Reworkable polysiloxane for thermal interface materials

Abstract

Disclosed are thermal interface materials (TIMs) comprising a thermally reworkable polysiloxane having a thermally reversible cyclic addition functional group on at least one polysiloxane chain. Also disclosed are TIMs comprising a polysiloxane blended with a crosslinked network having a thermally reversible cyclic addition functional group. Also disclosed are methods for providing a TIM comprising a thermally reversible polymer network, a semiconductor package for mounting the TIM, and a computing device comprising the semiconductor package. The thermally reworkable polymer network of the provided TIM comprises at least one polysiloxane chain and a thermally reversible cyclic addition functional group.

Description

[Technical Field]

[0001] This disclosure relates to thermal interface materials (TIMs), and more specifically, to polymer composite TIMs. [Background technology]

[0002] TIMs are widely used in electronic equipment packaging to improve heat conduction across the interface between a heat source (e.g., a chip) and a heat sink (e.g., fins or a cold plate). Roughness of the interface surface creates non-contact areas, and if air enters these areas, the resulting contact thermal resistance (R) between surfaces increases. c ) increases. Therefore, by filling the gaps with TIMs that have a much higher thermal conductivity (k) than air, the contact thermal resistance at these interfaces can be significantly reduced. Examples of TIMs include metals (e.g., liquids, solder, or foils), polymer composites, carbon-based materials, and phase change materials (PCMs). Polymer composite TIMs include a polymer matrix (base material) filled with a thermally conductive material (filler). Flexible matrix polymers can enable higher thermal conductivity than the filler material alone by improving contact between interface surfaces.

[0003] However, TIM is high k, low R cTo meet the increasing demands on semiconductor devices, such as performance and high adaptability, challenges remain. For example, the thermal conductivity of polydimethylsiloxane (PDMS)-based TIMs can be limited by defects and structural irregularities in the polymer, which can act as scattering sites for heat carriers. These defects can lead to undesirable crosslinking, poor adhesion, and crack formation in cured TIMs. Therefore, materials and technologies for preventing or repairing defects in polymers and polymer composite TIMs can lead to improved performance and reliability of semiconductor packages. [Overview of the project]

[0004] Various embodiments relate to thermal interface materials (TIMs) comprising thermally reworkable polymers. The thermally reworkable polymer comprises at least one polysiloxane chain having a thermally reversible cyclic addition functional group. In some embodiments, the thermally reworkable polymer comprises a polysiloxane chain backbone linked by the thermally reversible cyclic addition functional group. In further embodiments, the thermally reversible cyclic addition functional group may be a surface functional group or a side-chain functional group of the polysiloxane chain. In some embodiments, the thermally reworkable polymer can be blended with a thermally conductive filler such as a liquid metal. In some embodiments, the TIM can be reworked to repair voids, cracks, and other defects by applying thermal stimulation. Thus, the TIM can improve package yield and lifespan and facilitate the scaling of multi-chip modules.

[0005] Further embodiments relate to TIMs comprising a crosslinked network and a blended polysiloxane. The crosslinked network comprises a thermoreversible cyclic addition functional group. In some embodiments, the polysiloxane is polydimethylsiloxane or poly(dimethylsiloxane-co-diphenylsiloxane). The thermally reworkable polymer may also be blended with a thermally conductive filler such as graphite, aluminum, aluminum nitride, aluminum oxide, boron nitride, or gallium-based liquid metal. In some embodiments, the TIM can be reworked to repair voids, cracks, and other defects by applying thermal stimulation. Thus, the TIM can improve package yield and lifespan and facilitate the scaling of multi-chip modules. Furthermore, the reworkable polymer blend can advantageously facilitate the distribution of the thermally conductive filler throughout the TIM.

[0006] Additional embodiments relate to a method for providing a TIM comprising a thermally reworkable polymer network including at least one polysiloxane chain and a thermally reversible cyclic adduct. Further embodiments relate to a semiconductor package on which the TIM is mounted, and a computing device comprising the semiconductor package. The reworkability of the polymer network can enable the repair of defects within the TIM. Furthermore, advantageously, the use of TIMs can facilitate the scaling of multi-chip modules. TIMs can provide improved yield and lifespan for semiconductor packages and computing devices. [Brief explanation of the drawing]

[0007] The drawings included herein are incorporated herein and form part thereof. They illustrate embodiments of the herein and, together with the description, serve to illustrate the principles of the herein. The drawings are illustrative of certain embodiments and do not limit the herein.

[0008] [Figure 1]Figure 1A is a flowchart showing the process for preparing an electronic device with a reworkable thermal interface material (TIM) according to several embodiments.

[0009] Figure 1B is a flowchart showing the process of reworking a cured TIM layer according to several embodiments.

[0010] [Figure 2] This block diagram shows some of the electronic device modules that implement a reworkable TIM according to several embodiments.

[0011] [Figure 3] Figure 3A is a chemical structure diagram showing an example of a polysiloxane having a substituted cyclic adduct unit according to several embodiments.

[0012] Figure 3B is a chemical reaction diagram illustrating the process of reworking polysiloxanes, such as the polysiloxane shown in Figure 3A, according to several embodiments.

[0013] [Figure 4] This is a chemical reaction diagram showing experimental examples of thermal stability tests using polysiloxanes according to several embodiments.

[0014] [Figure 5A] This is a chemical structure diagram showing a siloxanecyclopentadiene dimer in several embodiments.

[0015] [Figure 5B] This is a chemical structure diagram showing examples of polysiloxanes having thermoreversible cyclopentadiene dimer units according to several embodiments.

[0016] [Figure 6] This is a chemical structure diagram showing a polysiloxane having furan and maleimide groups that can form thermoreversible dimer units, according to several embodiments.

[0017] [Figure 7A] The proton nuclear magnetic resonance (1H NMR) spectrum and the corresponding chemical structure diagram of the first trifunctional furan crosslinking agent are shown.

[0018] [Figure 7B] The 1H NMR spectrum and the corresponding chemical structure diagram of the second trifunctional furan crosslinking agent are shown.

[0019] [Figure 8A] It is a chemical reaction diagram showing the Diels-Alder reaction between the second trifunctional furan crosslinking agent and N-methylmaleimide according to some embodiments.

[0020] [Figure 8B] It is a set of 1H NMR spectra obtained at three time intervals while monitoring an experimental example of the reaction shown in Figure 8A.

[0021] [Figure 9A] It is a chemical reaction diagram showing the formation of a thermoreversible crosslinked network according to some embodiments.

