Saturday, February 13, 2016

Review: microscope for electronics (three Andonstar USB microscopes)

Here: fixing a board (0805 SMT resistors near a µSD socket, 0.6 mm wires).
A microscope is a much needed tool to inspect electronics, or to work at small scales.
(shot on my $160 workhorse, a very good Andonstar ADSM302)
This post shows the microscopes I have been using so far, sorted in historical order. This is also sorted by price, not surprisingly: with time my gear tend to get more expensive...
I am using microscopes all the time to inspect PCBs, read SMT component values, work at small scales, or whenever my (ageing) eyes are tired... And it feels like being in another world when you end up raising your eye back to the reality after a few hours :)

My first, cheap miscroscope

The $50 "Andonstar 500X 8LED HD" USB microscope is definitely a great tool to double check surface mount components among other uses. I bought it from them on Banggood for about $50 (not a low cost low quality USB endoscope, but much better as well).

See below: I had to replace an AMS1117 regulator from a RAMPS board that I blew (I plugged a 2-wire endstop to the wrong pair of 3-pin, which mean I grounded the power supply and got magic smoke...). I could then check how good or bad I did ;)

The zoom range of an Andonstar USB microscope (webcam/endoscope)! Excellent for its price
if you need a cheap one. Notice however how small the gap is between the lens and the object
on the 
last picture: no reworking possible at this zoom level, only worth for inspection.
My main opinion is:
  • impressively large wide zooming range (see the pic below)
  • integrated leds that are very close to the camera sensor (no external device would give enough light in the shot on the right given how close the lens is from the board)
  • the light intensity can be tuned down to zero. Sometimes the object is too reflective and it "flattens" the image. Then, an external lateral light beam is better.
  • a somehow stable support with fast height adjustment (the stick can be raised/lowered quickly from the "main" tower), plus a fine thumb-wheel on top of the camera barrel (mostly zoom).
  • can be used freely without its base to inspect difficult angles or get a quick overview
  • none many for the price
  • make sure to align "north" with "north" by precisely rotating the barrel, else it is hellish. I ended up adding marks but a physical (eg. 3D printed) cursor would be much better
  • the main pole has a bit of free play left, which can be felt when tuning with the thumb wheel at high zoom ratios (the small wheel is very firm). And there is no easy way to hack this
  • the lens is close to the job: there is not much place to work at high zoom ratios, but more importantly, fumes or flux projection will end up projected on the lens. When it happens, it is almost impossible to clean, given how small the lens is (I am left with dirt and residues)
  • the lens is attached by a plastic ring, which slowly melts under long high temperature work!

A better variant (same microscope, improved base)

Update: this slightly more expensive $85 version (A1-200W-B) addresses this with a definitive improvement. It uses the same microscope, but the already good stands looks way better. I would buy this one if I had to buy again (no, see next one). It is not perfect, as the barrel tilts too easily, and there is a slight free play in the focus ring -- but it is already better.
The same USB microscope/endoscope but with an improved stand ($80 here)

Anyhow it is worth the $20 more.

Note: this microscope is featured in a video by Dave on EEVblog (a nice source of information by the way).

ADSM302: my current, hi-quality, not so cheap microscope

I ended up buying yet another microscope from this brand: the "Andonstar ADSM302 Long Object Distance Digital USB Microscope". It includes its own HD screen. I was not sure it was worth, but this microscope is a real killer for inspection and serious rework.

The andonstar AD302 (about $165)

The column is sturdy and adjusting rings are smooth. More importantly, it leaves plenty of room to work between the (large) lens and the job. Interestingly, this is almost a telescope as well when taken out of its support, but I would trade it for a broader view.

There is no "zoom ring" like on expensive gear, height must be adjusted as before according to the zoom you want. It is smooth and very precisely done though.

Highest zoom (1mm tocks). Check the convenient distance left
between the lens and the subject. Also, the outer (non-focusing)
lens can be removed to clean it, nice.
The embedded, flexible, lights are much better than a led ring around the lens, as they can be oriented sideways to improve contrast (see PCB traces, etc). They hold well enough after a few year BTW.

Inspection: here is a "dry" solder joint that needs rework. 
The attached screen is really nice, and convenient to share a view with colleagues on a lab bench (i.e. when in front of your PC). Also, the high frame rate is a major bonus to inspect a board quickly, or to do tricky soldering jobs: it is no webcam anymore, so it does not have the significant lag and blur of the former microscopes.

But I lack it as well! The HDMI video output brings no benefit to me. I would not add a TV to my desk when I have a 30" screen already. I need to swap SD cards to bring screenshots to my PC, which is cumbersome.

1.27mm-spaced BGA balls on an Octavo SIP (shot sideways)
Checking deposited and "reflowed" solder on a 0.5mm pitch footprint.
The pads lacked varnish between them, and any excess of solder paste
often caused shortcuts between the pads, under the chip !
Being able to project light from the side is essential here.
Solder paste before reflow, on a micro-USB plug
(click on the image for the 4Kx3K original image).
You can see the tiny solder balls in the grease !

