Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
  • H01B1/20—Conductive material dispersed in non-conductive organic material
  • H01B1/22—Conductive material dispersed in non-conductive organic material the conductive material comprising metals or alloys
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K1/00—Printed circuits
  • H05K1/02—Details
  • H05K1/09—Use of materials for the conductive, e.g. metallic pattern
  • H05K1/092—Dispersed materials, e.g. conductive pastes or inks
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
  • C04B41/009—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone characterised by the material treated
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
  • C04B41/45—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements
  • C04B41/50—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements with inorganic materials
  • C04B41/51—Metallising, e.g. infiltration of sintered ceramic preforms with molten metal
  • C04B41/5105—Metallising, e.g. infiltration of sintered ceramic preforms with molten metal with a composition mainly composed of one or more of the noble metals or copper
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
  • C04B41/45—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements
  • C04B41/50—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements with inorganic materials
  • C04B41/51—Metallising, e.g. infiltration of sintered ceramic preforms with molten metal
  • C04B41/5111—Ag, Au, Pd, Pt or Cu
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
  • C04B41/45—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements
  • C04B41/50—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements with inorganic materials
  • C04B41/51—Metallising, e.g. infiltration of sintered ceramic preforms with molten metal
  • C04B41/5116—Ag or Au
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
  • C04B41/80—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone of only ceramics
  • C04B41/81—Coating or impregnation
  • C04B41/85—Coating or impregnation with inorganic materials
  • C04B41/88—Metals
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10W—GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10
  • H10W70/00—Package substrates; Interposers; Redistribution layers [RDL]
  • H10W70/60—Insulating or insulated package substrates; Interposers; Redistribution layers
  • H10W70/62—Insulating or insulated package substrates; Interposers; Redistribution layers characterised by their interconnections
  • H10W70/66—Conductive materials thereof
  • H10W70/666—Organic materials or pastes
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10W—GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10
  • H10W70/00—Package substrates; Interposers; Redistribution layers [RDL]
  • H10W70/60—Insulating or insulated package substrates; Interposers; Redistribution layers
  • H10W70/67—Insulating or insulated package substrates; Interposers; Redistribution layers characterised by their insulating layers or insulating parts
  • H10W70/69—Insulating materials thereof
  • H10W70/692—Ceramics or glasses
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
  • C04B2111/00474—Uses not provided for elsewhere in C04B2111/00
  • C04B2111/00844—Uses not provided for elsewhere in C04B2111/00 for electronic applications

Definitions

• the invention is directed to a thick film composition for use on an aluminum nitride substrate.
• the composition includes a boron containing reactant and a metal oxide that promotes adhesion to the substrate.
• BACKGROUND OF THE INVENTION In recent years aluminum nitride substrates for circuit boards have been employed for use in high-temperature environments because of their high heat conduction coefficient. However, in order to adhere metal conductors to aluminum nitride substrates, it becomes necessary to use thick film compositions that are capable of providing a thin reactive layer (oxide film) formed between the metal found in the composition and the substrate by introducing the metal in atomic form to the surface of the substrate.
• the metal which is extremely active, chemically bonds with excess oxygen that exists on the surface of the substrate.
• US Patent Number 6,103,146 to Okamoto describes such a composition for use on an aluminum nitride substrate wherein a conductive powder and a metal boride are dispersed in an organic medium.
• the present invention improves the adhesion performance of the existing compositions.
• the invention is directed to a thick film composition
• a thick film composition comprising: a) electrically conductive powder; b) boron containing reactant selected from boron oxide, elemental boron, metal boride and mixtures thereof; and c) metal oxide; wherein a through c are dispersed in organic medium.
• DETAILED DESCRIPTION OF INVENTION The invention is a thick film composition for use on an aluminum nitride substrate. Thick film technology, which includes compositions thereof, is an established method in the electronic industry to efficiently manufacture hybrid electronic circuitry.
• the main components of the thick film conductor composition described herein are a conductor powder, a boron containing reactant, and a metal oxide dispersed in an organic medium. The components are discussed below.
