Patent Publication Number: US-11648773-B2

Title: Unsupported top hat layers in printhead dies

Description:
BACKGROUND 
     Printers are used to print images onto a print medium. Printers may print images using different types of printing fluids and/or materials. For example, some printers may use ink, toner, and the like. A print job may be transmitted to the printer and the printer may dispense the printing fluids and/or materials on the print medium in accordance with the print job. 
     The printing fluid may be ejected from a printhead. The printheads may be packaged and sealed to prevent the printing fluid from leaking during transport. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1 A  is a block diagram of a top view of an example a printhead die of the present disclosure; 
         FIG.  1 B  is a block diagram of a closer up view of an initial unsupported top hat layer portion of printhead die of the present disclosure; 
         FIG.  2    is a block diagram of a cross-sectional view of an example chamber of the printhead of the present disclosure; 
         FIG.  3    is a block diagram of a top view of an example of a printhead die with pillars of the present disclosure; 
         FIG.  4    is a block diagram of a cross-sectional view of an example chamber of a printhead with pillars of the present disclosure; 
         FIG.  5    is a block diagram of a top view of another example of a printhead of the present disclosure; 
         FIG.  6    is a flow chart of an example method for fabricating the printhead die of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Examples described herein provide an integrated printhead with an improved unsupported top hat layer and chamber to prevent tearing of the top hat layer during a de-taping process. For example, printheads can be packaged and sealed after manufacturing to ensure that the printing fluid in the printhead does not leak or evaporate before use. 
     As printhead technology has advanced, the materials used in the manufacturing processes have also changed. In some examples, tape can be placed over the printhead to prevent the printing fluid from leaking. However, when the tape is removed, the removal of the tape may create deflection and stress on the portions of the printhead that can result in damage to the printhead. The resulting damage can cause the printing fluid to leak or escape. 
     Mechanical solutions can be created, but the mechanical solutions can be expensive to implement. Tape is a relatively low cost material that can help to reduce the overall costs of the printhead. 
     Examples herein provide a printhead that minimizes beam length (e.g., a width across an unsupported top hat portion) where taping begins to minimize an amount of deflection when the tape is removed. Minimizing the amount of deflection at the point of initiation of tape adhesive to the unsupported top hat layer may prevent the top hat layer from being damaged when the tape is removed. As a result, tape can still be used to seal the printing fluid in the printhead without damaging the top hat layer of the printhead during removal of the tape by the customer. 
       FIG.  1 A  illustrates a top view of an example printhead die  100  and  FIG.  2    illustrates a cross-sectional view of the example printhead die  100  along a dashed line  134 . The reader may refer to  FIG.  1 A  and  FIG.  2    simultaneously to view the different layers of the printhead die  100  that are discussed in  FIG.  1 A , but may be difficult to see in the top view illustrated in  FIG.  1 A . 
     In one example, the printhead die  100  may be part of an integrated printhead (IPH). IPHs may be devices that combine an ink cartridge with a printhead. In other words, unlike some printers that have distinct printheads and printing fluid containers (e.g., off-axis ink supply with permanent printheads), the printhead may be integrated into the ink cartridge in an IPH. 
     In one example, the printhead die  100  may include a substrate  112  that includes slotted portions  102   1 - 102   n  that form a fluidic connection to the printhead (hereinafter also referred to individually as a slotted portion  102  and collectively as slotted portions  102 ). In an example, the substrate  112  may be a silicon substrate. The slotted portions  102  may each be associated with a different colored printing fluid. 
     Although multiple slotted portions  102  are illustrated in  FIG.  1 A , it should be noted that a single slotted portion may be included in a single printhead die  100 . In other words, printhead die  100  can be fabricated with multiple slotted portions  102  for multiple colors or can be fabricated with a single slotted portion  102  for a single color. 
