JP2001523892A - Thermal management device - Google Patents

Abstract

  (57) [Summary] A thermal management device comprising at least one heat pipe and a molded heat sink in thermal communication therewith, wherein the heat sink comprises a filled resin composition having a thermal conductivity of greater than about 5 W / mK. The device, wherein the composition comprises from 10 to 80% by weight of the thermally conductive filler and from about 90 to about 20% by weight of the resin, based on the total weight of the filler and the resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001] This application is related to US Provisional Application No. 60 / 065,41, filed Nov. 13, 1997.
Claim 8 advantage.

[0002] The present invention relates to a heat pipe apparatus for heat management, and more particularly to an improved heat management device including a heat pipe element and a molded heat sink element. Still more particularly, the invention relates to a thermal management device comprising a heat pipe element in thermal communication with a heat sink element, wherein the heat sink element is a moldable, thermally conductive, filled polymer, preferably an injection molded polymer. The invention relates to such a thermal management device, comprising a moldable, thermally conductive, filled liquid crystal polymer. Preferably, the thermal management device is formed as a unitary structure by an insert molding operation.

[0003] The market segment of electrical devices, such as for motors, transformers and solenoid windings, is increasingly moving toward miniaturization of such devices. This in turn raises the operating temperature of internal equipment, creating not only the need for high heat rating of the insulation used in these applications, but also the need for improved methods for heat removal and dissipation. . Heat generation, for example, laser diodes,
A problem in a wide variety of electronic devices consisting of semiconductor elements, such as light emitting diodes, thyristors, microwave electron transfer devices, and the like. For example, a semiconductor or multi-chip module consisting of single crystal silicon with countless transistors located on or near one side of the chip generates a significant amount of thermal energy during operation. Removal of by-product heat is important for the useful life of electronic components, and the art is continually developing improved thermal management systems and methods for managing the high levels of thermal output associated with such devices. I'm asking.

[0004] Thermal management has long been the subject of extensive research and investigation. Early implementations were based on the use of heat sinks, including carriers and housings, composed of metals and alloys selected for their high thermal conductivity, and such devices have found widespread application. Continue to headline. More recent innovations and improvements in materials include, for example, the combination of a metal housing with a metallized diamond tip or wafer, which attempts to take advantage of the fact that diamond has the highest thermal conductivity known. ing. In particular, the obvious disadvantages of diamond-based devices, including the practical problems caused by the limited size and high cost of diamond elements, are the metal matrix composites containing diamond particles as fillers to increase thermal conductivity. The development of the material has resulted. Other solutions to the thermal management problem, specifically designed for use with high power density devices, include a liquid cooled heat sink structure and a chip module housing based on liquid nitrogen as a coolant.

[0005] A disadvantage of prior art structures lies in the complexity associated with their manufacture. Generally, thermal management devices are composed of metal, primarily due to the need for good heat conduction combined with good mechanical properties. There is a significant coefficient of thermal expansion (CTE) difference between most metals used in thermal management devices and the electronic components to be cooled, and between these components and the plastic cases and components that house the device. Exists. It is believed that these differences impart significant mechanical stress to the mating elements, creating opportunities for breakage during use. Harmonizing the CTE properties of the heat sink material with the CTE properties of the semiconductor is difficult to machine and requires the use of high density alloys that significantly increase the weight of the device. Compensation for large differences in CTE is also made, but requires complex designs that make manufacturing difficult. Furthermore, effective heat dissipation by convection is a function of surface area. As the thermal load increases, it becomes necessary to use convective heat exchange elements with a larger surface area, which further increases the weight and adversely affects the design flexibility.

[0006] Low density materials have been proposed as metal substitutes for thermal management. Structures containing carbon or crystalline graphite are particularly attractive, both materials are highly thermally conductive,
CT, which has a much lower density than the metal they replace, and is low, even negative
It can be made into a structure having E. Although lightweight graphite and carbon-carbon composites are known and accepted for use in heat sinks and thermal management applications, it is generally difficult to manufacture complex structures from these materials, so Elements are expected to be more expensive than elements composed of metal.

[0007] Thermoplastics with good moldability are readily available, as are castable, moldable thermosets. However, resin generally has a high coefficient of thermal expansion and is a poor conductor of heat. Few can withstand thermal cycling over a wide range of temperatures without experiencing creep or warp failure, or, in the case of hard thermosets, crack formation or similar failure due to thermomechanical stress. CTE
Adding fillers to resins as a way to reduce dimensional stability and thereby improve dimensional stability is well known and widely used in the resin manufacturing arts, and is also useful for improving thermal conductivity. It is thought to be clear. Particulate materials including conductive carbon or graphite fillers, various metals, spherical particles of glass or carbon black, non-spherical metal or ceramic particles, stainless steel filaments, aluminum fibers and the like are disclosed in the art, Has been characterized as particularly useful where improvement of However, only marginal improvements have been made when resins containing these fillers are used for thermal management purposes. Generally, filled thermosetting resins used commercially in the electronics industry are two to two.
Disclosed are injection moldable filled thermoplastic compounds having a thermal conductivity on the order of 4 W / mK, but having a thermal conductivity in the range of 4-9 W / mK. Even the highest conductivity filled resin formulations disclosed in the art have a thermal conductivity of less than 10 W / mK, and most commercially available fillers containing highly conductive fillers such as, for example, metal filaments and the like. Available filled resins generally have very low thermal conductivities, as low as 2-3 W / mK. Therefore, filled resins, especially filled thermoplastics, have only found limited acceptability, where the heat load is low and where miniaturization of the heat exchange device size is not an important design factor. It is generally well suited for use in

