Abstract:
A microdeposition system includes a printhead carriage that includes N rows of nozzles and that moves along a first axis; a stage that holds a substrate; and a maintenance station located at a position along the first axis that is past an edge of the substrate. The N rows of nozzles selectively deposit droplets of fluid manufacturing material onto the substrate. The maintenance station includes a capping station and an ultrasonic cleaning station located in a middle of the capping station. N is an integer greater than one.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/289,696, filed on Dec. 23, 2009. The disclosure of the above application is incorporated herein by reference in its entirety. 
     
    
     FIELD 
       [0002]    The present disclosure relates to inkjet printing and more particularly to an ultrasonic cleaning station for inkjet printing devices. 
       BACKGROUND 
       [0003]    The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. 
         [0004]    Manufacturers have developed various techniques for fabricating microstructures that have small feature sizes. The microstructures may form one of more layers of an electronic circuit. Examples of these structures include light-emitting diode (LED) display devices, polymer LED (PLED) display devices, organic LED (OLED) devices, liquid crystal display (LCD) devices, and printed circuit boards. Many of these manufacturing techniques are relatively expensive to implement and require high production quantities to amortize the cost of the fabrication equipment. 
         [0005]    One technique for forming microstructures on a substrate is screen printing. During screen printing, a fine mesh screen is positioned on the substrate. Fluid material is deposited through the screen and onto the substrate in a pattern defined by the screen. Screen printing therefore causes contact between the screen and the substrate. Contact also occurs between the screen and the fluid material, which contaminates both the substrate and the fluid material. 
         [0006]    While screen printing is suitable for forming some microstructures, many manufacturing processes do not allow contamination of the substrate by the screen. Therefore, screen printing is not a viable option for the manufacture of certain microstructures. For example, polymer light-emitting diode (PLED) display devices may require a contamination-free manufacturing process. 
         [0007]    Certain polymeric substances can be used to manufacture diodes that generate visible light of different wavelengths. Using these polymers, display devices having pixels with sub-components of red, green, and blue can be created. PLED fluid materials enable full-spectrum color displays and require very little power to emit a substantial amount of light. PLED displays can be used in various applications, including televisions, computer monitors, PDAs, other handheld computing devices, cellular phones, etc. PLED technology may also be used for manufacturing light-emitting panels that provide ambient lighting for office, storage, and living spaces. One obstacle to the widespread use of PLED display devices is the difficulty and expense of manufacturing PLED display devices. 
         [0008]    Photolithography is another manufacturing technique that is used to manufacture microstructures on substrates. Photolithography may also be incompatible with PLED display devices. Manufacturing processes using photolithography generally involve the deposition of a photoresist material onto a substrate. The photoresist material is cured by exposure to light. A patterned mask is therefore used to selectively apply light to the photoresist material. Photoresist that is exposed to the light is cured and unexposed portions are not cured. The uncured portions can be removed from the substrate while the cured portions remain. 
         [0009]    An underlying surface of the substrate is exposed through the removed photoresist layer. Another material is then deposited onto the substrate through the opened pattern on the photoresist layer, followed by the removal of the cured portion of the photoresist layer. 
         [0010]    Photolithography has been used successfully to manufacture many microstructures, such as traces on circuit boards. However, photolithography contaminates the substrate and the material formed on the substrate. Photolithography may not be compatible with the manufacture of PLED displays because the photoresist contaminates the PLED polymers. In addition, photolithography involves multiple steps for applying and processing the photoresist material. The cost of the photolithography process can be prohibitive when relatively small quantities are to be fabricated. Further, expensive PLED material may be lost when it is deposited on cured photoresist that is later removed. 
         [0011]    Spin coating has also been used to form microstructures. Spin coating involves rotating a substrate while depositing fluid material at the center of the substrate. The rotational motion of the substrate causes the fluid material to spread evenly across the surface of the substrate. Spin coating is also an expensive process because a majority of the fluid material does not remain on the substrate. In addition, the size of the substrate is limited by the spin coating process to less than approximately 12″, which makes spin coating unsuitable for larger devices such as PLED televisions. 
