High solids HBN slurry, HBN paste, spherical HBN powder, and methods of making and using them
Inactive Publication Date: 2015-11-17
SAINT GOBAIN CERAMICS & PLASTICS INC
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The present invention provides a hexagonal boron nitride slurry with high solid loading and low viscosity. The slurry can be used to produce high yields of hexagonal boron nitride powder and paste. The spherical shape of the hBN agglomerates reduces inter-agglomerate friction, allowing higher polymer loading and higher thermal conductivity. The spherical hBN powder exhibits more isotropic thermal conductivity and higher thermal conductivity through the thickness of the polymer.
However, thermal contact resistance between the source or device and the heat sink limits the effective heat removing capability of the heat sink.
% becomes difficult.
This shape is not ideal for optimizing solids loading due, primarily, to the following reasons: (1) non-spherical shaped agglomerates do not slide against each other easily, thus raising the viscosity; and (2) non-spherical shaped agglomerates have higher surface area and hence absorb greater amounts of polymer on their surface which results in lower amounts of free available polymer, thus, once again raising the viscosity.
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The correct amounts of powders and liquids set forth in Table 1 were measured out. The deionized (DI) water was then pH adjusted to 9-9.5. Surfactant was added to isopropylalcohol (IPA) in a large “final mix” sized bucket (Nalgene Nunc, Rochester, N.Y.), approximately 10 L. The surfactant / IPA solution was agitated using air powered propeller mixer (Lightnin, Rochester, N.Y.). Powder was slowly added to the surfactant / IPA solution un...
[0081]The addition of sintering additives to BN powder was ideally done in a slurry form. This helped create a homogeneous blend of BN and sinter aid. If slurry blending was not possible or practical, a dry mixing method was used.
[0082]The technique used to make dry mixes depended on the amount of sample required. If the sample size was approximately less than 25 g, a mortar and pestle was used to mix the powders. The powder was mixed like this for 10 minutes then used as needed.
[0083]If larger amounts of powder were needed, a paint shaker was used to blend the powders. When using the paint shaker, ⅜″ Si3N4 media was used in a Nalgene Nunc container (Rochester, N.Y.) to assist in blending powders. The amount of media used was approximately ¼ the height of the powder column in the Nalgene container. An appropriately sized container was used for each size batch. The paint shaker was set to run for 25 minutes and mixing began. After mixing, Si3N4 media was ...
[0084]The BN slurry of Example 1 was spray dried in order to produce a BN powder for die-fill applications. Spray drying also afforded the quickest way to produce a homogeneous, multi-component, pressureless sinter powder system. Although a 50 wt. % solids BN slurry seemed very highly loaded compared to other ceramic systems, it contained significant amounts of water. In order to evaporate all this water in the available residence time, and inlet and outlet temperatures had to be increased. Along with these changes, the flow rate of the slurry was slowed down and the revolutions per minute (rpm) of the atomizer increased. In addition, 4 wt. % glycerol was added into the slurry before spray drying if it was going to be used for dry pressing applications. During spray drying, the slurry was constantly mixed.
[0085]The inlet temperature was set to 235° C. which gave an outlet temperature of 85° C. The flow rate of the slurry was 60 ml / minute and the atomizer (Pe...
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Abstract
The present invention relates to a method for making a hexagonal boron nitrideslurry and the resulting slurry. The method involves mixing from about 0.5 wt. % to about 5 wt. % surfactant with about 30 wt. % to about 50 wt. % hexagonal boron nitridepowder in a medium under conditions effective to produce a hexagonal boron nitrideslurry. The present invention also relates to a method for making a spherical boronnitridepowder and a method for making a hexagonal boronnitride paste using a hexagonal boronnitride slurry. Another aspect of the present invention relates to a hexagonal boron nitride paste including from about 60 wt. % to about 80 wt. % solid hexagonal boron nitride. Yet another aspect of the present invention relates to a spherical boron nitridepowder, a polymer blend including a polymer and the spherical hexagonal boron nitride powder, and a system including such a polymer blend.
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[0001]More than one reissue application has been filed for the reissue of U.S. Pat. No. 6,645,612. U.S. Reissue application Ser. No. 11 / 266,751, filed Nov. 3, 2005, is co-pending with the present reissue application. FIELD OF THE INVENTION[0002]The present invention relates to a method for making a hexagonal boron nitride slurry, a method for making a hexagonal boron nitride paste, and a method for making a spherical hexagonal boron nitride powder. The present invention also relates to the resulting hexagonal boron nitride slurry, paste, and spherical hexagonal boron nitride powder, and the use of the spherical hexagonal boron nitride powder in a polymer blend and system including a heat source and a heat sink.BACKGROUND OF THE INVENTION[0003]Microelectronic devices, such as integrated circuit chips, are becoming smaller and more powerful. The current trend is to produce integrated chips which are steadily increasing in density and perform many more functions in a given period of ti...
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