Patent Application
20070070122
The disclosure relates to micro-fluid ejection devices, and in particular to improved methods for making micro-fluid ejection head structures that have precisely formed flow features.
Micro-fluid ejection heads are useful for ejecting a variety of fluids including inks, cooling fluids, pharmaceuticals, lubricants and the like. A widely used micro-fluid ejection head is in an ink jet printer. Ink jet printers continue to be improved as the technology for making the micro-fluid ejection heads continues to advance. New techniques are constantly being developed to provide low cost, highly reliable printers which approach the speed and quality of laser printers. An added benefit of ink jet printers is that color images can be produced at a fraction of the cost of laser printers with as good or better quality than laser printers. All of the foregoing benefits exhibited by ink jet printers have also increased the competitiveness of suppliers to provide comparable printers in a more cost efficient manner than their competitors.
One area of improvement in the printers is in the micro-fluid ejection head itself. This seemingly simple device is a relatively complicated structure containing electrical circuits, ink passageways and a variety of tiny parts assembled with precision to provide a powerful, yet versatile micro-fluid ejection head. The components of the ejection head must cooperate with each other and with a variety of ink formulations to provide the desired print properties. Accordingly, it is important to match the ejection head components to the ink and the duty cycle demanded by the printer. Slight variations in production quality can have a tremendous influence on the product yield and resulting printer performance.
The primary components of an exemplary micro-fluid ejection head are a substrate, a nozzle member (e.g., a nozzle plate) and a flexible circuit attached to the substrate. The substrate can be made of silicon and have various passivation layers, conductive metal layers, resistive layers, insulative layers and protective layers deposited on a device surface thereof. Fluid ejection actuators formed on the device surface may be thermal actuators or piezoelectric actuators, for example. For thermal actuators, individual heater resistors are defined in the resistive layers and each heater resistor corresponds to a nozzle (e.g., a hole) in the nozzle member for heating and ejecting fluid from the ejection head toward a desired substrate or target.
The nozzle members typically contain hundreds of microscopic nozzles for ejecting fluid therefrom. A plurality of nozzle members are usually fabricated in a polymeric film using laser ablation or other micro-machining techniques. Individual nozzle members are excised from the film, aligned, and attached to the substrates on a multi-chip wafer using an adhesive so that the nozzles align with the heater resistors. The process of forming, aligning, and attaching the nozzle members to the substrates is a relatively time consuming process and requires specialized equipment.
Fluid chambers and ink feed channels for directing fluid to each of the ejection actuator devices on the semiconductor chip are typically either formed in the nozzle member material or in a separate thick film layer. In a center feed design for a top-shooter type micro-fluid ejection head, fluid is supplied to the fluid channels and fluid chambers from a slot or ink via which is formed by chemically etching, dry etching, or grit blasting through the thickness of the substrate. The substrate, nozzle member and flexible circuit assembly is typically bonded to a thermoplastic body using a heat curable and/or radiation curable adhesive to provide a micro-fluid ejection head structure.
In order to decrease the cost and increase the production rate of micro-fluid ejection heads, newer manufacturing techniques using less expensive equipment is desirable. These techniques, however, must be able to produce ejection heads suitable for the increased quality and speed demanded by consumers. As the ejection heads become more complex to meet the increased quality and speed demands of consumers, it becomes more difficult to precisely manufacture parts that meet such demand. Accordingly, there continues to be a need for manufacturing processes and techniques which provide improved micro-fluid ejection head components.
The present disclosure includes a method of making a micro-fluid ejection head structure, and micro-fluid ejection head components and structures made by the method. In one embodiment, the method includes providing a substrate having a plurality of fluid ejection actuators on a device surface thereof. The device surface of the substrate also has a thick film layer comprising at least one of fluid flow channels and fluid ejection chambers therein. A removable anti-reflective material is applied to at least one or more exposed portions of the device surface of the substrate. A nozzle layer is applied adjacent to the thick film layer. The nozzle layer is imaged (and in some embodiments developed) to provide a plurality of nozzles in the nozzle layer, and the non-reflective material is removed from the exposed portions of the device surface of the substrate.
