Rigid Trackpad Lamination Using Segmented Adhesive System
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Solution Overview
Problem
Existing laminated structures for electronic devices, such as trackpads, face challenges in achieving a balance between rigidity, flatness, and minimal thickness, with conventional adhesives either compromising on flatness for stiffness or vice versa, and often resulting in inconsistent thickness and thermal mismatch issues.
Innovation Solution
A laminated structure using a combination of room-temperature-activated liquid adhesive, cured adhesive as a spacing component, and pressure-sensitive adhesive (PSA) as an alignment-holding component, which maintains spacing and alignment during bonding, ensuring a stiff, flat, and uniformly thick laminate stack.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional adhesives are used to bond layers, then the laminate stack achieves stiffness, but flatness and thickness uniformity are compromised
Solution Approach 1:
The adhesive system is segmented into three distinct components: bonding component (for stiffness), spacing component (for thickness control), and alignment-holding component (for flatness). Each component performs a specific function, allowing the laminate to achieve stiffness without compromising flatness or thickness uniformity.
Solution Approach 2:
The patent changes the physical state parameters of the adhesive system by using a curable adhesive that transitions from liquid (easy to apply and distribute uniformly) to cured state (provides stiffness). This parameter change allows the adhesive to provide bonding strength while maintaining flatness and thickness control during the curing process.
2Volume of moving object
If the laminate stack is made thinner, then the device profile is improved, but structural rigidity is compromised
Solution Approach 1:
The patent uses a composite adhesive system combining three different adhesive components with complementary properties. The bonding component provides structural rigidity, while the spacing and alignment-holding components ensure uniform thickness distribution, allowing the laminate to be thin yet rigid.
Solution Approach 2:
The adhesive system provides localized functionality: the bonding component is distributed throughout to provide overall stiffness, while the spacing component is positioned at specific locations to maintain thickness, and the alignment-holding component is applied at edges to maintain flatness during bonding.
3Strength
If adhesive is applied to ensure coverage, then bonding strength is improved, but thickness consistency and flatness deteriorate
Solution Approach 1:
The adhesive application is segmented into functional zones: spacing components are positioned at specific locations to control thickness, alignment-holding components are applied at edges to maintain flatness during bonding, and the bonding component is distributed in the remaining areas to provide coverage and strength without compromising precision.
Solution Approach 2:
The spacing and alignment-holding components are applied in advance to establish the geometric framework (spacing and alignment) before the bonding component is applied. This preliminary action ensures that when full adhesive coverage is achieved, thickness consistency and flatness are already established.
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 achieves a stiff and flat laminated structure with minimal thickness, preventing capacitance variations and enabling larger yet thinner trackpads with improved mechanical properties and uniform thickness, addressing the limitations of existing adhesive systems.
Implementation Method 1
A first layer component or substrate is coupled to a second layer component or substrate by an adhesive system including a bonding component
Implementation Method 2
The cured liquid adhesive has a higher stiffness than the alignment-holding component
Data Source
AI summary
A laminated stack, such as a trackpad, is assembled by coupling components using an adhesive system. Assembly of the laminated stack includes forming an adhesive-spacing component on a first substrate, forming an adhesive-alignment-holding component on the first substrate in a perimeter around the adhesive-spacing component, forming a bonding component by filling an area within the perimeter with liquid adhesive, and bonding the first substrate to a second substrate by curing the bonding component. The first substrate and the second substrate may each be one of a touch-sensing component and a cover component. The adhesive-spacing component maintains a space between the first substrate and the second substrate while the bonding component cures. The adhesive-alignment-holding component maintains alignment of the first substrate and the second substrate while the bonding component cures.