# Patent

## Title
Injection molded mounting substrate

## Abstract

The present invention relates to a fluid ejection assembly that includes an injection-molded mounting substrate that is formed by a two-shot injection molding process, wherein a housing portion of the mounting substrate is formed by a first shot molding, and a die-attach portion of the mounting substrate is formed within the housing portion by a second shot molding.

## Background
FIELD OF THE INVENTION
The present invention relates to a fluid ejection assembly that includes a mounting substrate for a fluid ejection device. The mounting substrate is made by utilizing two separate molding steps in a two-shot molding process that enables a housing portion of the mounting substrate to have increased strength and a die-attach portion of the mounting substrate to have fluid feed slots with small widths and spacings.
BACKGROUND OF THE INVENTION
A mounting substrate for a fluid ejection device, such as an inkjet printhead, has conventionally been made by a single molding process which forms both the die-attach portion for the fluid ejection device(s), including the fluid feed channels or slots with lands there-between, and a housing portion including alignment and fastening features, such as bolt holes. The mounting substrate should be sufficiently strong that it does not deform during fabrication of the mounting substrate, during attaching of the fluid ejection device(s), during attaching of the mounting substrate to a printhead chassis, or during printhead operation. If the fluid ejection device(s) to be attached to die-attach portion have multiple fluid inlets that are spaced apart by about 2 millimeters or more center-to center, use of a single molding process provides satisfactory results. Such multiple fluid inlets can, for example, be for providing different colored inks (e.g. cyan, magenta, yellow and black) to an inkjet printhead die having separate arrays of drop ejectors that are fed independently by the fluid inlets.
One significant way to reduce the cost of an inkjet printhead is to reduce the size of the fluid ejection device, i.e. the printhead die, which typically includes not only the fluid inlets and the arrays of drop ejectors, but also includes logic and switching electronics, as well as electrical interconnections. Due to advances in microelectronic fabrication processes, making the electronics on the die fit within a smaller space is now possible, so that the fluid inlets on the printhead die can be spaced as close together as 0.8 mm center-to-center or closer. The problem that remains is providing a mounting substrate having a die-attach portion with fluid feed slots at the same spacing as the fluid inlet spacing on the printhead die.
It is difficult to make fluid feed slots at a center-to-center spacing of less than one millimeter in a single injection molding process step and still provide sufficient strength in the mounting substrate. This is because for precision single-step injection molding processes, all wall thicknesses need to be substantially uniform. For example, for a center-to-center fluid feed slot spacing of 0.8 mm, the width of the slots and the widths of the lands between the slots can each be about 0.4 mm. This means that all walls that are injection molded in the same step should have approximately the same wall thickness as the lands, i.e. about 0.4 mm. It is found that such thin wall thickness does not provide a sufficiently strong, flat and stable mounting substrate.
