BACKGROUND

[0001] Printing devices contain a number of printheads used to dispense ink or another jettable fluid onto a print medium. The printheads include a number of dies that are precision dispensing devices that precisely dispense the jettable fluid to form an image on the print medium. The jettable fluid may be delivered via a fluid slot defined in the print head to an ejection chamber beneath a nozzle. Fluid may be ejected from the ejection chamber by, for example, heating a resistive element. The ejection chamber and resistive element form the thermal fluid ejection device of a thermal inkjet (TIJ) printhead. The printing devices may, however, use any type of digital, high precision liquid dispensing system, such as, for example, two-dimensional printing systems, three-dimensional printing systems, digital titration systems, and piezoelectric printing systems, among other types of printing devices.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] The accompanying drawings illustrate various examples of the principles described herein and are part of the specification. The illustrated examples are given merely for illustration, and do not limit the scope of the claims.

[0003] Fig. 1 is a block diagram of a printhead including collinear dies.

[0004] Fig. 2 is a block diagram of a curved printhead including dies that curve with respect to a surface of a print medium, according to an example of the principles described herein. [0005] Figs. 3, 4A - 4B, 5, 6, and 7A - 7B are a series of block diagrams of a method of manufacturing a fluid ejection device, according to an example of the principles described herein.

[0006] Fig. 8 is a block diagram of a mold for use in shaping a printhead, according to an example of the principles described herein.

[0007] Fig. 9 is a flowchart showing a method of manufacturing a fluid ejection device, according to an example of the principles described herein.

[0008] Fig. 10 is a flowchart showing a method of manufacturing a fluid ejection device, according to an example of the principles described herein.

[0009] Fig. 1 1 is a flowchart showing a method of manufacturing a fluid ejection device, according to an example of the principles described herein.

[0010] Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements. The figures are not necessarily to scale, and the size of some parts may be exaggerated to more clearly illustrate the example shown. Moreover, the drawings provide examples and/or implementations consistent with the description; however, the description is not limited to the examples and/or implementations provided in the drawings.

DETAILED DESCRIPTION

[0011] A print media path defines the path print media such as a web or paper takes during a printing process. During the printing process, a printing substance such as an ink or toner is deposited onto the print media. Within the print media path, the print media may be directed by a number of rollers that cause the print media to wrap around the rollers. The print media is eventually brought into printing interface with a printhead that dispenses the printing substance onto the print media. A roller may be included next to the printhead to direct the print media past the printhead.

[0012] The printhead may include a plurality of rows of printing dies that dispense the printing substance from the printhead. In some instances, the dies of the printhead may be collinear with one another. Fig. 1 is a block diagram of a printhead (100) including collinear fluid ejection dies (101-1 , 101-2, 101 -3, 101-4, collectively referred to herein as 101 ). Throughout the description, the terms“fluid ejection dies” and“dies” are used exchangeably to mean any device that ejects fluid from the printhead (100). The printhead (100) includes the dies (101 ) arranged collinearly with respect to one another. A roller (180) carries a print medium (150) such that the print medium (150) is placed next to the printhead (100) and its collinear dies (101 ). A gap (160) may exist between the print medium (150) and the roller (180). The gap (160) is created as the print medium (150) is pulled taunt across a top or crown of the roller (180) and is moved within a printing device via other rollers. In this manner, the radius of the curvature of the print medium (150) over the roller (180) may be greater than the radius of the roller (180) itself.

[0013] However, due to the curvature of the print medium (150) across the roller (180), the distances between the various dies (101 ) is different. For example, the distance D1 between dies (101 -2, 101-3) and the print medium (150) is different than the distance D2 between dies (101-1 , 101 -4) and the print medium (150). This difference in distances between the dies (101 ) and the print medium (150) may cause defects in the finished print when the dies (101 ) print a printing fluid onto the print medium (150). For example, dies (101-2, 101-3) may print in one manner onto the print medium (150), while the print substance dispensed by dies (101 -1 , 101-4) take more time to travel through the air between the dies (101-1 , 101-4) and the print medium (150).

