Nanoparticle Joining for Microelectronic Package Thickness Reduction
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Solution Overview
Problem
The challenge in microelectronic packaging is to achieve uniform and reliable interconnections between semiconductor chips and substrates with high contact density, where the reduced size of solder joints and increased thermal expansion differences complicate the formation of uniform metal columns and underfill structures, leading to issues with joint reliability and package thickness.
Innovation Solution
The method involves applying metallic nanoparticles to the conductive elements of microelectronic components, juxtaposing them, and elevating the temperature to form metallurgical joints, which allows for the creation of conductive posts with precise dimensions and reliable interconnections, even at high contact densities, using metals like gold, tin, and copper.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If solder volume is reduced to accommodate high contact density, then contact density is improved, but joint reliability deteriorates
Solution Approach 1:
The patent changes the material parameters by using nanoparticle paste instead of conventional solder, and controls the sintering temperature parameter to form reliable joints at lower temperatures (e.g., 150-200°C) without requiring large solder volumes, thus maintaining joint reliability while accommodating high contact density
Solution Approach 2:
The patent uses composite nanoparticle paste materials containing metal nanoparticles (e.g., silver, copper, or tin nanoparticles) suspended in a vehicle, which provide both the necessary flowability for placement and the sintering properties for forming reliable electrical and mechanical connections at reduced volumes
2Adaptability or versatility
If stand-off height is increased to allow underfill and thermal compensation, then adaptability is improved, but package thickness increases
Solution Approach 1:
The patent reduces the required stand-off height by changing the joining material properties to nanoparticle paste, which can form reliable connections at smaller heights (e.g., 10-50 microns compared to conventional solder heights), thereby reducing package thickness while still allowing for underfill and thermal expansion compensation
Solution Approach 2:
The patent enables the underfill to flow in the lateral dimension more effectively by reducing the vertical stand-off height requirement, allowing the underfill material to properly compensate for thermal expansion in the planar direction without requiring excessive vertical space
3Manufacturing precision
If electroplating is used to form metal columns, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts the complex electroplating process and replaces it with a simpler nanoparticle paste application and sintering process, removing the need for photoresist masking, electroplating equipment, and complex process control while achieving sufficient column uniformity through the self-leveling properties of the paste
Solution Approach 2:
The patent replaces the expensive and complex electroplating process with a cheaper nanoparticle paste application method that uses disposable paste materials, eliminating the need for expensive plating equipment and complex process infrastructure
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 formation of reliable and uniform interconnections with improved joint reliability and reduced package thickness, accommodating differential thermal expansion while maintaining positional stability and planarity of the conductive posts.
Implementation Method 1
elevating a temperature at least at interfaces of the juxtaposed conductive elements to a joining temperature at which the metallic nanoparticles cause metallurgical joints to form between the juxtaposed conductive elements
Implementation Method 2
elevating a temperature at least at interfaces of the juxtaposed conductive elements to a joining temperature at which the metallic nanoparticles cause metallurgical joints to form
Data Source
AI summary
A method of making an assembly includes the steps of applying metallic nanoparticles to exposed surfaces of conductive elements of either of or both of a first component and a second component, juxtaposing the conductive elements of the first component with the conductive elements of the second component with the metallic nanoparticles disposed therebetween, and elevating a temperature at least at interfaces of the juxtaposed conductive elements to a joining temperature at which the metallic nanoparticles cause metallurgical joints to form between the juxtaposed conductive elements. The conductive elements of either of or both of the first component and the second component can include substantially rigid posts having top surfaces projecting a height above the surface of the respective component and edge surfaces extending at substantial angles away from the top surfaces thereof.