CN101142677A - Aerodynamic jets of aerosol-like liquids for the fabrication of passive structures - Google Patents

Abstract

Method and apparatus for direct writing of passive structures having a tolerance of 5% or less in one or more physical, electrical, chemical, or optical properties. The present apparatus is capable of extended deposition times. The apparatus may be configured for unassisted operation and uses sensors and feedback loops to detect physical characteristics of the system to identify and maintain optimum process parameters.

Description

Aerodynamic jets of aerosol-like liquids for the fabrication of passive structures

Cross References to Related Applications

This application claims priority to U.S. Provisional Patent Application Serial No. 60/635,848, titled "Solution-Based Aerosol Jetting of Passive Electronic Structures", filed on December 13, 2004, the description of which is hereby incorporated by reference.

technical field

This application relates generally to the field of direct deposition of passive structures. More specifically, the application relates to the field of precise deposition of medium-scale passive structures on planar or non-planar targets without masks, with an emphasis on the deposition of precise resistive structures.

Background technique

Note that the ensuing discussion refers to several published documents and reference documents. The discussion of these publications is given for the context of a more complete scientific rationale and is not to be construed as an admission that these publications are prior art for purposes of determining patentability.

Various methods exist for depositing passive structures, however thick and thin film methods play a major role in depositing passive structures including but not limited to resistors or capacitors onto a variety of electronic and microelectronic targets. As an example, thick film technology typically uses a screen printing process to deposit electronic paste with line widths as small as 100 microns. Thin-film methods for printing electronic structures include vapor deposition techniques, such as chemical vapor deposition and laser-assisted chemical vapor deposition, and physical deposition techniques, such as sputtering and evaporation.

US Patent No. 4938997 discloses a method for fabricating thick film resistors on ceramic substrates, with tolerances compatible with the required microelectronic circuits. In this method, a ruthenium-based resistor material is screen printed onto a substrate and sintered at temperatures in excess of 850°C. U.S. Patent No. 6709944 discloses a method of fabricating passive structures on flexible substrates by means of ion bombardment to activate the substrate surface such as polyimide to form a substrate that can be combined with another deposited material, such as titanium. Graphite-like carbon regions thus form passive structures. US Patent No. 6713399 discloses a method of manufacturing embedded resistors on a printed circuit board. The method uses a thin film process to form embedded passive structures within recesses that have been formed in the conductive layer. The method of US Patent No. 6713399 discloses a process for reducing the large resistance variation seen in polymer thick film embedded resistors.

Although thick and thin film methods for fabricating passive structures are well developed, these processes may not be suitable for some deposition applications. Some drawbacks of thick film processes are the relatively large minimum linewidth, which is a technical characteristic, the requirement of mask usage, and the requirement of high temperature processing of deposited materials. Disadvantages of typical thin-film processes include the need to use masks, vacuum atmospheres, and multi-step photolithography processes.

In contrast to conventional methods of passive structure deposition, the M ³ D ^(R) process is a direct printing technique that does not require the use of vacuum chambers, masks or extensive post-deposition processes. Publicly known International Patent Application No. PCT/US01/14841, published as WO 02/04698 and incorporated herein by reference, discloses a method of depositing passive structures onto multiple targets using an aerosol spray, No measures are given to reduce the error of the deposited structure to an acceptable level for the manufacture of electronic components. In fact, the use of effective impactors in the invention disclosed herein eventually leads to the failure of the system due to the accumulation of particles inside the device. As a result, previously disclosed systems had a maximum run time of 15 to 100 minutes before failure, with electronic errors of approximately 10% to 30% in the deposited structure.

In contrast, the present invention can deposit passive structures with less than 5% error in conductance, resistance, capacitance, or inductance values with hours of runtime.

Contents of the invention

The present invention is an apparatus for depositing a passive structure comprising material on a target, the apparatus comprising: a sprayer for forming a suspension comprising material and a carrier gas; an exhaust flow controller for exhausting excess carrier gas; Deposition head for delivery of suspended matter in a cylindrical casing gas stream; pressure sensor transducer; cross connection to nebulizer, deposition head, exhaust flow controller and transducer, where passive The error of the ideal properties of the structure is better than about 5%. The deposition head and sprayer are preferably connected at opposite inlets of the cross fitting. The exhaust flow controller preferably exhausts excess carrier gas in a direction perpendicular to the direction of transport of suspended solids through the cross fitting. The exhaust flow controller preferably reduces the flow rate of the carrier gas.