Alternatively, if the walls or other features in the rest of mounting substrate were made substantially thicker than the lands between the slots, the molding material would not flow in a uniform manner to fill both the thick walls and the thin lands. As a result, the die-attach surface can warp, so that it is insufficiently flat to allow the printhead die to be adhesively attached with reliable fluid seals between adjacent fluid feed slots. In addition, there can be “knit lines” resulting from molding material flowing from both ends of the fluid feed slot and land region and meeting midway down the lands. Such knit lines are built-in discontinuities and stress concentrations which can lead to deformation and failure in the part.
Commonly assigned US Published Application No. 2008/0149024 (incorporated herein) discloses a printhead substrate arrangement in which the portion of the substrate that includes the fluid feed slots or channels is made from a ceramic material, while the remaining portion of the substrate arrangement is made by insert molding, i.e. by molding plastic material around the ceramic portion. This arrangement provides for a mounting surface that is flat and stable.
It is desirable to have a printhead substrate (i.e. a mounting substrate to which one or more printhead die can be attached) which costs less to produce. Additionally, it is further beneficial to have a printhead substrate where the widths of the fluid feed slots and the lands between the fluid feed slots are reduced to enable the overall reduction in the size of the corresponding printhead die to be attached. Ceramic is higher in cost than plastic. With ceramic, it is further difficult to provide for desired reduced center-to-center spacing of fluid feed slots, which enable the size the printhead substrate to be reduced. Accordingly, providing a low cost printhead substrate that includes reduced size fluid feed slots and lands. there-between when using ceramic is difficult.
SUMMARY OF THE INVENTION
The present invention relates to a fluid ejection assembly that includes an injection-molded mounting substrate that is formed by a two-shot injection-molding process, wherein a housing portion of the mounting substrate is formed by a first shot of the two-shot molding process, and a fluid passageway portion of the mounting substrate is formed within the housing portion by a second shot of the two-shot molding process. In a feature of the present invention, the two-shot injection-molded mounting substrate of the present invention provides an attachment surface for a fluid ejection device at a surface of the fluid passageway portion that is formed by the second shot. In a further feature of the present invention, with the two-shot molding process it is possible to reduce the width of the fluid feed slots and the lands between the fluid feed slots of the fluid passageway portion of the mounting substrate so as to enable the attachment of a reduced size fluid ejection device. The present invention further relates to a method of manufacturing the fluid ejection assembly and a method for manufacturing the mounting substrate for the fluid ejection assembly.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic representation of an inkjet printer system;
FIG. 2 is a perspective view of a portion of a printhead chassis;
FIG. 3 is a schematic view of a printhead die;
FIG. 4 is a perspective top view of a mounting substrate according to an embodiment of the present invention;
FIG. 5 is a perspective top view of the housing portion of the mounting substrate shown in FIG. 4;
FIG. 6 is a cross-sectional view of the mounting substrate shown in FIG. 4;
FIG. 7 is a perspective view of the die-attach portion of the mounting substrate shown in FIG. 4;
FIG. 8 is a cross-sectional view of the mounting substrate shown in FIG. 4;
FIG. 9 is a schematic top view of the die-attach portion of the mounting substrate shown in FIG. 4;
FIG. 10 is a perspective bottom view of the mounting substrate shown in FIG. 4;
FIG. 11 is a cross-sectional view of the mounting substrate shown in FIG. 4 and two printhead die attached to it; and
FIG. 12 is a perspective top view of the mounting substrate shown in FIG. 4 and two printhead die attached to it.