       SUMMARY 
       [0012]    A microdeposition system includes a printhead carriage that includes N rows of nozzles and that moves along a first axis; a stage that holds a substrate and that moves the substrate along a second axis that is perpendicular to the first axis, and a maintenance station located at a position along the first axis that is past an edge of the substrate. N is an integer greater than one. The N rows of nozzles selectively deposit droplets of fluid manufacturing material onto the substrate. 
         [0013]    In other features, the maintenance station includes N capping chambers arranged in two groups of N/2 capping chambers. The N capping chambers simultaneously immerse the N rows of nozzles in one of a solvent and a vapor rich environment of the solvent. The maintenance station also includes an ultrasonic cleaning station located between the two groups of N/2 capping chambers. The printhead carriage rotates between first and second orientations. Each of the N rows of nozzles is parallel to the first axis when the printhead carriage is in the first orientation. Each of the N rows of nozzles is parallel to the second axis when the printhead carriage is in the second orientation. The printhead carriage rotates to the second orientation for maintenance by the maintenance station. 
         [0014]    In further features, the ultrasonic cleaning station includes a water tank holding deionized water; ultrasonic transducers mounted to an external bottom surface of the water tank that apply ultrasonic vibrations to the deionized water; and an inner trough that is partially submerged in the water tank. The inner trough is filled with the solvent, and selectively immerses one of the N rows of nozzles in the solvent. The water tank includes a temperature sensor that measures a temperature of the deionized water. The ultrasonic transducers are deactivated when the temperature of the deionized water is greater than a threshold. 
         [0015]    In other features, the maintenance station includes a blotting station located past the N capping chambers along the first axis. The blotting station includes a feed roller that dispenses blotting material; a waste roller that winds up the blotting material; and a spray bar that moves perpendicular to the first axis and deposits N lines of the solvent on the blotting material. 
         [0016]    A microdeposition system includes a printhead carriage that includes N rows of nozzles and that moves along a first axis; a stage that holds a substrate; and a maintenance station located at a position along the first axis that is past an edge of the substrate. The N rows of nozzles selectively deposit droplets of fluid manufacturing material onto the substrate. The maintenance station includes a capping station and an ultrasonic cleaning station located in a middle of the capping station. N is an integer greater than one. 
         [0017]    In other features, the stage moves the substrate along a second axis that is perpendicular to the first axis. The printhead carriage rotates between first and second orientations. Each of the N rows of nozzles is parallel to the first axis when the printhead carriage is in the first orientation. Each of the N rows of nozzles is parallel to the second axis when the printhead carriage is in the second orientation. For maintenance by the maintenance station, the printhead carriage rotates to the second orientation. For depositing the droplets on the substrate, the printhead carriage rotates to a printing orientation that is adjustable between the first orientation and a predetermined orientation. The predetermined orientation is between the first orientation and the second orientation. 
         [0018]    In further features, the capping station includes N capping chambers. The N capping chambers simultaneously immerse the N rows of nozzles in one of a fluid and a vapor rich environment of the fluid. The fluid includes at least one of a solvent and the fluid manufacturing material. The ultrasonic cleaning station receives one of the N rows of nozzles at a time. When the one of the N rows of nozzles is placed in the ultrasonic cleaning station, remaining rows of the N rows of nozzles are outside of the N capping chambers. 
         [0019]    In other features, the printhead carriage moves down in a direction perpendicular to the substrate to place the one of the N rows of nozzles into the ultrasonic cleaning station. The printhead carriage moves down in the direction perpendicular to the substrate to immerse the N rows of nozzles in the N capping chambers. When the one of the N rows of nozzles is placed in the ultrasonic cleaning station, one of the remaining rows of the N rows of nozzles is located between the ultrasonic cleaning station and one of the N capping chambers, and others of the remaining rows of the N rows of nozzles are located outside of the capping station. The N capping chambers are arranged in two groups of N/2 capping chambers. The ultrasonic cleaning station is located between the two groups of N/2 capping chambers. 
