Porous composite materials and methods of producing thereof

Abstract

An electronic system including one or more (semi)conductive entities attached to a substrate, and a porous dielectric composite material, wherein the composite material includes: a polymer and a non-conductive fdler, wherein the composite material is nano / micro porous, wherein the pores are essentially homogenously distributed and, wherein a thermal stress between the composite material and the one or more (semi)conductive entities is at least about 1.5 -fold lower compared to a non-porous analog.

Description

[0001] POROUS COMPOSITE MATERIALS AND METHODS OF PRODUCING

[0002] THEREOF

[0003] TECHNICAL FIELD

[0004] The present disclosure relates generally to electronic devices. More particularly, the present disclosure relates to porous dielectric composite materials for use in electronic components.

[0005] BACKGROUND

[0006] Electronic devices undergo thermal cycling of heating and cooling during their operation. This process leads to repeated expansion and contraction of the components, which is one of the primary reasons for electronics failure. The stress and strain caused by the thermal expansion / contraction affect the device's specifications and performance of almost all components. When thermal fatigue occurs, multiple systems within the devices can be affected, resulting in warpage, solder weakness, breaking or cracking, and ultimately, product failure. As electronics are a part of everything today, the strain caused by thermal cycling affects components in devices across industries such as automotive, aerospace and defense, biomedical, manufacturing, and consumer goods.

[0007] Three factors affect the thermal stress of an electronic assembly: the extent of temperature change, the difference between the coefficients of thermal expansion (CTE) of the materials that come into contact with each other, and their moduli. Every material has a unique CTE, and a mismatch between the CTEs of materials is a major cause of fatigue. Since different materials are required for an electronic assembly, they will inherently have different CTEs, for example, a semiconductive material and an organic polymer will have very distinct CTEs. In addition, every material has a unique modulus that reflects its elasticity, which is the ratio of stress to strain. This measures how resistant the object is to being deformed elastically. A high modulus, which is often a characteristic of the essential semiconductive material, for example, will lead to higher thermal stress. Composite materials offer a reduced CTE compared to polymers alone, however, that is not sufficient by itself to reduce thermal stress. Additionally, the modulus of the composite material is too high and should be modulated.

[0008] There is a need to modify or compensate for these characteristics in order to reduce thermal stress and achieve stable, high-performing, and reliable electronic devices that can withstand ongoing thermal cycling with minimal impact on product specifications.

[0009] SUMMARY

[0010] This disclosure is directed, in accordance with some embodiments, to an electronic system that is characterized by low thermal stress between a dielectric composite material and one or more (semi)conductive entities attached to a substrate.

[0011] Advantageously, the composite material disclosed herein, in accordance with some embodiments, is configured to be porous and therefore characterized by a low modulus and a low thermal expansion coefficient compared to its non-porous counterpart. As a result, and in accordance with some embodiments, the electronic system including the said porous composite material is characterized by thermal stress that is lower by at least about 1.5-fold compared to a system incorporating a non-porous analog of the composite material.

[0012] The disclosure further provides, in accordance with some embodiments a method for producing porous composite material with homogenously distributed pores and filler.

[0013] There is provided herein, according to some embodiments, an electronic system including one or more (semi)conductive entities attached to a substrate, and a porous dielectric composite material, wherein the composite material is located over the one or more (semi)conductive entities and the substrate, wherein the composite material includes: a polymer and a non-conductive filler, wherein the composite material is nano / micro porous, wherein the pores are essentially homogenously distributed and, wherein a thermal stress between the composite material and the one or more (semi)conductive entities is at least about 1.5 -fold lower compared to a non-porous analog. According to some embodiments, the thermal stress between the composite material and the one or more (semi)conductive entities is at least about 2-fold lower compared to a non- porous analog.

[0014] According to some embodiments, the composite material is characterized by a thermal expansion coefficient that is lower compared to a non-porous analog by at least about 10%.

[0015] According to some embodiments, the composite material is characterized by a biaxial modulus that is lower compared to a non-porous analog by at least about 30%.

[0016] According to some embodiments, the composite material is characterized by a density that is lower compared to a non-porous analog by at least about 15%.

[0017] According to some embodiments, the composite material is characterized by a dielectric constant that is lower compared to a non-porous analog by at least about 30%.

[0018] According to some embodiments, the pores are heterogenous ranging in size from about 50 nm to 5 pm.

[0019] According to some embodiments, the pores are opened and / or closed pores.

[0020] According to some embodiments, the pores include gas, liquid, or both.

[0021] According to some embodiments, the gas includes ambient air.

[0022] According to some embodiments, the filler is selected from Nomex, Kevlar, paraaramid, ortho-aramid, polyamide, SiCh, SiCh-Li / Ba-Al, SiO2 / B2O3 / Zn / Sr / Li, Zr-Si, Si-C, Si- N, ZrO2, ZnO, TiCh, B-N, AI2O3, ZrWhC . doped versions thereof, or any combination thereof.