[0022] [Figure 9B] It is a graph showing the experimental results obtained by dynamic mechanical analysis (DMA) of the crosslinked network shown in Figure 9A.

[0023] [Figure 10] Figure 10A is a chemical reaction diagram showing the rework process of TIM by thermal activation of a potential catalyst according to some embodiments.

[0024] Figure 10B is a set of chemical reaction diagrams showing examples of salts that can be used as catalyst generators according to some embodiments.

[0025] While various modifications and alternative forms are possible with respect to the present invention, their details are illustrated in the drawings and described in detail below. However, it should be understood that the intention is not to limit the present invention to the specific embodiments described. Rather, it is intended to cover all modifications, equivalents, and alternatives that fall within the spirit and scope of the present invention. [Modes for carrying out the invention]

[0026] Embodiments of the present invention generally relate to thermal interface materials (TIMs), more specifically polymer composite TIMs. While the disclosure is not necessarily limited to such applications, various aspects of the disclosure can be understood through the description of examples using this context.

[0027] Various embodiments of this disclosure are described herein with reference to the relevant drawings, where similar numbers refer to the same components. Alternative embodiments can be devised without departing from the scope of this disclosure. Note that various connections and positional relationships (e.g., above, below, adjacent, etc.) are shown between elements in the following description and drawings. These connections and / or positional relationships may be direct or indirect unless otherwise specified, and this disclosure is not intended to limit them in this respect. Thus, a joining of entities may refer to either a direct or indirect joining, and a positional relationship between entities may be a direct or indirect positional relationship. As an example of an indirect positional relationship, the reference herein to forming layer "A" on layer "B" includes a situation in which one or more intermediate layers (e.g., layer "C") are located between layer "A" and layer "B", provided that the relevant properties and functions of layer "A" and layer "B" are not substantially altered by the intermediate layer.

[0028] The following definitions and abbreviations are used for interpretation of the claims and specification. Where used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having,” “contains,” or “containing,” or any other variation thereof, are intended to cover non-exclusive inclusion. For example, a composition, mixture, process, method, article, or apparatus containing a list of elements is not necessarily limited to those elements alone, and may include other elements not expressly listed or that are inherent to such composition, mixture, process, method, article, or apparatus.

[0029] For the purposes of the following explanation, the terms “top,” “bottom,” “right,” “left,” “vertical,” “horizontal,” “top,” and “bottom,” and their derivatives, refer to the structures and methods described in the orientation of the drawings. The terms “overlapping on,” “on top of,” “on the top of,” “above,” “located at,” or “located on top of” mean that a first element, such as a first structure, lies on a second element, such as a second structure, where an intervening element, such as an interface structure, may exist between the first and second elements. The term “direct contact” means that a first element, such as a first structure, and a second element, such as a second structure, are connected at the interface of the two elements without any intermediate conductive, insulating, or semiconductor layers. Note that the term “selective,” for example, “a first element selective to a second element,” means that the first element can be etched and the second element can act as an etch stop.

[0030] As used herein, the articles “a” and “an” preceding an element or component are not intended to be limiting in terms of the number of instances (i.e., the number of occurrences) of the element or component. Therefore, “a” or “an” should be interpreted as including one or at least one, and the singular form of an element or component also includes the plural form unless it is clearly implied that its number is singular.

[0031] As used herein, the terms “invention” or “this invention” are non-limiting and are not intended to refer to any single aspect of a particular invention, but rather encompass all possible aspects described in the specification and claims.

[0032] Unless otherwise specified, ranges as expressed herein (e.g., time, concentration, temperature, etc.) include all values ​​at both endpoints and between those endpoints. Unless otherwise specified, the use of tildes (~) or terms such as “about,” “substantially,” “approximately,” “slightly less,” and variations thereof is intended to include the degree of error associated with the measurement of a particular quantity based on the equipment available at the time of filing. For example, “about” may include a range of ±8%, 5%, 2%, or ≤1% of the endpoints of a given value, a range of values, or one or more ranges of values. Unless otherwise specified, the use of such terms in relation to a range applies to both endpoints of the range (e.g., “approximately 1g to 5g” should be interpreted as “approximately 1g to approximately 5g”), and the use in relation to a list of ranges applies to each range in the list (e.g., “approximately 1g to 5g, 5g to 10g, etc.” should be interpreted as “approximately 1g to approximately 5g, approximately 5g to approximately 10g, etc.”). As used herein, n, m, l, and p represent integers of 1 or greater than 1. In this specification, exemplary ranges of integers are provided for polymer / crosslinking agent repeating units, methylene groups, etc., but these ranges may encompass any number of units suitable for the composition. For example, n dimethylsiloxane units can represent polydimethylsiloxane of any suitable molecular weight (MW) (e.g., for TIM applications).

[0033] As used herein, the term “aliphatic” includes the terms alkyl, alkenyl, or alkynyl. Aliphatic radicals or aliphatic groups, such as groups having only carbon-carbon single bonds ("alkyl" or "alkylene"), groups having one or more carbon-carbon double bonds ("alkenyl"), radicals having one or more carbon-carbon triple bonds ("alkynyl"), and groups having a mixture of carbon-carbon single, double, and / or triple bonds, may have any degree of saturation.

[0034] As used herein, the “alkyl” group refers to a saturated aliphatic hydrocarbon group (e.g., C1-C4, C1-C6, or C1-C8 alkyl) containing at least one carbon atom. Alkyl groups can be linear, branched, cyclic, or any combination thereof. Unless specifically limited herein, the term “alkyl” as used herein, as well as its derivatives such as “alkoxy” and “thioalkyl,” includes linear, branched, and cyclic portions within its scope. When an alkyl radical is further bonded to another atom, it becomes an alkylene radical or alkylene group. In other words, the term “alkylene” also refers to divalent linear or branched alkyl groups. For example, -CH2CH3 is ethyl and -CH2CH2- is ethylene. The term “alkylene” refers, alone or as part of another substituent, to a saturated linear or branched divalent hydrocarbon radical obtained by removing two hydrogen atoms from a single carbon atom or two different carbon atoms of a starting alkane.

