Method of constructing an electronic assembly having an indium thermal couple and an electronic assembly having an indium thermal couple

• US 6,461,891 B1
• Filed: 09/13/1999
• Issued: 10/08/2002
• Est. Priority Date: 09/13/1999
• Status: Expired due to Term

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Churilla, Paul W., Dishongh, Terrance J., Pullen, David H.
• Primary Examiner(s): Smith, Matthew
• Assistant Examiner(s): LUU, CHUONG A
• Application Number:
  US09/394,860
• Publication Number:
  US 20020020912A1
• Time in Patent Office: 1,121 Days
• Field of Search: 438/108, 438/109, 438/106, 438/118, 438/117, 438/127, 438/111, 438/112, 438/110, 438/612, 438/613, 438/15, 438/122, 257/703
• US Class Current: 438/106
• CPC Class Codes: H01L 21/50 Assembly of semiconductor devices using processes or apparatus not provided for in a single one of the subgroups H01L21/06 - H01L21/326, e.g. sealing of a cap to a base of a container
• CPC Class Codes: H01L 2224/16 of an individual bump connector
• CPC Class Codes: H01L 23/3736 Metallic materials H01L23/3732, H01L23/3733, H01L23/3735, H01L23/3737, H01L23/3738 take precedence
• CPC Class Codes: H01L 23/433 Auxiliary members in containers characterised by their shape, e.g. pistons
• CPC Class Codes: H01L 2924/15311 being a ball array, e.g. BGA
• CPC Class Codes: H01L 2924/16152 Cap comprising a cavity for hosting the device, e.g. U-shaped cap

Abstract

According to one aspect of the invention a method of constructing an electronic assembly is provided. The electronic assembly is constructed from a semiconductor package including a package substrate and a semiconductor chip mounted to the package substrate, a thermally conductive member, and a substance including indium. The method comprises securing the thermally conductive member and the semiconductor package in a selected orientation relative to one another with the thermally conductive member on a side of the semiconductor chip opposing the package substrate and with the substance located between the semiconductor chip and at least a portion of the thermally conductive member. The substance is thermally coupled to the semiconductor chip on one side and thermally coupled to the portion of the thermally conductive member on an opposing side.

Claims

1. A method of constructing an electronic assembly, the method comprising:

locating a thermally conductive member, a thermally conductive indium-containing substance, and semiconductor package, including a package substrate and a semiconductor chip, having an integrated circuit formed thereon, mounted to the package substrate, in a selected orientation relative to one another so that at least a portion of the thermally conductive member is located on a side of the semiconductor chip opposing the package substrate and the substance is located between the semiconductor chip and the portion of the thermally conductive member;

heating the substance while the thermally conductive member, the substance and the semiconductor package are in the selected orientation relative to one another, the substance being heated to a temperature above its melting point so that the substance melts; and

cooling the substance to below its melting point so that the substance solidifies, whereafter the substance provides a thermally conductive thermal couple between the semiconductor chip and the portion of the thermally conductive member.

2. A method according to claim 1, wherein the substance contacts the semiconductor chip on one side of the substance.

3. A method according to claim 2, wherein the substance contacts the portion of the member on an opposing side of the substance.

4. A method according to claim 1, wherein the substance contacts two parts of the semiconductor package without causing a short between the two parts.

5. A method according to claim 1, wherein the substance has a melting point below 150°

C. and is heated to above its melting point but below a temperature which causes destruction of the integrated circuit.

6. A method according to claim 1, wherein the member is a lid having a recess and the substance is a first sheet of material that is located in the recess, the method further comprising:

heating the first sheet in the recess to cause it to melt.

7. A method according to claim 6, wherein the lid is of a thermally conductive material that reacts with the alloy when the alloy is heated to cause it to melt, reaction between the alloy and the material of the lid resulting in voids within the alloy, the method further comprising:

removing at least some of the voids from a portion of the substance, the portion of the substance being located between the semiconductor chip and the portion of the lid when the lid and the semiconductor package are located in the selected orientation.

8. A method according to claim 7, wherein the alloy when reacting with the material of the lid causes fewer voids than voids created by pure indium when reacting with the material of the lid.

