WO2022189430A2

WO2022189430A2 - Composite material

Info

Publication number: WO2022189430A2
Application number: PCT/EP2022/055889
Authority: WO
Inventors: Joerg Schuhmacher; Stephanie Mangold; Sabine Pichler-Wilhelm; Jonas Dimroth
Original assignee: Schott Ag
Priority date: 2021-03-08
Filing date: 2022-03-08
Publication date: 2022-09-15
Also published as: DE102021202222A1; WO2022189430A3

Abstract

The present invention relates to a composite material for protecting electronic components, comprising at least a first material fraction and a second material fraction, wherein said first material fraction comprising at least one hybrid polymer, wherein said at least one hybrid polymer comprising at least one of - sol-Gel compound having a total organic carbon, TOC, content below 75 weight-% and above 0,01 weight-%, preferably above 10 weight-%, preferably above 20 weight-%, - Silicone resin and/or - Polysilsesquioxane, and/or combinations thereof, and said second material fraction comprising a particle filler.

Description

COMPOSITE MATERIAL

The present invention relates to a composite material for protecting electronic components, comprising at least a first material fraction and a second material fraction.

The present invention further relates to an encapsulating, moulding, potting, underfill, bonding and/or coating mass comprising a composite material.

The present invention further relates to an electronic and/or semiconductor component comprising a composite material.

The present invention even further relates to a use of a composite material for encapsulating, moulding, potting, underfill, bonding and/or coating of an electronic and/or semiconductor component.

The present invention further relates to a precursor paste for a composite material.

The present invention further relates to an encapsulating, moulding, potting, underfill, bonding and/or coating mass comprising a precursor paste.

The present invention even further relates to a use of a precursor paste for providing a composite material for encapsulating, moulding, potting, underfill, bonding and/or coating of an electronic and/or semiconductor component.

Although applicable in general to any component, the present invention will be described with regard to electronic and/or semiconductor components.

In the electronics industry, it is common practice to apply a casting compound to the sensitive electronic semiconductor-based components like chips, memory elements, etc. for - in particular - mechanical protection as well as for better handling when integrated into the integrated circuits, e.g. printed circuit boards, PCBs. The compounds, which are used, are e.g. dispersions or pastes comprising for instance a liquid resin precursor or thermoplastics and usually at least one particulate filler, e.g. S1O2, AI2O3, etc. These are usually applied with a suitable application device around, on or under the component and then cured to a solid composite material in a subsequent step.

Often the resin precursors or thermoplastics are purely organic based. For instance, the use of bifunctional epoxy resins is shown in US 9,045,585 B2 or US 10,043,782 B2 and the use of polyurethanes is shown in US 10,674,612 B2. These materials are usually mixed with bifunctional hardeners. After application of the casting compound, both components are thermally reacted and crosslinked to form a three- dimensional network.

It is further known that casting, bonding and underfilling compounds, where organo- based resins are used, can only be permanently used at temperatures below a maximum of 200 °C. If the compounds are used at higher temperatures over a longer period of time, degradation of the polymer network occurs, which can lead to complete ashing. The desired function as protection against mechanical stress or against humidity impact is then lost.

However, future generations of electronic components may likely be operated at temperatures above 200 °C, e.g. based on materials such as SiC, as these enable higher power/switching frequencies. Accordingly, casting, bonding and underfilling compounds must also be able to withstand temperatures above 200 °C without significant degradation. In US 7,352,045 B2 a glass as an encapsulation material is described, but its processing temperatures are very high and not acceptable for some of the parts in the electronic component.

Furthermore, organic materials, for example polymers, can be used as encapsulants, adhesives and for filling gaps in electronic applications, with low- expansion fillers. Organic compounds, especially polymers, usually show a very high thermal expansion. If such polymers are used for encapsulating, bonding or filling gaps, in particular for encapsulating, bonding or underfilling inorganic materials, as is the case in the semiconductor industry, but also in optical applications, difficulties can arise if the adhesive bond is exposed to major thermal fluctuations. Due to the very different expansion coefficients of the polymer and the inorganically formed materials to be bonded, thermomechanical stresses are induced between the materials to be bonded, which in the worst case can even lead to mechanical failure of the bonded component, e.g. by crack formation, delamination or the like.

Embodiments of the present invention therefore address the problem of a composite material for protecting in particular electronic components, which has an enhanced temperature stability, in particular is stable for temperatures of more than 200 °C.

Embodiments of the present invention address the further problem of a composite material for protecting in particular electronic components, which has a very low thermal expansion, in particular below 50 ppm.

Embodiments of the present invention address the further problem of providing an alternative composite material, an alternative encapsulating, moulding, potting, underfill, bonding and/or coating mass, an alternative an electronic and/or semiconductor component and an alternative use of a composite material.

In an embodiment, the present invention provides a composite material for protecting electronic components, comprising at least a first material fraction and a second material fraction, wherein said first material fraction comprising at least one hybrid polymer, wherein said at least one hybrid polymer comprising at least one of sol-gel compound having a total organic carbon, TOC, content below 75 weight-% and above 0,01 weight-%, preferably above 10 weight-%, preferably above 20 weight-%,

Silicone resin and/or Polysilsesquioxane, and/or combinations thereof, and said second material fraction comprising a particle filler. In a further embodiment, the present invention provides an encapsulating, moulding, potting, underfill, bonding and/or coating mass comprising a composite material according to one of the claims 1-15.

In a further embodiment, the present invention provides an electronic and/or semiconductor component comprising a composite material according to one of the claims 1 -15 and/or a mass according to claim 16.

