FOR FLUID EJECTION DIE

BACKGROUND

[0001] Fluid ejection dies may be used to selectively eject droplets of fluid. Fluid ejection dies may be used in various applications such as for printing upon a medium or for three-dimensional printing. Power and control signals may be transmitted to the fluid ejection dies to control the ejection of the fluid droplets by the dies.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] Figure 1 is a sectional view schematically illustrating portions of an example fluid ejection apparatus.

[0003] Figure 2 is a flow diagram of an example method for forming an example fluid ejection apparatus.

[0004] Figure 3 is a flow diagram of an example fluid ejection method.

[0005] Figure 4 is a diagram schematically illustrating portions of an example fluid ejection system for carrying out the method of Figure 3.

[0006] Figure 5 is a block diagram schematically illustrating portions of example electrical transmission enhancement circuitry for the fluid ejection apparatus of Figure 1.

[0007] Figure 6 is a diagram schematically illustrating portions of an example fluid ejection system.

[0008] Figure 7 is an enlarged sectional view schematically illustrating portions of an example fluid ejection system. [0009] Figures 8A and 8B are a circuit diagram illustrating portions of an example electrical transmission enhancement circuitry of the example fluid ejection system of Figure 7.

[00010] Figure 9 is a circuit diagram illustrating portions of the electrical transmission enhancement circuitry of the example fluid ejection system of Figure 7.

[00011] Figure 10 is a circuit diagram illustrated portions of the example electrical transmission enhancement circuitry of the example fluid ejection system of Figure 7.

[00012] Figure 11 is a circuit diagram illustrating portions of the example electrical transmission enhancement circuitry of the example fluid ejection system of Figure 7.

[00013] Figure 12 is a perspective view illustrating portions of the example fluid ejection system of Figure 7.

[00014] Figure 13 is a perspective view illustrating portions of the example fluid ejection system of Figure 7.

[00015] Figure 14 is a perspective view illustrating portions of the example fluid ejection system of Figure 7.

[00016] Figure 15 is a perspective view illustrating portions of the example fluid ejection system of Figure 7.

[00017] Figure 16 is a perspective view illustrating portions of the example fluid ejection system of Figure 7.

[00018] 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 OF EXAMPLES

[00019] Disclosed are example fluid ejection apparatus and fluid ejection methods that may provide enhanced print quality with a lower cost and more compact arrangement of components. The example apparatus and methods may achieve enhanced print quality by providing a higher quality transmission of power and control signals (individually and collectively referred to as “electrical transmissions”) to fluid ejection dies.

[00020] Electrical power and electrical control signals are sometimes supplied from active firing circuitry that may be remote from the fluid ejection dies. During the transmission and distribution or routing of the electrical power and electrical control signals from the active firing circuitry to the fluid ejection dies, the power and signal transmissions may experience parasitic losses and voltage variations (voltage noise). Parasitic losses are a function of the electrical current being transmitted and the electrical resistance of the electrically conductive wire, trace or layer transmitting the power. Such parasitic losses may lead to voltage drops or voltage sagging.

[00021] Control signals, in the form of data and clock signals, are sometimes transmitted as low voltage differential signals (LVDS). Impedance variations in the transmission of such control signals may introduce voltage signal ringing or overdamping, reducing edge quality of the signals. Poor signal edge quality may result in poor signal integrity which may result in poor print quality.

[00022] The example fluid ejection apparatus and fluid ejection methods enhance signal integrity or quality by comprising or utilizing a physical construct that locates or supports electrical transmission enhancement circuitry in close proximity to the fluid ejection dies. In the examples illustrated, the electrical transmission enhancement circuitry is supported by a printed circuit assembly (PCA) that is itself supported in close proximity to the fluid ejection dies. In some implementations, the PCA is stacked over or on the fluid ejection dies to locate the electrical transmission enhancement circuitry closer to the fluid ejection dies. Because the electrical transmission enhancement circuitry is closer to the fluid ejection dies, the electrical transmission enhancement circuitry may more effectively condition, distribute and/or route electrical power and/or electrical control signals to provide enhanced signal integrity and enhanced print quality.

[00023] “Electrical transmission enhancement circuitry” refers to electronic circuitry that enhances the transmission of electrical power and/or electrical control signals. Enhancing the transmission of electrical power and/or electrical control signals may comprise reducing parasitic losses, and/or reducing voltage noise. The electrical transmission enhancement circuitry may reduce parasitic losses using storage capacitors. Parasitic losses experienced by a fluid ejection die decline the closer the storage capacitor is to the fluid ejection die. The example fluid ejection apparatus and fluid ejection methods may comprise or utilize a physical construct that locates storage capacitors in close proximity to the fluid ejection dies so as to reduce parasitic losses in the circuitry closest to the fluid ejection dies to enhance signal integrity and print quality.

[00024] The electrical transmission enhancement circuitry may reduce voltage noise using bypass capacitors. Bypass capacitors shunt high- frequency noise components of an electrical transmission to ground. In some implementations, such bypass capacitors may have a bypass capacitance of no greater than 0.1 pF. [00025] The length of the electrical conductor connecting a bypass capacitor to a fluid ejection die may function as an antenna, picking up high- frequency noise from surrounding electrical lines. The farther that a bypass capacitor is from a fluid ejection die, the greater the length of the antenna and the greater likelihood that the antenna will pick up additional voltage noise from surrounding electrical lines. If the bypass capacitor is not sufficiently close to the fluid ejection die, the antenna formed by the electrical conductor connecting the bypass capacitor to the fluid ejection die may be so long so as to render the bypass capacitor ineffective with respect to reducing voltage noise. The example fluid ejection apparatus and fluid ejection methods comprise or utilize a physical construct that locates bypass capacitors sufficiently close to the fluid ejection dies to reduce voltage noise and enhance print quality.

