Study on Thermal Cycling Reliability of Epoxy-Enhanced SAC305 Solder Joint.

In this work, epoxy was added into commercial Sn-3.0Ag-0.5Cu (SAC305) solder paste to enhance the thermal cycling reliability of the joint. The microstructure and fracture surface were observed using a scanning electron microscope/energy dispersive spectrometer (SEM/EDS), and a shear test was performed on the thermally cycled joint samples. The results indicated that during the thermal cycling test, the epoxy protective layer on the surface of the epoxy-enhanced SAC305 solder joint could significantly alleviate the thermal stress caused by coefficients of thermal expansion (CTE) mismatch, resulting in fewer structural defects. The interfacial compound of the original SAC305 solder joints gradually coarsened due to the accelerated atomic diffusion, but epoxy-enhanced SAC305 solder joints demonstrated a thinner interfacial layer and a smaller IMC grain size. Due to the reduced stress concentration and the additional mechanical support provided by the cured epoxy layer, epoxy-enhanced SAC305 solder joints displayed superior shear performance compared to the original joint during the thermal cycling test. After 1000 thermal cycles, Cu-Sn IMC regions were observed on the fracture surfaces of the original SAC305 solder joint, exhibiting brittle fracture characteristics. However, the fracture of the SAC305 solder joint with 8 wt.% epoxy remained within the solder bulk and exhibited a ductile fracture mode. This work indicates that epoxy-enhanced SAC305 solder pastes display high thermal cycling reliability and could meet the design needs of advanced packaging technology for high-performance electronic packaging materials.

[Residual Guidewire Removal in the Aorta Using Minimally Invasive Approach:Report of a Case].

An 80-year-old man had a guidewire in his aorta since catheter laboratory accident 4 years ago. He recently started to suffer mental distress and underwent coronary angiography that revealed an entrapped guidewire and significant stenoses in each of three major coronary arteries. The guidewire could not be removed using transcatheter technique. Thus, after careful consideration, we decided to perform entrapped guidewire removal through minimally invasive surgical approach instead of median sternotomy. Post-operative course was uneventful. Although surgical approach should be tailored in each case, minimally invasive approach can be a choice for entrapped guidewire removal.

[Successful Treatment of Blow-out Type Left Ventricular Free Wall Rupture Using Sutureless Technique].

Blow-out type left ventricular free wall rupture is a serious complication of acute myocardial infarction, that carries high hospital mortality rates and poor surgical outcome. We report the case of an 88-year-old woman who developed cardiac tamponade following percutaneous coronary angioplasty for acute myocardial infarction. She was diagnosed with left ventricular free wall rupture, and rupture type was proved to be blow out after median sternotomy. To address this critical condition, we opted for the sutureless technique for its minimally invasive nature and ability to preserve left ventricular function. The patient was discharged from the hospital without any complications 22 days after surgery. Considering favorable, encouraging outcomes of this case, sutureless technique could be regarded as a viable option for blow-out type left ventricular free wall rupture.

Impact of crystalline orientation on Cu-Cu solid-state bonding behavior by molecular dynamics simulations.

High-density electronics are hindered by the constraints of Sn-based solder joints, necessitating the exploration of Cu-Cu solid-state bonding. However, current bonding methods are expensive and time-consuming; therefore, understanding the Cu-Cu bonding mechanism is crucial for optimization. This study utilizes molecular dynamics (MD) simulation to elucidate the Cu-Cu solid-state bonding behavior, focusing on interfacial densification and diffusion phenomena. Furthermore, it highlights the influence of crystal orientation on the interfacial bonding behavior. To analyze the impact of crystal orientation, monocrystalline Cu slabs with a simplified periodic surface structure were employed to replicate surface roughness and subsequently bonded at a specific temperature. The results indicate the critical influence of crystalline orientations on the bonding process: identical orientations result in slower densification at the interface, whereas misoriented orientations significantly accelerate it. This effect, attributed to the grain boundary (GB) structures formed owing to misorientation, suggests a central role for GB diffusion in bonding progression. Diffusion coefficients calculated using the mean square displacement (MSD) confirmed these findings and exhibited significantly larger values for misoriented joints. Additionally, the simulations reveal an activation energy for GB diffusion that is lower than conventional values, highlighting the impact of the crystallographic orientation and voids at the bonding interface. Our research elucidates the role of crystalline orientation in diffusion phenomena at bonding interfaces, offering valuable implications for optimizing bonding-based manufacturing processes.

