Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1999-12-16
2002-03-19
Le, N. (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S050000
Reexamination Certificate
active
06357864
ABSTRACT:
TECHNICAL FIELD
This invention relates to the field of printhead cartridge bodies contained within inkjet printers. More particularly, this invention relates to a printhead cartridge body which includes a tape automated bonding (TAB) circuit having a plurality of apertures for connecting to a printed circuit board (PCB) and a printhead heater chip located on the printhead cartridge body.
BACKGROUND OF THE INVENTION
Tape automated bonding (TAB) circuits are improved circuit mounting structures that are used to interconnect electronic elements in advanced microelectronic devices. TAB circuits can be used to electrically connect a semiconductor chip to a printed circuit board (PCB). Misalignment errors are common when connecting the TAB circuit to the PCB. Many TAB circuits are constructed having a polyimide layer enclosing the conductive traces, so visually inspecting the circuits for proper alignment is difficult. Furthermore, testing the circuit for open or short circuits can be a time consuming and expensive process since the electrical connections are not easily accessible. In prior art TAB circuits applications, misalignment errors were corrected by physically disassembling the connected circuits which usually destroyed one or both of the circuits.
Hot bar refers to the use of a heated metal or ceramic bar which is an efficient connection method used to form a solder joint between many electrical connectors at the same time. Hot bar is a technique that can be used to interconnect a flexible circuit to a PCB. Particularly, hot bar can be used to interconnect a PCB to a flexible TAB circuit.
In many hot bar applications, a flexible polyimide TAB circuit with conductive traces on one side of the circuit is connected to the electrical connectors of a PCB by transferring the heat from the hot bar through the polyimide and into the circuit trace. The transferred heat causes the PCB's solder to flow, which electrically connects the PCB to the TAB circuit. Flexible TAB circuit designs sometimes utilize a small opening as a vent so that excess solder can flow away from the electrical connections. Since the traces of a TAB circuit are covered by polyimide, which acts as an insulator, the hot bar must transfer heat first through the polyimide layer before transferring heat to the underlying traces and PCB solder. By forcing heat transfer through a polyimide layer first, longer hot bar application times or higher heating temperatures are required, resulting in increased bonding time and production costs. The increased hot bar temperatures may also be detrimental to the polyimide material which may cause premature failure of the flex circuit.
Complications may occur if it is determined that an electrical connection within the PCB/TAB circuit configuration might be defective and the electrical connections need to be inspected. Since there is a polyimide surface covering the electrical connections, the entire circuit has to be removed to rework the electrical connections. Removing the circuit can destroy or significantly impair the electrical connectors of both the PCB and the TAB circuit. As a consequence, rework can be quite an expensive process.
TAB circuitry is useful since the traces and polyimide can be configured to the users specifications in a cost effective manner. However, because printhead cartridge body space is constrained by the area of printer, TAB circuit designs have been correspondingly limited. Therefore, improvements to the TAB circuit architecture are limited by the amount of TAB circuit surface area.
Adding to the design criteria of the TAB circuitry utilized within an inkjet printer is the ink contained within the printer. Ink is a highly corrosive contaminant to any exposed metal that is subjected to the ink. TAB circuitry containing exposed conductive metal traces will be subject to the highly corrosive ink within the inkjet printer and correspondingly the trace material can degrade after a short period of time, normally resulting in a short or open circuit.
What is needed therefore, is a TAB circuit which reduces hot bar processing times and temperatures, while enabling easy access to the electrical connections when the TAB circuit is being connected to a PCB. Furthermore, there is a need for preventing corrosion and deterioration of the electrical connections from ink mist within the inkjet printer.
SUMMARY OF THE INVENTION
With regard to the above, and other objects, the invention provides a printhead cartridge body for an inkjet printer which includes a TAB circuit having a unique architecture for improved manufacturing operations. Moreover, the TAB circuit architecture is readily sealable by a variety of methods.
The printhead cartridge body includes a TAB circuit having a first region, which further includes a first face and a second face. The first region of the TAB circuit also includes a first axis and a second axis that is substantially perpendicular to the first axis. The TAB circuit includes a second region, which contains a first face and a second face. The second region of the TAB circuit also includes a first axis and a second axis that is substantially perpendicular to the first axis.
A plurality of conductive traces are located on the second face of the first region and on the second face of the second region of the TAB circuit. Each trace has a first end and a second end. The first end of each trace is substantially parallel with the second axis of the first region of the TAB circuit. The second end of each trace is electrically connected to a printhead heater chip.
The first region of the TAB circuit contains at least two rectangular apertures. A length and a width define each aperture. A first axis extends along the length of each aperture and a second axis extends along the width of each aperture. The first axis of each aperture is aligned with the first axis of the first region of the TAB circuit. The second axis of each aperture is aligned with the second axis of the first region of the TAB circuit. An encapsulant layer is provided which substantially encloses the rectangular apertures preventing ink mist from penetrating into the apertures.
The printhead cartridge body also contains a PCB having a first face and a second face. The PCB includes a first axis and a second axis substantially perpendicular to the first axis. The PCB also includes a plurality of conductive contacts. The conductive contacts are electrically connected to the first ends of the conductive traces of the TAB circuit. The first face of the PCB is arranged adjacent to the second face of the first region of the TAB circuit. Furthermore, the first axis of the PCB is aligned substantially parallel with the first axis of the first region of the TAB circuit.
Additionally, the printhead cartridge body includes a printhead heater chip, having a first face and a second face. The printhead heater chip has a first axis and a second axis that is substantially perpendicular to the first axis. The printhead heater chip also includes a plurality of conductive contacts. The conductive contacts arc electrically connected to the second ends of the conductive traces of the TAB circuit. The first face of the printhead heater chip is arranged adjacent the second face of the second region of the TAB circuit. Moreover, the first axis of the printhead heater chip is aligned substantially parallel with the first axis of the second region of the TAB circuit.
The printhcad cartridge body including the TAB circuit with PCB region apertures as described above, is advantageous in a variety of ways. First, the hot bar cycle time period is much faster since heat does not have to be transferred through the polyimide layer, because the hot bar is applied directly to the exposed TAB circuit traces and solder on the conductive contacts of the PCB. Secondly, solder can flow around the entire TAB circuit lead providing a stronger junction between the TAB circuit and the PCB. In prior art systems, where KAPTON or analogous polymeric material covers one side of the lead, only the bottom and sides of th
Anderson Frank Edward
Reeves Kris Ann
Saldanha Singh Jeanne Marie
Spivey Paul Timothy
Sullivan Carl Edmond
Lambert D. Brent
LaRose David E.
Le N.
Lexmark International Inc.
Sanderson Michael T.
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