Precautions of thermal print head
Electrical Precautions
1. Circuits should be designed to shut down VH (heater voltage) to GND level during stand-by mode in order to avoid damage to the printhead by ion, noise, etc.
2. Exceeding the specified limit of the number of simultaneous printing dots will reduce the power per heater element due to the power loss in the circuit pattern of the printhead, causing insufficient optical density. It will also increase the current flow resulting in higher noise level; appropriate design for noise reduction is recommended.
3. Circuits should be designed so as to stop printing to avoid overheating when the thermistor is damaged.
4. Each wiring resistance and length from VH and GND to the printhead is recommended to be less than 10mΩ and 100cm. Also the power supply line is recommended to be kept away from the signal line so as not to produce any electrical interference.
5. Signal inputs of CLOCK, LATCH, DATA, and STROBE should be interfaced by C-MOS (74HC240) or equivalent.
6. An electrolytic aluminum capacitor of 15V and 33μF level should be placed between VDD and GNDL to avoid noise.
7. Power on sequence should be in the order of VDD first and VH next. Power off sequence should be in the reverse order with VH first and VDD next. STROBE signal should be disabled when the power supply is turned on or off.
Mechanical Precautions
1. Platen shaft shall be designed not to bend and rubber thickness is recommended to be more than 2.0mm.
2. When local platen pressure is higher than the limit, the life of the printhead is shortened. Appropriate mechanical design is required to have an even pressure across the paper width.
Handling Precautions
1. Substrate temperature should not exceed the maximum limit when continuously printing at a high duty to avoid breakdown of heater elements.
2. Paper residue on the heater line should be removed with ethanol or IPA to avoid corrosion.
3. Do not touch the heater line surface with bare hands to avoid corrosion.
4. Please use thermal paper and ink-ribbons that are free from Na+, K+, and CI- ions and of which the reliability is fully evaluated to avoid corrosion.
5. The heater surface should be free from any condensation to avoid corrosion. In case condensation is found, please turn off the VH until condensation evaporates.
