Patent Publication Number: US-10328694-B2

Title: Printed circuit board with recessed pocket for fluid droplet ejection die

Description:
BACKGROUND 
     Fluid droplet ejection printing typically relies upon fluid droplet ejection dies by which droplets of fluid are selectively ejected onto a medium. Control of the fluid ejection may be facilitated using a circuit chip that transmits signals to each fluid droplet ejection die. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view schematically illustrating an example print head. 
         FIG. 2  is a sectional view schematically illustrating another example print head. 
         FIG. 3  is a flow diagram of an example method for forming the printed of  FIG. 1  or the print head of  FIG. 2 . 
         FIG. 4  is a sectional view schematically illustrating another example print head. 
         FIG. 5  is a sectional view schematically illustrating another example print head. 
         FIG. 6  is a schematic diagram of an example printing system. 
         FIG. 7  is a fragmentary plan view of a portion of an example print bar of the printing system of  FIG. 6 . 
         FIG. 8  is a sectional view of a portion of the print bar of  FIG. 7 . 
         FIGS. 9-13  are sectional views illustrating forming of the portion of the print bar of  FIG. 8 . 
         FIGS. 14 and 15  are sectional views illustrating one example of forming of another example print bar. 
         FIGS. 16 and 17  are sectional views illustrating another example of forming another example print bar. 
     
    
    
     DETAILED DESCRIPTION OF EXAMPLES 
       FIG. 1  schematically illustrates an example fluid droplet ejection print head  20 . As will be described hereafter, fluid droplet ejection print head  20  utilizes a printed circuit board as a support for an fluid droplet ejection die. The printed circuit board includes a recessed pocket in which the die is located such that the die is less proud. As a result, planarity of the print head is enhanced. Enhanced planarity of the printed may facilitate enhanced servicing of the print head dies. In another example, media (Paper/powder) to printhead spacing may be reduced. 
     Print head  20  comprises printed circuit board  24  and fluid droplet ejection die  26 . Printed circuit board (PCB)  24  comprises a platform that mechanically supports electronic components using conductive tracks or traces, pads and other features. In one implementation, printed circuit board  24  comprises a nonconductive substrate upon which an electrically conductive sheet is laminated and etched or otherwise patterned to form tracks or traces, pads and other features. In one implementation, the electrically conductive sheet comprises a sheet of copper. In one implementation, printed circuit board  24  comprises multiple layers or laminations of nonconductive substrates and electrically conductive traces. 
     In one implementation, printed circuit board  24  comprises a fire retardant 4 (FR4) printed circuit board, wherein FR4 is a glass fiber epoxy laminate. In one implementation, the glass fiber epoxy laminate comprises core layers comprising a glass fiber reinforcement material embedded in an epoxy resin matrix upon which electrically conductive traces are formed, wherein the core layers are laminated to one another by intermediate prepreg layers, epoxy coated glass fabric layers. 
     In yet other implementations, printed circuit board  24  may be formed from other core materials which are laminated to one another using other glues, adhesives or epoxies. For example, in another implementation, printed circuit board  14  may comprise a composite epoxy material (OEM) printed circuit board, wherein the glass fiber fabric layers or cores are laminated to one another by a laminated paper. 
     As further shown by  FIG. 1 , printed circuit board  24  comprises a recessed pocket  30  having a floor  32 , sides  34  and a mouth  36 . Pocket  30  forms a cavity, volume or recess that extends into printed circuit board  24  from face  40  of printed circuit board  24 . Pocket  30  is sized to at least partially receive fluid droplet ejection die  26 . In the example illustrated, pocket  30  has a depth d greater than or equal to a thickness of die  26 . In one implementation, pocket  30  has a depth d of at least 150 μm. 
     In one implementation, pocket  30  extends into and is contained within a single topmost layer of printed circuit board  24 . For example, in one implementation, pocket  30  extends to the topmost cover layer which is not contact and underlie an electrically conductive trace, such as a layer of prepreg. In one implementation, pocket  30  extends through the topmost cover layer so as to expose an electrically conductive trace or electrical contact pad provided on an underlying core layer of printed circuit board  24 . In yet another implementation, pocket  30  extends through a topmost cover layer and further into an underlying core layer. 