[0014] Further, dies (101 -1 , 101-4) are angled differently with respect to a surface of the print medium (150) as compared to the angle at which dies (101 - 2, 101-3) are positioned relative to the surface of the print medium (150). These and other differences between dies (101 -1 , 101-4) and dies (101 -2, 101-3) and their positioning relative to the print medium (150) may cause blurring, stretching, distortions, or other print quality issues. Thus, a deviation of printhead (100) to print medium (150) spacing may be formed due to the collinear arrangement of the dies (101 ).

[0015] Examples described herein provide a method of manufacturing a fluid ejection device may include coupling a plurality of fluid ejection dies to an epoxy mold compound (EMC), partially curing the EMC, applying a force to the fluid ejection dies and EMC for a period of time, heating the fluid ejection dies and EMC for the period of time, and releasing the force when the EMC is cured. The completion of the curing causes the plurality of fluid ejection dies to be angled with respect to one another, the angle of the plurality of fluid ejection dies creating a curve in the fluid ejection device.

[0016] Coupling the plurality of fluid ejection dies to the EMC may include heating the EMC to a degree such that the EMC flows around the fluid ejection dies, the EMC overmolding the fluid ejection dies. A coefficient of thermal expansion (CTE) of the EMC causes the plurality of fluid ejection dies to be angled with respect to one another at the completion of the curing, the angle of the plurality of fluid ejection dies creating the curve in the fluid ejection device. Applying the force to the fluid ejection dies and EMC for a period of time comprises applying the force parallel to a longitudinal axis of the fluid ejection dies.

[0017] The method may include cooling the fluid ejection dies and EMC after the heating, the heating and cooling causing additional crosslinking of the fluid ejection device. The degree of curvature of the fluid ejection device is defined by a thickness of the fluid ejection dies, a coefficient of thermal expansion (CTE) of a material of the fluid ejection dies, a CTE of the EMC, the period of time the force is applied, the amount of force applied, the period of time the heat is applied, the amount of heat applied, or combinations thereof. Applying the force to the fluid ejection dies and EMC may include applying a force using a shaped object. The shaped object includes a curvature matching a radius of a print medium over a roller within a printing device.

[0018] Examples described herein provide a method of curving a fluid ejection device. The method may include applying a force to a partially-cured, EMC coupled to an array of fluid ejection dies for a period of time, heating the EMC and fluid ejection dies for the period of time, and cooling the EMC and fluid ejection dies. The application of the force to the EMC and fluid ejection dies, the heating of the EMC and fluid ejection dies, and the cooling of the EMC and fluid ejection dies complete the curing of the EMC. [0019] The combination of the CTE of the fluid ejection dies and the CTE of the EMC causes the plurality of fluid ejection dies to be angled with respect to one another at the curing of the EMC and fluid ejection dies, the angle of the fluid ejection dies creating a curve in the curved fluid ejection device. Applying the force to the partially-cured, EMC and fluid ejection dies comprises applying a force using a shaped object, the shaped object comprising a curvature matching a radius of a print medium over a roller within a printing device.

Applying the force to the EMC and fluid ejection dies for a period of time comprises applying the force parallel to a longitudinal axis of the fluid ejection dies. The heating and cooling causes additional crosslinking of the fluid ejection device. The degree of curvature of the fluid ejection device is defined by a thickness of the fluid ejection dies, a coefficient of thermal expansion (CTE) of a material of the fluid ejection dies, a CTE of the EMC, the period of time the force is applied, the amount of force applied, the period of time the heat is applied, the amount of heat applied, or combinations thereof. The method may include forming ink feed channels in the EMC.

[0020] Examples described herein provide a fluid ejection device. The fluid ejection device includes a plurality of fluid ejection dies overmolded within a partially-cured epoxy mold compound (EMC), and a curve formed in the fluid ejection device. A completion of the curing causes the plurality of fluid ejection dies to be angled with respect to one another, the angle of the plurality of fluid ejection dies creating the curve in the fluid ejection device.

[0021] The curve formed in the fluid ejection device is formed through the application of a force to the fluid ejection device, a coefficient of thermal expansion (CTE) of the EMC, or combinations thereof during a curing of the EMC. The curve is formed in the fluid ejection device parallel to a longitudinal axis of the fluid ejection dies. The fluid ejection device may include ink feed channels defined in the EMC.

