CHIP ARRANGEMENT AND METHOD FOR FORMING A CONTACT CONNECTION

Abstract

The invention relates to a chip arrangement (10) and to a method for forming a contact connection (11) between a chip (18), in particular a power transistor or the like, and a conductor material track (14), the conductor material track being formed on a non-conductive substrate (12), the chip being arranged on the substrate or on a conductor material track (15), a silver paste (29) or a copper paste being applied to each of a chip contact surface (25) of the chip and the conductor material track (28), a contact conductor (30) being immersed into the silver paste or the copper paste on the chip contact surface and into the silver paste or the copper paste on the conductor material track, a solvent contained in the silver paste or the copper paste being at least partially vaporized by heating and the contact connection being formed by sintering the silver paste or the copper paste by means of laser energy.

Claims

1. A method for forming a contact connection between a chip and a conductor material track, the conductor material track being formed on a non-conductive substrate, the chip being arranged on the substrate or on another conductor material track, comprising the steps of applying a silver paste or a copper paste to each of a chip contact surface of the chip and the conductor material track, immersing a contact conductor into the silver paste or the copper paste on the chip contact surface and into the silver paste or the copper paste on the conductor material track, heating the silver paste or the copper paste to at least partially vaporize a solvent contained in the silver paste or the copper paste and forming the contact connection by sintering the silver paste or the copper paste with laser energy.

2. The method according to claim 1, wherein a stranded wire is used as a contact conductor.

3. The method according to claim 2, wherein the stranded wire is at least partially infiltrated by the silver paste or the copper paste.

4. The method according to claim 2, wherein only one stranded wire is used per chip contact surface.

5. The method according to claim 1, wherein the step of heating of the silver paste or the copper paste is achieved by arranging the substrate on or on top of a heating element.

6. The method according to claim 1, further comprising the step of supporting the substrate with a clamp during heating.

7. The method according to claim 1, further comprising the step of sintering the silver paste or the copper paste prior to complete vaporization of the solvent.

8. The method according to claim 1, further comprising the step of pressing the contact conductor onto the chip contact surface and/or onto the conductor material track during sintering.

9. The method according to claim 1, further comprising the step of severing the contact conductor after sintering.

10. The method according to claim 1, wherein the chip contact surface is formed by applying a copper strip to a chip surface.

11. The method according to claim 1, wherein a contact metallization is applied to the conductor material track and/or to the chip contact surface.

12. The method according to claim 11, wherein the contact metallization is formed by physical vapor deposition (PVD), sputter deposition, galvanization or electroless plating.

13. The method according to claim 11, wherein the contact metallization is made of silver, nickel, copper, gold, palladium, aluminum or an alloy of one of said metals.

14. A chip arrangement comprising a chip, a non-conductive substrate having a conductor material track formed thereon and a contact conductor, the chip being arranged on the substrate or on a conductor material track, wherein a silver paste or a copper paste is applied to each of a chip contact surface of the chip and the conductor material track, the contact conductor being immersed into the silver paste or the copper paste on the chip contact surface and into the silver paste or the copper paste on the conductor material track, a solvent contained in the silver paste or the copper paste being vaporized by heating and a contact connection being formed by sintering of the silver paste or the copper paste with laser energy.

15. The method of claim 1, wherein the chip is a power transistor.

16. The method of claim 2, wherein the stranded wire is a flat litz wire made of copper or a copper alloy.

17. The chip arrangement of claim 14, wherein the chip comprises a power transistor.

Description

[0024] In the drawing:

[0025] FIG. 1 shows a schematic sectional view of a first embodiment of a chip arrangement during a method step;

[0026] FIG. 2 shows a schematic sectional view of the chip arrangement of FIG. 1 after completion of a contact connection;

[0027] FIG. 3 shows a schematic sectional view of a second embodiment of a chip arrangement; and

[0028] FIG. 4 shows a schematic sectional view of a third embodiment of a chip arrangement.

[0029] FIG. 1 shows a chip arrangement 10 in a schematic sectional view during the production of a contact connection 11. The chip arrangement 10 comprises a non-conductive substrate 12, on whose surface 13 a plurality of different conductor material tracks 14 and 15 are formed. The conductor material tracks 14 and 15 are separated from each other via an isolating gap 16 and are thus electrically isolated from each other. A contact metallization 17 made of silver or a silver alloy is formed on or applied to each of the conductor material tracks 14 and 15. Alternatively, the contact metallization 17 can also be made of nickel, copper, gold, palladium, aluminum or another alloy of one of said metals. A chip 18, which is made of a semiconductor material, is formed on conductor material track 15. A contact metallization 23 made of silver or a silver alloy is applied to a rear side 19 of the chip 18 facing away from conductor material track 15, and contact bumps 21 are applied to a front side 20 of the chip 18 facing toward conductor material track 15. The contact bumps 21 connect the chip 18 to the conductor material track 15. Accordingly, a rear chip contact surface 25 and a front chip contact surface 26 are formed on the chip 18. The chip contact surface 26 of the chip 18 is contacted, that is electrically connected, with a conductor surface 27 of conductor material track 15. A defined amount of silver paste 29 has been applied to each of a conductor surface 28 of conductor material track 14 and to the chip contact surface 25 of the chip 18. A contact conductor 30 is realized as a flat litz wire 31 made of copper and is immersed into the silver paste 29 with each of its ends 32 and 33, the silver paste 29 substantially surrounding the ends 32 and 33.

[0030] As can be taken from FIG. 2, the silver paste 29 was sintered after the solvent contained therein had largely vaporized. Sintering took place in that laser energy was introduced to the silver paste 29 and each of the ends 32 and 33. In this way, a first contact 34 of the contact connection 11 was formed with the silver paste 29 and the end 32 on the conductor surface 28 and a second contact 35 of the contact connection 11 was formed with the silver paste 29 and the end 33 on the chip contact surface 25. The silver particles (not visible) of the silver paste 29 penetrated the ends 32 and 33 and were sintered or partially melted together by the sintering, a particularly tight connection having been formed with the filaments (not visible) of the flat litz wire 31 and the conductor surface 28 and the chip contact surface 25, respectively. Thus, the sintered silver paste 29 is solidified in contact areas 36 and 37.

[0031] FIG. 3 shows a second embodiment of a chip arrangement 38, which differs from the chip arrangement shown in FIG. 2 in that it comprises a flat litz wire 39 that was severed only after sintering of the silver paste 29. An end 40 of the flat litz wire 39 thus protrudes from a contact area 41, a section 42 of the flat litz wire 39 serving to form a contact 43 with the chip 18.

[0032] FIG. 4 shows a third embodiment of a chip arrangement 44, which differs from the chip arrangement shown in FIG. 2 in that it comprises conductor material tracks 45 and 46, between which the chip 47 is arranged. The chip 47 forms two front chip contact surfaces 48 and 49 on a front side 50 of the chip 47, a rear side 51 of the chip 47 being arranged directly on a substrate 52. Each of the chip contact surfaces 48 and 49 is connected to conductor surfaces 57 and 58 of conductor material tracks 45 and 46, respectively, via contact conductors 53 and 54, which are realized as flat litz wires 55 and 56, respectively.

[0033] In the embodiment examples described above, the silver paste can also be replaced with copper paste.