     Fluid droplet ejection die  26  comprises a printing element by which droplets fluid, such as ink, are selectively ejected or fired through corresponding nozzles. In one implementation fluid droplet ejection die  26  comprises an arrangement of firing chambers that are proximate to corresponding nozzles, wherein drop ejectors are located within such firing chambers. In one implementation, such drop ejectors comprise thermal fluid droplet ejection resistors that are supplied with electric current to generate sufficient heat to vaporize or nucleate adjacent fluid within the corresponding firing chamber so as to create a bubble, wherein the bubble forcefully ejects a drop or drops of fluid through the corresponding nozzle. In yet other implementations, die  26  may support other types of drop ejectors such as piezo-resistive drop ejectors, wherein a flexible diaphragm is moved to eject a drop or drops of fluid through a corresponding nozzle. 
     As shown by  FIG. 1 , die  26  is at least partially received within pocket  30 . Die  26  is supported by floor  32  of pocket  36 . Unless otherwise specifically noted, recitations that a die is “supported” by the floor encompasses both the die being directly supported by the floor, in contact with the floor, and the die being indirectly supported by the floor, with one or more intermediate structures or materials sandwiched between the floor and the die. 
     In the example illustrated, die  26  is supported by the floor  32  with a an outer face  42  of the die  26  extending substantially coplanar or substantially flush with face  40  of printed circuit board  24 . The term “substantially coplanar” or “substantially flush” means that the outermost face of the die and the outermost face of the print head extend within planes that are coplanar with one another or within a spacing or distance of +/−20 um from one another with either the die rising above or being proud with respect to the outermost surface of the print head or the outermost surface of the print head rising above the outer more surface of the die. The outermost face of a die means the surface of die  42  closest to the print medium during printing. Likewise, the outermost face of a printed circuit board means the surface of the printed circuit board (excluding electronic devices or componentry supported by the printed circuit board) closest to the print medium during printing. In circumstances where the outermost faces of the die or the print head are irregular (not flat or planar all across the printed circuit board), the outermost face of the print head refers to the height of the tallest projections (excluding electronic devices or componentry supported by the printed circuit board) rising from the face, such as the height of electrical traces (or their coverings) or contact pads rising above the face. In such an implementation, because face  42  and face  40  are substantially coplanar or substantially flush with one another, servicing of print head  20  may be enhanced. 
     As schematically illustrated by  FIG. 2  which illustrates print head  120 , in other implementations, fluid droplet ejection die  26  may be positioned within a pocket  30  and supported by floor  32  such that surface  42  of fluid droplet ejection die  26  is not substantially flush or not substantially coplanar with the outer face  40  of printed circuit board  24 . As illustrated by  FIG. 2 , in one implementation, the outermost face  42  of die  26  may be recessed within pocket  30  relative to outermost face  40  of printed circuit board  24 . In some implementations, such recessing of die  26  provides additional height or volume within pocket  30  for electrical connectors that connect die  26  to printed circuit board  24  as well as covering layers, such as an encapsulating layer that encapsulates such electric connectors. 
     Alternatively, as indicated by broken lines in  FIG. 2 , in some implementations, outermost face  42  of die  26  may project beyond pocket  30  and beyond outermost face  40 . In such an implementation, although surface  42  remains proud with respect to surface  40 , the extent to which surface  42  is proud with respect to printed circuit board  24  and its outermost surface  40  is reduced. 
       FIG. 3  is a flow diagram of an example method  200  for forming a print head, such as print head  20 . As indicated by block  202 , a printed circuit board (PCB) with a recessed pocket having a floor, such as printed circuit board  24 , is provided. In one implementation, the pocket is molded into one or more of the layers of the printed circuit board during its fabrication. In yet another implementation, the pocket is formed by performing material removal processes on the printed circuit board. For example, the pocket  30  may be formed by routing a recess into printed circuit board  24 . In one implementation, the depth of the pocket is controlled to control the relative positioning of the outermost surfaces of the die and the printed circuit board. 