The device preferably further comprises a processor for receiving data from said transducer, the processor determining whether a leak or blockage has occurred in the device. In this case, the device preferably further comprises a feedback loop for automatically purging the device if a blockage is detected; or automatically stopping operation of the system if a leak is detected. The apparatus preferably further comprises: a laser whose laser beam passes through the flowing suspension; and a photodiode for detecting scattered light from the laser. The laser beam is preferably perpendicular to the flow direction of the suspension and the photodiode is preferably positioned orthogonal to both the laser beam and the flow direction. The photodiode is preferably connected to a controller for automatically controlling power to the nebulizer.

The invention also relates to a method of depositing a passive structure comprising material on a target, the method comprising the steps of: atomizing the material; transporting the atomized material in a carrier gas to form a suspension; removing excess carrier gas from the suspension; monitoring the pressure of the suspension; surrounding the suspension with a jacket gas; and depositing material on the target; where the error of the ideal characteristic of the passive structure is optimized at about 5%. The method preferably further comprises the steps of determining the presence of a leak or blockage based on the pressure value, and automatically cleaning the system if a blockage occurs or automatically stopping operation if a leak occurs. The method preferably further includes the step of irradiating a laser beam into the suspension, and measuring scattered light from the laser beam. This measuring step is preferably performed by a detector positioned orthogonal to both the laser beam and the flow direction of the suspension.

The method preferably further comprises the step of varying the power used in the nebulizing step according to the amount of scattered light detected in the measuring step.

The method preferably further comprises the step of treating the material, the treating step preferably being selected from the group consisting of wetting the suspension, drying the suspension, heating the suspension, heating the deposited material, irradiating the deposited material with a laser beam and combinations thereof. The use of laser beam radiation to deposit materials preferably ensures that the linewidth of the deposited material is as small as about 1 micron. Materials deposited using laser beam radiation did not raise the average temperature of the target above the destruction threshold.

It is an object of the present invention to pre-process and/or post-process material on the fly after deposition on a target to produce physical and/or electrical properties having values in the vicinity of the bulk material.

Another object of the present invention is to provide a deposition apparatus which can extend the operating time.

An advantage of the present invention is that the deposited passive structures have conductance, resistance, capacitance or inductance values with less than 5% error.

Other purposes, advantages and novel features of the present invention, as well as further scope of application will be partly explained in the following detailed description and in conjunction with the accompanying drawings, partly will be understood by those skilled in the art after verification, or can be realized through implementation The present invention is understood. The above objects and advantages of the present invention can be realized or attained by means of the measures and combinations particularly pointed out in the appended claims.

Description of drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the invention and together with the description serve to explain the principles of the invention. The drawings are only for the purpose of illustrating preferred embodiments of the invention and are not to be construed as limiting the invention. In the attached picture:

Figure 1a is a schematic diagram of an embodiment of a preferred ^{M3D (R)} apparatus of the present invention that can extend run times and deposit passive structures with a tolerance of less than 5%.

Figure 1 b illustrates a general embodiment of a preferred ^{M3D (R)} device of the present invention, configured to have a spray propelled by compressed air.

Figure 2 is a graph illustrating the relationship between casing gas pressure and total gas flow velocity.

Figure 3a is a schematic cross-sectional view of a passive structure with terminations. The structure has a height t ₁ .

Figure 3b is a schematic illustration of Figure 3a with an additional balanced passive structure. The structure has a height t ₂ , where t ₂ >t ₁ .

FIG. 4 is a schematic diagram showing that the rightmost resistor has a larger resistance value than the middle structure according to a longer length of resistor material between pads.

Figure 5a is a schematic diagram of a resistor ladder prior to direct writing of additional passive structures.

Figure 5b is a schematic diagram of a resistor ladder illustrating how the structure is added after the backplane has been processed and other components added, adjusting the circuit after it is mostly complete.

Figure 6 is a schematic diagram of a passive structure written on the edge of a target.

Figure 7a is a schematic diagram of the final resistor linear passive path.

Figure 7b is a schematic diagram of the final resistor bend passive path.

Figure 8 is a schematic diagram of a resistor embedded in a via between two circuit layers.

