Soldering surface mount (SMT) components is tricky, particularly if you can’t see what you are doing due to the small scale of most SMT parts. Since I started working with SMTs at home I have suffered with a 10x magnifier ring-light. It works, but it’s tricky to use, mainly because the working distance is so small that getting a soldering iron on a part and keeping that part in focus are almost mutually exclusive.
The right tool for this job is a stereo microscope. Stereo microscopes use two separate optical paths to provide you with depth perception, very helpful for working with 3-dimensional objects like printed circuit boards. Even better is a stereo zoom microscope, where the magnification factor can be changed by turning a knob instead of swapping out lenses.
Until now I assumed that a stereo zoom microscope would be way out of my price range, at least several hundred or a thousand dollars for a very basic setup. However, some searching on eBay showed that good deals can be had, and a used microscope with a boom stand suitable for surface mount work can be found for as little as $200-$300. New microscopes are available for $400-$500, although there is some debate regarding the quality of low-cost imported microscopes. Caveat emptor.
For surface mount soldering, 7-30x magnification is reasonable (that’s 10x eyepieces * a 0.7-3x objective), and a 4″ or greater working distance makes using tools under the microscope a lot easier.
I ended up buying an American Optical (AO) model 569 with an illuminator and boom stand, shown below. Total cost was just over $200 with shipping.
Combined with the PID controlled hotplate I just put together this is a very powerful setup for doing rework of very tiny components – I could probably work with 0402’s, maybe even 0201’s if I was careful. Using this setup, 0805’s are easy. (and they look huge!)
The scope is very old, it was made in the late 1970s, but it has survived in extremely good condition. Upon receiving it, I tightened some setscrews and regreased the slides and it’s as good as new, despite being over 30 years old!
There are a few more photos of the microscope setup on flickr.
The image quality is excellent. Here are a couple pictures of my SYBA USB-Audio Adapter taken with the microscope and my Sony DSC-V1 digital camera. I held the camera up to one eyepiece, set it into macro mode, and snapped the shutter – these images are straight off the camera with no retouching.
Click to enlarge.