More recently, computer manufacturers have turned to heat pipes as a means to effectively and quickly transfer and further dissipate heat from heat sources, such as microprocessor semiconductor elements. Typically, the heat pipe is a hollow metal tube partially filled with a fluid, but alternatives, including a heat pipe containing a solid thermally conductive material, can be used for these structures. In use, the evaporator or heat input zone of the heat pipe is thermally coupled directly to the semiconductor structure being cooled or, more generally, to an inserted heat sink in thermal communication with the device. .
Heat extracted to the heat pipe cooler or heat dissipation zone is dissipated to the environment by thermally coupled cooling fins or second heat sink elements such as, for example, heat plates.

Since good heat transfer between the elements is important for effective and efficient operation, metal fins and heat sink elements are typically swaged, soldered or brazed to heat pipes. Alternatively, the elements can be brought into mechanical contact by fasteners, clamping devices, etc., and thermally conductive adhesives have been used for these purposes. If the heat pipe element of the assembly is intended to be displaced, e.g., rotatably or slidably, with respect to the heat sink element during use, and thus cannot be permanently fixed, filling the gap, Parts (par
ts) to provide a continuous contact area between the contact surfaces.
) Is used. See U.S. Patent No. 5,598,320. Heat pipes serving as pintles or hinge pins and gadion receiving the pintles
A hinged computing device that transfers heat to the display housing through a gudgeon is also disclosed. See U.S. Patent No. 5,621,613.

[0010] It is also known in the art to produce heat pipe panels having internal micro heat pipes by forming channels in a substrate and then enclosing these channels. For example, a vapor-deposited tungsten or tungsten-rhenium alloy heat panel having an internal tubular passage forming a microheat pipe is also disclosed. See U.S. Patent No. 5,598,632.

[0011] Although the use of heat pipes can greatly improve the efficiency of heat removal, the heat removed is then usually dissipated to the environment, which is generally the case with heat pipes such as thermal panels. Requires the use of a sink. In fact, these latter elements most often take the form of a hard metal structure, such as a hot plate, placed in thermal communication with the environment, as an external feature or structural element of the case of the portable electronic device. Thus, the requirements imposed by the thermal management device still seem to affect and limit the flexibility of the design, while at the same time increasing the total weight of the device.

The art still seeks more flexible solutions to the thermal management problem. Even though further improvements in heat removal have been achieved, the heat load continues to increase due to the demand for smaller electronic devices. In order to adequately dissipate the removed heat to the environment, the size of the heat sink must also increase, which in turn impedes the miniaturization trend. Thermal management devices, including heat dissipating means formed from thermally conductive, low density, easily molded structural materials suitable for use as case elements in electronic devices, represent a promising advance in the field of thermal management. Conceivable.

SUMMARY OF THE INVENTION [0013] The improved thermal management device of the present invention includes a heat pipe in thermal communication with a molded thermally conductive heat sink containing a filled thermally conductive resin. The resin may be thermoplastic or thermoset. Examples of thermoplastics suitable for the present invention are liquid crystal polymers (LC
Ps), aliphatic polyamides, polyphthalamides, acrylonitrile butadiene styrene resins (ABS), and polyaryl ether resins such as PPO and PPS resins. Some thermosetting resins are also suitable for use in the present invention, including epoxy resins, cyanate resins, thermosetting polyester resins, and phenolic resins. Thermosetting resins are particularly useful when transfer molding is used to produce a molded heat sink. Other molding methods are possible, for example, compression molding and injection molding.

In one preferred embodiment, a heat sink element is injection molded from a thermally conductive filled liquid crystal polymer. Insert the heat pipe into the molded heat sink,
Preferably, insert molding provides a one-piece unitary structure with excellent heat transfer properties, so that specific portions of the heat pipe are in thermal communication with the heat sink element without the need for heat resistant grease or the like. In another embodiment, the heat sink element is compression molded from a thermally conductive filled epoxy resin.

[0015] The good thermal properties and dimensional stability and excellent mechanical strength of the filled LCP resin provide low molding shrinkage and injection into parts with tight tolerances and very thin sections. Together with the ease of fabrication by molding, these thermally conductive molding compounds are particularly well suited for the construction of elements with complex designs that are very desirable and useful, especially in thermal management for electrical and electronic devices. To

DETAILED DESCRIPTION In a preferred embodiment, the thermal management device of the present invention comprises at least one heat
The pipe includes one or more molded thermoplastic or thermoset heat sink elements.
For the purposes of the present invention, a heat sink includes any structure through which heat is transferred.

[0017] Thermoplastic and thermoset formulations suitable for these purposes are thermally conductive, and preferably also have a thermal conductivity of greater than about 15 W / mK, and as high as 600 W / mK or more. However, at a temperature that does not damage the heat pipe, molding can be easily performed by the high melt flow at this molding temperature. Generally 7x1
0 ⁶ psi greater than, have a high tensile modulus values, thermoplastic formulations which can be expressed to be similar to the rigidity and hardness of the light metal, including magnesium and aluminum is even more preferred.

