Patent Application
20170100916
The present invention is directed to electronic components and processes of producing electronic components. More particularly, the present invention is directed to energetic beam remelt components and processes.
Deposition of conductive inks via different printing technologies is a growing field, with limitations on compatibility for existing techniques. Such limitations render it difficult to utilize the perceived selectivity and ability to produce lower feature-sized electrical contacts. For example, reliance upon metallization techniques on printed features is problematic because they are very complicated thermodynamic and kinetic processes.
Flexibility and breadth of use for electrical contact layers is highly desirable. Prior techniques have not had sufficient control of properties associated with electrical contact layers and, thus, have been limited in application. For example, prior techniques have not adequately permitted inclusion of nanocrystalline structures and/or amorphous structures, permitted creation of medium or larger grains, permitted pore free or substantially pore free layers, permitted a gradient of elemental or compositional metals or alloys, permitted formation of a grain boundary strengthened by grain boundary engineering, permitted grain pinning, permitted higher surface hardness, permitted higher wear resistance, permitted diffusion of elements or formation of an interdiffusion layer, permitted higher corrosion resistance, or permitted combinations thereof.
Electroplating has been used to make fine grained contact surfaces which have shown improved properties in electrical contact structures. (See European Publication No. 0160761 B1, “Amorphous Transition Metal Alloy, thin gold coated, electrical contact”, published Feb. 8, 1989.)
Electroplating of electrical contacts is a common process which requires large volumes of plating bath chemicals, large area physical footprint, and consumes large quantities of precious metals. Due to environmental regulations, electroplating lines are typically segregated to specific geographic zones and undergo high levels of regulatory scrutiny. In addition, the process of electroplating is limited to a confined space for application of coating. Further, electroplated coatings result in an undesirably porous structure.
An electronic component and process of producing an electronic component that show one or more improvements in comparison to the prior art would be desirable in the art.
In an embodiment, an electronic component includes a substrate and a thermal grain modified layer positioned on the substrate. The thermal grain modified layer includes a modified grain structure. The modified grain structure includes a thermal grain modification additive.
In another embodiment, a process of producing an electronic component includes providing a substrate and applying a pre-modification layer to the substrate comprising one or more metallic components and a thermal grain modification additive. The pre-modification layer is heated and cooled to form a thermal grain modified layer.
Other features and advantages of the present invention will be apparent from the following more detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.
Wherever possible, the same reference numbers will be used throughout the drawings to represent the same parts.
Provided are electronic components and processes of producing electronic components. Embodiments of the present disclosure, for example, in comparison to concepts failing to include one or more of the features disclosed herein, permit inclusion of nanocrystalline structures and/or amorphous structures, permit creation of medium or larger grains, such as grains from about 0.5 μm to about 4 μm grains, permit pore-free or substantially pore-free layers, permit a gradient of elemental or compositional metals or alloys, permit formation of a grain boundary strengthened by grain boundary engineering via alloying element/compound additions, permit formation of a grain boundary pinning via alloying elements and insoluble particle, permit higher surface hardness, permit higher wear resistance, permit diffusion of elements or formation of an interdiffusion layer, permit higher corrosion resistance, or permit combinations thereof. The method, according to embodiments of the present disclosure, includes a process that is more environmentally friendly and includes selective deposition of precious metals that do not require electroplating. Processes, according to embodiments of the present disclosure, include higher throughput speeds, smaller footprint, and reduced precious metal consumption. In addition to process advantages, the technique generates desirable grain structures, alloys, and microstructures that provide desired physical properties. The thermal grain modified layer formed includes a surface that is smoother and less porous than electroplated surfaces. In addition, the process, according to the present disclosure, permits the inclusion of a larger selection of metals for thermal grain modified layer than can be electroplated.
Referring to
Thermal grain modification, as utilized herein, is an enhancement or otherwise a modification to a metallic structure of a deposited metal. Thermal grain modification is provided by a heating and controlled cooling of a metal deposited on substrate 101 to obtain grain refinement and form preferential grain orientations. Grain refinement, as utilized herein, includes achieving small grain size by way of adding higher melting point alloying/substitutional elements or insoluble compounds. While not wishing to be bound by theory or specific explanation, these additives either act as nucleation sites for fine-sized grains during solidification (when the molten phase cools down) or pin the grain boundaries at temperatures below melting point to overcome grain growth. The grain refiner nucleants, when added to the metal alloy, give a wide range of physical and mechanical properties including high corrosion resistance, good weldability, low shrinkage, low thermal expansion, high tensile properties, good surface finish resulting in improved machinability when compared with an unmodified alloy. The increase in the strength as the grain size gets significantly smaller is believed to be related to Hall-Petch strengthening. Smaller grains have greater ratios of surface area to volume, which means the fraction of grain boundaries increases. Grain boundaries impede the dislocation slip (in general movement), which is, in general, the atomistic mechanism of plastic deformation for grain sizes greater than several nanometers.