     The number of slotted portions  102  created in the substrate  112  may be a function of a number of different colors of printing fluid that are dispensed by the printhead die  100 . For example for a printhead die  100  that dispenses cyan, yellow, and magenta colors, the printhead die  100  may have three slotted portions  102  (e.g., a cyan slot, a yellow slot, and a magenta slot on a single printhead substrate  112 ). 
     In one example, the slotted portions  102  may include a top hat layer  104 , and a chamber layer  138  (illustrated in  FIG.  2   ) that is beneath the top hat layer  104  that is etched to form walls  136 . As shown in  FIG.  2   , the top hat layer  104  may be arranged above the chamber layer  138  and also above the substrate  112 . Thus, as illustrated in  FIG.  1 A , the top hat layer  104  is to be understood as being arranged above both the substrate  112  and the chamber layer  138  (e.g., in the z-axis, coming out of the page). The walls  136  are illustrated as dashed lines that surround a perimeter of the slotted portions  102 .  FIG.  2    illustrates how the walls  136  support the outer edges of the top hat layer  104 . 
     The portions of the chamber layer  138  that are etched away may form a void  108 . The void  108  is illustrated in diagonal lines in the top view illustrated in  FIG.  1 A .  FIG.  2    illustrates the void  108  as a volume formed between the top hat layer  104 , the walls  136  of the chamber layer  138 , and the substrate  112 . The portions of the top hat layer  104  that are over the void  108  may be referred to as the unsupported top hat layer  104 . The portions of the top hat layer  104  that rest on the chamber layer  138  and/or the walls  136  may be referred to as the supported top hat layer portion. 
     In one example, the top hat layer  104  may include an initial unsupported top hat layer portion  106 . The initial unsupported top hat layer portion  106  may be defined by a first end  120  and a second end  122 .  FIG.  1 B  illustrates a more detailed view of the initial unsupported top hat layer portion  106 , and is discussed in further details below. 
     As illustrated in  FIG.  2   , the void  108  in the chamber layer  138  may form a volume to store printing fluid  204 . The void  108  may run along a length of the slotted portion  102  and may also be referred to as a fluid channel that runs along a length of the slotted portion  102 . The printing fluid  204  may be fed through an ink feed hole  132  (shown in dashed lines in  FIG.  1 A ) formed through the substrate  112 , as shown in  FIG.  2   . 
     The printing fluid  204  may then be ejected via printing fluid ejection chambers  110   1  to  110   m  (of which only  110   1 ,  110   2 , and  110   m  are labeled, hereinafter also referred to individually as a printing fluid ejection chamber  110  or collectively as printing fluid ejection chambers  110 ). The printing fluid ejection chambers  110  may be formed or coupled to opposite sides of the fluid channel and along a length of the chamber layer  138  and top hat layer  104 . Said another way, in  FIG.  1 A , if the top view of the slotted portion  102  were divided along a length of the slotted portion (e.g., left to right when viewing the page), the printing fluid ejection chambers  110  may be formed on opposite sides (e.g., along the perimeter on both sides of the slotted portion  102  when viewed from the top as shown in  FIG.  1 A ). An opening  130   1  to  130   p  (of which only  130   1 ,  130   2 ,  130   3 , and  130   p  are labeled; hereinafter also referred to individually as an opening  130  or collectively as openings  130 ) may be formed in the top hat layer  104  over each one of the printing fluid ejection chambers  110 . 
     The printing fluid ejection chambers  110  are shown formed as a portion of the cross-section of  FIG.  2    shown by dashed lines. The volume created by the void  108  may store the printing fluid  204  that is fed through the ink feed hole  132 . The printing fluid  204  may be fed to each one of the printing fluid ejection chambers  110  during operation of the printhead die  100 . For example, the printing fluid  204  may flow through the fluid channel that runs into and out of the page in  FIG.  2   . 
       FIG.  2    illustrates the openings  130  of the printing fluid ejection chambers  110 . The openings  130  may allow the printing fluid  204  to be ejected one drop at a time. The printing fluid may be ejected by an actuator  202  that forces the printing fluid through the openings  130  (e.g., a resistive element, a piezo actuator, etc.). 
