Segmented Metal Trace Support for Stacked IC Delamination
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Solution Overview
Problem
Stacked integrated circuit chips are prone to delamination due to thermal expansion of the top metal layer on printed circuit boards during the die attach process, especially in bridge configurations, leading to catastrophic reliability failures.
Innovation Solution
The use of a top metal layer with equally spaced, thin metal traces instead of a contiguous metal plate provides structural support while minimizing thermal expansion, preventing delamination by dissipating heat quickly and reducing stress on the die stack.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a contiguous metal plate is used in the top metal layer, then structural support for the die stack is provided, but thermal expansion during die attach causes delamination
Solution Approach 1:
The top metal layer is segmented into multiple equally spaced metal traces instead of using a contiguous metal plate. This segmentation reduces the overall thermal mass and allows for differential thermal expansion, preventing the formation of large-scale voids that cause delamination while still providing adequate structural support through the distributed trace pattern.
2Ease of manufacture
If high temperatures are applied during die attach, then proper bonding is achieved, but thermal expansion of the metal layer creates voids in the die attach film
Solution Approach 1:
The metal layer is divided into separate traces that can expand and contract independently during thermal processing. This segmentation allows the die attach process to proceed at high temperatures while preventing the formation of large voids, as the distributed trace structure accommodates thermal expansion more uniformly.
3Adaptability or versatility
If a bridge die stack configuration is used, then specific functional requirements are met, but the structure is more vulnerable to delamination failure
Solution Approach 1:
The segmented metal trace pattern provides distributed support that is particularly beneficial for bridge die stack configurations. The traces are positioned to provide enhanced support at critical locations while allowing the bridge structure to maintain its functional configuration without being overly vulnerable to delamination.
Solution Approach 2:
The metal traces are strategically positioned and dimensioned to provide localized support where the bridge die stack configuration is most vulnerable. This local quality approach ensures that the traces provide maximum support where needed while maintaining the overall bridge configuration functionality.
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 solution effectively prevents delamination of the die stack during thermal processing, ensuring the electrical integrity and reliability of the package, as confirmed by statistical distributions and micrograph analysis, with no compromise in electrical functionality.
Implementation Method 1
the top metal layer with equally spaced, thin metal traces instead of a contiguous metal plate provides structural support while minimizing thermal expansion, preventing delamination by dissipating heat quickly
Data Source
AI summary
Delamination of stacked integrated circuit die configurations on printed circuit boards is avoided by providing a metal trace support structure underneath the die stack. The metal trace support structure features substantially equally spaced thin metal traces in place of a contiguous metal plate which has been used in the past. Spaced apart thin metal traces are less vulnerable to thermal expansion than a metal plate which has a large thermal mass. The metal traces still provide structural stability, while preventing delamination of the die stack configuration during thermal processing. A method of attaching a bridge die stack configuration to a printed circuit board by adhering a die attach film to a field of metal traces is demonstrated. In addition, the electrical and structural integrity of the bridge die stack formed with a metal trace support structure is confirmed with test results.