Foamed Sheet Impact Absorption via Viscoelastic Tuning
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Solution Overview
Problem
Conventional foamed materials fail to provide sufficient impact absorption when reduced to small thicknesses, leading to increased risk of failure in electronic devices upon drop impacts, and they often require adhesive layers for lamination, which adds thickness and complexity.
Innovation Solution
A foamed sheet with a specific density of 0.2 to 0.7 g/cm³ and average cell diameter of 10 to 150 µm, featuring a peak top of loss tangent occurring between -30°C to 30°C, which enhances impact absorption and allows for adhesive-free lamination with other members, reducing device thickness and complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the thickness of foamed materials is reduced to meet decreasing clearances in electronic devices, then the device thickness is reduced, but the impact absorption capability becomes insufficient
Solution Approach 1:
The patent applies parameter changes by optimizing the density range (0.2-0.7 g/cm³) and average cell diameter range (10-150 µm) of the foamed sheet to achieve excellent impact absorption even at reduced thicknesses of 30-500 µm. This resolves the contradiction by finding the optimal parameter combination that maintains protective functionality while reducing overall thickness.
Solution Approach 2:
The patent utilizes porous foamed materials with specifically controlled cell structures (average cell diameter 10-150 µm) to achieve high impact absorption efficiency at thin sections. The porous structure allows the material to dissipate impact energy effectively through cell deformation and air compression, maintaining reliability while reducing thickness.
2Reliability
If adhesive layers are added to laminate the shock absorbing sheet with other members, then the lamination reliability is improved, but the overall device thickness increases
Solution Approach 1:
The foam material performs dual functions: it provides shock absorption and simultaneously serves as its own adhesive through direct bonding to other members. This self-service capability eliminates the need for separate adhesive layers, maintaining lamination reliability while reducing overall device thickness.
Solution Approach 2:
The foamed sheet is designed to be multi-functional, serving both as a shock-absorbing element and as a bonding/adhesive layer. This universality allows it to replace traditional separate components (shock absorber + adhesive), thereby reducing the number of layers and overall device thickness while maintaining both impact protection and lamination reliability.
3Length of stationary object
If adhesive layers are removed to reduce device thickness, then the device thickness is reduced, but misregistration upon lamination occurs
Solution Approach 1:
The foam material bonds directly to other members without requiring separate adhesive layers, achieving both thickness reduction and precise registration. The direct bonding capability of the foam eliminates misregistration issues that typically occur when adhesive layers are removed, as the foam itself provides the bonding interface.
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 foamed sheet effectively absorbs impacts and prevents device failure at reduced thicknesses without the need for adhesive layers, ensuring reliable performance and reduced thickness in electronic devices.
Implementation Method 1
the loss tangent (tan δ) is defined as the ratio of a loss modulus to a storage modulus determined at an angular frequency of 1 rad/s in dynamic viscoelastic measurement of the foam
Implementation Method 2
when the electrical/electronic devices are dropped off typically onto the ground, the foamed sheets absorb impacts upon collision with the ground
Data Source
Figure 1~2
AI summary
A foamed sheet according to the present invention has a thickness of 30 to 500 µm and includes a foam. The foam has a density of 0.2 to 0.7 g/cm3, an average cell diameter of 10 to 150 µm, and a peak top of loss tangent (tan δ) occurring in a temperature range of from -30°C to 30°C, where the loss tangent is defined as the ratio of a loss modulus to a storage modulus determined at an angular frequency of 1 rad/s in dynamic viscoelastic measurement of the foam. The foam preferably has a maximum of the loss tangent (tan δ) in the temperature range of from -30°C to 30°C of 0.2 or more.