SILVER SINTERING PREPARATION AND THE USE THEREOF FOR THE CONNECTING OF ELECTRONIC COMPONENTS

Abstract

A silver sintering preparation in the form of a silver sintering paste comprising 70 to 95 wt.-% of coated silver particles (A) and 5 to 30 wt.-% of organic solvent (B) or in the form of a silver sintering preform comprising 74.5 to 100 wt.-% of coated silver particles (A) and 0 to 0.5 wt.-% of organic solvent (B), wherein the coating of the coated silver particles (A) comprises silver acetylacetonate (silver 2,4-pentanedionate) and/or at least one silver salt of the formula C.sub.nH.sub.2n+1COOAg with n being an integer in the range of 7 to 10, and wherein the at least one silver salt is thermally decomposable at >160° C.

Claims

1. A silver sintering preparation either in the form of a silver sintering paste comprising 70 to 95 wt.-% of coated silver particles (A) and 5 to 30 wt.-% of organic solvent (B), or in the form of a silver sintering preform comprising 74.5 to 100 wt.-% of coated silver particles (A) and 0 to 0.5 wt.-% of organic solvent (B), wherein the coating of the coated silver particles (A) comprises silver acetylacetonate (silver 2,4-pentanedionate) and/or at least one silver salt of the formula C.sub.nH.sub.2n+1COOAg with n being an integer in the range of 7 to 10, and wherein the at least one silver salt is thermally decomposable at >160° C.

2. The silver sintering preparation in the form of a silver sintering paste of claim 1 comprising 75 to 85 wt.-% of the coated silver particles (A) and 8 to 25 wt.-% of organic solvent (B).

3. The sintering preparation in the form of a silver sintering preform of claim 1 comprising 96 to 100 wt.-% of the coated silver particles (A) and 0 to 0.5 wt.-% of organic solvent (B).

4. The silver sintering preparation of claim 1, wherein the alkyl group C.sub.nH.sub.2n+1 is branched.

5. The silver sintering preparation of claim 4, wherein the branching is characterized by the carbon atom in position 2 carrying 2 or 3 alkyl substituents.

6. The silver sintering preparation of claim 1, wherein the fraction of the silver acetylacetonate and/or the at least one silver salt, relative to the entire coating is at least 60 wt.-%.

7. The silver sintering preparation of claim 1, wherein the fraction of the silver acetylacetonate and/or the at least one silver salt is ≤20 wt.-%, relative to the weight of the coated silver particles (A).

8. A method for the connection of electronic components, in which (a) a sandwich arrangement is provided, which comprises at least (a1) an electronic component 1, (a2) an electronic component 2, and (a3) a silver sintering preparation of according to claim 1 being situated between metal contact surfaces of the electronic components, and in which (b) the sandwich arrangement is being sintered.

9. The method of claim 8, wherein each of the electronic components 1 and 2 has a metal contact surface.

10. The method of claim 9, wherein the metal contact surfaces are made of (i) non-precious metal selected from the group consisting of copper, nickel and aluminum or of (ii) a precious metal or (iii) one of the metal contact surfaces is made of non-precious metal selected from the group consisting of copper, nickel and aluminum and the other is made of precious metal.

11. The method of claim 10, wherein there is no pretreatment of a non-precious metal contact surface prior to carrying out the sintering step (b).

12. The method of claim 10, wherein the sintering proceeds at a temperature in the range of 200 to <300° C. with or without applying mechanical pressure and/or with or without pretreatment of the precious metal or non-precious metal contact surfaces.

13. The method of claim 11, wherein the metal of at least one of the non-pretreated metal contact surfaces of the electronic components is a non-precious metal, and wherein the sintering step (b) is carried out in an inert atmosphere without application of mechanical pressure at a sintering temperature in the range of 200 to <300° C.

14. The method of claim 13, wherein the non-precious metal is copper, and wherein the inert atmosphere is a non-reducing atmosphere.

Description

EXAMPLES

[0094] 1. Production of Silver Sintering Pastes:

[0095] Silver sintering pastes 1 to 4 (according to the invention) and a reference paste were produced by mixing the individual ingredients according to Table 1 at comparable rheological behavior. All amounts given are in units of wt.-%.

TABLE-US-00001 TABLE 1 Ref. Ex. 1 Ex. 2 Ex. 3 Ex. 4 Silver particles.sup.1) 82 coated with 1 wt.-% stearic acid Silver particles.sup.1) 82 coated with 1 wt.-% Ag caprylate Silver particles.sup.1) 82 coated with 5 wt.-% Ag neodecanoate Silver particles.sup.1) 82 coated with 10 wt.-% Ag neodecanoate Silver particles.sup.1) 82 coated with 5 wt.-% Ag 2,4-pentanedionate Isostearic acid 2.7 2.7 2.7 2.7 2.7 Tripropylene glycol 7.2 7.2 7.2 7.2 7.2 monobutyl ether Butyl polyglycol 7.7 7.7 7.7 7.7 7.7 Ethylcellulose 0.4 0.4 0.4 0.4 0.4 Total 100 100 100 100 100 .sup.1)Silver particles having a mean particle size (d50) of 0.5 μm

[0096] 2. Application and Pressure-Free Sintering of Sintering Compositions:

[0097] The respective composition was applied by means of dispensing onto the copper surface of a lead frame made of a copper-rich copper/iron alloy (96 wt.-% copper, 4 wt.-% Fe) to produce a 50 μm thick wet layer. Then, the applied composition was contacted without previous drying to a silicon chip via its 2 mm×2 mm silver metal contact surface. The subsequent pressure-free sintering took place according to the following heating profile in a nitrogen atmosphere comprising max. 50 ppm of oxygen: The contact site was heated steadily to 250° C. over the course of 60 minutes and then maintained at 250° C. for 60 minutes. Then, the so formed arrangement was cooled steadily to 30° C. over the course of 60 minutes.

[0098] After the sintering, the bonding strength was determined by shear testing. In this context, the electronic components were sheared off with a shearing chisel at a rate of 0.3 mm/s at room temperature. The force was measured by means of a load cell (DAGE 4000 plus device made by DAGE, Germany). Table 2 shows the results obtained with compositions 1 to 5.

TABLE-US-00002 TABLE 2 Composition refer- Exam- Exam- Exam- Exam- ence ple 1 ple 2 ple 3 ple 4 Shear strength at 1.0 7.6 33.1 24.3 11.3 room temperature (N/mm.sup.2)