Flip Chip Interconnection With Double Metal Posts
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Solution Overview
Problem
Existing microelectronic packaging technologies face challenges in minimizing package thickness while enhancing joint reliability in flip-chip interconnections.
Innovation Solution
The use of solid metal posts with specific dimensions and materials, such as copper, extending from both the microelectronic element and substrate, joined by fusible metal, with a unique geometry and underbump metallizations to create conductive columns that increase standoff height and reduce pitch, facilitating improved mechanical and electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional flip-chip interconnection with solder lumps is used, then electrical connection is achieved, but package thickness cannot be minimized and joint reliability is insufficient
Solution Approach 1:
The interconnection structure is segmented into multiple components: solid metal posts extending from the substrate, solder lumps on the chip bond pads, and underfill material in the gap. This segmentation allows each component to perform its specific function optimally - the solid posts provide mechanical support and electrical conduction, the solder lumps create reliable joints, and the underfill protects the connections, thereby improving joint reliability without increasing package thickness
Solution Approach 2:
The invention transitions from traditional planar solder bump connections to a three-dimensional structure with solid metal posts extending vertically from the substrate. This dimensional change enables the posts to provide both mechanical support and electrical conduction pathways, allowing the package to achieve greater reliability while maintaining minimal thickness by utilizing vertical space efficiently
2Reliability
If solder lumps are used for connection, then electrical pathway is established, but stress on joints increases and current density at solder interface increases
Solution Approach 1:
Solid metal posts serve as intermediary elements between the substrate and the solder lumps. These posts provide a robust mechanical foundation and additional electrical conduction pathway, reducing the stress burden on the solder joints themselves. The underfill material acts as another intermediary, distributing mechanical stress and protecting the solder-solder joint interface from excessive stress and current density concentrations
Solution Approach 2:
The interconnection structure employs composite materials including solid metal posts (copper or other conductive metals), solder lumps (tin-lead or lead-free solder), and underfill material (epoxy or polymer-based). This composite approach combines the high conductivity and mechanical strength of metal posts with the bonding capabilities of solder and the protective properties of underfill, thereby reducing joint stress and improving overall durability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration reduces stress on the joints, allows for easier underfill application, and enhances durability by decreasing current density at the solder interface, thereby improving the reliability and variety of underfills used in microelectronic packaging.
Implementation Method 1
joined to the first solid metal posts with a fusible metal
Implementation Method 2
When it melts the solder flows to form truncated spheres
Implementation Method 3
an underfill material may be deposited between the front surface of the microelectronic element and the top surface of the substrate
Data Source
AI summary
A microelectronic assembly includes a substrate having a first surface, a plurality of first conductive pads exposed thereon, and a plurality of first metal posts. Each metal post defines a base having an outer periphery and is connected to one of the conductive pads. Each metal post extends along a side wall from the base to ends remote from the conductive pad. The assembly further includes a dielectric material layer having a plurality of openings and extending along the first surface of the substrate. The first metal posts project through the openings such that the dielectric material layer contacts at least the outside peripheries thereof. Fusible metal masses contact the ends of some of first metal posts and extend along side walls towards the outer surface of the dielectric material layer. A microelectronic element is carried on the substrate and is electronically can be connected the conductive pads.