Curved Micro-Springs for Ionic Wind Cooling in Semiconductor Packages
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing cooling methods for high-power semiconductor devices, such as bulky fans, are inefficient for managing heat in thinner, lighter electronics with increasing power density, especially in 3D stacked chip configurations, where passive methods like heat spread and thermal interface materials are hard to apply and fluid-based active cooling is not common in consumer electronics.
Innovation Solution
A low-cost ionic wind engine system using curved micro-springs and associated electrodes, fabricated by existing high-volume IC production methods, generates micro-plasma events to create an air current for effective cooling between circuit structures in semiconductor packages, leveraging Peek's Law for sufficient voltage potential and current crowding to ionize air molecules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If bulky fans are used for cooling high-power ICs, then heat dissipation capability is improved, but device size and weight increase
Solution Approach 1:
The patent replaces the mechanical fan-based forced convection system with an ionic wind generation system that uses electrohydrodynamic forces. High voltage applied to micro-springs creates corona discharge and ionizes air molecules, generating ionic wind that provides cooling without moving mechanical parts, thereby eliminating the need for bulky fans while maintaining heat dissipation capability
Solution Approach 2:
The patent changes the physical state and properties of the cooling medium by ionizing air molecules through corona discharge. By applying high voltage (creating electrical fields sufficient to ionize air), the system transforms ordinary air into an active ionic flow that can be directed for cooling, replacing the need for mechanical air movement while achieving effective heat transfer
2Device complexity
If passive heat management methods are used, then device simplicity is maintained, but effectiveness in 3D stacked chip configurations is insufficient
Solution Approach 1:
The micro-springs are batch-fabricated on the host substrate using stress-engineered thin films that self-bend into curved configurations through built-in stress gradients. This self-actuating mechanism eliminates the need for external mechanical actuators or complex control systems, maintaining structural simplicity while enabling active cooling functionality integrated directly into the package
Solution Approach 2:
The patent combines multiple functions into the micro-spring structure: electrical connection, mechanical compliance, and ionic wind generation. The same curved micro-springs that provide electrical interconnect between stacked chips also serve as the electrode for generating ionic wind, eliminating the need for separate cooling components and maintaining simplicity while improving cooling effectiveness
3Temperature
If wire-based corona discharge is used to generate ionic wind, then cooling capability is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent makes the micro-springs serve dual purposes: as electrical interconnect structures for signal/power transmission between stacked chips and as electrodes for ionic wind generation. This multi-functionality eliminates the need for separate wire-based corona discharge structures, reducing manufacturing complexity and cost while maintaining cooling capability
Solution Approach 2:
The micro-springs are self-formed through batch fabrication processes using stress-engineered thin films that automatically bend into the required curved configurations. This self-organizing behavior eliminates the need for complex assembly steps or precise positioning operations, making the manufacturing process compatible with existing high-volume IC fabrication while enabling ionic wind cooling
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 provides a cost-effective and efficient cooling solution for semiconductor packages by generating an air current that can be used to cool circuit structures, addressing the inefficiencies of traditional cooling methods and being suitable for various semiconductor package assemblies without additional production costs.
Implementation Method 1
By generating a sufficiently large voltage potential (i.e., as determined by Peek's Law, at least 100V, typically greater than 250V), current crowding at the tip portion of the micro-spring creates an electrical field that sufficiently ionizes neutral molecules in a portion of the air-filled region surrounding the tip portion to generate a micro-plasma event.
Implementation Method 2
High electrical field around the emitting electrode ionizes the air molecules. The ions accelerated by electrical field and then transfer momentum to neutral air molecules through collisions.
Implementation Method 3
The ions accelerated by electrical field and then transfer momentum to neutral air molecules through collisions. The resulting micro-scale ionic winds can potentially enhance the bulk cooling of forced convection at the location of a hot spot for more effective and efficient cooling.
Implementation Method 4
The narrow finger-like portions are then released from the host substrate (the anchor portion remains attached to the substrate), whereby the built-in stress causes the finger-like portions to bend (curl) out of the substrate plane with a designed radius of curvature, whereby the tip end of the resulting curved micro-spring is held away from the host substrate.
Data Source
AI summary
An ionic wind engine unit for cooling semiconductor circuit assemblies includes a curved micro-spring and an associated electrode that are maintained apart at an appropriate gap distance such that, when subjected to a sufficiently high voltage potential (i.e., as determined by Peek's Law), current crowding at the spring's tip portion creates an electrical field that sufficiently ionizes neutral molecules in a portion of the air-filled region surrounding the tip portion to generate a micro-plasma event. In one engine type the electrode is a metal pad, and in a second engine type the electrode is a second micro-spring. Ionic wind cooling is generated, for example, between an IC die and a base substrate in a flip-chip arrangement, by controlling multiple engines disposed on the facing surfaces to produce an air current in the air gap region separating the IC device and base substrate.