DE202009017662U1 - Thermal paste High temperature range, non-conductive based on natural stone flour, oil emulsion and various additives - Google Patents

Abstract

Thermal paste, characterized in that it consists of 50 to 80% by weight of a filler of natural stone powder in particle sizes between 10 to 30 nm and 20 to 50% by weight of a matrix material based on a silicone oil emulsion.

Description

The The present invention relates to a thermal grease, in particular a thermally conductive paste made of carbon with biologically neutral Matrix. The paste is used to make a heat conductive Connection between an electronic component, such. B. one Computer chip, or an electrical component, such as a power semiconductor, and a cooling system used.

electrical Devices produce from a part of them Electric energy loss heat, which is used to prevent Failures of the electronic components dissipated must become.

Generally Devices are known for cooling of electrical Components by combinations of heat sinks (passive cooling) and suitable fans.

But also in many other everyday electrical appliances Demands such as in the automotive electronics, washing machines, dishwashers, appliances with control electronics such as drills, etc., radio, TV, machine controls, Voltage regulator in the power plant, wind generators or solar systems electrical components must be cooled. Also In these cases, thermal grease is compensated of unevenness of the surfaces between a semiconductor or power semiconductors and heat sink or heat transport system used.

In order to the cooling must be able to be carried out effectively the connection of the electronic component to be cooled to the cooling system a high thermal conductivity have. In addition, certain, existing in each electronic module, Compensate for manufacturing tolerances. When mounting chips with the help of so-called circuit connection technology with controlled Connection occurs due to variations in size and shape used for connecting a chip to a circuit board Lötknötchengruppen considerable fluctuations the chip height and tilt with respect to the circuit board on. The electrical connections of the chips are very fragile, and the thermally conductive connection needs a certain degree of different movement of the individual, an electrical system group allow forming chips. Likewise, manufacturer tolerances lead to different distances between chip and cooling system. Additional there are topographical Unevenness, such as engraved in electronic components License plate to bridge. Similar requirements There are also other components to be cooled.

The Combination of geometric variations and tolerances is the goal contrary, a good heat conduction by means of a very thin Layer paste between specific components and the cooling system to reach. Despite the difficulties encountered, one is good heat output still achievable when a paste with good thermal conductivity is used. A Such paste is generally applied to the surface at room temperature applied to the electronic component to be cooled, whereupon the cooling system is put on.

Of the Use of known, conventional thermal compounds has led to moderately good heat transfer. A commonly used paste contains a Mixture of zinc oxide in mineral oil or silicone oil. Such Pastes have a thermal conductivity upper limit from 1 W / mK. Contains a slightly improved thermal grease as a thermally conductive component alumina and has a maximum thermal conductivity of 2 W / mK on. Such pastes with low thermal conductivity However, these are the requirements for new computer generations with even higher integration density and increased at the same time Processor performance or of modern power electronics in increasing Measures not grown.

In US.6.651.736 was presented a thermal compound based on cut carbon fibers and silicone oil and other additives. Although carbon fibers have high thermal conductivity along the fiber, transferring this property to a three-dimensional matrix, such as a paste, is difficult because the fibers have a hard surface and heat output is limited to only individual points of contact between the fibers. If one tries to compensate for this lag by increasing the proportion of fiber in the matrix, the paste becomes too firm, because the fibers, similar to the rods in the Mikado, form a rigid skeleton in whose interstices, for example, the oil rests. Thus, in US.6.651.736 the proportion of carbon fibers is limited to 10 to 20% and the maximum thermal conductivity achieved is 4 W / mK. Moreover, due to the dimensions of the carbon fibers, which are about 10 mu thick and 100 mu long, it is difficult to compensate for smaller topographic bumps on the electronic components. In the worst case, the fibers may get caught and damage the electronic component. The production of finely cut carbon fibers is also very expensive.

In the utility model DE 20 2004 017 33 U1 2005.03.249 a thermal grease based on graphite, natural graphite or synthetic graphite is presented, whose grain size is less than 10 mu, and enriched with additives such as carbon fibers, carbon nanotubes and / or metal or Karamikpartikeln. It should be noted that it has been demonstrated in the meantime that these additives When penetrating the body, they can penetrate the cell membranes and cause serious damage to the DNA. This is remedied according to the invention, in which deliberately dispensed with such additives. Furthermore, these additives prevent the biodegradability of the thermal compound, which is no longer appropriate in the light of current environmental legislation. In addition, deliberately the addition of animal by-products (wax) was omitted, since there is currently no reliable knowledge about the compatibility of the degradation products that arise under high temperatures in connection with electronic components.