     In one example, the top hat layer  104  and the chamber layer  138  may be formed or fabricated from the same material. For example, the top hat layer  104  and the chamber layer  138  may be fabricated from a photo definable polymer or negative photoresist material. An example of the photo definable polymer may include SU8. The photo definable polymer may be soft or flexible. 
     In one example, the chamber layer  138  may be formed by depositing the photo definable polymer onto the substrate  112 . A lithography and etching process may be applied to the photo definable polymer to form the void  108 . The top hat layer  104  may be a thin layer that is deposited on top of the chamber layer  138  via a plastic film that can be removed. Lithography and etching steps can be applied to form openings  130  in the top hat layer  104  at the locations of the printing fluid ejection chambers  110 . 
     In one example, the printing fluid ejection chambers  110  may eject the printing fluid  204  using a thermal resistor in the actuator  202 . For example, to eject the printing fluid  204 , a thermal resistor may heat a fluid in the printing fluid ejection chambers  110 . The heat may cause a steam bubble to be formed in the fluid and burst towards an opening of the printing fluid ejection chamber  110 . The printing fluid may be fed into the printing fluid ejection chambers  110  from the void  108  and the force of the bubble formation may cause a droplet of printing fluid  204  to be ejected from the printing fluid ejection chambers  110 . 
     It should be noted that the printhead  100  has been simplified for ease of explanation. The printhead die  100  may include additional components and circuitry that are not shown. For example, the printhead die  100  may include connection interfaces to a controller or other electronics, a housing, thin film dielectrics, thin film conductors, and the like. 
     Referring back to  FIG.  1 A , the printhead die  100  may be shipped with an adhesive tape  114  over each slotted portion  102  or a single piece of the adhesive tape  114  over all three slotted portions  102 . The adhesive tape  114  may be applied to prevent the printing fluid from leaking out of the openings  130  in the top hat layer  104  over the printing fluid ejection chambers  110  during shipping. However, when the adhesive tape  114  is removed before the printhead die is used, the adhesive tape  114  may damage the top hat layer  104 . For example, a portion of the top hat layer  104  can be damaged or torn by tape adhesive forces on the unsupported top hat layer portions of the top hat layer  104  causing the printing fluid  204  to leak from the chamber layer void  108 . 
     The present disclosure improves the initial unsupported top hat layer portion  106  to prevent damage during removal of the adhesive tape  114 . In one example, the initial unsupported top hat layer portion  106  may be soft or flexible and be damaged from removal of the adhesive tape  114 . However, the present disclosure forms the initial unsupported top hat layer portion  106  to minimize or significantly reduce the amount of deflection or stress applied to the top hat layer  104  when the adhesive tape  114  is removed. The amount of deflection created by the adhesive tape  114  may be a function of the width of a surface that is attached to the adhesive tape  114 . 
       FIG.  1 B  illustrates a more detailed view of the initial unsupported top hat layer portion  106 . In one example, the unsupported top hat layer portion  106  may be formed to gradually increase a width (w 1 ) from the first end  120  to a gradually wider width (w 2 ) to a desired width (w d ) at the second end  122 . In other words, w d &gt;w 2 &gt;w 1 . The widths w 1 , w 2 , and w d  may also be referred to as the beam length of the top hat layer  104 . 
     The first end  120  may be an end where the adhesive tape  114  begins. The second end  122  may be where a desired width of the top hat layer  104  is reached and where the printing fluid ejection chambers  110  begin. The width, w 1 , of the first end  120  may be at a particular width that minimizes the amount of deflection of the adhesive tape  114  at a point of initiation of the adhesive tape  114  to the printhead die  100 . 
     The width may be gradually increased until a desired width, w d , of the top hat layer  104  is reached. For example, the width of the first end  120  may be less than the width of the second end  122 . The first end  120  may be narrower than the second end  122 . Said another way, the first end  120  may be a narrow end and the second end  122  may be a wide end. 
