Soldering a Segbot Board

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Soldering the Other Surface Mount Devices

At this point, you are ready to start soldering on the smaller SMDs. Your board should have all of the larger chips soldered on and should appear something like the picture below.

Before starting to solder, note the labeling convention for the values of your SMD resistors. One of our resistors is pictured below. This is a 24.9 KOhm resistor. You can identify it as that by realizing the numbers on the device represent 249*10^2 = 24,900. You also might see only two numbers on a device. In general, the last number represents the 10^x multiplier, the second to last number represents the units digit (before multiplication), the third to last number represents the tens digit, and so on. For example, 222 on a resistor would mean 22*10^2 = 2,200 Ohm or 2.2KOhm.

To solder on a small SMD, it is usually best to presolder a pad, heat the pad up, use the tweasers to guide one end of the device on to that pad, solder the other pad, and then add a little bit of solder to the first pad. Instead of continually having to locate and relocate reels or bags of certain resistors or capacitors, I find it easiest to simply go down the list of those types of devices on the bill of materials and solder on all the devices of the same type and value at once. Therefore, I recommend picking a device, finding all of its locations on the board, presoldering one pad for each location, and then soldering on each one. After that, you are done with that type of resistor/capacitor and can set it aside so it is out of the way, and the other types are easier to find in your supply of devices. The process of soldering on an example resistor is shown below.

Presoldered Pads

Heating Pad for Resistor Placement

Resistor Placed on Pads

Both Sides Soldered and Complete

With the exception of the 47uF capacitors, the above procedure should work for all of the resistors, capacitors, and the single inductor (L1). For the larger 47uF caps, presolder a pad, heat it up, and slide the capacitor onto the pad using your hand. Make sure to orientate them such that the plastic on the capacitor and the silkscreen outline match. Finish up the soldering on both pads and you are done. The board should look similar to below at this point.

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