Two-part interface materials, systems including the interface material, and methods thereof

Abstract

The teachings herein relate to new compositions for thermal interface materials that provide improved thermal conductivity without requiring filler materials that are expensive or abrasive. The improved thermal conductivity is achieved using a combination of increased filler loading, selection of a filler having abroad particle size distribution, and selection of filler that is non-abrasive. The thermal interface material preferably has a specific gravity of about 4.0 or less, about 3.0 or less, about 2.5 or less, or about 2.4 or less. The thermal interface material may be a two-part composition. In order to achieve maximum thermal conductivity, each part preferably includes a liquid matrix material and dispersed filler. Upon mixing, the first and second parts may react to increase this viscosity (e.g., by polymerizing and/or cross-linking). The first part preferably includes a carbamate-containing compound that reacts with a carbamate-reactive compound, which is preferably in the second component. The first part preferably is substantially or entirely free of isocyanate containing compounds, as these compounds may reduce the shelf life stability of the composition. The carbamate-reactive compound preferably is a polyamine, including two or more spaced apart amine groups. The first part, the second part, or both, preferably includes a catalyst for accelerating the reaction between the carbamate-containing compound and the carbamate-reactive compound.

What is claimed is: 
     
         1 . A two-part composition for a thermal interface material comprising:
 i) a first part comprising at least
 a) a prepolymer including two or more carbamate groups; 
   ii) a second part comprising at least:
 b) one or more polyamine compounds capable of a reaction with the prepolymer; 
   wherein the composition includes:
 c) one or more catalysts for catalyzing the reaction between the prepolymer and the polyamine compounds; and 
 d) 50 weight percent or more of one or more conductive fillers, based on the total weight of the two-part composition. 
   
     
     
         2 . The two-part composition of  claim 1 , wherein the prepolymer is formed by blocking one or more of the isocyanate groups (preferably substantially each, or entirely each of the isocyanate groups) of an aromatic aromatic poolyisocyanate prepolymer with a phenol group of a blocking compound. 
     
     
         3 . The two-part composition of  claim 2 , wherein the blocking compound includes a terminal phenol group (preferably a single terminal phenol group) attached to a linear hydrocarbon (preferably the linear hydrocarbon includes 6 or more, 8 or more, 10 or more, or 12 or more carbon atoms) (preferably the linear carbon includes 60 or less, 30 or less, or 20 or less carbon atoms). 
     
     
         4 . The two-part composition of  claim 1 , wherein the one or more polyamines, the prepolymer, or both have an average functionality of greater than 2. 
     
     
         5 . The two-part composition of  claim 1 , wherein the one or more thermally conductive fillers includes a filler selected from aluminum hydroxide, aluminium oxide, aluminium powder, zinc oxide, boron nitride, and/or mixtures of any of these. 
     
     
         6 . The two-part composition of  claim 1 , wherein the one or more thermally conductive fillers include a filler selected from aluminum hydroxide, aluminium oxide, and/or mixtures of any of these. 
     
     
         7 . The two-part composition of  claim 1 , wherein the one or more thermally conductive fillers is aluminum hydroxide. 
     
     
         8 . The two-part composition of  claim 1 , wherein the one or more conductive fillers includes aluminum hydroxide. 
     
     
         9 . The two-part composition of  claim 1 , wherein the first part includes 75 weight percent or more aluminum hydroxide and the second part includes 75 weight percent or more aluminum hydroxide. 
     
     
         10 . The two-part composition of  claim 1 , wherein a surface of the aluminum hydroxide is partially or entirely coated with a surface modifier for reducing the hydrophilicity of the surface. 
     
     
         11 . The two-part composition of  claim 1 , wherein the composition includes an aluminum hydroxide having a broad particle size distribution, including a D 90 /D 50  ratio of about 3 or more, wherein the particle size is measured according to ISO 13320, using a 2.24×10 −3  M solution of Tetrasodium pyrophosphate decahydrate (1 g Na 4 P 2 O 7 X10H 2 O in 1000 ml deionized water) as dispersion medium. 
     