A preferred thermosetting formulation suitable for use in the present invention comprises a discontinuous, pitch-based carbon fiber filled thermosetting resin, such as an epoxy resin. Thermosets are well known and described in the art and are characterized by having a low density in an uncured state that facilitates wet out of carbon fibers.

A preferred thermoplastic compound suitable for use in the practice of the present invention comprises a discontinuous, pitch-based carbon fiber filled, liquid crystal polymer (LCP) resin.

LCP resins are well known in the art and have been described. Those further characterized as thermotropic liquid crystal polymer (LCP) resins exhibit optical anisotropy when melted, with a significantly lower melt viscosity at the melt production temperature. Such LCP resins, when further compounded with high levels of filler, up to as high as 75% by weight based on the weight of resin and filler, have good melt processing characteristics (m
Maintain elt processing character) and moldability.

Preferred LCP resins are aromatic polyesters derived from monomers selected from one or more aromatic dicarboxylic acids and one or more aromatic diols, together with one or more aromatic hydroxycarboxylic acids.

Typical examples of aromatic dicarboxylic acids used to form LCP resins useful in the practice of the present invention include, for example, terephthalic acid, 4,4′-diphenyldicarboxylic acid, 4,4
'-Triphenyldicarboxylic acid, 2,6-naphthalenedicarboxylic acid, diphenylether-4,4'-dicarboxylic acid, diphenoxyethane-4,4'-dicarboxylic acid, diphenoxybutane-4,4'-dicarboxylic acid, diphenyl Ethane-4,
4'-dicarboxylic acid, isophthalic acid, diphenyl ether-3,3'-dicarboxylic acid, diphenoxyethane-3,3'-dicarboxylic acid, diphenylethane-3,
Aromatic dicarboxylic acids such as 3'-dicarboxylic acid and naphthalene-1,6-dicarboxylic acid, and for example, chloroterephthalic acid, dichloroterephthalic acid, bromoterephthalic acid, methylterephthalic acid, dimethylterephthalic acid, ethylterephthalic acid, methoxyterephthalic acid Derivatives of the above aromatic dicarboxylic acids substituted by alkyl, alkoxyl or halogen, such as acids and ethoxyterephthalic acid.

Aromatic diols that may be found useful in forming LCP resins include hydroquinone, resorcinol, 4,4′-dihydroxydiphenyl, 4,4′-dihydroxytriphenyl, 2,6-naphthalenediol, 4'-dihydroxydiphenyl ether, bis (4-hydroxyphenoxy) ethane, 3,3'-dihydroxydiphenyl, 3,3'-dihydroxydiphenyl ether, 1,6-naphthalenediol, 2,2-bis (4-hydroxyphenyl) propane , 2,2-
Bis (4-hydroxyphenyl) methane and the like and the above aromatic diols such as, for example, chlorohydroquinone, methylhydroquinone, 1-butylhydroquinone, phenylhydroquinone, methoxyhydroquinone, phenoxyhydroquinone, 4-chlororesorcinol, 4-methylresorcinol and the like Alkyl, alkoxy or halogen derivatives of

Aromatic hydroxycarboxylic acids that may be found to be useful in forming LCP resins include 4-hydroxybenzoic acid, 3-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 6-hydroxy-1-naphthoic acid Acids and the like, for example, 3-methyl-4-hydroxybenzoic acid, 3,5-dimethyl-4-hydroxybenzoic acid, 2,6-dimethyl-4-hydroxybenzoic acid, 3-methoxy-4-hydroxybenzoic acid, , 5
-Dimethoxy-4-hydroxybenzoic acid, 6-hydroxy-5-methyl-2-naphthoic acid, 6-hydroxy-5-methoxy-2-naphthoic acid, 3-chloro-4-
Hydroxybenzoic acid, 2-chloro-4-hydroxybenzoic acid, 2,3-dichloro-4-hydroxybenzoic acid, 3,5-dichloro-4-hydroxybenzoic acid, 2,
5-dichloro-4-hydroxybenzoic acid, 3-bromo-4-hydroxybenzoic acid, 6-hydroxy-5-chloro-2-naphthoic acid, 6-hydroxy-7-chloro-2-naphthoic acid and 6-hydroxy- Includes alkyl, alkoxy or halogen derivatives of the aromatic hydroxycarboxylic acids, such as 5,7-dichloro-2-naphthoic acid and the like.

LCP resins containing thio-containing analogs of these monomers, such as amide analogs derived from aromatic thiol carboxylic acids, dithiols and aromatic thiol phenols, and hydroxylamines and aromatic diamines are also known in the art. These resins are known and are believed to prove useful in the practice of the present invention.

As noted above, polymers useful in the practice of the present invention are LCP resins that are anisotropic in the molten state. The specific factors selected to determine whether the polymer is anisotropic in the molten state, the composition ratio and sequence distribution in the polymer
The skilled artisan will understand that this is dictated by on) and therefore will select the monomers and composition parameters according to experience and according to common knowledge and practice in the LCP resin art.