FIG. 9 depicts a method for depositing a capping layer on the sidewalls and bottom of a via.

Figures 10a-c are schematic illustrations of using the ^M3D ( ^R) process in a hybrid-addition alkali-less technique to fabricate precise metal structures using etch barrier layers.

Detailed ways

Introduction and Overview

The ^{M3D( R)} process is an additive direct printing technique that operates in an atmospheric environment and eliminates the need for photolithography or vacuum deposition techniques. The method deposits passive electronic components in a predetermined pattern and uses an aerodynamically focused stream of suspension to deposit the pattern on a planar or non-planar target without the use of masks or modification of the environment. The M ³ D ^(R) method is compatible with commercially available thick film and polymer thick film adhesive compositions in the field, and can also be used with liquid precursor-based compositions, particle-based compositions, and compositions consisting of a combination of particles and liquid precursors use together. This method can also deposit multiple components on the same target layer. This capability ensures that resistive structures deposited directly on the same layer have a wide range of resistance values, ranging from below 50Ω/square to over 500KΩ/square.

The M ³ D ^(R) method can mix different components, such as a low value and a high value component, in transport, in a method where preferably multiple atomizers are used to aerosolize the two components. The aforementioned components are preferably deposited by a single deposition head, and mixing can occur during the delivery of the suspension, or when the droplets of the suspension combine on the target. This method allows automatic adjustment of the composition, allowing continuous changes in the resistance or other electrical, thermal, optical or chemical properties of the deposit from low to high values. This mixing process can also be used for glues, inks, different fluids (including but not limited to, chemical precursor solutions, electronic particle suspensions, optical, biological and. biocompatible materials, adhesives) and their combination.

As used throughout this specification and claims, "passive structure" means a structure having desired electrical, magnetic or other properties, including but not limited to conductors, resistors, capacitors, inductors, insulators, dielectrics, Suppressors, filters, varistors, ferromagnets, adhesives, and more.

The M ³ D ^TM process preferably deposits material in aerosol form. Aerosolization of most particle suspensions is preferably produced using devices powered by compressed air, such as nebulizers, however ultrasonic aerosolization can be used for particle suspensions consisting of small particles or low density particles. In this case, the solid particles may be suspended in water or an organic solvent and additives to maintain the suspension. These two spraying methods allow the generation of droplets or droplets/particles with a typical size in the range of 1 to 5 microns, but are not limited to this range.

Ultrasonic aerosolized components typically have a viscosity ranging from 1 to 10 cP. The precursor and precursor/particle components typically have a viscosity of 10 to 100 cP and are preferably aerosolized by compressed air. Components with a viscosity of 100 to 1000 cP are also preferably aerosolized by compressed air. Using suitable diluents, components with a viscosity greater than 1000 cP can be modified to a viscosity suitable for compressed air driven aerosolization.

A preferred apparatus of the present invention is shown in FIG. 1a, which can deposit passive structures with a tolerance of less than 5% and with extended runtime. Figure 1b shows a ^{M3D (R)} device configured for a spray propelled by compressed air and details the most general embodiment of the device. An inert carrier gas or fluid is preferably used to transport the aerosolized sample to the deposition module. In the case of ultrasonic atomization, the carrier gas loaded with the suspension preferably enters the deposition head immediately after the atomization process. The carrier gas may comprise compressed air, an inert gas (which may include solvent vapors), or a mixture of the two. The aerosolization process powered by compressed air requires a carrier gas flow velocity, preferably exceeding the maximum allowable gas flow velocity through the deposition head 22 . To ensure utilization of large carrier gas flow velocities (eg, approaching 0.2 to 2 liter/min), it is preferred to use effective impactors to reduce the flow velocity of the carrier gas without significant reduction of particles or droplets. The number of steps used in an effective impactor can vary and is related to the amount of carrier gas that must be removed. The gas flow is introduced into the M ³ D ^(R) deposition head where an annular flow is created consisting of an inner suspended flow surrounded by jacket gas. The co-flow configuration can focus the suspension flow to approximately one-tenth the size of the nozzle diameter.

