Pre-fabricated Metal Posts for IC Packaging Stress Absorption
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Solution Overview
Problem
The bonding of integrated circuit device dies to package substrates using solder regions or copper pillars is hindered by warpage and thermal stresses due to differing Coefficients of Thermal Expansion (CTE), leading to dielectric delamination, and existing metal post bonding processes have low throughput and poor uniformity.
Innovation Solution
Pre-fabricated metal posts, formed using a metal film and etching process with plated end portions for improved bondability, are used to absorb stress and are efficiently bonded to package components using a capillary system, eliminating the need for time-consuming cutting actions and allowing simultaneous bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal posts are formed by bonding and cutting metal wires, then stress absorption is improved, but throughput deteriorates and length uniformity deteriorates
Solution Approach 1:
Metal posts are pre-formed with predetermined lengths through efficient processes like etching and rolling before bonding. This preliminary fabrication eliminates the time-consuming cutting step during bonding, thereby improving throughput while maintaining uniform length and stress absorption capabilities
Solution Approach 2:
The cutting operation is extracted and eliminated from the bonding process by pre-fabricating metal posts to the exact required lengths. This separation of operations allows the bonding process to focus solely on joining, significantly improving throughput without compromising the stress absorption function
2Reliability
If metal posts are formed by bonding and cutting metal wires, then stress absorption is improved, but manufacturing precision deteriorates
Solution Approach 1:
Metal posts are pre-formed with predetermined lengths through efficient processes like etching and rolling before bonding. This preliminary fabrication eliminates the time-consuming cutting step during bonding, thereby improving throughput while maintaining uniform length and stress absorption capabilities
Solution Approach 2:
The manufacturing method transitions from mechanical cutting (which causes variability) to controlled processes like etching and rolling that produce metal posts with predetermined, uniform lengths. This parameter change in the fabrication approach directly improves length uniformity while preserving stress absorption
3Device complexity
If traditional bonding processes are used, then process simplicity is maintained, but bond quality deteriorates due to warpage and thermal stress
Solution Approach 1:
Plated end portions are applied to specific locations (ends) of the metal posts to enhance bondability at the bonding interfaces. This localized treatment improves bond quality without complicating the overall process, as only the endpoint regions require plating while the post bodies remain simple
Solution Approach 2:
The metal posts combine different materials or coatings (base metal post material plus plated end portions) to achieve both stress absorption and enhanced bondability. This composite structure improves bond quality while maintaining process efficiency
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
The pre-fabricated metal posts effectively absorb thermal stresses, improve bond quality, and increase throughput by enabling simultaneous bonding and uniformity, reducing dielectric delamination and enhancing the packaging process efficiency.
Implementation Method 1
Pre-fabricated metal posts with plated end portions are used
Implementation Method 2
The metal posts are longer than typical solder regions and metal pillars, and hence may absorb the stress
Data Source
AI summary
A method includes forming a plurality of metal posts. The plurality of metal posts is interconnected to form a metal-post row by weak portions between neighboring ones of the plurality of metal posts. The weak portions include a same metal as the plurality of metal posts. A majority of each of the plurality of metal posts is separated from respective neighboring ones of the plurality of metal posts. An end portion of each of the plurality of metal posts is plated with a metal. The plurality of metal posts is disposed into a metal post-storage. The method further includes retrieving one of the metal posts from a metal-post storage, and bonding the one of the metal posts on a metal pad.