[00026] In some example implementations, the electrical transmission enhancement circuitry may comprise a switchable bypass capacitor on the peak-to-peak voltage (VPP) firing power supply line for noise immunity. The electrical transmission enhancement circuitry may comprise a bypass capacitor on an analog power supply for voltage noise reduction. The electrical transmission enhancement circuitry may comprise a Vdd storage capacitor and a bypass capacitor 381 on the Vdd digital power supply line for parasitic loss protection and voltage noise reduction, respectively. In some implementations, each end of each of the fluid ejection dies may comprise a Vdd storage capacitor and a bypass capacitor on the Vdd digital power supply line. The electrical transmission enhancement circuitry may comprise an LVDS impedance matching network. The electrical transmission enhancement circuitry may further comprise a switchable bypass capacitor on the VPP firing power supply line which allows the bypass capacitor to be switched out of circuit for leakage testing.

[00027] In some implementations, power and/or electrical control signals transmitted from the electrical transmission enhancement circuitry of the PCA to the fluid ejection die occur across electrically conductive lines, each having a length of no greater than 9 mm. In some implementations, the power and/or electrical control signals may be transmitted from the electrical transmission enhancement circuitry of the PCA to the fluid ejection die across electrically conductive lines, each line having a length of no greater than 4 mm. In some implementations, the close proximity of the PCA and its electrical transmission enhancement circuitry to the fluid ejection die is facilitated by stacking the PCA directly or indirectly upon the fluid ejection die. In some implementations, the close proximity of the PCA and its electrical transmission enhancement circuitry to the fluid ejection die is facilitated by wire bonding the electrical transmission enhancement circuitry of the PCA to the fluid ejection die through a via within the PCA. In some implementations, the close proximity of the PCA and its electrical transmission enhancement circuitry to the fluid ejection die is facilitated by delivering fluid for the die through an opening in the PCA.

[00028] The electrical transmission enhancement circuitry may reduce voltage noise by providing enhanced control over the impedance of the electrical transmission of control signals such as data and clock LVDS signals. The PCA, local to the fluid ejection dies, may comprise a multilayer printed circuit board comprising a stack of electrically conductive layers including ground layers, power layers and signal layers. The PCA may route such LVDS signals with signal layers, wherein each signal layer is sandwiched between and shielded by a pair of ground layers. This physical construct provides enhanced control over the impedance to provide enhanced emitting and immunity noise protection.

[00029] The electrical transmission enhancement circuitry may further reduce voltage noise by supporting a low voltage impedance matching network or multiple low voltage impedance matching networks directly on the PCA. The PCA provides sufficient real estate (surface area) for the provision of such a low voltage impedance matching network or multiple low voltage impedance matching networks in close proximity to the fluid ejection dies. A low voltage impedance matching network may assist in reducing noise, providing sharper clock signal edges, to enhance print quality.

[00030] In some implementations, the PCA, which is connected to the fluid ejection die and which comprises the electrical transmission enhancement circuitry, is connected to a flexible cable. The flexible cable extends from the PCA and is connected to an electrical interface board. The electrical interface board facilitates connection of the PCA to a remote firing system that controls the overall ejection of fluid by the die. The flexible cable spaces the electrical interface board from an aerosol field of the die. As a result, the electrical interface board may omit protective coatings or other protective measures from fluid exposure or corrosion. The stacking of the PCA behind and upon the fluid ejection die may further isolate the PCA and its connections from the aerosol field to further reduce reliance upon protective coatings or other protective measures. In some implementations, connectors of the PCA and/or connectors of electrical interface board that connect the PCA to the remote firing system face in a direction that is opposite to the direction in which fluid is ejected, further reducing potential aerosol contamination of such connections.

[00031] Disclosed is an example fluid ejection apparatus. The example fluid ejection apparatus may include fluid ejection dies, an interposer printed circuit board supporting the fluid ejection dies and electrically connected to the fluid ejection dies and a printed circuit assembly stacked upon the interposer printed circuit board. The printed circuit assembly may include electrical transmission enhancement circuitry.

[00032] Disclosed is an example fluid ejection method. The method may include supplying fluid to a fluid ejection die having a bond pad and transmitting electrical transmissions from a PCA to the bond pad of the fluid ejection die across an electrically conductive line have a length of no greater than 9 mm.

[00033] Disclosed is an example fluid ejection apparatus. The example fluid ejection apparatus may include fluid ejection dies, a printed circuit assembly electrically connected to the fluid ejection dies and comprising electrical transmission enhancement circuitry, a flexible cable electrically connected to and extending from the printed circuit assembly and an electrical interface board connected to the flexible cable.

[00034] Figure 1 is a diagram schematically illustrating portions of an example fluid ejection apparatus 20 for selectively ejecting drops of fluid onto a medium, such as a print medium or 3D printing media (build material). Fluid ejection apparatus 20 facilitates a higher quality transmission of power and control signals to fluid ejection dies with a more compact and lower-cost arrangement of components. Fluid ejection apparatus 20 comprises fluid ejection dies (FEDs) 24-1 - 24-n (collectively referred to as dies 24), interposer printed circuit board 28 (shown in cross-section) and printed circuit assembly (PCA) 32.

[00035] Fluid ejection dies 24 comprise individual devices that dispense fluid through openings or ejection orifices. Fluid ejection dies may include internal fluid passages or channels for delivering fluid to a fluid actuator which displaces the fluid through an ejection orifice to eject droplets of the fluid.

