Board assembly requires the following:
- all the electronic components
- Solder paste
- Stencil mask or other solder paste application implement
- Reflow tool
Manual assembly of the components onto the board is the best way to go when making a few prototypes. To do this assembly place solder paste by hand or using a stencil. Sparkfun has a nice stenciling tutorial. Another option is to use a sharp probe to place solder paste individually on each pad on the PCB. This is slower than the stencil approach but it is good enough when doing one board at a time. Then, using tweezers place each component on the board. Having an optical microscope helps but the work can still be done without a microscope.
After placing all components reflow the solder. The simplest method is to use and electric skillet or a hot plate. A number of DIY reflow oven projects have been done that work as well. The skillet method is probably the easiest to start with. This board was reflowed on a Oster electric skillet from Target. Place your board on the skillet. Turn the temperature setting to about 400 degrees F. Wait about 5 minutes. Turn off the skillet. Let the board cool a few minutes before removing it from the skillet. This method should produce the approximate temperature profile required for surface mount soldering of most components.
At this point you should have a fabricated board that is ready to be programmed.