Henkel (United States)

Conductive assembly film adhesives are extensively employed in medical, telecom, aerospace, and defense systems. Glass fabric cloth is frequently utilized as the carrier in many film adhesives to enhance handling and processability during electronic device assembly. Furthermore, practical applications have shown that film adhesives with glass fabric carriers can bond adherends with severely mismatched coefficients of thermal expansion. However, the impact of embedding glass fabric on the overall performance of assembly films has not been systematically investigated. To address this gap in knowledge, a study was conducted to compare the performance of electrically conductive film adhesives with and without the glass fabric carriers. The study focused on the mechanical performance of the film adhesives, including lap shear strength, tensile modulus, and the ability to manage applications with mismatched coefficients of thermal expansion. Additionally, the study assessed the impact of the carrier on the electrical and thermal conductivity of the film adhesives. Overall, this integrated assessment provides insights into the effectiveness of the glass fabric carrier on the performance of film adhesives.

Thermal interface material (TIM) is used in between a heat generating component (e.g., microelectronic packaging) and a heat spreading component (e.g., heatsink or cooling plate) to create an effective path for the heat (Phonon) to travel. Standard heatsink and heat generating component surfaces are generally uneven and rough. Actual metal to metal contact is no more than 10%. These surface imperfections allow air to get trapped in between the two surfaces. Air, being a thermal insulator, prevents the heat from dissipating and thus the device/system fails to maintain the required operating temperature to meet the reliability and functionality needed. Replacing the air with the “right” thermal interface material is the focus of this research. TIM is a composite of thermally conductive fillers dispersed in a polymer matrix. A higher filler loading causes a higher bulk conductivity. Common practice among design engineers is to utilize output from thermal modelling & simulation to specify a TIM with a certain thermal conductivity to meet the system’s thermal needs. What many engineers miss is the impact of thermal boundary resistance that could have significant effect on the overall thermal management of the design. This paper discusses how to characterize thermal performance of TIM beyond the bulk thermal conductivity. Boundary/interfacial thermal resistance and impedance will be explored as a function of TIM wetting ability, bond line thickness and surface conditions. This paper will discuss the importance of thermal conductivity, thermal resistance/impedance in a real application scenario.

ABSTRACT ASTM Method D3233A uses a Pin&Vee Block tester to evaluate cutting fluids. However, the standard defines a steel-steel contact, uses a small volume of lubricant, and the test report is limited to the ‘ultimate failure load’. With our approach, we bring testing closer to reality, using different metallurgies and testing the oils in aqueous emulsion-form. We monitor the frictional torque throughout increasing load, so that differences between products are revealed that are not visible in failure load alone. By modifying lubrication to recirculated or misted conditions, we simulate cutting of forming operations. Consequently, this provides an additional tool for cost efficient ranking of cutting fluids, based on an industry-accepted instrument. We demonstrate same ranking of cutting fluids as well established Tapping Torque Tests, with the advantage of using a simplified and lower cost configuration. Developing a standardized test protocol involves more work on reproducibility and correlation to real machining processes.

Wafer level encapsulation is an important packaging process for several components in mobile and high-performance computing applications. In mobile applications, electronic components like application processors, radio-frequency System in Package (RF-SiP) and antenna modules are being manufactured using wafer level fan-out processes. In HPC, wafer level encapsulation is used for chip-on-wafer (CoW) processing and 2.5D / 3D packaging that enables wafer level packaging of processors and high band width memory devices. Although encapsulant materials are currently used in mass production, many pain points remain unresolved. These are predominantly related to lowering the wafer level warpage to enable better handling of wafers during processing, addressing the environmental and EU REACH regulatory compliance, providing better total cost of ownership to the end user by improving throughput and various other factors. In our development, we aim to address these pains and we will present our progress in this research paper. As the structural material in the package, molding compound can cause severe warpage issue during process, becoming the limiting factor to pursue thinner packaging design and causing serious wafer handling issues in the equipment during wafer processing. However, we considered a new material design route to develop ultra-low warpage LCM materials that can dramatically reduce the warpage thereby benefitting various WLP packaging design, such as Fan-in or Fan-out type. We have successfully demonstrated more than 70% improvement in warpage compared to traditional LCM compound. This new type of LCM material is REACH compliant and shows good warpage stability after high temperature annealing process. The polymer relaxation study shows the unique relaxation behavior leading to the warpage stability that is critical in many Fan-out processes. Dynamic Mechanical Analysis is the useful tool to study the relaxation behavior that can differentiate the impact of various chemistry on epoxy molding materials. Another key advantage of our LCM is the excellent gapfilling capability that can lead to the protection of high density structures in semiconductor packages with finer die-to-die or die-to-substrate spacing, meanwhile enabling low-warpage and simpler processing steps. Moreover, the new LCM design can help further shorten the molding time, allowing for increased throughput resulting in lower cost of ownership for the end users.

