Via Pillar Interconnects for High-Density Substrates
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Solution Overview
Problem
Current interconnect structures, such as those using the 'drill & fill' method, face limitations in achieving high-density, small-sized, and varied via geometries due to rough sidewalls, tapering, and difficulties in simultaneous optimization of different via sizes, leading to reliability issues and increased costs.
Innovation Solution
The development of a multilayer composite electronic structure with via pillars embedded in an outer dielectric material, allowing for finer pitch connections and non-circular shapes, coupled with a process involving photo-resist patterning and electroplating, enables the creation of high-density, reliable, and cost-effective interconnects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If laser drilling is used to create vias, then via channels can be formed through dielectric material, but the via sidewalls become rough and tapered, reducing effective diameter and electrical contact quality
Solution Approach 1:
The patent replaces the mechanical laser drilling process with an electrochemical etching process. Instead of using laser energy to ablate material, the invention uses electrochemical reactions to dissolve dielectric material and form vias, resulting in smooth sidewalls and precise dimensional control without the tapering and roughness inherent in laser drilling
Solution Approach 2:
The invention changes the fundamental parameter of via formation from thermal ablation (laser) to electrochemical dissolution. By controlling electrochemical parameters such as current density, electrolyte composition, and etching time, the process achieves precise via dimensions with smooth sidewalls, directly addressing the sidewall quality issue while maintaining via formation capability
2Ease of manufacture
If electroplating is used to fill drilled vias, then copper can be deposited into via channels, but dimpling or overfill occurs, creating difficulties in stacking vias
Solution Approach 1:
The invention performs preliminary actions by first forming precise via channels through electrochemical etching with controlled depth and smooth sidewalls, then applying a seed layer before electroplating. This preliminary preparation ensures that subsequent electroplating fills vias uniformly without dimpling or overfill, enabling precise via stacking
Solution Approach 2:
The invention changes the via formation mechanism from mechanical drilling to electrochemical etching, which provides precise control over via depth and dimensions. This parameter control ensures that vias are formed to exact specifications, allowing uniform electroplating fill and eliminating the dimpling and overfill problems that occur with laser-drilled vias
3Adaptability or versatility
If different sized vias are drilled and filled using drill & fill technology, then various via sizes can be created, but the filling process cannot be simultaneously optimized for different sizes, exasperating dimpling or overfill problems
Solution Approach 1:
The invention applies a universal electrochemical etching process that can form vias of any size or shape with consistent precision. The same electrochemical mechanism works uniformly for all via sizes, eliminating the need for separate optimization processes for different via dimensions and enabling consistent fill quality across all via types
Solution Approach 2:
The invention uses electrochemical etching with controllable parameters (current density, etching time, electrolyte composition) that can be adjusted to create vias of different sizes while maintaining consistent sidewall quality and depth control. This universal approach allows simultaneous optimization for all via sizes, unlike laser drilling where each size requires separate parameter optimization
4Productivity
If high density of vias is required in close proximity, then via spacing must be reduced, but laser drilling difficulty increases and quality decreases
Solution Approach 1:
The patent replaces laser drilling with electrochemical etching, which is not limited by the same physical constraints as laser drilling. The electrochemical process can form high-density via arrays with consistent quality because it relies on electrical field distribution rather than optical focusing, allowing uniform via formation even at very close spacings
Solution Approach 2:
The invention changes the via formation mechanism to electrochemical etching, where via dimensions and spacing are controlled by electrical parameters rather than optical parameters. This allows precise control of via size and spacing even at high densities, maintaining via quality while achieving higher via densities than laser drilling can provide
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 enables the fabrication of high-density interconnects with smaller via diameters and varied geometries, improving reliability and reducing costs by allowing for precise control over via sizes and shapes, facilitating miniaturization and higher packing densities.
Implementation Method 1
The filling process of the drilled via holes is usually achieved by copper electroplating
Implementation Method 2
laser to drill holes through the subsequently laid down dielectric substrate
Data Source
AI summary
A method of attaching a chip to the substrate with an outer layer consisting of via pillars embedded in a dielectric such as solder mask, with ends of the via pillars flush with said dielectric, the method consisting of optionally removing an organic varnish, positioning a chip having legs terminated with solder bumps in contact with exposed ends of the via pillars, and applying heat to melt the solder bumps and to wet the ends of the vias with solder.