Aligned Core Balls for High Aspect Ratio Interconnect Stability
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Solution Overview
Problem
Legacy interconnect joints in microelectronic packaging, such as those used in Package on Package (PoP) configurations, face challenges in achieving high aspect ratios with tight pitches, leading to yield issues and quality concerns due to moisture evaporation and thermal treatment processes.
Innovation Solution
The use of multiple core balls aligned substantially linearly within a solder compound to form interconnect joints, which can achieve high aspect ratios greater than 1.1:1 height/pitch ratio, providing increased strength and stability through compressive and tensile alignment, and allowing for tunable joint shapes and heights.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If legacy copper pillar-based interconnect joints are used, then manufacturing is simpler, but the aspect ratio is limited and yield issues occur due to moisture evaporation and thermal treatment
Solution Approach 1:
The interconnect joint is segmented into multiple discrete core balls (e.g., four core balls) arranged in a linear array rather than using a single continuous copper pillar. This segmentation allows each core ball to independently withstand thermal and moisture stresses, preventing the yield issues associated with legacy copper pillars while achieving the required high aspect ratio of greater than 1.1:1.
Solution Approach 2:
The invention uses composite material construction where core balls (made of copper or copper alloy) are embedded within a solder compound matrix. This composite structure combines the high strength and conductivity of copper core balls with the protective and bonding properties of the solder compound, enabling high aspect ratio joints that resist moisture evaporation and thermal treatment stresses.
2Strength
If core balls are used to achieve high aspect ratio, then strength and stability improve, but device complexity increases
Solution Approach 1:
The invention changes key parameters of the interconnect structure: using discrete core balls with specific diameters (e.g., 50-150 micrometers) spaced at controlled intervals within the solder compound, arranged in a linear array. This parameter-based design achieves high aspect ratio and improved strength while maintaining manufacturability through standardized core ball dimensions and spacing, rather than requiring complex custom structures.
Solution Approach 2:
The solder compound acts as an intermediary material that embeds and protects the core balls, providing both structural support and electrical connectivity. This intermediary approach simplifies the overall structure compared to direct core ball-to-core ball connections, as the solder compound matrix handles stress distribution and bonding while the core balls provide strength and alignment.
3Strength
If multiple core balls are aligned linearly, then compressive and tensile strength increase, but manufacturing precision requirements increase
Solution Approach 1:
The core balls are designed to self-align during the manufacturing process through their spherical geometry and the flow characteristics of the solder compound. When the solder compound is applied and cured, the core balls naturally settle into a linear arrangement due to surface tension and gravity, reducing the need for precise external alignment fixtures or complex positioning mechanisms.
Solution Approach 2:
The use of spherical core balls provides geometric advantages for alignment and stress distribution. The spherical shape allows core balls to roll into proper positions during assembly and ensures uniform stress distribution under compressive and tensile loads, reducing the precision requirements compared to non-spherical geometries while maximizing strength.
Data Source
AI summary
Embodiments herein relate to systems, apparatuses, or processes directed to an interconnect joint that includes multiple core balls within a solder compound where the multiple core balls are substantially linearly aligned. The multiple core balls, which may include copper or be a polymer, couple with each other within the solder and form a substantially linear alignment during reflow. In embodiments, four or more core balls may be used to achieve a high aspect ratio interconnect joint with a tight pitch.