         [0020]    In further features, the ultrasonic cleaning station includes a water tank that holds water; ultrasonic transducers that apply ultrasonic vibrations to the water; and an inner trough that is filled with solvent and that receives at least one of the N rows of nozzles. The ultrasonic vibrations are transferred from the water to the solvent. The inner trough is partially submerged in the water tank. The ultrasonic transducers are mounted to an external bottom surface of the water tank. The ultrasonic cleaning station further includes a temperature sensor located in the water tank that measures a temperature of the water. The ultrasonic transducers are deactivated when the temperature of the water is greater than a threshold. 
         [0021]    In other features, the maintenance station includes a blotting station that is located at a position along the first axis that is past the capping station. The blotting station moves up along an axis perpendicular to the substrate to engage the N rows of nozzles. The blotting station moves down along the axis perpendicular to the substrate to allow use of the ultrasonic cleaning station. The blotting station moves down along the axis perpendicular to the substrate to allow manual maintenance of the N rows of nozzles. 
         [0022]    In further features, the blotting station includes a feed roller that dispenses blotting material; a waste roller that winds up the blotting material; and a spray bar that moves perpendicular to the first axis and deposits a line of solvent on the blotting material. The spray bar deposits N lines of the solvent including the line on the blotting material. 
         [0023]    Further areas of applicability of the present disclosure will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0025]      FIG. 1  is an isometric view of an example implementation of a microdeposition system according to the principles of the present disclosure; 
           [0026]      FIG. 2  is a simplified top view of an example implementation of a microdeposition system according to the principles of the present disclosure; 
           [0027]      FIG. 3  is an isometric view of an example pack of printhead modules according to the principles of the present disclosure; 
           [0028]      FIGS. 4A-4C  are partial side views of an example maintenance station showing relative positions of printhead modules according to the principles of the present disclosure; 
           [0029]      FIG. 5  is an isometric view of an example maintenance station according to the principles of the present disclosure; 
           [0030]      FIG. 6A  is an isometric view of an example ultrasonic cleaning station according to the principles of the present disclosure; 
           [0031]      FIG. 6B  is an exploded isometric view of an example ultrasonic cleaning station according to the principles of the present disclosure; and 
           [0032]      FIG. 7  is a functional block diagram of fluid control for an example ultrasonic cleaning station according to the principles of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0033]    The following description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical or. It should be understood that steps within a method may be executed in different order without altering the principles of the present disclosure. 
         [0034]    The terms “fluid manufacturing material” and “fluid material,” as defined herein, are broadly construed to include any material that can assume a low viscosity form and that is suitable for being deposited, for example, from a microdeposition head onto a substrate for forming a microstructure. Fluid manufacturing materials may include, but are not limited to, light-emitting polymers (LEPs), which can be used to form polymer light-emitting diode display devices (PLEDs and PolyLEDs). Fluid manufacturing materials may also include plastics, metals, waxes, solders, solder pastes, biomedical products, acids, photoresists, solvents, adhesives, and epoxies. The term “fluid manufacturing material” is interchangeably referred to herein as “fluid material.” 
         [0035]    The term “deposition,” as defined herein, generally refers to the process of depositing individual droplets of fluid materials on substrates. The terms “let,” “discharge,” “pattern,” and “deposit” are used interchangeably herein with specific reference to the deposition of the fluid material from a microdeposition head, for example. The terms “droplet” and “drop” are also used interchangeably. 
         [0036]    The term “substrate,” as defined herein, is broadly construed to include any material having a surface that is suitable for receiving a fluid material during a manufacturing process such as microdeposition. Substrates include, but are not limited to, glass plate, pipettes, silicon wafers, ceramic tiles, FR-4 and other printed circuit board materials, rigid and flexible plastic, and metal sheets and rolls. In certain embodiments, a deposited fluid material itself may form a substrate, as the fluid material itself also includes surfaces suitable for receiving a fluid material during manufacturing, such as, for example, when forming three-dimensional microstructures. 