In a further embodiment, the present invention provides a use of a composite material according to one of the claims 1-15 for encapsulating, moulding, potting, underfill, bonding and/or coating of an electronic and/or semiconductor component, preferably an RFID-chip, preferably wherein said composite material is suitable for forming electrical insulators, preferably wherein said composite material is suitable for use as electrical insulator in electrical feedthroughs, preferably wherein said electrical insulator is used as an insulation barrier for electrical feedthroughs configured for use in harsh environments.

In a further embodiment, the present invention provides a precursor paste for an electrically insulating composite material in particular according to one of the claims 19-29. Said composite material is in particular suitable for forming electrical insulators. Said composite material is in particular suitable for use as electrical insulator in electrical feedthroughs. In particular, the electrical insulator may be used as an insulation barrier for electrical feedthroughs configured for use in harsh environments. Examples for harsh environments include high temperature applications as well as chemically or radiation contaminated environments, such as in the chemical industry or in energy plant and reactor technology. The composite material is in particular suitable for forming temperature resistant insulation barriers surrounding an electrical conductor of the feedthrough.

The precursor paste may be provided in the form of a spreadable paste that can be applied to the feedthrough, in particular to an electrical conductor of the feedthrough, and which forms a temperature-resistant electrical insulation after curing. Advantageously, the formed insulation barrier is stable even when exposed to high temperatures for long periods of time, e.g. for multiple months, or even for years. In a further embodiment, the present invention provides a precursor paste, preferably in form of a spreadable paste, for a composite material according to one of the claims 1-15 for protecting electronic components, preferably an electrically insulating composite material, said precursor paste comprising at least a first material fraction and a second material fraction, wherein said first material fraction comprising at least one chemically reactive hybrid polymer, wherein said at least one chemically reactive hybrid polymer comprising at least one of a reactive sol-gel compound having a total organic carbon, TOC, content below 85 weight-% and above 0,01 weight-%, preferably above 10 weight- %, preferably above 20 weight-%, a reactive or inert silicone resin and/or reactive Polysilsesquioxane, and/or combinations thereof, and said second material fraction comprising a particle filler.

In a further embodiment, the present invention provides an encapsulating, moulding, potting, underfill, bonding and/or coating mass comprising a precursor paste according to one of the claims 19-29.

In a further embodiment, the present invention provides a use of a precursor paste according to one of the claims 19-29 for providing a composite material for encapsulating, moulding, potting, underfill, bonding and/or coating of an electronic and/or semiconductor component, preferably an RFID-chip, preferably wherein said composite material is suitable for forming electrical insulators, preferably wherein said composite material is suitable for use as electrical insulator in electrical feedthroughs, preferably wherein said electrical insulator is used as an insulation barrier for electrical feedthroughs configured for use in harsh environments.

Examples for a sol-gel compound may be based on a metalloxide or metalloid network, preferably a S1O2 network. As described in WO 2014/086619 A2, which is herein incorporated by reference, metal alcoholates are preferably used as sol-gel starting materials for the sol-gel compound or sol-gel-matrix, preferably in the form of alkoxysi lanes. A tetraalkoxysilane, e.g. tetraethoxysilane (TEOS) in combination with a trialkoxysilane, which has an organic crosslinkable functionality, may be preferred. In order to ensure a high degree of crosslinking within the hybrid polymer sol-gel matrix, alkoxysilanes with the following functionalities can be used: epoxy, acrylate, methacrylate, vinyl or allylsilanes. Stable or flexible network structures can be built up depending on the setting of the residues. Glycidoxypropyltriethoxysilane (GPTES), methacryloxypropyltrimethoxysilane (MEMO or MPTMS), methacryloxypropyl-triethoxysilane (MPTES) or vinyltriethoxysilane (VTES) may be used for example. The hydrolysate is produced by the specific reaction of the monomers with water. Preferably, in the presence of a catalyst, especially an acid, e.g. HCI, para-toluenesulfonic acid, but in a special version the hydrolysis is carried out with an aqueous nanoparticle dispersion. The inorganic degree of crosslinking of the hydrolysate is adjusted by the ratio of water to monomers, the inorganic degree of crosslinking is preferably between 11 and 50 %, preferably between 15 and 35 %.

Embodiments of the present invention may realize the advantage of a low coefficient of thermal expansion of the composite material, i.e. the resulting coefficient of thermal expansion for the entire composite material is reduced compared to conventional composite materials for protecting electronic components.

Embodiments of the present invention may realize the advantage of a high temperature stability, in particular for temperatures of more than 200 °C, e.g. in the temperature range between 60 °C and at least 300 °C, in particular up to 400 °C at least for multiple months.

Embodiments of the present invention may realize the advantage of a cheap and easy usable composite material.

Embodiments of the present invention may realize the advantage of an easy producible composite material.

Embodiments of the present invention may realize the advantage of a composite material with enhanced flexibility in terms of adaptability of properties, e.g. dielectric properties, thermal conductivity, electric conductivity, electro-magnetic shielding, viscosity, colour or the like.

The term “hybrid polymer” is to be understood in its broadest sense and refers in particular in the claims, preferably in the description to polymeric materials that combine structural units of different material classes at the molecular level. In contrast to materials with defined phase boundaries and weak interactions between the phases and nanocomposites using of nanoscale fillers, the structural units of hybrid polymers are linked together at the molecular level. Examples for hybrid polymers are sol-gel compounds, silicone resins, polysilsesquioxanes.