Particularly preferred LCP resins for use in the practice of the present invention contain a naphthalene moiety such as, for example, 6-hydroxy-2-naphthoyl, 2,6-dioxynaphthalene or 2,6-dicarboxynaphthalene, and the like. The repeating unit contains at least about 10 mole%, preferably about 10 to about 90 mole%. About 10-90 mol%, preferably about 65-85 mol%, more preferably 70-80 mol% of such naphthalene units are replaced with about 90-10 mol%, preferably 20-30 mol% of hydroxybenzoic acid -Polyesters which are contained together with the derived units are particularly useful. About 30 to about 7
0 mole%, preferably about 40 to about 60 mole%, of hydroxybenzoic acid units and about 2
It is believed that polyesters containing from 0 to about 30 mole% of 2,6-naphthalene diol derived units and from about 20 to about 30 mole% of terephthalic acid derived units will prove useful.

[0028] Other typical examples of LCP resins that may prove useful are from about 20 to
About 40 mol%, preferably 20 to 30 mol%, of 6-hydroxy-2-naphthalic acid-derived units; 10 to about 50 mol%, preferably about 25 to 40 mol% of hydroxybenzoic acid-derived units; About 10 to 90 mole%, preferably about 15 to 25 mole% of a hydroquinone-derived unit and 5 to about 30 mole%, preferably about 15 to 25 mole% of a terephthalic acid-derived unit; A polyester containing from 5 to about 45 mol% of terephthalic acid derived units and from about 5 to about 45 mol% of hydroquinone derived units; about 1 mol% of 6-hydroxy-2-naphthalic acid derived units;
0 to 40 mol% of 6-hydroxy-2-naphthalic acid-derived units are added in about 10
A polyester containing -40 mole% of terephthalic acid-derived units and hydroquinone-derived units; and about 60-80 mole% of 6-hydroxy-2-naphthalic acid-derived units, each of about 10-20 mole% of terephthalic acid-derived units. And hydroquinone-derived units.

The molecular weight of the LCP resin used in the practice of the present invention depends on the intrinsic viscosity (intrinsic viscosity) of the resin.
viscosity, expressed by (IV), is at least about 0.1 dl / g, preferably from about 0.1 to about 0.1% by weight when dissolved in pentafluorophenol at 60 ° C. at a concentration of 0.1% by weight. It is in the range of about 10.0 dl / g.

[0030] LCP resins and methods of making them are well known in the art and have been extensively described, and many suitable LCP resins are readily available from commercial sources. Xydar® L by Amoco Polymers
LCP resins sold as CP resins are particularly suitable.

[0031] Thermally conductive fillers suitable for use in the practice of the present invention include aluminum nitride, boron nitride, alumina, graphite, pyrolytic graphite, aluminum, copper and other metal particles, diamond, silicon carbide, preferably carbon. Fibers.

[0032] Carbon fibers suitable for use in the practice of the present invention include highly graphitized carbon fibers made from pitch and having high thermal conductivity and low or negative coefficient of thermal expansion. As used herein, the term "carbon fiber" is intended to include graphitized, partially graphitized, and non-graphitized carbon reinforced fibers or mixtures thereof. Preferred carbon fibers are greater than about 600 W / mK, preferably greater than about 900 W / mK.
Even more preferred are pitch based carbon fibers having a thermal conductivity greater than 1000 W / mK. Fibers having a higher thermal conductivity from about 1300 W / mK to a thermal conductivity of single crystal graphite of 1800 W / mK or more are also suitable.
A thermally conductive composition can also be obtained using pitch-based carbon fibers having a low thermal conductivity of the order of 300 W / mK.

Thermal conductivity within the range of 600 W / mK to greater than 1100 W / mK, density from 2.16 g / cc to greater than 2 g / cc, and 110 × 10 ⁶ psi to greater than 120 × 10 ⁶ psi. Pitch-based carbon fibers with very high tensile modulus are readily available from commercial sources. Commercial carbon fibers typically comprise a plurality of carbon filaments, typically from 1000 to 20,000 or more, having a diameter of 5 to 20 microns, the axially aligned filaments providing continuous carbon fiber tow to provide strength in the fiber direction of the tow or Supplied in yarn form.

In general, when using discontinuous fibers, the fibers are generally chopped tow having a length greater than 1/4 ", usually from about 1/4" to about 3/4 "in length. Or about 25 to 1000 μ, preferably about 50 μm, obtained by grinding or granulating carbon fiber.
It can be carbon particles having a length of about 200 μ.

By generally following the methods and means commonly used in the resin compounding field, the thermoplastic resin, including the LCP resin, and the carbon fibers can be easily mixed and compounded. For example, the discontinuous carbon fibers can be dry mixed or similarly combined with the dry resin of any convenient shape using any suitable conventional mixing means and then fed to a compounding extruder, thereby providing additional A filled extrudate is obtained that can be shredded for use in the manufacturing process. Alternatively, the thermoplastic resin, along with the required amount of carbon fiber in the form of continuous carbon fiber tow, may be fed to a single screw extruder and extruded or pultruded as strands and chopped to form pellets. And collect. Thermosetting resin and carbon fiber can be easily mixed and blended by dry blending, or a mixer, extruder, stirrer,
It can be compounded by a roll mill and an impregnating device such as, for example, a prepreg machine. In addition, dipping, spraying or other application processes can be used.