When an annular flow is used to manufacture passive structures, the suspension flow preferably enters through holes arranged in the deposition head 22 and reaches the nozzles. The suspension-carrying air flow controller 10 preferably controls the quality of the throughput. Inside the deposition head, the suspension stream is preferably initially aligned by passing through micron-sized holes. The emerging particle stream then combines with the casing gas or fluid to form an annular distribution consisting of a carrier gas loaded with suspension inside and the casing gas or fluid outside. The cannula gas most commonly consists of compressed air or an inert gas, either or both of which may contain a modified solvent vapor content. The casing gas enters through the casing gas inlet below the suspension inlet and forms an annular flow with the suspension flow. The gas flow controller 12 preferably controls the cannula gas. The combined gas stream exits the chamber through holes aligned with the target 28 . This annular flow focuses the flow of suspension onto the target 28 and allows the deposition of features with dimensions as small as 10 microns or less. The purpose of the casing gas is to create a boundary layer that both focuses the suspended flow and prevents deposition of particles onto the bore walls. This protective effect reduces clogging of the pores.

The diameter of the emerging gas flow (and thus the width of the deposited line) is controlled by the size of the hole, the ratio of the cannula gas flow rate to the carrier gas flow rate, and the spacing between the hole and the target 28 . In a typical configuration, the target 28 is fixed on a platen which is moved in two perpendicular directions by X-Y linear steppers under computer control, allowing complex geometries to be deposited. An alternative configuration allows the deposition head 22 to move in two perpendicular directions while maintaining the target 28 in a fixed position. However, another configuration allows the deposition head 22 to be moved in one direction while the target 28 is moved in a direction perpendicular to the deposition head 22 . The process can also deposit three-dimensional structures.

In the ^{M3D( R)} process, once the sheath gas is combined with the suspension stream, the gas stream does not need to pass through more than one hole in order to deposit submicron linewidths. The ^M3D ( ^R) process typically achieves a gas flow diameter compression of close to 250 in 10 micron linewidth deposition, and over 1000 can be achieved for "single-stage" deposition. Axial compression is not used, and the gas flow typically does not reach the velocity of supersonic flow, thereby preventing the formation of turbulent flows that could result in complete compression of the gas flow.

Aerosolization and effective impact

In the preferred operation of the system of the invention detailed in Figure Ia, impingement-type compressed air powered nebulisers 32 aerosolize the material in the sample vial. The suspension-laden gas stream is delivered to a cross fitting 30 that bridges the sprayer 32 , deposition head 22 , exhaust flow controller 34 , and pressure sensing transducer 36 . The cross fitting 30 is preferably arranged such that the suspension stream inlet is opposite the suspension stream outlet. The outlet is connected to the M ³ D ^(R) deposition head. Excess carrier gas is preferably exhausted from the system at a 90° angle to the suspension input/output transfer line. A mass flow controller 34 is preferably used to control the amount of gas exhausted from the system. By helping to control the mass flow of material through the deposition head, the fluid controller is used to control the discharge flow, increasing the accuracy of the deposition process.

In an alternative embodiment, the sprayer is placed directly adjacent to the active impactor. Placing this efficient impactor near the output of the compressed air propelled nebulizer results in the deposition of larger droplets as the suspension ultimately spends less time in transport from the nebulizer to the target and undergoes reduced evaporation. The deposition of larger droplets can have a non-negligible effect on the properties of the deposited structure. In general, deposited structures formed from larger droplets showed less particle overspray and improved edge definition when compared to deposited structures from small to medium sized droplets. Shake the sprayer arbitrarily to prevent clumping of the material.

Typically, the carrier gas velocity required for compressed air to drive the spray must be reduced after the suspension is generated in order to direct the flow of the suspension into the deposition head. A limited impactor is preferably used to achieve the required reduction in carrier gas flow - from as much as 2 L/min to as little as 10 ml/min. However, the use of efficient impactors can cause the system to clog more easily, reducing the run time of the apparatus to as little as a few minutes, while undesirably reducing the tolerance of the deposited structure. For example, the device in Figure 1b can deposit carbon-based resistors in as little as 15 minutes with up to a 30% error in resistance value before failure. In contrast, the apparatus in FIG. 1 a replaces the standard ^M3D (R ⁾ effective impactor with a cross fitting 30 that removes excess carrier gas from the system while minimizing particle loss and particle accumulation with the system. The cross fitting 30 acts as an efficient impactor with not negligibly larger nozzle and collector apertures than those used with standard impactors. The use of larger nozzle and collector apertures can increase the amount of material flowing through the effective smaller flow axis of the impactor while minimizing buildup of material inside the device.

