阅读说明：本技术 导热性片材 (Thermal conductive sheet ) 是由 山县利贵 和田光祐 金子政秀 于 2018-08-27 设计创作，主要内容包括：提供导热性优异的片材,特别是提供适合作为电子部件用散热构件的导热性片材。一种导热性片材,其特征在于,其是将鳞片状氮化硼的一次粒子聚集成的二次聚集粒子分散于热固性树脂中而形成的导热性片材,其中,前述二次聚集粒子具有50μm以上且120μm以下的平均粒径、51％以上且60％以下的孔隙率,累积破坏率63.2％时的粒子强度为0.2MPa以上且2.0MPa以下,前述导热性片材中的前述二次聚集粒子的填充率为50体积％以上且70体积％以下。(Disclosed is a sheet having excellent thermal conductivity, particularly a thermal conductive sheet suitable as a heat-dissipating member for electronic components. A thermal conductive sheet comprising a thermosetting resin and secondary aggregated particles obtained by aggregating primary particles of scaly boron nitride, wherein the secondary aggregated particles have an average particle diameter of 50 to 120 [ mu ] m inclusive and a porosity of 51 to 60% inclusive, a particle strength at a cumulative failure rate of 63.2% is 0.2 to 2.0MPa inclusive, and a filling rate of the secondary aggregated particles in the thermal conductive sheet is 50 to 70% by volume.)

1. A thermal conductive sheet comprising a thermosetting resin and secondary aggregated particles obtained by aggregating primary particles of scaly boron nitride, wherein the secondary aggregated particles have an average particle diameter of 50 to 120 [ mu ] m and a porosity of 51 to 60%, a particle strength at a cumulative destruction rate of 63.2% is 0.2 to 2.0MPa, and a filling rate of the secondary aggregated particles in the thermal conductive sheet is 50 to 70 vol%.

2. A heat dissipating member comprising the thermal conductive sheet according to claim 1.

Technical Field

The present invention relates to a sheet having excellent thermal conductivity and use thereof, and more particularly to a thermal conductive sheet which can be mounted on an electronic device without damaging a heat-generating electronic component such as a power device, a transistor, a thyristor, or a CPU (central processing unit) when used as a heat-dissipating member for an electronic component.

Background

In heat-generating electronic components such as power devices, transistors, thyristors, and CPUs, how to remove heat generated during use is an important issue. Conventionally, as such a heat removal method, a heat-generating electronic component is generally mounted on a heat sink or a metal plate via an electrically insulating heat conductive sheet, and heat is dissipated, and as the heat conductive sheet, a heat conductive filler dispersed in silicone rubber is used.

In recent years, as the circuit in an electronic component is highly integrated, the amount of heat generated is also increased, and a material having higher thermal conductivity than that of the conventional one is required. In order to improve the thermal conductivity of a thermally conductive material, it has been a common method to incorporate a filler exhibiting high thermal conductivity, such as alumina powder, boron nitride powder, or aluminum nitride powder, into an organic resin. In addition, a method of filling scaly hexagonal boron nitride powder having poor filling properties into an organic resin in the form of secondary aggregated particles to achieve high thermal conductivity has been carried out. (patent documents 1 to 4). The orientation of hexagonal boron nitride powder is described in patent documents 5 and 6.

Disclosure of Invention

Problems to be solved by the invention

However, it has been difficult to obtain a sheet-like member having excellent thermal conductivity. High thermal conductive members using BN moldings are known as in patent document 7, but they are not suitable for use in heat dissipation of curved shapes or for use under strong fastening torque because of insufficient flexibility as members. In addition, it is not practical to reduce the thickness of the member to 300 μm or less. Further, for example, patent document 8 proposes a sheet having high thermal conductivity, but the BN aggregate particles used therein have a porosity of 50% or less, and the thermal conductivity can be about 6W/(m · K).

Means for solving the problems

The purpose of the present invention is to provide a sheet having excellent thermal conductivity. In particular, a thermal conductive sheet suitable as a heat dissipating member for electronic parts is provided.

