Regional Stiffness Reduction Using Lamina Emergent Torsional Joints for Flexible Printed Circuit Board Design

DeFigueiredo, Bryce P.; Zimmerman, Trent K.; Russell, Brian D.; Howell, Larry L.

doi:10.1115/1.4040552

Cited by 14 publications

(4 citation statements)

References 35 publications

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“…Previous risk assessment findings on the escape defects from unknown FPC suppliers of a flexible printed circuit board (FPCB) for smartphones showed a defective rate between 1.50% and 4.99%, but failure modes can be detected by operators' self-check [10]. The two main failure modes for flexible electronic devices are crack propagation and delamination, which are generally more common in the conductive layer than in the polyimide structure [11].…”

Section: Introductionmentioning

confidence: 99%

DSC Assessment on Curing Degree of Micron-scaled Adhesive Layer in Lamination-pressed Flexible Printed Circuit Panels

Kok¹,

Lau²,

Rosli³

2021

JMechE

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Continuous monitoring and optimisation of the lamination process are critical in negating flexible printed circuit (FPC) delamination risk during operation. The main QC inspection criterion of the lamination adhesive’s curing degree is adhesive thickness. However, this method is prone to measurement error due to poor microscopy image definition and the inspector’s measurement parallax error. The feasibility of using thermal characterisation to measure the difference in curing degrees of micron-scaled adhesive layer of laminated FPC was investigated. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used according to IPC standards. Polyimide-epoxy adhesive coverlays were laminated onto both sides of FPC at 120 kgf/cm2 pressure and 180 °C temperature for 120 s. Then, the coverlays were subjected to oven curing at 150 °C for 60 min. The DSC detected a small difference in the curing degree of adhesive layers in the two cured FPC laminated in different laminating-press openings (T1 and T2). T2 had a glass transition temperature (Tg) of 106.5 °C, which was higher than that for T1 (105 °C), thereby suggesting that the former had a higher curing degree than the latter. This result was consistent with the adhesive thickness measurement result of the DSC samples. The adhesive thickness of T2 was smaller (30.97 µm) than that of the T1 (31.76 µm). T2 had a higher curing degree than T1 because of the larger shrinkage percentage. In comparison with DSC, TGA was unable to detect the curing degree difference between the samples because of the undetected weight loss resulting from the adhesive curing.

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Section: Introductionmentioning

confidence: 99%

DSC Assessment on Curing Degree of Micron-scaled Adhesive Layer in Lamination-pressed Flexible Printed Circuit Panels

Kok¹,

Lau²,

Rosli³

2021

JMechE

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“…Systems of panels and low-footprint joint designs are beneficial for applications where the function of the panels depends on the panel size. This feature can be used to create networks of monolithic panels and joints to obtain desired motions and functions (e.g., deployable devices [23][24][25], printed circuit boards [26], and actuation origami [27][28][29]).…”

Section: Introductionmentioning

confidence: 99%

Load–Displacement Characterization in Three Degrees-of-Freedom for General Lamina Emergent Torsion Arrays

Pehrson

Bilancia

Magleby

et al. 2020

Journal of Mechanical Design

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Lamina emergent torsion (LET) joints for use in origami-based applications enables folding of panels. Placing LET joints in series and parallel (formulating LET arrays) opens the design space to provide for tunable stiffness characteristics in other directions while maintaining the ability to fold. Analytical equations characterizing the elastic load–displacement for general serial–parallel formulations of LET arrays for three degrees-of-freedom are presented: rotation about the desired axis, in-plane rotation, and extension/compression. These equations enable the design of LET arrays for a variety of applications, including origami-based mechanisms. These general equations are verified using finite element analysis, and to show variability of the LET array design space, several verification plots over a range of parameters are provided.

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“…In the light of resolving the LEM's challenges, RUFF and TUFF flexure hinges were investigated [22]. To expand the family of lamina emergent torsional (LET) joints, researchers developed LET joints with a large displacement such as ODLET [23], LET array for circuit board product [24], and spatial LET joints [25,26]. In order to analyze behaviors of a LEM's flexure hinges, several methods have been developed, including the closed-form model [24], compliance matrix method [25,27,28], semianalytic model [29], finite element method [30], and pseudorigid-body model [31].…”

Section: Introductionmentioning

confidence: 99%

“…To expand the family of lamina emergent torsional (LET) joints, researchers developed LET joints with a large displacement such as ODLET [23], LET array for circuit board product [24], and spatial LET joints [25,26]. In order to analyze behaviors of a LEM's flexure hinges, several methods have been developed, including the closed-form model [24], compliance matrix method [25,27,28], semianalytic model [29], finite element method [30], and pseudorigid-body model [31]. Besides, researches proposed advanced analytical methods to model a nonlinear relation of load versus displacement, e.g., analytical models for spatial compliant parallel modules [32], a simplified pseudo-rigidbody model method for spatial multibeam modules [33], position-and space-based design of a symmetric spatial compliant mechanism [34], nonlinear kinetostatic modelling for parallel manipulator [35], and normalization-based approach [36].…”

Section: Introductionmentioning

confidence: 99%

Design and Performance Analysis of a TLET‐Type Flexure Hinge

Chau

Tran

Dao

2020

Advances in Materials Science and Engineering

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In order to permit a large deflection, three lamina emergent torsional flexure hinges are reconfigured to create a new triple LET-type flexure hinge (TLET) in this paper. The TLET consists of flexure hinges in a series coupled with others in parallel configuration. This arrangement is aimed to enhance the displacement of the joint. The proposed joint is capable of generating a large displacement and a large capacity of load within safety working conditions. The closed-form models are derived to calculate the equivalent spring constant, rotation angle, and displacement of the proposed joint. Failure analysis of the TLET joint with different materials is conducted by finite element analysis. The closed-form models are validated by simulations and experimentations. The validated results are well coincided each other. The result found that the joint achieves a maximum large displacement of 16.97 mm in the x-axis with respect to a maximum load of 20 N. When the joint slides a maximum displacement of 16.97 mm along the x-axis, the output displacement emerges out the z-axis up to 23.12 mm, respectively. The joint can achieve an angle displacement of 38.92°. The displacement of the TLET joint is 2.4 times greater than that of the traditional LET joint. The proposed joint is considered for engineering applications where a large working stroke and a large capacity of load are expected.

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Regional Stiffness Reduction Using Lamina Emergent Torsional Joints for Flexible Printed Circuit Board Design

Cited by 14 publications

References 35 publications

DSC Assessment on Curing Degree of Micron-scaled Adhesive Layer in Lamination-pressed Flexible Printed Circuit Panels

DSC Assessment on Curing Degree of Micron-scaled Adhesive Layer in Lamination-pressed Flexible Printed Circuit Panels

Load–Displacement Characterization in Three Degrees-of-Freedom for General Lamina Emergent Torsion Arrays

Design and Performance Analysis of a TLET‐Type Flexure Hinge

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