Thermomechanical Properties of Zeta (Ag3In) Phase.

The thermomechanical properties of materials within die-attach joints play an essential role in assessing the reliability of high-power modules. Ag-In transient liquid phase (TLP) bonding serves as an alternative method for die attachment. However, relevant material data for the ζ (Ag3In) phase, one of the Ag-In intermetallic compound (IMC) products of TLP bonding, are limited. This paper proposes an approach to fabricate a densified and pure bulk sample of the ζ (Ag3In) phase. The thermomechanical properties of the ζ (Ag3In) phase were subsequently investigated at elevated temperatures and compared to those of other IMCs frequently observed in die-attach joints. As the temperature increased from 30 °C to 200 °C, the hardness of the ζ (Ag3In) phase decreased linearly from 1.78 GPa to 1.46 GPa. Similarly, the Young's modulus also decreased linearly from 82.3 GPa to 66.5 GPa. These properties rank among the lowest levels compared to those of other IMCs. The average coefficient of thermal expansion within the temperature range of 70 °C to 250 °C was approximately 18.63 ± 0.61 µm/m/°C, placing the ζ (Ag3In) phase at a moderate level. When considering its potential for mitigating thermal stress, these combined properties render the ζ (Ag3In) phase an appropriate material choice for die-attach joints compared to other IMCs.

Influence of Isothermal Aging on Microstructure and Shear Property of Novel Epoxy Composite SAC305 Solder Joints.

With the rapid iteration of microsystem integrated technology, the miniaturization of electronic devices requires packaging materials with higher reliability. In this work, the microstructure evolution and mechanical properties of novel epoxy composite SAC305 solder joints were studied after isothermal aging to evaluate the enhanced effect of epoxy addition. The thickness variation and morphological evolution of the interfacial layer were analyzed. The results showed that, as the aging time was prolonged, the Cu6Sn5 interfacial layer remarkably coarsened and Cu3Sn compounds formed between the Cu6Sn5 layer and Cu pad due to the continuous atomic diffusion. Compared with the monolithic joint, the epoxy composite SAC305 joints had a lower overall IMC growth rate during aging, closely related to the initial morphologies of the interfacial layers. The shear test results showed an apparent decrease in the shear forces of all the solder joints as the aging time increased. Nevertheless, because of the extra mechanical support provided by the epoxy layer, the epoxy composite joints demonstrated notably enhanced mechanical properties. After 1000 h aging treatment, the shear force of SAC305 joints containing 8 wt.% epoxy was 26.28 N, showing a 24.08% increase over the monolithic joint. Cu-Sn IMCs were detected on the shear fracture of the monolithic joint after 1000 h aging, indicating the fracture occurred near the interface and displayed a ductile/brittle mixed fracture. Concerning the epoxy composite joints, cracks were still initiated and extended within the solder bulk, demonstrating a noticeable enhancement in ductility due to the addition of epoxy.

Surgical treatment for coarctation of the aorta.

Key Clinical Message: Surgical treatment is a better option for coarctation of the aorta. Abstract: A 56-year-old man was admitted to the hospital due to chest pain. Computed tomography showed severe coarctation of the aorta distal to the left subclavian artery, with poststenotic dilatation of the descending aorta. A descending aortic replacement was performed in an uneventful manner. The postoperative course was good without symptoms.

[Ascending Aortic Mural Thrombus Caused by Plaque Destruction:Report of a Case].