[0035] Examples of alkyl radicals / partial or alkyl groups include methyl, ethyl, propyl, 1-methylethyl, butyl, 1-methylpropyl, 2-methylpropyl, 1,1-dimethylethyl, pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 2,2-dimethylpropyl, 1-ethylpropyl, hexyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1,1-dimethylbutyl, 1,2-dimethylbutyl, 1,3-dimethylbutyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl, 3,3-dimethylbutyl, 1-ethylbutyl, 2-ethylbutyl, 1,1,2-trimethylpropyl, 1,2,2-trimethylpropyl, 1-ethyl-1-methylpropyl, and 1-ethyl-2-methylpropyl. The alkyl or alkylene groups defined above may be unsubstituted or substituted with one or more substituents listed below.

[0036] As used herein, the term “cyclic” refers to a cyclic compound or group containing at least three carbon atoms, wherein all bonds between adjacent atoms may be of a type called single bonds (containing two electrons), or some of them may be double or triple bonds (containing four or six electrons, respectively). Examples of cyclic aliphatic groups include phenyl and saturated cycloalkyl groups (e.g., cyclopropyl, cyclobutyl, cyclopentyl, or cyclohexyl).

[0037] As used herein, the terms “amine” or “amino” include compounds in which a nitrogen atom is covalently bonded to at least one carbon atom or heteroatom. The terms “amine” or “amino” include -NH2 and also include substituted moieties. The terms include “alkylamino,” which includes groups and compounds in which nitrogen is bonded to at least one additional alkyl group (e.g., a secondary or tertiary amine). As used herein, the terms “imino” group or imino residue mean a divalent group = NR, where R represents either H or an alkyl group as defined herein. As used herein, the term “imide” refers to a group or compound having a nitrogen atom covalently bonded to two carbonyl groups. As used herein, the term “furan” refers to a group or compound having a five-membered aromatic ring containing four carbon atoms and one oxygen atom.

[0038] As described herein, the compounds of this disclosure may be optionally substituted with one or more substituents, such as those outlined above or exemplified by the specific classes, subclasses, and species of this disclosure. As described herein, any of the above portions or those described below may be optionally substituted with one or more substituents as described herein.

[0039] In the context of this disclosure, the term “substituted” means that one or more hydrogen atoms of the indicated radical or group are independently replaced by the same or different substituents. Additionally, the term “substituted” specifically refers to one or more substituents, e.g., two, three, or more, as commonly used in the art. However, it is generally known that substituents should be selected so as not to adversely affect the useful properties or functions of the compound.

[0040] Suitable substituents in the context of this disclosure may, in some embodiments, include halogen groups, perfluoroalkyl groups, perfluoroalkoxy groups, alkyl groups, alkenyl groups, alkynyl groups, hydroxy groups, oxo groups, mercapto groups, alkylthio groups, alkoxy groups, aryl or heteroaryl groups, aryloxy or heteroaryloxy groups, arylalkyl groups or heteroarylalkyl groups, arylalkoxy or heteroarylalkoxy groups, amino groups, alkyl and dialkylamino groups, carbamoyl groups, alkylcarbonyl groups, carboxyl groups, alkoxycarbonyl groups, alkylaminocarbonyl groups, dialkylaminocarbonyl groups, arylcarbonyl groups, aryloxycarbonyl groups, alkylsulfonyl groups, arylsulfonyl groups, cycloalkyl groups, cyano groups, C1-C6 alkylthio groups, arylthio groups, nitro groups, keto groups, acyl groups, boronate or boronyl groups, phosphate or phosphonyl groups, sulfamyl groups, sulfonyl groups, sulfinyl groups, and combinations thereof.

[0041] In further embodiments, substituents or groups of substituents may include halogens, hydroxyls, alkyls, alkenyls, alkynyls, alkoxyls, -NH2, aminos (primary, secondary, or tertiary), nitros, thiols, thioethers, imines, cyanos, amides, phosphonatos, phosphines, carboxyls, thiocarbonyls, sulfonyls, sulfonamides, ketones, aldehydes, esters, acetyls, acetoxys, carbamoyls, oxygen (O); haloalkyls (e.g., trifluoromethyl; aminoacyls and aminoalkyls), monocyclic or condensed or uncondensed polycyclic carbocyclic cycloalkyls (e.g., cyclopropyl, cyclobutyl, cyclopentyl, or cyclohexyl), or monocyclic or condensed or uncondensed polycyclic carbocyclic cycloalkyls. These may include heterocycloalkyls that may be cyclic (e.g., pyrrolidinyl, piperidinyl, piperazinyl, morpholinyl, or thiadinyl), carbocyclic or heterocyclic, monocyclic or condensed or uncondensed polycyclic aryls (e.g., phenyl, naphthyl, pyrrolyl, indolyl, furanyl, thiophenyl, imidazolyl, oxazolyl, isoxazolyl, thiazolyl, triazolyl, tetrazolyl, pyrazolyl, pyridinyl, quinolinyl, isoquinolinyl, acridinyl, pyrazinyl, pyridadinyl, pyrimidinyl, benzimidazolyl, benzothiophenyl, or benzofuranyl), -CO2CH3, -CONH2, -OCH2CONH2; -SO2NH2, -OCHF2, -CF3, -OCF3.

[0042] Modifications or derivatives of the compounds disclosed throughout this specification are considered useful in conjunction with the methods and compositions of this disclosure. Derivatives can be prepared, and the properties of such derivatives can be assayed for their desired properties by any method known to those skilled in the art. In certain embodiments, “derivative” refers to a chemically modified compound that still retains the desired effect of the compound before chemical modification.

[0043] In various embodiments, conventional materials and processing techniques can be employed, and such conventional aspects will not be described in detail herein. For example, the selection of appropriate polysiloxanes, curing conditions, solvents, photosensitizers, pigments, fillers, antistatic agents, flame retardants, defoamers, light stabilizers, and antioxidants can be carried out in conventional ways.

[0044] For the sake of brevity, conventional techniques for fabricating semiconductor devices and integrated circuits (ICs) may or may not be described in detail herein. Furthermore, various tasks and process steps described herein may be incorporated into more comprehensive procedures or processes that have additional steps or functions not described in detail herein. Specifically, because the various steps in the manufacture of semiconductor devices and semiconductor-based ICs are well known, for the sake of brevity, many conventional steps are described only briefly herein, or are omitted entirely without providing details of the well-known processes.

[0045] It should also be understood that material compounds are described with respect to the listed elements, such as SiN or SiGe. These compounds contain different proportions of elements in the compound; for example, SiGe contains Si x Ge (1-x) and similar compounds, where x is less than or equal to 1. In addition, the compound may contain other elements and still function according to the principles of the present invention. Compounds containing additional elements are referred to herein as alloys.