     In one example, the first end  120  may have a beam length or a width that is approximately one tenth of a beam length or a width of the second end  122 . For example, the first end  120  may have a width of approximately 5-20 microns and the second end  122  may have a width of approximately 100-150 microns. In one example, the first end  120  may have a width of approximately 8 microns and the second end  122  may have a width of approximately 130 microns. 
     Said another way, the first end  120  of the initial unsupported top hat layer portion  106  may be tapered relative to the second end  122  of the initial unsupported top hat layer portion  106 . In one example, the side walls  136  of the initial unsupported top hat layer portion  106  (and corresponding portions of the chamber layer that form the walls  136 ) may be formed at a particular angle θ from the first end  120  towards the second end  122 . The angle θ may be relative to an imaginary point where the two side walls  136  may meet if the walls were continued to the imaginary point, as shown by line  118  in  FIG.  1 B . In one example, the angle may be approximately 30-70 degrees. In one example, the angle may be approximately 45 degrees. 
     Thus, the form of the initial unsupported top hat layer portion  106  may allow the initial deflection and stress caused from the initial removal of the adhesive tape  114  to be minimized. Minimization of the deflection force may prevent damage to the initial unsupported top hat layer portion  106  as well as the remaining supported top hat layer portions of the top hat layer  104 . As the length of the adhesive tape  114  that is removed increases, the deflection force and stress may start to gradually increase as the beam length of the initial unsupported top hat layer portion  106  is increased. The gradually increasing stress may reduce failure rates compared with starting with a beam length of the unsupported top hat layer portion  106  that is large. Thus, the width of the initial unsupported top hat layer portion  106  may be gradually increased up to the desired width of the second end  122  of the initial unsupported top hat layer portion  106 . 
       FIG.  3    illustrates a top view of an example of a slotted portion  302  of a printhead die. In one example, the slotted portion  302  may include a top hat layer  104  and a void  108  (shown as diagonal lines) formed in a portion of a chamber layer, and printing fluid ejection chambers  110  similar to the slotted portion  102 , illustrated in  FIG.  1 A  and described above. The printing fluid ejection chambers  110  may be coupled to or formed on opposite sides of the fluid channel, and along a length of the walls  136 . 
     In one example, the slotted portion  302  may also include openings  130  in the top hat layer  104  over locations of the printing fluid ejection chambers  110 . The slotted portion  302  may also include the ink feed hole  132 . 
     The void  108  may be formed in the chamber layer to create a volume. The void  108  may store printing fluid  204 . The printing fluid  204  may be ejected by the printing fluid ejection chambers  110 , as described above. The slotted portion  302  may also include an initial unsupported top hat layer portion  106 . 
     The initial unsupported top hat layer portion  106  may also be formed to minimize deflection and/or stress caused by removal of adhesive tape applied to the slotted portion  302  before shipping. For example, the initial unsupported top hat layer portion  106  may also have a tapered shape or a trapezoidal shape, as described above in reference to the initial unsupported top hat layer portion  106  of the slotted portion  102 . 
     However, the slotted portion  302  may include pillars  304   1  to  304   l  (hereinafter also referred to individually as a pillar  304  or collectively as pillars  304 ). In one example, the pillars  304  may provide extra support. For example, the pillars  304  may provide a structure or surface to bond to the unsupported top hat layer portion  106 . This bond may further prevent the unsupported top hat layer portion  106  from being damaged when the adhesive tape  114  is removed. 
     In one example, the pillars  304  may be fabricated from the same material as the top hat layer  104  and the chamber layer. For example, the pillars  304  may also be fabricated from a photo definable polymer or negative photoresist material, such as SU8, for example. 
     In one example, the pillars  304  may have a diameter that is a function of a size of the slotted portion  302 . For example, the larger (e.g., width and length) the slotted portion  302  is, the larger the diameter of the pillars  304  may be. In one example, the diameter of the pillars  304  may be approximately 1-5 microns. In one example, the diameter of the pillars  304  may be approximately 2 microns. 
