Noncircular Interconnects for IC Package Substrates
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Solution Overview
Problem
Existing integrated circuit package substrates with circular microvias and capture pads suffer from misalignment issues due to tolerance stack-up in the manufacturing process, leading to oversized capture pads and increased substrate layer requirements, limiting the lateral spacing for conductive traces and necessitating multiple routing layers.
Innovation Solution
The use of conductive pillars and pads formed through plating and build-up lamination processes, allowing for noncircular cross-sections and improved alignment accuracy, enabling smaller dimensions and combining microstrip and strip line escapes into a single escape line routing layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If circular microvias and capture pads are used with conventional laser drilling, then manufacturing process is simple, but misalignment occurs due to tolerance stack-up requiring oversized pads and multiple layers
Solution Approach 1:
The patent changes the shape of microvias and capture pads from circular to noncircular (rectangular, oval, or polygonal) cross-sections. This asymmetric shape change enables better alignment between the microvia and capture pad, reducing the tolerance stack-up effect and allowing for more precise electrical connections without requiring oversized pads or additional routing layers.
2Manufacturing precision
If oversized capture pads are used to compensate for misalignment, then alignment tolerance is improved, but lateral spacing for conductive traces is reduced
Solution Approach 1:
By using noncircular capture pads that precisely align with noncircular microvias, the patent achieves accurate alignment without requiring oversized pads. The asymmetric shape allows the capture pad dimensions to match the microvia dimensions more closely, maintaining adequate lateral spacing for conductive traces while ensuring proper alignment tolerance.
3Adaptability or versatility
If multiple routing layers are used to accommodate trace routing, then routing capacity is increased, but substrate complexity and layer count increase
Solution Approach 1:
The noncircular microvia and capture pad geometry enables more efficient space utilization on each routing layer. By improving alignment accuracy and reducing the space required for alignment compensation, the asymmetric shape allows conductive traces to be routed more effectively on fewer layers, reducing the overall substrate layer count while maintaining adequate routing capacity.
4Ease of manufacture
If conventional circular microvias are used, then manufacturing process is straightforward, but line density is limited due to spacing requirements
Solution Approach 1:
The patent maintains manufacturing simplicity by using standardized plating and build-up lamination processes, but changes the microvia and capture pad shape to noncircular. This asymmetric geometry allows for closer spacing between adjacent interconnects, increasing the number of conductive traces that can be routed per unit area and thereby increasing line density without significantly complicating the manufacturing process.
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 approach reduces the number of substrate layers required, increases line density, and enhances alignment capabilities, allowing for more efficient routing of conductive traces and reducing the need for additional layers, thereby improving the overall packaging efficiency.
Implementation Method 1
conductive pillars and pads formed through plating and build-up lamination processes
Implementation Method 2
conductive pillars and pads formed through plating and build-up lamination processes
Data Source
AI summary
Package substrates including conductive interconnects having noncircular cross-sections, and integrated circuit packages incorporating such package substrates, are described. In an example, a conductive pillar having a noncircular pillar cross-section is electrically connected to an escape line routing layer. The escape line routing layer may include several series of conductive pads having noncircular pad cross-sections. Accordingly, conductive traces, e.g., strip line escapes and microstrip escapes, may be routed between the series of conductive pads in a single escape line routing layer.