A 52-year-old male with complaints of pain and cold sensation on left upper-extremity was admitted to a hospital. He was diagnosed with acute left brachial artery occlusion and accordingly underwent emergency thrombectomy. Contrast-enhanced computed tomography (CT) revealed an ascending aortic mural thrombus (AMT). After his transferring to our institution, the AMT was removed, and the ascending aorta was replaced under cardiac arrest. Based on histopathological findings, the thrombus was caused by the destruction of an atheromatous plaque. The patient's postoperative course was uneventful, and no recurrence of AMT was presented for 12 months after operation.

Reconstruction of Noma Sequelae: A Surgical Treatment Algorithm Developed from Lessons from 210 Cases in Ethiopia.

Noma is an infectious disease affecting mostly children aged 0-10. Although it has almost completely disappeared from the Western world, it is still prevalent in many developing regions, mainly Africa's Sahel region. The infection behaves like a necrotizing fasciitis of the face, originating from the gums and progressively expanding into the cheek, nose, or eye regions. In an estimated 90% of cases, the disease is lethal as a result of systemic sepsis. For survivors, typical results are extensive defects of the cheek, nose, and periorbital and perioral regions. Due to the defects, extensive scarring is common, which leads to secondary problems such as growth alterations in an infant's skeleton due to inhibition and restraint of growth resulting typically in cicatricial skeletal hypoplasia. Other sequelae include trismus, partially caused by scarring or complete fusion between maxilla/zygomatic arch and mandible. The resulting overall disfiguring facial appearance results in patients being disabled and socially isolated. Methods: Facing Africa is a UK-based non-governmental organization that treats the secondary problems of Ethiopian noma survivors. Operations are performed in Addis Ababa by a visiting expert team. Postoperatively, patients are seen annually for years after the surgery. Results: This article discusses basic principles, goals, and a practical surgical algorithm for operating on lip, cheek, and oral defects, based on 210 noma patients who were operated on in Ethiopia over a period of 11 years. Conclusions: The suggested algorithm has proven to work for the Facing Africa team members and is considered shareware for all surgeons to use and benefit from.

Study on the SPCC and CFRTP Hybrid Joint Performance Produced with Additional Nylon-6 Interlayer by Ultrasonic Plastic Welding.

Due to the high degree of dissimilarity in physicochemical properties between metal and carbon fiber, it presents a tremendous challenge to join them directly. In this paper, cold rolled steel (SPCC) and carbon fiber reinforced thermoplastic (CFRTP) chopped sheet hybrid joints were produced with the addition of Nylon 6 (PA6) thermoplastic film as an intermediate layer by the ultrasonic plastic welding method. The effect of ultrasonic welding energy and preheating temperature on the hybrid joint microstructure and mechanical behavior was well investigated. The suitable joining parameters could obtain a strong joint by adding the PA6 film as an intermediate layer between the SPCC and bare carbon fibers. Microstructural analysis revealed that the interface joining condition between the PA6 film and the SPCC component is the primary reason for the joint strength. The crevices generated at the interface were eliminated when the preheating temperature arrived at 200 °C, and the joint strength thus significantly increased. The lap shear test results under quasi-static loading showed that the welding energy and preheating temperature synergistically affect the joint performances. At 240 °C, the joint strength value reached the maximum. Through the analysis of the microstructure morphology, mechanical performance, and the failure mechanism of the joint, the optimized joining process window for ultrasonic plastic welding of SPCC-CFRTP by adding an intermediate layer, was obtained.

A surgical treatment for frank rupture of acute type a small intramural hematoma.

A 71-year-old woman was admitted to the hospital due to cardiac tamponade. Computed tomography revealed that the diameter and wall thickness of the ascending aorta were 36 and 9 mm, respectively. An emergent ascending aortic replacement was performed uneventfully. The pathological findings indicated frank rupture of intramural hematoma.

[Right Anterior Minithoracotomy as an Effective Technique for Minimally Invasive Aortic Valve Replacement in Frail and Elderly Patient:Report of a Case].

