Flexible Circuit Anchor Structures for Tight Bend Stress Reduction
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Solution Overview
Problem
The challenge lies in securing flexible circuits around tight bends without increasing residue stress, which can lead to broken connections or delamination, especially in microfluidics where environmental factors like corrosion are prevalent, and there is a need for more reliable and cost-effective materials and manufacturing processes to accommodate the demand for smaller, lighter, and more complex electronic devices.
Innovation Solution
The use of anchor structures within the flexible circuit, such as recessed regions or through holes, to create a strong adhesive bond when the circuit is bent over a die carrier, utilizing various adhesives and flexible circuit structures, including adhesiveless and symmetrical/asymmetrical designs, to enhance mechanical strength and reduce stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If flexible circuits are bent around tight bends to reduce device size, then device compactness is improved, but residue stress increases leading to broken connections or delamination
Solution Approach 1:
The patent applies preliminary action by forming anchor structures (recesses or through-holes) in the flexible circuit substrate before bending the circuit around tight bends. These pre-formed structures create mechanical interlocking with adhesive that strengthens the bond and reduces residue stress during subsequent bending operations, preventing delamination and broken connections while maintaining compact device size.
2Volume of moving object
If tighter bends are generated in flexible circuits to reduce device size, then device compactness is improved, but the difficulty in reliably securing the flexible circuit increases
Solution Approach 1:
The patent applies local quality by creating localized anchor structures (recesses or through-holes) at specific locations where the flexible circuit will be secured. These localized features provide enhanced adhesive bonding strength precisely where needed, improving securing reliability in tight bend areas without affecting the overall flexibility or requiring changes to the entire circuit structure.
3Shape
If increased stress is present in flexible circuits, then tighter bends can be achieved, but broken circuit connections or delamination occurs leading to degradation
Solution Approach 1:
The patent applies preliminary action by pre-forming anchor structures in the flexible circuit substrate before applying adhesive and performing bending operations. These pre-formed structures create mechanical interlocking that distributes and reduces stress concentrations, allowing tight bends to be achieved while preventing broken connections and delamination through enhanced bond strength at critical locations.
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
This approach provides a robust adhesive bond with lower-cost adhesives, allowing for the use of more brittle materials and reducing stress on the flexible circuit, thereby improving reliability and flexibility, particularly in applications like microfluidics and inkjet printheads.
Implementation Method 1
The adhesive bond strength between the adhesive and the flexible circuit material, in the region of the tight static bend, is at least partially a function of the cohesive strength of the adhesive utilized to form the cleat like structure.
Data Source
AI summary
A method of using a flexible circuit, including attaching a first portion of the flexible circuit, via an attaching surface of the flexible circuit, to a first surface of a chip carrier. Statically bending a bending portion of the flexible circuit around an edge formed at the intersection of the first surface of the chip carrier, and a second surface of the chip carrier. Adhesively attaching a second portion of the flexible circuit, via the attaching surface, to the second surface of the chip carrier, where the second portion of the flexible circuit has at least one first anchor structure formed in the attaching surface, where the at least one first anchor structure is adapted to accept an adhesive.