Pad-to-Pad Bonding via Bump-on-Bump Interconnects
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Solution Overview
Problem
Current integrated circuit packaging technologies face challenges with finer bond pad pitches, particularly in pad-to-pad bonding, leading to wire damage and electrical shorts, which are exacerbated by the difficulty in forming reliable connections at pitches of 35 um or less.
Innovation Solution
The implementation of a bump-on-bump connection system using controlled bumps and connectors between them, which eliminates wire damage and shorts by providing structural and signal integrity, and is compatible with existing equipment and technologies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If wire bonding is used for pad-to-pad bonding with fine pitches (35 um or less), then electrical connections can be established, but wire damage and electrical shorts occur
Solution Approach 1:
The wire bonding process is segmented into two distinct stages: first forming a ball bond on the chip pad, then forming a stitch bond on the substrate pad. This segmentation allows each bonding stage to be optimized independently, with the ball bond providing a robust connection point and the stitch bond establishing the final fine-pitch connection, thereby reducing wire damage and shorts
Solution Approach 2:
The ball bond is formed as a preliminary action before the stitch bond. This preliminary ball bond creates a stable anchor point on the chip pad, allowing the subsequent stitch bond to be formed with greater precision and control at the fine pitch required for pad-to-pad bonding, reducing the risk of wire damage and electrical shorts
2Quantity of substance
If finer bond pad pitches are used to increase capacity, then more functions can be integrated, but wire damage and ball deformation increase
Solution Approach 1:
The bonding process is divided into ball bond formation and stitch bond formation as separate, controlled stages. This segmentation allows the system to handle fine pitch requirements (35 um or less) by first establishing a larger ball bond that is less susceptible to deformation, then forming the precise stitch bond connection, thereby maintaining wire and ball integrity while enabling fine pitch integration
Solution Approach 2:
The bonding parameters (such as bonding force, ultrasonic power, and temperature) are optimized differently for the ball bond stage versus the stitch bond stage. This parameter optimization allows reliable bonding at fine pitches without deforming the ball or damaging the wire, enabling higher integration capacity while maintaining manufacturing precision
3Volume of moving object
If pad-to-pad bonding is implemented to reduce form factor, then smaller packaging is achieved, but wire damage and shorts are exacerbated
Solution Approach 1:
The pad-to-pad bonding process is segmented into ball bond and stitch bond stages, with each stage optimized for its specific function. The ball bond creates a robust initial connection that tolerates the constraints of small form factor packaging, while the stitch bond establishes the precise fine-pitch connection needed for compact packaging, thereby achieving small form factor without exacerbating wire damage or shorts
Solution Approach 2:
The ball bond acts as an intermediary element between the chip pad and the substrate pad. This intermediary ball bond provides a stable connection point that facilitates the subsequent stitch bond formation at fine pitch, enabling pad-to-pad bonding in small form factor packages while reducing wire damage and electrical shorts through the mediating ball structure
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 manufacturing yield, improves workability and quality, reduces costs by minimizing gold wire usage, and supports various packaging types such as BGA and SoC, while maintaining compatibility with existing technologies and equipment.
Implementation Method 1
A ball is formed on a tail of the wire, which extends from the end of a capillary of a wire bonder, and is bonded to a bond pad of the chip under pressure by the capillary while heat and/or ultrasonic vibration are applied.
Implementation Method 2
The capillary deforms the wire against a bond position of the substrate, producing a wedge-shaped stitch bond.
Data Source
AI summary
An integrated circuit package system includes an integrated circuit die, a first controlled bump over the integrated circuit die, a second controlled bump over the integrated circuit die, and a connector between the first controlled bump and the second controlled bump.