The formulation “particles of said particle filler” in particular in the claims, preferably in the description may mean or refer to all particles of the particle filler.

Further features, advantages and preferred embodiments are described or may become apparent in the following.

In an embodiment of the present invention, particles of said particle filler having a coefficient of thermal expansion, CTE, of +20 ppm/K or lower, preferably of +15 ppm/K or lower, preferably of +10 ppm/K or lower, preferably of +5 ppm/K or lower, preferably of +2 ppm/K or lower and higher than +0,01 ppm/K, preferably higher than +0,1 ppm/K, preferably higher than +1 ,0 ppm/K. One of the advantages may be that a low CTE is provided enabling composite materials for protecting components in a wider temperature range.

In an embodiment of the present invention, said first material fraction has an alkali ion impurity density smaller than 10 ppm, preferably smaller than 5 ppm, preferably smaller than 3 ppm and higher than 0,01 ppm, preferably higher than 0,1 ppm, preferably higher than 1 ppm. One of the advantages may be that the functionality of the semiconductor components will not be affected on a long-term scale and therefore their reliability is guaranteed.

In an embodiment of the present invention, said composite material has an ignition loss smaller than 30 weight-%, preferably smaller than 25 weight-%, preferably smaller than 20 weight-% and higher than 1 weight-%, preferably higher than 3 weight-%, preferably higher than 5 weight-%, preferably higher than 10 weight-% for temperatures below 400 °C, preferably below 450 °C and above 100 °C. One of the advantages may be that a high temperature stability is provided.

In an embodiment of the present invention, particles of said particle filler having a particle size of d99 < 70 pm, preferably < 40 pm, preferably < 25 pm, preferably < 10 pm and d99 > 0.5 pm, preferably > 1 pm, preferably > 2 pm and/or wherein said particles of said particle filler having a particle size of d95 £ 65 pm, preferably < 35 pm, preferably < 20 pm, preferably < 8 pm and d95 ³ 0.5 pm, preferably > 1 pm, preferably ³ 2 pm and/or wherein said particles of said particle filler having a particle size of dso < 30 pm, preferably < 7 pm, preferably < 3 pm and dso > 0.5 pm, preferably > 1 pm, preferably > 2 pm. One of the advantages may be that an easy and fast homogenization of the particles in the composite material can be obtained, since the collective of the particles has a low specific surface area, SSA, and thus a small tendency to agglomerate.

In an embodiment of the present invention a collective of particles of said particle filler has a specific surface area, SSA, < 3 m²/g, preferably < 2 m²/g, preferably < 1 m²/g, preferably < 0,5 m²/g and above 0,05 m²/g, preferably above 0,1 m²/g. This ensures a small tendency of the particles to agglomerate.

In an embodiment of the present invention, particles of said particle filler having a polydispersity index of more than 3.0, preferably more than 3.5, more preferably more than 4.0, preferably more than 4.5 and below 10.0, preferably below 8.0. This ensures a high filling grade. The term „polydispersity index" relating to the particle size distribution is to be understood as common logarithm (logarithm with base 10) of the quotient of the d9o- and dio-value of the diameter distribution: PI = Iog(d9o/dio). The term „d-value“ as basis for the d9o-value and dio-value is determined as follows:

Independently of their real sphericity, the particles of a powder are generally distinguished with the aid of a volume-equivalent sphere diameter, which has to be measured and are ordered into selected classes according to their size. To represent a particle size distribution, a determination is made of the quantity fractions with which the respective classes of particles are present in the powder.

This is done using different quantity types. If the particles are counted, the quantity type is the number. In the case of weightings, conversely, it is the mass or, in the case of homogeneous density Q_r, the volume. Other types are derived from lengths, projection surfaces and surface areas.

The following are distinguished:

One common quantity measure for describing the particle size distribution in powders is formed by the cumulative distribution Qr. The index r identifies the quantity type according to the table above.

The cumulative distribution function Qr (d) indicates the standardized quantity of all particles having an equivalent diameter less than or equal to d. Explicitly defined below are cumulative distributions of the two most commonplace quantity types:

Particle Number (r = 0).

Let Ni be the number of all particles investigated with a diameter d less than or equal to the diameter di under consideration and let N be the total number of all particles investigated. In that case

Particle Mass (r = 3).

Let m j be the mass of all particles investigated with a diameter d less than or equal to the diameter di under consideration and let m be the total mass of all particles investigated. In that case

In the sense of the invention, di values are understood to be equivalent diameter values for which the Cb (di) cumulative distribution function adopts the following values:

- dio: Cb (dio) = 10%, i.e. 10 weight. -% of the particles have a diameter less than or equal to dio.

- d5o: Cb (dso) = 50%, i.e. 50 weight. -% of the particles have a diameter less than or equal to dso.

- doo: Gb (d9o) = 90%, i.e. 90 weight. -% of the particles have a diameter less than or equal to d9o.

- dgg: Gb (d99) = 99%, i.e. 99 weight. -% of the particles have a diameter less than or equal to d99.

- dioo: Q3 (dioo) = 100%, i.e. 100 weight. -% of the particles have a diameter less than or equal to dioo.

In the sense of the present specification, the term “polydispersity index” may be understood synonymously with the term “polydispersion index”.