     In one example, the pillars  304  may have the same diameters. In one example, the pillars  304  may have different diameters. 
     In one example, some of the pillars  304  may be located in different areas of the initial unsupported top hat layer portion  106 . For example, the pillars  304   1  and  304   2  may be located towards a tip or first end of the initial unsupported top hat layer portion  106 . The pillars  304   3 - 304   l  may be located through the void  108  closer to a second end of the initial unsupported top hat layer portion  106 . 
       FIG.  4    illustrates a cross-sectional view along a dashed line  306  illustrated in  FIG.  3   . The cross-section view illustrates an example of the void  108  with the pillars  304 . In one example, the void  108  may be formed in the chamber layer to create a volume created by a surface of the substrate  112 , the side walls  136  of the chamber layer and the top hat layer  104 . The volume created by the void  108  may store a printing fluid  204 . The printing fluid  204  may be fed to each one of the printing fluid ejection chambers  110  during operation of the printhead die  100 . 
     As shown in  FIG.  4   , the pillars  304  may be formed through the void  108 . The pillars  304  may be bonded to the top hat layer  104  and the surface of the substrate  112 . Thus, the pillars  304  help to further prevent the initial unsupported top hat layer portion  106  from being damaged, torn, pulled off, and so forth, when the adhesive tape  114  is removed from the slotted portion  302 . 
     It should be noted that although a particular arrangement of the pillars  304  is illustrated in  FIG.  3    that the pillars  304  may be arranged in any shape or distribution. For example, more than two pillars may be arranged in the supported top hat layer portion of the top hat layer  104  and less than, or more than, five pillars  304  may be arranged in a regular or irregular pattern through the void  108  in the initial unsupported top hat layer portion  106 . 
       FIG.  5    illustrates a block diagram of other examples of initial unsupported top hat layer portions  106  of slotted portions of a printhead die of the present disclosure. For example, the slotted portions  102  and  302  illustrated in  FIGS.  1  and  3    illustrate an unsupported top hat layer portion  106  that has a trapezoidal shape with straight lined side walls  136 . The side walls  136  extend from the first end  120  to the second end  122  in a symmetrical form. 
     However, it should be noted that the side walls  136  between the first end  120  and the second end  122  may be formed in other shapes and forms. For example, the slotted portion  502  may have an initial unsupported top hat layer portion  510  formed by a top hat layer  104  over a void  108 . The initial unsupported top hat layer portion  510  may have side walls  516  that form a domed or “fire-hydrant” shape. For example, a first end  508  of the initial unsupported top hat layer portion  510  may have an initial width and then curve out gradually to a desired width. 
     In one example, a slotted portion  504  may have an initial unsupported top hat layer portion  512  formed by a top hat layer  104  over a void  108 . The initial unsupported top hat layer portion  512  may have side walls  516  that form multiple “points” on a first end  520 . For example, the initial unsupported top hat layer portion  512  may have an “M” shape or any other shape with multiple “points”. Each point may have a width that gradually increases from the first end  520  and meets to a desired width. 
     In one example, a slotted portion  506  may have an initial unsupported top hat layer portion  514  formed by a top hat layer  104  over a void  108 . The initial unsupported top hat layer portion  514  may have irregular shaped side walls  516 . For example, the side walls  516  of the initial unsupported top hat layer portion  514  may have multiple curves as the width gradually increases from the first end  518  to a desired width. 
     It should be noted that the slotted portions  502 ,  504 , and  506  illustrated in  FIG.  5    are provided as additional examples and should not be considered limiting. For example, the initial unsupported top hat layer portion  106  of the printhead may have other shapes that are not illustrated in  FIGS.  1 ,  3   , and  5 . For example, although the sidewalls are shown each having the same shape, the sidewalls of the initial unsupported top hat layer portion  106  may have different shapes. For example, one side wall may be straight and the opposite side wall may have a curve or an irregular shape. 