Such fluid ejection dies may include a silicon substrate supporting fluid actuators, electrically conductive traces and other electronic componentry associated with the fluid actuators. Such fluid ejection dies may further include a chamber or barrier layer which forms firing chambers or passages and associated ejection orifices. In some implementations, the chamber layer may be formed from a photo-imageable epoxy, such as SU8. In some implementations, each of the dies may be in the form of a sliver, wherein each die has a length to width ratio of 50 or more. [00036] Interposer printed circuit board 28 comprises a printed circuit board that supports the fluid ejection dies 24 and is electrically connected to the fluid ejection dies 24. Interposer printed circuit board 28 may include electrically conductive traces or may include electrically conductive layers connected to a bond pad for electrical connection to the PCA. In some implementations, fluid ejection dies 24 are received within apertures formed within interposer printed circuit board 28. In some implementations, fluid ejection dies 24 are further secured within and to interposer printed circuit board 28 by a molding, such as an epoxy mold compound, which encapsulates portions of the fluid ejection dies 24 and the interposer printed circuit board 28. In some implementations, interposer printed circuit board 28 supports fluid ejection dies 24 in parallel rows with the fluid ejection dies of the rows being staggered or offset relative to dies of an adjacent row.

[00037] As shown by Figure 1, each of fluid ejection dies 24 has an ejection face 30 and a rear face 31. In some implementations, rear face 31 is the rearward most surface with respect to interposer printed circuit board 28 and any molding. As a result, fluid ejection dies 24 may be located in closer proximity to PCA 32 and its electrical transmission enhancement (ETE) circuitry 50.

[00038] In some implementations, each rear face 31 is flush with a rear face 36 of interposer printed circuit board 28. In implementations where fluid ejection dies 24 are partially encapsulated by a molding, the molding may also be flush with the rear face 36 of the interposer printed circuit board 28 and the rear face 31 of the fluid ejection dies 24. In some implementations, interposer printed circuit board 28 may be recessed with respect to rear face 31 of fluid ejection dies 24, wherein the molding (overlying the rear of interposer printed circuit board 28) may form the rear face 36 that is flush with the rear face 31 of each fluid ejection dies 24. Because rear face 31 of each of fluid ejection dies 24 is the rearward most projecting surface with respect to the interposer printed circuit board 28 and/or any molding, fluid ejection dies 24 may be positioned in closer proximity to PCA 32 and its electrical transmission enhancement circuitry 50.

[00039] As shown by broken lines, in some implementations, interposer printed circuit board 28 may have a rear face 36’ that projects beyond rear face 31 of the fluid ejection dies 24, wherein each rear face 31 of each of fluid ejection dies 24 is recessed within a corresponding opening or window 40 in the interposer printed circuit board 28. In other implementations, rear face 31 may project beyond the rear face 36 of interposer printed circuit board 28. [00040] In some implementations, ejection face 30, the face through which fluid is ejected, is also flush with a front face 34 of interposer printed circuit board 28 or a molding partially encapsulating interposer printed circuit board 28. As shown by broken lines, in some implementations, interposer printed circuit board 28 (or a molding that partially encapsulates interposer print circuit board 28) may have a front face 34’ that projects beyond ejection face 30, wherein each ejection face 30 is recessed within a window 38 formed in interposer printed circuit board 28 and/or the molding partially encapsulating interposer printed circuit board 28. In other implementations, ejection face 30 may project beyond front face 34 of interposer print circuit board 28 or of the molding.

[00041] PCA 32 comprise a platform or structure, such as a printed circuit board, that supports electrical transmission enhancement (ETE) circuitry 50. ETE circuitry 50 enhances the transmission of electrical power and/or electrical control signals by reducing parasitic losses, and/or reducing voltage noise. The ETE circuitry 50 may reduce parasitic losses using storage capacitors. ETE circuitry 50 may reduce voltage noise using bypass capacitors.

[00042] In some implementations, power and/or electrical control signals transmitted from the ETE circuitry 50 of the PCA 32 to a fluid ejection die 24 occur across electrically conductive lines, each having a length of no greater than 9 mm. In some implementations, the power and/or electrical control signals may be transmitted from the ETE circuitry 50 of the PCA 32 to a fluid ejection die 24 across electrically conductive lines, each line having a length of no greater than 4 mm.

[00043] In some implementations, the ETE circuitry may reduce voltage noise by providing enhanced control over the impedance of the electrical transmission of control signals such as data and clock LVDS signals. The PCA 32, local to the fluid ejection dies 24, may comprise a multilayer printed circuit board comprising a stack of electrically conductive layers including ground layers, power layers and signal layers. The PCA 32 may route such LVDS signals with signal layers, wherein each signal layer is sandwiched between and shielded by a pair of ground layers. This physical construct of PCA 32, sometimes referred to as microstrip or strip line control, provides enhanced control over the impedance to provide enhanced emitting and immunity noise protection. In contrast to individual electrical conductors, traces or lines, the much larger area layers (each layer having a surface area coextensive with the majority if not 90% or more of the surface area of the printed circuit board itself) reduce parasitic losses. In one implementation, PCA 32 comprises a 10-layer printed circuit board supporting the electronic components that form the ETE circuitry 50.

[00044] The ETE circuitry 50 may comprise a low voltage impedance matching network or multiple low voltage impedance matching networks directly on the PCA. A low voltage impedance matching network may assist in reducing noise at high switching rates, such as switching rates greater than 90 MHz. Such matching networks may provide for enhanced impedance matching amongst fluid ejection dies at the point of delivery, reducing “ring” and providing sharper clock signal edges, to enhance print quality.

[00045] As indicated by arrows 53, PCA 32 with electrical transmission enhancement circuitry 50 is directly or indirectly stacked upon interposer printed circuit board 28 and/or fluid ejection dies 24. With “indirect” stacking, intervening films or layers may extend between PCA 32 and interposer printed circuit board 28 or fluid ejection dies 24. Such intervening films or layers may have a “de minimis” thickness, a thickness of less than 3 mm. In some implementations, PCA 32 may be directly mounted to the interposer printed circuit board 28 by an adhesive, wherein no other structures extend between PCA 32 and interposer printed circuit board 28 but for the adhesive and any air gaps. With “direct” stacking, PCA 32 is directly stacked upon and in contact with interposer print circuit board 28 and/or fluid ejection dies 24. For example, in those implementations in which rear face 36 of interposer printed certain board 28 is flush with rear face 31 of fluid ejection dies 24, PCA 32 may directly rest upon and in contact with rear face 36 and/or rear face 31.