The thermal conductivity of the utility model DE 20 2004 017 339 U1 2005.03.24 is characterized in that a value of 5-9 W / mK is achieved; this value can be increased according to the invention by the use of other additives to 10 to 15 W / mK, which causes a significantly lower load on the electronic components by temperature. Incidentally, the set viscosity of the above-mentioned thermal paste changes below DE 20 2004 017 339 U1 Greater than 250 ° C in such a way that the paste begins to smoke and thus begins to shrink spatially. As a result, the components are bonded, which does not detract from the heat conduction, but which leads to overheating problems in various applications. This has been remedied according to the invention in the present thermal paste for the high temperature range, so that the paste undergoes a viscosity loss only from 300 ° C.

It There are also commercially available thermal transfer pastes containing particles made of metals that have a particularly high thermal conductivity have. These include mainly copper, aluminum and Silver. Silver-based pastes achieve thermal conductivities of up to 9 W / mK, but are very expensive and have an allergenic Potential. In addition, the long-term effect of metal-based Pasts controversial, because these metals have a certain ductility have, ie at elevated temperatures and pressure flow, and thus the heat-conducting contact will decrease over time can. So they are not usable for devices, which are used in the food sector, as possible here toxic emissions occur.

The Object of the present invention is to provide a thermal paste to provide, which by their thermal conductivity from more than 10 W / mK also the requirements for modern Electronics met, the viscosity set also in the high temperature range and thus long-term stable is inexpensive, as well as non-toxic and biologically harmless is.

These The object is achieved according to the invention that a thermal compound is provided, which on Base of natural stone flour and synthetic silicone oil as well Stäke, water and gelling agent is produced.

Natural stone powder biologically inert and can be degraded.

Of the Natural stone can be applied to grains by various grinding methods from 10 to 30 nanometers. This small grain size is necessary for the paste according to the invention, to compensate for topographic bumps on the electronic components.

ever The particle size makes it possible, above all, to compressibility modify the paste to some extent.

Of the Total content of natural stone flour in the paste can be between 50 to 80% by weight.

The achieved with a paste according to the invention thermal conductivities are between 10 and 15 W / mK and thus meet the requirements of the most modern Electronics and surpass the value of the most conductive commercially available thermal paste. optional can a thermal paste according to the invention still additives such. B. degreased soot be buried. These Additives can improve the thermal conductivity and processability of the paste even further.

When Matrix materials come for the invention Thermal paste preferably biologically neutral silicone oils for use. These include silicone oil emulsions based on synthetic silicone oils and starch, Water and gelling agent. Depending on the desired consistency the thermal compound can be the matrix materials be combined with each other. These can also be different Contain additives that the processability and / or durability improve the paste.

invention Furthermore, pastes can be prepared without residue by means of suitable Cleaning agents of electronic components or other substrates remove.

The finished pastes can be prepared by conventional methods in the conventional Containers for thermal compounds, such as about plastic syringes, cans, cartridges, buckets and suitable Pack barrels.

The Thermal compounds prepared in this way were successfully used for the cooling of various electronic components in computers and other electronic devices.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - US 6651736 [0008, 0008]
• - DE 202004017339 U1 [0009, 0010, 0010]

Claims (11)

Thermal paste, characterized in that it consists of 50 to 80% by weight of a filler of natural stone powder in particle sizes between 10 to 30 nm and 20 to 50% by weight of a matrix material based on a silicone oil emulsion. Thermal compound according to claim (1), characterized in that it allows a temperature stability> 275 ° C. Thermal compound according to claim (1) and (2), characterized in that they have a thermal conductivity from 10 to 15 W / mK. Thermal paste according to claims (1), (2) and (3), characterized in that they are non-toxic, not containing heavy metals and biologically harmless. Thermal paste according to claims (1), (2), (3) and (4), characterized in that they are not toxic Emissions at the workplace or after processing. Thermal paste according to claims (1), (2), (3), (4) and (5), characterized in that they are without Personal protective equipment will be processed can and does not place any special requirements on the work sheet and harmless if inadvertently consumed Body and life is. Thermal paste according to claims (1), (2), (3), (4), (5) and (6), characterized in that they is not electrically conductive. Filler according to claim (1), characterized in that it consists of natural stone flour or mixtures different natural stone types. Filler according to claim (8), characterized in that it has a mean grain size of 10-30 nm. Matrix material according to claim (1), characterized in that it is a silicone oil emulsion which is based on silicone oils of synthetic origin with a purity of "chemically pure". Matrix material according to claim (10), characterized in that the emulsion further additives such as starch, water and gelling agent.