Page 17 - Make Your Own PCBs with EAGLE from Schematic Designs to Finished Boards

FIGURE 1-2 Through-hole and surface-mount components.

Surface-mount components are often referred to as surface-mount devices (SMDs) and are
replacing through-hole components in most commercial products. This is so because SMD
components are smaller and cheaper than their through-hole counterparts, and the boards that use them
are also easier to make. You will also see the term surface-mount technology (SMT) used.

In commercial surface-mount PCB production, and increasingly for hobbyists, boards are
soldered by creating a mask that allows solder paste to be deposited on the pads, then the components
are placed precisely on the pads, and then the whole board is baked in an oven that melts the solder
paste, soldering the components without the difficulty of soldering each component separately.

SMD ovens are still too expensive for most hobbyists, but many people have had success
modifying toaster ovens to operate at the high and precisely controlled temperatures required. Such
experiments usually require the safety features of the toaster oven to be disabled and are therefore
often referred to as “fire starters” for good reason. However, like so many things in life, with care,
common sense, and a watchful eye, such things can be made to work safely.

The choice of surface-mount versus through-hole design is less cut and dried for the hobbyist just
wanting to make one or two boards for a specific project. For a single project that is never intended
to be made as a commercial product, through-hole design is much simpler to solder by hand. Through-

hole component leads are nearly always at least 0.1 in. apart, whereas surface-mount chips can have