Shortly afer I joined Spectrum Astro (July 2000) and was assigned to work on the Swift gamma ray explorer mission, I built a 1/20 scale model and presented it to our program manager. This model is mostly made of foam-board and heavy poster board with a few plastic parts. Since the model would be covered entirely in thermal blankets (using the actual aluminized kapton as we use on our satellites), seams and underlying construction material did not matter much.
The spacecraft electronic boxes are mounted externally and are made of lightweight cardboard covered in kapton. There is a large sunshade on the top made of a balsa wood frame covered in aluminum foil on the outside and black "Pizzazz" brand mylar wrapping film. A few small parts (antennas, torque rods, etc.) are made of bits of plastic.
Solar panels are poster board with the cells made in two layers. First, I drew a cell pattern of small rectangles on the computer and printed it on transparency film. I applied spray adhesive to one side of the transparency and laid down a sheet of purple-colored "Pizzazz" brand mylar wrapping foil that I found at a card shop. I cut that out to match the edge of the solar cells, then sprayed the colored mylar with a coat of adhesive and attached it to the cardboard panels. This resulted in the cell pattern on top with a glossy glass-like finish, violet cells underneath, all attached to a rigid substrate. Almost like the real thing! Note the backside of the solar panels are left white, which is common on many spacecraft. In actuality, Swift wound up with unpainted graphite epoxy (black) panels with a lot of white wiring visible. I did not bother to add that effect on this model.