In addition, the thermal grain modified layer 103 provides a fine grained contact finish. For example, the thermal grain modified layer 103 provides a finer grain contact finish than layers formed by electroplating.
The thermal grain modified layer 103 is formed from pre-modification layer 207. The pre-modification layer 207 includes at least one metal, alloy or metallic component and a thermal grain modification additive. For example, the pre-modification layer 207 may include metal/metallic inks/dyes/pastes or any other suitable material having the desired composition. The formulation of the pre-modification layer 207 may be any suitable ink/dye/paste formulation capable of carrying the desired metal, alloy or metallic component. For example, the pre-modification layer 207, in one embodiment, may be formed utilizing the coating layer composition of U.S. Patent Publication No. 2014/0097002 (Sachs et al.), which is hereby incorporated by reference in its entirety. Suitable metallic components for inclusion in the pre-modification layer 207 include, but are not limited to, gold (Au), silver (Ag), tin (Sn), molybdenum (Mo), titanium (Ti), palladium (Pd), platinum (Pt), rhodium (Rh), iridium (Ir), aluminum (Al), ruthenium (Ru), or combinations thereof. In addition, the pre-modification layer 207 includes a thermal grain modification additive. Thermal grain modification additives include components that provide thermal grain modification upon the heating and cooling steps, according to the present disclosure. Suitable thermal grain modification additives include, but are not limited to, solid additives, such as germanium (Ge), titanium (Ti), molybdenum (Mo), tungsten (W), tantalum (Ta), niobium (Nb), zirconium (Zr), vanadium (V), combinations thereof, or chemical additives such as nickel sulfate, nickel acetate, sodium molybdate, ammonium molybdate, organometallic complexes of W, Mo, Nb, Ta, Ti, Zr, Hf, Re, organometallic complexes of transition metals and post-transition metals, and combinations thereof.
In one embodiment, particularly suitable additives include boron, nickel acetate, nano nickel, nickel carbonate, nano molybdenum, tungstic acid, copper+germanium, titanium nitride nanoparticles, and combinations thereof. One suitable nanoparticle is an insoluble titanium nitride nanoparticle distributed within the matrix of the pre-modification layer 207. Such nanoparticles have maximum dimensions of between 10 nm and 30 nm, between 10 nm and 20 nm, between 20 nm and 30 nm, or any suitable combination, sub-combination, range, or sub-range therein.
Although not shown, a diffusion barrier layer may be applied to the substrate 101 prior to application of the pre-modification layer 207 to reduce or eliminate diffusion of the substrate material. The barrier layer includes any suitable barrier material, such as, but not limited to, nickel (Ni), titanium (Ti), molybdenum (Mo), tungsten (W), tantalum (Ta), niobium (Nb), zirconium (Zr), vanadium (V), chromium (Cr), iron (Fe), cobalt (Co), manganese (Mn), iron (Fe), hafnium (Hf), rhenium (Re), zinc (Zn), or a combination thereof. The composition of the diffusion barrier layer corresponds with the composition of the substrate and the thermal grain modified layer 103. In one embodiment, the composition of the diffusion barrier layer includes one or both of titanium and molybdenum, when the composition of the thermal grain modified layer 103 includes one or more of copper, silver and gold. In a further embodiment, the diffusion barrier layer further includes indium and/or gallium, for example, allowing the heating and cooling to be at a lower temperature, such as, below the melting point of copper.
In one embodiment, the heating and cooling is by furnace heating. In one embodiment, the thermal grain modified layer 103 is annealed. Suitable temperatures for the heating and cooling depend upon the composition used to produce the thermal grain modified layer 103. In one embodiment, the pre-modification layer 207 includes Cu and Ge and the heating is at a temperature of 1,000° C. In another embodiment, the pre-modification layer 207 includes Ag, Cu, and Ge and the heating is likewise at a temperature of 1,000° C. In other embodiments, the heating is at a temperature of between 800° C. and 1,200° C., between 900° C. and 1,100° C., between 900° C. and 1,200° C., between 800° C. and 1,100° C., or any suitable combination, sub-combination, range, or sub-range therein. For cooling, any suitable quenching or cooling may be utilized. For example, the thermal grain modified layer 103 may be furnace cooled, air cooled, quenched or otherwise cooled to form the thermal grain modified layer 103.
In one embodiment, the heating and cooling by energetic beam remelting is achieved by any suitable techniques. Suitable techniques include, but are not limited to, applying a continuous energetic beam (for example, from a CO2 laser or electron beam welder), applying a pulsed energetic beam (for example, from a neodymium yttrium aluminum garnet laser), applying a focused beam, applying a defocused beam, or performing any other suitable beam-based technique. Energetic beam remelting is with any suitable parameters, such as, penetration depths, pulse duration, beam diameters (at contact point), beam intensity, and wavelength.