     In one example, the shape of the initial unsupported top hat layer portion  106  may be a function of other components in the printhead. For example, the printhead may have a deflection plate or other component that may be covered by the initial unsupported top hat layer portion  106 . Thus, the unsupported top hat layer portion  106  may have a gradual increase in width from a first end as long as all of the components within the respective slotted portion of the printhead die are covered by the initial unsupported top hat layer portion  106 . 
       FIG.  6    illustrates a flow diagram of an example process flow  600  for fabricating a printhead die of the present disclosure. In an example, the process flow  600  may be performed by different tools or equipment that are operated individually or collectively by a single controller or processor. 
     At block  602 , the method  600  begins. At block  604 , the method  600  provides a substrate. For example, substrate may be a silicon wafer and may include integrated circuit thin films and processes. Each silicon wafer may be processed to form multiple printhead dies. In one example, an ink feed hole may be etched out of the substrate to allow printing fluid to enter the printhead die. 
     At block  606 , the method  600  deposits a first layer of photo definable polymer onto the substrate. The photo definable polymer may be a negative photo resist material such as SU8. The photo definable polymer material may be deposited onto portions of the printed circuit board where the printheads may be formed. The first layer of photo definable material may form the chamber layer. 
     At block  608 , the method  600  applies a mask to the first layer of the photo definable polymer to form a void. For example, the mask may be applied to the first layer to define areas in the photo definable polymer where the void to store printing fluid will be formed. 
     At block  610 , the method  600  performs photolithography and etching processes to form the void in the first layer of the photo definable polymer. For example, the photolithography steps may include exposing portions of the photo definable polymer to certain types of light. The etching process may include wet etch and/or dry etch processes to remove the portions of the photo definable polymer that are exposed to the light. In one example, the etching process may include wet etch and/or dry etch processes to remove the portions of the photo definable polymer that were not exposed to the light. 
     In one example, the remaining portions of the chamber layer may form the walls to support portions of a subsequently deposited top hat layer. In one example, pillars may also be formed in the first layer of the photo definable polymer. For example, the pillars may be formed via a masking, photolithography, and etching processes. The pillars may provide a surface to bond to an initial unsupported top hat layer portion that is formed, as discussed above. The bond may provide more support to the initial unsupported top hat layer portion, and as such may reduce occurrences of damage to the top hat layer when adhesive tape applied to the slotted portion is removed. 
     At block  612 , the method  600  deposits a second layer of the photo definable polymer over the first layer of the photo definable polymer. For example, the second layer of the photo definable polymer may be pushed onto the previously deposited chamber layer using a plastic film to form a top hat layer. The top hat layer may be much thinner than the chamber layer. 
     In one example, the portions of the top hat layer that rest on the remaining walls of the chamber layer may form supported or rigid portions of the top layer. The portions of the top hat layer that sit over a void formed in the chamber layer may form unsupported portions of the top hat layer. 
     At block  614 , the method  600  may apply photolithography and etching steps to form openings in the second layer of the photo definable polymer over each printing fluid ejection chamber and to form an initial unsupported top hat layer portion that is tapered. For example, the initial unsupported top hat layer portion may be formed with the first end at an initial width. The side walls of the initial unsupported top hat layer portion may gradually move away from one another to form a second end having a second width. The second width may be greater than the first width. The second width may be a desired width of the top hat layer of the printhead die. The chamber layer may also be etched to have an end that has a tapered portion that matches the shape of the initial unsupported top hat layer portion in block  610 . 
     The side walls may gradually move away from one another in a regular form at approximately 45 degrees. In another example, the side walls may move away in an irregular form. The side walls may be straight, may have a curved surface, or have surface with multiple different curves, portions, and/or segments until forming the second end with the second width. At block  616 , the method  600  ends. 
     It will be appreciated that variants of the above-disclosed and other features and functions, or alternatives thereof, may be combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.