In another embodiment there is provided a method for providing an improved micro-fluid ejection head nozzle member having improved nozzle characteristics. According to the method, a nozzle layer is imaged in the presence of a removable anti-reflective material covering at least exposed portions of a device surface of a substrate to which the nozzle layer is attached. In some embodiments, the imaged nozzle layer is developed to provide a plurality of nozzles therein. The removable anti-reflective layer is removed from the substrate to which the nozzle member is attached.
An advantage of the embodiments described herein can include that they may provide an improved micro-fluid ejection head structures and, in particular, improved nozzle members for micro-fluid ejection heads. Another advantage can include that the methods may enable the formation of nozzles that have a precise size and shape in a nozzle member after the nozzle member has been attached to a micro-fluid ejection head structure. Other advantages of the embodiments described herein may include an ability to readily remove a material that enables such precise nozzles formation in the nozzle member.
Further features and advantages of the disclosed embodiments will become apparent by reference to the detailed description when considered in conjunction with the figures, which are not to scale, wherein like reference numbers indicate like elements through the several views, and wherein:
With reference to
The cartridge body 12 may preferably be made of a metal or a polymeric material selected from the group consisting of amorphous thermoplastic polyetherimide available from G.E. Plastics of Huntersville, N.C. under the trade name ULTEM 1010, glass filled thermoplastic polyethylene terephthalate resin available from E. I. du Pont de Nemours and Company of Wilmington, Del. under the trade name RYNITE, syndiotactic polystyrene containing glass fiber available from Dow Chemical Company of Midland, Mich. under the trade name QUESTRA, polyphenylene oxide/high impact polystyrene resin blend available from G.E. Plastics under the trade names NORYL SE1 and polyamide/polyphenylene ether resin available from G.E. Plastics under the trade name NORYL GTX. A preferred polymeric material for making the cartridge body 12 is NORYL SE1 polymer.
The substrate 14 can include a silicon semiconductor substrate 14 having a plurality of fluid ejection actuators, such as piezoelectric devices or heater resistors 22, formed on a device side 24 of the substrate 14, as shown in the simplified illustration of
The substrates 14 are relatively small in size and typically have overall dimensions ranging from about 2 to about 8 millimeters wide by about 10 to about 20 millimeters long and from about 0.4 to about 0.8 mm thick. In conventional substrates 14, the fluid supply slots 26 are grit-blasted in the substrates 14. Such slots 26 typically have dimensions of about 9.7 millimeters long and 0.39 millimeters wide. Fluid may be provided to the fluid ejection actuators by a single one of the slots 26 or by a plurality of openings in the substrate 14 made by a dry etch process selected from reactive ion etching (RIE) or deep reactive ion etching (DRIE), inductively coupled plasma etching, and the like.
The fluid supply slots 26 direct fluid from a reservoir 20, for example, which is located adjacent fluid surface 30 of the cartridge body 12 (
Prior to attaching the substrate 14 to the cartridge body 12, the nozzle member 16 is attached to the device side 24 of the substrate, such as by use of one or more adhesives 34. The adhesive 34 used to attach the nozzle member 16 to the substrate 14 can include a heat curable adhesive such as a B-stageable thermal cure resin, including, but not limited to phenolic resins, resorcinol resins, epoxy resins, ethylene-urea resins, furane resins, polyurethane resins and silicone resins. In an exemplary embodiment, a phenolic butyral adhesive, which is cured using heat and pressure, is used as an adhesive 34 for attaching the nozzle member 16 to the substrate 14. The nozzle member adhesive 34 may be cured before attaching the substrate/nozzle member assembly 14/16 to the cartridge body 12.
As shown in detail in
The excised nozzle members 16 are attached to a wafer 42 comprising a plurality of substrates 14 (
An improved micro-fluid ejection head structure 44 is illustrated in
According to the embodiment illustrated in
One difficulty faced by manufacturers of the micro-fluid ejection heads 44 described above is that during the formation of the nozzles 50 with laser or ultraviolet imaging techniques, radiation is scattered and/or reflected by the device surface 24 of the substrate 14. Such radiation may be effective to distort the size of the nozzles 50 or form irregular nozzle shapes. Conventional, non-removable, anti-reflective coatings applied to the device surface 24 of the substrate 14 cannot be used since such coatings may cause delamination of the thick film layer 46 from the substrate 14, and may impact fluid flow properties and fluid ejection properties if allowed to remain on the heater resistors 22.