As is generally known in the art, further processing of glass fibers, carbon fibers or similar brittle fiber fillers using shearing means, such as extruders, injection molding machines, etc., generally involves: Break the fibers, further reducing the size of the fibrous particles.
Next, the average size of the particles in the filled compact produced by high shear processing means generally ranges from 35 to irrespective of whether the fibers are supplied as a continuous tow from the beginning or as chopped or ground fibers. The aspect ratio of the filler is in the range of 200μ and greater than about 4, averaging up to about 10. Fiber damage and destruction is minimized, for example, when processing using low shear conditions by compression or transfer molding, or when used in flowable formulations as found in potting resin applications. The shaped body is a fairly large length of fiber, corresponding to a length of the order of 100μ to 1/4 ", i.e. ranging from the original length of chopped tow fiber, generally greater than about 10; Containing fibers having a high aspect ratio.

Generally, the filled resin formulation useful in the practice of the present invention will comprise from about 20% to about 80% by weight.
Preferably from about 45 to about 80%, even more preferably from about 60 to about 75% by weight of carbon fiber, and correspondingly from about 80 to about 20% by weight, more preferably from about 55 to about 20% by weight, Most preferably, from about 40 to about 25% by weight of the resin. The formulation may further include plasticizers and processing aids, as well as heat stabilizers, oxidation inhibitors, flame retardants, reinforcing fillers, as commonly used in the compounding arts for use with such molding resins. Additional fillers, including fibers, dyes, pigments and the like can be included. It will be readily appreciated that the utility of the filled molding compounds of the present invention lies in the sufficient thermal conductivity exhibited by the material. Accordingly, these additional factors and the amounts used are selected to avoid or at least minimize the thermal conductivity of the formulation.

Preferably, the filled resin is injection molded through a heat pipe using an insert molding operation to provide a unitary structure. The insert molding process typically involves placing the insert in a mold and injecting a plastic material around the insert or a desired portion of the insert to complete the element. In the practice of the present invention, a heat pipe is inserted into a mold, then filled with a filled LCP resin, surrounding the desired portion of the heat pipe and filling the mold to form a heat sink.
The filled LCP resin, when cooled, forms a molded heat sink element having an approximate interference fit at all points of contact with the surface of the heat pipe, providing excellent heat transfer between the elements.

As will be appreciated, heat pipes are damaged when exposed to high temperatures or pressures. Heat pipes are intended to operate in a particular environment and within a particular temperature range that depends in part on the working fluid, materials of construction and design. To prevent breakage of the heat pipe due to excessive compression, the end seal of the heat pipe can be designed to burst when exposed to temperatures significantly above the design upper limit. Further, if the heat pipe is subjected to high external pressure or other severe mechanical stress, the pipe will bend or distort, rendering it unusable. Highly filled polymers are generally difficult to injection mold, forming viscous melts that flow hard and require high injection pressures with stock temperatures well above the polymer melt temperature to fill the mold cavities. I do. Uneven flow of the high viscosity melt in the mold cavity exposes the heat pipe insert to severe mechanical stress, distorting the pipe,
You can even bend and fold. Filled LCP resins, such as LCP resins used in the practice of the present invention, have low melt viscosities and are well within the design limits of many heat pipes at 400-700 ° F (200-370 ° C). To allow molding with relatively low melt temperatures in the range. In addition, damage to the heat pipe due to mechanical stress is avoided because no excessive injection pressure is required to fill the mold.

As long as these formulations are thermoformable, the filled LCP resin can be heat piped using any of a variety of conventional molding equipment and processes suitable for use in insert molding operations. To form a unitary thermal management device according to the present invention.

A wide variety of extrudable and injection moldable thermoplastic resins other than LCP resins are generally known in the art, and such resins are also filled with high modulus carbon fibers and injected. When forming a thermally conductive resin that is moldable, it is believed that g will prove suitable for the present invention. Aliphatic polyamides, including those widely available, such as, for example, nylon 6, nylon 6,6, nylon 4,6, nylon 11, and the like; for example, hexamethylene diamine, 2-methylpentamethylene diamine, and the like. Commercially available polymers of one or more aliphatic diamines with terephthalic acid compounds and copolymers thereof with additional dicarboxylic acid compounds such as, for example, isophthalic acid, adipic acid, naphthalenedicarboxylic acid, etc. Polyphthalamide including; polyethylene terephthalate (PET)
Resins, polyarylate resins, including polybutylene terephthalate (PBT) resins; arylene polycarbonate resins, including poly (bisphenol A carbonate); PPOs, including thioether analogs thereof, such as PPS resins, etc.
Known polyarylether resins, such as resins, and the corresponding sulfone- and ketone-linked polyarylethers, such as polyethersulfone, polyphenylethersulfone, polyetherketone, polyphenyletherketone, and the like, are well known. Filled and unfilled resin formulations containing various thermoplastic resins are readily available from a variety of commercial sources.