In an embodiment of the present invention, particles of said particle filter having a cumulative distribution function of Cb, reai(d) and a deviation of a random sample of n particles defined as

of smaller than 0,030, preferably smaller than 0,020, more preferably smaller than 0,015 from the ideal Andreasson cumulative distribution function Cb, Andreassen, (d), said ideal Andreasson cumulative distribution function Cb, Andreassen, (d) fulfilling

with d being the particle size, D is the maximum particle size and q is a distribution coefficient, with said distribution coefficient q is between 0.2 and 0.5, preferably between 0.22 and 0.4, preferably between 0.24 and 0.38. A small deviation from the ideal Andreassen cumulative distribution function, as disclosed in the non-patent literature of A. H. M. Andreassen et al. , Kolloid-Zeitsch rift 50 (1930) 17-228, ensures a dense packaging of the particles, i.e. high volume filling grades besides their usually small CTE reducing shrinkage upon heating. For instance, if the upper particle size, represented by the d9o value, is limited to several 10 pm or even smaller for application-related reasons, nanopowders must be used as ultra-fine fractions represented by the dio value to fulfill the above condition.

In an embodiment of the present invention, said composite material providing a dielectric strength is higher than 20 kV/mm, preferably higher than 35 kV/mm, preferably higher than 40 kV/mm. One of the advantages may be that the integrity of the semiconductor component will be kept also in cases of undesired voltage stress.

In an embodiment of the present invention, particles of said particle filler comprising carbon particles, preferably graphite particles, having a fraction of 10 weight-% or less of all particles. One of the advantages may be that a low glow loss or char yield respectively is obtained.

In an embodiment of the present invention, a part of particles of said second material fraction having a coefficient of thermal expansion, CTE, of 1 ppm/K or lower, preferably having a negative coefficient of thermal expansion. One of the advantages may be that a very low overall CTE can be obtained for the composite material. Another advantage may be an enhanced flexibility in adapting the CTE to the underlying CTE of the semiconductor component being protected with said composite material.

In an embodiment of the present invention, said particles comprising at least one of amorphous silicon dioxide or zirconium tungstate, preferably crystalline zirconium tungstate, preferably crystalline zirconium tungstate in a-, b-, and/or y-phase. One of the advantages may be that particles with a very low or even negative CTE are used enabling a very low overall CTE for the composite material, in particular for crystalline zirconium tungstate in the a-, b-, and/or y-phase.

In an embodiment of the present invention, said second material fraction having a volume fraction of more than 10 vol-%, preferably more than 20 vol-%, preferably more than 30 vol-%, preferably more than 35 vol-%, preferably more than 40 vol-% and below 80 vol-%, preferably below 70 vol-% of the total volume of the composite material. One of the advantages may be that an easy and flexible adaption of the overall CTE is enabled and in particular a low overall CTE for the composite material.

In an embodiment of the present invention, said composite material having a coefficient of thermal expansion, CTE of +50 ppm/K or lower, preferably of +30 ppm/K or lower and above +1 ppm/K, preferably between +1 and +20 ppm/K, preferably between +2 and +18 ppm/K, preferably between +2 and +16 ppm/K, preferably between +4 and +16 ppm/K or between +2 and +5 ppm/K. One of the advantages may be that a low overall CTE can be obtained for the composite material, which fits well to the semiconductor component as well as to the other substrate or housing components, which the composite material may be in contact with.

In an embodiment of the present invention said composite material having a density of below 6 g/cm³, preferably below 3 g/cm³, preferably below 2 g/cm³ and above 1 g/cm³, preferably 1 .5 g/cm³. One of the advantages may be that an easy application of the composite material is enabled. In an embodiment of the precursor paste according to the present invention, said first material fraction has an alkali ion impurity density smaller than 9 ppm, preferably smaller than 4 ppm, preferably smaller than 2 ppm. One of the advantages may be that the functionality of the semiconductor components will not be affected on a long term scale by the composite material obtained from the precursor paste and therefore their reliability is guaranteed.

In an embodiment of the precursor paste according to the present invention, said material fraction having a volume fraction of more than 9 vol-%, preferably more than 19 vol-%, preferably more than 29 vol-%, preferably more than 34 vol-%, preferably more than 39 vol-% of the total volume of the precursor paste. One of the advantages may be that an easy and flexible adaption of the overall CTE is enabled and in particular, a low overall CTE for the composite material based on said precursor paste.

In an embodiment of the precursor paste according to the present invention, particles of said particle filler having a particle size of d99 < 70 pm, preferably < 40 pm, preferably < 25 pm, preferably < 10 pm and/or wherein said particles of said particle filler having a particle size of d95 £ 65 pm, preferably < 35 pm, preferably < 20 pm, preferably < 8 pm and/or wherein said particles of said particle filler having a particle size of dso < 30 pm, preferably < 7 pm, preferably < 3 pm. One of the advantages may be that an easy and fast homogenization of the particles in the precursor paste can be obtained, since the particles have a small specific surface and thus an only small tendency to agglomerate.

In an embodiment of the precursor paste according to the present invention, a collective of particles of said particle filler has a specific surface area, SSA, < 3 m²/g, preferably < 2 m²/g, preferably < 1 m²/g, preferably < 0,5 m²/g. This ensures a small tendency of the particles to agglomerate.

In an embodiment of the precursor paste according to the present invention, particles of said particle filler comprising carbon particles, preferably graphite particles, having a fraction of 10 weight-% or less of all particles. One of the advantages may be that a low glow loss or char yield respectively is obtained. In an embodiment of the precursor paste according to the present invention, a part of particles of said second material fraction having a coefficient of thermal expansion, CTE, of 1 ppm/K or lower, preferably having a negative coefficient of thermal expansion. One of the advantages may be that a very low overall CTE can be obtained for the composite material based on the precursor paste. Another advantage may be an enhanced flexibility in adapting the CTE to the underlying CTE of the semiconductor component being protected with said composite material based on said precursor paste.