Accordingly, embodiments of the disclosure, described and illustrated in more detail below, provide improved methods for reducing scattering or reflection of radiation by the device surface 24 of the substrate 14 during nozzle formation processes. Scattering and/or reflection of radiation from the device surface 24 of the substrate 14 is substantially reduced by use of a removable anti-reflective material that, in some embodiments, is also pattemable. In one embodiment, an anti-reflective material that is selected to reduce ultraviolet (UV) reflections may be used. Such material may have an index of refraction, when measured at the wavelengths of UV radiation used for imaging the nozzles 50 that is lower than an index of refraction of the nozzle layer 48. In another embodiment, an anti-reflective material may be selected that absorbs UV radiation at the wavelengths used for imaging the nozzles 50 in the nozzle member material 48. In other embodiments, an anti-reflective material that absorbs UV radiation and that has an index of refraction that is lower than the index of refraction of the nozzle layer 48 may be used. Such removable and/or pattemable anti-reflective materials may be selected from positive or negative photoresist materials containing UV absorbent fillers, UV sensitive acrylic materials, UV sensitive polyurethane acrylics, UV sensitive polyimide resins, and water-soluble materials, including but not limited to, polyvinyl acetate, polyacrylamide, and polyethylene oxide.
For example, a positive photoresist material that is sensitive to g-line (436 nanometers) or broadband g,h,i-line (365 to 436 nanometers) UV radiation may be filled with an i-line (365 nanometers) dye or pigment to provide a patternable and removable anti-reflective material that may be applied to the thick film layer 46 and device surface 24 of the substrate 14. Such dye or pigment filled positive photoresist may be patterned using 436 nanometer radiation and developed so that it remains in the fluid chambers 54 and over the heater resistors 22 and/or electrical contacts on the device surface 24 of the substrate 14. During the formation of the nozzles 50 using UV radiation, UV radiation is absorbed by the anti-reflective material so that no significant amount of 365 nanometer radiation is reflected off the device surface 24 of the substrate 14 thereby causing irregular nozzle formation.
Specific examples of patternable and removable anti-reflective materials include polymethyl methacrylate resists containing about 2.6 wt. % coumarin 6 laser dye, a polyimide silane type resin containing a UV absorbing dye, polysulfonyl esters, polybutylsulfone containing a UV absorbing material such as bis-(4-azidophenyl)ether, naphthalene, anthracene, and tetracene. UV absorbing dyes that may be used with positive and negative photoresist materials include, but are not limited to, curcumin and its derivatives, bixin and its derivatives, coumarin derivatives, and halogenate, hydroxylated, and carboxylated dyes and combinations thereof. UV absorbing pigments that may be included in positive and negative photoresist materials include, but are not limited to, blue pigment available from Ciba Specialty Chemicals of Tarrytown, N.Y. under the trade name CIBA IRGALITE blue GLO, and black pigments available from Abbey Group Companies of Philadelphia, Pa. under the trade name ABCOL black 16 BR-126%, and from Tokai Carbon Co., Ltd, of Tokyo, Japan under the trade name AQUA-black 162. The removable and/or patternable anti-reflective material may be applied to the device surface 24 of the substrate 14 with a thickness ranging from about the wavelength of UV radiation (300 nanometers) up to about 30 microns or more.
Methods for making micro-fluid ejection heads 44 according to some exemplary embodiments of the disclosure will now be described with reference to
The multi-functional epoxy component of a photoresist formulation used for providing the thick film layer 46 may have a weight average molecular weight of about 3,000 to about 5,000 Daltons as determined by gel permeation chromatography, and an average epoxide group functionality of greater than 3, preferably from about 6 to about 10. The amount of multifunctional epoxy resin in the photoresist formulation for the thick film layer 46 can range from about 30 to about 50 percent by weight based on the weight of the cured thick film layer 46.