[0042] Such thermoplastic resins, when filled with thermally conductive fillers, including carbon fibers as described herein above, may become thermally conductive suitable for many thermal management applications. Conceivable. However, to obtain the high level of thermal conductivity required for heat sinks that dissipate heat without the need for significant increase in surface area and for other thermal management applications where high heat loads are expected, It is generally necessary to use high levels of carbon fiber loading, of the order of at least 45% by weight, preferably 50-80% by weight. When filled to these levels, most such thermoplastic materials are extremely difficult to mold, making them less suitable for insert molding operations using heat and pressure sensitive inserts such as, for example, heat pipes. Unsuitable pressures and high temperatures may be required.

[0043] Thermoconductive filled thermosetting resins are also known, and most of them are thermally conductive potting materials, encapsulating materials, adhesive materials and coating materials, as well as sheet molding compounds, bulk molding compounds, and the like. It is used commercially for thermal management, especially for electronics applications. Conventional thermosetting resins, including epoxy resins, cyanate resins, novolaks, resols and similar thermosetting phenolic resins, thermosetting polyesters, and the like, can be cut into chopped carbon fiber tows as described herein above. Alternatively, it can be advantageously mixed with pulverized or granular carbon fibers to obtain thermosetting molding resins and materials having a suitable thermal conductivity for use in thermal management devices. Such formulations can be manufactured and molded by conventional means, usually using a compression or transfer molding process or using the B-state resin composition in a thermoforming step or the like. When properly molded and then thermoset or cured, along with dimensional stability at elevated temperatures, which is generally recognized as a characteristic of most thermoset materials,
It is possible to obtain a filled resin molded article having a high thermal conductivity of ５5 W / mK to 80 to 100 W / mK or more depending on the usage level of the filler. Filled elastomers that can be thermoformed and cured to produce tough, flexible parts are also known in the art, and they can also be made thermally conductive by use of suitable fillers. .

Examples The following materials are used in the following examples: K-1100X Amoco Performance Products
Carbon fiber obtained from Thornel® UHM carbon fiber K1100X, according to published specifications, a tensile modulus of about 130 × 10 ⁶ psi, a density of 2.21 g / cc, and a thermal conductivity of 1100 W / mK. Have.

P-120 Carbon fiber obtained as Thornel® carbon fiber P-120 from Amoco Polymers, according to published specifications:
It has a tensile modulus of about 120 × 10 ⁶ psi, a density of 2.17 g / cc, and a thermal conductivity of 900 W / mK.

E600X Carbon fiber obtained as Thornel® carbon fiber E-600X from Amoco Polymers, according to published specifications, a tensile modulus of about 120 × 10 ⁶ psi, a density of 2.14 g / cc, and It has a thermal conductivity of 600 W / mK.

Radel A A polyether sulfone resin obtained from Amoco Polymer as Radel® A3800 polyaryl ether sulfone.

PPA-1 Polyphthalamide resin Nylon 6,6 polyhexamethylene adipamide LCP obtained from Amoco Polymers as Amodel® polyphthalamide resin LCP Xydar® SR from Amoco Polymers
Liquid crystal polymer obtained as T900 resin.

Mechanical properties were measured by ASTM standardized test methods unless otherwise specified.

Thermal conductivity is obtained from measurements of power / heat input and temperature differences along multiple paths and measurements of cross-sectional heat flow under steady-state conditions. The device was calibrated using aluminum or copper panels of known thermal conductivity.

The thermal conductivity is calculated using Fourier Construction Law: q = KA · ΔT / ΔX: where q = input; A = cross-sectional area; K = thermal conductivity; ΔT = direction of heat flow And ΔX = distance between temperature measuring devices. Data is reported in W / mK.

[0052] (filled resin composition) Example 1. X to chopped K-1100 carbon fiber tow with nominal length of 1/4 "
ydar LCP resin pellets are dry-mixed and extruded (extrusion compoun
ded) and chopped to obtain a filled resin pellet containing 45% by weight of the target level of carbon fiber. Specimens (6 "x 6" x 1/16 ") were prepared by injection molding dried resin pellets using an HPM 75 ton injection molding machine and the properties are summarized in Table I.

Examples 2 to 5 Substantially according to the method of Example 1, a series of filled Xydar resins were obtained at carbon fiber levels of 10, 45 and 60% by weight. The pellets were injection molded as in Example 1 to obtain flat panels and 4 "x 4" x 1/8 "specimens. The thermal conductivity is summarized in Table I below.

[0054]

[Table 1]

It is clear that formulations containing less than about 20% by weight of carbon fibers do not have sufficient thermal conductivity. With some variation, the filled material can be shaped to be anisotropic with respect to thermal properties or to be substantially isotropic in the plane of the shaped body. For most systems, there is some degree of fiber alignment along the fiber plane, and there appears to be a large degree of alignment that occurs most frequently in the direction of flow. However, the property perpendicular to the flow surface indicates that three-dimensional fiber orientation occurs in most injection molded articles.

The composition according to the invention can also be produced with other thermoplastic resins to obtain thermally conductive parts.

Embodiments 6 and 7 Killion 1.5 "single screw extruder continuously K-1
By supplying 100X carbon fiber with polysulfone resin, continuous K-1
Radel polyethersulfone was blended with 100X carbon fiber, the blended resin was extruded into strands, and the strands were chopped to form filled polysulfone pellets. The feed rate was adjusted to obtain strands with 18% and 33% target carbon fiber levels. The pellets were then dried and compression molded to obtain 4 "x4" x1 / 8 "coupons for use as test specimens.