[0046] Next, to give a more specific overview of the technologies relevant to the aspects of this disclosure, electronic packaging components for semiconductors and microelectronic devices generally include a wide range of polymer materials, such as underfills, thermal interface materials (TIMs), adhesives, pastes, and laminates.

[0047] TIM is widely used in electronic equipment packaging to improve heat conduction across the interface between the heat source and the heat sink. Roughness of the interface surface creates non-contact areas, and if air enters these areas, the resulting contact thermal resistance (R) between surfaces increases. c ) increases. Therefore, by filling gaps with TIMs that have a much higher thermal conductivity (k) than air, the contact thermal resistance at interfaces between electronic equipment packaging components can be significantly reduced. Examples of TIMs include various metals (e.g., liquids, solder, or foils), filled polymer matrices (polymer composites, greases, gels, etc.), carbon-based materials, and phase change materials (PCMs). Polymer composite TIMs may include polymer matrices (e.g., PDMS or other polysiloxanes) filled with thermally conductive materials ("fillers"), such as graphite, aluminum, aluminum nitride (AlN), aluminum oxide (alumina), alumina-aluminum, aluminosilicates, boron nitride (BN), liquid gallium, or alloys thereof. TIMs have high k and low contact thermal resistance (R). c ), and other characteristics such as high adaptability may be selected.

[0048] However, TIM is high k, low R c To meet the increasing demands for high frequency and high integration in electronic devices, including high adaptability, challenges remain. Single-chip module TIM degradation can lead to performance loss and increased thermal resistance. Furthermore, as packages transition to multi-chip modules, the greater warping commonly seen in multi-chip modules may further increase the likelihood of TIM degradation.

[0049] Current TIMs are susceptible to cracking or material failure, which can lead to thermal degradation / voids affecting device performance or causing package component failures. Existing TIM matrix polymers are typically based on irreversible PDMS crosslinking chemistry. Therefore, once the TIM hardens, material rework may become impossible. Instead, the damaged or ineffective TIM layer may need to be completely replaced. Existing methods attempting to address this can introduce complexity and additional costs to the TIM assembly process and bonding. For example, existing techniques to improve TIM adhesion may include the use of stiffeners or tie-downs that load the TIM, but these techniques occupy space on the laminate surface. Therefore, such components may violate fundamental rules of device layout.

[0050] Liquid metal materials (e.g., gallium-based liquid metals) have been shown to provide highly thermally conductive films as filler components in polymer composite TIMs. Dispersing droplets in a polymer matrix film before crosslinking can enable the formation of percolating networks that are dynamically captured by crosslinking the polymer network. However, if the polymer network is crosslinked in such a way that the distance between regions of thermally conductive filler or droplets becomes excessively large, the contact thermal resistance of the TIM may increase. If this type of crosslinking is irreversible, as in existing polymer composite TIMs, it may not be possible to improve the distribution and conductivity of the filler after curing.

[0051] Embodiments of this disclosure can overcome these and other challenges by providing a TIM that can be reworked to repair voids, cracks, and other defects within the TIM when heated. In some embodiments, the disclosed TIM can be used without requiring significant changes to typical packaging processes or components. For example, the TIM can be contained in a capped package (e.g., as TIM1 / TIM2) or a direct-attach case (e.g., as TIM1.5). Additionally, reworkable TIMs can improve package yield and lifespan and facilitate scaling of multi-chip modules.

[0052] Reworkable TIMs may include polymer networks (matrices) having relaxation pathways (e.g., reversible crosslinking chemical reactions, dynamic covalent bonds, supramolecular interactions, etc.) that can be used to reversibly "soften" the polymer at temperatures above a threshold temperature. Reworkable TIMs may be composite films of these polymer networks and thermally conductive fillers such as metal particles or liquid metal.

[0053] In some embodiments, the relaxation pathway of the TIM polysiloxane chain can be generated by introducing persistent anionic chain ends. For example, a reworkable TIM may include a hydroxy-terminated polysiloxane blended with a latent organocatalyst that, when activated by thermal stimulation, can cleave silicon-oxygen bonds in the polymer chain.

[0054] In further embodiments, relaxation pathways can be generated by incorporating thermoreversible cyclic adducts into the polysiloxane chain network. For example, hydride-crosslinked polysiloxane components (e.g., skeleton, branched chains, crosslinking agents, etc.) can be replaced with polysiloxane components functionalized with diene / dienophile groups, such as a single-component cyclopentadiene system or a furan / maleimide derivative. In another example, the polysiloxane includes siloxane surface functional groups that can be reversibly dimerized in response to thermal stimuli to improve surface adhesion. In yet another example, a crosslinking network formed by a Diels-Alder reaction between bismaleimide and a trifunctional furan crosslinking agent can be blended with the polysiloxane.

[0055] Next, referring to the drawings, where similar numbers in the drawings represent identical or similar elements, Figure 1A is a flowchart of process 100 for preparing an electronic device with a reworkable thermal interface material (TIM) according to several embodiments. A reworkable TIM can be provided, as shown in step 110. As described above, the reworkable TIM can be a polymer composite TIM. The polymer matrix of the reworkable TIM may include a polysiloxane such as polydimethylsiloxane (PDMS) or another polysiloxane (e.g., poly(dimethylsiloxane-co-diphenylsiloxane)).

[0056] In some embodiments, the polysiloxane may be functionalized with a thermoreversible cyclic adduct. Herein, “cyclic adduct” and “dimer” are used interchangeably to refer to the product of a Diels-Alder cyclic adduct / dimerization reaction. For example, a polysiloxane chain having Diels-Alder terminal groups can be cured to form a polysiloxane skeleton linked by a thermoreversible cyclic adduct. In another example, the polysiloxane chain may be crosslinked and / or branched by side chains and / or terminal Diels-Alder groups. In some embodiments, the polymer network may include thermoreversible cyclic adducts in both the skeleton and the crosslinking / branching.

[0057] In further embodiments, the polymer matrix can be formed by blending polysiloxane with an immiscible crosslinking network comprising thermoreversible cyclic adducts, or by surface-functionalizing polysiloxane with thermoreversible cyclic adducts. In these embodiments, the polysiloxane may be a conventional polysiloxane (e.g., unsubstituted PDMS) or the reversibly dimerized polysiloxane network described above. Surface functionalization of the polysiloxane may include reversibly dimerized siloxane small molecules. The surface functional groups can facilitate adhesion to the surface of the device component. The immiscible crosslinking network can provide covalent crosslinks (e.g., cyclic adducts) and physical crosslinks (e.g., crystalline domains, aggregates, etc.), both of which can be reversibly altered in response to thermal stimuli.