[0022] Turning again to the figures, Fig. 2 is a block diagram of a curved printhead (200) including dies (201-1 , 201-2, 201-3, 201 -4, collectively referred to herein as 201 ) that curve with respect to a surface of a print medium (150), according to an example of the principles described herein. In the examples described herein, the dies (201 ) may eject different substances such as, for example, different colors of printable fluid such as cyan (C), magenta (M), yellow (Y), and black (B).

[0023] In order to ensure that each of the dies (201 ) are equidistant from the print medium (150) as opposed to collinear as depicted in Fig. 1 , the printhead (200) may include a curved form factor that matches a radius of the print medium (150) created by the roller (180) and the movement of the print medium (150) over the roller (180). In the examples described herein, the curved printhead (200) may be formed through application of a force during and after a curing process, reliance on coefficients of thermal expansion (CTE) of materials within the printhead (200), and combinations of these parameters. As to the application of force during and after a curing process, a force may be applied to the printhead (200) within, for example, an oven or other curing system and that force may be maintained after the heat form the curing system is removed (e.g., when the printhead (200) is removed from the oven.

[0024] As to the reliance on coefficients of thermal expansion (CTE) of materials within the printhead (200), in one example, at least one layer of EMC (210) with a CTE different than the dies (201 ) or a plurality of layers of EMC (210) with different CTEs with respect to one another and the dies (201 ) may be included in the printhead (200) in order to create the curve within the printhead (200). When the CTE of the dies (201 ) and the at least one EMC layer (210) are different or when the CTE of the plurality of EMC layers (210) includes one relatively higher CTE material and one relatively lower CTE material, the surface of the printhead (200) will form a concave shape from the side of the printhead (200) on which the dies (201 ) are located. The material of the dies (201 ) and the material of the EMC layer(s) (210) may be tuned or selected to create the curve of the printhead (200) such that the curve matches the curvature of the print medium (150) around the roller (160).

[0025] In Fig. 2, element 210 indicates an overmold of the dies (201 ), and may include at least one, and in some examples, a plurality of layers of a resin such as an epoxy mold compound (EMC). By overmolding the dies (201 ), the dies (201 ) may be made smaller resulting in less cost in manufacturing the printhead (200) by eliminating large amounts of relatively more expensive materials such as silicon from which the dies (201 ) are made. Thus, the use of sliver dies (201 ) along with the overmold material greatly decreases

manufacturing costs, and, in the examples described herein, are able to be modified to create a curvature in the printhead (200) that matches a curvature of a print medium (150) as curved over a roller (180).

[0026] In the examples described herein, the dies (201 ) may be positioned within the EMC layer(s) at a 1 ,524 micrometer (pm) pitch. Further the dies (201 ) may be embedded in 500 pm thick EMC layer(s). In an example, the dies (201 ) may be sliver dies. A sliver die may include a thin silicon, glass, or other substrate having a thickness on the order of approximately 650 pm or less, and a ratio of length to width (L/W) of at least three.

[0027] In examples where the printhead (200) includes a single layer of EMC (210), the CTE of the single layer of EMC (210), the CTE of the dies (201 ), the thickness of a layer of the dies (201 ) such as a silicon layer of the dies (201 ), a thickness of the single layer of EMC (210), and combinations thereof may determine whether the printhead (200) has a concave, flat, or convex curvature, and may determine the degree of curvature of the printhead (200). In examples where the printhead (200) includes two layers of EMC (210), the CTE of the first layer and second layer of the EMC (210), the CTE of the dies (201 ), the order or sequence at which the two layers of EMC (210) are positioned with respect to the dies (201 ), the thickness of a layer of the dies (201 ) such as a silicon layer of the dies (201 ), a thickness of the first layer of EMC (210), a thickness of the second layer of EMC (210), and combinations thereof may determine whether the printhead (200) has a concave, flat, or convex curvature, and may determine the degree of curvature of the printhead (200).