Transcatheter aortic valve replacement has increasingly been used as a standard treatment option for patients with aortic valve stenosis, especially in the frail and the elderly. However, it is not recognized as a valid treatment for patients with aortic valve regurgitation. In this study, we report our experience in conducting a right anterior minithoracotomy for a minimally invasive aortic valve replacement in the elderly. An 87-year-old woman with severe aortic valve regurgitation was admitted to our department. Minimally invasive aortic valve replacement was performed, through a right anterior minithoracotomy in the second intercostal space. A localized transverse aortotomy was performed at a position higher than that in an ordinary aortotomy. Our procedure for aortic valve replacement was similar to the conventional method. The postoperative course was uneventful, and the patient was discharged after 10 days. Therefore, we conclude that right anterior minithoracotomy for a minimally invasive aortic valve replacement is a feasible, effective, and safe technique.

Solid-state bonding behavior between surface-nanostructured Cu and Au: a molecular dynamics simulation.

In recent years, solid-state bonding has attracted attention for various electronic packaging applications as an alternative to conventional solders. Surface-nanostructured materials enable solid-state bonding without complex surface modifications and operate at a low bonding temperature and pressure. Therefore, in this study, molecular dynamics simulations were conducted to investigate the solid-state bonding behavior between surface-nanostructured Cu and Au, with a focus on diffusion phenomena. A periodic ligament-cavity nanostructured Cu (NS-Cu) model was prepared at the bonding interface between Cu and Au slabs. The simulation results indicated that the larger the specific surface area of NS-Cu, the faster the densification at the bonding interface. Atomic displacement analysis showed that rapid densification occurred via the displacement of Cu and Au atoms in the vicinity of NS-Cu. The preferential diffusion of atoms along NS-Cu cavities contributed to this phenomenon. At this stage of densification, the diffusion coefficients were higher than the surface diffusion coefficients estimated based on literature, which indicates that this behavior is specific to surface-nanostructured materials. The highly disordered atomic arrangement at the bonding interface enabled significant atomic diffusion. Therefore, this study confirmed that the use of surface-nanostructured materials would contribute to a promising bonding technology for application in electronics.

Posterior Calvarial Distraction in older paediatric population: single centre paediatric neurosurgery craniofacial unit outcomes.

PURPOSE: Posterior calvarial distraction (PCD) is a safe and effective technique used to increase cranial vault volume and therefore reduce intracranial pressure in children with complex craniosynostosis. Optimal timing and method used for PCD is controversial. This procedure is usually performed in children younger than 2 years. Literature regarding calvarial distraction in older children is sparse and limited. We report our single-centre experience with PCD in children aged 6 and above to outline the applications, benefits and challenges of employing this technique in an older paediatric population. METHODS: A retrospective analysis of a database on craniofacial cases from 2006 to 2021 was performed. Patients undergoing PCD were identified and children aged 6 and above at the time of operation were included. Data on demographics and clinical outcomes were obtained from electronic records and relevant imaging was reviewed. All cases were reviewed prior to a decision for surgery by the multidisciplinary craniofacial team (composed of neurosurgery, maxillofacial and plastics teams) and underwent surgery in our paediatric craniofacial centre. RESULTS: Overall, 98 PCD cases were identified during the study period, of which 20 cases were identified as having undergone PCD at age 6 or above with mean age of 8.8 years (range 6-18). The most common indication was pansynostosis associated with raised intracranial pressure. Four cases had calvarial remodelling previously and represented with symptoms of raised intracranial pressure sometime after their initial surgery requiring PCD as rescue procedure. Average duration of inpatient stay was 5.85 days. The average duration of follow-up was 3.5 years (0.3 to 11 years). Mean distraction distance achieved was 22.5 mm (18-29 mm). Five patients experienced complications related to wound infection or distractor. Follow-up assessment in all patients demonstrated evidence of vault expansion and symptomatic improvement and resolution of intracranial pressure signs. Comparison with younger cohort did not reveal any difference in any parameters except lower rate of transfusion in the older cohort compared to young cohort (5% vs 38%). CONCLUSION: Posterior calvarial distraction in older children is safe and effective for vault expansion and treatment of raised intracranial pressure in selected cases. A multidisciplinary craniofacial team approach is crucial for appropriate case selection and management in order to optimise outcomes.