         [0037]    The term “microstructures,” as defined herein, generally refers to structures formed with a high degree of precision, and that are sized to fit on a substrate. Because the sizes of different substrates may vary, the term “microstructures” should not be construed to be limited to any particular size and can be used interchangeably with the term “structure.” Microstructures may include a single droplet of a fluid material, any combination of droplets, or any structure formed by depositing the droplet(s) on a substrate, such as a two-dimensional layer, a three-dimensional architecture, and any other desired structure. 
         [0038]    The microdeposition systems referenced herein perform processes by depositing fluid materials onto substrates according to user-defined computer-executable instructions. The term “computer-executable instructions,” which is also referred to herein as “program modules” or “modules,” generally includes routines, programs, objects, components, data structures, or the like that implement particular abstract data types or perform particular tasks such as, but not limited to, executing computer numerical controls for implementing microdeposition processes. 
         [0039]    Program modules may be stored on any non-transitory, tangible computer-readable media, including, but not limited to RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium capable of storing instructions or data structures and capable of being accessed by a general purpose or special purpose computer. 
         [0040]    Referring now to  FIG. 1 , a microdeposition system  100  includes a printhead carriage  104  that slides along beams  108 . For example only, the beams  108  may be constructed from granite. The direction of travel of the printhead carriage  104  may be called the x axis. The printhead carriage  104  includes one or more rows of nozzles that deposit a fluid manufacturing material on a substrate  112 . For example only, the substrate  112  may be a sheet of glass and may be a component of a PLED video monitor or television. 
         [0041]    The substrate  112  may be secured by a chuck, which may hold the substrate  112  using a vacuum. The substrate  112  may translate back and forth along the y axis, which is perpendicular to the x axis. For example only, the printhead carriage  104  may align the rows of nozzles to be parallel to the x axis. As the substrate  112  moves along the y axis, the rows of nozzles selectively deposit fluid manufacturing material onto the substrate  112 . The rows of nozzles may be unable to cover the entire substrate  112  in one pass. The printhead carriage  104  may therefore translate to another position along the x axis. The substrate  112  will then move along the y axis again to print the next pass. 
         [0042]    Alternatively, the printhead carriage  104  may print while moving along the x axis. The substrate  112  would then translate to a new position along the y axis after each pass of the printhead carriage  104  is completed. The nozzles in the printhead carriage  104  may be periodically maintained to ensure uniform dispensing of droplets. In various implementations, nozzle maintenance may be performed when the substrate  112  is being loaded into the microdeposition system  100  and/or when the substrate  112  is being unloaded from the microdeposition system  100 . 
         [0043]    A nozzle maintenance station  116  may be located further along the x axis outside of the area where printing takes place. If instead the nozzle maintenance station  116  were positioned at a location where printing was performed, such as at location  120 , it may be necessary to move the nozzle maintenance station  116  below the plane of the substrate  112  in order to avoid interfering with printing. 
         [0044]    There may be packaging constraints regarding how much room is available below the plane of the substrate. For example, portions of the chuck that holds the substrate  112  and support structures for the microdeposition system  100  may be in the way. In addition, when the nozzle maintenance station  116  would be raised to perform nozzle maintenance, loading of a new substrate may be blocked. For these reasons, the nozzle maintenance station may be located at the end of the x axis movement of the printhead carriage  104 , past the area where printing takes place. 
         [0045]    The x axis structures, including the beams  108 , may need to be extended to allow for this additional x axis movement of the nozzle maintenance station  116  beyond the length needed for printing. As the length of the x axis structures increases, the overall cost, size, and weight of the microdeposition system  100  increases. The present disclosure describes techniques for reducing additional x axis travel. 
