High print quality printhead

A substrate for an inkjet printhead, the substrate comprising:

• at least 400 inkjet resistors formed on a surface of the substrate at a density of at least 6 heater resistors per square millimeter, each resistor sized to generate a vapor bubble for ejecting droplets of ink that are each less than 8 ng in drop weight;
• a thermal barrier layer underlying each resistor;
• and
• a passivation layer overlying each resistor, wherein the thermal resistance of the passivation layer relative to the thermal barrier layer is tuned to allow an electrical impulse equal to or less than 1.4 μjoules to eject a drop of ink from an ink ejector.

A printhead for an inkjet printer, comprising:

• a substrate;
• a plurality of switch circuits;
• a plurality of primitives formed on the substrate, each primitive including a plurality of resistors, each of the plurality of resistors is coupled to a separate one of the plurality of switch circuits, wherein at least some of the plurality of resistors from each resistor group has a resistance of at least 70 Ω;
• a plurality of address select leads, each address select lead coupled to one of the plurality of switch circuits for each of the plurality of primitives, selecting an address lead for a switch circuit closes the switch circuit to enable actuation of the resister that is coupled to the switch circuit, in operation, the address leads are actuated sequentially so that only one resistor in a primitive is actuated at a time;
• a plurality of primitive select leads, each of the plurality of primitive select leads is separately electrically coupled to one of the plurality of primitives, each primitive select lead has a primitive select pad for connection to a power source;
• and
• a ground lead electrically coupled to all of the plurality of primitives, the ground lead having a first ground pad and a second ground pad that is spaced apart from the first ground pad and is electrically common with said first ground pad to allow current to flow from a primitive select pad, through a particular resistor and a corresponding particular switch circuit, and out of the first and second ground pads when the address for the corresponding particular switch circuit is actuated.

A printhead for an inkjet printer, comprising;

• a substrate;
• a plurality of heater resistors disposed on said substrate and electrically arranged into a first group and a second group;
• a plurality of address select leads, each address select lead coupled to one of the plurality of heater resistors for each of the first and second groups, selection of an address select lead enabling actuation of the resistor;
• a first electrical conductor disposed on said substrate, coupled to each heater resistor in said first group, and terminating in a first terminal disposed on said substrate whereby electrical current is sourced to each heater resistor in said first group;
• a second electrical conductor disposed on said substrate, coupled to each heater resistor in said second group, and terminating in a second terminal disposed on said substrate whereby electrical current is sourced to each heater resistor in said second group;
• and
• a return electrical conductor disposed on said substrate, electrically coupled to each heater resistor in both said first group and said second group, the return electrical conductor terminating on said substrate in a first return pad and second return pad that is spaced apart from the first return pad and is electrically common with the first return pad whereby electrical current is returned to complete an electrical circuit, and wherein at least some of the resistors in the first and second groups have a resistance of more than 70 Ω to reduce parasitic power dissipation through the return electrical conductor.

A high print quality printhead for an inkjet printing device, comprising:

• a foraminous orifice plate having a thickness in the range of 20 μm to 30 μm and a plurality of ink emitting nozzles disposed therein, each nozzle of said plurality of ink emitting nozzles having an opening at an outer surface of said foraminous orifice plate having a dimension in the range of 10.5 μm to 14.5 μm;
• a semiconductor substrate having an elongated ink opening therein and a plurality of heater resistors disposed at a density of at least six heater resistors per square millimeter of substrate on a major surface of said substrate, each heater resistor associated with one of said plurality of ink emitting nozzles, each of said heater resistors having a measured resistance greater than 70 Ω and subdivided into at least a first resistor segment coupled in series with a second resistor segment via a conductive shorting bar having a notch disposed therein, said semiconductor substrate further including a first set of electrical conductors carrying electrical current to each of said heater resistors and a second set of electrical conductors carrying electrical current from each of said heater resistors, said first set of electrical conductors arranged to organize heater resistors of said plurality of heater resistors into primitives, a first primitive of said primitives comprising a first set of current controlling switches, a first control terminal of said first set of current controlling switches being coupled to at least one address line in a first set of address lines, and a second primitive of said primitives comprising a second set of current controlling switches, a first control terminal of said second set of current controlling switches being coupled to at least one address line in a second set of address lines, said second set of address lines being electrical isolated from said first set of address lines, whereby each switch in said first primitive can be activated independently of each switch in said second primitive by way of control signals on at least one address line of said first and second set of address lines, and an electrical conductor of said second set of electrical conductors coupled to heater resistors in said first primitive and said second primitive and terminating in a first terminal and a second terminal disposed spaced apart from each other on said substrate whereby electrical current is returned to complete an electrical circuit;
• and
• a barrier layer disposed between said foraminous orifice plate and said semiconductor substrate, said barrier layer being patterned into an ink manifold and a plurality of firing chambers fluidically coupled to said ink manifold by way of at least one entrance channel for each one of said plurality of firing chambers, said entrance channel including an inner pinch point formed by two entrance protrusions and a plurality of pillars extending from said major surface of said substrate to said orifice plate, disposed between said inner pinch point and said ink manifold, and spaced apart from each other at predetermined distances, adjacent pillars of the plurality of pillars forming a plurality of outer pinch points, whereby ink refill for each said firing chamber is overdamped, said ink manifold forming an elongated chamber encompassing said ink opening and having opposed ends defined by end wall portions, said end wall portions including a protrusion extending therefrom.

An inkjet printing apparatus, comprising:

• a printhead substrate;
• a plurality of primitives formed on the substrate, each primitive including an array of firing resistors, the firing resistors formed on the substrate with a density of at least 6 firing resistors per square millimeter;
• multiplexing circuitry formed on the substrate and electrically coupled to said plurality of primitives;
• and
• a plurality of input leads electrically coupled to the multiplexing circuitry, the plurality of input leads including a ground line that is electrically coupled to at least four of said plurality of primitives to reduce a number of required input leads to provide individual control of the resistors, wherein the ground line is coupled to two electrically common ground pads that are spaced apart from one another on the printhead substrate.