Copper Ball Bond Aluminum Splash Control
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Solution Overview
Problem
Conventional ball bonding processes for semiconductor devices, particularly with copper ball bonds on aluminum pads, face mechanical integrity issues such as cracks and mold compound penetration due to stressors like impact force and pressure, leading to reliability concerns during device operation and testing.
Innovation Solution
The method involves controlling bonding parameters to form aluminum splash features with specific geometric structural requirements, including lateral splash size, shape, crevice width, length, and angle, ensuring the splash extends around the ball bond perimeter with minimal crevice length and width, and positioning the splash above the pad to prevent mold compound penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ball bonding processes are used with copper ball bonds on aluminum pads, then the bonding process can be completed, but mechanical integrity problems such as cracks and mold compound penetration occur due to stressors like impact force and pressure
Solution Approach 1:
The patent applies parameter changes by precisely controlling bonding parameters (ultrasonic power, bonding force, bonding time, temperature) to form aluminum splash features with specific geometric characteristics. This control transforms the bonding process to create a reliable bond interface without cracks or penetration, resolving the mechanical integrity problem while maintaining processability
Solution Approach 2:
The patent creates local quality differences by forming aluminum splash features with specific geometric properties at the bond interface. The splash features have controlled lateral dimensions, heights, and crevice characteristics that locally enhance mechanical integrity at the critical bond interface, preventing cracks and mold compound penetration while maintaining overall bond reliability
2Ease of manufacture
If copper ball bonds are used instead of gold ball bonds, then cost is reduced, but the process window becomes narrower leading to increased reliability concerns
Solution Approach 1:
The patent addresses the narrower process window of copper ball bonds by implementing precise parameter control during bonding. By controlling ultrasonic power, bonding force, temperature, and time parameters, the process creates consistent aluminum splash features that ensure reliable bonding despite copper's narrower process window, enabling cost-effective manufacturing with maintained reliability
Solution Approach 2:
The patent partially replaces mechanical bonding approaches with ultrasonic vibration energy to achieve reliable copper ball bonding. The ultrasonic energy facilitates bond formation with reduced mechanical pressure, accommodating copper's narrower process window while maintaining bond reliability and enabling cost reduction compared to gold bonding
3Area of stationary object
If the splash extends beyond the ball bond perimeter, then coverage is improved, but crevice length increases allowing mold compound penetration
Solution Approach 1:
The patent resolves this contradiction by precisely controlling bonding parameters to create aluminum splash features with optimized geometric characteristics. The splash extends laterally to provide adequate coverage around the ball bond perimeter while maintaining controlled crevice dimensions (width and length) that prevent mold compound penetration, achieving both coverage and protection
Solution Approach 2:
The patent creates local quality variations in the aluminum splash structure, with elevated portions providing coverage and controlled crevice regions preventing penetration. The splash features have specific geometric properties at different locations - lateral extension for coverage but constrained vertical and horizontal dimensions at critical interfaces to prevent mold compound ingress
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 enhances the reliability of copper ball bonds by minimizing crevice penetration and maintaining mechanical integrity, thereby improving the durability and performance of semiconductor devices under stress tests.
Implementation Method 1
conventional ball bonding processes typically use a combination of heat, pressure and ultrasonic energy to form an intermetallic connection or weld between a wire and a connection pad
Implementation Method 2
conventional ball bonding processes typically use a combination of heat, pressure and ultrasonic energy to form an intermetallic connection or weld
Implementation Method 3
conventional ball bonding processes typically use a combination of heat, pressure and ultrasonic energy to form an intermetallic connection or weld
Data Source
AI summary
An integrated circuit wire bond connection is provided having an aluminum bond pad (51) that is directly bonded to a copper ball (52) to form an aluminum splash structure (53) and associated crevice opening (55) at a peripheral bond edge of the copper ball (54), where the aluminum splash structure (53) is characterized by a plurality of geometric properties indicative of a reliable copper ball bond, such as lateral splash size, splash shape, relative position of splash-ball crevice to the aluminum pad, crevice width, crevice length, crevice angle, and/or crevice-pad splash index.