News Column

Researchers Submit Patent Application, "Control Method and Apparatus for Dispensing High-Quality Drops of High- Viscosity Material", for Approval

May 28, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- From Washington, D.C., VerticalNews journalists report that a patent application by the inventors Ciardella, Robert L. (Rancho Santa Fe, CA); Chin, Wai Ching Bessie (Rancho Santa Fe, CA); La, Duong (Rancho Santa Fe, CA), filed on December 31, 2012, was made available online on May 15, 2014.

The patent's assignee is Advanjet.

News editors obtained the following quote from the background information supplied by the inventors: "In the semiconductor, electronics and life science industries viscous fluids are frequently dispensed. The demands to miniaturize in these industries require smaller and faster deposition of viscous fluids. Non-contact dispensing, often referred to as jet dispensing, is preferred for many reasons, some of which might be the ability to dispense drops while moving above a surface, the speed of drop formation, and the minute size and precision of the drops produced. Jetting as used herein refers to non-contact dispensing as compared to contact dispensing. Contact dispensing is the process where a fluid drop on the end of a dispensing tip comes into contact with the target substrate while still in contact with the dispensing tip so that the fluid drop 'wets' or clings to the substrate and remains on the surface of the substrate as the dispensing tip pulls away. In the case of ink jet technology, inks with a viscosity very near water (50 mPas) can be jetted. Examples of viscous fluids include adhesives, fluxes, oils, lubricants, conformal coatings, paints, slurries, UV inks, proteins, and enzymes.

"As known in the industry, to produce a free flying jetted drop, energy must be imparted to the fluid which transfers enough momentum to force fluid through an orifice with the appropriate exit velocity for the fluid to break into a free flying drop. However, due to the different rheology of each fluid, the momentum transfer required and the resulting exit velocity to produce high-quality drops can be different. A high-quality drop of fluid as defined here is a drop that breaks-off cleanly (without satellite droplets separated from the main drop and without leaving behind residue that affects the succeeding drop volume or directionality) from the exit orifice and travels to the surface resulting in a single deposit of fluid on the surface. Given a specific amount of momentum transfer, one fluid can generate high-quality drops but a different fluid can generate poor quality drops, drops that accumulate on the nozzle tip or even fail to generate a drop. Poor quality drops could be caused by small 'satellite' droplets that separate from the main drop and form multiple deposits on the surface. Or, poor quality drops could be a result of excessively high exit velocity of the drop which can hit the surface and form splattered droplets surrounding the main drop. In both cases, the resulting jetted drop would not be considered high-quality, nor would the failure to generate an expected drop be considered high-quality. Other measures of high-quality drops could be the repeatability of the drop size, shape of the drop, or other measures. There is thus a need for a method and apparatus to precisely measure, adjust, and control the transfer of momentum to the fluid, and/or the resulting drop exit velocity that would be beneficial for producing repeatable, high-quality jetted drops of viscous fluid. Advantageously, the fluid has a viscosity of greater than about 50 mPas, and more preferably a viscosity of over 150 mPas.

"Non-contact jets generally have specific construction which either restricts the flow of material through the exit orifice in the power-off state, a normally-closed construction, or allows the flow of material through the orifice in the power-off state, a normally open construction. Jetting high-viscosity fluid using a flexible diaphragm is known and described in U.S. patent application 61/293,837 and U.S. Pat. No. 5,320,250. A flexible diaphragm is preferred for many reasons, some of which might be the lack of dynamic fluid seals and ease of cleaning. However, the normally-open construction can allow the fluid to drip from the orifice when the power to the jet is shut off which can cause a loss of fluid and require the time and expense of clean up. There is thus a need for a method and apparatus to close the fluid path automatically when the power is shut off.

"When jetting fluid with a flexible diaphragm, the diaphragm material should be chemically compatible with the fluid being jetted. Some chemically aggressive fluids can have an adverse effect on an elastomeric diaphragm usually noted by swelling of the diaphragm material. If swelling occurs, the diaphragm can deflect into the jetting chamber and restrict the flow of fluid into the jetting chamber or to reduce the chamber volume. If flow is restricted or the chamber volume reduced, the quality of the jetted drop can be adversely affected. There is thus a need for a way to determine if the diaphragm material has swollen and has deflected into the jetting chamber. Additionally, the overall life of the diaphragm can be compromised by swelling. There are chemically inert materials that can be used as a diaphragm; however, the cost of these chemically inert materials can be very expensive. There is thus a need for a way to use a low-cost diaphragm material with aggressive fluids and to also minimize the effect of swelling."