[0023] According to some embodiments, the filler includes Aramid / Kevlar, SiCh, or ZrWhOs.

[0024] According to some embodiments, a shape of the filler is selected from a sphere, platelet, rod, fiber, an irregular shape, or any combination thereof.

[0025] According to some embodiments, the composite includes the filler and the polymer in a ratio of about 80 / 20 to 30 / 70 (v / v), respectively.

[0026] According to some embodiments, the filler is homogeneously distributed in the composite material. According to some embodiments, the polymer includes epoxy, polyimide, polyamide, polyurethane, bismaleimide, polyacrylate, polyethylene terephthalate, polyethylene naphthalates, polylactic acid, polyester, polypropylene, polyolefin, polyphenol, silicon resin, benzocyclobutene (BCB) polymer, derivatives thereof, or any combination thereof.

[0027] According to some embodiments, the composite material is used for an application selected from the groups consisting of coating, spacing, packaging, sealing, additive manufacturing, ink-jetting, associating, or encapsulating one or more (semi)conductive entities.

[0028] According to some embodiments, the coating has a thickness of about 5-100 pm.

[0029] There is provided herein, in accordance with some embodiments, a method of producing an electronic system, the method including: providing a substrate comprising one or more (semi)conductive entities; treating the substrate by exposing it to a first dielectric composite solution including a first solvent, a non-conductive filler, and a polymer or a prepolymer, wherein the first solvent is capable of solubilizing the polymer or the pre-polymer; exposing the treated substrate to a second solvent, wherein the second solvent is essentially incapable of solubilizing the polymer, and wherein the second solvent is miscible with the first solvent; and evaporating the solvent mixture to form essentially homogenously distributed pores in an essentially dried composite material, thereby obtaining an electronic system including the porous composite material located over the substrate and the one or more (semi)conductive entities.

[0030] According to some embodiments, the filler is insoluble in the first and second solvents.

[0031] According to some embodiments, a surfactant is further added to the filler.

[0032] According to some embodiments, the polymer and / or pre-polymer is solid or semisolid.

[0033] According to some embodiments, the pre-polymer includes a monomer, oligomer, initiator, catalyst, cross-linker, polymer, or any combination thereof.

[0034] According to some embodiments, the treating of the substrate by exposing it to a first dielectric composite solution and / or the exposing of the treated substrate to the second solvent, is performed by a technique selected from the group consisting of spin-coating, dip-coating, spray-coating, layer-by-layer deposition, vapor deposition, and any combination thereof.

[0035] According to some embodiments, the essentially dried composite material is characterized by a viscosity of more than about 100,000 cP while having a shear rate of less than about 1 Hz.

[0036] According to some embodiments, the essentially dried composite material is further cured.

[0037] Certain embodiments of the present disclosure may include some, all, or none of the above advantages. One or more technical advantages may be readily apparent to those skilled in the art from the figures, descriptions and claims included herein. Moreover, while specific advantages have been enumerated above, various embodiments may include all, some or none of the enumerated advantages.

[0038] In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the figures and by study of the following detailed descriptions.

[0039] BRIEF DESCRIPTION OF THE FIGURES

[0040] The invention will now be described in relation to certain examples and embodiments with reference to the following illustrative figures.

[0041] FIG. la shows an exemplary cross-sectional side view obtained from a high-resolution scanning electron microscope (HR-SEM) using a focused ion beam (FIB) for a porous composite material containing silica nanoparticles (0.5 pm) and bismaleimide polymer in a ratio of 3 / 2 (w / w), in accordance with some embodiments.

[0042] FIG. lb shows a magnification (x5) of the system exemplified in FIG. la, in accordance with some embodiments.

[0043] FIG. 1c shows an exemplary cross-sectional side view obtained from a high-resolution scanning electron microscope (HR-SEM) using a focused ion beam (FIB) for a porous material that contains bismaleimide polymer, in accordance with some embodiments. FIG. Id shows a magnification (x5) of the system exemplified in FIG. 1c, in accordance with some embodiments.

[0044] FIG. 2 shows a flowchart of a method for producing an electronic system, in accordance with some embodiments.

[0045] FIG. 3 is a schematic illustration exemplary of a method for producing an electronic system including a porous composite material located over a substrate and one or more (semi)conductive entities, in accordance with some embodiments.

[0046] FIG. 4 is a comparative schematic illustration exemplary of FIG. 3 of a method for producing an electronic system including a non-porous composite material located over a substrate and one or more (semi)conductive entities, in accordance with some embodiments.

[0047] FIG. 5a shows an exemplary cross-sectional side view obtained from a high-resolution scanning electron microscope (HR-SEM) using a focused ion beam (FIB) for a porous composite material containing silica nanoparticles (0.5 pm) and bismaleimide polymer in a ratio of 3 / 2 (w / w), in accordance with some embodiments.