In order to solve the above problems, embodiments of the present invention may provide the following.

(1) A thermal conductive sheet comprising a thermosetting resin and secondary aggregated particles obtained by aggregating primary particles of scaly boron nitride, wherein the secondary aggregated particles have an average particle diameter of 50 to 120 [ mu ] m and a porosity of 51 to 60%, a particle strength at a cumulative destruction rate of 63.2% is 0.2 to 2.0MPa, and a filling rate of the secondary aggregated particles in the thermal conductive sheet is 50 to 70 vol%.

(2) A heat dissipating member comprising the thermal conductive sheet according to the above (1).

ADVANTAGEOUS EFFECTS OF INVENTION

According to an embodiment of the present invention, a sheet exhibiting high thermal conductivity may be provided.

Detailed Description

The present invention will be described in detail below.

The secondary aggregated particles obtained by aggregating the primary particles of the flaky boron nitride used in the embodiment of the present invention must have an average particle diameter of 50 to 120 μm, and the average particle diameter is preferably in the range of 70 to 90 μm. If the average particle diameter is larger than 120 μm, the gap between particles becomes large when the particles come into contact with each other, and the thermal conductivity is lowered, and it becomes difficult to obtain a thin sheet. Conversely, if the average particle diameter is less than 50 μm, the filling property of the secondary agglomerate particles in the thermosetting resin is deteriorated, and the thermal conductivity is lowered.

Further, the thermal conductive sheet according to the embodiment of the present invention may contain conductive powder such as aluminum, copper, silver, carbon fiber, or carbon nanotube in a range where heat dissipation is not impaired.

The porosity of the secondary aggregated particles obtained by aggregating the primary particles of the scaly boron nitride used in the embodiment of the present invention is required to be 51 to 60%, and the porosity is preferably in the range of 53 to 57%. If the porosity is more than 60%, the strength of the particles becomes low, and the sheet formation becomes difficult. Conversely, if the porosity is less than 51%, the filling property of the secondary aggregated particles in the thermosetting resin is deteriorated, and the thermal conductivity is lowered. By setting the porosity of the BN aggregate particles to 51 to 60%, the filling effect in the resin is improved to such an extent that cannot be obtained in the prior art, and high thermal conductivity can be achieved.

The secondary aggregated particles obtained by aggregating the primary particles of the scaly boron nitride used in the embodiment of the present invention need to have a particle strength of 0.2 to 2.0M Pa at a cumulative failure rate of 63.2%, more preferably 0.3 to 1.8MPa, and still more preferably 0.3 to 1.5 MPa. If the particle strength at a cumulative failure rate of 63.2% is greater than 2.0MPa, deformation due to secondary aggregation does not occur, and the particles are in point contact instead of in surface contact, resulting in a decrease in the thermal conductivity of the thermal conductive sheet. Conversely, if the particle strength at a cumulative failure rate of 63.2% is less than 0.2MPa, the secondary aggregated particles are easily broken, the anisotropy increases, and the thermal conductivity of the thermal conductive sheet decreases.

The filling rate of the secondary aggregated particles in the thermal conductive sheet according to the embodiment of the present invention is 50 to 70 vol%, and particularly preferably 55 to 65 vol%, based on the total volume. When the filling ratio of the secondary aggregated particles is less than 50 vol%, the thermal conductivity of the thermal conductive sheet becomes insufficient, and when it exceeds 70 vol%, the filling of the thermal conductive filler becomes difficult.

The secondary aggregated particles having a specific average particle diameter, porosity, and particle strength combined as described above have excellent characteristics from the viewpoints of thermal conductivity and physical properties in the production of a sheet. Further, by preparing a thermal conductive sheet using the specific secondary aggregated particles at a filling rate in the range of 50% by volume or more and 70% by volume or less, it is possible to achieve an extremely high thermal conductivity effect which cannot be achieved by the conventional techniques.