In an embodiment of the precursor paste according to the present invention, part of said particles of said second material fraction comprising at least one of amorphous silicon dioxide or zirconium tungstate, preferably crystalline zirconium tungstate, preferably crystalline zirconium tungstate in a-, b-, and/or y-phase. One of the advantages may be that particles with a very low or even negative CTE are used enabling a very low overall CTE for the composite material based on said precursor paste.

In an embodiment of the precursor paste according to the present invention, said precursor paste having a density of below 6 g/cm³, preferably below 3 g/cm³, preferably below 2 g/cm³. One of the advantages may be that an easy handling of the precursor paste is enabled.

In an embodiment of the precursor paste according to the present invention, particles of said particle filler having a polydispersity index of more than 3.0, preferably more than 3.5, more preferably more than 4.0, preferably more than 4.5. This ensures a high filling grade.

In an embodiment of the precursor paste according to the present invention, particles of said particle filter having a cumulative distribution function of Cb, reai(d) and a deviation of a random sample of n particles defined as

with d being the particle size, D is the maximum particle size and q is a distribution coefficient, with said distribution coefficient q is between 0.2 and 0.5, preferably between 0.22 and 0.4, preferably between 0.24 and 0.38. A small deviation from the ideal Andreassen cumulative distribution function ensures a dense packaging of the particles, i.e. high volume filling grades besides their usually small CTE reducing shrinkage upon heating.

There are several ways how to design and further develop the teaching of the present invention in an advantageous way. To this end, it is to be referred to the patent claims subordinate to the independent patent claims on the one hand and to the following explanation of preferred examples of embodiments of the invention on the other hand. In connection with the explanation of the preferred embodiments of the invention, generally preferred embodiments and further developments of the teaching will be explained.

In detail, in the following table below different precursor compositions in form of pastes for obtaining a composite material according to embodiments of the present invention are shown:

In particular the pastes with past ratios

have been used for providing a composite material tested as high temperature isolating material. Test compounds have been provided according to both precursor paste ratios. These compounds have been hardened using a temperature of 150 °C, for 8 hours (first paste ratio) and for 30 minutes (second paste ratio). After hardening each compound has been divided into two parts and the two parts of each paste have been subjected to 400 °C for 30 days and 60 days respectively. After that the four parts have been examined and no color change or mechanical instability has been determined.

This paste can still be applied using a molding process like injection molding, dip coating, screen or inkjet printing, doctoring, spraying, etc.

The composition for the paste in the table above each comprise a matrix part, a solvent part, an additive part and a pigment part.

The matrix part comprises silicone resin, for instance “Silikoftal HTT”, “Silres H62C” of the company EVONIK or “Silres MK” of the company Wacker and optionally a sol- gel-hydrolysate, for instance comprising tetraethoxysilane and methyltriethoxysilane in a molar fraction of 1 :2.

The additive part comprises a defoaming agent for instance BYK 301 of the company BYK. Optionally, the additive part comprises also a rheology additive, for instance Aerosil^® R812 of the company EVONIK.

The filler part comprises fused silica particles having a dso of 20 pm of the company Denka. The pigment part comprises graphite particles and coloring pigments Black-Spinell 30 C965 of the company Shepard Pigments and further black effect pigments, for instance Osixo Black Pearl of the company Costenoble or “FlammruB” of the company Kremer Pigmente. As described for example in WO 2012/010302 A1 , which is herein incorporated by reference, graphite particles may have a grain size between 3 pm and 60 pm. If alpha boron nitride is used, the corresponding particles may have a grain size preferably between 1 pm and 100 pm, in particular between 3 pm and 20 pm.

The pigment particles may be based on one or more of the following compounds

(Cr, Fe)(Ni, Mn)-spinells (Fe, Mh)2q3 (Fe, Mn)(Fe, Mn)0₄ CuCr04

(Ni, Fe)(Cr, Fe)₂0₄ having a grain size or agglomerate size preferably a dso higher than 0.1 pm and below 3 pm, preferably below 2 pm, in particular below 1 pm.

For coloring CoAI-, CoCrAI-, CoCrMgTiZnAI-, CoNiZnTi-, NiSbTi-, CrSbTi-, and/or FeAITi-based pigments can be used. Effect pigments such as mica or glass flakes can be added as platelet-shaped pigment particles. Platelet-shaped mica is well suited for this purpose, which is coated with Si02/Ti02 or Si02/Ti02/Sn02 or Si02/Ti02/Fe203, for example. Preferably, the platelet-shaped pigments may have diameters smaller than 200 pm, preferably smaller than 100 pm, preferably smaller than 60 pm. As already mentioned, absorption pigments can also be considered as pigments, especially platelet- or rod-shaped pigments. It is also possible to use coated effect pigments and fillers can also be added, in particular: S1O2 particles, alumina particles, pyrogenic silicas, soda lime, alkali aluminosilicate or borosilicate glass spheres, hollow glass spheres, etc. as described in WO 2013/156622 A1 , which is herein incorporated by reference.