Embodiment 8 FIG. By feeding the resin and continuous K1100X carbon fiber to the extruder at a feed rate adjusted to obtain a rod having a target level of carbon fiber of 60% by weight, the pultruded rod is converted to nylon 6,6. From No. 6. The pltruded rods were chopped to give 1/2 "pellets. Test plaques were injection molded from the dried pellets using a 75 ton HPM injection molding machine. Properties are summarized in Table II.

Embodiments 9, 10 and 11 PPA-1 resin pellets are dry blended, extruded and chopped into shredded E-600X carbon fiber tow having a nominal length of 1/4 "to achieve a target level of carbon of 10, 50 and 70% by weight. Specimens were prepared by injection molding dry resin pellets as described above, with pellets of filled resin containing fibers, the properties are summarized in Table II.

[0060]

[Table 2]

The composition according to the invention can also be compression molded to obtain thermally conductive parts. Embodiment 12 FIG . 50% by weight of Radel polyethersulfone and 50% by weight
Of a chopped K-1100 carbon fiber tow having a nominal length of 1/4 "was prepared by solution impregnation. The mixture was compression molded to obtain a specimen having thermal properties. The internal (or X and Y directions) thermal conductivity was 90.4 W / mK and 102.9 W / m K. The coefficient of thermal expansion was 4.0 ppm / ° F.

Embodiment 13 FIG. A dry blend of 50% by weight of Radel polyethersulfone powder and 50% by weight of chopped K-1100 carbon fiber tow having a nominal length of 1 "is compression molded to obtain a thermal property specimen. The in-plane (or X-direction) thermal conductivity was 67.8 W / mK, and some difficulty in wetting was observed.

Embodiment 14 FIG. A dry blend of 50% by weight of Radel polyethersulfone powder and 50% by weight of P-120 carbon fiber ground or granulated to obtain 200μ particles is compression molded to provide a thermal property specimen. Obtained. The in-plane (or X direction) thermal conductivity was 37.0 W / mK. Some resistance to wetting was observed.

For example, a thermosetting resin such as a general epoxy potting resin may be filled with carbon fibers, molded and cured to obtain a thermally conductive part.

Embodiment 15 FIG. A filled epoxy composition consisting of 70% by weight of epoxy resin and 30% by weight of P-120 carbon fiber ground or granulated to obtain 200μ particles is obtained by combining the liquid resin and the granules. Prepared by hand mixing, poured into a mold, and the plaque was cured to obtain a specimen of thermal properties. In the plane (
(Or X direction) The thermal conductivity was 15 W / mK.

Example 16 (Insert Molding Thermal Device) Using the 60 wt% carbon fiber filled LCP resin formulation of Example 5, a thermal device including a 3 mm × 160 mm heat pipe and an injection molded heat sink was constructed. A mold cavity having a size of 12 mm × 12 mm × 96 mm was fixed so as to support the heat pipe inserted into the mold cavity with the center placed. The filled LCP resin formulation was then injected into the closed mold using an HPM 75 ton injection molding machine as described above. After removal of the cooled molding, the centering fixture was removed to form a heat pipe fitted in the cooler section to a length of 51 mm in the injection molded resin. The block was then crushed to form a plurality of fins 1 mm thick and 4-5 mm high, these fins were concentrated on the axis of the heat pipe, placed perpendicular to this axis and fitted. 1 mm apart along the length. The total weight of the heat sink was 12 g. The source end of the heat pipe is embedded in the heat transfer block to a length of 14 mm. The heat transfer block was electrically heated with a constant input of 5.5 watts. The temperature of the source and the ambient temperature are measured by a thermocouple, and the temperature rise for a constant input is inversely proportional to the ability of the structure to dissipate heat.

When the ambient temperature is 23 ° C., the die / source temperature is 71 ° C. and 8.6 ° C.
/ Watt thermal resistance.

Comparative example . A 3 x 160 mm heat pipe was placed at the end of the cooler, 13 mm x 20 mm.
It was mounted on a commercial cast magnesium finned heat sink weighing 26 g and measuring 95 mm long with a size of mm × 14 mm long. A thermal additive was applied to the interface between the heat sink and the heat pipe. The source end was embedded in the heat transfer block to a length of 14 mm and heated as in Example 16. Die / source temperature is 71 ° C and ambient temperature is 2 ° C.
5 ° C., resulting in a thermal resistance of 8.3 ° C./watt.

Thus, it can be seen that the injection molded heat sink produces substantially the same heat dissipation as the large, fairly heavy cast magnesium heat sink of the prior art.

It is clear that the molding thermal management device of the present invention represents a substantial advance in the art and provides significantly improved materials for use in thermal management applications. The thermally conductive resin compound used to form the device of the present invention is readily prepared using conventional processing means and is generally a tough material having excellent mechanical properties and good dimensional stability. is there. It is believed that these improved thermally conductive resin molding compounds will find a wide range of applications for use in making thermal management elements.