DETAILED DESCRIPTION OF THE INVENTION
The present description will be directed in particular to elements forming part of, or cooperating more directly with, apparatus in accordance with the present invention. It is to be understood that elements not specifically shown or described may take various forms well known to those skilled in the art.
Referring to FIG. 1, a schematic representation of an inkjet printer system 10 is shown, for its usefulness with the present invention and is fully described in U.S. Pat. No. 7,350,902, and is incorporated by reference herein in its entirety. Inkjet printer system 10 includes an image data source 12, which provides data signals that are interpreted by a controller 14 as being commands to eject drops. Controller 14 includes an image processing unit 15 for rendering images for printing, and outputs signals to an electrical pulse source 16 of electrical energy pulses that are inputted to an inkjet printhead 100, which includes at least one inkjet printhead die 110.
In the example shown in FIG. 1, there are two nozzle arrays. Nozzles or drop ejectors 121 in first nozzle array 120 have a larger opening area than nozzles or drop ejectors 131 in second nozzle array 130. In this example, each of the two nozzle arrays (120, 130) has two staggered rows of nozzles, each row having a nozzle density of 600 per inch. The effective nozzle density then in each array is 1200 per inch. If pixels on the recording medium 20 were sequentially numbered along the paper advance direction, the nozzles from one row of an array would print the odd numbered pixels, while the nozzles from the other row of the array would print the even numbered pixels.
In fluid communication with each nozzle array is a corresponding ink delivery pathway. Ink delivery pathway 122 is in fluid communication with the first nozzle array 120, and ink delivery pathway 132 is in fluid communication with the second nozzle array 130. Portions of fluid delivery pathways 122 and 132 are shown in FIG. 1 as fluid inlets 123 and 133 respectively through printhead die substrate 111. One or more inkjet printhead die 110 will be included in inkjet printhead 100, but for greater clarity only one inkjet printhead die 110 is shown in FIG. 1. The printhead die are arranged on a support member as discussed below relative to FIG. 2. In FIG. 1, first fluid source 18 supplies ink to first nozzle array 120 via ink delivery pathway 122, and second fluid source 19 supplies ink to second nozzle array 130 via ink delivery pathway 132. Although distinct fluid sources 18 and 19 are shown, in some applications it may be beneficial to have a single fluid source supplying ink to nozzles in the first nozzle array 120 and the second nozzle array 130 via ink delivery pathways 122 and 132 respectively. Also, in some embodiments, fewer than two or more than two nozzle arrays may be included on printhead die 110. In some embodiments, all nozzles on inkjet printhead die 110 may be the same size, rather than having multiple sized nozzles on inkjet printhead die 110.
Not shown in FIG. 1, are the drop forming mechanisms associated with the nozzles. Drop forming mechanisms can be of a variety of types, some of which include a heating element to vaporize a portion of ink and thereby cause ejection of a droplet, or a piezoelectric transducer to constrict the volume of a fluid chamber and thereby cause ejection, or an actuator which is made to move (for example, by heating a bi-layer element) and thereby cause ejection. In any case, electrical pulses from electrical pulse source 16 are sent to the various drop ejectors according to the desired deposition pattern. In the example of FIG. 1, droplets 181 ejected from the first nozzle array 120 are larger than droplets 182 ejected from the second nozzle array 130, due to the larger nozzle opening area. Typically other aspects of the drop forming mechanisms (not shown) associated respectively with nozzle arrays 120 and 130 are also sized differently in order to optimize the drop ejection process for the different sized drops. The term drop ejector is sometimes used to refer to the drop forming mechanism plus the nozzle.
An array of drop ejectors has a corresponding array of nozzles, and sometimes herein drop ejector arrays will be interchangeably referred to as nozzle arrays. During operation, droplets of ink are ejected by the drop ejector arrays and deposited on a recording medium 20.
FIG. 2 (similar to FIG. 9 of US Published Application No. 2008/0149024) shows a perspective view of a portion of a printhead chassis 250, which is an example of an inkjet printhead 100. Printhead chassis 250 includes three printhead die 251 (similar to printhead die 110), each printhead die 251 containing two nozzle arrays 253, so that printhead chassis 250 contains six nozzle arrays 253 altogether. The six nozzle arrays 253 in this example may be each connected to separate ink sources (not shown in FIG. 2); such as cyan, magenta, yellow, text black, photo black, and a colorless protective printing fluid. Each of the six nozzle arrays 253 is disposed along nozzle array direction 254.