[0048] FIG. 5b is a comparative example to FIG. 5a shows a cross-sectional side view obtained from a high-resolution scanning electron microscope (HR-SEM) using a focused ion beam (FIB) for a non-porous composite material containing silica nanoparticles (0.5 pm) and bismaleimide polymer in a ratio of 3 / 2 (w / w), in accordance with some embodiments.

[0049] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0050] In the following description, various aspects of the disclosure will be described. For the purpose of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the different aspects of the disclosure. However, it will also be apparent to one skilled in the art that the disclosure may be practiced without specific details being presented herein. Furthermore, well-known features may be omitted or simplified in order not to obscure the disclosure.

[0051] Prior to setting forth the present subject matter in detail, it may be helpful to provide definitions of certain terms to be used herein. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in the art to which this subject matter pertains. The following definitions are provided for clarity.

[0052] The term "a" or "an" as used herein includes the singular and the plural, unless specifically stated otherwise. Therefore, the terms "a," "an", "at least one", or “at least two” can be used interchangeably in this application.

[0053] As used herein, the verb "comprise" as is used in this description and in the claims and its conjugations are used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded.

[0054] As used herein, the term "about" when used in connection with a numerical value includes ±10% from the indicated value. In addition, all ranges directed to the same component or property herein are inclusive of the endpoints, are independently combinable, and include all intermediate points and ranges. It is understood that where a parameter range is provided, all integers within that range, and tenths thereof, are also provided by the invention.

[0055] As used herein, according to some embodiments, the term “composite material” refers to a combination of two or more materials with different physical and chemical properties, such as Young’s modulus, thermal expansion coefficient, specific weight, solubility, reactivity, and dielectric constant, to name a few. According to some embodiments, when they are combined, they create material properties unlike the individual elements. Within the finished structure, the individual elements remain separate and distinct, in accordance with some embodiments.

[0056] As used herein, according to some embodiments, the term “porous composite material" refers to a composite material that includes pores in a relative volume of at least about 15% (v / v) more compared to its corresponding “non-porous composite material”.

[0057] As used herein, according to some embodiments, the terms “non-porous composite material, “comparable non-porous composite material”, “corresponding non-porous composite material”, “respective non-porous composite material”, “non-porous analog” or any other interchangeable related term refers to the same composition of the material, i.e. same materials, and proportions combining thereof, as of a correlative porous composite material, but having a lower percentage volume of pores by at least about 15% (v / v) compared to its porous composite material correlative. As used herein, according to some embodiments, the term “open and / or closed pores” refers to pores within the porous composite material that are either open to the material’s solidsolid interface and / or air-solid surface, or to pores that are closed cells and therefore are not exposed to any material’s surfaces.

[0058] As used herein, according to some embodiments, the term “pre-polymer” refers to a monomer, oligomer, initiator, cross-linker, polymer, or any combination thereof, that can be further polymerized and / or manipulated to create the final designed polymer resin within the composite material.

[0059] As used herein, according to some embodiments, the term “polymer" refers to a soluble thermoplastic polymer that is used to create the resin of the composite material. It can be the initial polymer, the whole designed polymer, or it can be a polymer that is further cured, polymerized, cross-linked, entangled, rearranged, assembled, disassembled, or chemically and / or physically manipulated by any other means.

[0060] As used herein, according to some embodiments, the term “thermal stress” refers to the stress that is developed between the assembled (semi)conductive entity and / or substrate and a composite material upon heating. The thermal stress originates from 1. the difference between the thermal expansion coefficient (CTE) of the two distinctive materials (the composite and the (semi)conductive materials), and 2. the modulus of the materials. This dependency is represented by the formula: o = Ea T, whereas o is the thermal stress, E is the modulus, a is the thermal expansion coefficient (CTE), and AT is the temperature change before and after heating the assembly.

[0061] As used herein, according to some embodiments, the term “essentially incapable of solubilizing” refers to a solvent that cannot solubilize the polymer or the pre-polymer even when the composite material is exposed to this solvent in an amount that is higher by about 1000-fold compared to the first solubilizing solvent. According to some embodiments, the incapability to solubilize is expressed at the provided relevant temperature and pressure conditions.

[0062] As used herein, according to some embodiments, the term “essentially homogenously distributed pores” refers to pores that are distributed throughout the composite material in an even manner on X-Y, X-Z, and Y-Z planes on average. According to some embodiments, the majority of the pores are not segregated. As used herein, according to some embodiments, the term “essentially dried composite material” refers to composite material wherein any of the solvents used to create it were mostly evaporated, and less than about 15% of the solvent was left.

[0063] As used herein, according to some embodiments, the term “packaging” which can be interchangeably referred to as “electronic packaging” or “printed circuit board assemblies”, refers to the design and production of enclosures for electronic devices. Packaging must consider protection from mechanical damage, cooling, radio frequency noise emission, and electrostatic discharge, in accordance with some embodiments, and designated packaging material should be considered.