[00046] The stacking of PCA 32 behind or on top of interposer printed circuit board 28 and fluid ejection dies 24 facilitates close proximity of the ETE circuitry 50 and fluid ejection dies 24. In implementations where the fluid ejection dies comprise bond pads, such stacking facilitates shorter electrical conductors connecting the bond pads of PCA 32 to the bond pads of the fluid ejection dies. In some implementations, such stacking may facilitate the use of electrical conductors between the bond pads of PCA 32 and the bond pads of the fluid ejection dies, wherein the electrical conductors have a length no greater than 9 mm. In some implementations, the length may be no greater than 4 mm. Direct stacking of PCA 32 on interposer printed certain board 28 and fluid ejection dies 24 may further reduce the length of such electrical conductors. Reducing the length of the electrical conductors may enhance the performance of ETE circuitry 50, as described above, potentially resulting in less electrical noise and more consistent performance.

[00047] Figure 2 is a flow diagram illustrating an example method 100 for forming an example fluid ejection apparatus, such as fluid ejection apparatus 20 described above. As indicated by block 104, an interposer printed circuit board, such as interposer printed certain board 28, that supports fluid ejection dies is provided. In some implementations, the provision of the interposer printed circuit board and the supported fluid ejection dies may involve positioning fluid ejection dies within apertures that extend through the interposer printed circuit board, electrically connecting the fluid ejection dies to bond pads provided on the interposer printed circuit board and partially encapsulating the fluid ejection dies and the interposer printed circuit board with a molding, such as epoxy mold compound.

[00048] As indicated by block 108, a printed circuit assembly, such as PCA 32, having electrical transmission enhancement circuitry, such as ETE circuitry 50, is stacked on the interposer printed circuit board. As described above, such stacking may be direct or indirect. In some implementations, such stacking may involve wire bonding bond pads on the interposer printed circuit board to bond pads on the PCA. Such stacking may involve aligning openings through the PCA with the bond pads on the interposer printed circuit board such that the electrical conductors may extend through the opening and through the PCA. Such stacking may further involve alignment of additional apertures in the PCA 32 with fluid passages of the fluid ejection dies such that fluid may be supplied to the fluid ejection dies through the PCA.

[00049] Figures 3 and 4 illustrate an example fluid ejection method 200. Figure 3 is a flow diagram of the example fluid ejection method 200. Figure 4 illustrates implementation of the method 200 with an example fluid ejection apparatus 220. Although method 200 is described in the context of being carried out with apparatus 220, it should be appreciated that method 200 may likewise be carried out with apparatus 20 described above, with any of the systems described hereafter or with similar fluid ejection apparatus. Method 200 may be carried out where a PCA 32 is supported relative to a fluid ejection die in any manner that facilitates close proximity of PCA 32 and its ETE circuitry 50 relative to the fluid ejection die.

[00050] As indicated by block 204 in Figure 3 and shown by Figure 4, fluid supply 222 supplies fluid (F) to a fluid ejection die 24 that has a bond pad 226 for receiving control signals. As indicated by block 208 in Figure 3 and shown by Figure 4, PCA 32, supporting ETE circuitry 50 (shown in Figure 1), transmits electrical transmissions 33 to the bond pad 226 of the fluid ejection die 24 across an electrical conductor 56. Electrical transmissions 33 may be in the form of electrical power or control signals. The electrical conductor 56 has a length L that is no greater than 7 mm. In some implementations, the length L is no greater than 4 mm. In implementations where wire bonding is used, the length L may be measured as extending from bond pad 226 to a bond pad of PCA 32. The short length L may reduce electrical noise by reducing the antennae length (as described above) and reduce parasitic losses near the fluid ejection dies.

[00051] Figure 5 is a block diagram schematically illustrating portions of an example fluid ejection device ETE circuitry 350, one example of electrical transmission enhancement circuitry 50 which may be utilized in apparatus 20, 220 or any of the following described fluid ejection apparatus. ETE circuitry 350 is supported by a PCA, such PCA 32, and enhances the quality of the transmission of power and control signals to fluid ejection dies. ETE circuitry 350 comprises VPPLOGIC line 370, bypass capacitor 372, analog power supply line 374, bypass capacitor 376, storage capacitor 377, Vdd digital power supply line 378, storage capacitor 380, bypass capacitor 381 , VPP firing power supply line 382, bypass capacitor 384, transistor 385 and low- voltage differential signaling (LVDS) impedance matching network 386. Each of the capacitors 372, 376, 377 380, 381 , 384, transistor 385 and electronic components of the LVDS matching network 386 are supported by PCA 32. In some implementations, each of such electronic components may be supported on an external surface of PCA 32. The close proximity of such electronic components to the fluid ejection die 24 facilitates enhanced signal integrity for enhanced print quality.

[00052] VPPLOGIC line 370 comprises an electrically conductive line on PCA 32 that facilitates voltage regulation. Storage capacitor 372 is electrically connected to VPPLOGIC line 370 on PCA 32. Bypass capacitor 372 shunts high-frequency noise components of an electrical transmission to ground to reduce voltage noise.

[00053] Analog power supply line 374 comprises an electrically conductive line on PCA 32 that supplies power to a fluid ejection die, such as fluid ejection die 24. Bypass capacitor 376 is electrically connected to the analog power supply line 374 on PCA 32. Bypass capacitor 376 shunts high- frequency noise components of electrical transmission to ground to reduce voltage noise. Storage capacitor 377 serves as a local power source for the fluid ejection dies 24.

