Thermally Conductive Material for Electronic and/or Electrical Components, and Use Thereof

Abstract

A thermally conductive and electrically insulating material, especially a paste, for mounting electrical and/or electronic components in housings and/or on cooling elements. The material is free of silicons and has a high filling ratio with moderate viscosity.

Description

The invention is described in more detail below with reference to an example:

The substances listed in the table below are combined, mixed in a corresponding apparatus and degassed in the vacuum:

Quantity Composition
32.0 g   Cycloaliphatic epoxy resin
14.4 g   Epoxydized soya bean oil
3.20 g   Polyvinyl butyral
97.4 g   Trifunctional polyester polyol
2.35 g   Triaryl sulfonium hexafluoroantimonate
         (photoinitiator)
0.095 g  Isopropyl thioxanthone
0.30 g   Defoamer
340.97   Quartz
85.24    Quartz
1.5      Soda lime glass

The polyvinyl butyral products can vary both in respect of the molar mass as well as in respect of their acetalization degree and finally in respect of their proportion of hydroxy groups.

The initial viscosity of the heat-conductive material should be as small as possible, between 50 and 250 Pas for instance (measured with a plate or cone viscosimeter).

After a few seconds of radiation, the viscosity of 80 increases to more than 500 Pas, so that the mounting can be carried out during the next hour or somewhat longer, without a complete curing process taking place.

The thermal conductivity of the material is significantly dependent on the filling degree and on the filler material, for instance a thermal conductivity of at least 0.7 W/mK can be reached with a filling degree of 75 percent by weight (silica dust). Higher filling degrees and more powerful thermally-conductive filler material produce a higher thermal conductivity of the material.

The following advantages are achieved for the first time by the inventive material:

• • the material can be easily applied, because it has a moderate initial viscosity suitable for this purpose,
  • surplus material can be easily removed again
  • mechanical unevenesses are balanced and holes filled
  • no silicon content, therefore no unwanted byproducts
  • a simple disassembly for repair purposes, because the material only exhibits low adhesion
  • low thermal contact resistance, because the thermally-conductive material can be applied over a large area over the entire device and thus ensures optimum heat dissipation
  • only one material is necessary, which covers both the conductor board or printed circuit board as well as the assembly parts located thereupon
  • less cost-intensive curing conditions (radiation with UV light)
  • material is cross-linked when in a completely cured state, therefore enabling components and printed circuit boards embedded in the material to withstand high vibration loads.
  • possibility of double-sided SMD equipping without additional housing

The present invention relates to a material, in particular a paste, for mounting electrical and/or electronic components in housings and/on cooling elements, which is thermally conductive and electrically insulating. This material which is being presented for the first time is free of silicons, exhibits a high thermal conductivity with a high filling degree and moderate viscosity. The end state is achieved after UV activation during thermal post curing if required.

Claims

1. A thermally-conductive and electrically insulating material, comprising at least the following components: a) a trifunctional or higher functional polyolb) an epoxy componentc) a photoinitiator system andd) 65 to 80% percent by weight of a thermally-conductive filler material

2. The material as claimed in claim 1, with the epoxy component being bifunctional.

3. The material as claimed in claim 1, with more hydroxy groups being contained in the prepolymer initial components, in respect of functional groups, than epoxy groups.

4. The material as claimed in claim 1, with the polyol being a polyvinyl butyral and/or a trifunctional polyester polyol.

5. The material as claimed in claim 1, with the polyol being a polyvinyl butyral and the acetalization degree of the polyvinyl butyral being more than 75% and/or the molar mass of the trifunctional polyester polyol component being more than 800 g/mol.

6. The material as claimed in claim 1, with the photoinitiator being a type of triaryl sufonium salt.

7. The material as claimed in claim 1, with the filler material not exhibiting any alkali character, but instead a neutral or even an acid character.

8. (canceled)

9. The material as claimed in claim 2, with more hydroxy groups being contained in the prepolymer initial components, in respect of functional groups, than epoxy groups.