Plated Metal Posts for Fine-Pitch Microelectronic Interconnections
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Solution Overview
Problem
Traditional methods for forming conductive bumps for microelectronic interconnections, such as solder-to-solder interconnections, face difficulties in creating sufficient volume when the pitch is smaller than 150 microns, making it challenging to achieve effective interconnections at fine pitches.
Innovation Solution
The development of interconnection elements with plated metal posts that project outwardly from a dielectric element, where the metal posts are formed by plating onto a mandrel and then removing it, allowing for conductive connections with microelectronic devices or wiring, and optionally including metal wiring traces that can be insulated or connected to these posts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional solder-to-solder interconnection methods are used, then interconnection can be achieved, but it becomes increasingly difficult to form conductive bumps of sufficient volume when the pitch is smaller than 150 microns
Solution Approach 1:
The patent transitions from planar conductive bumps to three-dimensional protruding metal posts that extend vertically from the substrate surface. This dimensional change allows the conductive structure to achieve sufficient volume for fine-pitch interconnections (pitch < 150 microns) by utilizing the vertical dimension, thereby resolving the contradiction between maintaining small pitch and ensuring adequate conductive volume.
Solution Approach 2:
The patent employs a mandrel structure that is formed in advance within the substrate before the metal plating process. This preliminary action creates a precise template that guides the formation of metal posts with controlled dimensions and positioning, enabling accurate conductive bump formation at fine pitches while ensuring sufficient volume through the vertical extension of plated metal around the mandrel.
2Productivity
If the pitch of conductive bumps is reduced to achieve fine-pitch interconnections, then interconnection density increases, but it becomes difficult to form conductive bumps of sufficient volume
Solution Approach 1:
By extending the conductive structure vertically as protruding metal posts rather than maintaining them as planar bumps, the patent enables high interconnection density at fine pitches while simultaneously achieving sufficient conductive volume through the height of the posts, thus resolving the contradiction between density and volume.
Solution Approach 2:
The patent creates a composite structure consisting of a mandrel material (such as solder or conductive paste) combined with plated metal layers. This composite approach allows the mandrel to provide the initial volume and shape at fine pitch, while the plated metal adds vertical extension and enhances the overall conductive volume, thereby achieving both high density and sufficient volume.
3Reliability
If metal posts are formed by plating onto a mandrel and removing it, then reliable conductive interconnections at fine pitches are achieved, but the process complexity increases
Solution Approach 1:
The mandrel structure serves as a preliminary template that is formed during standard substrate fabrication processes. By establishing the mandrel position and dimensions in advance, the subsequent plating process becomes more controlled and reliable, producing consistent metal posts even at fine pitches. The mandrel removal step, while additional, is a simple etching or dissolution process that leaves clean post structures, thereby achieving reliable interconnections with manageable process complexity.
Solution Approach 2:
The mandrel acts as an intermediary structure that facilitates the formation of metal posts. It provides a template for plating, ensures proper positioning at fine pitches, and can be selectively removed after serving its purpose. This intermediary approach enables reliable post formation without requiring complex direct-plating techniques, as the mandrel mediates between the plating process and the final post structure.
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 solution enables reliable conductive interconnections at fine pitches, suitable for microelectronic assemblies with high current density, by forming metal posts with heights of at least 35 microns and pitches less than 150 microns, facilitating connections to microelectronic elements with arrays of exposed contacts.
Implementation Method 1
The posts can be defined by plating a metal onto exposed co-planar surfaces of a mandrel and interior surfaces of openings in a mandrel
Data Source
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AI summary
An interconnection element (170, 190) is provided for conductive interconnection with another element (172) having at least one of microelectronic devices or wiring thereon. The interconnection element includes a dielectric element (187) having a major surface. A plated metal layer (130, 192) including a plurality of exposed metal posts (130) can project outwardly beyond the major surface (176) of the dielectric element. Some of the metal posts can be electrically insulated from each other by the dielectric element (187). The interconnection element typically includes a plurality of terminals (151) in conductive communication with the metal posts. The terminals can be connected through the dielectric element (187) to the metal posts (130). The posts may be defined by plating a metal (122, 124) onto exposed co-planar surfaces of a mandrel (120) and interior surfaces of openings (102) in a mandrel, after which the mandrel can be removed.