So you need to solder something small, but it is so tiny you can’t see it properly. This is often the case with surface mount components (SMD), and we will show you an easy way to handle it.
Before deciding on which solution to use, you should determine what your requirements are.
For us, it was key to have a responsive system, a comfortable working position when soldering, a light, portable solution (at least that we can stack away easily), and of course, enough magnification to see very small components. The list became rather extensive but it is important to list all your ‘wants’ upfront and then peel away the unobtainable ones later.
In the end, our requirement list looked like this:
- high magnification level
- responsive, i.e. high frame rate, if a camera
- long distance focus so there is enough room for tools and soldering irons under the magnifier
- light and small equipment
- built-in or easily added light/illumination
- possibility to make a recording/video (to create instructional videos)
- affordable, since we’re on a tight budget (max $100)
We searched the web for different solutions, but most fell on a single parameter: price. There are many nice bench-top microscopes built for soldering, but none that fit our budget — normally by a factor of 15x in price!
We looked at using video cameras with close-up lenses, popular with some bloggers. It may’ve worked fine, but we didn’t want to risk our only video camera getting splashed with 250 degree Celsius melted solder.
Another option was to use a web camera. We tested the idea with an old camera, and found the magnification and focus distance weren’t a practical setup.
We also looked at so-called, USB microscopes. They are essentially a web camera with a different lens. There are, of course, a whole flood of these devices on the market so how do we choose one? In our case, we started with a list of requirements, so we assumed it would be fairly easy.
Well, it wasn’t so easy, mainly due to poor documentation. Many product sheets and specifications don’t contain even the most basic optical performance information. How can one possibly decide on which product to buy? To choose, we simply excluded the ones without useful or enough information.
We settled on a USB microscope camera with 1.3 megapixel resolution, adjustable focus from 10mm to infinity (as stated), and up to 200x magnification. The resolution was chosen since many devices don’t support fast data transfer over the USB channel, and 1.3 megapixel is as low as we wanted to go on resolution (lower resolution means less data in each image frame to transfer to a computer). Since the frame rate isn’t always constant and limited by the exposure time (depending on the camera’s sensitivity), we opted to add 2 USB powered LED lamps.
Our camera has LEDs built-in, which give sufficient light when the camera is close to the target object. When 10-15cm away from the object, more light is necessary to keep the exposure times down and the frame rate high (for a more responsive system). There is a lag, but it is not so long the device becomes unusable.
To make the setup truly useable in daily applications we needed a stable and quick setup. For this reason, we used a piece of wood as a base to hold all the other parts together.
We started by gluing the USB hub to the back of the wooden base. This is easy with a hot glue gun.
Then we positioned the USB camera holder (included with the USB camera) and drilled a 3mm hole through the metal base of the camera holder and the wood base.
With a screw, we fixed the camera holder in position. We then put the lamps and the fan in the USB hub, took a cell phone charger with USB connection and plugged in the hub’s male connector.
PC or Mac? Our camera came with software for PCs but since we use Mac and Linux computers we wanted to see if it worked on those as well. The device is a generic USB camera and you can run the preview in a default applications in OS X, such as Photobooth and FaceTime. When you expand the image window over your screen you will get an enlarged image.
Because Mac comes with QuickTime player, you can also record screen captures directly without the need to add extra software.
To record a screen capture/video of what you are magnifying, do the following: start the program you want to capture with, e.g. Photobooth, then start QuickTime player and select File > New Screen Recording in the menu. Click the red record button and then drag a rectangle with your mouse (click and drag) around the window you want to record. Start recording by clicking on the button on the screen. You can save your captured video in different formats, email it, etc.
On an Ubuntu Linux computer, we downloaded and installed the Cheese application. The open application shows a live video from your connected camera or you can choose which camera to use (that is, if your computer has a built-in camera as most laptops).
Back to the microscope question. So what about the size? Cameras like this come in different sizes and ours isn’t one of the smallest, measuring 140mm in length by 37mm in diameter. The whole kit — with microscope, USB hub, fan, and the two LED lamps — fits neatly in a shoe box. This way, it can also be stashed easily.
In the image, you can see how our setup looks with all pieces connected. The magnified live image is shown on the laptop screen in the background. For demonstration purposes we used a SMT soldering kit that you can find online.
Magnification… How about that? Our camera is listed with “up to” 200x magnification, but what does that mean in practice? In short, you can say that the closer you place the camera to your target, the higher magnification you get.
Since we chose a camera designed to allow focusing from far distances, we can focus on the target ~10cm away without a problem. At this distance, the magnification is around 11x (an object is 11 times larger in the screen than in real life). This works fine for the intended purpose.
The resolution is also sufficient for our needs. We can even see the individual solder balls in the solder paste here.
Did it work out to solder the surface mount components?
Yes, it worked well, even despite that our solder paste was a bit dry. The dryness was surprising since we just bought it from an electronics store (likely due to them storing it too long). Solder paste has a pretty short shelf life and even shorter once opened. In the images you can see how the solder paste is not sticky and keeping together.
Applying heat with a hot air rework station, the solder paste melts and the surface tension actually pulls the components into place.
As you see in the image, the resistors R2 and R5 are not placed straight into their positions but after the solder melted this is corrected (see final result below). We didn’t do anything other than melt the solder.
All in all, we managed to put together a kit for magnifying soldering jobs, magnifying coins, stamps or similar, or even your kids science project for less than $100.
It works, it’s fairly responsive, portable and easy to setup, and we can capture video of what we did (even stream it live using FaceTime). Great!