Patent ID: 8957520
Filing Date: 2015-02-17
Classification: H01L

Abstract:
1. A microelectronic assembly comprising: a substrate including a dielectric element having first and second opposed surfaces, a first dielectric layer having a first material structure adjacent the first surface, and a second dielectric layer having a second material structure different from the first material structure, the second dielectric layer disposed between the first dielectric layer and the second surface, wherein the first material structure as the first dielectric layer has a first Young's modulus at least 50% greater than a second Young's modulus of the second material structure as the second dielectric layer, the second Young's modulus being less than two gigapascal (GPa); a plurality of substrate contacts at the first surface, a plurality of terminals at the second surface; and a conductive structure extending through the first and second dielectric layers and electrically connecting the substrate contacts with the terminals; a microelectronic element having a face confronting the first surface and a plurality of element contacts thereon joined with the substrate contacts through conductive masses; and a rigid underfill between the face of the microelectronic element and the first surface, wherein the terminals are configured and usable for bonding the microelectronic assembly to corresponding contacts of a component external to the microelectronic assembly, and wherein the second Young's modulus of the second material structure has a value selected in relation to the first Young's modulus of the first material structure and the terminals have a material structure that permits a predetermined displacement by bending such that, when the terminals are bonded through electrical connections to the corresponding contacts of the external component, the terminals move up to the predetermined displacement by bending relative to the substrate contacts, when an external load is applied to the terminals through the electrical connections between the terminals and the contacts of the external component, to appreciably reduce mechanical stresses in the electrical connections between the terminals and the contacts of the external component, as caused by differential thermal expansion or contraction, which would be present in the electrical connections between the terminals and the contacts of the external component absent said predetermined displacement.