[0058] In additional embodiments, the reworkable TIM may include a polysiloxane blended with a potential organocatalyst that, when activated by thermal stimulation, can cleave silicon-oxygen bonds in the polymer chain. This will be described in more detail with reference to Figures 10A and 10B.

[0059] By varying the polysiloxane chain length, crosslinking / branching, fillers, number / type of reversible cyclic adduct units, and catalyst generation concentration, reworkable TIMs with different viscosities, curing temperatures, thermal conductivity, and other properties can be provided. Reworkable TIMs may also contain thermally conductive filler materials, such as graphite, aluminum, aluminum nitride (AlN), alumina, alumina-aluminum, boron nitride (BN), and liquid metals (e.g., gallium-indium, gallium-indium-tin) within the polysiloxane matrix. In some embodiments, the TIM contains at least 90% by weight of thermally conductive filler, but this amount is variable.

[0060] The semiconductor package can be assembled using reworkable TIM, as shown in step 120. Package assembly may include applying and curing layers of TIM at the interface between the heat sink and the heat source (see, for example, Figure 2). Any suitable technique for assembling a semiconductor package using polysiloxane-based TIM can be used. Examples of these techniques are known in the art and are therefore not described in detail herein. In some embodiments, package assembly may include applying thermal stimulation to the reworkable TIM after curing. However, as shown in Figure 1B, thermal stimulation may be applied after the device is assembled.

[0061] Figure 1B is a flowchart of process 101 for reworking a cured TIM layer according to several embodiments. A device for mounting the cured TIM layer can be provided, as shown in process 130. In some embodiments, the device is a semiconductor package for mounting at least one reworkable TIM layer produced in process 100 (Figure 1A). In further embodiments, the device is a computing device comprising at least one semiconductor package for mounting the reworkable TIM. In some embodiments, a device is provided in case it is found to have degraded performance after a period of use (e.g., due to crack formation or reduced adhesion of the TIM). The device may also be provided in response to the detection of at least one faulty chip during testing.

[0062] To rework the TIM, thermal stimulation can be applied to the provided device. This is shown in step 140. As used herein, “thermal stimulation” can mean heat applied at a threshold temperature or temperature range sufficient to rework the TIM polymer (e.g., between approximately 60 and 150°C), or higher but below a temperature that would cause damage to the TIM or other device components. For example, there may be a minimum temperature for reworking the polymer network and a maximum temperature determined based on the thermal stability of the TIM and other device components. Thermal stimulation can be applied for approximately 10 to 30 minutes, but the time may be variable (e.g., approximately 5 to 10 minutes, 10 to 15 minutes, 15 to 20 minutes, 30 to 60 minutes, 1 to 12 hours, etc.).

[0063] Next, the thermal stimulus can be removed and the TIM can be cooled to below a threshold temperature (e.g., ambient temperature or any other temperature suitable for device operation). This is shown in step 150. This allows the reworked TIM polymer to be re-solidified by Diels-Alder cyclic addition. As a result of the rework, cracks in the TIM may be repaired and adhesion to the device surface may be improved. Additionally, the rework may correct undesirable crosslinking of the polysiloxane.

[0064] Figure 2 is a block diagram showing a portion of an electronic device module 200 for mounting a reworkable TIM according to several embodiments. Figure 2 provides a simplified diagram of a semiconductor package that can mount a reworkable TIM, as described above with respect to Figures 1A and 1B. The module 200 may include a package lid 203 (e.g., an integrated heat spreader: IHS) above the semiconductor (silicon chip 206) mounted on a substrate 209. A heat sink 213 may be mounted on the lid 203.

[0065] The capped package of module 200 includes TIM1 / TIM2 layers 216A and 216B (collectively referred to as "TIM layer 216"). TIM1 216A is located at the interface between the chip 206 and the package lid 203, and TIM2 216B is located at the interface between the lid 203 and the heatsink 213. In other embodiments, the number / configuration of TIM layers 216 may be modified. For example, TIMs such as TIM layer 216 may be included in packaging based on direct bonded heterogeneous integration (DBHi), in which the processor chip is directly bonded to the silicon bridge using copper pillars. Although not shown in Figure 2, other device / packaging components, such as solder balls and underfill between the chip 206 and the substrate 209, additional semiconductor packages mounted on the substrate 209, or any other suitable components known in the art may be included in module 200.

[0066] Figure 3A is a chemical structure diagram showing an example of a polysiloxane (PDMS) 300 having a substituted cyclic adduct unit according to several embodiments of the present disclosure. Polysiloxane 300 can be used in reworkable TIMs (e.g., TIM layer 216). In the structure of polymer 300, n and m each represent an integer greater than 1 or 1, and the asterisked bond represents a substituent that can be modified to adjust the properties of the polymer. The substituents can be independently selected and, in some embodiments, are alkyl groups (e.g., methyl, ethyl, propyl, butyl, etc.). However, in other embodiments, at least one asterisked bond can be bonded to a hydrogen atom (e.g., if the cyclopentadiene group is not substituted). In further embodiments, other substituents (e.g., from the examples of substituents described above) may be selected depending on the desired properties.

[0067] Polysiloxane 300 can be formed by dimerization of substituted pentadiene terminal groups on a PDMS chain. Cyclopentadiene terminal groups are dimerized by a Diels-Alder reaction or a reversible cycloaddition reaction between a conjugated diene and a substituted alkene ("dienophile"). By changing the diene or dienophile, the effect of temperature on the reaction equilibrium can be adjusted. For example, dienophiles with stronger electron-withdrawing groups may react at lower temperatures. Thus, by adding electron-withdrawing or electron-donating groups to the cyclopentadiene unit (e.g., the asterisked bond), the temperature at which crosslinking / rework can occur can be adjusted in some embodiments. In further embodiments, the threshold temperature for inverse dimerization can be adjusted by changing the steric effect of the substituent on the cyclopentadiene species.

[0068] Figure 3B is a chemical reaction diagram showing a polysiloxane rework process 301 according to several embodiments. A cured TIM containing a polysiloxane, such as that shown in Figure 3A, may contain dimerized end groups on the same polysiloxane chain 303, as shown in Figure 3B. Although only one "self-dimerized" PDMS molecule 303 is shown in Figure 3B, the cured TIM polymer matrix may contain PDMS molecules with varying chain lengths and configurations. The presence of self-dimerized polysiloxane chains may reduce thermal conductivity by inhibiting linear formation of the polymer network. Thermal stimulation can be applied to induce inverse dimerization of cyclopentadiene dimer units, as shown in step 310. As a result of removing the thermal stimulation, cyclic adducts with cyclopentadiene end groups of other PDMS chains in the polymer network may be formed, as shown in step 320.