         [0046]    Referring now to  FIG. 2 , a simplified top view of the microdeposition system  100  is shown. The nozzle maintenance station  116  includes a capping station  204  and a blotting station  208 . The capping station  204  may include troughs where the nozzles can be soaked to prevent the nozzles from drying out. The nozzles may be immersed in fluid or may be placed in a vapor rich environment above the fluid. 
         [0047]    The capping station  204  may also seal the nozzles to prevent air movement from drying the nozzles. In addition, manufacturing fluids and/or solvent may be jetted from the nozzles into the capping station. This may be performed to clean the nozzles and/or when changing deposition fluids. In addition, droplet analysis may be performed while jetting droplets into the capping station  204 . 
         [0048]    For example, measurements regarding the speed, trajectory, size, and shape of droplets may be made. Deviations from desired values may be compensated for electronically and/or may result in cleaning procedures and/or other remedial measures. For example only, nozzle firing timing may be adjusted to compensate for deviations in droplet trajectory or speed. For example only, a cleaning procedure may be performed on the nozzles by the blotting station  208 . 
         [0049]    One or more nozzles may contact a blotting surface on the blotting station  208 . The blotting station  208  may wipe the nozzles by moving the blotting surface while the nozzles are in contact with the blotting surface. For example only, a roll of blotting material may be dispensed from a feed roller and wound up by a waste roller. Solvent may be deposited on the blotting material to perform a wet wipe of the nozzles. 
         [0050]    Certain manufacturing fluids may contaminate the nozzles to an extent that the contamination is not removed by the capping station  204  and the blotting station  208 . In various implementations, a fluid manufacturing material may be used that is not a dispersion but a mixture of discrete particles and solvent. For example, to separate pixel regions in liquid crystal display (LCD) manufacturing, spacer particles may be mixed with solvent. When this mixture is deposited on a substrate, the solvent may be removed, such as through evaporation, leaving the spacer particles on the substrate. 
         [0051]    For example only, spacer particles may include acrylic spheres with bonding agent applied, where the acrylic spheres have diameters between three and five microns. The spacer particles may tend to settle out of the solvent without continual ink circulation, sonification, and filtration. As such, the spacer particles may build up in low fluid flow regions or regions where natural eddy currents are present. Another cleaning station may therefore be implemented. For example, ultrasonic cleaning may release buildup of various materials in the nozzles. However, adding an ultrasonic cleaner after the blotting station  208  would require further x axis movement of the printhead carriage  104 . 
         [0052]    Referring now to  FIG. 3 , a pack  304  may include multiple printhead modules  308 . Each printhead module  308  may include multiple nozzles. For example only, the pack  304  may include six printhead modules  308 . Each of the printhead modules  308  may include  128  nozzles. An example implementation of the pack  304  would therefore have 6*128 (768) nozzles that are substantially colinear. Fluid for each of the printhead modules  308  may be received from a multiple-port fluid connector  312 . Nozzle firing waveforms may be received via ribbon cable headers  316 , which may be located at both ends of the pack  304 . 
         [0053]    Referring back to  FIG. 2 , an example implementation of the printhead carriage  104  may include four of the packs  304 . Each of the packs is shown with six printhead modules, although more or fewer may be present. The packs  304  may be able to rotate 90 degrees, so that the rows of nozzles are perpendicular to the y axis (the direction of substrate travel) for printing and parallel to the y axis for maintenance. In addition, intermediate angles may be used to change the pitch of the nozzles with respect to the moving substrate.  FIG. 2  shows the rows of nozzles being parallel to the y axis for maintenance. 
         [0054]    When depositing solvent-suspended particles, such as spacer particles, the nozzles may be cleaned after each substrate is printed. In order to minimize production time, ultrasonic cleaning of the nozzles may be performed during the time it takes for one substrate to be unloaded and another to be loaded. 
         [0055]    In various implementations, there may be enough time to perform four ultrasonic cleaning operations. Each of the packs may therefore be cleaned sequentially. This reduces the size of the ultrasonic cleaning assembly by approximately three-quarters. However, in order to create enough clearance for the other three packs while one pack is being cleaned, the ultrasonic cleaning station may still need to be positioned further out along the x axis. As shown in  FIGS. 4A-4C , appropriately designing the spacing of the packs may allow for an ultrasonic cleaning station  212  to be located inside of the capping station  204 . 
