Silver sintering preparation and the use thereof for the connecting of electronic components

Abstract

A silver sintering preparation comprising: (A) 30 to 88 wt.-% of silver flake particles having a mean particle diameter (d.sub.50) in the range of >1 to 20 m, (B) 5 to 30 wt.-% of at least one silver precursor, (C) 1 to 10 wt.-% of an organic polymer system, and (D) 6 to 30 wt.-% of organic solvent,
wherein the organic polymer system (C) is chemically essentially stable at temperatures <300 C. and forms a continuous phase together with the organic solvent (D).

Claims

1. A silver sintering preparation comprising: (A) 30 to 88 wt.-% of silver flake particles having a mean particle diameter (d.sub.50) in the range of >1 to 20 m, (B) 5 to 30 wt.-% of at least one silver precursor, (C) 1 to 10 wt.-% of an organic polymer system, and (D) 6 to 30 wt.-% of organic solvent, wherein the organic polymer system (C) is chemically essentially stable at temperatures <300 C. and forms a continuous phase together with the organic solvent (D).

2. The silver sintering preparation of claim 1, wherein the silver flake particles (A) comprise a surface coating comprising at least one type of organic compound.

3. The silver sintering preparation of claim 2, wherein the at least one type of organic compound is selected from the group consisting of free fatty acids, fatty acid salts and fatty acid esters.

4. The silver sintering preparation of claim 1, wherein the at least one silver precursor is selected from the group consisting of silver carbonate, silver(I) lactate, silver(II) formate, silver citrate, silver(I) oxide and silver(II) oxide.

5. The silver sintering preparation of claim 1, wherein the organic polymer system (C) consists of at least one organic polymer.

6. The silver sintering preparation of claim 5, wherein the at least one organic polymer is selected from the group consisting of phenoxy ether resins, phenolic resins, polyimides, polyamides, polysulfones, benzoxazine resins, melamine formaldehyde resins, acrylonitrile butadiene styrene copolymers, (meth)acryl copolymers, polyesters, polyurethanes, polysiloxanes and any hybrids thereof.

7. The silver sintering preparation of claim 5, wherein the at least one organic polymer has a weight average molar mass M.sub.w of >1000 to 100000, as determined by gel permeation chromatography.

8. The silver sintering preparation of claim 5, wherein the at least one organic polymer exhibits a glass transition temperature T.sub.g in the range of >60 C. to 190 C., as determined by Digital Scanning calorimetry (DSC) with a heating rate of 5 K per minute.

9. The silver sintering preparation of claim 1, further comprising a total of 0 to 10 wt.-% of one or more further ingredients (E) different from ingredients (A) to (D).

10. 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 claim 1 being situated between metal contact surfaces of the electronic components, and in which (b) the sandwich arrangement is being sintered.

11. The method of claim 10, wherein each of the electronic components 1 and 2 has a metal contact surface.

12. The method of claim 11, wherein the metal contact surfaces of the electronic components 1 and 2 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.

13. The method of claim 12, wherein there is no pretreatment of a non-precious metal contact surface prior to carrying out the sintering step (b).

14. The method of claim 10, wherein the sintering proceeds at a temperature of 200 to 280 C. with or without applying mechanical pressure and with or without pretreatment of the precious metal or non-precious metal contact surfaces.

15. The method of claim 10, wherein when a non-precious metal contact surface of an electronic component is involved in the sintering of step (b), the sintering of step (b) is performed in an inert or oxygen-free atmosphere.

Description

EXAMPLES

(1) 1. Production of Silver Sintering Preparations:

(2) Silver sintering preparations 2 to 5 (according to the invention) and reference paste 1 were produced by mixing the individual ingredients according to table 1 at comparable rheological behavior. All amounts given are in units of wt.-%.

(3) TABLE-US-00001 TABLE 1 Reference paste 1 Paste 2 Paste 3 Paste 4 Paste 5 Silver particles.sup.1) 66.80 66.80 66.80 62.00 58.00 Silver carbonate 19.95 19.95 19.95 18.00 17.00 Terpineol 3.00 3.31 Ethylcellulose 0.25 2-Ethyl-1,3-hexanediol 8.00 Isooctadecyl alcohol 2.00 Dimethyl phthalate 5.80 5.00 DBE.sup.2) 2.48 Diethylene glycol 4.00 8.00 monoethyl acetate y-butyrolactone 1.00 6.00 15.00 Diethyl adipate 4.25 Phenoxy ether resin.sup.3) 1.66 4.00 4.50 Phenolic resin.sup.4) 1.50 Polyimide.sup.5) 5.00 Total 100 100 100 100 100 .sup.1)Silver flakes having a mean particle size (d.sub.50) of 4 m with a coating of 0.7 wt.-% lauric acid/stearic acid (weight ratio 1:3) .sup.2)Dibasic ester 422053 from Sigma-Aldrich .sup.3)Phenoxy ether resin (bisphenol A/epichlorohydrin resin) having a weight average molar mass M.sub.w of 52000 Da .sup.4)GP phenolic resin BKRmolecular-2620 from Georgia-Pacific Chemicals LLC .sup.5)MATRIMID 5218 US from Huntsman
2. Application and Pressure-Free Sintering of Compositions 1 to 5:

(4) 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 30 m thick wet layer. Then, the applied composition was contacted without previous drying to a silicon chip via its 22 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 200 C. over the course of 60 minutes and then maintained at 200 C. for 60 minutes. Then, the so formed arrangement was cooled steadily to 30 C. over the course of 60 minutes.

(5) 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.

(6) TABLE-US-00002 TABLE 2 Composition 1 2 3 4 5 Shear strength at room 1.0 9.2 22.4 17.6 10.8 temperature (N/mm.sup.2)