A second component of a photoresist formulation for the thick film layer 46 is the di-functional epoxy compound. The di-functional epoxy component may be selected from di-functional epoxy compounds which include diglycidyl ethers of bisphenol-A (e.g. those available under the trade designations “EPON 1007F”, “EPON 1007” and “EPON 1009F”, available from Shell Chemical Company of Houston, Tex., “DER-331”, “DER-332”, and “DER-334”, available from Dow Chemical Company of Midland, Mich., 3,4-epoxycyclohexylmethyl-3,4-epoxycyclo-hexene carboxylate (e.g. “ERL-4221” available from Union Carbide Corporation of Danbury, Connecticut, 3,4-epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6-methylcyclohexene carboxylate (e.g. “ERL-4201 ” available from Union Carbide Corporation), bis(3,4-epoxy-6-methylcyclohexylmethyl) adipate (e.g. “ERL-4289” available from Union Carbide Corporation), and bis(2,3-epoxycyclopentyl) ether (e.g. “ERL-0400” available from Union Carbide Corporation.
An exemplary first di-functional epoxy component is a bisphenol-A/epichlorohydrin epoxy resin available from Shell Chemical Company of Houston, Tex. under the trade nane EPON resin 1007F having an epoxide equivalent of greater than about 1000. An “epoxide equivalent” is the number of grams of resin containing 1 gram-equivalent of epoxide. The weight average molecular weight of the di-functional epoxy component is typically above 2500 Daltons, e.g., from about 2800 to about 3500 weight average molecular weight. The amount of the di-functional epoxy component in the thick film photoresist formulation may range from about 30 to about 50 percent by weight based on the weight of the cured resin.
The photoresist formulation for the thick film layer 46 may also include a photoacid generator devoid of aryl sulfonium salts. The photoacid generator can be a compound or mixture of compounds capable of generating a cation such as an aromatic complex salt which may be selected from onium salts of a Group VA element, onium salts of a Group VIA element, and aromatic halonium salts. Aromatic complex salts, upon being exposed to ultraviolet radiation or electron beam irradiation, are capable of generating acid moieties which initiate reactions with epoxides. The photoacid generator may be present in the photorsist formulation for the thick film layer 46 in an amount ranging from about 5 to about 15 weight percent based on the weight of the cured resin.
Of the aromatic complex salts which are suitable for use in an exemplary photoresist formulation disclosed herein, suitable salts are di- and triaryl-substituted iodonium salts. Examples of aryl-substituted iodonium complex salt photoacid generaters include, but are not limited to: diphenyliodonium trifluoromethanesulfonate, (p-tert-butoxyphenyl)phenyliodonium trifluoromethanesulfonate, diphenyliodonium p-toluenesulfonate, (p-tert-butoxyphenyl)-phenyliodonium p-toluenesulfonate, bis(4-tert-butylphenyl)iodonium hexafluorophosphate, and diphenyliodonium hexafluoroantimonate.
An exemplary iodonium salt for use as a photoacid generator for the embodiments described herein is a mixture of diaryliodonium hexafluoroantimonate salts, commercially available from Sartomer Company, Inc. of Exton, Pa. under the trade name SARCAT CD 1012
A photoresist formulation for the thick film layer 46 may optionally include an effective amount of an adhesion enhancing. agent such as a silane compound. Silane compounds that are compatible with the components of the photoresist formulation typically have a functional group capable of reacting with at least one member selected from the group consisting of the multifunctional epoxy compound, the difunctional epoxy compound and the photoinitiator. Such an adhesion enhancing agent may be a silane with an epoxide functional group such as a glycidoxyalkyltrialkoxysilane, e.g., gamma-glycidoxypropyltrimethoxysilane. When used, the adhesion enhancing agent can be present in an amount ranging from about 0.5 to about 2 weight percent, such as from about 1.0 to about 1.5 weight percent based on total weight of the cured resin, including all ranges subsumed therein. Adhesion enhancing agents, as used herein, are defined to mean organic materials soluble in the photoresist composition which assist the film forming and adhesion characteristics of the thick film layer 46 on the device surface 24 of the substrate 14.