[00054] Vdd digital power supply line 378 comprises an electrically conductive line on PCA 32 that supplies a digital voltage for the control of the fluid ejection die. Storage capacitor 380 is electrically connected to the Vdd digital power supply line 378 on the PCA 32. Bypass capacitor 381 is electrically enacted to Vdd digital power supply line 378 in parallel with storage capacitor 380. Capacitors 380 and 381 provide parasitic loss and noise protection, respectively. In some implementations, capacitors 380 and 381 are provided by PCA 32 at each end of fluid ejection die 24. Storage capacitors 380 reduce voltage sag at each end of each die. The multiple bypass capacitors 381 provided for each fluid ejection die provide enhanced noise protection.

[00055] VPP firing power supply line 382 comprises an electrically conductive line on PCA 32 that supplies the firing voltage for the fluid ejection die. Bypass capacitor 384 is selectively electrically connected to the VPP firing power supply line on the PCA 32 by transistor 385. The switchable bypass capacitance provided by capacitor 384 and transistor 385 facilitates the switching out of bypass capacitor 384 out of the circuit for leakage testing.

[00056] LVDS impedance matching network 386 comprises an electronic circuit formed on PCA 32 that matches the impedance as between pairs of fluid ejection dies for enhanced clock edge signaling. In some implementations, LVDS impedance matching network 386 may be omitted.

[00057] Figure 6 is a diagram schematically illustrating portions of an example fluid ejection apparatus 400 in the form of an example printhead device stack. Figure 6 illustrates an example of how connections with PCA 32 may be made so as to reduce complexity and cost of the fluid ejection apparatus 400. As shown by Figure 6, fluid ejection dies 24 are connected to PCA 32 which includes the ETE circuitry 50. In some implementations, PCA 32 is stacked on fluid ejection dies 24 as described above to provide close proximity of ETE circuitry 50 include ejection dies 24. In some implementations, PCA 32 may be supported relative to fluid ejection dies 24 in other fashions. ETE circuitry 50 provides a higher quality transmission of power and control signals to fluid ejection dies 24.

[00058] As further shown by Figure 6, fluid ejection apparatus 400 further comprises flexible cable 460 and electrical interface board 462.

Flexible cable 460 is electrically connected to and extends from a back side of PCA 32. In some implementations, PCA 32 is sandwiched between fluid ejection dies 24 and flexible cable 460 with fluid ejection dies 24 being located on a front side of PCA 32 and flexible cable 460 extending from a rear side of PCA 32. As a result, flexible cable 460 and its connection to PCA 32 is spaced from and blocked from any aerosol field that may exist in the print zone adjacent the ejection faces 30 of the fluid ejection dies 24.

[00059] Electrical interface board 462 is electrically connected to flexible cable 460. Electrical interface board 462 is for an electrical connection to another printed circuit board supporting processors and other componentry that form the firing system for the printer utilizing fluid ejection apparatus 400. The firing system controls the overall operation of fluid ejection dies 24 to carry out a printing operation, such as printing a two-dimensional image on a print medium or depositing fluid as part of a 3D printing operation. In some implementations, electrical interface board 462 comprises a circuit board providing edge connectors for insertion into electrical connection slots.

[00060] Flexible cable 460 spaces electrical interface board 462 from the aerosol field of fluid ejection dies 24. In the example illustrated, the electrical connectors of electrical interface board 462 which connect to the larger firing system face in directions away from the aerosol field and away from the direction (indicated by arrows 431) in which fluid is being ejected by fluid ejection dies 24. As a result, such electrical connectors are further protected from contamination from the aerosol field. As a result, PCA 32 and the electrical connectors of PCA 32 and electrical interface board 462 are less susceptible to contamination from the aerosol field. In some implementations, this lower susceptibility to contamination from the aerosol field may allow such structures to omit coatings or other protective measures that would otherwise be used to protect against fluid exposure/corrosion.

[00061] Figure 7 is a sectional view schematically illustrating portions of an example fluid ejection system 500. System 500 comprises fluid supply 504, firing system 506 and fluid ejection apparatus 520. Fluid supply 504 supplies a fluid for being controllably ejected by fluid ejection apparatus 520.

In one implementation, fluid supply 504 may supply an ink for printing upon a two-dimensional printing medium. In another implementation, fluid supply 504 may supply a binder or other fluid to facilitate three-dimensional printing. In another implementation, fluid supply 504 may supply other forms of fluid depending upon the use of fluid ejection apparatus 520. In some implementations, fluid supply 504 may supply different types or kinds of fluid to different portions of a fluid ejection die or to different fluid ejection dies.

[00062] Firing system 506 comprises a processor and associated memory which contains instructions for directing the processor to output ejection control signals for controlling the ejection or firing of fluid droplets by fluid ejection apparatus 520. Power and control signals output by firing system 506 are conditioned, distributed and routed by PCA 532.

[00063] Fluid ejection apparatus 520 receives fluid from fluid supply 504 and ejects droplets of the fluid in accordance with instructions or control signals from firing system 506. Fluid ejection apparatus 520 may provide enhanced performance due to the close proximity of electrical transmission enhancement circuitry relative to the fluid ejection dies of apparatus 520.

Fluid ejection apparatus 520 may be less vulnerable to aerosol contamination. Fluid ejection apparatus 520 comprises fluid ejection dies 524 (one of which is schematically shown in Figure 7), interposer printed circuit board 528, electrical conductors 529, molding 530, PCA 532, cable connector 534, flexible cable 560, electrical interface board 562, pressure regulator 564 and housing 570.

[00064] Fluid ejection die 524 is similar to fluid ejection die 24 as described above. As schematically shown by Figure 7, each of fluid ejection dies 524 comprises substrate 600, bond pads 602 (one of which is shown), chamber layer 604, fluid supply passages 606, and an array of fluid ejectors 608-1 , 608-2, 608-3, 608-4 and so on (collectively referred to as fluid ejectors 608). Substrate 600 comprises a layer or a set of layers that support bond pads 602 and fluid actuators of ejector 608. In some implementations, substrate 600 comprises a layer of silicon. In other implementations, substrate 600 may comprise a layer or layers of other materials.