[0064] There provided herein, in accordance with some embodiments, an electronic system including one or more (semi)conductive entities attached to a substrate, and a porous dielectric composite material, wherein the composite material is located over the one or more (semi)conductive entities and the substrate, wherein the composite material includes: a polymer and a non-conductive filler, wherein the composite material is nano / micro porous, wherein the pores are essentially homogenously distributed and, wherein a thermal stress between the composite material and the one or more (semi)conductive entities is at least about 1.5 -fold lower compared to a non-porous analog.

[0065] Advantageously, according to some embodiments, the thermal stress between the composite material and the one or more (semi)conductive entities is at least about 2-fold lower compared to a non-porous analog. For example, according to some embodiments, the thermal stress between the composite material and the one or more (semi)conductive entities is at least about 3 -fold lower, at least about 4-fold lower, or at least about 5 -fold lower compared to a non-porous analog. Each possibility is a separate embodiment. Surprisingly, and according to some embodiments, the thermal stress between the two types of materials is substantially reduced as disclosed herein, when a porosity is introduced into an identical composition of composite material, i.e. the same polymer and filler components are used, and the ratio between the components is the same as in the non-porous analog.

[0066] According to some embodiments, the one or more (semi)conductive entities attached to a substrate and / or the substrate may include but are not limited to silicon, copper, adhesive, carbon, silver, gold, gallium, arsenide, tungsten, polymer, oxides, ceramics, aluminum, zirconium, glass, and any combination thereof. Each possibility is a separate embodiment. According to some embodiments, the substrate and / or the entities include semiconductive material. According to some embodiments, the substrate and / or entities include silicon.

[0067] According to some embodiments, the thermal stress between the composite material and the one or more (semi)conductive entities is linearly dependent on the difference between the thermal expansion coefficient of the composite vs. the substrate and / or entities and linearly dependent on their moduli.

[0068] According to some embodiments, the thermal expansion coefficient of the substrate and / or (semi)conductive entities is less than about 15 ppm / °C, for example, less than about 12 ppm / °C, less than about 10 ppm / °C, less than about 8 ppm / °C, less than about 5 ppm / °C, or less than about 3 ppm / °C. Each possibility is a separate embodiment.

[0069] According to some embodiments, the porosity introduced into the composite material is designed to lower the thermal expansion coefficient of the composite in general, and more specifically to level it down towards the low thermal expansion coefficient of the substrate and / or (semi)conductive entities. According to some embodiments, the porous composite material is characterized by a thermal expansion coefficient that is lower compared to a non- porous analog by at least about 10%, for example, by at least about 15%, at least about 20%, at least about 25%, or at least about 30%. Each possibility is a separate embodiment. Advantageously, and according to some embodiments, the lower thermal expansion of the porous composite material proportionally reduces the thermal stress between the composite material and the substrate and / or (semi)conductive entities.

[0070] According to some embodiments, the porous composite material is characterized by a biaxial modulus that is lower compared to a non-porous analog by at least about 30%, for example, by at least about 40%, at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 90%, at least about 100%, or at least about 120%. Each possibility is a separate embodiment. Advantageously, and according to some embodiments, the lower modulus of the porous composite material proportionally reduces the thermal stress between the composite material and the substrate and / or (semi)conductive entities.

[0071] According to some embodiments, the porous composite material is characterized by a density that is lower compared to a non-porous analog by at least about 15%, for example, by at least about 20%, at least about 30%, at least about 50%, at least about 60%, or at least about 70%. Each possibility is a separate embodiment. According to some embodiments, the density is equal across and along the composite material X-Y-Z planes. According to some embodiments, the lower density of the porous composite material is attributed to its porosity.

[0072] According to some embodiments, the porous composite material is characterized by a dielectric constant that is lower compared to a non-porous analog by at least about 30%, for example, by at least about 40%, at least about 50%, or at least about 60%. Each possibility is a separate embodiment.

[0073] According to some embodiments, the pores are heterogeneous, ranging in size from about 50 nm to 5 pm. According to some embodiments, the pores in the nano range are in a size of about 50-200 nm, about 200-500 nm, about 500-700 nm, or about 700-1000 nm. Each possibility is a separate embodiment. According to some embodiments, the pores in the micro range are in a size of about 1-2 pm, about 2-3 pm, about 3-4 pm, or about 4-5 pm. Each possibility is a separate embodiment. A reference is now made to a cross-section micrograph in FIG. la and its x5 magnification FIG. lb to exemplify pore sizes in the porous composite material at the nano and micro ranges. A reference without a filler is exemplified in a crosssection micrograph in FIG. 1c and its magnification in FIG. Id, showing the porosity of the polymer resin.

[0074] According to some embodiments, the pores are homogeneously distributed across and along the composite material. A reference is now made to the micrographs in FIG. la-d to exemplify the distribution of the pores.