The three printhead die 251 are shown in FIG. 2 as being attached to die-attach portion 230 of mounting substrate 220. The printhead die 251 are attached to die-attach portion 230 using an adhesive (not shown) that individually seals the fluid inlets (shown as 123 and 133 in FIG. 1) to corresponding fluid feed slots (not shown in FIG. 2) in die-attach portion 230, so that inks or other fluids from fluid sources 18 and 19 are separately fed and are not mixed together. Extending outwardly from die-attach portion 230 of mounting substrate 220 is housing portion 222. Housing portion 222 includes holes for bolts 225 for attaching mounting substrate 220 to printhead chassis 250. Housing portion 222 also includes alignment features 224, with respect to which printhead die 251 are placed on the die-attach portion 230. Alignment features 224 are also used to locate the printhead chassis against datum reference features in a carriage of a printer (not shown).
Also shown in FIG. 2 is a flex circuit 257 to which the printhead die 251 are electrically interconnected, for example, by wire bonding or tape automated bonding. The interconnections are covered by an encapsulant 256 to protect them. Flex circuit 257 is supported by the die-attach portion 230, bends around the side of printhead chassis 250 and connects to connector board 258. When printhead chassis 250 is mounted into the printer carriage (not shown), connector board 258 is electrically connected to a connector (not shown), so that electrical signals may be transmitted to the printhead die 251.
In commonly assigned U.S. Published Application No. 2008/0149024, the die-attach portion 230 (i.e. second portion 16 in the terminology of U.S. Published Application No. 2008/0149024) is made, for example, of a ceramic material that is insert molded into housing portion 220 (i.e. first portion 14 in U.S. Published Application No. 2008/0149024). Such an insert molded ceramic piece works well if the nozzle arrays 253 of printhead die 251 and their corresponding fluid inlets are spaced apart by a center-to-center distance of about one millimeter or more. However, using presently available ceramic fabrication technology, it is difficult to provide fluid feed slots at a center-to-center spacing of less than one millimeter.
FIG. 3 schematically shows a printhead die 252 that has four fluid inlets (also interchangeably referred to herein as ink inlet slots) 123, 133, 143 and 153 corresponding to first, second, third and fourth drop ejector arrays (not shown) respectively. Drop ejector arrays and associated logic and switching electronics are located between the fluid inlets, as well as beyond the outside fluid inlets 123 and 153. Compact design and fabrication of the electronics on printhead die 252 allows the center-to-center spacing “s” between adjacent fluid inlets to be less than one millimeter, for example 0.8 mm.
FIG. 4 shows a perspective view of a mounting substrate 220 according to an embodiment of the present invention. Mounting substrate 220 includes a housing portion 222 that extends outwardly from die-attach portion 230. Housing portion 222 includes alignment features 224 and bolt hole(s) 226, and is generally similar to the housing portion 222 shown in FIG. 2, except near die-attach portion 230. Housing portion 222 includes a first housing surface 228 (the top surface in the top view of FIG. 4) and a second housing surface 227 (the bottom surface that is hidden from view in FIG. 4). Die-attach portion 230 includes a first set of fluid feed slots 231 and a second set of fluid feed slots 232 in order to accommodate two printhead die 252 of the type shown in FIG. 3. Each set of fluid feed slots 232 and 233 has four fluid feed slots spaced at the same center-to-center spacing “s” as in printhead die 252 of FIG. 3, for example 0.8 mm. First and second sets of fluid feed slots 231 and 232 are the openings of fluid passageways (described below) at the die-attach surface 239 of die-attach portion 230. When printhead die 251 are subsequently mounted on mounting substrate 220, it is the die-attach surface 239 that the printhead die 251 are bonded to.
Mounting substrate 220 shown in FIG. 4 is made, for example, in a two-shot injection molding process. As is well known in the art of two-shot injection molding, a first molten material (e.g. a plastic resin) is injected through a first gate or first set of gates into a first cavity of a mold tool where the first cavity has the inverse shape of the features of the part to be made in the first shot. Then the part made in the first shot is moved to face a second cavity and a second molten material is injected through a second gate into the second cavity during the second shot step of the process to form or “overmold” the details corresponding to the second cavity onto the part made in the first shot step of the process.
