Heat, cooling and pressure are the main reasons thermal printheads fail. As thermal transfer ribbon (TTR) is fed past the printhead, small resistor elements, known as dots are heated by applying an electric current to them. The heat from the dots is then transferred to either the direct thermal paper (media) or thermal transfer ribbon. This dot pattern produces the text, barcode or image on the label.
Because the dots must be heated and cooled very rapidly, and there is friction as the ribbon or paper passes against the printhead, the printhead will eventually wear out. As the printhead ages, the output will become lighter or sections of dots may stop heating and cause voids in the print.