[0075] According to some embodiments, the pores are opened and / or closed pores. According to some embodiments, the pores are mainly closed. According to some embodiments, at least about 60% of the pores are closed, for example, at least about 70%, at least about 80%, or at least about 90% of the pores are closed. Each possibility is a separate embodiment. According to some embodiment, the porous composite material is essentially non-permeable. According to some embodiment, the porous composite material is not a membrane.

[0076] According to some embodiments, the pores include gas, liquid, or both. Each possibility is a separate embodiment. According to some embodiments, the gas includes ambient air. According to some embodiments, the gas is pressure-reduced. According to some embodiments, the gas is over-pressured. According to some embodiments, the liquid includes a solvent and / or water. According to some embodiments, the filler includes organic and / or inorganic particulates. According to some embodiments, the organic particulate may be but not limited to a thermosetting polymer. According to some embodiments, the inorganic particulate may be ceramics, oxides, carbonaceous, alloys, or any combination thereof. Each possibility is a separate embodiment.

[0077] According to some embodiments, the filler is selected from but not limited to Nomex, Kevlar, para-aramid, ortho-aramid, SiCh, SiCh-Li / Ba-Al, SiCh / EEOs / Zn / Sr / Li, Zr-Si, Si-C, Si- N, ZrO2, ZnO, TiCh, B-N, AI2O3, ZrWhCh. derivatives thereof, doped versions thereof, or any combination thereof. Each possibility is a separate embodiment. According to some embodiments, the filler includes but is not limited to Aramid / Kevlar, SiCh, or ZrW2C . Each possibility is a separate embodiment.

[0078] According to some embodiments, the shape of the filler is selected from a sphere, platelet, rod, fiber, an irregular shape, or any combination thereof. Each possibility is a separate embodiment.

[0079] According to some embodiments, the composite includes the filler and the polymer in a ratio of about 80 / 20 to 30 / 70 (v / v), respectively. According to some embodiments, the filler and the polymer are in a ratio of about 80 / 20-70 / 30, about 70 / 30-60 / 40, about 60 / 40-50 / 50, about 50 / 50-60 / 40, or about 60 / 40-70 / 30. Each possibility is a separate embodiment.

[0080] According to some embodiments, the filler is homogeneously distributed in the composite material. A reference is now made to a micrograph in FIG. la and FIG. lb to exemplify the homogeneous distribution of the filler across the composite material.

[0081] According to some embodiments, the polymer includes but is not limited to epoxy, polyimide, polyamide, polyurethane, bismaleimide, polyacrylate, polyethylene terephthalate, polyethylene naphthalates, polylactic acid, polyester, polypropylene, polyvinyl pyrrolidone, polyvinyl acetate, melamine -formaldehyde, urea-formaldehyde, polyolefin, polyphenol, polysiloxane, silicon resin, benzocyclobutene (BCB) polymer, derivatives thereof, or any combination thereof. Each possibility is a separate embodiment. According to some embodiments, the polymer includes but is not limited to epoxy, bismaleimide, polyester, polyimide, derivatives thereof, or any combination thereof. Each possibility is a separate embodiment. According to some embodiments, the composite material is used for but not limited to an application selected from the group consisting of coating, spacing, packaging, soldering, sealing, additive manufacturing, ink-jetting, associating, and encapsulating the substrate and / or one or more (semi)conductive entities. Each possibility is a separate embodiment. According to some embodiments, the composite material is used for electronic packaging.

[0082] According to some embodiments, the coating has a thickness of about 5-300 pm, for example, about 5-30 pm, about 30-70 pm, about 70-100 pm, about 100-150 pm, about 150- 200 pm, about 200-250 pm, or about 250-300 pm. Each possibility is a separate embodiment.

[0083] There is provided herein, in accordance with some embodiments, a method of producing an electronic system, the method including: providing a substrate including one or more (semi)conductive entities; treating the substrate by exposing it to a first dielectric composite solution including a first solvent, a non-conductive filler, and a polymer or a prepolymer, wherein the first solvent is capable of solubilizing the polymer or the pre-polymer; exposing the treated substrate to a second solvent, wherein the second solvent is essentially incapable of solubilizing the polymer, and wherein the second solvent is miscible with the first solvent; and evaporating the solvent mixture to form essentially homogenously distributed pores in an essentially dried composite material, thereby obtaining an electronic system including the porous composite material located over the substrate and the one or more (semi)conductive entities.

