This is by far the most common method for most inexpensive keyboards. There are a wide variety of ways that the legend is printed onto the keycap, the important distinction is that the dye is simply on top of the keycap. Because of this, pad printed legends are notorious for their rate of wear. The legends will fade or disappear over time.
Laser printing is gaining popularity and is the second most commonly used manufacturing method, after pad printing. There are three main ways to use lasers in keycap production.
Laser Etching- Also known as charring, this method is most commonly used for light-colored keycaps. It uses a laser to burn the plastic, leaving behind a black legend on the keycap.
Laser Etching with Paint Fill- This method also burns grooves into the plastic. Those grooves are then filled in with colored paint. This is a common method for darker colored keycaps.
Laser Engraving- This is the most common way to produce backlit keycaps. A transparent keycap is covered in black paint, then the legend is engraved, allowing backlighting to shine through.
Dye sublimation or dye-subbed is an alternative to printing and is commonly used on PBT keycaps because of their higher heat resistance. The dye is pressed shallowly into the keycap through heating.
Double Shot Keycaps
Double shot injection molding is the most expensive and complex process. In this method, the keycap is produced by first forming one section of the keycap in a mold, then, another colored plastic is added to make up the rest of the keycap. This allows two colors to be used to form a single keycap.
Since the legend and surrounding keycap are both individual pieces of plastic, they wear at the same rate and the legends won’t rub off over time.
Double shot production is mainly used with ABS plastics but there are some double shot PBT keycaps beginning to emerge.