As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "It is the objective of this invention to provide a non-contact jetting method and apparatus to jet high-quality drops of viscous fluid.

"It is a further objective of this invention to determine the amount of momentum transferred to the fluid during the jetting process and use this information to produce high-quality drops.

"It is a further objective of this invention to provide a method to adjust the momentum transfer to produce high-quality drops of viscous fluid.

"It is a further objective of this invention to provide a method to measure and adjust the drop exit velocity to produce high-quality drops of viscous fluid.

"It is a further objective of this invention to measure if the diaphragm has deflected into the jetting chamber and restricts the flow of fluid into the jetting chamber or reduces the usable volume of the jetting chamber.

"It is further an objective of this invention to provide a method to determine if the diaphragm has been adversely affected by aggressive fluids.

"It is a further objective of this invention to provide a means to increase the life of a flexible diaphragm when using chemically aggressive fluids.

"It is a further objective of this invention to provide a positive shut-off mechanism for a normally-open flexible diaphragm jetting apparatus which will impede the flow of fluid through the orifice when the power is off.

"One or more of these objectives and other advantages may be achieved by providing a viscous jetting apparatus for jetting high-quality minute quantities of viscous fluid as described further in this disclosure.

"The jetting apparatus may include a pressurized fluid source, a jetting chamber, a compliant diaphragm containing a contoured insert, an inlet channel, an outlet path, an orifice, a supporting structure, a pressure source, an adjustable impact element, a pair of sensing elements, and a positive shutoff actuator. The jetting chamber has as its top wall a suitably flexible, compliant diaphragm. The diaphragm is contained between the jetting chamber and the supporting structure and is easily removed for cleaning or replacement. The jetting chamber communicates with a dispensing orifice by means of an outlet conduit. The jetting chamber is connected to a fluid inlet channel which communicates with a pressurized viscous fluid source. With the impact element retracted, fluid flows from the fluid source unimpeded through the inlet channel and into the jetting chamber. The diaphragm is then forced to rapidly deform away from the supporting structure by an impact element. The diaphragm deforms into the jetting chamber and displaces an amount of fluid contained within the jetting chamber until a central protrusion of the diaphragm insert mates with the top of the outlet chamber and ejects a drop of fluid that breaks away from the dispensing orifice and flies to a substrate. The impact element is retracted and the diaphragm is urged away from the outlet chamber aided by the fluid pressure and by the restorative force of the deformed diaphragm. The diaphragm returns to its initial starting position which optionally is flat, but can be biased into or away from the jetting chamber. Fluid from the source enters the jetting chamber and flows past the central protrusion of the diaphragm insert and enters the outlet conduit to refill the volume of fluid which has been ejected. The volume of fluid that enters the jetting chamber is a function of the fluid flow rate and the time the impact element is retracted. Once the appropriate volume has refilled the jetting chamber, the impact element will cycle and eject another drop of fluid.

"The quality of the ejected drop is dependent upon several factors, three of which are the rheology of the fluid, the drop exit velocity, and the level of momentum transferred to the fluid. A method of calibration is advantageously provided that may include setting an impact gap, measuring and/or changing the distance the impact element travels before it impacts the diaphragm, ejecting a drop or series of drops, measuring the drop velocity, inspecting the quality of the ejected drop or drops, and selecting a preferred impact gap to ensure high-quality, reliable jetting. The method of calibration can be repeated and used to determine fluid specific preferred impact gaps and the resulting preferred drop velocities and momentum transfer parameters for a multitude of different fluids. These fluid specific parameters can be stored in electronic, optical or other accessible memory associated with the equipment and used each time a specific fluid is jetted, drastically reducing the required set-up time for each fluid. Optionally, but preferred, a pair of sensing elements can be used to determine the initial impact gap automatically. Once the impact element starts to move, the sensing elements measure the change in position of a location on the impact element. Using this information the velocity of the impact element can be determined. Using this velocity and knowing the mass of the impact element, the amount of momentum transfer can be calculated. This resulting value of momentum transfer which produces the highest quality drops can be used to adjust the position of the impact element for reliable high-quality jetting. The method could include the additional step of measuring the velocity of the impact element during operation, comparing the actual velocity to the preferred velocity, and making adjustments to the speed of the impact element or the distance of the impact gap so reliable high-quality jetting is maintained. The method may also include adjusting the gap and/or velocity until the desired quality of drops is achieved. The method may also include setting an alarm to notify the user that the current values of momentum transfer or impact gap are not at the preferred values.