The solvent part may comprise instead of or additionally to diethylene glycol monomethylether high boiling solvents with a vapor pressure of <5 bar, preferably <1 bar, especially preferred <0.1 bar. Solvents with a boiling point of more than 120°C and an evaporation number of >10 are preferred. Preferably a solvent with a boiling point above 150 °C and a volatility >500, especially preferred with a boiling point above 200°C and a volatility >1000 is used. Such high boiling solvents are especially glycols and glycol ethers, terpenes and polyols as well as mixtures of several of these solvents. Butyl acetate, methoxybutylacetate, butyldiglycol, butyldiglycol acetate, butylglycol, butylglycol acetate, cyclohexanone, diacetone alcohol, diethylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monobutyl ether, propylene glycol monobutyl ether, propylene glycol monopropyl ether, propylene glycol monoethyl ether, ethoxypropyl acetate, hexanol, methoxypropyl acetate, monoethylene glycol, ethyl pyrroiidone, methyl pyrroiidone, dipropylene glycol dimethyl ether, propylene glycol, propylene glycol monomethyl ether, mixtures of paraffinic and naphthenic hydrocarbons, aromatic hydrocarbon mixtures, mixtures of aromatic alkylated hydrocarbons and mixtures of n-, i- and cyclo-aliphatics and/or combinations thereof may be used as solvents. In particular, polyethylene glycol ethers such as diethylene glycol monoethyl ether, tripropylene glycol monomethyl ether and terpineol and/or combinations thereof can be used as solvents. The use of solvent mixtures is also possible, where solvents can be added to the sol-gel based matrix.

The paste as precursor for the composite material is still formable or pliable usually, i.e. it may show plastic ductility and a shear-thinning behavior with viscosity values of 10¹ up to 10⁵ or even 10⁶ Pa s at shear rates <1 s^_1 (measured at room temperature) in order to ensure applicability using a molding process like injection molding, dip coating, screen or inkjet printing, doctoring, spraying, etc as mentioned above. In contrast, the final composite material behaves as a solid showing either plasticity or even a definite degree of brittleness. Plastic characteristics are in particular not desired for it.

For obtaining a composite material for encapsulating an electronic component according to an embodiment of the present invention, the following steps are performed: In a first step S1 the matrix part is provided, i.e. a silicone resin and optionally as mentioned above a sol-gel hydrolysate is added to the silicone resin.

In a further step S2 the one or more different pigments of the pigment part are added to the matrix part and mixed with high forces, e.g. mixed with a speed mixer type “DAC 400” of the company “Hauschild”.

Alternatively, to the sol-gel hydrolysate or additionally a rheology additive, for instance Aerosil^® R812 of the company EVONIK can be added. The sol-gel hydrolysate and the rheology additive may provide enhanced processing.

The resulting paste is put into a suitable mold-form and heated at a temperature above 250 °C, preferably above 300 °C for at least 20 minutes. Prior to heating, a drying process can be applied to the paste.

When a drying process is applied, volatile components are removed by physical evaporation, whereas when the paste is heated for hardening to obtain the composite material, the volatile components emerge by chemical reaction and escape from the hardening composite material.

The composite material according to embodiments of the present invention is obtained only after the thermal curing as described above. Prior to that step, reactive functional groups present in the sol-gel hydrolysate, silicone resin or polysilsesquioxane are converted in a chemical reaction. Depending on the nature of these reactions, e.g. an addition or condensation reaction, small molecular units may be formed as by-products, which escape from the composition into the surrounding atmosphere in the course of thermal stress and lead to a certain degree of weight loss. The same applies to solvents used in the preparation of the pasty precursor, which may or may not be the case: These also escape from the resulting paste during the final temperature treatment step.

The composite material obtained after the thermal curing step is no longer plastically deformable and provides a protective function. It may however possess more or less elastic properties. Depending on the formulation of the precursor, it may even be brittle.

To measure the coefficient of thermal expansion, the method of optical dilatometry is used. In general, dilatometry is a method of thermal analysis and is used to measure the thermal expansion of materials, e.g. metals, glass and building materials etc. when the temperature is increased. In this context, the special case of optical dilatometry measurements are performed without contact with the sample. Dimensional changes in the sub-pm-range can be determined. A high-resolution CCD-camera allows a visual real-time analysis of the sample expansion either as a single image or as a video sequence. The contactless measurement of the optical dilatometers simplifies the sample preparation, because the parallelism between the two end faces of the sample and the shape of the sample are not as important as in mechanical dilatometry. In an optical dilatometer, the sample is compared with a reference during the measurement. The result is the difference in strain between the two samples. In this way, the influence of the sample holder is eliminated.

In detail, to measure the CTE of the composite materials shown in the table above, a heating microscope of type “EMI III” of the company Hesse Instruments is used. This heating microscope comprises an optical bench with lamp, stands and camera, a furnace system with furnace control unit, furnace and transformer and a measuring station computer for analysis of a sample of the composite material. Basis for obtaining the CTE using said heating microscope are the norms DIN 51730:2007, ISO 540:2008-06, CEN/TS 15370-1 :2006 and CEN/TR 15404:2006.

Different samples have been examined and a CTE of less than +50 ppm/K, in particular for a number of samples a CTE of less than +30 ppm/K was obtained.

In summary, embodiments of the present invention may provide or enable a composite material preferably having the following properties:

Thermal stability: -60 °C to 300 °C or even up to 400 °C.

Low load on alpha emitters (<0.1 counts/cm²/h).

Low mobility of certain ions: e.g. alkalis < 10 ppm, halogens < 10ppm,

Cu, Fe < 10ppm. Thermal conductivity >0.2 W/mK, preferably >0.5 W/mK, preferably >1.0 W/mK.

Resistance to steam: 85h at 85°C, resistant to acids, bases, alcohols, mineral oils.