         [0056]    Referring now to  FIG. 4A , a simplified side view of the capping station  204  and the ultrasonic cleaning station  212  is shown. In an implementation where four packs  304  are present, the capping station  204  may include four capping chambers  404 . Each of the packs  304  lines up with each of the capping chambers  404 . The packs  304  may be lowered into the capping chambers  404  and/or the capping chambers  404  may be raised. 
         [0057]    The ultrasonic cleaning station  212  is located between the first two of the capping chambers  404  and the second two of the capping chambers  404 . In  FIG. 4B , the printhead carriage has moved to position one of the packs  304  over the ultrasonic cleaning station  212 . In order to submerge the pack  304  into the ultrasonic cleaning station, the packs may be lowered and/or the ultrasonic cleaning station  212  may be raised. 
         [0058]    In various implementations, the printhead carriage  104  may have the ability to adjust the packs  304  up or down (along the z axis) to allow for varying thicknesses of substrate. The packs  304  can therefore be lowered into the ultrasonic cleaning station  212 . Once lowered, one of the packs  304  will be located in the void between the ultrasonic cleaning station  212  and the second pair of capping chambers  404 . The other two packs  304  are located past the capping station  204 . 
         [0059]    Similarly, when submerging a second one of the packs  304 , the first one of the packs  304  will occupy the void between the first pair of the capping chambers  404  and the ultrasonic cleaning station  212 , as shown in  FIG. 4C . Positioning of the remaining two packs  304  in the ultrasonic cleaning station  212  may be mirror images of  FIGS. 4B-4C . 
         [0060]    Referring now to  FIG. 5 , the capping chambers  404  are seen in an isometric view, with the ultrasonic cleaning station  212  located between the two sets of capping chambers  404 . Because the capping station  204  surrounds the ultrasonic cleaning station  212 , a vacuum that is applied by the capping station  204  to prevent evaporating solvent from escaping may also control evaporating solvent from the ultrasonic cleaning station  212 . Further, the capping station  204  may provide overflow trays that capture overflow from the ultrasonic cleaning station  212 . 
         [0061]    The blotting station  208  is shown in a lowered position. This lowered position may allow for manual inspection and maintenance of nozzles and nozzle assemblies. Additionally or alternatively, as one of the packs  304  is lowered into the ultrasonic cleaning station  212 , the lowered position may provide clearance for remaining ones of the packs  304 . In order to perform a blotting operation, the blotting station  208  may be raised. 
         [0062]    Blotting material  504  is drawn across the top of the blotting station. For example only, a feed roller  508  may dispense blotting material  504  and a waste roller  512  may wind up the blotting material  504 . The blotting station  208  may include a spray bar  516  that sprays solvent onto the blotting material  504 . In various implementations, the spray bar  516  may be mounted to a carriage  520  that rides along a rail  524  disposed parallel to the y axis. The spray bar  516  may spray solvent in four stripes, one for each of the packs. 
         [0063]    Referring now to  FIG. 6A , an example of an ultrasonic cleaning station  212  includes a water tank  604  coupled to ultrasonic transducers  608 . The ultrasonic transducers  608  introduce ultrasonic vibration into the water within the water tank  604 . An inner solvent trough  612  contains solvent. The solvent trough  612  is partially submerged in the water of the water tank  604 . Ultrasonic vibration of the water is transferred to the solvent within the solvent trough  612 , into which nozzles of a pack are inserted. The ultrasonic vibration and the chemical action of the solvent remove contaminants from the nozzles. 
         [0064]    The solvent trough  612  may be filled via a solvent inlet  616 , which may pass through the water tank  604 . The solvent trough  612  may be filled until solvent overflows into an overflow trough  620 . The overflow trough  620  surrounds the solvent trough  612 , and a solvent waste pipe  624  is present on each end of the overflow trough  620 . 