Suitable penetration depths depend upon the composition and the beam energies. For example, for Cu or Cu-containing compositions, suitable penetration depths at 20 kV include, but are not limited to, between 1 and 2 micrometers, between 1 and 1.5 micrometers, between 1.2 and 1.4 micrometers, or any suitable combination, sub-combination, range, or sub-range therein. For Cu or Cu-containing compositions, suitable penetration depths at 60 kV include, but are not limited to, between 7 and 9 micrometers, between 7.5 and 8.5 micrometers, between 7.8 and 8.2 micrometers, or any suitable combination, sub-combination, range, or sub-range therein.
For Ag or Ag-containing compositions, suitable penetration depths at 20 kV include, but are not limited to, between 1 and 2 micrometers, between 1 and 1.5 micrometers, between 1.2 and 1.4 micrometers, or any suitable combination, sub-combination, range, or sub-range therein. For Ag or Ag-containing compositions, suitable penetration depths at 60 kV include, but are not limited to, between 8 and 9 micrometers, between 8.2 and 8.8 micrometers, between 8.4 and 8.6 micrometers, or any suitable combination, sub-combination, range, or sub-range therein.
Suitable pulse durations include, but are not limited to, between 4 and 24 microseconds, between 12 and 100 microseconds, between 72 and 200 microseconds, between 100 and 300 microseconds, between 250 and 500 microseconds, between 500 and 1,000 microseconds, or any suitable combination, sub-combination, range, or sub-range therein.
Suitable beam widths include, but are not limited to, between 25 and 50 micrometers, between 30 and 40 micrometers, between 30 and 100 micrometers, between 100 and 150 micrometers, between 110 and 130 micrometers, between 120 and 140 micrometers, between 200 and 600 micrometers, between 200 and 1,000 micrometers, between 500 and 1,500 micrometers, or any suitable combination, sub-combination, range, or sub-range therein.
Suitable beam intensities include, but are not limited to, having a power output of between 2,000 watts to 10 kilowatts, between 10 kilowatts to 30 kilowatts, between 30 to 100 kilowatts, between 0.1 and 2,000 watts, between 1,100 and 1,300 watts, between 1,100 and 1,400 watts, between 1,000 and 1,300 watts, between 50 and 900 watts, between 4.5 and 60 watts, between 1 and 2 watts, between 1.2 and 1.6 watts, between 1.2 and 1.5 watts, between 1.3 and 1.5 watts, between 200 and 250 milliwatts, between 220 and 240 milliwatts, or any suitable combination, sub-combination, range, or sub-range therein.
In embodiments utilizing the laser for the energetic beam remelting, suitable wavelengths include, but are not limited to, between 10 and 11 micrometers, between 9 and 11 micrometers, between 10.5 and 10.7 micrometers, between 1 and 1.1 micrometers, between 1.02 and 1.08 micrometers, between 1.04 and 1.08 micrometers, between 1.05 and 1.07 micrometers, or any suitable combination, sub-combination, range, or sub-range therein.
In one embodiment, the thermal grain modified layer 103 has a selected concentration of Ag grains with certain orientations, for example, having a greater fraction of (111)-orientation Ag grains than (200)-orientation Ag grains. In further embodiments, the relative fraction of the (111)-orientation Ag grains to the (200)-orientation Ag grains is at a ratio of 2 to 1, at a ratio of greater than 2 to 1, at a ratio of great than 2.1 to 2, at a ratio of 2.16, or any suitable combination, sub-combination, range, or sub-range therein.
In one embodiment, the thermal grain modified layer 103 has a lower coefficient of friction than electroplated Ag (between 0.7 and 0.9). For example, suitable coefficients of friction for the thermal grain modified layer 103 include, but are not limited to, between 0.15 and 0.35, between 0.15 and 0.25, between 0.2 and 0.35, between 0.2 and 0.3, any relative value compared to the coefficient of friction of the electroplated Ag, or any suitable combination, sub-combination, range, or sub-range therein.
The Ag grains within the thermal grain modified layer 103 have dimensions and morphology corresponding with the desired application. Suitable maximum dimensions for the Ag grains include, but are not limited to, between 1 nm and 110 nm, between 90 nm and 110 nm, between 1 nm and 20 nm, between 5 nm and 15 nm, between 1 nm and 3 nm, between 1 nm and 5 nm, between 0.5 nm and 1.5 nm, or any suitable combination, sub-combination, range, or sub-range therein.
While the invention has been described with reference to one or more embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. In addition, all numerical values identified in the detailed description shall be interpreted as though the precise and approximate values are both expressly identified.