     In one implementation, the depth of the pocket  30  may not be precisely controlled, possibly due to the process by which the pocket  30  is formed. In such a circumstance, the pocket  30  may be provided with a depth greater than a thickness of the die  26 , wherein additional structures or materials, such as a spacer, shim, glue, epoxy or the like, are provided along the floor of the pocket or are provided to the underside of the die  26  to control or adjust the relative positioning of the outermost surface  42  of the die  26  and the printed circuit board  24 . 
     As indicated by block  204 , die  26  is positioned upon floor  32 . In one implementation, die  26  is positioned directly upon floor  32  in which die  26  contacts floor  32 . In yet another implementation, additional materials, substances or structures are sandwiched between floor  32  and the opposite surface of die  26 . For example, in one implementation, an epoxy or glue may be applied to either or both of the mutually facing surfaces of die  26  and floor  32 . In one implementation, a shim or spacer, or multiple shims and spacers, may rest upon floor  32  to raise die  26  within pocket  34 , may be bonded to floor  32  or may be bonded or otherwise secured to die  26 . 
     In some implementations, the shim or spacer may be compressible or resiliently compressible. In such an implementation, die  26  may compress the shim or spacer, wherein once positioned at a desired height or level of planarity with respect to outermost surface  40  of printed circuit board  24  and while the shim or spacer is compressed, die  26  is retained at the selected height, such as with glue, epoxy, molding compound or the like. 
       FIG. 4  schematically illustrates print head  220 , an example of print head  20 . Print head  220  comprises printed circuit board  224 , fluid droplet ejection die  26  (described above) and electrical interconnect  27 . Printed circuit board  224  is similar to printed circuit board  24  except that printed circuit board  224  is specifically illustrated as comprising multiple laminated layers comprising core layers  260 A,  260 B,  260 C (collectively referred to as core layers  260 ), traces  262 , contact pad  263 , binding layers  264 A,  264 B (collectively referred to as binding layers of  264 ), electrically conductive vias  265  (one of which is shown) and topmost cover layer  266 . 
     Core layers  260  comprise dielectric layers upon which are formed or patterned electrically conductive traces  262 . In one implementation in which printed circuit board  224  comprises an FR4 printed circuit board, core layers  260  comprise a glass fiber fabric and epoxy resin matrix. Although  FIG. 4  illustrates three core layers and two intermediate binding layer  264  for ease of illustration, in other implementations, printed circuit board  224  may comprise additional or fewer core layers  260  and associated traces  262  as well as additional binding layers  264 . 
     Traces  262  are formed from metals, such as copper. In one implementation, traces  262  are formed by etching a copper sheet plated upon core layers  260 . Binding layers  264  comprise layers that join core layers  260  and encapsulate traces  262 . In one implementation in which printed circuit board  224  comprises an FR4 printed circuit board, binding layers  260  comprise prepreg, an epoxy coated glass fabric. In other implementations, binding layer  264  may comprise a laminated paper such as with a OEM printed circuit board. 
     Electrically conductive via  265  extends through core layers  260  and provides electrical connection between electrically conductive traces  262  of different layers  460 . In one implementation, electrically conductive via  265  is formed by drilling through layers  260 ,  264  and plating copper within such drilled apertures. 
     Cover layer  266  comprises a layer of material or multiple layers of material that overlie the uppermost core layer  260 A and its electrical traces  262 . Cover layer  266  omits the electrical traces or electrical contact pads. In one implementation, cover layer  226  comprise the same material forming binding layers  264 . In one implementation, cover layer  226  comprises an epoxy or an epoxy coated glass fabric such as prepreg. 
     As further specifically shown by  FIG. 4 , print head  220  comprises pocket  230  and fluid passage  280 . Pocket  230  is similar to pocket  30 . Pocket  230  includes floor  32 , sides  34  and mouth  36 . Pocket  230  contains die  26 . In the example illustrated, die  26  directly contacts floor  32  of pocket  230  or is adhesively bonded to the floor  32  of pocket  230 . 
     In the example illustrated, floor of pocket  230  overlies core layer  260 A such that pocket  230  does not project into or extend into core layer  260 A. Pocket  230  exposes electrical contact pad  263  supported by core layer  260 A, facilitating the connection of the electrical interconnect  227 , a wire or flexible circuit, to contact pad  263  and to die  26 . Although not illustrated, in some implementations, electrical interconnect  227  may itself be covered or coated by a protective layer or layers. 