         [0065]    A fluid sensor  628  may be located on each of the waste pipes  624 . The fluid sensor  628  indicates when fluid is present in the waste pipe  624 . Once fluid is present in the waste pipe  624 , the solvent trough  612  is determined to be full and the supply of solvent is halted. 
         [0066]    The water tank  604  may be filled using a water fill inlet  640 . In various implementations, deionized water may be used in the water tank  604 . A loop  644  may be formed to detect the level of water present in the water tank  604 . The loop  644  may be connected to the water tank via a coupling  648 . A fluid level sensor  652  may be located near the top of the loop  644 . An outlet coupling  656  may be connected to the loop  644  and may allow overflowing water to escape to an overflow tank. In addition, the outlet coupling  656  may allow trapped air to escape from the loop  644  to allow for accurate water level readings and to prevent backpressure when filling the water tank  604 . 
         [0067]    Referring now to  FIG. 6B , an exploded view of the ultrasonic cleaning station  212  of  FIG. 6A  includes a support bracket  670 . The support bracket  670  may attach to the water tank  604  via a gasket  674 . In addition, a gasket  678  located between the solvent trough  612  and the water tank  604  may prevent water leakage and cross-contamination between the solvent and the water. 
         [0068]    Referring now to  FIG. 7 , a fluid control module  704  applies pressure, which may be positive or negative, to a solvent reservoir  708 . The solvent reservoir  708  may include an overfill sensor  710 , a full sensor  712 , and a refill sensor  714 . When the refill sensor  714  does not detect fluid presence, filling of the solvent reservoir  708  begins. Filling may continue until the full sensor  712  detects fluid presence. 
         [0069]    When the overfill sensor  710  detects fluid presence, solvent may need to be drained from the solvent reservoir  708 . For example only, the solvent reservoir  708  may output solvent to the solvent trough  612 , which may then overflow and be removed as waste. The solvent reservoir  708  may stop outputting the solvent when the full sensor  712  no longer detects fluid presence. 
         [0070]    Applying pressure to the solvent reservoir  708  may push solvent through a filter  720  and then through a check valve  724  and into the solvent trough  612 . Applying a negative pressure draws solvent from the solvent trough  612  to a second check valve  728  and then through a second filter  732  before the solvent returns to the solvent reservoir  708 . In various implementations, solvent may be removed from the solvent trough  612  when the ultrasonic cleaning station  212  is not in use. This may minimize evaporation of solvent and also allows for the solvent to be filtered by the filters  720  and  732 . 
         [0071]    Solvent overflowing into the overflow trough  620  passes by either of the first and second fluid sensors  628  before arriving at a solvent waste valve  740 . The solvent waste valve  740  may remain closed until enough solvent backs up to trip one of the fluid sensors  628 . The solvent waste valve  740  may then be opened, allowing the solvent to go to a waste collection location. Alternatively, solvent from the solvent waste valve  740  may be filtered and replaced into the solvent reservoir  708 . 
         [0072]    Water may be added to the water tank  604  via a check valve  750 . A stopcock  752  may allow water to be drained from the water tank  604  when the check valve  750  is bypassed. The level of water within the water tank  604  may be measured by a water level sensor  760  attached to an indicator tube  764 . 
         [0073]    An overflow tube  768  may be located within the water tank  604  to allow water to overflow to a water overflow reservoir  772  and also to allow air to escape from the water tank  604 . In various implementations, the overflow tube  768  and the indicator tube  764  may be implemented in a single structure, such as the loop  644  of  FIG. 6A . An ultrasound driver  780  may be driven by ultrasound amplifiers  784 , which are selectively energized by a relay  788 . A temperature sensor  792 , such as a thermistor, may check to make sure that the water temperature does not increase above a predetermined threshold. Ultrasonic energization may be stopped if the water temperature crosses this threshold. 
         [0074]    The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification, and the following claims.