Adhesive Composition And Use Thereof In Electronics

Abstract

An adhesive composition includes a polymer, inorganic fillers, and at least one organic solvent. The polymer is at least one preceramic polymer, advantageously based on silicon. The fillers include one or a plurality of thermally conductive and electrically insulating inorganic fillers.

Claims

1. An adhesive composition comprising a polymer, inorganic fillers, and at least one organic solvent, wherein: the polymer is at least one preceramic polymer, and the fillers comprise one or a plurality of types of thermally conductive and electrically insulating inorganic fillers.

2. The adhesive composition of claim 1, wherein the preceramic polymer comprises at least one of the following: polysiloxanes, polysilsesquioxanes, polycarbosiloxanes, polyborosilanes, polyborosiloxanes, polysilazanes, poly-silsesquiazanes, polyborosilazanes, polycarbosilanes, polysilylcarbodiimides, and polysilsesquicarbodiimides.

3. The adhesive composition of claim 1, wherein the preceramic polymer represents from 15 to 50 wt. % with respect to a total weight of the adhesive composition.

4. The adhesive composition of claim 1, wherein the inorganic fillers comprise at least one of the following: AlN; Al.sub.2O.sub.3; hBN; silicon nitride; ceramics based on silicon, aluminum, oxygen, and nitrogen; and BeO.

5. The adhesive composition of claim 1, wherein the adhesive composition comprises inorganic fillers having different sizes, different shapes, or both different sizes and different shapes.

6. The adhesive composition of claim 1, wherein the inorganic fillers represent from 60 to 80 vol. % with respect to a total volume of the adhesive composition.

7. The adhesive composition of claim 1, wherein the adhesive composition has a weight ratio of the polymer to the inorganic fillers in the range from 1:4 to 1:11.

8. An adhesive layer formed of the adhesive composition, dried, of claim 1.

9. The adhesive layer of claim 8, wherein said layer comprises at least one preceramic polymer that is crosslinked, ceramized, or both crosslinked and ceramized.

10. A use of the adhesive layer of claim 8 in microelectronics, in a layer transfer method.

11. The adhesive composition of claim 1, wherein the polymer comprises at least one silicon based preceramic polymer.

12. The adhesive composition of claim 7, wherein the adhesive composition has a weight ratio of the polymer to the inorganic fillers in the range from 1:5 to 1:11.

Description

DESCRIPTION OF THE DRAWINGS

[0106] FIG. 1 illustrates two conventional methods of layer transfer between two substrates.

[0107] FIG. 2 illustrates an adhesive support obtained after the deposition of the adhesive composition according to the invention on a silicon or silica substrate.

[0108] FIG. 3 illustrates an adhesive support obtained after the deposition of the adhesive composition according to the invention.

[0109] FIG. 4 shows photographs of layers obtained after the deposition of the adhesive composition according to the invention on a silicon or silica substrate after a crosslinking at 200 C.

[0110] FIG. 5 shows photographs of layers obtained after the deposition of the adhesive composition according to the invention on a silicon or silica substrate after a thermal treatment at 350 C. for 30 minutes.

[0111] FIG. 6 illustrates the thermal conductivity according to the quantity of fillers for adhesive compositions according to the invention.

[0112] FIG. 7 corresponds to the enlargement of a portion of FIG. 6.

DETAILED DESCRIPTION OF THE INVENTION

Preparation of Samples

[0113] A plurality of examples of adhesive compositions according to the invention have been prepared. To achieve this, the following components are mixed before the application of the adhesive composition onto a substrate: [0114] from 15 to 30 vol. % of a polysiloxane having a high rate of conversion into silica (Wacker's reference SilresMK); [0115] from 60 to 85 vol. % of one or a plurality of inorganic fillers; [0116] a xylene-type solvent.

[0117] The volume contents are expressed with respect to the total volume of the adhesive composition except for the organic solvent.

[0118] The inorganic fillers used are thermally conductive and electrically insulating fillers with different grain sizes.

[0119] The adhesive composition is homogenized to distribute the inorganic fillers (18) within the preceramic polymer (17) (FIGS. 2 and 3). It is then deposited by spreading with a doctor blade on a silicon or silica substrate (11) (FIG. 2). It may also be used alone, that is, without a substrate (FIG. 3).

[0120] The substrate-free deposition enables to form samples to measure the thermal conductivity. It also enables to form a substrate made of adhesive composition, with no support.

[0121] An adhesive layer is obtained after evaporation of the solvent. It is crosslinked, for example, by thermal treatment at 200 C. for 30 minutes (FIG. 4).

TABLE-US-00001 TABLE 1 examples of embodiment of the adhesive composition according to the invention. Example 1 2 3 4 5 6 7 8 9 10 Fillers C1 C1 C2 C2 C1 C1 C3 C3 C4 C5 (vol. %) (60) (60) (60) (60) (70) (85) (60) (80) (85) (85) Polymer P1 P1 P1 P1 P1 P1 P1 P1 P1 P1 (vol. %) (40) (40) (40) (40) (30) (15) (40) (20) (15) (15) C1: AlN fillers (d50 = 0.125 m) C2: functionalized AlN fillers (d50 = 0.125 m) C3: AlN fillers (1/d50 = 0.7-11 m; 2/d50 = 2-4.5 m: 3/d50 = 0.8-2 m) C4: mixture of AlN fillers (d50 = 7.5 m) and of nanometer AlN fillers C5: mixtures of fillers C1 + C4 P1: Wacker's SilresMK polysiloxane

[0122] The volume contents are expressed with respect to the total volume of the adhesive composition, except for the organic solvent.

[0123] The adhesive composition according to example 2 has been submitted to a thermal treatment at 350 C. for 30 minutes.

[0124] FIGS. 6 and 7 illustrate the thermal conductivity of these adhesive compositions.

Thermal Tests

[0125] The layers obtained by deposition of the adhesive compositions according to examples 1 to 10 have been tested after a thermal treatment at 350 C. for 30 minutes in a furnace under air (FIG. 5). At the end of the thermal treatment, no crack is observed on the layers.

[0126] Tests have also been carried out at 450 C., after a crosslinking at 200 C. In this case, the depositions also appear with no cracks.

[0127] Tests have also been carried out at 350 C., after a crosslinking at 150 C. In this case, the depositions also appear with no cracks.

[0128] No degradation can be observed at the end of these different thermal treatments.

[0129] Further, the bonding strength on a silicon substrate has been measured after the thermal treatments. It is approximately in the range from 7 to 8 MPa, which is equivalent or even greater than for conventional epoxy glues.

Thermal Conductivity

[0130] FIGS. 6 and 7 show that the thermal conductivity of the layers obtained by deposition of the adhesive compositions of examples 1 to 10 can be controlled according to the following parameters: [0131] the functionalization of the fillers which improves the wettability of the fillers in the adhesive composition, [0132] a thermal treatment of the adhesive composition at a temperature higher than the crosslinking temperature, which enables to densify the network and favors the percolation, [0133] the filler grain size, [0134] the quantity of fillers.