     Fluid passage  280  extends through printed circuit board  224  from a back face  282  opposite to face  40 . Fluid passage  280  provides a passage by which fluid, such as ink, may be supplied from face  282  through printed circuit board  224  to slots, manifold or other fluid delivery passages of die  26 . In the example illustrated, fluid passage  280  extends through and across core layers  260  and binding layers  264 . In such an implementation, surfaces along fluid passage  280  are coated with a barrier layer  284  to inhibit diffusion or seepage of fluids between the layers of printed circuit board  224 . In other implementations, a fluid directing tube or liner may be inserted into fluid passage to direct fluid to die  26 . In other implementations, one of layers  260 ,  264  may continuously or homogenously extend upwards and/or downwards across the other layers  260 ,  264  from face  282  to floor  32  of pocket  230 , wherein fluid passage  280  is formed through the one layer, reducing or eliminating the number of lamination junctions or layer junctions along fluid passage  280 . 
       FIG. 5  schematically illustrates print head  320 , another implementation of print head  20 . Print head  320  is similar to print head  220  except that printed circuit board  224  comprises pocket  330  in place of pocket  230  and additionally comprises spacer  332 . Those remaining structures of print head  320  which correspond to structures of print head  220  are numbered similarly. 
     Similar to pocket  230 , pocket  330  comprises floor  32 , sides  34  and mouth  36 . Unlike pocket  230 , pocket  330  extends from outermost face  40  through multiple layers or laminations a printed circuit board  224 . In the example illustrated, pocket  230  extends through both cover layer  266  and core layer  260 A, wherein floor  32  overlies binding layer  264 A. 
     Spacer  332  comprises a structure that serves as a shim, elevating or spacing die  26  with respect to floor  32 . In one implementation, spacer  332  comprises a series of individual spacing elements. In another implementation, spacer  332  comprises a ring. In yet another implementation, spacer  332  comprises the rim of a filter that extends across fluid passage  280 , filtering fluid as it passes from fluid passage  280  to die  26 . In one implementation, spacer  332  is provided as part of a tube or liner extending along fluid passage  280 . 
     In one implementation, spacer  332  is compressible or resiliently compressible. In such an implementation, die  26  may compress the shim or spacer, wherein once positioned at a desired height or level of planarity with respect to outermost surface  40  of printed circuit board  224  and while the shim or spacer  332  is compressed, die  26  is retained at the selected height, such as with glue, epoxy, molding compound or the like. 
       FIG. 6  is a sectional view schematically illustrating an example printing system  400  which utilizes an implementation of any of print heads  20 ,  120 ,  220  or  320  described above. Printing system  400  comprises media feed  402 , fluid supplies  404 , controller  406  and print bar  408 . Media feed  402  comprises a device to move media, such as sheets or webs of paper, into position for being printed upon by print bar  408 . In one implementation, media feed  402  comprises one or more rollers by which sheets or webs of media  403  are driven and moved relative to print bar  408 . 
     Fluid supplies  404  supply fluid, such as ink, to different fluid droplet ejection dies that are part of print bar  408 . In one implementation, fluid supplies  404  supply different types of fluid to their respective dies. For example, in one implementation, fluid supplies  404  supply black, cyan, magenta and yellow inks to their respective associated dies. In one implementation, fluid supplies  404  are carried by print bar  408 . In another implementation, fluid supplies  404  are “off-axis”, located remote with respect to print bar  408 , wherein fluid is supplied through one or more conduits. 
     Controller  406  comprises electronics that output control signals controlling the ejection of the fluid from each of the dies on print bar  408 . In the example illustrated, controller  406  outputs electric control signals which are transmitted to a processor chip  407 , such as an application-specific integrated circuit (ASIC), supported by print bar  408 . The processor chip or ASIC outputs electric signals to the dies  26  based upon the control signals received from controller  406 . Chip  407  addresses transistor arrays to selectively actuate the fluid droplet ejectors of the dies. The control signals transmitted to the dies cause the fluid, such as ink, to be selectively deposited in a predetermined image or pattern upon the print media  403  moved by media feed  402 . 