[0084] Reference is now made to Fig. 2, which schematically illustrates in flowchart 100 the method for producing the electronic system, in accordance with some embodiments. In step 110 a substrate including one or more (semi)conductive entities is provided. In step 120 the substrate is treated by exposing it to a first dielectric composite solution including a first solvent, a non-conductive filler, and a polymer or a pre-polymer, wherein the first solvent is capable of solubilizing the polymer or the pre-polymer. In step 130 the treated substrate is exposed to a second solvent, wherein the second solvent is essentially incapable of solubilizing the polymer, and wherein the second solvent is miscible with the first solvent. In step 140 the solvent mixture is evaporated to form essentially homogenously distributed pores in an essentially dried composite material, thereby obtaining an electronic system including the porous composite material located over the substrate and the one or more (semi)conductive entities. In optional step 150, the essentially dried composite material is further cured. According to some embodiments, the polymer and / or pre-polymer is a solid or a semisolid at a temperature of ambient conditions.

[0085] According to some embodiments, the essentially dried composite material is highly viscous. According to some embodiments, the essentially dried composite material is characterized by a viscosity of more than about 100,000 cP while having a shear rate of less than about 1 Hz.

[0086] According to some embodiments, the capability of the solvent mixture to solubilize the polymer is lower compared to the first solvent. Advantageously, and according to some embodiments, exposing the treated substrate to the second solvent causes coagulation, which essentially separates the viscous polymer from the liquid solvent mixture due to its reduced solubility compared to the first solvent. According to some embodiments, this phase separation, which is interchangeably termed ‘phase-inversion’, results in pores within the composite material. The term ‘pores’ can be used interchangeably, but is not obligated to, the term ‘voids’, in accordance with some embodiments.

[0087] Reference is now made to FIG. 3 and FIG. 4, which schematically illustrate in flowcharts 300 and 500 the production method of the porous composite material vs. a non- porous composite material, respectively, in accordance with some embodiments. In step 310 the substrate 313 and one or more (semi)conductive entities 312 are provided to afford the assembly 311. The counterparts in 500 are step 510, substrate 513, and entities 512 to afford the assembly 511. In step 320 the substrate is treated with a first dielectric composite solution 322 to afford the assembly 321. which includes the first solvent, the filler 323, and the polymer. The counterparts in 500 are step 520, composite solution 522, and filler 523 to afford the assembly 521. In step 340 the treated substrate is exposed to a second solvent 342 to afford the second solvent-treated substrate 341 that contains phase-inversion areas or voids 343 due to the lower solubility in the second solvent, in accordance with some embodiments. The counterparts in 500 are not part of the production method and therefore do not include voids, phase inversion, or mechanism of creating pores, in accordance with some embodiments. In step 350 the solvent mixture is evaporated to afford the porous composite material located over the substrate and the one or more (semi)conductive entities to afford 351. in accordance with some embodiments. The composite material 352 includes pores 353 that are homogeneously distributed. The non-equal comparative parts in 500 are the obtained non-porous composite material 532 which is located over the substrate and the one or more (semi)conductive entities to afford 531. in accordance with some embodiments. FIG. 5a and 5b represent comparable cross-section micrographs to exemplify the porosity in the porous composite material vs. the lack of porosity in a comparative non-porous composite material, in accordance with some embodiments.

[0088] According to some embodiments, the fdler is insoluble in the first and second solvents.

[0089] According to some embodiments, a surfactant is further added to the filler. According to some embodiments, the filler is hydrophilic or hydrophobic, and the surfactant is hydrophobic or hydrophilic, respectively.

[0090] According to some embodiments, the pre-polymer includes but is not limited to a monomer, oligomer, initiator, cross-linker, catalyst, polymer, or any combination thereof. Each possibility is a separate embodiment.

[0091] According to some embodiments, the treating of the substrate by exposing it to a first dielectric composite solution and / or exposing the treated substrate to the second solvent is performed by but not limited to a technique selected from the group consisting of spin-coating, dip-coating, spray-coating, layer-by-layer deposition, vapor deposition, and any combination thereof.

[0092] According to some embodiments, the evaporating is performed by a technique selected from the group consisting of but not limited to spin-drying, heating, vacuuming, venting, gasblowing, incubating, or any combination thereof. Each possibility is a separate embodiment.

[0093] According to some embodiments, the essentially dried composite material is further cured. According to some embodiments, the curing is performed with or without a catalyst and / or a cross linker.

[0094] In some embodiments, the curing and / or drying is performed at a temperature lower than the Tgor melting point of the polymer.

[0095] According to some embodiments, the first solvent may be selected from, but not limited to, toluene, xylene, anisole, chlorobenzene, nitrobenzene, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-Methyl-2-pyrrolidone (NMP), acetone, tetrachloroethane, gamma-butyrolactone (GBL), tetrahydrofuran (THF), dioxane, dichloromethane (DCM), chloroform, phenol, cresol, benzyl alcohol, ethylene glycol ether, Propylene Glycol Monomethyl Ether Acetate (PGM-AC), or any combination thereof. Each possibility is a separate embodiment. According to some embodiments, the first solvent may be selected from, but not limited to, anisole, NMP, and PGM-AC. Each possibility is a separate embodiment.

