Flexible Microsystem Trenches for Thermal Stress Relief
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Flexible microsystem structures face thermal stress issues during bonding, leading to inflatedness, bending, and curling due to the difference in thermal expansion coefficients between the flexible substrate and the chip, which affects their structural integrity and functionality.
Innovation Solution
Incorporating trenches along the sides of bonding elements on the flexible substrate to alleviate thermal stress, which can be formed using methods like laser cutting, photolithography, and etching, and optionally through-holes to further reduce stress and maintain structural stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the flexible substrate is heated to bond the chip, then the bonding strength is improved, but thermal stress causes inflatedness, bending and curving of the substrate
Solution Approach 1:
The flexible substrate is segmented by forming trenches around the bonding elements, dividing the continuous substrate into isolated regions. This segmentation allows different parts of the substrate to undergo independent thermal expansion and contraction, preventing cumulative stress that would cause global deformation. The trenches create isolated stress zones that contain local thermal stress without propagating it across the entire substrate surface.
Solution Approach 2:
The substrate structure is modified locally by adding trenches specifically around the bonding elements where thermal stress is most concentrated. This local modification allows the substrate to maintain its original properties in most areas while providing stress relief precisely where needed during the heating process, enabling differential thermal management across the substrate surface.
2Ease of manufacture
If the flexible substrate is heated to bond the chip, then the bonding process is completed, but thermal stress reduces the structural integrity of the substrate
Solution Approach 1:
The substrate is divided into isolated regions by trenches surrounding each bonding element. This segmentation prevents thermal stress from propagating through the entire substrate structure, containing stress within localized zones. As a result, the substrate maintains its overall structural integrity even after repeated heating cycles during bonding processes.
Solution Approach 2:
The trenches are formed in advance before the bonding process, creating predetermined stress relief pathways. This prior preparation allows the substrate to accommodate thermal stress during subsequent heating operations without compromising structural integrity, effectively cushioning against potential damage before it occurs.
3Device complexity
If traditional bonding methods are used without trenches, then the manufacturing process is simpler, but thermal stress causes deformation and reduces reliability
Solution Approach 1:
The substrate structure is segmented by adding trenches around bonding elements, which can be formed using standard photolithography and etching processes. This segmentation approach maintains compatibility with existing manufacturing workflows while significantly improving substrate reliability by preventing thermal stress-induced deformation during bonding operations.
Solution Approach 2:
Rather than fundamentally changing the entire manufacturing process, the invention applies a localized structural modification (trenches) to specific areas around bonding elements. This local quality approach minimizes the increase in manufacturing complexity while effectively addressing the thermal stress reliability issue.
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 trenches effectively reduce thermal stress-induced deformation, enhancing the structural stability and reliability of flexible microsystem structures by managing thermal expansion differences between the substrate and the chip.
Implementation Method 1
thermal stress can result in inflatedness, bending and curving of the flexible substrate after the flexible substrate is bonded to the chip
Data Source
AI summary
A flexible microsystem structure is provided. The flexible microsystem structure includes a flexible substrate; and a chip disposed over the flexible substrate, wherein the chip is bonded to the flexible substrate by a plurality of bonding elements disposed over the flexible substrate; wherein the flexible substrate has at least one trench disposed under the chip and disposed along at least one side of at least one of the bonding elements.