Methods for transferring heat from stacked microfeature devices

A method of assembling a microfeature device assembly, comprising:

• attaching a first heat transfer unit to an interposer substrate having terminals, the first heat transfer unit having a first portion and a second portion, wherein the second portion is out of mechanical contact with and spaced apart from the first portion by a first gap extending between the first and second portions, wherein at least a portion of the terminals are aligned with the first gap;
• securing a first microelectronic die having integrated circuitry and first external contacts to the first heat transfer unit, wherein the first external contacts at a front side of the first die are aligned with the first gap and electrically coupled to at least a portion of the terminals on the interposer substrate;
• attaching a second heat transfer unit to a back side of the first die, the second heat transfer unit having a third portion, a fourth portion, and a second gap between the third and fourth portions such that at least a portion of the second external contacts at the back side of the first die are aligned with the second gap;
• and
• securing a second microelectronic die having integrated circuitry and second external contacts to the second heat transfer unit in a stacked arrangement with the first die, wherein the second external contacts at a front side of the second die are aligned with the second gap and electrically coupled to at least a portion of the first external contacts at the back side of the first die,
• wherein the first and second microelectronic dies have the same planform shape when viewed in the stacking direction, and
• wherein the first heat transfer unit has a first thickness and the second heat transfer unit has a second thickness, and wherein the first thickness and the second thickness are equal to or greater than thicknesses of the individual first die and second die.

A method of assembling a microfeature device assembly, comprising:

• attaching a first microelectronic die to an interposer substrate having terminals, the first die having a first perimeter and including first external contacts electrically coupled to corresponding terminals;
• stacking a second microelectronic die having second external contacts on the first die such that the second external contacts at a front side of the second die are electrically coupled to first external contacts at a back side of the first die, wherein the second microelectronic die has a second perimeter the same as the first perimeter when viewed in the stacking direction;
• and
• positioning a heat transfer unit between the first and second dies, wherein the heat transfer unit is composed of a silicon material having a higher thermal conductivity than silicon of the first and second microelectronic dies,
• wherein the heat transfer unit includes a first portion and a second portion, and wherein the second portion is out of mechanical contact with and spaced apart from the first portion by a gap extending between the first and second portions such that the first external contacts of the first die and second external contacts of the second die are aligned with the gap.