The average particle diameter in the present specification is measured by using a laser diffraction particle size distribution measuring apparatus SALD-200 manufactured by Shimadzu corporation. For the evaluation sample, 50cc of pure water and 5g of the measured thermal conductive powder were added to a glass beaker, stirred with a spatula, and then subjected to a dispersion treatment for 10 minutes with an ultrasonic cleaner. The solution of the dispersed powder of the heat conductive material is added dropwise to the sampling portion of the apparatus with a dropper until the solution becomes stable to measurable absorbance. Thus, the measurement was performed at the time when the absorbance was stabilized. In the laser diffraction particle size distribution measuring apparatus, the particle size distribution is calculated from data of the light intensity distribution of diffracted/scattered light of particles detected by a sensor. The average particle diameter is determined by multiplying the value of the measured particle diameter by the relative particle amount (% difference) and dividing by the total amount of the relative particle amount (100%). The average particle diameter is an average diameter of the particles.

The porosity of the secondary aggregated particles in which the primary particles of the scaly boron nitride are aggregated in the present specification means a value obtained by measurement with a mercury intrusion porosimeter. The porosity is throughThe pore volume was measured by a mercury porosimeter. The pore volume using a mercury porosimeter can be measured, for example, by using "PASCAL 140-440" (manufactured by FISONSINSTROMENTS CORPORATION). The principle of this measurement is based on the formula ∈ g ═ Vg/(Vg +1/ρ t) × 100. In the formula,. epsilon.g represents the porosity (%) of the boron nitride particles, and Vg represents the value (cm) obtained by subtracting the voids between the particles from the pore volume³G) (/ g), ρ t is the density of hexagonal boron nitride particles of the primary particles 2.34 (g/cm)³)。

In the present specification, the particle strength (single grain crushing strength) at a cumulative failure rate of 63.2% of secondary aggregated particles in which primary particles of scaly boron nitride are aggregated is as defined in JIS R1639-5: 2007. Here, "63.2%" refers to a case where the ratio of JIS R1639-5: JIS R1625 cited in 2007: the values of lnln {1/(1-f (t)) } ═ 0 in the Weibull (Weibull) distribution function taught in 2010 are known, and are values based on the number of particles.

Among the thermosetting resins that can be used in the embodiment of the present invention, a kneading type silicone (millable type silicone) is typical, but in general, it is often difficult to exhibit the desired flexibility, and therefore, an addition reaction type silicone is preferable in order to exhibit high flexibility. Specific examples of the addition reaction type liquid silicone include a one-liquid reaction type organopolysiloxane having both a vinyl group and an H — Si group in one molecule, and a two-liquid type silicone of an organopolysiloxane having a vinyl group at a terminal or in a side chain and an organopolysiloxane having 2 or more H-Si groups at a terminal or in a side chain. For example, the product is "ERASTOSIL LR 3303-20/A/B" manufactured by Ltd.

The addition reaction type liquid silicone that can be used in the embodiment of the present invention may further contain a reaction retarder such as acetyl alcohol and maleate, a thickener such as AEROSIL having a particle size of ten to several hundred μm, silicone powder, a flame retardant, a pigment, and the like.

The thermal conductive sheet according to the embodiment of the present invention can be reduced in thickness to 200 μm as long as desired, and can have flexibility, so that the degree of freedom in the mounting method can be improved.

The thermal conductive sheet according to the embodiment of the present invention may be used in combination with a glass cloth as a reinforcing material. Examples of the glass cloth include a raw cloth obtained by weaving glass, and a treated cloth subjected to heat washing and coupling agent treatment, and the glass cloth is, for example, under the trade name "H25F 104" manufactured by Unitika ltd.

In the method for producing a thermal conductive sheet of the present invention, the aggregated powder of boron nitride powder is added to the addition reaction type liquid silicone, and the mixture is mixed using "desmearing taro" manufactured by THINKY CORPORATION as a rotation/revolution mixer, whereby the aggregated powder of boron nitride powder can be produced without being crushed.