Electrical insulation: about 40 kV/mm.

Low density: < 2.8 g/cm.

Primary particle size of fillers: d99 < 100 pm, preferably d99 < 70 pm, preferably d99 < 50 pm, preferably d99 < 25 pm, preferably d99 < 10 pm, preferably d99 < 5 pm.

Particle shape: nearly, preferably ideally, spherical.

The composite material according to embodiments of the present invention is highly resistant to acids, bases and aqueous media as well as having good climatic resistance, e.g. 85 % relative humidity at 85 °C. It is resistant to the effects of UV radiation and has an enhanced flame behavior. Due to the composition of the particle filler fraction, it can be modified and adapted in many properties, e.g.:

High UV absorption, thus being able to protect underlying components. Adjustment of the dielectric properties.

Adjustment of the thermal conductivity.

Setting of the electromagnetic shielding.

The processability of the composite material according to embodiments of the present invention can also be adjusted over a wide range, e.g. application as an injection moldable compound.

Many modifications and other embodiments of the invention set forth herein will come to mind to the one skilled in the art to which the invention pertains having the benefit of the teachings presented in the foregoing description. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

C l a i m s

1. Composite material for protecting electronic components, comprising at least a first material fraction and a second material fraction, wherein said first material fraction comprising at least one hybrid polymer, wherein said at least one hybrid polymer comprising at least one of sol-Gel compound having a total organic carbon, TOC, content below 75 weight-%, and above 0,01 weight-%, preferably above 10 weight-%, preferably above 20 weight-%,

Silicone resin and/or Polysilsesquioxane, and/or combinations thereof, and said second material fraction comprising a particle filler.

2. Composite material according to claim 1 , wherein particles of said particle filler have a coefficient of thermal expansion, CTE, of +20 ppm/K or lower, preferably of +15 ppm/K or lower, preferably of +10 ppm/K or lower, preferably of +5 ppm/K or lower, preferably of +2 ppm/K or lower and higher than +0,01 ppm/K, preferably higher than +0,1 ppm/K, preferably higher than +1 ,0 ppm/K.

3. Composite material according to claim 1 or 2, wherein said first material fraction has an alkali ion impurity density smaller than 10 ppm, preferably smaller than 5 ppm, preferably smaller than 3 ppm, and higher than 0,01 ppm, preferably higher than 0,1 ppm, preferably higher than 1 ppm.

4. Composite material according to one of the claims 1-3, wherein said composite material has an ignition loss smaller than 30 weight-%, preferably smaller than 25 weight-%, preferably smaller than 20 weight-%, and higher than 1 weight- %, preferably higher than 3 weight-%, preferably higher than 5 weight-%, preferably higher than 10 weight-% for temperatures below 400 °C, preferably below 450 °C, and above 100 °C. 5. Composite material according to one of the claims 1-4, wherein particles of said particle filler having a particle size of d99 < 70 pm, preferably < 40 pm, preferably < 25 pm, preferably < 10 pm and d99 > 0.5 pm, preferably ³ 1 pm, preferably ³ 2 pm and/or wherein said particles of said particle filler having a particle size of d95 < 65 pm, preferably < 35 pm, preferably < 20 pm, preferably < 8 pm and d95 ³ 0.5 pm, preferably > 1 pm, preferably > 2 pm and/or wherein said particles of said particle filler having a particle size of dso < 30 pm, preferably < 7 pm, preferably < 3 pm and dso ³ 0.

5 pm, preferably > 1 pm, preferably > 2 pm.

6. Composite material according to one of the claims 1-5, wherein a collective of particles of said particle filler has a specific surface area, SSA, < 3 m²/g, preferably < 2 m²/g, preferably < 1 m²/g, preferably < 0,5 m²/g and above 0,05 m²/g, preferably above 0,1 m²/g.

7. Composite material according to one of the claims 1-6, wherein particles of said particle filler having a polydispersity index of more than 3.0, preferably more than 3.5, more preferably more than 4.0, preferably more than 4.5 and below 10.0, preferably below 8.0.

8. Composite material according to one of the claims 1-7, wherein particles of said particle filter having a cumulative distribution function of Cb, reai(d) and a deviation of a random sample of n particles defined as

with d being the particle size, D is the maximum particle size and q is a distribution coefficient, with said distribution coefficient q is between 0.2 and 0.5, preferably between 0.22 and 0.4, preferably between 0.24 and 0.38.

9. Composite material according to one of the claims 1-8, wherein said composite material providing a dielectric strength is higher than 20 kV/mm, preferably higher than 35 kV/mm, preferably higher than 40 kV/mm.

10. Composite material according to claim 9, wherein particles of said particle filler comprising carbon particles, preferably graphite particles, having a fraction of 10 weight-% or less of all particles.

11. Composite material according to one of the claims 1-10, wherein a part of particles of said second material fraction having a coefficient of thermal expansion, CTE, of 1 ppm/K or lower, preferably having a negative coefficient of thermal expansion.

12. Composite material according to claim 11 , wherein said particles comprising at least one of amorphous silicon dioxide or zirconium tungstate, preferably crystalline zirconium tungstate, preferably crystalline zirconium tungstate in a-, b-, and/or y-phase.

13. Composite material according to one of the claims 1-12, wherein said second material fraction having a volume fraction of more than 10 vol-%, preferably more than 20 vol-%, preferably more than 30 vol-%, preferably more than 35 vol-%, preferably more than 40 vol-% and below 80 vol-%, preferably below 70 vol-% of the total volume of the composite material.