Laminate structures are widely used for food packaging applications. Polyester urethane‐based adhesives are very common materials for bonding the layers of such laminates together. Unintended by‐products of polyester synthesis include low molecular weight cyclic polyester oligomers (cyclic oligoesters) that lack the required hydroxyl functionality to react with isocyanates to form the intended high molecular weight polyurethane polymer and remain as impurities with high migration potential. Our investigation conducted migration studies of 537 commercial and/or developmental food packaging laminate structures by using food simulants with gas chromatography‐mass spectrometry analyses of the extracts. A subset of the extracts were also analysed by high‐performance liquid chromatography‐mass spectrometry and gas chromatography‐mass spectrometry with chemical ionization. Migration of cyclic oligoesters of diverse chemical structure was observed in nearly all of the samples analysed. Aside from migrants originating directly from polyolefin sealant films on the food‐contact side of the laminates, cyclic oligoesters were the migrants detected at next highest concentration. This report presents electron ionization mass spectra and molecular structures of 106 cyclic oligoesters including a series of novel as well as previously identified species. Fifty‐six cyclic oligoesters migrated from the 537 laminate samples analysed were evaluated for frequency of occurrence and migration concentration range. The most commonly observed cyclic oligoester migrants were those derived from combinations of the polyhydric alcohols, diethylene glycol, and neopentyl glycol and the dibasic acids, adipic, and phthalic/isophthalic.

Zinc oxide (ZnO) thin films have been reported to suffer from degradation in electrical properties, when exposed to elevated heat and humidity, often leading to failures of electronic devices containing ZnO films. This degradation appears to be linked to water and oxygen penetration into the ZnO film. However, a direct observation in the ZnO film morphological evolution detailing structural and chemical changes has been lacking. Here, we systematically investigated the chemical and morphological heterogeneities of ZnO thin films caused by elevated heat and humidity, simulating an environmental aging. X-ray fluorescence microscopy, X-ray absorption spectroscopy, grazing incidence small angle and wide angle X-ray scattering, scanning electron microscopy (SEM), ultra-high-resolution SEM, and optical microscopy were carried out to examine ZnO and Al-doped ZnO thin films on two different substrates—silicon wafers and flexible polyethylene terephthalate (PET) films. In the un-doped ZnO thin film, the simulated environmental aging is resulting in pin-holes. In the Al-doped ZnO thin films, significant morphological changes occurred after the treatment, with an appearance of platelet-shaped structures that are 100–200 nm wide by 1 μm long. Synchrotron x-ray characterization further confirmed the heterogeneity in the aged Al-doped ZnO, showing the formation of anisotropic structures and disordering. X-ray diffraction and X-ray absorption spectroscopy indicated the formation of a zinc hydroxide in the aged Al-doped films. Utilizing advanced characterization methods, our studies provided information with an unprecedented level of details and revealed the chemical and morphologically heterogeneous nature of the degradation in ZnO thin films.

ABSTRACT Although the price of silver has stabilised, it remains the most expensive element of the lead free Tin silver Copper (SAC) alloys. Lowering the level of silver has a number of effects beyond simply the cost of the alloy. It has been shown that decreasing the silver can improve the drop/mechanical shock resistance, a desirable parameter for many hand held applications, but at the cost of an increase in liquidus and a drop in thermal fatigue resistance. Although this impact has been studied for low silver alloys 1-3% little work has been don on ultralow silver alloys (less than 1%). In this paper the key parameters impacting the thermal fatigue of SAC0307 are studied, as well as the delta of the thermal cycle being important the peak temperature and dwell at each end of the thermal cycle are determined to be significant contributors to the ultimate performance of the solder joint. The contribution was determined to vary with the component tested. Thus care should be taken in extrapolating the thermal cycle data from one test vehicle to an actual circuit assembly.

The US Automotive Materials Partnership through the Magnesium-Intensive Front End Development Project (MFERD) is currently investigating a number of joining, coating and corrosion mitigation strategies to incorporate magnesium components into the automotive body-in-white with the ultimate goal of decreasing vehicle curb weight, thus improving fuel economy. Because Mg is anodic to all other structural metals, this is a key hurdle to Mg component implementation in vehicles. This paper will discuss the results of a study to examine the effectiveness of different corrosion mitigation strategies in joined plate assemblies and provide some insight into the systems challenges of incorporation of Mg parts into a vehicle. Details of a statistically-designed experiment developed to explore the interaction of several materials of construction (magnesium, steel and aluminum), pretreatment and topcoatings, joining methods and standardized test protocols including SAE J-2334 and ASTM B-117 are discussed. A number of avenues have emerged from this study as potential strategies for corrosion mitigation.

Significant innovations in Pb-free solder alloy formulations are being driven by volume manufacturing and field experiences. As a result, the industry has seen an increase in the number of Pb-free solder alloy choices beyond the common near-eutectic Sn-Ag-Cu (SAC) alloys first established as replacements for Sn-37Pb. The increasing number of Pb-free alloys provides opportunities to address shortcomings of near-eutectic SAC, such as poor mechanical shock performance, but also introduces a variety of technical and logistical risks. Since 2008, the Pb-Free Alloy Characterization Program sponsored by the International Electronics Manufacturing Initiative (iNEMI) has been working to fill the gap in knowledge associated with thermal fatigue resistance of these new solder alloys. Results from the extensive experimental program are now becoming available and are being published through a series of publications (see References). This paper provides a summary of the overall iNEMI's program goals, the experimental structure, and the results and analysis of thermal cycling for low silver alloys, containing 1 wt.% or less Ag. Results indicated that there is a correlation between the characteristic life of short dwell thermal cycles and Ag content. Increase in the Ag content increased the characteristic life. Another important finding is that all low-and no-Ag alloys performed better than Sn-37Pb under the test conditions. Finally, as the stress levels increase during thermal cycling, the performance differences between the Pb-free alloys diminish, and their performance appears to be approaching that of Sn-37Pb.