9. A method according to claim 7, wherein the thermally conductive material of the lid is copper.

10. A method according to claim 7, wherein the voids are massaged out of the portion of the substance.

11. A method according to claim 10, wherein the voids are massaged out by a jet of fluid that creates a force which moves the voids out of the portion of the substance.

12. A method according to claim 11, further comprising:

locating a second sheet of material over the substance; and

heating the substance to a temperature above its melting point to cause melting of the substance but below the melting point of the second sheet of material so that the second sheet of material remains intact while the substance is melted, the jet of fluid impinging on the second sheet and the second sheet preventing splattering of the melted substance by the jet of fluid.

13. A method according to claim 12, wherein the material of the second sheet includes indium.

14. A method according to claim 12, further comprising:

cooling the substance after the voids are massaged out, the substance being cooled to a temperature below its melting point;

locating the substance next to the semiconductor chip; and

heating the substance to above its melting point to cause reflow of the substance over the semiconductor chip.

15. A method according to claim 14, further comprising:

locating a third sheet, which includes indium, over the semiconductor chip, the third sheet and the substance being simultaneously heated to above their melting points, the third sheet acting as a wetting layer for ensuring proper thermal coupling to the semiconductor chip.

16. A method of constructing an electronic assembly from:

(i) a semiconductor package including a package substrate and a semiconductor chip, having an integrated circuit formed thereon, mounted to the package substrate;

(ii) a lid of a thermally conductive material, the lid having a recess; and

(iii) a first sheet of a first alloy, the method comprising;

locating the first sheet in the recess;

heating the first sheet to above its melting point to cause softening of the first alloy, the first alloy reacting with the material of the lid to cause voids within the first alloy;

locating a second sheet of material on the first alloy, the second sheet of material including indium and having a higher melting point than the first alloy;

directing a jet of fluid onto the second sheet while the second sheet and the first alloy are at a temperature between the melting point of the first alloy and the melting point of the second sheet, the second sheet preventing splattering of the first alloy by the jet of fluid, the jet of fluid massaging the voids out of at least a portion of the first alloy;

locating the lid and the semiconductor package in a selected orientation wherein the semiconductor chip is next to the recess; and

heating the second sheet and the first alloy to a temperature above the melting point of the second sheet to cause reflow of the second sheet and the first alloy over the semiconductor chip, the material of the second sheet and the first alloy providing a thermal couple between the lid and the semiconductor chip, with the portion of the first alloy located between the semiconductor chip and the lid.

17. The method of claim 16 wherein the alloy includes indium.

18. A method of constructing an electronic assembly, comprising:

inserting a first alloy including indium into a recess of a thermally conductive lid;

heating the first alloy in the recess to cause it to melt wherein the lid is of a thermally conductive material that reacts with the first alloy when the alloy is heated to cause it to melt, reaction between the alloy and the material of the lid resulting in voids within the alloy;

removing at least some of the voids from a portion of the substance; and

locating the first alloy adjacent to a semiconductor chip, having an integrated circuit formed therein, mounted to a package substrate, the portion of the substance being located between the semiconductor chip and the lid.

19. A method according to claim 18, wherein the alloy when reacting with the material of the lid causes fewer voids than voids created by pure indium when reacting with the material of the lid.

20. A method according to claim 18, wherein the thermally conductive material of the lid is copper.

21. A method according to claim 18, wherein the voids are massaged out of the portion of the substance.

22. A method according to claim 18, wherein the voids are massaged out by a jet of fluid that creates a force which moves the voids out of the portion of the substance.

23. A method according to claim 18, further comprising:

locating a second sheet of material over the substance; and

heating the substance to a temperature above its melting point to cause melting of the substance but below the melting point of the second sheet of material so that the second sheet of material remains intact while the substance is melted, the jet of fluid impinging on the second sheet and the second sheet preventing splattering of the melted substance by the jet of fluid.

24. A method according to claim 18, wherein the material of the second sheet includes indium.

25. A method according to claim 18, further comprising:

cooling the substance after the voids are massaged out, the substance being cooled to a temperature below its melting point;

locating the substance next to the semiconductor chip; and

heating the substance to above its melting point to cause reflow of the substance over the semiconductor chip.