[0028] In the examples described herein, the dies (201 ) may be formed from silicon (Si). In another example, the dies (201 ) may be formed from glass or other materials instead of or in combination with silicon. For example, the printheads (200) described herein may include some dies (201 ) formed from silicon and some dies formed from another material such as glass. Further, in still another example, the layers of EMC described herein may include other materials inserted therein that change the CTE of the layers in order to achieve a certain curvature of the printhead (200). Thus, the dies (201 ) may be made of different materials in order to adjust the CTE of a die layer within the printhead

(200) and influence the curvature of the cured printhead (200).

[0029] The curved printhead (200) may also include fluid feed channels (202-1 , 202-2, 202-3, 202-4, collectively referred to herein as 202) formed in the at least one layer of EMC. The fluid feed channels (202) serve to feed a printing fluid to the fluid ejection dies (201 ). In one example, the fluid feed channels (202) may be formed by removing the at least one layer of EMC (210) to form the fluid feed channels (202). Removal of the at least one layer of EMC (210) may include cutting, mechanical etching, chemical etching, or other material removal processes. In another example, the fluid feed channels (202) may be formed through a molding process where the non-ejection sides of the dies

(201 ) are interfaced with a protruding portion of a mold.

[0030] In one example, the curvature of the printhead (200) may be formed by placing the layer(s) of EMC (210) and the dies (201 ) into a mold that is shaped to include a curve as depicted in Fig. 8. In this example, the mold cavity with its curved surfaces may be used to shape the printhead (200) alone or in combination with the layers(s) of EMC (210) with their respective CTEs.

The type of molding processes used in connection with this example of molding may include, for example, compression molding, transfer molding, injection molding, or combinations thereof.

[0031] The arrangement of the dies (201 ) and the process used to form the curved printhead (200) causes the plurality of fluid ejection dies (201 ) to be non-planar with respect to one another at curing of the at least one layer of EMC (210). The non-planar arrangement of the plurality of fluid ejection dies (201 ) creates a curve in the curved printhead device (200). More details regarding single and double layers of EMC (210) within the printhead (200) and the process by which the printhead (200) in these two examples are formed are provided herein in connection with Figs. 3 through 5B and 6 through 8B, respectively. [0032] Figs. 3 through 7B are a series of block diagrams of a method of manufacturing a fluid ejection device, according to an example of the principles described herein. Specifically, Figs. 3 through 7B depict the method of manufacturing the printhead (300) using at least one layer of EMC (301 ) and relying on the CTE of the dies (201 ) and the single layer of EMC (301 ) to form a curve in the printhead (300).

[0033] Beginning at Fig. 3, a number of dies (201 ) are adhered to a temporary substrate (310) via an adhesive layer (31 1 ). The temporary substrate (310) and adhesive layer (31 1 ) are used to correctly position and align the dies (201 ) with respect to one another. A reservoir of EMC material may be placed in a receptacle (305). In the example of Figs. 3 through 7B, the at least one layer of EMC material (305) may have a CTE that is relatively higher than the CTE of the dies (201 ). In this situation, the CTE difference will cause the printhead (300) and its dies (201 ) to form a concave curvature suitable to curve around the print medium (150) as the print medium (150) is moved by the roller (180).

[0034] The dies (201 ) are then brought into contact with the at least one layer of EMC (301 ) as depicted by arrow 303, and the EMC (301 ) is allowed to cure. “Curing” as used herein in the context of polymer chemistry and process engineering refers to the toughening or hardening of a polymer material by cross-linking of polymer chains, brought about by electron beams, heat, or chemical additives. The viscosity of, for example, the EMC drops initially upon the application of electron beams, heat, or chemical additives, passes through a region of maximum flow and begins to increase as the chemical reactions increase the average length and the degree of cross-linking between the constituent oligomers. This process continues until a continuous 3-dimensional network of oligomer chains is created that is referred to as gelation. In terms of processability of the EMC, before gelation the EMC may be relatively mobile, and after gelation the mobility is limited. At this point, the micro-structure of the EMC. Thus, in order to achieve vitrification in the EMC, the process

temperature may be increased after gelation. [0035] A partially cured EMC layer (301 ) is depicted in Fig. 4A where the dies (201 ) are overmolded with the at least one EMC layer (301 ) and the temporary substrate (310) is adhered to the dies (201 ) and the EMC layer (301 ) via an adhesive layer (31 1 ). In Fig. 4B, the adhesive layer (31 1 ) and temporary substrate (310) are removed. The orientation of the dies (201 ) and the at least one EMC layer (301 ) is flipped about the horizontal axis between Figs. 4A and 4B.

