ABSTRACT
In soft electronics, anisotropic conductive adhesive films (ACFs) are the trending interconnecting approach due to their substantial softness and superior bondability to flexible substrates. However, low bonding pressure (≤1 MPa) and fine-pitch interconnections of ACFs become challenging while being extended in advanced device developments such as wafer-level packaging and three-dimensional multi-layer integrated circuit board assembly. To overcome these difficulties, we studied two types of ACFs with distinct conductive filler sizes (ACF-1: ~20 µm and ACF-2: ~5 µm). We demonstrated a low-pressure thermo-compression bonding technique and investigated the size effect of conductive particles on ACF's mechanical properties in a customized testing device, which consists of flexible printing circuits and Flex on Flex assemblies. A consistency of low interconnection resistance (<1 Ω) after mechanical stress (cycling bending test up to 600 cycles) verifies the assembly's outstanding electrical reliability and mechanical stability and thus validates the great effectiveness of the ACF bonding technique. Additionally, in numerical studies using the finite element method, we developed a generic model to disclose the size effect of Au/Ni-coated polymer fillers in ACF on device reliability under mechanical stress. For the first time, we confirmed that ACFs with smaller filler particles are more prone to coating fracture, leading to deteriorated electrical interconnections, and are more likely to peel off from substrate electrode pads resulting in electrical faults. This study provides guides for ACF design and manufacturing and would facilitate the advancement of soft wearable electronic devices.
ABSTRACT
As the integration technology for integrated circuit (IC) packaging continues to advance, the issue of electromagnetic interference in IC packaging becomes increasingly prominent. Magnetic materials, acknowledged for their superior electromagnetic absorption capabilities, play a pivotal role in mitigating electromagnetic interference problems. In this study, we employed a liquid-phase reduction method. We prepared three types of cobalt (Co) particles with distinct morphologies. Through variations in the synthesis process conditions, we were able to control the aspect ratio of protrusions on the surface of the Co particles. It was found that the sword-like Co particles exhibit superior electromagnetic wave absorption capabilities, showing a reflection loss value of up to -50.96 dB. Notably, when the coating thickness is only 1.6 mm, the effective absorption bandwidth is extended up to 7.6 GHz. The spatially expansive sword-like Co particles, with their unique structure featuring dipole polarization and interfacial polarization, demonstrated enhanced dielectric and magnetic loss capabilities, concurrently showcasing superior impedance-matching performance.
ABSTRACT
OBJECTIVE: To investigate the feasibility of grayscale ultrasound and quantitative shear wave elastography (SWE) for assessing the image features and stiffness of the Achilles tendon in patients with familial hypercholesterolemia (FH) compared with healthy controls. METHODS: A total of 38 Achilles tendons from healthy control participants and 94 from patients with FH were examined with grayscale ultrasound and SWE. Each Achilles tendon examination was performed on 3 different segments (proximal, middle, and distal). The thickness, grayscale image features and elasticity modulus of each segment was measured on longitudinal views. RESULTS: In Achilles tendons of healthy control participants, the thicknesses of the proximal, middle, and distal segments were (4.46 ± 0.68) mm, (5.41 ± 1.01) mm, and (4.41 ± 0.57) mm, respectively. The grayscale features were diffusely hypoechoic with parallel linear hyperechoic striations. The mean elasticity modulus of the proximal, middle, and distal sites was (418.08 ± 43.13) kPa, (425.78 ± 47.14) kPa, and (407.79 ± 38.74) kPa, respectively. In the FH group, the thicknesses of the proximal, middle, and distal segments were (7.65 ± 3.09) mm, (11.46 ± 4.84) mm, and (8.14 ± 2.90) mm, respectively. The grayscale features were hypoechoic with linear hyperechoic disordered fibre distribution (92/94). Two of 94 Achilles tendons had considerable focal hypoechogenicity. Seventeen of 94 Achilles tendons had calcifications. In the FH group, the mean elasticity modulus of the proximal, middle, and distal segments were (294.86 ± 58.13) kPa, (280.93 ± 63.58) kPa, and (282.41 ± 56.47) kPa, respectively. Statistically significant differences were found between the Achilles tendons of healthy control participants and FH patients in the thicknesses and mean elasticity modulus at the proximal, middle and distal segments of the Achilles tendons (all P < 0.001). CONCLUSIONS: Our results suggest that the grayscale features and SWE characteristics of the Achilles tendon provided complementary biomechanical information for quantitative assessment the Achilles tendon in patients with FH.
