Flexible Circuit Board Dummy Leads for Thermal Stress Relief
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional flexible circuit boards face issues with inner leads creasing or breaking due to significant temperature variations during flip chip bonding, especially when the space between bumps is large and lacks additional support.
Innovation Solution
Incorporating first and second dummy leads connected to the inner leads and a comb-shaped stress release portion in the circuit layer to provide support and reduce stress concentration, preventing creasing or breaking during thermal compression bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the space between bumps is large with no additional bumps, then the chip design flexibility is improved, but the inner leads are more prone to creasing or breaking due to lack of support
Solution Approach 1:
The patent introduces dummy leads as separate structural elements that segment the large space between bumps into smaller supported zones. These dummy leads divide the unsupported area into multiple sections, each with reduced span, thereby preventing inner leads from creasing or breaking while preserving the original chip design flexibility.
Solution Approach 2:
The dummy leads act as intermediary support structures between the actual bumps. They provide intermediate support points that mediate the mechanical stress distribution across the large gap, preventing direct transmission of thermal stress to the inner leads without requiring changes to the chip bump configuration.
2Reliability
If dummy leads are added to support inner leads, then the reliability of inner leads is improved, but the device complexity increases
Solution Approach 1:
The dummy leads serve multiple functions simultaneously: they provide mechanical support to prevent inner lead damage, act as stress distribution elements during thermal bonding, and can potentially serve as additional electrical connection points. This multi-functionality justifies the added structural elements without proportionally increasing overall device complexity.
Solution Approach 2:
The dummy leads are strategically placed only in specific locations where inner leads require support, rather than uniformly across the entire circuit layer. This localized approach provides necessary reinforcement only where needed, minimizing the overall increase in device complexity while maintaining inner lead integrity in critical areas.
3Ease of manufacture
If the space between bumps is large, then the manufacturing cost is reduced, but the production yield rate decreases due to inner lead damage
Solution Approach 1:
The dummy leads are pre-configured in the circuit layer before the thermal bonding process. This preliminary structural preparation ensures that support is already in place to prevent inner lead damage during the subsequent thermal bonding operation, thereby maintaining high production yield rates while allowing large bump spacing that reduces manufacturing cost.
Solution Approach 2:
The dummy leads provide beforehand cushioning support to the inner leads in the large spaces between bumps. This pre-established support structure cushions against thermal stress and mechanical deformation during bonding, preventing yield-reducing failures while maintaining the cost benefits of large bump spacing.
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 solution effectively protects inner leads from damage, enhancing the production yield rate of flexible circuit boards by providing additional support and stress relief mechanisms.
Implementation Method 1
the stress release portion is connected to the transmission portion, is located between the transmission portion and an edge of the chip, and is a comb-shaped structure
Data Source
AI summary
A layout structure of flexible circuit board includes a flexible substrate, a chip and a circuit layer. A chip mounting area and a circuit area are defined on a top surface of the flexible substrate. The chip is mounted on the chip mounting area, a space exists between a first bump and a second bump of the chip, and there are no additional bumps between the first and second bumps. A first inner lead, a second inner lead, a first dummy lead and a second dummy lead of the circuit layer are located on the chip mounting area. The first and second inner leads are electrically connected to the first and second bumps respectively. The first dummy lead is connected to the first inner lead and adjacent to the first bump, and the second dummy lead is connected to the second inner lead and adjacent to the second bump.