[0036] In Fig. 5, printhead (300) is placed within an oven (501 ) on a pair of shims (502-1 , 502-2). A force is applied to the printhead (300) as indicated by arrows (503). The force causes the partially-cured EMC layer (301 ) to bend such that the bottom side of the printhead (300) moves past the shims (502-1 , 502-2). Thus, the shims (502-1 , 502-2) serve to allow for an area to be created under the printhead (300) into which a portion of the printhead (300) may be forced into to form the curve (320). In one example, the heat provided by the oven (501 ) may be between approximately 175 °C to 180 °C and the duration at which the printhead (300) is exposed to the heat from the oven may be approximately 40 min. Further, in one example, the force applied to the printhead (300) may be approximately 4.2 kilograms (kg) distributed about the surface of the printhead (300) that includes the dies (201 ).

[0037] The force is applied to the printhead (300) is applied parallel to a longitudinal axis of the fluid ejection dies (201 ). Thus, as depicted in Fig. 5, the dies (201 ) may extend into an out of the page parallel with one another, and the extension of the dies in this direction is referred to herein as the longitudinal axis of the dies (201 ). In this manner, the dies (201 ) run a length of the printhead (300), and the curve (300) in the printhead (300) is formed by the application of the force (503) parallel to the dies (201 ) and the length of the printhead (300).

[0038] In Fig. 6, the printhead (300) is removed from the oven (501 ) and allowed to cool. In one example, the force (503) is continually applied to the printhead (300) after being removed from the oven (501 ) in order to ensure that the EMC layer (301 ) does not return to an angle previous to being placed in the oven (501 ) or return to a different degree of curvature. For this reason, the shims (502-1 , 502-2) are also removed from the oven (501 ) along with the printhead (300) so that the curvature (302) may be maintained. The printhead (300) is allowed to cool to an ambient temperature. The force (503) may be removed from the printhead (300) once the printhead (300) has cooled. The heating and cooling of the printhead (300) causes additional crosslinking of the EMC layer (301 ) of the printhead (300) such that the printhead (300) retains its shape and the curve (320) formed therein.

[0039] In one example, the force (503) applied to the printhead (300) while in the oven (501 ) and afterwards when cooling down may be applied by a shaped object. The shaped object may include a curvature that matches the desired curvature (320) of the printhead (300) and/or matches a radius of the print medium (150) created by the roller (180) and the movement of the print medium (150) over the roller (180). In one example, the mold (800) of Fig. 8 or a similar device may be used as the shaped object. In one example, the shaped object may have a mass that is large enough to apply the 4.2 kg force (503) to the printhead during and after the curing of the printhead (300).

[0040] At Fig. 7A, the orientation of the dies (201 ) and the at least one EMC layer (301 ) is flipped about the horizontal axis with respect to Fig. 6, and at Fig. 7B fluid feed channels (202) may be formed in the at least one layer of EMC. The fluid feed channels (202) serve to feed a printing fluid to the fluid ejection dies (201 ). In one example, the fluid feed channels (202) may be formed by removing portions of the at least one layer of EMC (301 ) to form the fluid feed channels (202). Removal of the portions of the at least one layer of EMC (301 ) may include cutting, mechanical etching, chemical etching, or other material removal processes. In another example, the fluid feed channels (202) may be formed through a molding process where the non-ejection sides of the dies (201 ) are interfaced with a protruding portion of a mold.