In the first shot step of the two-shot injection molding process of mounting substrate 220, the housing portion 222 shown in FIG. 5 is made including the housing portion features described above relative to FIG. 4, as well as a recess 240 which is located in the region where die-attach portion 230 (not shown in FIG. 5) will be formed. Within recess 240 is an injection hole 243 and two subdivided indentations 241 and 242, corresponding respectively to the eventual positions of the first set of fluid feed slots 231 and the second set of fluid feed slots 232 shown in FIG. 4. The subdivided indentations 241 and 242 are each subdivided into four portions that merge into an elongated opening near the top surface of recess 240 (as viewed in FIG. 5), and lead to four separate holes 244, not all of which are visible in FIG. 5, and three of which are labeled within subdivided indentation 242 for clarity. There are no precision features in housing portion 222 having extensive thin walls, so housing portion 222 can be made with wall and feature thicknesses on the order of one to two millimeters.
In the second shot step of the two-shot injection molding process a molten material (e.g. a plastic resin) is injected through injection hole 243 from second housing surface 227 along injection direction 245 into recess 240 of housing portion 222 to form die-attach portion 230. The molten material flows into the recess 240 and into the two subdivided indentations 241 and 242. Blades and/or pins (not shown) within the second cavity of the mold tool limit the flow of the molten material within the two subdivided indentations 241 and 242 in order to form fluid passageways that exit the top surface of die-attach portion 230 as sets of fluid feed slots 231 and 232, as shown in FIG. 4. In some embodiments the mold tool is configured such that the resulting die-attach surface 239 of the die-attach portion 230 is substantially coplanar with the adjacent first housing surface 228 of the housing portion 222 (FIG. 4).
FIG. 6 shows a cross-section of mounting substrate 220, with the cut line of the cross-section being along dashed line 6A-6A shown in FIG. 4. Because the die-attach portion 230 is made during a second shot within the recess 240 and the subdivided indentations 241 and 242, the fluid passageway portions 233 that exit the die-attach surface 239 of die-attach portion 230 as first and second sets of fluid feed slots 231 and 232 can be made with thin walls without compromising the strength of mounting substrate 220. Fluid passageway portions 233 exit the bottom side surface 227 of housing portion 222 at ink feed holes 234 that are located within holes 244 in the subdivided indentations 241 and 242 (with reference to FIG. 5). Because holes 244 and ink feed holes 234 are spaced along the length of first and second sets of fluid feed slots 231 and 232, the cross-sectional view of FIG. 6 only exposes three of the holes 244 and corresponding ink feed holes 234, not all of which are labeled for improved clarity in FIG. 6.
FIG. 7 shows a view of die-attach portion 230 as if housing portion 222 were invisible. Because die-attach portion 230 is molded as a second shot within housing portion 222, die-attach portion 230 never exists separately from housing portion 222, but the view of FIG. 7 further clarifies additional details. First set of fluid feed slots 231 includes a first fluid feed slot 236a and a second fluid feed slot 236b, which is adjacent to first fluid feed slot 236a. Fluid feed slots 236a and 236b are the exit portions of first passageway 235a and second passageway 235b respectively at the surface of die-attach portion 230. First passageway 235a and second passageway 235b taper along the length dimension L of the set of fluid slots 231, and lead to ink feed holes 234a and 234b respectively at a second surface 229 of die attach portion 230.
Projection 238 from die-attach portion 230 is a result of injecting molten material in the second shot along injection direction 245 into injection hole 243 through a gate in the second cavity of the mold tool, and, as a result, projection 238 fills injection hole 243. (See FIG. 5 and also FIG. 8, which is a cross-sectional along dashed line 8A-8A of FIG. 4.) Preferably there is a single gate through which the second-shot molten material is injected into the second cavity to form die-attach portion 230, and preferably that gate (corresponding to injection hole 243 and projection 238) is near a first end 237 of fluid passageway portion(s) 233. In this way, the molten material flows along the single direction shown by the arrow indicated by length dimension L. Alternatively, if there are gates at both first end 237 and second end 247 (opposite first end 237) of the fluid passageway portion(s) 233, injected molten material would flow from both directions and form an undesirable knit line midway down the length of the lands between adjacent slots in the first and second sets of fluid feed slots 231 and 232. In some embodiments injecting the molten material through injection hole 243 from the bottom side surface 227 is advantageous because it results in a flatter surface on the die-attach surface of die-attach portion 230.