Thus, the thermal management device of the present invention can be described as including a heat pipe with a molded heat sink, wherein the heat sink element is preferably a heat sink.
It is insert molded with the pipe to form an integral unitary structure. The heat conductive heat sink element may be greater than about 5 W / mK, preferably greater than about 10 W / mK, and more preferably about 80 W / m, depending on the amount of conductive filler in the formulation.
K to a size of the order of 600 W / mK, even more preferably from about 100 to about 4
A thermal conductivity of 50 W / mK, again depending on the type and level of conductive filler,
It can be further characterized as being molded from a filled thermoplastic or thermoset molding compound having a particularly low coefficient of thermal expansion of generally less than 10 ppm / ° C. The filled thermoplastic injection molding compound used in a more preferred embodiment of the present invention comprises from about 80 to about 20%, preferably from about 50 to about 20% by weight of a thermoplastic LCP resin and from about 20 to about 80% by weight. %, Preferably from about 50 to about 8
0% by weight of carbon fiber, said carbon fiber being greater than about 600 W / mK, preferably greater than about 750 W / mK, more preferably greater than about 900 W / mK, and even more. Preferably it has a thermal conductivity of more than 1000 W / mK.

It will be appreciated that the filled resin formulation can further include plasticizers, processing aids, stabilizers, and the like, as commonly used in the resin formulation and resin molding arts. This formulation is particularly suitable for use in the manufacture of thermal management devices for electrical and electronic applications where the art has not had a suitable, easily manufactured material with high thermal conductivity.

[0073] Further modifications and variations will be readily apparent to those skilled in the resin art. For example, a wide variety of heat management devices can be designed using multiple heat pipe elements fitted into a heat sink, including elements in a heat spreader or heat plane, insert molding operation. Will be readily understood by those skilled in the art. For example, the use of additional molding or post-molding operations, including overmolding of thermal management devices, optionally including accessory electrical or electronic components, to form an attached hermetically sealed housing is also contemplated. Can be It will be understood that such further embodiments and modifications are well within the skill of those in the art and are therefore within the scope of the invention as defined by the appended claims. .

[Procedure amendment]

[Submission date] June 15, 2000 (2000.6.15)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

Claims (16)

[Claims] 1. A thermal management device comprising at least one heat pipe and a molded heat sink in thermal communication therewith, wherein said heat sink is about 5 W /
a filled resin composition having a thermal conductivity greater than mK, wherein said composition comprises 10-80% by weight of a thermally conductive filler, based on the total weight of the filler and the resin, and about 90-90%.
About 20% by weight of the resin. 2. A thermal management device comprising at least one heat pipe and a molded heat sink in thermal communication therewith, wherein said heat sink is about 10 Watts.
/ MK comprising a filled resin composition having a thermal conductivity of greater than 10% to 80% by weight carbon fiber and about 90% to about 20% by weight based on the total weight of carbon fiber and resin. The device comprising: a resin. 3. The thermal management device according to claim 2, wherein said resin is a liquid crystal polymer. 4. The thermal management device according to claim 2, wherein said resin is a thermosetting resin. 5. The thermal management device according to claim 2, wherein said resin is a thermoplastic resin. 6. A thermal management device comprising at least one heat pipe and an injection molded heat sink in thermal communication therewith, wherein said heat sink comprises at least one heat pipe.
An injected moldable resin composition having a thermal conductivity greater than 0 W / mK, wherein said composition comprises 20-80% by weight carbon fiber and about 80% based on the total weight of carbon fiber and liquid crystal polymer. About 20% by weight of a liquid crystal polymer. 7. A thermal management device comprising at least one heat pipe and a compression molded heat sink in thermal communication therewith, wherein said heat sink comprises at least one heat pipe.
A compression moldable filled resin composition having a thermal conductivity greater than 0 W / mK, said composition comprising 20-80 wt% carbon fiber and about 80-80 wt% based on the total weight of carbon fiber and resin. About 20% by weight of a thermosetting resin. 8. The device of claim 2, wherein said carbon fibers are pitch-based carbon fibers having a thermal conductivity greater than about 300 W / mK. 9. The device of claim 2, wherein said carbon fibers are pitch-based carbon fibers having a thermal conductivity greater than about 600 W / mK. 10. The device of claim 2, wherein said composition has a thermal conductivity in the range of about 15 W / mK to about 600 W / mK. 11. The device of claim 9, wherein said carbon fibers have a thermal conductivity of greater than about 1000 W / mK. 12. The device of claim 9, wherein said carbon fibers have a thermal conductivity in the range of 600 W / mK to about 1800 W / mK. 13. The thermal management device of claim 1, wherein the device is insert molded to provide a unitary structure having the heat pipe element embedded in the molded heat sink element. 14. The thermal management device of claim 2, wherein said device is insert molded to provide a unitary structure having said heat pipe element embedded within said molded heat sink element. 15. The thermosetting resin according to claim 4, wherein the thermosetting resin is selected from the group consisting of an epoxy resin, a cyanate resin, a thermosetting polyester resin, and a phenol resin.
A thermal management device as described. 16. The thermoplastic resin of claim 5, wherein the thermoplastic resin is selected from the group consisting of polyamide, polyphthalamide, acrylonitrile butadiene styrene resin, polycarbonate resin, polyaryl ether resin, polyphenylene sulfide resin, polysulfone and polyether sulfone. Thermal management device.