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AmScope Stereo Microscope a boon for working with surface-mount devices How you do cope with assembling PCBs with surface-mount devices? You can always inspect the solder joints with a magnifying glass after they have been made. Or perhaps you use a large illuminated magnifying glass while you solder. But the “deluxe” way is to use a stereo microscope. T hese days it is more or less impossible to avoid surface-mount technology if you are involved in building or repairing electronics. Almost all the really interesting devices seem to be available only in finepitch or leadless packages. Rather than fight this trend, I have been working quite happily with SMT technology 22  Silicon Chip for many years and have developed an armoury of tools and techniques to cope with most of the packages those devious chip designers can dream up. One of these tools was a very cheap, hand-held USB microscope. Review by Andrew Levido This was handy for inspecting joints or looking for solder bridges but it was not practical to use while soldering since the working distance (the distance between the work piece and the lens) was only around 20mm and there was a considerable lag in the video. Thus, I tended to do most of my SMT work without magnification. siliconchip.com.au Viewing your work through the eyepieces then moving your soldering tool to the same place takes a bit of getting used to – but after a couple of hours, it does become second nature. The microscope is perfect for surface-mount devices. Recently, after spending an afternoon hunched over the bench with my face only centimetres from a PCB, the crick in my neck told me something had to be done. I hit the ’net to see what the options were. I steered away from video microscopes because I was wary of the video lag effect. I therefore narrowed my search down to optical stereo microscopes with a wide field of view and a good working distance. Incidentally, I should point out the difference between a compound microscope (the type you might have used in science at school) and a stereo microscope. A compound microscope may have one or two eyepieces but has a single objective lens close to the object being examined. Often there are several objective lenses mounted on a turret but only one is in the optical path any time. Compound microscopes offer high magnifications (up to 1600x) but the image is two-dimensional. A stereo microscope, on the other hand, has two completely separate siliconchip.com.au optical paths offering slightly different views, resulting in a three dimensional image. Magnification is usually lower than for compound microscopes (less than 100x). What’s available? There is a wide variety of options out there, ranging from the top-ofthe-line Mantis Elite at nearly $3,000 to low cost “toy” microscopes under $100. After much searching I settled for a microscope from the US-based online retailer AmScope (www.amscope. com). They offer a truly bewildering array of microscope types and configurations. Ultimately I chose their SM4TX-144A microscope package. See www.amscope.com/sm-4tx-144a.html This is a trinocular microscope: as well as two eyepieces, it has a third optical port suitable for mounting a camera. It has a magnification ranging from 3.5x to 45x, continuously variable via a zoom knob, a wide field of view at 65mm and a working distance of 200mm. It comes with a boom stand that allows the microscope to be moved in and out of the workspace and a LED ring light to illuminate the work surface. At about $US550 this seemed to be a very reasonable package. I went onto the website and placed my order, only to discover the shipping would be around $US360, bringing the total to almost $1000 Aussie dollars – right at the top end of what I was prepared to spend. Given that the package weighs over 30kg, there were no cheaper shipping options. I swallowed hard, entered my credit card details, hit the go button and sat back to wait. But a few days later I got an email from AmScope explaining that they did not accept foreign credit cards, asking me to pay via their PayPal account. No problem here but it seems an inefficient way to operate. They also stated: “all of our items come standard 110V, if you need 220V please let us know as there is a $5 fee for the upgrade”. Again, no big issue – but the website could be a bit more friendly to overseas purchasers. A few weeks later two parcels duly arrived, one containing the microscope head, the eye pieces, Barlow lens, eye guards, a plastic dust cover, the ring light and its control box. The second box (which I could barely lift) contained the parts for the boom stand. This is truly a massive (30kg) piece of hardware. Caveat emptor! By the way, there is an enormous price range for the AmScope SM-4TX144A on the internet – and we’re not sure why. Some sources offer this microscope for about the same net price as AmScope or even less: after ordering (of The eyepieces have a rubber shroud which can be extended, as shown here, or collapsed for those of us who are visually aided (ie, wear glasses!). July 2014  23 The ring light control box is also a bit disappointing and has a bit of a home-made feel. It works fine but the buttons feel cheap and the ring light connector is a USB mini B type. I don’t like the idea of using these connectors for non-USB purposes in commercial gear. One day some “valued customer” will plug a USB device into the control box or the ring light into a USB device with ugly consequences. The control box does have a CE mark label (although no US or Australian approval marks), so I assume it is reasonably well designed and made. Using It Included in the package is this ring LED worklight, absolutely essential for illuminating the subject, along with its power supply/controller. We have just a few reservations about the quality – but it works! course!) we found one site selling for $US520 with $US53 shipping to Australia (~$AU600). But there are others selling for much more (eg, >$AU1350 inc shipping) with no apparent “extras”. You can order this scope through amazon.com (“sold and shipped by AmScope”) which suggests a $US499.98 ($AU537) including postage. But when you go through the cart process to order one, you’re likely to find that they either “will not supply to your geographic area” or the “free postage” suddenly becomes not quiteso-free. That same site adds a “per shipment” charge of $US29.00 and a “per weight” charge of $US8.99 per pound – and the AmScope website states a shipping weight of 68 pounds. So that free postage could equate to $US611 or more than $AU650! So if you order on line, shop around, check the fine print and watch for any emails from the supplier. In