Patent ID: 9137903
Filing Date: 2015-09-15
Classification: B23K,H01L,H05K,Y10T

Abstract:
1. A microelectronic assembly comprising: a microelectronic element having a plurality of contacts and a dielectric region at a face thereof, in which the dielectric region includes a dielectric material having a low-k dielectric constant; and a substrate including: a first dielectric layer having electrically conductive elements on a first surface facing the face of the microelectronic element, the first dielectric layer having a coefficient of thermal expansion of at least 10 parts per million/° C., wherein the coefficient of thermal expansion of the first dielectric layer is greater than a coefficient of thermal expansion of the microelectronic element, a second dielectric layer overlying the first dielectric layer and having a second surface confronting the face of the microelectronic element, the substrate having a plurality of electrically conductive substrate contacts exposed at the second surface and respectively overlying the conductive elements, and the second dielectric layer having a Young's modulus of less than about 2 GPa, wherein the first dielectric layer and the microelectronic element have a Young's modulus exceeding the Young's modulus of the second dielectric layer, and a plurality of conductive vias extending respectively from the substrate contacts through the second dielectric layer to the conductive elements, electrically connecting the conductive elements with the respective substrate contacts and being disposed entirely below the respective substrate contacts, the substrate contacts being joined respectively to the contacts of the microelectronic element, in which the substrate contacts have a structure including a metal layer and a thickness extending in a direction perpendicular to the second surface of the second dielectric layer configured to define a stiffness of the substrate contacts which is based on the low-k dielectric constant of the dielectric region and the Young's modulus of the microelectronic element, wherein, when an external load resulting from differential thermal expansion or contraction of the assembly based on the difference in the coefficients of thermal expansion between the first dielectric layer and the microelectronic element is applied to the substrate contacts through joints joining the substrate contacts respectively with the contacts of the microelectronic element,