CONTROLLING THE POROSITY OF METAL PASTES FOR PRESSURE FREE, LOW TEMPERATURE SINTERING PROCESS
Metal pastes and methods make it possible to produce extremely compact layers between contact surfaces of structural components, which layers are sufficiently elastic to permanently withstand mechanical and thermal stress variations. This is achieved by the porosity of a corresponding contact area being controlled. For this purpose, a metal paste is provided which contains 70-90% by weight of a metal powder, 1-20% by weight of an endothermically decomposable metal compound and 5-20% by weight of a solvent having a boiling point or range above 220° C., the metal paste being compactable exothermically to form a metal contact.
1 . A metal paste comprising 70-90% by weight of a metal powder, 1-20% by weight of an endothermically decomposable metal compound and 5-20% by weight of a solvent having a boiling point or range above 220° C., such that the metal paste is compactable exothermically to form a metal contact.
2 . The metal paste according to claim 1 , wherein the metal paste contains 11-20% by weight of the solvent with a boiling point or range above 220° C.
3 . The metal paste according to claim 1 , wherein the endothermically decomposable metal compound is a copper compound or noble metal compound.
4 . The metal paste according to claim 1 , wherein the metal powder comprises predominantly a metal selected from silver, copper, gold, palladium, and platinum.
5 . The metal paste according to claim 1 , wherein the metal paste is compactable exothermically without supplying oxygen to form a metal contact.
6 . The metal paste according to claim 1 , wherein the paste has a form of a suspension.
7 . A process for joining contact surfaces placed opposite each other, comprising contacting the contact surfaces with each other via a metal paste according to claim 1 , and compacting the metal paste exothermically.
8 . The process according to claim 7 , wherein the solvent present in the metal paste has a boiling point or range above 250° C.
9 . The process according to claim 8 , wherein the metal compound contained in the metal paste has a decomposition temperature below 400° C.
10 . The process according to claim 8 , wherein the metal compound contained in the metal paste has a decomposition temperature below 350° C.
11 . The process according to claim 8 , wherein the metal compound contained in the metal paste has a decomposition temperature below 300° C.
12 . A structural component comprising structural elements arranged on top of each other, the structural elements being joined by a compacted metal paste according to claim 1 .