• a thick film composition comprises a functional phase that imparts appropriate electrically functional properties to the composition.
• the functional phase comprises electrically functional powders dispersed in an organic medium that acts as a carrier for the functional phase.
• the composition is fired to bum out the organics and to impart the electrically functional properties.
• a processing requirement may include an optional heat treatment such as drying, curing, reflow, and others known to those skilled in the art of thick film technology.
• Organics comprise polymer or resin components of a thick film composition.
• the electrically functional powders in the present thick film composition are conductor powders and may comprise a single type of metal powder, mixtures of metal powders, alloys, or compounds of several elements.
• the particle diameter and shape of the metal powder is not particularly important as long as it is appropriate to the application method.
• Such powders include: gold, silver, copper, nickel, aluminum, platinum, palladium, molybdenum, tungsten, tantalum, tin, indium, lanthanum, gadolinium, boron, ruthenium, cobalt, titanium, yttrium, europium, gallium, sulfur, zinc, silicon, magnesium, barium, cerium, strontium, lead, antimony, conductive carbon, and combinations thereof and others common in the art of thick film compositions.
• the boron containing reactant is selected from: combinations of boron and a metallic element which include binary, ternary and higher compounds of boron and a metallic element (called metal borides); boron oxide and sources that produce boron oxide under firing conditions (e.g. boric acid, B 2 0 3 , and borate glass); elemental boron (hydrated or anhydrous) and a mixture of the listed reactants.
• metal borides includes TiB 2 , ZrB 2 , HfB 2 .
• the level of the boride reactant added to the composition is determined by the extent that it does not cause poor solder wetting as a result of the B 2 O 3 formed from boron in the firing process that becomes vitrified and covers the conductor surface.
• the unwanted decreased solder wetting effect of the B 2 O3 is related to the type and form of noble metal used, that is, whether pure or alloy; the metal oxide additive; and the density of the thick film after firing. Consequently, through selection of combinations, it is possible to inhibit formation of vitreous B 2 O 3 on or migration of vitreous B 2 O 3 to the thick film surface.
• the amount of boron containing reactant contained in the composition should be no more than 1.6 parts by weight per 100 parts by weight based on total composition in order to apply the thick film conductor composition on an aluminum nitride substrate without causing poor solder wetting.
• the metal oxide may be one type of metal oxide powder or a mixture of different metal oxide powders. Some examples of metal oxides include Co 3 O 4 , Fe 2 O 3 , ZnO, SnO 2 , TiO 2 , ZrO 2 and mixtures thereof.
• the metal oxide (1 ) reacts with the aluminum nitride substrate in the presence of the boron containing reactant to form ternary metal aluminate compounds or quaternary metal boroaluminate compounds forming an adhesive bond and/or; (2) modifies the vitrification (glass formation) of the boron containing reactant upon its oxidation thereby improving the solder wettability of the composition.
• a metal oxide forming moiety can replace the metal oxide powders or partially replace some of the powders.
• the metal oxide can be produced several ways; such as, oxidation of metals, decomposition of metal carbonates, conversion from metal sulfides, sulfates, phosphates, nitriates, nitrides, borides, halides, etc., under firing conditions for processing the compositions.
• the metal oxide in the composition is no more than 2 parts by weight per 100 parts by weight based on the total composition.
• the boron containing reactant and metal oxide in combination are no more than 3 parts by weight per 100 parts by weight of the total composition.
• the metal oxide and the boron containing reactant react with the aluminum nitride substrate during the firing process, producing an oxidation reaction product (2AI 2 O3.B O 3 ), which contributes to adhesion between the conductor and the substrate.
• an oxidation reaction product (2AI 2 O3.B O 3
• the combination of TiO 2 with anhydrous boron reacts with AIN in air to form B 2 O 3 , 2AI 2 O 3 .B 2 O 3 , and a TiO 2 modified B 2 O3 glass.
• the TiO 2 inhibits the formation and flow of the B 2 O 3 glass thus improving solder wettability of the metallic conductor thick film composition.
