Flexible Circuit Board Comb-Shaped Stress Release Structure
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Solution Overview
Problem
Conventional flexible circuit boards face stress concentration and damage during thermal bonding due to differing thermal expansion behaviors of the flexible substrate and circuit layer, which can lead to breakage of the circuit layer around the chip.
Innovation Solution
A comb-shaped stress release portion is integrated between the transmission portion and the second side of the chip mounting area on the flexible circuit board, mitigating stress concentration and protecting the connection portion from damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If a patterned circuit layer is arranged on a flexible substrate with high circuit line density and narrow width, then the circuit board can be used in smaller-size electronic equipment, but stress concentration and damage occur on the circuit layer around the chip during thermal bonding
Solution Approach 1:
The circuit layer is segmented into functional portions: a connection portion extending into the chip mounting area, a transmission portion in the circuit area, and a stress release portion with comb-shaped structure. This segmentation allows each portion to perform its specific function while the stress release portion protects the connection portion from thermal stress during bonding
Solution Approach 2:
The stress release portion acts as an intermediary element between the transmission portion and the chip mounting area. It absorbs and redistributes thermal stress that arises during chip bonding, preventing direct stress transmission to the connection portion and protecting the circuit layer integrity
2Device complexity
If the circuit layer is disposed close to the chip mounting area for compact design, then the circuit board size is reduced, but stress concentration causes breakage of the connection portion
Solution Approach 1:
The circuit layer exhibits local quality variations through its different portions: the connection portion has narrow width for high density, the transmission portion has appropriate width for signal transmission, and the stress release portion has comb-shaped structure with specific geometry. Each portion's local structure is optimized for its specific function and stress conditions
Solution Approach 2:
The stress release portion is designed beforehand as a protective structure between the transmission portion and chip mounting area. Its comb-shaped geometry is预先 configured to absorb and distribute thermal stress that will occur during chip bonding, cushioning the connection portion from stress concentration before it can cause damage
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 stress release portion effectively reduces stress on the circuit layer, enhancing the manufacturing yield rate of flexible circuit boards by preventing breakage and ensuring reliable signal transmission.
Implementation Method 1
the different thermal expansion behavior of the flexible substrate and the circuit layer during thermal bonding of the chip to the circuit layer on the flexible substrate may cause stress concentration and damage on the circuit layer around the chip
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 circuit area surrounds the chip mounting area. The chip is mounted on the chip mounting area of the top surface and includes a bump. The circuit layer is disposed on the top surface. A connection portion of the circuit layer extends across a first side of the chip mounting area and into the chip mounting area. A transmission portion of the circuit layer is located on the circuit area and electrically connected to the connection portion. A stress release portion of the circuit layer is located between the transmission portion and a second side of the chip mounting area and is a comb-shaped structure.