Leak/Clog Sensor

The present invention preferably uses a leak/occlusion sensor comprising a pressure transducer to monitor the pressure development at the nebulizer gas inlet and the cannula gas inlet. In normal operation, the pressure expanded within the system is related to the total gas flow rate through the system and can be calculated using a second order polynomial equation. In FIG. 2 a curve of pressure versus total volume flowing through the system is shown. If the system pressure is higher than that determined from the curve in Figure 2, non-ideal flow may have developed due to material buildup. If the pressure is too low and there is a system leak, material deposition can be suppressed or completely stopped. The second order polynomial equation representing the curve for normal operation is of the form:

P＝M ₀ +M ₁ Q+M ₂ Q ²

where P is the casing gas pressure and Q is the total flow rate. The total flow rate through the system is given by the following equation:

Q _ultrasonic ＝F _sheath +F _ultrasonic

Q _pneumatic ＝F _sheath +F _pneumatic -F _exhaust

where F is the device flow rate. The coefficients M ₀ , M ₁ and M ₂ of each deposition tip diameter are constant, but may vary according to atmospheric pressure.

This leak/occlusion sensor provides valuable system diagnostics that can allow continuous manual or automatic monitoring and control of the system. When operating in a non-selected mode, the system can be monitored for blockage and automatically cleans the system when a pressure increase above a predetermined value is detected.

smoke detection

Quantitative measurement of the amount of suspended matter produced by the nebulizer unit is critical for manual or automatic operation of the M ³ D ^(R ) system extension. Maintaining a constant aerosol density allows for precise deposition because the mass flow rate of aerosolized material delivered to the target can be monitored and controlled.

The system of the present invention preferably utilizes a smoke sensor which preferably comprises a visible wavelength laser whose laser beam is passed through the suspension output tube of the nebulizer unit. The beam is preferably oriented perpendicular to the tube axis, and the silicon photodiode is preferably arranged near the tube on an axis perpendicular to both tube and laser axes. As the laser interacts with the smoke stream passing through the tube, the light is scattered over large angles. The energy detected by the photodiode is proportional to the suspended matter density of the smoke stream. As the smoke flow rate increases, the photodiode output increases until saturation is reached, at which point the photodiode output becomes constant. Saturated smoke level conditions are preferred for constant smoke output such that constant photodiode output shows the best operating conditions.

In the feedback control loop, the output of the photodiode is sensed and can be used to determine the input power to the transducer of the ultrasonic nebulizer.

deal with

The aerosolized material components can be processed on the fly - during transport to the deposition head 22 (pre-processing) - or once deposited on the target 28 (post-processing). Pretreatment may include, but is not limited to, wet or dry suspension carrier gas or cannula gas. The wetting process can be accomplished by introducing aerosolized liquid droplets and/or vapor into the carrier gas stream. The evaporation process is preferably accomplished by evaporating the one or more solvents and additives using a heating element.

Post-processing may include, but is not limited to, using one or a combination of the following processes: (1) thermally heating the deposited structural element; (2) subjecting the deposited structural element to a reduced pressure atmosphere; or (3) The structural element is irradiated with electromagnetic radiation. Post-processing of passive structures generally requires temperatures ranging from about 25 to 1000°C. Deposits requiring solvent evaporation or cross-linking are typically processed at temperatures of about 25 to 250°C. Precursors or deposits of nano-based particles typically require processing temperatures of about 75 to 600°C, while commercially available sintered pastes require more conventional heating temperatures of about 450 to 1000°C. Commercially available polymer thick film adhesives are typically processed at temperatures of about 25 to 250°C. Workup can optionally be carried out in an oxidizing or reducing environment. To aid in the removal of solvents and other volatile additives, subjecting the deposit to a reduced pressure environment before or during the heating step may facilitate the handling of passive structures on thermally sensitive targets.

Two preferred methods of reaching the desired processing temperature are by heating the deposit and target on a heated platen or in a furnace (thermal treatment), or by irradiating the structural element with laser radiation. Laser heating of the deposit allows densification of thick film adhesives on conventional heat sensitive targets. Laser photochemical processing has been used to decompose liquid precursors to form mid to high range resistors, low to mid range dielectric films and high conductivity metals. The laser treatment and deposition processes may optionally be performed simultaneously. Simultaneous deposition and processing can be used to deposit structures that are thicker than a few microns, or to create three-dimensional structures. Further details on laser processing can be found in commonly known U.S. Patent Application Serial No. 10/952,108, entitled "Laser Processing For Heat-Sensitive Mesoscale Deposition", filed September 27, 2004, The specification and claims thereof are hereby incorporated by reference.