• the addition of Co 3 O 4 to TiB 2 reacts with the AIN to form both 2AI 2 O 3 .B 2 O 3 and CoAI 2 O 4 interfacial (conductor - substrate interface) bond phases.
• the Co 3 O4 also inhibits the formation and flow of the B 2 O 3 glass thus improving solder wettability.
• the powders described hereinabove are finely dispersed in an organic medium and are optionally accompanied by inorganic binders, ceramics, and fillers, such as other powders or solids.
• inorganic binder in a thick film composition is binding the particles to one another and to the substrate after firing.
• inorganic binders include glass binders (frits), metal oxides, and ceramics.
• Glass binders useful in the thick film composition are conventional in the art. Some examples include borosilicates and aluminosilicates glasses.
• Examples further include combinations of oxides, such as: B 2 O 3 , SiO 2 , AI 2 O 3 , Bi 2 O 3 , CuO, CdO, CaO, BaO, ZnO, SiO 2 , Na 2 O, PbO, and ZrO which may be used independently or in combination to form glass binders.
• the thick film composition can also include other metal particles and inorganic binder particles to enhance various properties of the composition, such as adhesion, sintering, processing, brazeability, solderability, reliability, etc., during processing.
• Organic Medium The powders are typically mixed with an organic medium (vehicle) by mechanical mixing to form a pastelike composition called "pastes", having suitable consistency and rheology for printing.
• inert liquids can be used as organic medium.
• the organic medium must be one in which the solids are dispersible with an adequate degree of stability.
• the rheological properties of the medium must be such that they lend good application properties to the composition. Such properties include: dispersion of solids with an adequate degree of stability, good application of composition, appropriate viscosity, thixotropic, appropriate wettability of the substrate and the solids, a good drying rate, good firing properties, and a dried film strength sufficient to withstand rough handling.
• the organic medium is conventional in the art and is typically a solution of polymer in solvent(s). The most frequently used resin for this purpose is ethyl cellulose.
• resins include ethyl hydroxyethyl cellulose, wood rosin, mixtures of ethyl cellulose and phenolic resins, polymethacrylates of lower alcohols, and monobutyl ether of ethylene glycol monoacetate can also be used.
• the most widely used solvents found in thick film compositions are ethyl acetate and terpenes such as alpha- or beta-terpineol or mixtures thereof with other solvents such as kerosene, dibutylphthalate, butyl carbitol, butyl carbitol acetate, hexylene glycol and high boiling alcohols and alcohol esters.
• volatile liquids for promoting rapid hardening after application on the substrate can be included in the vehicle.
• the preferred mediums are based on ethylcellulose and ⁇ -terpineol. Various combinations of these and other solvents are formulated to obtain the viscosity and volatility requirements desired.
• the solids are mixed with an essentially inert liquid medium (vehicle) by mechanical mixing using a planetary mixer, then dispersed on a three roll mill to form a paste-like composition having suitable consistency and rheology for screen printing.
• a paste-like composition having suitable consistency and rheology for screen printing.
• the latter is printed as a "thick film” paste on an aluminum nitride substrate in the conventional manner as known to those in the art of thick film technology.
• the ratio of organic medium in the thick film composition to the inorganic solids in the dispersion is dependent on the method of applying the paste and the kind of organic medium used. Normally to achieve good coverage, the dispersions will contain complementarily 50-91% wt. inorganic solids and 50-9% wt. vehicle, as described above.
• the compositions of the present invention may, of course, be modified by the addition of other materials, which do not affect its beneficial characteristics. Such formulations are well within the state of the art.
• the pastes are conveniently prepared on a three-roll mill. The viscosity of the pastes is typically within the following ranges when measured on a Brookfield HBT viscometer at low, moderate, and high shear rates: Shear Rate (sec" ' ' ) Viscosity (Pa * s)
• Print parts are dried 5-15 minutes at 80-150°C. They are then fired three times in a belt furnace which has a 10 minute peak temperature cycle at 850°C; and a 30 minute descending temperature ramp back down from 850°C to ambient.