[00065] Bond pads 602 are formed upon and supported by substrate 600. Bond pads 602 comprise pads of electrically conductive material electrically connected to each of fluid ejectors 608 for transmitting power and control signals to ejectors 608. Bond pads 602 further facilitate electrical connection to interposer printed circuit board 528 using electrical conductors 529. [00066] Chamber layer 604 comprises a layer or multiple layers formed upon substrate 600 and forming chambers and ejection orifices of fluid ejectors 608. In some implementations, chamber layer 604 comprises a first layer forming ejection chambers and a second layer forming ejection orifices. In some implementations, chamber layer 604 is formed from a photo- imageable epoxy, such as SU8. In other implementations, chamber layer 604 may be formed from other materials.

[00067] Fluid supply passages 606 deliver fluid through substrate 600 and through chamber layer 604 to fluid ejectors 608. Fluid supply passages 606 may comprise slots, feed holes or a combination thereof. In some implementations, fluid supply passages 606 may additionally provide circulation or recirculation of fluid within substrate 600 or within chamber layer 604, across each of fluid ejectors 608.

[00068] Fluid ejectors 608 each comprise a fluid actuator 610, an ejection chamber 612 and an ejection orifice 614. Fluid actuator 610 comprises a device to displace fluid within the ejection chamber 612 through ejection orifices 614. Fluid actuator 610 is supported by substrate 600 generally opposite to or within an associated fluid ejection chamber 612. In one implementation, fluid actuator 610 may comprise a thermal resistor which, upon receiving electrical current, heats to a temperature above the nucleation temperature of the fluid so as to vaporize a portion of the adjacent fluid to create a bubble which displaces the fluid through the associated ejection orifice. In other implementations, the fluid actuator 610 may comprise other forms of fluid actuators. In other implementations, the fluid actuator 610 may comprise a fluid actuator in the form of a piezo-membrane based actuator, an electrostatic membrane actuator, mechanical/impact driven membrane actuator, a magnetostrictive drive actuator, an electrochemical actuator, and external laser actuators (that form a bubble through boiling with a laser beam), other such microdevices, or any combination thereof. [00069] Each ejection chamber 612 is formed within chamber layer 604. Fluid ejection orifices 14 extends from ejection chamber 612 through chamber layer 604 for ejecting drops through and from the front face or ejection face 630 of the fluid ejection die 524 in the directions indicated by arrows 616. In some implementations, ejection chamber 612 may include an inlet and outlet to facilitate circulation of fluid through the ejection chamber, between fluid actuator 610 and ejection orifice 614.

[00070] Interposer printed circuit board 528 is similar to interposer printed circuit board 28 described above. Interposer printed circuit board 528 comprises a printed circuit board that supports the fluid ejection dies 524 and is electrically connected to the fluid ejection dies 524. Interposer printed circuit board 528 has a front face 634 and a rear face 636. Front face 634 supports bond pads 638 which are electrically connected to electrical conductors 529. Rear face 636 supports bond pads 640 which are electrically connected to PCA 532 by electrical conductors 641. In the example illustrated, interposer printed circuit board 528 comprises openings 644 which receive fluid ejection dies 524. In some implementations, interposer printed circuit board 528 provides electrical connections between bond pads 638 and 640, omitting electronic components.

[00071] Molding 530 conforms to and encapsulates interposer printed circuit board 528 and fluid ejection die 524. Molding 530 further encapsulates electrical conductors 529 and their bond pads 602, 638. In some implementations, molding 530 comprises an epoxy mold compound. In other implementation, molding 530 may comprise other conformable materials that solidify after deposition.

[00072] PCA 532 is similar to PCA 32 (described above) except that PCA 532 is stacked upon interposer printed circuit board 528 and fluid ejection dies 524. PCA 532 and interposer printed circuit board 528 extend in parallel planes. In the example illustrated, die 524 and interposer printed circuit board 528 are coplanar. In the example illustrated, PCA 532 is adhesively bonded to interposer printed circuit board 528 by adhesive 645. PCA 532 comprises multilayer printed circuit board 650, bond pads 652, encapsulant 654, fluid ejection device electrical transmission enhancement circuitry 550 and electrical stitching lines 656.

[00073] Multilayer printed circuit board 650 comprises a stack of layers including ground layers, power layers and signal layers. In the example illustrated, signal layers are sandwiched between and shielded by ground layers for enhanced impedance control to reduce voltage noise. In one implementation, PCA 532 comprises a 10-layer printed circuit board. In contrast to individual electrical conductors, traces or lines, the much larger area layers (each layer having a surface area coextensive with the majority if not 90% or more of the surface area of the printed circuit board itself) reduce parasitic losses. Multilayer printed circuit board 650 comprises vias 670 and fluid delivery openings 672.

[00074] Vias 670 extend through PCA 532 from a front face 674 of PCA 532 to a rear face 676 of PCA 532. Vias 670 are aligned with bond pads 640 of interposer printed circuit board 528. Electrical conductors 641 extend from the rear face 636 of interposer printed circuit board 528 through vias 670 to bond pads 652 on rear face 676 of PCA 532. As a result, bond pads 638 are electrically connected to front faces of the fluid ejection dies 524 by the electrical conductors 529 and the bond pads 640 are electrically connected to a back face of the PCA 532 by electrical conductors 641 extending through the vias 670.

[00075] Encapsulant 654 fills vias 670, encapsulating electrical conductor 641 and encapsulating bond pads 640 and 652. In some implementations, encapsulant 654 may comprise the material also forming molding 530, such as an epoxy mold compound. In other implementations, encapsulant 654 may comprise other materials. In some implementations, vias 670 may be omitted, such as in implementations where electrical conductors 641 extend about an outer edge of PCA 532. [00076] Fluid delivery openings 672 extend through PCA 532 from front face 674 to rear face 676. Fluid delivery openings 672 are aligned with ports 607 of fluid supply passage 606 of substrate 600. Fluid delivery openings 672 facilitate delivery of fluid from fluid supply 504 to fluid supply passages 606 and ultimately to fluid ejector 608 for ejection. In other implementations, fluid delivery openings 672 may be omitted where fluid delivery to fluid supply passages 606 is about an outer edge of PCA 532.