[A Surgical Technique for Ascending Aorta-bifemoral Bypass and Coronary Artery Bypass Grafting without Aortic Cross-clamp].

A 69-year-old woman presented with symptoms of resting pain in the lower limb bilaterally. A computed tomography( CT) scan revealed occlusion of the infrarenal aorta and bilateral common iliac arteries, indicating Leriche syndrome. A coronary angiogram demonstrated in-stent restenosis in the left anterior descending coronary artery. Therefore, the patient underwent off-pump coronary artery bypass grafting (left mammary artery to left anterior descending coronary artery) and ascending aorta-bifemoral bypass using the HeartString device for the inflow anastomosis. The postoperative period was uneventful. Although an indication for this surgical technique should be tailored to the anatomy of the lesion, it is a reliable surgical option to achieve good outcomes.

[Acute Aortic Dissection after Reoperative Aortic Valve Replacement with Early Diagnosis:Report of a Case].

Acute aortic dissection is a rare and potentially catastrophic perioperative complication of cardiac surgery. A 72-year-old woman underwent aortic valve replacement with a bioprosthetic valve for aortic regurgitation seven years earlier. She experienced respiratory distress on exertion and was diagnosed with prosthetic valve dysfunction. Reoperative aortic valve replacement with a bioprosthetic valve was performed. On postoperative day eight, contrast-enhanced computed tomography, which was performed to evaluate persistent high levels of inflammatory response, revealed acute DeBakey typeⅠaortic dissection. Emergency ascending aortic replacement was successfully performed. The patient was discharged on postoperative day 19 without any complications. Acute aortic dissection after cardiac surgery is rare;however, physicians should be aware of this possible complication.

Focal atrial tachycardia originating from the pulmonary vein with onset later than 3 years of age might have a better prognosis, possibly converting in adolescence.

Two cases of focal atrial tachycardia probably originating from the pulmonary vein with onset later than 3 years of age are presented. Both cases had associated variable atrioventricular conduction and showed no signs of heart failure, and they converted to sinus rhythm at the time of puberty. In cases of focal atrial tachycardia originating from the pulmonary vein with onset later than 3 years of age, drug therapy may be effective. Even if drug therapy is not effective, changes in the autonomic nervous system are reflected strongly in the pulmonary veins, so that changes in autonomic nervous system regulation with growth might terminate focal atrial tachycardia. Therefore, focal atrial tachycardia originating from the pulmonary vein with onset later than 3 years of age might have a better prognosis.

Prevention of surgical adhesions with gelatine sealing sheet in a canine adhesion model.

OBJECTIVES: Although reoperation has been increasingly performed in cardiovascular surgery in recent years, preventing surgical adhesions remains an unsolved complication. Therefore, this study aimed to investigate whether gelatine sealing sheets are more effective than fibrin sealing sheets in preventing surgical adhesions. METHODS: Bilateral femoral arteries of 20 beagle dogs under general anaesthesia were pricked with syringe needles, and gelatine and fibrin sealing sheets were applied on the bleeding points to make canine adhesion models. The femoral artery was harvested after 4 and 12 weeks to evaluate adhesion formations. The adhesive grade was quantified by scoring the area and strength of adhesion tissues. Histological staining was performed to examine the structural features of surgical adhesions. RESULTS: Significantly fewer macroscopic adhesions were observed with gelatine sealing sheets than those with fibrin sealing sheets at 4 and 12 weeks postoperatively. Microscopically, CD3+ T lymphocytes at 4 and 12 weeks postoperatively in gelatine sealing sheets were significantly lower than those in fibrin sealing sheets. Microvessel density determined by CD34 at 4 and 12 weeks postoperatively in gelatine sealing sheets was also significantly lower than those in fibrin sealing sheets. CONCLUSIONS: The gelatine sealing sheets are more effective than the fibrin sealing sheets in preventing surgical adhesions. These findings suggest that the gelatine sealing sheet may help prevent adhesions and thus be a therapeutically effective biomaterial in vascular surgery.