Structures and methods for low temperature bonding using nanoparticles
A method of making an assembly can include forming a first conductive element at a first surface of a substrate of a first component, forming conductive nanoparticles at a surface of the conductive element by exposure to an electroless plating bath, juxtaposing the surface of the first conductive element with a corresponding surface of a second conductive element at a major surface of a substrate of a second component, and elevating a temperature at least at interfaces of the juxtaposed first and second conductive elements to a joining temperature at which the conductive nanoparticles cause metallurgical joints to form between the juxtaposed first and second conductive elements. The conductive nanoparticles can be disposed between the surfaces of the first and second conductive elements. The conductive nanoparticles can have long dimensions smaller than 100 nanometers.
1. An assembly, comprising:
a first component including a substrate having a first surface and a plurality of substantially rigid first posts at the first surface, the first posts extending away from the first surface in a first direction, each first post having a top surface generally facing in the first direction, the top surface of each of the first posts projecting a height above the first surface such that the top surface is remote from the first surface, each first post having edge surfaces extending substantially in a second direction opposite the first direction away from the top surface thereof; and
a second component including a substrate having a major surface and a plurality of second conductive elements at the major surface, each second conductive element having a top surface generally facing in the second direction,
the first posts being joined with the second conductive elements, such that the top surfaces of the first posts at least partially confront the top surfaces of the second conductive elements, the top surfaces of at least some of the first posts being non-coplanar with respect to one another,
each first post being electrically interconnected to a corresponding one of the second conductive elements by a bond region including impurities that show structural evidence of the use of metal nanoparticles having long dimensions smaller than 100 nanometers in the joining process, each bond region penetrating at least partially into the first post and the second conductive element, each bond region containing a plurality of microvoids, each microvoid having a maximum width below 0.5 microns,
the thickness of different ones of the bond regions varying by up to 3 microns so as to accommodate the non-coplanarity of the top surfaces of the at least some of the first posts.
2. The assembly of claim 1 , further comprising a barrier layer substantially completely covering the top surface and the edge surfaces of each first post, each bond region being located between the barrier layer of a respective one of the first posts and the top surface of a corresponding one of the second conductive elements.
3. The assembly of claim 1 , wherein the plurality of second conductive elements are substantially rigid second posts extending away from the major surface in the second direction, and the top surface of each of the second posts projects a height above the major surface of the second component such that the top surface is remote from the major surface, each second post having edge surfaces extending substantially in the first direction away from the top surface thereof.
4. The assembly of claim 3 , wherein the edge surfaces of each of the first posts and second posts have a surface roughness of at least 3.0 nanometers.
5. The assembly of claim 1 , wherein at least one of the first or second components is a microelectronic element including active semiconductor devices.
6. The assembly of claim 1 , wherein the first posts and the second conductive elements each consist essentially of the same material, and the bond region includes at least one metal selected from a group consisting of copper, gold, silver, nickel, tin, aluminum, an alloy including silver, an alloy including indium, and an alloy including tin.
7. The assembly of claim 1 , wherein at least one of the first posts and second conductive elements comprises an electrically conductive pad or an electrically conductive trace.
8. The assembly of claim 1 , wherein the first component is a microelectronic element wafer including a plurality of microelectronic element portions, each microelectronic element portion including a respective subset of the first posts at the first surface, and the second component is at least a portion of a substrate panel including a plurality of substrate portions, each substrate portion including a respective subset of the second conductive elements at the major surface.
9. A system comprising an assembly according to claim 1 and one or more other electronic components electrically connected to the assembly.
10. The system of claim 9 , further comprising a housing, the assembly and the other electronic components being mounted to the housing.