  • Very stable (totally OK), very smooth and large focus and Z screws
  • All metal, large lens, removable outer protective glass (cleanup becomes possible!)
  • Large, comfortable lens-subject distance, which protects the lens and gives plenty of room to work.
  • Very good image quality and without distortion. Excellent frame rate.
  • The embedded, tilting screen is a good idea once you get used to it, and it ends up working better than looking farther at my screen with the previous microscope.

  • It does not zoom as much as the previous microscope. But it is mostly never a problem and way better picture quality and higher frame rate is a trade-off I am glad to pay! Still, having an endoscope in addition to the scope is a good thing for the tiniest details may be (unsuitable for working at these scales anyway because of the proximity of the lens to the subject).
  • The ADSM302 wants to zoom in! This is more annoying: it is not well suited to the broader views and subjects. I wish I could see more of my boards for quick inspection, and even more in order to take overall pictures and benefit from the hi-quality optics. See below: the maximum field of view is about 2.5 cm only, even after a mounting the barrel in the highest position.
  • And an annoying point: you have to take the micro-SD card out of its springy slot to transfer pictures to your PC. This really bogs me, especially when the card jumps out in the mess !
Attach the barrel to its end to increase the maximum field of view from 2 cm to a "wide" 2.5cm (1").
Uh. This is really not large, I wish I could get a larger view (no add-on lens?)
Now, look at this huge and convenient distance between the lens and the ruler !
Anyhow, it is not perfect but I would buy it again. It is really useful for real work, and the quality outshines all of the sub $100 scopes. Either go cheap with a $30 or buy something like this in my opinion!

A variant : the Andonstar AD407

Barely more expensive: the Andonstar AD407
Note that the Andonstar AD407 above is barely more expensive ($180), but it can be tilted forwards/backwards. It is particularly useful if and only if it stays as stable as the straight one as I regularly have to tilt the PCB I am looking at to get a side view (it can actually be done with basic supports). Now, beware of the straight column that leaves less space on the plate compared to an AD302. For larger PCBs it is probably a no go for me.

Addendum: cheap magnifiers

The first Andonstar above are excellent to inspect and work at really small scale (like 10x10mm surfaces or less). Being able to see with both eyes is relaxing (a screen is already better than a watchman magnifier), but being able to have a sense of depth is sometimes crucial.

For some time I used a large and super cheap magnifier like the one below ($9). It works well enough for basic electronics up to 1206 SMT as both eyes see through it at the same time. It is both faster and more comfortable at this scale than a microscope.

Having a sense of depth is very nice, and more comfortable. It is also easier to switch from the naked view of the board to the view through the lens, compared to a view on a screen while your hands are elsewhere (which does work once accustomed).

Today, I would certainly buy a more expensive ~$25 magnifying desk lamp instead like the one below But I discarded it because it sucks too much storage space and the non-flat base is annoying. Well, it is only $10 buck so it really is the minimum you can buy ;)
Super basic and cheaper ($9) magnifier. Basic but comfortable enough for bigger jobs
like large SMT soldering. B
ut it is crappy an unsuitable for small scale inspection.
Somehow better, a ~25$ desk lamp with a led ring.
It will not get in your way, and can be folded away when not it use.
An excellent thing to have in any case.
For longer work, I am mostly using these comfortable $12 glasses.
They need no constant distance adjustment compared to the previous ones,
but they take longer time to put on than a desk lamp.
The front led is useless, as much as the lowest magnifying lenses.

Addendum: more expensive binoculars I wish I had

The real binocular stuff I will end up buying starts at about $300.

In fact, I did have the chance to test some "good old $2000+ high quality optics" binoculars, as stated by its owner. But frankly I would never put this money into such overpriced / over-hyped occidental stuff. Its footprint wasted half a desk surface, it did not have a deported arm, nor a camera. Most annoying to me was the tiny field of view with a yellowish tint, like something that should go to a museum instead :D

Here is a more reasonable "trinocular", with good reviews:

A trinocular with a much needed offset / deported base.
It is like a binocular, with a third eye that is actually a video camera.
Now, my two drawbacks are:
  • If the camera is just HDMI, it will not help me take snapshots faster and discuss the images with remote colleagues. I do wish it was a USB webcam instead but the documentation is not helpful so far to me.
  • May be I should add some more money. At $400+ there are solid beauties.
  • Make sure it is simul-focal. This means the camera can shoot at the same time as both of your eyes. It would be a pity to stop half way!
I guess I will end up with $400+ on this. 

By the way, you probably will want to go and check Andreas Spiess video review of his ~500€ trinocular microscope. It gets pricey, if you keep on ignoring the super excessive "pro" brands that have no limits to the money they will ask for!

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