     Print bar  408  comprises a structure utilizing one example of the architecture described above with respect to print head  20 ,  120 ,  220  and  320 . In one implementation, print bar  408  is stationary opposite to media feed  302  to facilitate page wide printing. In another implementation, print bar  408  is carried by a carriage, wherein the carriage is scanned across the media  403  during printing. 
     Print bar  408  comprises printed circuit board  424  and fluid droplet ejection dies  26 . Printed circuit board  424  is similar to printed circuit board  224  described above except that printed circuit board  424  is specifically illustrated as comprising multiple pockets  230  containing multiple dies  26 , wherein each of such dies  26  are supported such that outermost faces  42  of dies  26  are recessed within their respective pockets  230  from outermost face  40  of printed circuit board  424 . Such recessing provides additional space for electrical interconnects  227  and any covering upon such electrical interconnects  227  without interconnects  227  or their coverings protruding or substantially protruding beyond outermost face  40 . 
       FIG. 7  is a bottom view of print bar  508 , an example implementation of print bar  408 . Print bar  508  may be utilized in printing system  400  in place of print bar  408 , wherein print bar  508  also supports processing chip  407 . As shown by  FIG. 7 , print bar  508  comprises printed circuit board  424  having multiple pockets  230  in which are received fluid droplet ejection dies  26 . In the example illustrated in  FIG. 7 , the nozzle plate (in some implementations formed from a material such as Bisphenol A Novolac epoxy (SU8)) are omitted to illustrate the slots  531  of each of dies  26 . As further shown by  FIG. 7 , pockets  230  provided within printed circuit board  424  extend in multiple rows, wherein the pockets  230  of one row are staggered respect to adjacent pockets of another row. In other words, the pockets  230  have end portions that overlap one another in a direction perpendicular to the major dimension or length of each of the pockets. As a result, dies  26  received within such pockets  26  are also staggered with respect to one another and also overlap. Such overlapping enhances printing. 
       FIG. 8  is a sectional view illustrating one example print head portion  520  of print bar  508  shown in  FIG. 7 . Print head portion  520  comprises printed circuit board  524 , ink jet die  526 , interconnect  527  and encapsulant  528 . Printed circuit board  524  comprises core and intermediate binding layer region  560 , cover layer  566 , cover layer  568 , pocket  530  and fluid passage  580 . Core and intermediate binding layer region  560  comprises that portion of printed circuit board  524  containing multiple layers or laminations of core layers  260 , binding layers  264 , electrically conductive traces  262 , and electrical vias  265  as illustrated and described above with respect to printed circuit board  224  of  FIG. 4 . 
     Cover layer  566  comprises a layer or multiple layers of materials that cover one face of region  560 . Cover layer  566  is similar to cover layer  266  described above. In one implementation, cover layer  566  omits electrically conductive traces. In one implementation, cover layer  566  comprises the same material forming binding layers  264 . In one implementation, cover layer  566  comprises an epoxy or an epoxy coated glass fabric such as prepreg. 
     Pocket  530  is similar to pocket  30 . Pocket  230  includes floor  32 , sides  34  and mouth  36 . Although pocket  230  is illustrated as having a single same level floor  32 , in other implementations, pocket  32  may comprise a multilevel, multi-tiered or otherwise irregular floor  32 . Pocket  530  contains die  26 . In the example illustrated, cover layer  568  forms a portion of floor  532 . In the example illustrated, die  526  is adhesively secured to the surface of cover layer  568  forming the portion of floor  532 . 
     In the example illustrated, floor of pocket  230  overlies core layer  260 A such that pocket  230  does not project into or extend into core layer region  560 . Pocket  530  exposes electrical contact pad  563  supported by a core layer a region  560 , facilitating the connection of the electrical interconnect  527 , a wire or flexible circuit, to contact pad  563  and to die  526 . In the example illustrated, electrical interconnect  527  is further covered or coated by a protective layer or layers  527  that formed from a material such as an epoxy. 
