Redistribution Substrate Pillar Geometry for Taller Semiconductor Packaging
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Solution Overview
Problem
Current semiconductor packages face challenges in reducing size and increasing metal pillar height due to physical constraints of photoresist layers, which limits performance and reliability.
Innovation Solution
A semiconductor package design featuring a redistribution substrate with metal pillars having distinct portions, including a cylindrical first portion and a square or octagonal second portion, connected to redistribution patterns and solder balls, allowing for increased height and improved electrical connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the height of metal pillars is increased to improve electrical connectivity and performance, then the electrical conductivity and signal transmission are improved, but the manufacturing complexity and processing requirements increase significantly
Solution Approach 1:
The metal pillar is divided into multiple segments or layers with different cross-sectional shapes. The lower portion has a cylindrical cross-section while the upper portion has a square or rectangular cross-section. This segmentation allows each portion to serve different functions: the cylindrical base provides strong mechanical support and electrical connection, while the squared upper portion facilitates better integration with surrounding structures and reduces manufacturing complexity compared to a single tall pillar
Solution Approach 2:
Different portions of the metal pillar have different geometric properties optimized for their specific locations. The lower cylindrical portion provides rotational symmetry and uniform stress distribution for mechanical support, while the upper squared portion provides directional alignment and integration with anisotropic surrounding structures. This local optimization allows the pillar to achieve both mechanical stability and electrical connectivity without requiring excessive height
2Productivity
If the height of metal pillars is increased to accommodate processing demands, then the electrical performance is improved, but the manufacturing precision and alignment requirements increase
Solution Approach 1:
The metal pillar structure is segmented into distinct portions with different cross-sectional geometries. The transition from cylindrical to squared cross-section creates natural alignment features and reference planes that simplify manufacturing processes. Each segment can be fabricated and positioned independently with relaxed tolerances, reducing the cumulative alignment errors that would occur in a single continuous tall structure
Solution Approach 2:
The metal pillar employs asymmetric geometry with a cylindrical base transitioning to a squared upper portion. This asymmetry creates distinct functional zones: the cylindrical base optimized for rotational symmetry and uniform loading, and the squared upper portion optimized for directional alignment with surrounding anisotropic structures. This geometric asymmetry provides natural registration features that reduce manufacturing precision requirements
Data Source
AI summary
A semiconductor package includes a redistribution substrate having a first side and an opposite second side. A plurality of redistribution patterns are in the redistribution substrate, and a semiconductor chip is on the first side of the redistribution substrate. A plurality of metal pillars are positioned around and spaced apart from a periphery of the semiconductor chip and are connected to the redistribution patterns. A plurality of solder balls are on the second side of the redistribution substrate. Each of the metal pillars includes a third side facing the first side of the redistribution substrate, and an opposite fourth side. The fourth side has a square or octagonal shape in plan view.