"Alternatively, a calibration method using at least one and preferably a pair of sensing elements (or an emitter and detector) to determine the drop exit velocity can be used to determine the preferred parameters for high-quality jetting. Sensing elements can be located below the nozzle orifice and in line with the drop path to detect when a drop passes by the sensing element. Along with signals from the jet control electronics, the time interval between when a drop was commanded to eject and the time a drop is detected by the sensing elements can be determined. Using this time interval information along with distance between the orifice and the sensors, the velocity of the drop can be determined. By varying the impact momentum transfer to the fluid resulting in different exit velocities, a preferred drop velocity for high-quality drops can be determined. Using the preferred value of the drop exit velocity which produces the highest quality drops, the preferred position or speed of the impact element for reliable high-quality jetting can be determined. The method could include the additional step of measuring the drop velocity during operation, comparing the measured velocity to the preferred velocity, and making adjustments to the speed of the impact element or the distance of the impact gap to alter the drop velocity so reliable high-quality jetting is maintained. The method may also include adjusting the gap velocity until the desired quality of drops is achieved. The method may also include setting an alarm to notify the user that the current value of drop velocity is not at the preferred value.

"There is also advantageously provided a power-off, positive shut-off means. To ensure fluid does not leak out the orifice when power is shut off, a positive shutoff actuator is automatically engaged when power to the jetting apparatus is turned off. The actuator deflects the impact element which forces the diaphragm to mate with the top of the outlet conduit impeding the flow of fluid out the orifice and also preferably shutting off flow into the jetting chamber.

"There is also advantageously provided a jetting apparatus for jetting chemically aggressive high-viscosity fluids that may include a jetting chamber, a compliant diaphragm containing a contoured insert, a diaphragm spring, a pressure source, an inlet channel, an outlet path, an orifice, a supporting structure, an adjustable impact element, sensing elements, and a diaphragm spring. The diaphragm with a diaphragm spring affecting the contoured diaphragm insert is contained between the jetting chamber and the supporting structure and is easily removed for cleaning or replacement. The jetting chamber is in fluid communication with a dispensing orifice by means of an outlet conduit. The jetting chamber is connected to a fluid inlet channel which is in fluid communication with a pressurized viscous fluid source. Fluid flows from the fluid source through the inlet channel and into the jetting chamber. The diaphragm is forced to rapidly deform away from the supporting structure and toward the outlet orifice by an impact element. The diaphragm and central protrusion deform into the jetting chamber displaces an amount of fluid contained within the jetting chamber until the central protrusion mates with the top of the outlet chamber and ejects a drop of fluid that breaks away from the dispensing orifice and flies to a substrate. The impact element is retracted and the diaphragm starts to relax and return to its initial flat position.

"However, if a chemically aggressive fluid is used, the diaphragm material can react with the fluid and cause local swelling in the area of the jetting chamber. If swelling occurs, the diaphragm would no longer be able to return to its relaxed flat position and the swelling may cause the diaphragm or central protrusion to occupy a portion of the chamber volume within the cavity formed by the chamber sidewalls. The flow gap, the distance between the tip of the central protrusion of the diaphragm insert and the top of the outlet conduit, will be decreased by swelling. If the flow gap is decreased due to the local swelling of the diaphragm, the quality of the jetted drops can be adversely affected. However, the addition of a diaphragm spring or springs can force the diaphragm back to its initial flat position thus mitigating the adverse effect of the local swelling and maintaining the desired flow gap.

"Additionally, the sensing elements as described above to measure the impact gap can also be used to determine if the flow gap has changed. The method of determining if the flow gap has changed advantageously includes setting a preferred impact gap as described above, measuring the distance of the impact gap during operation, comparing the actual gap to the preferred gap, and alerting the user to inspect or replace the diaphragm or adjust the equipment to achieve desired drop quality.

BRIEF DESCRIPTION OF THE DRAWINGS

"The structure, operation, and advantages of the presently preferred embodiments disclosed herein will be better understood upon consideration of the following description taken in conjunction with the accompanying drawings, in which like numbers refer to like parts throughout, and in which:

"FIG. 1a is a side view in cross section of an the jetting chamber assembly utilizing a flexible diaphragm with a contoured diaphragm insert attached so it protrudes through the diaphragm being deformed by an impact element and is in a condition just after a drop of viscous fluid has been jetted;

"FIG. 1b is a side view in cross section of an the jetting chamber assembly utilizing a flexible diaphragm with a contoured diaphragm insert attached so it protrudes through the diaphragm in a relaxed condition with an impact element retracted;

"FIG. 2a is a side view showing a diaphragm with an integral contoured central protrusion;

"FIG. 2b is a bottom view of the diaphragm of FIG. 2a;