[00077] ETE circuitry 550 is similar to ETE circuitry 50 described above. ETE circuitry 550 comprises electronic components that enhance the quality of electrical transmissions to fluid ejection die 524. Portions of ETE circuitry may condition and distribute power and control signals to reduce voltage noise and/or parasitic losses. Figure 7 schematically illustrates a portion of the transistors and capacitors supported by multilayer printed circuit board 650, transistor 385 and capacitors 376, 384. Figures 8-11 (described hereafter) illustrate example portions of the ETE circuitry 550. In the example illustrated, the various capacitors and transistors of electrical transmission enhancement circuitry 550 are mounted on rear face 676 of PCA 532 and are electrically connected to different electrically conductive layers of PCA 532 by stitching lines 656.

[00078] Electrical stitching lines 656 comprise electrically conductive vias extending from their associated electronic components to designated electrically conductive layers (power, signal or ground) of PCA 532.

[00079] Cable connector 534 is mounted on the back face 676 of PCA 532. Cable connector 534 facilitates connection of PCA 532 to flexible cable 560. In some implementations, cable connector 534 comprises a flat flex connector (FFC) having an opening or socket facing in a direction away from the direction of fluid ejection indicated by arrows 616. In some implementations, cable connector 534 comprises a zero insertion force (ZIF) FFC. [00080] Flexible cable 560 comprises a flat flexible cable that extends from and is connected to cable connector 534 and electrical interface board 562. Flexible cable 560 extends from the back side of PCA 532. Electric interface board 562 is similar to electrical interface board 462 described above. Electrical interface board 562 is for an electrical connection to firing system 506. In some implementations, electrical interface board 562 comprises a circuit board providing edge connectors for insertion into electrical connection slots.

[00081] Pressure regulators 564 comprise devices that regulate the pressure of the fluid F being supplied from fluid supply 504 to dies 524 through fluid passages and manifolds contained within housing 570. Pressure regulators 564 may prevent drooling and puddling to enhance the performance of fluid ejection apparatus 520. In some implementations, pressure regulators 564 may be omitted or may be remotely provided.

[00082] Housing 570 comprise structures that enclose the back side of PCA 532, cable connector 534, flexible cable 560, pressure regulators 564 and the various fluid passages and manifolds for delivering fluid from fluid supply 504 to the various fluid ejection dies 524. As shown by Figure 7, housing 570 partially encloses and supports electric interface board 562 such that a portion of electrical interface board 562 projects from a rear of housing 570. Housing 570 supports electrical interface board 562 such that the electrical connectors of electric interface board 562 face in a direction away from fluid ejection dies 524 and away from the directions indicated by arrows 616 at which fluid is ejected. Electrical interface board 562 projects through and extends from a back side of housing 570. As a result, electrical interface board 562 is less likely to become contaminated from aerosols that may produce during fluid ejection.

[00083] Figures 8-11 are circuit diagrams schematically illustrating examples of different portions of ETE circuitry 550. Because PCA 532 is stacked upon interposer printed circuit board 528 and fluid ejection dies 524, PCA 532 offers a sufficiently large surface area for mounting the multiple electronic components that form ETE circuitry 550. The larger surface areas of the different layers of PCA 532 provide a great area for power and signal routing, reducing parasitic loss. In addition, such stacking allows such electronic components to be sufficiently close to fluid ejection dies 524 to further enhance performance.

[00084] Figures 8A, 8B and 9 illustrate an example of cable connector 534 and its various connection location/pins with their respective functional assignments designating what power and control signals are to be transmitted at the respective connection locations from firing system 506. Figure 8A illustrates the electrical connections at a first end of individual fluid ejection die 524 while Figure 9 illustrates electrical connections at the second opposite end of the same fluid ejection die 524. As shown by Figures 8A and 9, at each end of each individual fluid ejection die 524 supported by interposer printed circuit board 528, PCA 532 supports a storage capacitor 380 and a bypass capacitor 381 connected to the Vdd digital power supply line 378 for enhanced parasitic loss and noise protection. For each of the fluid ejection dies 524 supported by interposer printed circuit board 528, PCA 532 further supports bypass capacitor 372 electrically connected to the VPPLOGIC line. PCA 532 further supports a bypass capacitor 376 (shown in Figure 8A and a storage capacitor 377 (shown in Figure 8B) connected to the analog power supply line 374 (V5A).

[00085] Figure 10 illustrates an example LVDS impedance matching network 386 supported on PCA 532 and provided for each pair of fluid ejection dies 524. As noted above, LVDS matching network 386 may be omitted. In some implementations, LVD’s matching network 336 may be omitted in implementations where die internal termination resistors are used. [00086] Figure 11 illustrates an example electronic circuit forming a switchable bypass capacitance on the VPP firing power supply line for noise immunity. Such switching is performed using transistor 660 and bypass capacitor 384 which are supported on PCA 532. Such switching allows for close to die capacitance to be switched out of circuit to facilitate leakage testing.

[00087] Figures 12-16 provide larger, more overall views of the example fluid ejection system 500. Figure 16 illustrates the assembled system 500. Figures 12-15 illustrate various parts of system 500 during its fabrication or assembly. Figure 12 illustrates a front side of interposer printed circuit board 528 and fluid ejection dies 524. Figure 12 illustrates the positioning of example fluid ejection dies 524 within opening 644 extending through the example interposer printed circuit board 528. Figure 12 further illustrates electrical conductors 529 (in the form of wires) bonded to and connecting bond pads 602 and bond pads 638.