14. Composite material according to one of the claims 1-13, wherein said composite material having a coefficient of thermal expansion, CTE, of +50 ppm/K or lower, preferably of +30 ppm/K or lower and above +1 ppm/K, preferably between +1 and +20 ppm/K, preferably between +2 and +18 ppm/K, preferably between +2 and +16 ppm/K, preferably between +4 and +16 ppm/K or between +2 and +5 ppm/K.

15. Composite material according to one of the claims 1-14, wherein said composite material having a density of below 6 g/cm³, preferably below 3 g/cm³, preferably below 2 g/cm³ and above 1 g/cm³, preferably 1 .5 g/cm³.

16. Encapsulating, moulding, potting, underfill, bonding and/or coating mass comprising a composite material according to one of the claims 1-15.

17. Electronic and/or semiconductor component comprising a composite material according to one of the claims 1-15 and/or a mass according to claim 16.

18. Use of a composite material according to one of the claims 1-15 for encapsulating, moulding, potting, underfill, bonding and/or coating of an electronic and/or semiconductor component, preferably an RFID-chip, preferably wherein said composite material is suitable for forming electrical insulators, preferably wherein said composite material is suitable for use as electrical insulator in electrical feedthroughs, preferably wherein said electrical insulator is used as an insulation barrier for electrical feedthroughs configured for use in harsh environments.

19. Precursor paste, preferably in form of a spreadable paste, for a composite material according to one of the claims 1-15 for protecting electronic components, preferably an electrically insulating composite material, said precursor paste comprising at least a first material fraction and a second material fraction, wherein said first material fraction comprising at least one chemically reactive hybrid polymer, wherein said at least one chemically reactive hybrid polymer comprising at least one of a reactive sol-gel compound having a total organic carbon, TOC, content below 85 weight-%, and above 0,01 weight-%, preferably above 10 weight-%, preferably above 20 weight-%, a reactive or inert silicone resin and/or reactive Polysilsesquioxane, and/or combinations thereof, and said second material fraction comprising a particle filler.

20. Precursor paste according to claim 19, wherein said first material fraction has an alkali ion impurity density smaller than 9 ppm, preferably smaller than 4 ppm, preferably smaller than 2 ppm.

21 Precursor paste according to one of the claims 19-20, wherein said second material fraction having a volume fraction of more than 9 vol-%, preferably more than 19 vol-%, preferably more than 29 vol-%, preferably more than 34 vol-%, preferably more than 39 vol-% of the total volume of the precursor paste.

22. Precursor paste according to one of the claims 19-21 , wherein particles of said particle filler having a particle size of d99 < 70 pm, preferably < 40 pm, preferably < 25 pm, preferably < 10 pm and/or wherein said particles of said particle filler having a particle size of d95 < 65 pm, preferably < 35 pm, preferably < 20 pm, preferably < 8 pm and/or wherein said particles of said particle filler having a particle size of dso

< 30 pm, preferably < 7 pm, preferably < 3 pm.

23. Precursor paste according to one of the claims 19-22, wherein a collective of particles of said particle filler has a specific surface area, SSA, < 3 m²/g, preferably

< 2 m²/g, preferably < 1 m²/g, preferably < 0,5 m²/g.

24. Precursor paste according to one of the claims 19-23, wherein particles of said particle filler comprising carbon particles, preferably graphite particles, having a fraction of 10 weight-% or less of all particles.

25. Precursor paste according to one of the claims 19-24, wherein a part of particles of said second material fraction having a coefficient of thermal expansion, CTE, of 1 ppm/K or lower, preferably having a negative coefficient of thermal expansion.

26. Precursor paste according to claim 25, wherein part of said particles of said second material fraction comprising at least one of amorphous silicon dioxide or zirconium tungstate, preferably crystalline zirconium tungstate, preferably crystalline zirconium tungstate in a-, b-, and/or y-phase.

27. Precursor paste according to one of the claims 19-26, wherein said precursor paste having a density of below 6 g/cm³, preferably below 3 g/cm³, preferably below 2 g/cm³.

28. Precursor paste according to one of the claims 19-27, wherein particles of said particle filler having a polydispersity index of more than 3.0, preferably more than 3.5, more preferably more than 4.0, preferably more than 4.5.

29. Precursor paste according to one of the claims 19-28, wherein particles of said particle filter having a cumulative distribution function of Cb, reai(d) and a deviation of a random sample of n particles defined as

of smaller than 0,030, preferably smaller than 0,020, more preferably smaller than 0,015 from the ideal Andreasson cumulative distribution function Cb, Andreassen, (d), said ideal Andreasson cumulative distribution function Cb, Andreassen, (d), fulfilling ( (-d\ Q ₌ )^q with d being the particle size, D is the maximum particle size and q is a distribution coefficient, with said distribution coefficient q is between 0.2 and 0.5, preferably between 0.22 and 0.4, preferably between 0.24 and 0.38.

30. Encapsulating, moulding, potting, underfill, bonding and/or coating mass comprising a precursor paste according to one of the claims 19-29.

31 . Use of a precursor paste according to one of the claims 19-29 for providing a composite material for encapsulating, moulding, potting, underfill, bonding and/or coating of an electronic and/or semiconductor component, preferably an RFID-chip, preferably wherein said composite material is suitable for forming electrical insulators, preferably wherein said composite material is suitable for use as electrical insulator in electrical feedthroughs, preferably wherein said electrical insulator is used as an insulation barrier for electrical feedthroughs configured for use in harsh environments.