[0096] According to some embodiments, the second solvent may be selected from, but is not limited to, isopropanol (IPA), water, ethanol, methanol, hexane, heptane, pentane, octane, acidic solution, alkaline solution, diethyl ether, methyl tert-butyl ether (MTBE), and any combination thereof. Each possibility is a separate embodiment. According to some embodiments, the second solvent may be selected from, but is not limited to, water, IPA, and ethanol. Each possibility is a separate embodiment.

[0097] According to some embodiments, the method utilizes a first solvent selected from NMP, anisole, PGM-AC, and a corresponding second solvent selected from water, IPA, and ethanol, respectively. Each possibility is a separate embodiment.

[0098] The following examples are presented in order to more fully illustrate some embodiments of the invention. They should, in no way be construed, however, as limiting the broad scope of the invention. One skilled in the art can readily devise many variations and modifications of the principles disclosed herein without departing from the scope of the invention.

[0099] EXAMPLES

[0100] Example 1 - Preparation of a composite solution of bismaleimide (BMI) and silica (SiOz) particles

[0101] An amount of 10 gr of silica particles having a diameter of 0.5 pm was dried in a vacuum oven (0.3 atm) for 1 hour at a temperature of 120 °C. The particles were dispersed in 15 gr of anisole by using a vortex for 1 min. The resulting dispersion was then ultra-sonicated for 5 min by repeating cycles of 3-sec work and 5-sec rest in an amplitude of 75%. Following the ultra-sonication, an amount of 20 gr of BMI6100 (5 gr of BMI and 15 gr of anisole, Designer Molecules Inc.) was admixed into the silica dispersion together with 0.3 gr of dicumyl peroxide curing agent, followed by dispersing in a vortex for 1 min. The resulting dispersion was ultra-sonicated for 5 min by repeating cycles of 3-sec of work and 5-sec of rest in an amplitude of 75%. Finally, the resulting composite solution was deformed for 2 min at 1000 rpm to remove bubbles.

[0102] Example 2 - Preparation of a non-porous composite film of bismaleimide (BMI) and silica (SiCh) particles on wafers of silicon or sintered alumina.

[0103] A wafer having a diameter of 4” was spin-coated by applying a volume of 3 m composite solution and using a spinning program consisting of acceleration by 1000 rpm / sec2up to a spinning rate of 500 rpm, holding at 500 rpm for 54 sec, and then a declaration by 200 rpm / sec2until a final stop is reached. The coated wafer was then dried on a hot plate set to 100 °C for 10 min. Finally, a curing was performed in an oven programmed to ramp the temperature by 5 °C / min up to 230 °C and then stay at that temperature for 75 min. A cross-section micrograph is exemplified for this system in FIG. 5b.

[0104] The thermal stress was measured using a Tencor Flexus 2320, by measuring the bow of the wafers relative to temperature. The thermal stress between the composite material and the silicon or sintered alumina was found to be - 1.99 MPa / °C and -1.15 MPa / °C, respectively. The composite’s biaxial modulus was found to be 18.0 GPa, and the composite’s CTE was found to be 14.0 ppm / °C.

[0105] Example 3 - Preparation of a porous composite film of bismaleimide (BMI) and silica (SiCh) particles on wafers of silicon or sintered alumina.

[0106] A wafer having a diameter of 4” was spin-coated by applying a volume of 3 m composite solution and using a program consisting of acceleration by 1000 rpm / sec2up to a spinning rate of 500 rpm, holding at 500 rpm for 54 sec, and then a declaration by 200 rpm / sec2until a final stop is reached. The coated wafer was then dipped in a bath of isopropanol for 5 min followed by a spin drying for 1 min at 9000 rpm. The coated wafer was further dried on a hot plate set to 100 °C for 10 min. Finally, a curing was performed in an oven programmed to ramp the temperature by 5 °C / min up to 230 °C and then stay at that temperature for 75 min. A cross-section micrograph is exemplified for this system in FIG. 5a.

[0107] The thermal stress was measured using a Tencor Flexus 2320, by measuring the bow of the wafers relative to temperature. The thermal stress between the composite material and the silicon or sintered alumina was found to be -0.97 MPa / °C and -0.50 MPa / °C, respectively. These stress values are about 2-fold lower than the corresponding non-porous examples demonstrated in Example 2. The composite’s biaxial modulus was found to be 10.4 GPa which is 1 .7-fold lower than the corresponding non-porous example demonstrated in Example 2, and the composite’s CTE was found to be 12.3 ppm / °C, which is 1.3-fold lower than the corresponding non-porous example demonstrated in Example 2.

[0108] While certain embodiments of the invention have been illustrated and described, it will be clear that the invention is not limited to the embodiments described herein. Numerous modifications, changes, variations, substitutions and equivalents will be apparent to those skilled in the art without departing from the spirit and scope of the present invention as described by the claims, which follow.