In the examples shown in FIGS. 4, 5 and 7, the width of the die-attach portion 230 is tapered near the first end 237 of fluid passageway portion(s) 233, i.e. near injection hole 243. Such a shape can be advantageous for improving the flow of molten material during the second shot mold step.
FIG. 9 shows a schematic top view of die-attach portion 230. First set of fluid feed slots 231 includes first fluid feed slot 235a, second fluid feed slot 235b, third fluid feed slot 235c and fourth fluid feed slot 235d, all extending along a length direction L. First fluid feed slot 235a has a slot width w1 and adjacent second fluid feed slot 235b has a slot width w2. The land (or first wall) between first fluid feed slot 235a and second fluid feed slot 235b has a wall width W1. A second land (or second wall) that is adjacent to second fluid feed slot 235b is opposite to the first wall and has a wall width W2. In some embodiments, all of the slot widths are equal (i.e. w1=w2, etc.), and in some embodiments, all of the wall widths are equal (i.e. W1=W2, etc.). In still other embodiments, each of the slot widths are equal to each of the wall widths (i.e. w1=w2=W1=W2, etc.). In general the slot widths and wall widths are designed to have good fluid flow through the fluid feed slots, and good adhesive sealing on the lands (or walls) between the fluid feed slots at the surface of die-attach portion 230, when the printhead die 252 is (are) attached to prevent fluid from leaking from one slot to another slot. In some embodiments, the slot widths are not exactly equal to the wall widths, but slot width w1 is greater than 80% of wall width W1 and less than 120% of wall width W1, for example. In some embodiments, the wall widths are not all exactly equal to each other, but wall width W1 is greater than 80% of wall width W2 and less than 120% of wall width W2, for example. The slot width and wall width dimensions also need to be designed to correspond to the center-to-center spacing “s” of the ink inlet slots (e.g. fluid inlets 123, 133, 143 and 153 of printhead die 252 with reference to FIG. 3).
Two-shot molding of mounting substrate 220 is particularly advantageous relative to other alternatives, when the center-to-center spacing of the ink inlet slots on the corresponding printhead die 252 to be attached to die-attach portion 230 is less than or equal to one millimeter. In apportioning the space on die-attach portion 230, it is advantageous if a slot width w1 of a first fluid feed slot 235a and a slot width w2 of a second fluid feed slot 235b are such that w1+w2 is less than one millimeter. It is further advantageous if (including the wall width W1 of the wall between the first fluid feed slot 235a and the second fluid feed slot 235b), W1+w1+w2 is less than 1.5 millimeter. Two-shot molding of mounting substrate 220 is not limited to center-to-center slot spacings between 0.8 and 1.0 mm, but can be used for center-to-center slot spacings as small as 0.4 mm.
In the examples shown in FIGS. 4, 6, 7 and 9, between the first set of fluid feed slots 231 and the second set of fluid feed slots 232 is a land area that can be larger than the wall widths, such as W1, between adjacent fluid feed slots within a set of fluid feed slots. This land area between sets of fluid feed slots allows for a space to be between two printhead die 252 that will be attached to die-attach surface 239 of die-attach portion 230. However, in other embodiments where adjacent printhead die 252 are designed to be attached without a space between them, the land area between sets 231 and 232 of fluid feed slots can be substantially the same as a wall width, such as W1.
FIG. 10 shows a bottom view of mounting substrate 220. Bottom side surface 227 of housing portion 222 is opposite the top surface of die-attach portion 230. Referring also to FIG. 7, first passageway 235a terminates at ink feed hole 234a and second passageway 235b terminates at ink feed hole 234b at second surface 229 of die-attach portion 230 near bottom side surface 227 of housing portion 222. Ink feed hole 234b is displaced from ink feed hole 234a along slot length direction L, and the other ink feed holes are similarly displaced from ink feed holes corresponding to adjacent passageways. Displacement of the ink feed holes makes it easier to reliably connect adjacent passageways to different fluid sources (not shown).
FIG. 11 shows an enlarged cross-sectional view of mounting substrate 220 similar to FIG. 6, but also including two printhead die 252a and 252b that are attached to die-attach portion 230. Note that fluid inlets 123, 133, 143 and 153 for first, second, third and fourth drop ejector arrays on printhead die 252a are respectively aligned with first, second, third and fourth fluid feed slots 235a, 235b, 235c and 235d in die-attach portion 230.