• the parts After firing three times, the parts have wires attached as follows. Wires are clipped onto the substrate so that they each run down the center of three pads. Then the wires/fired parts are dipped into Alpha 611 solder flux. The parts are then prewarmed on the solder bath and dipped for 10 seconds, and allowed to cool. Residual solder flux is cleaned from the soldered wire parts with a CH 2 CL 2 /methanol mixture. Parts are placed in an oven at 150°C for 48 hours, then removed and cooled. The aged parts are placed in an apparatus for measuring the force necessary to separate the wire from the substrate. The force necessary is recorded. Also, the type of separation is noted, i.e., whether separation involves the wires pulling out of the solder pulls off the substrate. Over 15 Newtons is good adhesion. Over 20 Newtons is excellent adhesion. Adhesion of 12-14 Newtons is marginal and below 12 is unacceptable.
• a typical test pattern with a conductor resistance test pattern and pads (2 x 2 mm) was prepared, and a thick film paste composition as given in Table 1 was screen printed using the typical adhesion test pattern on an aluminum nitride substrate measuring 1"x1"x0.25", dried, and fired at 850°C/30 minutes in a belt furnace in air atmosphere and repeated three times so that the thickness of the conductor after firing was about 11 ⁇ m-12 ⁇ m. Tests were preformed as described above. Table 2 shows results of the test method.
• Example 1 It is demonstrated that only silver powder in the composition results in an inadequate bond of the composition to the AIN substrate.
• Example 2 Boron added to the silver composition produces an inadequate bond of the composition to the AIN substrate.
• Example 3 TiO 2 added to the silver composition results in inadequate bonding of the composition to the AIN substrate.
• Example 4 Co 3 O 4 added to silver composition produces an inadequate bond of the composition to the AIN substrate.
• Example 5 This composition has a combination of C ⁇ 3 ⁇ 4 and TiO2. The resulting composition is unable to bond to the AIN substrate.
• Example 6 This composition has a combination of B and Co 3 O 4 .
• the composition is able to provide reasonable bonding strength to the AIN substrates. Compared to Examples 2 and 4, it suggests that both B and a metal oxide like Co 3 O 4 are needed to promote adhesion.
• Example 7 TiB 2 added to a silver composition produces an acceptable bond of lower strength than that formed with both TiB 2 + Co 3 O 4 (or Fe 2 O 3 ) additions (Examples 8 to 10).
• the TiB 2 additive produces a lower quality solder fillet (poor wetting).
• Examples 8-12 show the added adhesion through use of the claimed invention.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Ceramic Engineering (AREA)
• Materials Engineering (AREA)
• Structural Engineering (AREA)
• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Dispersion Chemistry (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Physics & Mathematics (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Parts Printed On Printed Circuit Boards (AREA)
• Conductive Materials (AREA)
• Ceramic Products (AREA)
• Manufacturing Of Printed Wiring (AREA)
• Compositions Of Oxide Ceramics (AREA)
• Paints Or Removers (AREA)
• Inorganic Insulating Materials (AREA)
• Glass Compositions (AREA)

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Publications (3)

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• 2002
  • 2002-10-08 CN CNB028197828A patent/CN1307124C/zh not_active Expired - Fee Related
  • 2002-10-08 WO PCT/US2002/033469 patent/WO2003031373A2/en not_active Ceased
  • 2002-10-08 AT AT02801065T patent/ATE334949T1/de not_active IP Right Cessation
  • 2002-10-08 JP JP2003534363A patent/JP4351050B2/ja not_active Expired - Fee Related
  • 2002-10-08 US US10/488,844 patent/US20040245508A1/en not_active Abandoned
  • 2002-10-08 KR KR1020047005129A patent/KR100585909B1/ko not_active Expired - Fee Related
  • 2002-10-08 AU AU2002356830A patent/AU2002356830A1/en not_active Abandoned
  • 2002-10-08 EP EP02801065A patent/EP1434750B1/en not_active Expired - Lifetime
  • 2002-10-08 DE DE60213628T patent/DE60213628T2/de not_active Expired - Lifetime

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