     Cover layer  568  comprises a layer or multiple layers of material extending on a back side of region  560  opposite to that of layer  566 . In one implementation, layer  568  omits electrically conductive traces. In one implementation, layer  568  is formed from a material similar to the material forming layer  566 . In one implementation, layer  568  is formed from the same material as binding layers  264  of region  560 . In one implementation, layer  568  is formed from an epoxy coated glass fabric, such as prepreg. 
     As further shown by  FIG. 8 , region  560  defines an opening  586  cover layer  568  which is surrounded by region  560 . Opening  586  is aligned with and within the profile of pocket  530 . Opening  586  has sides spaced from and within the sides  34  of pocket  530  such that perimeter portions of floor  32  are formed by the underlying region  560  while the central portion of floor  32  is formed by cover layer  568 . Cover layer  568  extends into opening  586 . In one implementation, cover layer  568  fills opening  586 , wherein portions of cover layer  568  within opening  586  subsequently removed to form fluid passage  580 . In other implementations, fluid passage  580  is molded into or as part of those portions of cover layer  568  within opening  586 . 
     Fluid passage  580  extends through printed circuit board  524  from a face  582  opposite to face  40 . Fluid passage  580  provides a passage by which fluid, such as ink, may be supplied from face  582  through print circuit board  524  to slots, manifold or other fluid delivery passages of die  526 . In the example illustrated, until reaching die  526 , fluid passage  580  is continuously bounded by or defined by the homogenous material forming cover layer  568  that extends within opening  586 , reducing or eliminating the number of lamination junctions or layer junctions along fluid passage  580 . 
     Die  526  is similar to die  26  described above. Adhesive layer  592  bonds died  526  to a surface of cover layer  586  forming a portion of the floor  32  of pocket  530 . In the example illustrated, die  526  comprises silicon substrate  592 , barrier layer  594  and drop eject is  599 . Silicon substrate  592  supports electrical contact pads  591  for electrical connection to printed circuit board  524  by electrical interconnect  527 . Silicon substrate  592  further comprises slots  531  that extend through substrate  592 , whereby fluid is provided by fluid passage  580  for printing. 
     Barrier layer  594  cooperates with substrate  592  to form individual firing chambers  596  and provide nozzles  597 . In one implementation, barrier layer  594  is formed from a material such as SU8. Each firing chamber  596  contains a drop ejector  599  by which drops of fluid, such as ink, are selectively ejected through the nozzle openings  597 . In one implementation, drop injectors  599  comprise thermal fluid droplet ejection resistors. In another implementation, drop injectors  599  comprise other drop ejection mechanisms such as piezo-resistive drop injectors. 
       FIGS. 9-13  illustrates one example method for forming print head portion  520  of  FIG. 8 . As shown by  FIG. 9 , printed circuit board  524  with pocket  530  is provided. Printed circuit board  524  comprises region  560 , cover layer  566  and cover layer  568  as described above.  FIG. 9  illustrates cover layer  566  after pocket  530  has been formed within cover layer  566 . In one implementation, pocket  530  is molded during the forming of cover layer  566 , while cover layer  566  is in a liquid or malleable state, prior to solidification or curing. In other implementations, portions of cover layer  56  are removed, such as by routing, to form pocket  530 . In the fabrication state shown in  FIG. 9 , cover layer  568  fills opening  586  of region  560 . 
       FIG. 10  illustrates the application or depositing of adhesive layer  590  upon cover layer  560  which extends at the bottom of pocket  530  to form a portion of floor  32 .  FIG. 11  illustrates the attachment of die  526  within pocket  530  using the previously applied adhesive layer  590 .  FIG. 12  illustrates wire bonding of electrical interconnect  527  to contact pads  563  of printed circuit board  524  and to contact pads  591  of die  526 . As shown in  FIG. 12 , electrical interconnects  527  are further encapsulated by a dielectric encapsulant  528  such as an epoxy. 