[0069] Figure 4 is a chemical reaction diagram showing Experimental Example 400 of a thermal stability test using reworkable polysiloxane 403 according to several embodiments. Polysiloxane (PDMS) 403 contains m chains of n siloxane units linked by DA (Diels-Alder) adducts, where m and n are integers greater than 1 or 1. In this example, m was in the range of approximately 3 to 5, and the molecular weight of the polysiloxane was in the range of approximately 180 to 13,000 g / mol. In step 410, polymer 403 was cured in a nitrogen (N2) purged polyimide bake oven under weak vacuum over a temperature range of 65 to 245°C. The temperature was increased from 65°C at a rate of 5°C / min and then held at 245°C for approximately 10 minutes. As a result of curing over this temperature range, p trimers (where p is an integer greater than 1 or 1) were produced from the cyclopentadiene terminal groups of at least two molecules of polysiloxane 403. In step 420, the trimerized polymer 406 was subjected to a thermal stimulus of approximately 90°C for approximately 30 minutes. At this temperature, DA dimerization was reversible, but trimerization was not.

[0070] Figure 5A is a chemical structure diagram showing siloxane Diels-Alder dimers according to several embodiments. Species such as compounds 510-540 can be used as surface functional groups for polysiloxane TIMs. Dimers 510-540 shown in Figure 5A include Diels-Alder adducts that can be “dedimerized” in response to thermal stimulation above a threshold temperature (e.g., about 90-120°C). Therefore, if there is a decrease in adhesion on the TIM surface, the application of thermal stimulation to the device can be used to improve surface adhesion during rework / cooling.

[0071] Figure 5B is a set of chemical structure diagrams showing examples of reworkable polysiloxanes 550–580 having thermoreversible cyclic adduct units according to several embodiments. These polysiloxanes 550–580 contain a polysiloxane (PDMS) skeleton in which polysiloxane chains are linked by thermoreversible cyclic adducts. This skeleton can be formed by curing a polysiloxane having cyclopentadiene terminal groups or other Diels-Alder terminal groups (not shown in Figure 5B) using any curing conditions suitable for polysiloxanes. Polysiloxanes 550–580 and thermally conductive fillers can be used to form a reworkable TIM layer, as described in more detail above with respect to Figures 1A–2. In the figures, n, l, and m are integers greater than 1 or each other. For example, n can represent approximately 34 dimethylsiloxane repeating units, l can represent approximately 11 methylene(-CH2-) groups, and m can represent a PDMS chain linked by approximately 1 to 100 cyclic adduct units. Although dimethylsiloxane repeating units are shown, in some embodiments, at least some of the methyl groups may be replaced with other alkyl groups such as phenyl. For example, poly(dimethylsiloxane-co-diphenylsiloxane) can be used as a substitute for PDMS.

[0072] Figure 6 is a chemical structure diagram showing a group of polysiloxanes 600 having furan and maleimide groups according to several embodiments. The illustrated compounds include bismaleimide PDMS (n=approximately 7-30), bisfuran PDMS (n=approximately 7-30), and side-chain furan PDMS (n=approximately 150), which can react with each other to form furan / maleimide dimer units by Diels-Alder cycloaddition. In some embodiments, mixtures of PDMS compounds 600 can be cured in the presence of radical inhibitors (e.g., N,N'-diphenylthiourea, butylated hydroxytoluene, catechol, 4-tert-butylcatechol, 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO), 1,4-naphthoquinone, etc.) to prevent irreversible crosslinking by radical mechanisms. For example, a mixture of PDMS compounds 600 and radical inhibitors can be cured at approximately 75°C (e.g., for approximately 20 hours). The ratio of bismaleimide-PDMS:bisfuran-PDMS:side-chain-furan-PDMS in the mixture can be 1:1:1 or 1:0.5:0.5, and this ratio can be adjusted, for example, based on the desired thermal properties and viscosity of the resulting TIM.

[0073] This reaction can generate a polymer network (not shown in Figure 6) containing a polysiloxane chain skeleton and / or branching linked by thermoreversible furan / maleimide cycloadducts, as well as thermoreversible furan / maleimide cycloadduct crosslinks formed by dimerization of the side chains. The cycloadducts in the cured TIM can be “dedimerized” by a reverse Diels-Alder reaction in the presence of thermal stimulation (e.g., about 100–120°C for about 10–30 minutes).

[0074] Figure 7A shows the proton nuclear magnetic resonance of the first trifunctional furan crosslinking agent 703 ("trifunctional crosslinking agent 703"). 1The "1H NMR" or "NMR" spectrum 700 and the corresponding chemical structure diagram are shown. The NMR spectrum 700 was experimentally obtained from a deuterated chloroform (CDCl3) solution of the trifunctional crosslinker 703. The positions of the hydrogen atoms on the trifunctional crosslinker 703 and their corresponding spectral peaks in the NMR spectrum 700 are labeled a - f in FIG. 7A.

[0075] A sample of the trifunctional furan crosslinker 703 from which the NMR spectrum 700 was obtained was synthesized as follows:

[0076] A mixture of 5 g of trimesic acid, 10 mL of thionyl chloride (SOCl2), and a catalytic amount of dimethylformamide (DMF) was heated under reflux for about 3 hours. The remaining SOCl2 was evaporated under reduced pressure to obtain the trimesoyl chloride (1,3 - benzenetricarboxylic acid chloride) product. Then, the trimesoyl chloride and about 10 equivalents (eq.) of furfurylamine were dissolved in DMF. Pyridine was added dropwise to this solution at about 0 °C and stirred for about 18 hours. Then, the reaction mixture was diluted with an excess of dichloromethane (DCM) and extracted with about 1 molar (1M) hydrochloric acid (HCl). The extracted organic phase was dried over magnesium sulfate (MgSO4) and purified by column chromatography (hexane:ethyl acetate = 1:1) to obtain the trifunctional crosslinker 703.

