Abstract An improved process is provided for aligning and bonding channel and heater substrates together to form a thermal ink jet printhead. A thick film polyimide layer is formed over the heater substrate and is patterned to provide a plurality of tacking pits. The channel substrate has alignment holes formed in peripheral edge areas. A UV curable adhesive is deposited into the alignment hole and UV irradiated to produce a cured tacking column in the underlying pits formed in the thick film layer. Due to the sloping walls of the etched alignment recess, some portion of the adhesive is not fully cured and, during a subsequent curing process, tends to initiate a capillary flow along the interface between channel substrate and the thin film layer. This flow, in prior art designs, sometimes proceeds to the point where the adhesive is squeezed out onto electrode connections formed on an adjacent heater substrate. The formation of the pits serves to interrupt and trap the flow of the uncured adhesive, thus, preventing further flow and eliminating subsequent contamination.
A method for aligning and tacking together a channel and heater substrate of an ink jet printer, comprising the steps of: applying a thermosetting adhesive to the bottom surface of a channel substrate, depositing a photopatternable thick film polymer layer on the surface of a heater substrate, identifying peripheral areas of said polymer layer where tacking will be accomplished, etching said polymer layer to form a plurality of pits along a length of said identified peripheral areas, mating the channel substrate to the heater substrate with the thick film layer sandwiched therebetween, etching an alignment hole in the channel substrate in a portion of each of said identified peripheral tack areas, introducing a UV curable adhesive into said alignment hole, said adhesive filling only those pits which directly underlie said alignment hole leaving a plurality of pits not filled by said adhesive during said adhesive introduction step, irradiating said tacking adhesive with a UV light source, curing most of the introduced adhesive but leaving uncured segments, curing the tacked substrates until the thermosetting adhesive is fully cured whereby said previously uncured segments migrate in a capillary flow along the interface formed at the channel substrate and are deposited into at least some of said plurality of pits not filled during said adhesive introduction step and separating the tacking portion from the fully bonded substrates.
Claim 2
Independent Claim
224 words
A method for aligning and tacking together a channel and heater substrate of an ink jet printer, comprising the steps of: applying a thermosetting adhesive to the bottom surface of a channel substrate, depositing a photopatternable thick film polymer layer on the surface of a heater substrate, identifying peripheral areas of said polymer layer where tacking will be accomplished, etching said polymer layer to form a plurality of pits along a length of said identified peripheral areas, mating the channel substrate to the heater substrate with the thick film layer sandwiched therebetween, etching an alignment hole in the channel substrate in a portion of each of said identified peripheral tack areas, introducing a UV curable adhesive into said alignment hole, said adhesive filling only those pits which directly underlie said alignment hole leaving a plurality of pits not filled by said adhesive during said adhesive introduction step, irradiating said tacking adhesive with a UV light source, curing most of the introduced adhesive but leaving uncured segments, curing the tacked substrates until the thermosetting adhesive is fully cured whereby said previously uncured segments migrate in a capillary flow along the interface formed at the channel substrate and are deposited into at least some of said plurality of pits not filled during said adhesive introduction step and separating the tacking portion from the fully bonded substrates.