     
         12 . The two-part composition of  claim 1 , wherein the composition includes one or more plasticizers. 
     
     
         13 . The two-part composition of  claim 1 , wherein the composition includes a fatty acid or an ester of a fatty acid. 
     
     
         14 . The two-part composition of  claim 1 , wherein the composition comprises an epoxy resin in the first part, preferably wherein a weight ratio of the prepolymer to the epoxy resin is about 0.5 or more, more preferably about 0.8 or more, even more preferably about 1.0 or more. (Preferably the weight ratio of the prepolymer to the epoxy resin is about 10 or less, about 5 or less, or about 4 or less). 
     
     
         15 . The two-part composition of  claim 1 , wherein the composition is substantially free of isocyanate containing compounds (e.g., the amount of NCO in the first-part preferably is about 0.10 weight percent or less, about 0.05 weight percent or less, or about 0.01 weight percent or less, based on the total weight of the first part). 
     
     
         16 . The two-part composition of  claim 1 , wherein a molar ratio of the carbamate groups in the first part to the amine groups in the second part is about 0.1 or more, about 0.2 or more, about 0.3 or more, about 0.4 or more, about 0.5 or more, or about 0.6 or more and/or about 10 or less, about 5.0 or less, about 3.5 or less, about 2.5 or less, about 2.0 or less, or about 1.7 or less. 
     
     
         17 . The two-part composition of  claim 1 , wherein the first part includes calcium carbonate (preferably in an amount of about 0.1 weigh percent or more, more preferably about 0.5 weight percent or more, and most preferably about 1.0 weight percent or more, based on the total weight of the first part). 
     
     
         18 . The two-part composition of  claim 1 , wherein the catalyst is a Lewis acid or a Lewis base. 
     
     
         19 . The two-part composition of  claim 1 , wherein the catalyst is a tin catalyst. 
     
     
         20 . The two-part composition of  claim 1 , wherein the catalyst is an amine catalyst. 
     
     
         21 . The two-part composition of  claim 1 , wherein the catalyst is DABCO (1,4-diazabicyclo[2.2.2]octane). 
     
     
         22 . The two-part composition of  claim 1 , wherein the first part includes some or all of the catalyst. 
     
     
         23 . The two-part composition of  claim 1 , wherein the composition is characterized by a thermal conductivity of about 2.0 W/mK or more (preferably about 2.5 or more, more preferably about 2.8 or more, even more preferably about 2.9 or more, and most preferably about 3.0 or more), measured according to ASTM 5470-12 on a therma interface material tester from ZFW Stuttgart, with tests performed in Spaltplus mode at a thickness of between 1.8-1.2 mm; the described thermal interface material is considered as Type I (viscous liquids) as described in ASTM 5470-12, the upper contact is heated to ca 40° C. and the lower contact to ca 10° C., resulting in a sample temperature of ca 25° C. 
     
     
         24 . The two-part composition of  claim 1 , wherein the two-part composition cures at room temperature (preferably as characterized by an increase in a press-in force of about 100% or more, after aging for 24 hours after mixing). 
     
     
         25 . The two-part composition of  claim 1 , wherein the first part is shelf stable (e.g., as characterized by a press-in force of the first part of less than 700 N after aging for 3 days at 55° C.). 
     
     
         26 . An article comprising: a first component that generates heat, a second component for removing heat, and a layer of a thermal interface material interposed between the first and second components, wherein the thermal interface material provides a path for transferring a heat from the first component to the second component and is formed of the two-part composition of  claim 1 . 
     
     
         27 . A method comprising a step of: arranging a layer of a thermal interface material between a first component and a second component, and applying a pressure so that the thermal interface material contacts both the first component and the second component and fills a gap between the two components, wherein the thermal interface material is formed of a two-part composition of  claim 1 .