the end, I was happy that I ordered it from AmScope direct (and the security that provides) even if I did pay a premium. Assembly . . . instructions? The assembly instructions are pretty rudimentary and I found it easier to use a photograph from the website rather than the provided booklet to assemble the stand. Otherwise, assembling the microscope head is fairly foolproof with 24  Silicon Chip the two eyepieces dropping in place and the Barlow lens screwing onto the objective lens at the bottom. The ring light is attached by three radial thumbscrews to a supplied collar that is screwed on to the Barlow lens. Incidentally, the Barlow lens is used to increase the working distance at the expense of magnification. In the case of my microscope, the Barlow lens doubles the working distance and halves the magnification. If it is removed, the maximum magnification increase to 90x but the working distance is only 100mm. The ring light is worthy of comment as it contains no less than 144 LEDs arranged in concentric rings. The controller allows the LEDs to be dimmed and also for separate control of each quadrant. This is handy if you want to light from one side only (for example to read those pesky black-on-black IC markings). The ring light and its control box are shown above. Note the (mis)use of a USB connector and the US mains cable. The photo opposite shows two of the four segments illuminated. One surprise was that my five-dollar “220V upgrade” consisted of an unapproved Chinese power adaptor so I could plug the supplied US-style 2-pin mains plug into an Aussie socket. Pretty dumb really, since the mains cable connects to the light control box via a shaver-style cord. It would have been better (and safer) if they had simply packed an Australian cable. Apart from a bit of playing about, the first intensive use of the microscope was to construct the prototypes for the Audio Recorder published in the May and June 2014 issues of SILICON CHIP. This required five or six hours of intensive SMT work including soldering 0.5mm pitch TQFP microcontrollers and a 3mm x 3mm leadless pack, also with 0.5mm pitch. Although it took a few minutes to get used to the idea of looking more or less straight ahead, while my hands were working down at bench level, I quickly became a complete convert to working with a microscope. For most work, I kept the magnification quite modest, with the greatest benefit being improved posture and zero eyestrain. I think the consistency of my solder joints was also improved. The microscope really came into its own when checking for solder bridges between pins or to check that a pin had properly reflowed. By increasing the magnification, those tiny 0.25mm gaps between pins became yawning chasms and any soldering faults were rendered blindingly obvious. I was even able to tilt the microscope 45º to look at the edges of the leadless packages to see if the solder had reflowed properly. As mentioned above, the ring light has plenty of modes but in practice I used it with all segments on and at close to full brightness almost all the time. The ring light is essential since without it the microscope image is almost unusable, despite my having a very bright lab. I found the working distance to be completely adequate and never felt constrained by the presence of the microscope while using the soldering siliconchip.com.au Helping to put you in Control N480D PID Controller Low-cost PID controller that accepts T/C & RTD input, 3 relay outputs & 1 pulse output for driving SSRs. Auto-tuning PID function, dual display & ramps soak function. 240 VAC powered. SKU: CET-052 Price:$79+GST Wireless Freezer Thermometer FT0076 is an 8 channel wireless thermometer suitable for monitoring temperature of freezers. It has temp accuracy of ± 1 °C. Comes with 2 remotes & up to 8 sensors can be added, plus alarm configuration. 100 m transmission range. Batteries not included. SKU: UTS-005 Price:$85+GST Here’s that same LED ringlight in action. It simply clips to the bottom of the Barlow lens (also supplied) and can be varied in brightness as well as in the segments illuminated. We tend to use it with all four on and flat out! iron or any of my usual tools. The field of view was also fine but there was an unusual side effect of viewing the work through what is effectively a 65mm diameter hole. I would tend not to lift my eyes from the eyepieces to grab the soldering iron, for example, and then fail to be able to bring it to the “hole”. The answer of course, is to only look through the microscope once your tools are nearly in position, but this took a little practice. One other pleasing feature compared to the old USB microscope I used to use was the true three-dimensional nature of the image. You can really see the way the solder fillet runs up the end of a SMT capacitor, for example. The depth of field is adequate at about 5 or 6mm for typical levels of magnification. Once you start using the microscope, you really begin to appreciate that heavy stand that cost so much to ship. The horizontal movement is very smooth and the solid construction and heavy counterweights mean that the microscope remains rock solid even at the fullest extension. This means you can push the microscope right out of the way when you don’t need it, but pull it into place in a couple of seconds. I wear spectacles all the time and I was a little concerned how these would work with the eyepieces since I have had trouble with microscopes and telescopes before. I need not siliconchip.com.au have worried, since the rubber eye guards (in their folded-down position) worked perfectly with my glasses. These eye guards also fold up for those lucky enough to have perfect vision. Conclusion On balance, the AmScope SM-4TX144A is a great tool for anyone regularly using surface mount components – and that’s most of us these days. It is easy to use and will in all probability significantly improve the quality of the work you can do, and give you the ability to tackle the very fine pitch, leadless, and miniscule components that seem to be the norm these days. I think that the manufacturer could easily do a little more to make things easier for non-US purchasers, by improving the website, fixing the “220V upgrade” and most importantly optimising the freight. If I have a criticism it is the poor documentation and the barely adequate quality of the ring light power supply. At around $1000 delivered, it is an investment on par with an entry-level oscilloscope or a top quality soldering station, so not one to be made lightly. Nevertheless, I am a complete convert, and would recommend a stereo microscope if you are doing a lot of SMT work. 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