The heat-treated structure has a linewidth determined in part by the deposition head and deposition parameters, and the minimum linewidth is approximately 5 microns. The maximum unidirectional line width is close to 200 microns. Line widths greater than 200 microns can be obtained using grating deposition techniques. The laser-processed lines may have line widths ranging from approximately 1 to 100 microns (for structures using unidirectional deposition). Linewidths greater than 100 microns can be obtained using grating process technology. Generally, laser processing is used to densify or convert films deposited on thermally sensitive targets, such as those with a low temperature threshold of 400°C or less, or when linewidths of less than about 5 microns are desired. Deposition and treatment of the suspended stream can occur simultaneously.

Type of structure: material composition

The present invention provides a method for precisely fabricating passive structures, wherein the material components include, but are not limited to, liquid chemical precursors, inks, glues, or any combination thereof. In particular, the present invention can deposit electronic materials, including but not limited to conductors, resistors, dielectrics, and ferromagnetic materials. Metal systems include, but are not limited to, silver, copper, gold, platinum, and palladium, which are available in the form of commercially available gels. Resistor components include, but are not limited to, systems consisting of silver/glass, ruthenate, polymer thick film components, and carbon-based components. Components used to deposit capacitive structures include, but are not limited to, barium titanate, barium strontium titanate, aluminum oxide, and tantalum oxide. Inductive structures have been deposited using a manganese/zinc ferrite composition mixed with low melting temperature glass particles. The present invention can also incorporate two UV curable inks to create a final component with targeted properties, such as a specific index of refraction.

Precursors are chemical components made up of solutes or solutes dissolved in suitable solvents. The system may contain additives that alter the fluidic, chemical, physical or optical properties of the solution. The ink may consist of particles, including but not limited to metal nanoparticles or metal nanoparticles with glass inclusions, electronic material suspended in a liquid medium. Depositable pastes include, but are not limited to, commercially available paste compositions for conductor, resistive, dielectric, and inductive systems. The present invention can also deposit commercially available tacky glues.

Resistor

The silver/glass resistor composition may consist of a liquid molecular precursor for silver together with a suspension of glass particles, or silver and glass particles, or silver particles in a precursor liquid for glass. The ruthenate system may include conductive ruthenium oxide particles and insulating glass particles, ruthenium oxide particles in a glass precursor, or a mixture of ruthenium oxide precursors with glass precursors or insulating dielectric precursors. Precursor components and some precursor/particle components may have a viscosity of about 10 to 100 cP and may be aerosolized ultrasonically. Resistor glue can be composed of either or both of ruthenate, polymer thick film, or carbon-based components. Commercially available ruthenate gums, typically composed of ruthenium oxide and glass particles, have a viscosity of 1000 cP or greater, which can be diluted to a viscosity of 1000 cP or lower using a suitable solvent such as terpineol. Polymer thick film adhesives can also be diluted in suitable solvents to similar viscosities, so that inferring aerosolization and airflow direction using compressed air is possible. Similarly, carbon-based gums can be diluted to a viscosity of about 1000 cP or less using solvents such as diethylene glycol monobutyl ether. Thus, many commercial glue components with viscosities greater than 1000 cP can be modified and deposited using the ^M3D ( ^R) process.

Resistors: range of resistance, repeatability, and temperature coefficient of resistance

Resistive structures deposited using the M ³ D ^(R) process can include a resistance range of about 6 orders of magnitude, from 1 ohm to 1 megohm. This range of resistance values can be obtained by depositing suitable materials with suitable geometrical cross-sectional areas. For a set of deposits, the tolerance or variance of the resistance values - defined as the ratio of the difference between the highest and lowest resistance values of the passive structure to the average resistance value - can be as low as 2 percent. The temperature coefficient of resistance (TCR) can vary from about ±50 to ±100 ppm for the silver/glass and ruthenate structures.