[0041] Fig. 8 is a block diagram of a mold (800) for use in shaping a printhead (200, 300), according to an example of the principles described herein. As mentioned herein, the curvature of the printhead (200, 300) may be formed by placing the at least one layer of EMC (210, 301 ) and the dies (201 ) into the mold (800) that is shaped to include a curve (320-1 , 320-2) as depicted in Fig. 8. Two halves (801 , 802) of the mold (800) each include the curve (320- 1 , 320-2) that matches the curvature of the print medium (150) created by the roller (180) and the movement of the print medium (150) over the roller (180). In this example, the mold cavity (803) with the curved surfaces (320-1 , 320-2) may be used to shape the printhead (200, 300) alone or in combination with the at least one layers of EMC (210, 301 ) with their respective CTEs. The type of molding processes used in connection with this example of molding may include, for example, compression molding, transfer molding, injection molding, or combinations thereof. In one example, the two halves (801 , 802) of the mold (800) may include a matching curved shape (320-1 , 320-2) to create the curved printhead surface. In another example, the two curved surfaces (320-1 , 320-2) may be different to create different radii of curvature on the two sides of the printhead (200, 300).

[0042] Fig. 9 is a flowchart showing a method (900) of manufacturing a fluid ejection device (200, 300) (i.e. , printhead), according to an example of the principles described herein. The method (900) may include coupling (block 901 ) a plurality of fluid ejection dies (201 ) to an EMC (210, 301 ). In one example, the coupling (block 901 ) of the dies (201 ) to the EMC (210, 301 ) may include overmolding the dies (201 ) with the EMC (210, 301 ). In one example, coupling (block 901 ) the plurality of fluid ejection dies (201 ) to the EMC (210, 301 ) may include heating the EMC (210, 301 ) to a degree such that the EMC (210, 301 ) flows around the fluid ejection dies (201 ). The EMC (210, 301 ) overmoldes the fluid ejection dies (201) in this manner.

[0043] The EMC (210, 301 ) may be partially cured (block 902), and a force (503) may be applied (block 903) to the dies (201 ) and EMC (210, 301 ) of the printhead (200, 300) for a period of time. Application (block 903) of the force (503) to the fluid ejection dies (201 ) and EMC (210, 301 ) for the period of time may include applying the force parallel to a longitudinal axis of the fluid ejection dies (201 ).

[0044] Further, applying (block 903) the force (503) to the fluid ejection dies (201 ) and EMC (210, 301 ) may include applying the force using a shaped object such as, for example the mold (800) or portions thereof, or a similar device that includes the desired curvature (320). The shaped object includes the curvature (320) that matches a radius of a print medium (150) over a roller (180) within a printing device.

[0045] The method (900) may also include heating (block 904) the fluid ejection dies (201 ) and EMC (210, 301 ) for the period of time, and completing (block 905) the curing of the EMC (210, 301 ) by releasing (block 905) the force (503) when the EMC (210, 301 ) is cured. The completion of the curing causes the plurality of fluid ejection dies (201 ) to be angled with respect to one another within the EMC (210, 301 ). The angle of the plurality of fluid ejection dies (201 ) creates a curve (320) in the fluid ejection device (200, 300).

[0046] In one example, the coefficient of thermal expansion (CTE) of the EMC (210, 301 ) may be used to cause the plurality of fluid ejection dies (201 ) to be angled with respect to one another at the completion of the curing where the angle of the plurality of fluid ejection dies (201 ) creates the curve in the fluid ejection device. In another example, the CTEs of the materials within the printhead (200, 300) may be used in concert with the force (503) applied to the printhead (200, 300) during the formation processes described herein. The heating and cooling of the printhead (200, 300) causes additional crosslinking of the EMC (210, 301 ) of the fluid ejection device (200, 300).

[0047] Fig. 10 is a flowchart showing a method (1000) of manufacturing a fluid ejection device (200, 300), according to an example of the principles described herein. The method (1000) may include applying (block 1001 ) a force (503) to a partially-cured, EMC (210, 301 ) coupled to an array of fluid ejection dies (201 ) for a period of time, and heating (block (1002) the EMC (210, 301 ) and fluid ejection dies (201 ) for the period of time

[0048] The EMC (210, 301 ) and fluid ejection dies (201 ) may be cooled (block 1003). The application (block 1001 ) of the force (503) to the EMC (210, 301 ) and fluid ejection dies (201 ), the heating (block 1002) of the EMC (210,

301 ) and fluid ejection dies (201 ), and the cooling (block 1003) of the EMC (210, 301 ) and fluid ejection dies (201 ) completes the curing of the EMC (201 , 301 ).

