Method to compensate for stress between heat spreader and thermal interface material

• US 6,748,350 B2
• Filed: 09/27/2001
• Issued: 06/08/2004
• Est. Priority Date: 09/27/2001
• Status: Expired due to Term

• Current Assignee: Beijing Xiaomi Mobile Software Co., Ltd. (Xiaomi Corp.)
• Original Assignee: Intel Corporation
• Inventors: Rumer, Christopher L., Houle, Sabina J.
• Primary Examiner(s): Thomson, W.
• Application Number:
  US09/963,438
• Publication Number:
  US 20030058620A1
• Time in Patent Office: 985 Days
• Field of Search: 703/1, 703/5, 703/6, 703/7, 703/9, 703/12, 703/13, 703/18, 361/704, 361/709, 361/717, 361/718, 361/760, 361/719, 257/701, 257/708, 257/706, 257/707, 257/709, 257/718, 374/57, 374/43, 374/46, 374/47, 374/44, 374/49, 702/132, 702/136, 702/131, 438/118, 438/122
• US Class Current: 703/9
• CPC Class Codes: H01L 2224/73204 the bump connector being embedded into the layer connector
• CPC Class Codes: H01L 2224/73253 Bump and layer connectors
• CPC Class Codes: H01L 23/34 Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements thermal treatment apparatus H01L21/00
• CPC Class Codes: H01L 23/3675 characterised by the shape of the housing
• CPC Class Codes: H01L 2924/16152 Cap comprising a cavity for hosting the device, e.g. U-shaped cap

Abstract

A device and method identify and compensate for tensile and/or shear stress due to heat-caused expansion and contraction between an integrated heat spreader and thermal interface material. This device and method may change the shape of the integrated heat spreader based upon the identification of location(s) of high tensile and/or shear stress so that additional thermal interface material may be deposited between the integrated heat spreader and a die in corresponding locations. Utilizing this method and device, heat is efficiently transferred from the die to the integrated heat spreader.

Claims

1. A method comprising;

placing first thermal interface material on a first die of a given type;

coupling a first integrated heat spreader having a flat bottom surface to the first thermal interface material to form a first package, the first thermal interface material having a constant thickness in a contact area between the first die and the bottom surface of the first integrated heat spreader;

exposing the first package to temperature cycling;

determining at least one location in the first thermal interface material with high tensile and shear stress;

altering to shape of a second integrated heat spreader bottom surface to provide a concave shape;

placing second thermal interface material on a second die of the given type; and

coupling the second integrated heat spreader having a concave bottom surface to the second thermal interface material to form a second package, wherein the concave bottom surface allows an increase in to thickness of the second thermal interface material in a center portion of the contact area between the second die and the second integrated heat spreader at the at least one location in to thermal interface material with high tensile and shear stress.

2. The method recited in claim 1, further comprising:

determining material properties and geometry of the first and second packages.

3. The method recited in claim 2, wherein determining the material properties and geometry of the first and second packages comprises:

determining the coefficient of thermal expansion, modulus, stiffness, warpage, and thickness of the respective integrated heat spreader and the thermal interface material of the first and second packages.

4. The method recited in claim 1, wherein determining at least one location in the first thermal interface material with high tensile and shear stress comprises:

taking cross-sections, acoustic analysis, or x-ray failure analysis of the first integrated heat spreader and the first thermal interface material, measuring any seperation between the first integrated heat spreader and first thermal interface material, and locating any air gaps formed in the first thermal interface material.

5. The method recited in claim 1, further comprising:

exposing the second package to temperature cycling.

6. The method recited in claim 5, wherein, after temperature cycling of the second package, the method further comprising:

determining the material properties and geometry of the second integrated heat spreader and the second thermal interface material; and

determining whether separation of the second integrated heat spreader and the second thermal interface material has occurred or air gaps have formed in the second thermal interface material.

7. A method comprising:

creating a first package by placing first thermal interface material on a die of a given type and coupling the bottom of a first integrated heat spreader to the first thermal interface material to form a first interface between the first integrated heat spreader and the first thermal interface material, wherein the bottom of the first integrated heat spreader is flat;

exposing the first package to temperature cycling;

determining at least one location of the first interface having a level of tensile and shear stress that is greater than levels of tensile and shear stress at other locations of the first interface;

altering the shape of a subsequent integrated heat spreader bottom surface to provide a non-convex shape;

creating a subsequent package by placing subsequent thermal interface material on another die of the given type and coupling the bottom of the subsequent integrated heat spreader to the subsequent thermal interface material to form a subsequent interface between the subsequent integrated heat spreader and the subsequent thermal interface material, wherein the non-convex bottom surface allows an increase in the thickness of the subsequent thermal interface material in a portion of to subsequent interface at the at least one location in the thermal interface material with high tensile and shear stress;

exposing the subsequent package to temperature cycling; and

testing whether material properties and geometry of the subsequent package are within desired limits and,

if so, ending the method;

otherwise, determining at least on location of the subsequent interface having a level of tensile and shear stress that is greater than levels of tensile and shear stress at other locations of the subsequent interface, and repeating the operations of altering through testing until the material properties and geometry of the subsequent package are within desired limits.

8. The method recited in claim 7, wherein the bottom surface of the subsequent integrated heat spreader has a concave shape.

9. The method recited in claim 7, further comprising:

determining material properties and geometry of the first and subsequent packages.

10. The method recited in claim 9, wherein determining the material properties and geometry of the first and subsequent packages comprises:

determining the coefficient of thermal expansion, modulus, stiffness, warpage, and thickness of the respective integrated heat spreader and the thermal interface material of the first and subsequent packages.

11. The method recited in claim 7, wherein determining at least one location in the first thermal interface material with high tensile and shear stress comprises:

taking cross-sections, acoustic analysis, or x-ray failure analysis of the first integrated heat spreader and the first thermal interface material, measuring any separation between the first integrated heat spreader and the first thermal interface material, and locating any air gaps formed in the first thermal interface material.

12. The method recited in claim 7, wherein determining at least one location in the subsequent thermal interface material with high tensile and shear stress comprises:

taking cross-sections, acoustic analysis, or x-ray failure analysis of the subsequent integrated heat spreader and the subsequent thermal interface material, measuring any separation between the subsequent integrated heat spreader and the subsequent thermal interface material, and locating any air gaps formed in the subsequent thermal interface material.