Methods for establishing thermal joints between heat spreaders or lids and heat sources

1. A method of establishing a thermal joint for conducting heat between a heat spreader and a heat source of an electronic device, the heat source having a normal operating temperature range, the method comprising:

positioning a thermal interface material (TIM 1 ) in an initial solid state in the form of a pad between the heat spreader and the heat source, wherein the thermal interface material comprises a phase change thermal interface material; and

heating the thermal interface material, while under pressure, to a temperature within a range from about 45 degrees Celsius to about 70 degrees Celsius such that the thermal interface material becomes flowable to form a thin bond line between the heat spreader and the heat source and establishes the thermal joint between the heat spreader and the heat source, whereupon removal of the pressure, the thermal interface material returns to the solid state and remains solidified as the thermal interface material precludes the heat source from heating beyond the normal operating temperature range during operation of the electronic device and heat is flowable through the thermal joint from the heat source to the heat spreader during operation of the electronic device whereby temperature of the heat source is reduced;

wherein the thermal interface material is silicone free; and

wherein the phase change thermal interface material is shear thinning and thixotropic such that the phase change thermal interface material is not flowable at the temperature within the range from about 45 degrees Celsius to about 70 degrees Celsius except under pressure and such that the phase change thermal interface material maintains shape unless force is applied even when the phase change thermal interface material is at the temperature within the range from about 45 degrees Celsius to about 70 degrees Celsius.

2. The method of claim 1 , wherein:

the thermal interface material is soft at room temperature with a shore 00 hardness of less than 80 at a temperature of 25 degrees Celsius; and

the normal operating temperature range of the heat source is within a range from about 30 degrees Celsius to about 60 degrees Celsius.

3. The method of claim 1 , wherein:

the thermal interface material is soft at room temperature with a shore 00 hardness of less than 80 at a temperature of 25 degrees Celsius; and

the heating the thermal interface material, while under pressure, to a temperature within a range from about 45 degrees Celsius to about 70 degrees Celsius comprises heating the thermal interface material, while under pressure, to a temperature that is below the normal operating temperature range of the heat source.

4. The method of claim 1 , wherein:

the thermal interface material is soft at room temperature with a shore 00 hardness of less than 80 at a temperature of 25 degrees Celsius; and

the heating the thermal interface material, while under pressure, to a temperature within a range from about 45 degrees Celsius to about 70 degrees Celsius comprises heating the thermal interface material, while under pressure, to a temperature that is within the normal operating temperature range of the heat source.

5. The method of claim 1 , wherein:

the thermal interface material is soft at room temperature with a shore 00 hardness of less than 80 at a temperature of 25 degrees Celsius; and

the heating the thermal interface material, while under pressure, to a temperature within a range from about 45 degrees Celsius to about 70 degrees Celsius comprises heating the thermal interface material, while under pressure, to a temperature of about 50 degrees.

6. The method of claim 1 , wherein:

the phase change thermal interface material is naturally tacky; and

the method further comprises pre-applying the phase change thermal interface material to the heat spreader, without using any additional adhesive between the phase change thermal interface material and the heat spreader, before positioning the phase change thermal interface material between the heat spreader and the heat source, such that the phase change thermal interface material adheres to the heat spreader without any additional adhesive.

7. The method of claim 1 , wherein the method includes curing an adhesive for attaching the heat spreader to the electronic device, which curing heats the phase change thermal interface material to the temperature within the range from about 45 degrees Celsius to about 70 degrees Celsius.

8. The method of claim 1 , wherein:

the electronic device comprises a semiconductor device having the heat source;

the heat spreader comprises a lid of the electronic device;

the phase change thermal interface material is positioned between the semiconductor device and the lid; and

the method further comprises positioning a second thermal interface material (TIM 2 ) between a heat sink and the lid, whereby the semiconductor device is in effective thermal communication with the heat sink via the phase change thermal interface material, the lid, and the second thermal interface material.

9. The method of claim 1 , wherein the method comprises positioning the thermal interface material between the heat spreader and the heat source prior to curing an adhesive for attaching the heat spreader to the electronic device.

10. The method of claim 9 , further comprising attaching the heat spreader to the electronic device by curing the adhesive.

11. The method of claim 9 , further comprising attaching the heat spreader to the electronic device by curing the adhesive, and wherein the heating the thermal interface material, while under pressure, to the temperature within the range from about 45 degrees Celsius to about 70 degrees Celsius is during the curing.

12. The method of claim 1 , wherein:

the thermal interface material has an initial footprint smaller than a footprint of the heat source; and

the method includes increasing the footprint of the thermal interface material during the heating of the thermal interface material while under pressure.

13. The method of claim 1 , wherein the thermal interface material has a shore 00 hardness less than 80 at a temperature of 25 degrees Celsius.