FIG. 12 shows a perspective view of a fluid ejection assembly including two fluid ejection devices (i.e. printhead die 252a and 252b) attached to die-attach portion 230 of mounting substrate 220, according to an embodiment of this invention. The eight independent drop ejector arrays corresponding to the four fluid inlets on each of the two printhead die can be configured in a variety of ways. In some embodiments, the four drop ejector arrays on printhead die 252a eject cyan, magenta, yellow and black ink, and the four drop ejector arrays on printhead die 252b also eject cyan, magenta, yellow and black ink, and provide additional nozzles for forming the same sorts of spots on the recording medium as printhead die 252a. In other embodiments, some of the drop ejector arrays eject different sized drops, so that the eight drop ejector arrays provide both larger spots and smaller spots of cyan, magenta, yellow and black ink, for example. In other embodiments, some of the drop ejector arrays eject different color densities having the same hue, so that the eight drop ejector arrays provide light magenta, dark magenta, light cyan, dark cyan, black, gray, yellow, and protective fluid, for example. In other embodiments, additional color inks such as orange and green are among the eight inks that can be ejected, in order to extend the gamut of colors that can be printed. In still other embodiments, only one printhead die 252 is mounted on a die-attach portion 230 correspondingly having a total of only four fluid feed slots. In yet other embodiments, printhead die 252a and 252b include only three drop ejector arrays each, and the six inks that can be ejected include cyan, magenta, yellow, text black, photo black, and protective fluid.
In the embodiments described above, fluid feed slots 236 were configured as continuous long, narrow openings. However, it is also contemplated that the fluid feed slots could alternatively include ribs that extend across the width of the slot, in order to improve strength and stability, for example.
In the embodiments described above, the fluid feed slots 236 for providing different fluids were arranged parallel to one another. Some printhead die are configured with two or more drop ejector arrays for different color inks in line with each other. It is also contemplated to provide a mounting substrate having a die-attach portion configured for such types of printhead die, in which a first set of two or more of the independent fluid feed slots are parallel to one another, and a second set of two or more of the independent fluid feed slots are in line with the fluid feed slots of the first set.
A variety of different materials can be used to make the housing portion 222 and the die-attach portion 230 in the two-shot injection molding process, including thermosetting or thermoplastic resins. Materials can be selected based on the resulting strength and stability of the overall mounting substrate 220, as well as flatness and moldability of the fine features of the die-attach portion 230. Printhead die are made of silicon in some embodiments, and the material of the die-attach portion 230 can be chosen to have a low thermal expansion coefficient in order to provide low stress when the printhead die 252 are adhesively attached. For example, the plastic resin of the die-attach portion can be glass filled (such as 30% glass filled Noryl). The materials chosen should also be chemically inert to ink components, resist stress cracking, have good mechanical strength, and have relatively low cost. Liquid crystal polymers are a good choice in some embodiments. The material used to form the die-attach portion 230 may be chosen to be the same material used to form the housing portion 222, or it may be a different material. Good adhesion between the material used to form the die-attach portion 230 and the material used to form the housing portion 222 is desirable. In the case of different materials being used for forming the die attach portion 230 and the housing portion 222, chemical properties of the two materials, as well as the respective melt temperatures of the two materials can be factors in selecting materials that are compatible with the manufacturing process and that adhere well to one another. In addition, the recess 240 and segmented indentation(s) 241 and/or 242 can include features such as surface roughness to improve the adhesion of the die-attach portion 230 to the housing portion 222.
Although two-shot molding is sufficient for making the mounting substrate of the present invention, it is also contemplated that a multi-shot molding process can be used having more than two shots. One of the shots would be used to form a housing portion, and another of the shots would be used to form a die-attach portion of the mounting substrate.
The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