Claims

CLAIMS1. An electronic system comprising one or more (semi)conductive entities attached to a substrate, and a porous dielectric composite material, wherein the composite material is located over the one or more (semi)conductive entities and the substrate, wherein the composite material comprises: a polymer and a non-conductive fdler, wherein the composite material is nano / micro porous, wherein the pores are essentially homogenously distributed and, wherein a thermal stress between the composite material and the one or more (semi)conductive entities is at least about 1.5-fold lower compared to a non-porous analog.

2. The electronic system of claim 1, wherein the thermal stress between the composite material and the one or more (semi)conductive entities is at least about 2-fold lower compared to a non-porous analog.

3. The electronic system of any one of claims 1 and 2, wherein the composite material is characterized by a thermal expansion coefficient that is lower compared to a non-porous analog by at least about 10%.

4. The electronic system of any one of claims 1-3, wherein the composite material is characterized by a biaxial modulus that is lower compared to a non-porous analog by at least about 30%.

5. The electronic system of any one of claims 1-4, wherein the composite material is characterized by a density that is lower compared to a non-porous analog by at least about 15%.

6. The electronic system of any one of claims 1-5, wherein the composite material is characterized by a dielectric constant that is lower compared to a non-porous analog by at least about 30%.

7. The electronic system of any one of claims 1-6, wherein the pores are heterogenous ranging in size from about 50 nm to 5 pm.

8. The electronic system of any one of claims 1-7, wherein the pores are opened and / or closed pores.

9. The electronic system of any one of claims 1-8, wherein the pores comprise gas, liquid, or both.

10. The electronic system of claim 9, wherein the gas comprises ambient air.

11. The electronic system of any one of claims 1-10, wherein the filler is selected from Nomex, Kevlar, para-aramid, ortho-aramid, SiCh, SiCh-Li / Ba-Al, SiCh / BaOs / Zn / Sr / Li, Zr-Si, Si-C, Si-N, ZrCh, ZnO, TiCh, B-N, AI2O3, ZrW20s, doped versions thereof, or any combination thereof.

12. The electronic system of claim 11, wherein the filler comprises Aramid / Kevlar, SiCh, or ZrW2C>8.

13. The electronic system of any one of claims 1-12, wherein a shape of the filler is selected from a sphere, platelet, rod, fiber, an irregular shape, or any combination thereof.

14. The electronic system of any one of claims 1-13, wherein the composite comprises the filler and the polymer in a ratio of about 80 / 20 to 30 / 70 (v / v), respectively.

15. The electronic system of any one of claims 1-14, wherein the filler is homogeneously distributed in the composite material.

16. The electronic system of any one of claims 1-15, wherein the polymer comprises epoxy, polyimide, polyamide, polyurethane, bismaleimide, polyacrylate, polyethylene terephthalate, polyethylene naphthalates, polylactic acid, polyester, polypropylene, polyolefin, polyphenol, silicon resin, benzocyclobutene (BCB) polymer, derivatives thereof, or any combination thereof.

17. The electronic system of any one of claims 1-16, wherein the composite material is used for an application selected from the groups consisting of coating, spacing, packaging, sealing, additive manufacturing, ink-jetting, associating, or encapsulating one or more (semi)conductive entities.

18. The electronic system of claim 17, wherein the coating has a thickness of about 5-100 pm.

19. A method of producing an electronic system, the method comprising:providing a substrate comprising one or more (semi)conductive entities; treating the substrate by exposing it to a first dielectric composite solution comprising a first solvent, a non-conductive filler, and a polymer or a pre-polymer, wherein the first solvent is capable of solubilizing the polymer or the pre-polymer; exposing the treated substrate to a second solvent, wherein the second solvent is essentially incapable of solubilizing the polymer, and wherein the second solvent is miscible with the first solvent; and evaporating the solvent mixture to form essentially homogenously distributed pores in an essentially dried composite material, thereby obtaining an electronic system comprising the porous composite material located over the substrate and the one or more (semi)conductive entities.

20. The method of claim 19, wherein the filler is insoluble in the first and second solvents.

21. The method of any one of claims 19 and 20, wherein a surfactant is further added to the filler.

22. The method of any one of claims 19-21, wherein the polymer and / or pre-polymer is solid or semi-solid.

23. The method of any one of claims 19-22, wherein the pre-polymer comprises a monomer, oligomer, initiator, catalyst, cross-linker, polymer, or any combination thereof.

24. The method of any one of claims 19-23, wherein the treating of the substrate by exposing it to a first dielectric composite solution and / or the exposing of the treated substrate to the second solvent, is performed by a technique selected from the group consisting of spin-coating, dip-coating, spray-coating, layer-by-layer deposition, vapor deposition, and any combination thereof.

25. The method of any one of claims 19-24, wherein the essentially dried composite material is characterized by a viscosity of more than about 100,000 cP while having a shear rate of less than about 1 Hz.

26. The method of any one of claims 19-25, wherein the essentially dried composite material is further cured.

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