[0077] FIG. 7B shows the 1H NMR spectrum 706 of the second trifunctional furan crosslinker 709 ("trifunctional crosslinker 709") 1 and the corresponding chemical structure diagram. The NMR spectrum 706 was experimentally obtained using a solution of the trifunctional crosslinker 709 in CDCl3. The positions of the hydrogen atoms on the trifunctional crosslinker 709 and their corresponding spectral peaks in the NMR spectrum 706 are labeled a - e in FIG. 7B.

[0078] A sample of the trifunctional furan crosslinker 709 from which the NMR spectrum 706 was obtained was synthesized as follows:

[0079] A mixture of 5 g of trimesic acid, 10 mL of SOCl2, and a catalytic amount of DMF was heated under reflux for approximately 3 hours. The remaining SOCl2 was evaporated under reduced pressure to obtain the trimesoyl chloride product. The trimesoyl chloride and approximately 10 equivalents of furfuryl alcohol were then dissolved in DMF. Pyridine was added dropwise to the solution at 0°C and stirred for approximately 18 hours. The reaction mixture was then diluted with excess DCM and extracted with approximately 1 M HCl. The extracted organic phase was dried over MgSO4 and purified by column chromatography (hexane:ethyl acetate = approximately 1:1) to obtain the trifunctional furan crosslinking agent 709.

[0080] Figure 8A is a chemical reaction diagram showing the Diels-Alder reaction 800 between the second trifunctional furan crosslinking agent 709 and N-methylmaleimide in several embodiments. In other embodiments, reaction 800 can be carried out using the first trifunctional furan crosslinking agent 703. Reaction 800 forms product 803, which contains a thermoreversible furan / maleimide cyclic adduct. Figure 8B shows the experimental example of reaction 800 shown in Figure 8A, obtained at three time intervals while monitoring. 1 This is a set of 1H NMR spectra 806A to 806C (collectively referred to as 806). In Figures 8A and 8B, the hydrogen atoms of the starting material are labeled with letters a to g, and the hydrogen atoms of product 803 are labeled with numbers 1 to 4.

[0081] The first NMR spectrum, 806A, was obtained from the starting mixture of the reactants of the Diels-Alder reaction 800 (trifunctional furan crosslinking agent 709 and N-methylmaleimide) in deuterated dimethyl sulfoxide (DMSO). The mixture was heated to approximately 80°C, and after about 3 hours at this temperature, the next NMR spectrum, 806B, was obtained from this mixture. The third NMR spectrum, 806C, was obtained from the mixture after about 48 hours at approximately 80°C. As can be seen from the set of NMR spectra 806, the reaction 800 between the second trifunctional crosslinking agent 709 and N-methylmaleimide proceeds slowly, which may be favorable for the formation of a crosslinking network (see, for example, Figure 9A).

[0082] Figure 9A is a chemical reaction diagram showing the formation of a thermoreversible crosslinked network 900 according to several embodiments. The trifunctional furan crosslinker 903 ("trifunctional crosslinker 903") can be blended with a bismaleimide compound ("bismaleimide") 903. In some embodiments, the trifunctional crosslinker 903 represents one or both of the crosslinkers 703 / 709 shown in Figures 7A and 7B. In the structure of the trifunctional crosslinker 903 shown in Figure 9A, X can represent O (ester moiety) or NH (amide moiety). The mixture of bismaleimide 906 and the trifunctional crosslinker 903 can be cured at approximately 60°C, resulting in a crosslinked network 909 formed by a Diels-Alder reaction between the trifunctional crosslinker 903 and multiple equivalents of bismaleimide 906 (represented by wavy bonding to the imide nitrogen atom). Figure 9A shows only one crosslinking unit in the network 909. However, as will be understood by those skilled in the art, the crosslinking network 909 comprises multiple units of bismaleimide species 906 linked by a trifunctional crosslinking agent 903. The wavy bonds to the imide nitrogen atoms represent covalent bonds to carbon atoms, as shown in the structure of bismaleimide 906. When the temperature of the crosslinking network 909 rises to (or beyond) a threshold temperature (e.g., about 100°C), inverse dimerization of the cyclic adduct crosslinking may occur. When the temperature decreases, the network 909 can dimerize again.

[0083] In some embodiments, a mixture of bismaleimide 906 and a trifunctional furan crosslinking agent 903 can be blended with polysiloxane, for example, in step 110 of process 100 (Figure 1A). In some embodiments, the crosslinking agents 903 and 906 do not mix in the polysiloxane. By curing the mixture, a polymer network containing a crosslinking network 909 having both physical and covalent crosslinks, and polysiloxane can be produced. This polymer network can be used to provide a reworkable TIM, which may also include a thermally conductive filler. Experimental examples of this process were carried out using PDMS and crosslinking agents 903 and 906. In these examples, the crosslinking agents 903 and 906 did not mix with PDMS and caused phase separation. Both the physical and covalent crosslinks in the crosslinking network 909 / PDMS blend can be broken by thermal stimulation, for example, in step 140 of process 101 (Figure 1B), allowing the TIM to be reworked / repaired. In some embodiments, rework may be used to improve the distribution of thermally conductive filler throughout the TIM.

[0084] Figure 9B is graph 910, showing experimental results obtained by dynamic mechanical analysis (DMA) of the crosslinked network 909 (shown in Figure 9A, where X=O). The DMA results measure the change in the storage modulus of the crosslinked network 909 when thermal stimulation is applied. A film of the crosslinked network 909 (X=O) was formed by curing a mixture of the trifunctional furan crosslinking agent 903 (709) and bismaleimide 906 at 60°C. The resulting change in the storage modulus of the crosslinked network 909 was monitored by repeating cycles between 60°C and 120°C (5°C / min). As shown in graph 910, the storage modulus of the crosslinked network 909 can be reversibly reduced in response to the application of thermal stimulation.

[0085] Figure 10A is a chemical reaction diagram showing a rework process 1000 of a TIM by thermal activation of a thermally activated potential catalyst ("organic catalyst generator" or "catalyst generator") according to several embodiments. The organic catalyst generator 1003 (e.g., ≤1 wt%) can be blended with hydroxy-terminated PDMS 1006. In some embodiments, a mixture of hydroxy-terminated PDMS 1006 / catalyst generator 1003 can be combined with a thermally conductive filler to form a polymer composite TIM. For example, the TIM may contain a hydroxy-terminated PDMS 1006 / catalyst generator 1003 matrix with an alumina-aluminum filler. However, various thermally conductive fillers can be used, such as graphite, aluminum, aluminosilicate, aluminum nitride, aluminum oxide, boron nitride (BN), liquid gallium, or alloys thereof. In other embodiments, a mixture of hydroxy-terminated PDMS 1006 / catalyst generator 1003 can be combined with conventional TIMs such as Dow Corning® TC-3040 thermal conductive gel (manufactured by Dow, Inc.), thereby enabling TIM rework. In some embodiments, catalyst generator 1003 is a salt that forms DBU (1,8-diazabicyclo[5.4.0]undeca-7-ene) when heated to a trigger temperature.