"FIG. 2c is a top view showing a flexible diaphragm with a dual-material contoured diaphragm insert so the insert protrudes through the diaphragm and sealing features;

"FIG. 2d is a sectioned side view of the diaphragm of FIG. 2c, through the middle of FIG. 2c;

"FIG. 2e is a bottom view of the flexible diaphragm of FIG. 2c;

"FIG. 3a is a side view in cross section of an embodiment of a viscous jetting apparatus utilizing a flexible diaphragm with a contoured diaphragm insert attached so it protrudes through the diaphragm, an adjustable impact element, sensor elements, and an automatic positive shut-off actuator;

"FIG. 3b is an enlarged view of a portion of FIG. 3a showing the impact element adjusted to allow for maximum momentum transfer;

"FIG. 3c is an enlarged side view in cross section showing the adjusting lever rotated and pushing the initial starting location of the impact element toward the diaphragm thereby reducing the impact gap and resulting in a low value of momentum transfer;

"FIG. 3d is a further enlarged side view in cross section to better show internal sensing elements viewing an impact gap which comprises the distance between the bottom of the impact element and the top of the diaphragm insert, by way of a viewing channel;

"FIG. 3e is an enlarged side view in cross section of a further embodiment showing external sensing elements viewing an impact gap which is the distance between the bottom of the impact element and the top of the diaphragm insert, by way of a viewing channel;

"FIG. 3f is an enlarged side view in cross section of a further embodiment showing external sensing elements viewing a drop after it is ejected from the orifice to determine the time interval between the command to eject a drop and the time the sensing element detects the drop;

"FIG. 4a is an enlarged side view in cross section of a viscous jetting apparatus showing the impact element adjusted to allow a for a medium level of energy transfer, and sensing elements that can measure the positions of both the bottom of the impact element, the top of the diaphragm, and the velocity of the impact element when moving;

"FIG. 4b is an enlarged side view in cross section of a viscous jetting apparatus showing the impact element and sensing elements after it has deflected the diaphragm and ejected a drop of fluid;

"FIG. 4c is a side view in cross section of a nozzle plate assembly showing a replaceable seat insert and orifice insert;

"FIG. 5a is a side view in cross section of a viscous jetting apparatus in a power-off condition showing the impact element being deflected by the shut-off actuator spring and deflecting the diaphragm so it mates with the top of the outlet conduit and impedes the flow of fluid out the orifice;

"FIG. 5b is an enlarged side view, in cross section of FIG. 5a showing the fully deflected diaphragm impeding the flow of fluid out the orifice;

"FIG. 6 is an enlarged side view, in cross section of a jetting apparatus with a swollen, fully relaxed compliant diaphragm with a contoured diaphragm insert, an inlet conduit recessed in the nozzle plate, and an impact element in a retracted position;

"FIG. 7a is a side view showing a diaphragm with a two-piece contoured metal diaphragm insert having a diaphragm spring attached to the side of the diaphragm that is in contact with the jetted fluid during use;

"FIG. 7b is a bottom view of the diaphragm of FIG. 7a;

"FIG. 7c is a top view showing a diaphragm with a two-piece contoured metal diaphragm insert with a diaphragm spring attached to the side of diaphragm that is not in contact with the jetted fluid during use;

"FIG. 7d is a side view of the diaphragm of FIG. 7c;

"FIG. 8a is a side view, in cross section of a jetting apparatus with a swollen fully relaxed compliant diaphragm with a top side diaphragm spring attached to a dual-material diaphragm insert and pulling the diaphragm back to the flat condition maintaining the distance between the contoured feature of the diaphragm insert and the top of the outlet conduit;

"FIG. 8b is an enlarged side view, in cross section of a portion of FIG. 7a showing the diaphragm insert;

"FIG. 9a is a side view, in cross section of a jetting apparatus with a swollen and fully relaxed compliant diaphragm with a bottom side diaphragm spring attached to a dual-material diaphragm insert and pushing the diaphragm back to the flat condition and thereby maintaining the distance between the contoured feature of the diaphragm insert and the top of the outlet conduit; and

"FIG. 9b is an enlarged side view, in cross section of FIG. 8a showing the diaphragm insert"

For additional information on this patent application, see: Ciardella, Robert L.; Chin, Wai Ching Bessie; La, Duong. Control Method and Apparatus for Dispensing High-Quality Drops of High- Viscosity Material. Filed December 31, 2012 and posted May 15, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=5622&p=113&f=G&l=50&d=PG01&S1=20140508.PD.&OS=PD/20140508&RS=PD/20140508

Keywords for this news article include: Advanjet, Electronics.

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