In one example, the combination of the CTE of the fluid ejection dies (201 ) and the CTE of the EMC (210, 301 ) may be used to cause the plurality of fluid ejection dies (201 ) to be angled with respect to one another at the curing of the EMC (210, 301 ) and fluid ejection dies (201 ). The angle of the fluid ejection dies (201 ) creates the curve (320) in the curved fluid ejection device (200, 300).

[0049] Fig. 1 1 is a flowchart showing a method (1 100) of manufacturing a fluid ejection device (200, 300), according to an example of the principles described herein. The method (1 100) may include coupling (block 1 101 ) a plurality of fluid ejection dies (201 ) to an EMC (210, 301 ). In one example, the coupling (block 1 101 ) of the dies (201 ) to the EMC (210, 301 ) may include overmolding the dies (201 ) with the EMC (210, 301 ). The EMC (210, 301 ) may be partially cured (block 1 102) to allow for some level of manipulation of the EMC (210, 301 ) during the method (1 100).

[0050] A force (503) may be applied (block 1 103) to the dies (201 ) and EMC (210, 301 ) of the printhead (200, 300) for a period of time. Application (block 1 103) of the force (503) to the fluid ejection dies (201 ) and EMC (210,

301 ) for the period of time may include applying the force parallel to a longitudinal axis of the fluid ejection dies (201 ). Further, applying (block 903) the force (503) to the fluid ejection dies (201 ) and EMC (210, 301 ) may include applying the force using a shaped object such as, for example the mold (800) or portions thereof, or a similar device that includes the desired curvature (320). The shaped object includes the curvature (320) that matches a radius of a print medium (150) over a roller (180) within a printing device.

[0051] The method (1 100) may also include heating (block 1 104) the fluid ejection dies (201 ) and EMC (210, 301 ) for the period of time, and releasing (block 905) the force (503) when the EMC (210, 301 ) is cured. The releasing (block 1 105) of the force (503) may be performed when the heat has been removed and the fluid ejection device (200, 300) is allowed to return to an ambient temperature. In other words, the force (503) is continually applied to the printhead (200, 300) during the heating and cooling processes to ensure that the curvature (320) is maintained until the EMC (210, 301 ) of the printhead (200, 300) is completely cross-linked. The heating and cooling causes the plurality of fluid ejection dies (201 ) to be angled with respect to one another within the EMC (210, 301 ). The angle of the plurality of fluid ejection dies (201 ) creates a curve (320) in the fluid ejection device (200, 300). [0052] The method (1 100) may also include forming (block 1 106) ink feed channels (202) in the EMC (210, 301 ). The fluid feed channels (202) serve to feed a printing fluid to the fluid ejection dies (201 ). In one example, the fluid feed channels (202) may be formed by removing the at least one layer of EMC (210) to form the fluid feed channels (202). Removal of the at least one layer of EMC (210) may include cutting, mechanical etching, chemical etching, or other material removal processes. In another example, the fluid feed channels (202) may be formed through a molding process where the non-ejection sides of the dies (201 ) are interfaced with a protruding portion of a mold.

[0053] The specification and figures describe a method of manufacturing a fluid ejection device. The method may include coupling a plurality of fluid ejection dies to an epoxy mold compound (EMC), partially curing the EMC, applying a force to the fluid ejection dies and EMC for a period of time, heating the fluid ejection dies and EMC for the period of time, and releasing the force when the EMC is cured. The completion of the curing causes the plurality of fluid ejection dies to be angled with respect to one another, the angle of the plurality of fluid ejection dies creating a curve in the fluid ejection device.

[0054] The systems and methods described herein provide a curved printhead that matches the radius of a print medium moved within a printing device over a roller. Since the overmolded dies are much narrower than other dies, it is much easier to integrate the dies in a curved and insert molded printhead. This curved printhead assists in minimizing the deviation of head-to- paper spacing and increase the usable print zone. As a result, the print quality is increased and print defects are minimized or eliminated. Further, a curved printhead provides tighter head to paper spacing control and a wider print zone, and reduces costs through a simplified paper path.

[0055] The preceding description has been presented to illustrate and describe examples of the principles described. This description is not intended to be exhaustive or to limit these principles to any precise form disclosed. Many modifications and variations are possible in light of the above teaching.