[00088] Figure 13 illustrates the front side of fluid ejection dies 524 following the partial encapsulation of interposer printed circuit board 528 (shown in Figure 12) by molding 530. As shown by Figure 13, molding 530 encapsulates front face 634 of interposer printed circuit board 528, filling those portions of openings 644 that are not already occupied by fluid ejection dies 524. In the example illustrated, each of fluid ejection dies 524 is recessed by 200 urn from the molded front surface of molding 530. In other implementations, fluid ejection dies may have ejection faces 630 that are flush with the molded front surface of molding 530.

[00089] Figure 14 illustrates an ejection head stack 502 formed by the stacking of PCA 532 on interposer printed circuit board 528 and molding 530. Figure 14 illustrates a rear side of the over molded assembly of Figure 13 following the mounting of PCA 532 on interposer printed circuit board 528 by adhesive 645 or other mounting structures or materials. Figure 14 further illustrates the over molded assembly of Figure 13 following the bonding of electrical conductor 641 to and between bond pads 640 and 652 and the encapsulation of electrical conductors 641 and bond pads 640, 652 (shown in Figure 7) by encapsulant 654. As seen in Figure 14, PCA 532 supports various capacitors 372, 376, 380, 381 and 384 and transistors 385 of ETE circuitry 550.

[00090] In the example illustrated, PCA 532 comprises four elongate openings 672 that are coincident with fluid ejection dies 524. As described above, fluid to be ejected is delivered to dies 524 through opening 672. In the example illustrated, the openings 644 of interposer printed circuit board 528 (shown Figure 12) are arranged in parallel rows with the openings being staggered or offset relative to one another. Likewise, the fluid ejection dies 524 extend in parallel rows with the individual fluid ejection dies 524 being staggered offset relative to one another so as to overlap one another. Accordingly, openings 672 also extend in parallel rows with the individual holes being staggered or offset relative to one another such that openings 672 of different rows overlap one another. The offset or staggered relationship of the fluid ejection dies 524 facilitates more complete ejection or printing coverage along the length of the assembly. In other implementations, the assembly shown in Figure 14 may have other arrangements of fluid ejection dies 524 along with their respective openings 644 and openings 672.

[00091] Figure 15 illustrates a larger example ejection head stack 502 of system 500 formed by pair of fluid ejection apparatus 520. Fluid ejection apparatus 520 nest with respect to one another so as to overlap one another. Both of fluid ejection apparatus 520 are similar to one another. Figure 15 illustrates the front of fluid ejection apparatus 520 in an orientation facing upwards.

[00092] Figure 15 illustrates fluid ejection head stack 502 following the mounting of manifolds 700 to the rear face of PCA 532 (shown in Figure 14) and the connection of the electrical interface assemblies 702 to the cable connectors 534 (shown in Figure 14) of each of apparatus 520. Each of manifolds 700 include internal fluid passages for directing fluid to the individual dies 524.

[00093] Electrical interface assemblies 702 are formed by flat flexible cables 560 and electrical interface boards 562. Flat flexible cables 560 extend between and are connected to cable connectors 534 (shown in Figure 14) and electrical interface boards 562. That interface boards 562 include edge connectors 704 for being received within corresponding connector slots associated with firing system 506 (shown in Figure 7).

[00094] Figure 16 illustrates the addition of housing 570 and the pressure regulators 564 (shown in Figure 7). Housing 570 joins fluid ejection apparatus 520 to form a single larger ejection head. Housing 570 encloses pressure regulators 572. As discussed above, housing 570 partially encloses electrical interface boards 562 such that edge connectors 704 of such electrical interface boards 562 project away from and beyond housing 570 in a direction away from the direction which fluid is ejected by dies 524. Housing 570 spaces and blocks such edge connectors 704 from the aerosol field that may result during fluid ejection by dies 524.

[00095] Although many of the examples illustrate the PCA as supporting electrical transmission enhancement circuitry that comprises each of the above described storage capacitors, bypass capacitors and LVDS impedance matching networks, it should be appreciated that other implementations may comprise a PCA that supports other forms of electrical transmission enhancement circuitry. For example, in some implementations, the PCA that is stacked on the fluid ejection dies may comprise the above described storage capacitors while omitting the above-described bypass capacitors and/or the LVDS impedance matching network. In some implementations, the PCA that is stacked on the fluid ejection dies may comprise the above bypass capacitors while omitting the above described storage capacitors and/or the LVDS impedance matching network. In some implementations, the PCA that is stacked on the fluid ejection dies may comprise the above-described LVDS impedance matching network while omitting the above-described storage capacitors and/or bypass capacitors. Although the disclosed examples illustrate the PCA supporting a bypass capacitor for each of the analog power supply line, the VPP firing power supply line, the Vdd digital power supply line and the VPPLOGIC line for enhanced noise protection, in other implementations, some of the bypass capacitors may be omitted. Although the disclosed examples illustrate the PCA supporting storage capacitor for the Vdd digital power supply line for each die, at each end of each die, for enhanced parasitic loss protection, in other implementations, the PCA may omit a storage capacitor for some of the fluid ejection dies or may omit a storage capacitor at one end of the fluid ejection dies or at one end of some of the fluid ejection dies.

[00096] Although the present disclosure has been described with reference to example implementations, workers skilled in the art will recognize that changes may be made in form and detail without departing from the disclosure. For example, although different example implementations may have been described as including features providing various benefits, it is contemplated that the described features may be interchanged with one another or alternatively be combined with one another in the described example implementations or in other alternative implementations. Because the technology of the present disclosure is relatively complex, not all changes in the technology are foreseeable. The present disclosure described with reference to the example implementations and set forth in the following claims is manifestly intended to be as broad as possible. For example, unless specifically otherwise noted, the claims reciting a single particular element also encompass a plurality of such particular elements. The terms “first”, “second”, “third” and so on in the claims merely distinguish different elements and, unless otherwise stated, are not to be specifically associated with a particular order or particular numbering of elements in the disclosure.