[0086] Figure 10B is a set of chemical reaction diagrams 1023–1029 showing examples of DBU-forming salts that can be used as catalyst generators according to several embodiments. As shown in Figure 10B, the exemplary catalyst generators 1003 in Figures 1023–1029 can form DBU at trigger temperatures of approximately 160°C, 180°C, and 200°C, respectively. In some embodiments, the DBU generator in Figure 1026 is used as catalyst generator 1003 in process 1000 (Figure 10A). However, other DBU generators (e.g., those shown in Figures 1023 and 1029) can also be used. In some embodiments, potential catalysts other than DBU can be used. For example, compounds that can be used as catalyst generator 1003 may include salts that produce catalysts, such as triazabicyclodecene (1,5,7-triazabicyclo[4.4.0]deca-5-ene, or TBD), pyridine, tetra-n-butylammonium fluoride (TBAF), etc.

[0087] Referring again to Figure 10A, any suitable curing conditions can be used to cure the PDMS in the PDMS 1006 / catalyst generator 1003 mixture at a temperature lower than the trigger temperature of the catalyst generator 1003. This is shown in step 1010. For example, PDMS 1006 can be cured at approximately 120°C.

[0088] The cured TIM can be reworked by applying a thermal stimulus to activate the catalyst generator 1003, as shown in step 1020. For example, if the catalyst generator 1003 is the DBU salt shown in Figure 1026 of Figure 10B, the thermal stimulus may have a threshold temperature of at least 180°C. In response to the thermal stimulus, the activated catalyst ("catalyst" in Figure 10A) can form an anionic end on the hydroxy-terminated PDMS 1006, cleaving the silicon-oxygen bond. This reaction can continue until the equilibrium reaction is stopped (in step 1021).

[0089] The descriptions of the various embodiments of this disclosure are presented for illustrative purposes only and are not intended to be exhaustive or limitful to the embodiments described. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the embodiments described. The terms used herein have been selected to best describe the principles, practical applications, or technical improvements to the technologies prevalent in the market, or to enable those skilled in the art to understand the embodiments described herein.

Claims

1. A thermally reworkable polymer comprising at least one polysiloxane chain having a thermoreversible cyclic addition functional group. Thermal interface material (TIM) including [this].

2. The thermally reworkable polymer comprises a backbone of at least one polysiloxane chain linked by the thermally reversible cyclic addition functional group, according to claim 1.

3. The aforementioned thermally reworkable polymer has the following structure: 【Chemistry 1】 It has, Here, n and m are integers greater than 1 or 1; R is an alkyl substituent; and The TIM according to claim 2, wherein each bond indicated by an asterisk is a bond to a hydrogen atom or an alkyl group.

4. The TIM according to claim 3, wherein the alkyl group is methyl or ethyl.

5. The aforementioned thermally reworkable polymer has the following structure: 【Chemistry 2】 It has, The TIM according to claim 2, wherein n, m, and l are integers greater than 1 or 1.

6. The aforementioned thermally reworkable polymer has the following structure: 【Transformation 3】 The TIM according to claim 2, wherein n, m, and l are integers greater than 1.

7. The aforementioned thermally reworkable polymer has the following structure: 【Chemistry 4】 It has, The TIM according to claim 2, where n is 1 or an integer greater than 1.

8. The aforementioned thermally reworkable polymer has the following structure: 【Transformation 5】 It has, The TIM according to claim 2, where n is 1 or an integer greater than 1.

9. The TIM according to claim 1, wherein the thermoreversible cyclic addition functional group is a surface functional group on the at least one polysiloxane chain.

10. The TIM according to claim 1, wherein the thermally reversible cyclic addition functional group is a side-chain functional group on the at least one polysiloxane chain.

11. The TIM according to claim 1, further comprising a thermally conductive filler blended with the thermally reworkable polymer.

12. The TIM according to claim 11, wherein the thermally conductive filler is a liquid metal.

13. Polysiloxanes; and A crosslinked network blended with the polysiloxane, the crosslinked network comprising a thermoreversible cyclic addition functional group, A thermally reworkable polymer network including Thermal interface material (TIM) including [this].

14. The aforementioned cross-linking network has the following structure: 【Transformation 6】 It has, The TIM according to claim 13, where X represents O or NH, and the wavy bond is to an alkyl carbon atom.

15. The TIM according to claim 13, further comprising a thermally conductive filler.

16. The TIM according to claim 15, wherein the thermally conductive filler is selected from the group consisting of graphite, aluminum, aluminum nitride, aluminum oxide, boron nitride, and gallium-based liquid metals.

17. The TIM according to claim 13, wherein the polysiloxane is selected from the group consisting of polydimethylsiloxane and poly(dimethylsiloxane-co-diphenylsiloxane).

18. The invention provides a thermal interface material (TIM) comprising a thermally reworkable polymer network, wherein the polymer network is At least one polysiloxane chain; and Containing a thermoreversible cyclic addition functional group, method.

19. The method according to claim 18, wherein the thermally reworkable polymer network comprises the at least one polysiloxane chain and the thermally reversible cyclic adduct skeleton.

20. The method according to claim 18, wherein the thermally reworkable polymer network comprises an immiscible blend of a crosslinked network comprising the at least one polysiloxane chain and the thermally reversible cyclic adduct.

21. The method according to claim 18, wherein the TIM is reworkable at a temperature between 60 and 150°C.

22. A thermal interface material (TIM) comprising a thermally reworkable polymer network, wherein the thermally reworkable polymer network is At least one polysiloxane chain; and Containing a thermoreversible cyclic addition functional group, Semiconductor package.

23. The semiconductor package according to claim 22, wherein the TIM is reworkable at a temperature between 60 and 150°C.

24. The semiconductor package according to claim 22, wherein the TIM further comprises a thermally conductive filler.

25. A semiconductor package comprising at least one on which a thermal interface material (TIM) is mounted, wherein the TIM is At least one polysiloxane chain; and Thermoreversible cyclic addition functional groups Including a thermally reworkable polymer network, Computing device.

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