       FIG. 13  illustrates the forming of fluid passage  580  through cover layer  568  within opening  586 . Fluid passage  580  extends into substrate  592  of die  526  such that slots  531  are brought into connection with fluid passage  580 . In one implementation, fluid passage  580  is formed by material removal, such as with a plunge cut by a router. In other implementations, fluid passage  580  may be formed for other material removal processes. In still other implementations, fluid passages  580  may be molded into cover layer  568  while the material a cover layer  568  is in a liquid or malleable state, similar to the molding of pocket  530 . In such an implementation, adhesive layer  590  is instead formed upon those portions of floor  32  provided by the uppermost layer of region  560 . 
       FIGS. 14 and 15  illustrate the forming of another example print head portion  620  of print bar  508  shown in  FIG. 7 . As shown in  FIG. 15 , which illustrates the completed printed portion  620 , print head portion  620  comprises printed circuit board  624 , ink jet dies  526 , interconnects  527  and encapsulants  528 . As shown by  FIG. 14 , printed circuit board  624  is similar to printed circuit board  524  except that printed circuit board  624  comprises multiple spaced pockets  530 . In one implementation, the multiple spaced pockets  530  are formed with a router as part of printed circuit board fabrication process or created by gang sawing the finished printed circuit board  524 . 
     As shown by  FIG. 15 , each pocket  530  is filled with an adhesive  692  prior to positioning of dies  526  within their respective pockets  530 . In the example illustrated, each die  526  is surrounded by an adhesive on its backside and all edges for enhanced adhesion. In the example illustrated, the depth of each recess pocket  530  may be varied to reduce the overall die protrusion from the outermost surface  40  of print head die  624 . 
     Once each die  526  has been position within its associated pocket  530 , wire bonding with electrical interconnects  527  is performed and encapsulant  528  is applied over electrical interconnects  527 . Thereafter, backside fluid slots or fluid passages  680  are formed. Fluid passages  680  extend through the floors  532  of pockets  530  to connect fluid passages  680  to slots  531  of each of dies  526 . In one implementation, such backside fluid passages  680  are formed with a plunge cut sawing or a laser. In one implementation, such fluid passages  680  are coated with a barrier layer  284  such as described above with respect print head  220  in  FIG. 4 . In another implementation, such fluid passages  680  are provided with a tube or liner. It still other implementations, printed circuit board  624  is fabricated such that one of its laminated layers defines the sides of fluid passage  680  along its length, similar to cover layer  568  extending along or defining fluid passage  580 . 
       FIGS. 16 and 17  illustrate the forming of another example print head portion  720  of print bar  508  shown in  FIG. 7 . As shown in  FIG. 17 , which illustrates the completed print head portion ink jet dies  526  interconnects  527  and encapsulants  528 . As shown by  FIG. 16 , printed circuit board  724  is similar to printed circuit board  524  except that printed circuit board  724  comprises a single large pocket  730  in which multiple dies  526  are to be located. In one implementation, pocket  730  is formed with a router as part of printed circuit board fabrication process or created by gang sawing the finished printed circuit board  724 . 
     As shown by  FIG. 17 , pocket  730  is filled with an adhesive  792  prior to positioning of dies  526  within the one pocket  730 . In the example illustrated, each die  526  is surrounded by an adhesive on it backside and all edges for enhanced adhesion. In the example illustrated, the depth of pocket  730  may be varied to reduce the overall die protrusion from the outermost surface  40  of print head die  724 . 
     Once each die  526  has been positioned within pocket  730 , wire bonding with electrical interconnects  527  is performed. Encapsulant  528  is formed so as to encapsulate electrical interconnects  527 . Thereafter, backside fluid slots or fluid passages  680  are formed. Each fluid passage  680  extends through the floor  732  to connect fluid passages  680  to slots  531  of each of dies  526 . In one implementation, such backside fluid passages  680  are formed by plunge cut sawing or a laser. In one implementation, such fluid passages  680  are coated with a barrier layer  284  such as described above with respect print head  220  in  FIG. 4 . In another implementation, such fluid passages  680  are provided with a tube or liner. It still other implementations, printed circuit board  724  is fabricated such that one of its laminated layers defines the sides of fluid passage  680  along its length, similar to cover layer  568  extending along or defining fluid passage  580 . 
     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 spirit and scope of the claimed subject matter. For example, although different example implementations may have been described as including one or more features providing one or more 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.