IC package with connection pads for die
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Solution Overview
Problem
The formation of reliable solder joints between the die and the interconnect in IC packages is challenging due to cracking, which leads to failure of the IC package.
Innovation Solution
The introduction of cavity pillars with recesses and pillars on the connection pads of the interconnect, formed using copper, which facilitate the flow of solder and provide mechanical resistance to thermal expansion, thereby enhancing the reliability of solder joints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional flat connection pads are used for mounting the die, then the manufacturing process is simple, but the solder joints are prone to cracking under thermal expansion stress
Solution Approach 1:
The connection pad surface is segmented into multiple cavity pillars distributed across the pad area. Each cavity pillar consists of a recess with a central pillar, creating discrete stress distribution points rather than a continuous flat surface. This segmentation allows the solder to form multiple localized bonds that independently accommodate thermal expansion, preventing crack propagation across the entire joint.
Solution Approach 2:
The cavity pillars create a porous-like structure on the connection pad surface with recesses that can be filled with solder material. This porous configuration increases the effective bonding area and allows the solder to penetrate and anchor into the recesses, creating a mechanically interlocked joint that resists cracking while maintaining manufacturing feasibility through standard electroplating processes.
2Strength
If the interconnect provides mechanical stability and heat dissipation, then the IC package structure is robust, but thermal expansion causes stress concentration at the solder joints
Solution Approach 1:
The cavity pillars are specifically designed to accommodate thermal expansion differences between the die, interconnect, and solder materials. The recesses in the cavity pillars provide compliance space that allows the solder to deform elastically during thermal cycling without generating excessive stress. The central pillars within each cavity provide anchoring points that distribute thermal stress uniformly across the connection pad surface, preventing stress concentration at any single location.
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 cavity pillars reduce the likelihood of crack propagation and delamination, improving the structural integrity and electrical performance of the IC package by distributing stress and strain caused by thermal expansion.
Implementation Method 1
A portion of the solder bumps flow over the cavity pillars
Implementation Method 2
provide mechanical resistance to thermal expansion, thereby enhancing the reliability of solder joints
Implementation Method 3
distributing stress and strain caused by thermal expansion
Implementation Method 4
formed using copper, which facilitate the flow of solder and provide mechanical resistance to thermal expansion
Data Source
AI summary
An IC (integrated circuit) package includes a first interconnect. The first interconnect includes a first surface comprising connection pads. The connection pads include cavity pillars on the first surface and the cavity pillars include a recess in the first surface with a pillar in a center region of a respective cavity pillar. The first interconnect includes a second surface opposing the first surface having connection pads for leads. The IC package includes a second interconnect with the leads mounted on the connection pads of the second surface of the first interconnect. The IC package also includes a die mounted with solder bumps on the connection pads of the first surface of the first interconnect. A portion of the solder bumps flow over the cavity pillars.