geometry

By controlling the geometry of the deposits, the method of the invention makes it possible to fabricate structures of specific electronic, optical, physical or chemical value. For example, as shown in Figures 3a and 3b, the properties of the structure can be changed by controlling the cross-sectional area of the structure. The resistance value can be changed by adding material to an existing existing path, thereby increasing the cross-sectional area of the overall path, thereby reducing the resistance value as material is added to the existing existing path. This method is similar to the commonly used laser milling method, however material is added rather than removed. Additional balanced passive paths 38 are deposited on existing passive paths 40 . As another example, specific values can be achieved by controlling the length of the deposited structures; as shown in Figure 4, the rightmost resistor has a larger resistance value. The method of the present invention may also be used to add material over a set of paths as shown in Figures 5a and 5b, or between one or more sets of connection pads 42 connected to pre-existing electronic circuitry. Ladder-type passive paths 44a-b are added to existing passive paths 40 . This method allows tuning of circuits to specific responses or eigenvalues. As shown in FIG. 6, the method can also create passive structures by making passive connections in vias, or by coating resistor material 46 around the edges of the circuit layers.

Passive structures deposited using the ^{M3D (R)} process The invention typically has a linear geometry, such as the linear passive path 48 shown in Figure 7a. Other geometries include, but are not limited to, curved shapes 50 (as shown in Figure 7b), spirals, and helicoidal patterns. The line width of the deposited resistive material typically varies from about 10 to 200 microns, but can be larger or smaller. Linewidths greater than 200 microns can be obtained by depositing material in a raster fashion. The thickness of the deposited film can vary from hundreds of nanometers to several micrometers.

Filled Via

The ^{M3D (R)} process can be used to fill vias that provide electrical interconnection between adjacent layers of electronic circuitry.

The present invention allows precise, uniform deposition of aerosolized material, such as into vias, over extended periods of time.

Figure 8 shows the resistive connections between the different layers of the circuit. Conductive layers in a PCB (Printed Circuit Board) are typically connected by metal vias, however the ^{M3D (R)} process also allows the deposition of resistive structures into the vias. This resistive via configuration is preferred because additional space is provided on the surface of the circuit board layer by moving the layer resistors into the vias.

Figure 9 depicts a method for depositing a capping layer on the walls and bottom of a via. In Fig. 9a, via 60 is completely filled with ink 62 using the process of the present invention. As shown in Figure 9b, as the ink 62 dries, solids 64 will adhere to the via walls and bottom, leaving the via hollow in the middle. Covering the via walls with a highly conductive material results in a very useful structure because most of the current in the via flows along the via walls and not through the middle.

Dielectric

With regard to making dielectric structures, the ink can be composed of precursors for the insulating layer, such as polyimide, while the glue can be a composition containing dielectric particles and glass inclusions with low melting temperature. The precise deposition provided by the present invention is critical for fabricating high tolerance capacitors because the thickness and uniformity of the capacitive film determines the performance of the capacitor. Low-K dielectric materials, such as glass and polymers, have been deposited as dielectrics for capacitor applications, and as insulating or passivation layers to isolate electronic components. Medium-K and high-K dielectrics such as barium titanate can also be deposited for capacitor applications.

Resist

The ^M3D ( ^R) process of embodiments of the present invention can be used for hybrid add/subtract techniques to make precise metal structures using resist. Resist 70 is preferably atomized and deposited onto metal layer 72 through a deposition head, as shown in FIG. 10a. A reducing technique, such as etching, is then used to remove the exposed metal, Figure 10b. In a final step, the resist is removed, leaving the metal structure 74 on the underlying substrate, Figure 10c. This add/reduce resist process can be used to deposit active metals, such as copper.

Target

Targets suitable for direct writing of passive structures using the ^{M3D( R)} process include, but are not limited to, polyimide, FR4, alumina, glass, zirconia, and silicon. Resistor compositions processed on polyimide, FR4, and other targets have a low temperature damage threshold, ie, a damage threshold of about 400°C or lower, and typically require laser heating for proper densification. Laser photochemical processes can be used to directly write mid- to high-range resistor materials, such as strontium ruthenate, on polyimide.

application

Fabrication of passive structures using the ^{M3D (R)} process allows applications including, but not limited to, direct writing of resistors for electronic circuits, heating elements, thermistors, and strain gauges. The structure can be printed on more traditional high temperature targets such as alumina and zirconia; but can also be printed on heat sensitive targets such as polyimide and FR4. The ^{M3D( R)} process can also be used to print embedded passive structures on pre-existing circuit boards, on planar or non-planar surfaces, and in vias connecting several layers into three-dimensional electronic circuits. Other applications include, but are not limited to, mixing passive component components to create deposited structures with specific physical, optical, electronic, or chemical properties; repairing pre-existing passive structures on circuit boards; and modifying the physical, Optical, electronic or chemical properties, depositing passive structures on pre-existing targets. The present invention ensures that the above-mentioned applications have physical or electronic characteristics with a tolerance of 5% or less.

