranges where useful.

[jfiresto]

Yeah, you would need a compound microscope with oil immersion and a minuscule working distance to get 700X – which makes me wonder if the OP's colleague got a video microscope with 700X magnification w.r.t. a large screen.

No one has mentioned the challenge of vibration with a stereo microscope at much lower magnifications upwards of, say, 20X. Mine can only reach 62X and that took a massive stand to make tolerable.

[magic]

You don't need immersion. Rule of thumb is 1000×NA so you only need 0.7NA. Plenty of dry objectives can do that.

Working distance is only a matter of money, here's 5mm if you want
Horizontal field of view 0.18mm.

[jfiresto]

Well, you have convinced me that I know nothing about modern compound micro$copes, for which I thank you and I mean that sincerely. I would love to see a drawing of the 50X Mitutoyo's optical train.

[Phil1977]

As others already mentioned, the dream magnification ratios of digital microscopes are usually pure fantasy. Fantasy of the kind if you would connect the video output to a video beamer and shine the image onto the neighbour building then you get this and that magnification...

What I usually look for is
- the size and quality of the imager unit, take something with at least 1/2.3" chip and a low latency HDMI output. 4K is nice to have for digital magnification and taking pics or movies, but 1080p is absolutely sufficient for hands-on-stuff.
- a lens with a optical magnification range from around 0.5 to 5. Cheap lenses do this by changing the focal distance, better ones have a "zoom" allowing magnification without changing the focus.
- Every old 21"- or 24"-computer screen is better than small displays sold with cheap microscopes. If you want to do yourself a favour, buy a new screen for PC work and use the old one at the microscope.

If you check these points I assume you will get a well usable solder microscope. Forget completely about "non-optical" magnification factors.

Or, if you want to spend more money, get a purely optical stereo microscope from a "solid" brand. The price is much higher, but good and crisp stereo magnification with a factor of 5x-20x is a really stunning dive into the 3-dimensional object under observation. Probably not necessary for solder stuff, but anyhow, it´s very fascinating. And long time working with a digital screen is much more convenient than looking through an eyepiece, so a really well equiped lab may have both systems...

Purely optical microscopes with magnifications of 100 or more again an own world, but practically only usable for absolutely flat objects like cross-sections or biological stuff. Even the roughness of a non-soldered PCB board is sometimes to much height difference to be focusable in such a microscope.

[tszaboo]

I only ever go to 45x magnification, my work scope has a 10x fixed lens and a 0.7x-4.5x adjustable lens in series.
You might want to have higher magnification to look at cracked capacitors of 0402 or 0201, not as a daily driver, definitely not for soldering or solder inspection.

[magic]

- the size and quality of the imager unit, take something with at least 1/2.3" chip and a low latency HDMI output. 4K is nice to have for digital magnification and taking pics or movies, but 1080p is absolutely sufficient for hands-on-stuff.
- a lens with a optical magnification range from around 0.5 to 5. Cheap lenses do this by changing the focal distance, better ones have a "zoom" allowing magnification without changing the focus.

Yep, that's the specs to look at. If you know these things, you know what to expect: a 1/2.3" sensor is a few mm across, and with 0.5x~5x magnification you get full field of view from a little over 1mm to a little over 10mm across.

Beware that Chinese camera specs can be fake too. I have a no-name AliExpress camera with advertised 1/2.5" sensor, but its actual coverage is 1/3" It's not a really huge difference, though.

[Phil1977]

Beware that Chinese camera specs can be fake too. I have a no-name AliExpress camera with advertised 1/2.5" sensor, but its actual coverage is 1/3" It's not a really huge difference, though.

AllExpress is the globalized version of a chinese street market: You find anything, you may find something cheap, you may get cheated. The only difference: Unfortunately AliExpress does not sell fresh fried food.

[Svgeesus]

My trinocular microscope has 3.5X-22.5X zoom range (10x eyepieces, 0.7 to 4.5x zoom objective, 0.5X Barlow lens). Working distance is great (165mm) and this works well for soldering and inspection.

https://amscope.com/products/c-sm-4tp-frl?variant=41421129056431

[Phil1977]

That Amscope seems quite attractive and absolutely not overpriced.

Do you have any practical comparison to e.g https://www.leica-microsystems.com/products/light-microscopes/stereo-microscopes/p/ivesta-3/?country=DE ?

You get very easily spoiled by the optical quality of the Leica. But is it worth around 5 Amscopes?

[jfiresto]

I have not heard from his lately, but Lukego definitely thought its predecessor, the Leica S9, was worth it. You can read about his researching alternatives, in this thread, and his happy experiences after he getting the S9.

[rfindley]

I use an Amscope similar to @Svgeesus, but I went with the 3.5x-90x, which is the same scope plus an additional 2x Barlow lens that I use mostly for non-soldering purposes.  For soldering, I typically have the 0.5x Barlow lens installed, so I'm working in the 3.5x to 22.5x range.  At 22.5x, a 5mm spot fills your field of vision, so you would only use that for the finest pitch components.  At 90x, you can fit about 2 pins of a 0.5mm-pitch chip in your field of vision, so it's maybe helpful for inspection in relatively rare cases.

I'm no microscope connoisseur, but the Amscope feels like it has decent optics.  No spectral distortion at all, and the PCB retains its planar appearance across the field of vision (no fish-eye).  I can use it all day without eye fatigue.  And it has all of the adjustments that I need.  Maybe this is out of ignorance, but there's no way I'd spend 2x or more on something higher-end since I have no complaints about this one.

[Phil1977]

  Maybe this is out of ignorance, but there's no way I'd spend 2x or more on something higher-end since I have no complaints about this one.

No, that does not sound like ignorance at all, for me it sounds like perfect reasonability...

Thanks for the feedback, if I ever see an Amscope on a workplace or tradefair I´ll check it out. If eyes get worse with age I may even get a personal one as a kind of anti-aging-measure for the eyes 🙃

[jfiresto]

I use an Amscope similar to @Svgeesus, but I went with the 3.5x-90x, which is the same scope plus an additional 2x Barlow lens that I use mostly for non-soldering purposes....

I'm no microscope connoisseur, but the Amscope feels like it has decent optics.... Maybe this is out of ignorance, but there's no way I'd spend 2x or more on something higher-end since I have no complaints about this one.

It all depends what you will do with the microscope. You can use a routine Greenough microscope, like a range that Amscope sells, for a lot of good things, but for some applications, a higher end model can be anywhere from a blessing to a necessity. A Common Main Objective microscope with a plan objective, for example, is well nigh a requirement for taking accurate measurements, especially at higher magnifications away from the center, where a Greenough model progressively loses focus. (You can address that and the perspective distortion, by tilting the specimen – what my father did with his SMZ-2T – but that can get old if you have to do it much.)

The important thing is a microscope that makes you happy. A good microscope is a godsend as your eyes get older, and will serve you well for years if not decades.

[coppercone2]

what microscope can do like 100x without a white cloud starting to show up in the picture? its useful for various things like PCB sides, connectors, etc. but a electronics one needs a huge base to be useful at that range (rail system)