## Claims

1. A fluid ejection device for ejecting a plurality of fluids, the fluid ejection device comprising:
a printhead die including a first array of drop ejectors with a corresponding first fluid inlet, and a second array of drop ejectors with a corresponding second fluid inlet that is adjacent to the first fluid inlet; and
an injection-molded mounting substrate for the fluid ejection device, wherein the injection-molded mounting substrate includes:
a housing portion including a recess and an indentation within the recess; and
a die-attach portion formed within the recess of the housing portion, the die-attach portion including:
a first passageway and a second passageway that are fluidly coupled to the first fluid inlet and the second fluid inlet, respectively, of the printhead die;
a first wall that conforms to a shape of the recess; and
a second wall that conforms to a shape of the indentation within the recess.

2. The fluid ejection assembly of claim 1, the housing portion including a first housing surface and the die-attach portion including a first die-attach surface that is substantially coplanar with the first housing surface.

3. The fluid ejection assembly of claim 2, wherein:
the first passageway comprises a first slot at the die-attach surface of the fluid passageway portion, the first slot extending along a first direction and including a first slot width w1; and
the second passageway comprises a second slot at the die-attach surface of the die-attach portion, the second slot extending along the first direction and including a second slot width w2, and wherein w1+w2<1 mm.

4. The fluid ejection assembly of claim 3, the die-attach portion further comprising a first wall disposed between the first slot opening and the second slot, the wall including a first wall width W1, wherein W1+wl+w2<1.5 mm.

5. The fluid ejection assembly of claim 4, wherein 0.8W1<w1<1.2W1.

6. The fluid ejection assembly of claim 4, the die-attach portion further comprising a second wall adjacent the second slot, the second wall being opposite the first wall and including a second wall width W2, wherein 0.8 W2<W1<1.2 W2.

7. The fluid ejection assembly of claim 3, the housing portion including a second housing surface that is opposite the first housing surface, and the die-attach portion including a second surface that is opposite the die-attach surface, wherein the first passageway further comprises a first hole at the second surface of die-attach portion and the second passageway further comprises a second hole at the second surface of the die-attach portion, and wherein the first hole is displaced from the second hole along the first direction.

8. A fluid ejection assembly for ejecting a plurality of fluids, the fluid ejection assembly comprising:
a fluid ejection device including a first array of drop ejectors with a corresponding first fluid inlet, and a second array of drop ejectors with a corresponding second fluid inlet that is adjacent to the first fluid inlet; and
an injection-molded mounting substrate for the fluid ejection device, wherein the injection-molded mounting substrate includes:
a housing portion including a recess, a first housing surface, and a second housing surface opposite the first housing surface, the housing portion having been formed by a first shot molding; and
a die-attach portion formed within the recess of the housing portion by a second shot molding, the die-attach portion including:
a die attach surface that is substantially coplanar with the first housing surface of the housing portion;
a second surface opposite the die attach surface;
a first passageway including a first slot extending along a first direction at the die-attach surface; and
a second passageway including a second slot extending along the first direction at the the-attach surface, the first and second passageway being fluidly coupled respectively to the first fluid inlet and the second fluid inlet of the fluid ejection device, wherein the first passageway further comprises a first hole at the second surface of die-attach portion and the second passageway further comprises a second hole at the second surface of the die-attach portion, and wherein the first hole is displaced from the second hole along the first direction.

9. The fluid ejection assembly of claim 1, wherein the housing portion includes an injection hole for the injection of material during the second shot molding.

10. The fluid ejection assembly of claim 9, the first passageway including a first end and a second end opposite the first end, and the second passageway including a first end that is proximate the first end of the first fluid passageway, wherein the injection hole is disposed proximate the first ends of the first and second fluid passageways.

11. The fluid ejection assembly of claim 1, wherein:
the housing portion is formed of a first material;
the die-attach portion is formed of a second material and
the die-attach portion is adhered to the housing portion by adhesion between the first material and the second material.

12. The fluid ejection assembly of claim 11, wherein the first material and the second material are plastic materials.

13. The fluid ejection assembly of claim 11, wherein the first material is the same as the second material.