The thick film layer 46 may be applied to the device surface 24 of the substrate by a variety of conventional semiconductor processing techniques, including but not limited to, spin-coating, roll-coating, spraying, dry lamination, adhesives and the like. An exemplary method includes spin coating the resin formulation onto the device surface 24 of the substrate 14 by use of a solvent. A suitable solvent includes a solvent which is non-photoreactive. Non-photoreactive solvents include, but are not limited gamma-butyrolactone, C1-6 acetates, tetrahydrofuran, low molecular weight ketones, mixtures thereof and the like. An exemplary non-photoreactive solvent is acetophenone. The non-photoreactive solvent is present in the formulation mixture used to provide the thick film layer 46 in an amount ranging of from about 20 to about 90 weight percent, such as from about 40 to about 60 weight percent, based on the total weight of the photoresist formulation. In an exemplary embodiment of the present invention, the non-photoreactive solvent does not remain in the cured thick film layer 46 and is thus removed prior to or during the thick film layer 46 curing steps.
A method for imaging the thick film layer 46 will now be described with reference to
A radiation source provides actinic radiation indicated by arrows 62 to image the thick film layer 46. A suitable source of radiation emits actinic radiation at a wavelength within the ultraviolet and visible spectral regions. Exposure of the thick film layer 46 may be from less than about 1 second to 10 minutes or more, such as about 5 seconds to about one minute, depending upon the amounts of particular epoxy materials and aromatic complex salts being used in the formulation and depending upon the radiation source, distance from the radiation source, and the thickness of the thick film layer 46. The thick film layer 46 may optionally be exposed to electron beam irradiation instead of ultraviolet radiation.
The foregoing procedure is similar to a standard semiconductor lithographic process. The mask 56 is a clear, flat substrate (e.g., usually glass or quartz) with opaque areas 60 defining areas of the thick film layer 46 that are to be removed after development. The opaque areas 60 prevent the ultraviolet light from contacting the thick film layer 46 masked beneath it so that such areas remain soluble in a developer. The exposed areas of the layer 46 provided by the substantially transparent areas 58 of the mask 56 are reacted and therefore rendered insoluble in the developer. The solubilized material is removed leaving the imaged and developed thick film layer 46 on the device surface 24 of the substrate 14 as shown in
In a prior art process illustrated in
In order to reduce reflected radiation during the nozzle imaging step, a removable anti-reflective material, such as a patternable and removable anti-reflective material is applied to the device surface 24 of the substrate 14 and/or to the thick film layer 46 as shown in
Areas of the substrate surface 24 that might be covered by the anti-reflective layer 74 include the heater resistor 22, the fluid chamber 54, the fluid flow channel 52, and electrical contact pad areas (not shown). If the fluid supply slot 26 has not already been formed in the substrate 14, then before the anti-reflective material 74 is removed, the fluid supply slot 26 may be wet or dry etched or grit blasted through the substrate 14. In an alternative process, the anti-reflective layer 74 is also used as an etch resistant mask for dry etching the slot 26 through the substrate 14 using a deep reactive ion etching process.
Before the anti-reflective layer 74 is removed from the substrate 14, the nozzle layer 48 can be applied to the thick film layer 46 as shown in
Instead of applying the anti-reflective material to the substrate 14 after the thick film layer 46 has been applied to the substrate 14, the anti-reflective material may be applied to the device surface 24 of the substrate 14 before the thick film layer 46 is applied to the substrate 14. In that case, the anti-reflective material may be patterned to provide an anti-reflective layer 76 as shown in
In the foregoing embodiments, the anti-reflective layer 74 or 76 may be applied to the substrate 14 before or after the fluid supply slot 26 is formed in the substrate 14. Alternate embodiments of the disclosure are illustrated in
In one embodiment, illustrated in
Variations on the embodiment described with reference to
A further variation of the foregoing embodiments is illustrated in
In all of the foregoing embodiments, it will be appreciated that the anti-reflective material may be applied on a wafer level to the individual substrates 14 on the wafer 42. Accordingly, if the anti-reflective material is a water soluble material, the anti-reflective material may be removed during a washing step used to rinse the micro-fluid ejection heads 44 after dicing the wafer 42 into the individual micro-fluid ejection heads 44.
Having described various aspects and embodiments of the disclosure and several advantages thereof, it will be recognized by those of ordinary skills that the embodiments are susceptible to various modifications, substitutions and revisions within the spirit and scope of the appended claims.