Although the invention has been described in detail with reference to certain preferred and alternative embodiments, various modifications and improvements can be made by those skilled in the art of the invention without departing from the spirit and scope of the following claims, and other embodiments can also be achieve the same effect. The various configurations that have been disclosed above are intended to teach the reader preferred and alternative embodiments, and are not meant to limit the scope of the invention or the claims. Various modifications and improvements of the present invention will be apparent to those skilled in the art, and it is to cover all such modifications and equivalents. All patents and published specifications cited above are hereby incorporated by reference in their entirety.

Claims (20)

1. An apparatus for depositing a passive structure comprising material on a target, The equipment includes: A nebulizer for forming a suspension comprising material and carrier gas; Exhaust flow controller for exhausting excess carrier gas; Deposition head for mixing suspensions in the cylindrical casing gas stream; Pressure sensor converter; A cross pipe joint connecting the sprayer, the deposition head, the exhaust flow controller and the converter; In this case, the error of the ideal characteristic of the passive structure is better than about 5%. 2. The apparatus as claimed in claim 1, wherein the deposition head and the sprayer are connected to opposite inlets of the cross fitting. 3. The apparatus of claim 2, wherein the exhaust flow controller exhausts excess carrier gas in a direction perpendicular to the direction in which suspended matter moves through the cross fitting. 4. The apparatus of claim 1, wherein the exhaust flow controller reduces the flow rate of the carrier gas. 5. The apparatus of claim 1, further comprising a processor for receiving data from said transducer, said processor determining whether there is a leak or blockage in said apparatus. 6. A device as claimed in claim 5, further comprising a feedback loop which automatically purges said device if a blockage is detected; or automatically stops operation of said device if a leak is detected. 7. The device of claim 1, further comprising: a laser whose laser beam passes through the flowing suspension; and A photodiode for detecting scattered light from the laser. 8. The apparatus as claimed in claim 7, wherein said laser beam is perpendicular to the suspension flow direction and said photodiode is positioned orthogonal to both said laser beam and said air flow direction. 9. The apparatus of claim 7, further comprising a controller for automatically controlling the power of the nebulizer. 10. A method of depositing a passive structure comprising material on a target, the method comprising the steps of: atomized material; Delivery of atomized material into a carrier gas to form a suspension; removing excess carrier gas from the suspension through openings positioned perpendicular to the direction of flow of the suspension; monitoring the pressure of the suspension; surrounding the suspension with casing gas; and deposit material on the target; Therein the error of the ideal characteristic of the passive structure is better than about 5%. 11. The method of claim 10, further comprising the step of determining the presence of a leak or blockage based on the pressure value. 12. The method of claim 11, further comprising the step of automatically cleaning the system if clogging occurs. 13. The method of claim 11, further comprising the step of automatically stopping operation if a leak occurs. 14. The method of claim 10, further comprising the step of shining a laser beam into the suspension, and measuring scattered light from the laser beam. 15. The method of claim 10, wherein the step of measuring is performed by a detector positioned orthogonal to both the laser beam and the direction of flow of the suspension. 16. The method of claim 14, further comprising the step of varying the power used in the nebulizing step based on the amount of scattered light detected in the measuring step. 17. The method of claim 10, further comprising the step of treating the material. 18. The method of claim 17, wherein the treating step is selected from the group consisting of wetting the suspension, drying the suspension, heating the suspension, heating the deposited material, irradiating the deposited material with a laser beam, and combinations thereof. 19. The method of claim 18, wherein irradiating the deposited material using a laser beam ensures that the deposited material has a line width as small as about 1 micron. 20. The method of claim 18, wherein irradiating the deposited material using the laser beam does not raise the average temperature of the target above a destruction threshold.

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