Structure of thermal printhead

Photo of thermal printheads

The typical structure of the thermal print head is shown in the figure below. The overall structure is supported by the heat sink (Base). The Base is made of various materials such as aluminum plate, aluminum profile, stainless steel plate, galvanized cold-rolled plate, and plastic, which are mainly used for support and heat dissipation. In addition to the function of marking (you can print code or stick a label on it), the function of connection
(connect the thermal print head and the relevant parts on the printer), and then use double-sided tape to attach the printed circuit board (PCB) and the ceramic substrate (SBS). ) is pasted to the heat sink, the printed circuit board is mainly used for the connection of electrical signals, the printed circuit board will detect the temperature of the print head by welding the thermistor, provide a temperature feedback signal, and the welding socket provides the peripheral circuit interface; the ceramic substrate is the heating body The carrier with the conductive line; the driver IC is connected with the heating body and the PCB through the wire, and then fixed and protected with the encapsulant. Generally, a glass layer is printed on the finished ceramic substrate to protect the circuit and the heating element. The print head is mainly in contact with the heating body and the medium, so the wear of the heating body directly determines the life of the print head. Some thermal print heads will use a thin film technology to coat a protective film on the heating body, considering the wear resistance of the protective film. Generally speaking, SiC films with stable properties and high hardness are selected.

Assembly drawing of thermal printhead

Finished drawing of thermal printhead

The most common thermal printer uses a fixed print head with a heated dot matrix. The print head shown in the figure has 320 square dots, each of which is 0.25mm * 0.25mm. Using this dot matrix, the printer can print on any position of the thermal paper. This technology has been used on receipt printers and label printers.Usually, the paper feed speed when printing by thermal printer is used as the evaluation index. However, some printers can print twice as fast when the label format is optimized. This thermal printer process is relatively simple, so it can be made into a portable battery-operated thermal label printer. Due to the flexible format, high image quality, fast speed and low cost printed by thermal printers, the barcode labels printed by it are not easy to be stored in an environment higher than 60°C, or exposed to ultraviolet light (such as direct sunlight) for long time. Therefore, thermal labels are usually limited to indoor use.