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This paper describes the chemistry and physics of the Glass Transition Temperature (Tg) and how it is measured in epoxy glass laminates using thermochemical techniques. Tg is related to the degree of cure of the epoxy resin and is used in the quality control of laminates for printed circuit board manufacture.

A common method for understanding the thermal performance of epoxy laminate materials is to analyze the glass transition temperature using instruments such as differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and thermomechanical analysis (TMA). In order to characterize the long‐term performance of a finished printed circuit board, more advanced reliable test methods have been developed. This paper will discuss interconnect stress testing (IST), an accelerated fatigue test used for evaluating the failure modes of a printed circuit board (PCB) interconnect. IST utilizes a DC current to heat the PCB to the recommended temperatures within the interconnect. The plated through hole integrity and the post‐interconnect integrity can be monitored simultaneously. The test matrix compares the performance of various AlliedSignal epoxy laminate materials as a function of glass transition temperature (Tg) and board design.

Differential Scanning Calorimetry (DSC) is an ideal technique for characterising polymeric materials such as the epoxy resin in epoxy glass prepregs and laminates, the technique having evolved from the older qualitative method of Differential Thermal Analysis (DTA). In DSC the heat flow to or from the sample is measured as a function of temperature or time. Epoxy glass prepregs are used as the bonding/insulating layer in multilayer printed circuit boards. When a sample of the epoxy resin in prepreg is heated, the heat flow that results from the exothermic curing reaction is measured and used to calculate the enthalpy ΔH of the reaction. ΔH is related to the degree of B stage curing and the flow achievable in the laminating press. Methods are given for calculating ΔH and the differences found in two manufacturers' prepreg material are discussed. The effect of ageing on ΔH, which has been found to decrease with time and with the extent of cure, is examined at room temperature and under refrigeration. The difference in the ageing properties of the two prepregs is explained by reference to a plot of the degree of conversion with time. This plot also enables the curing time required in the lamination press and the shelf life of the prepreg at room temperature to be calculated. Monitoring the degree of cure of laminates and cured prepreg using the glass transition temperature of the resin is examined. Insufficient cure may lead to problems of resin smear in multilayer printed circuit boards. Thermochemical analysis is used as a routine quality control method in the Microcircuit Assembly Techniques Facility at Marconi Research Centre for testing incoming prepreg and laminates used in multilayer printed circuit board manufacture.

This purpose of this paper is to provide an overview of the steps and processes behind successfully adapting novel materials, namely virgin glass and recycled glass, to three‐dimensional printing (3DP).

The transition from 3DP ceramic systems to glass systems will be examined in detail, including the necessary modifications to binder systems and printing parameters. The authors present preliminary engineering data on shrinkage, porosity, and density as functions of peak firing temperature, and provide a brief introduction to the complexities faced in realizing an adequate and repeatable firing method for 3D printed glass.

Shrinkage behavior for the 3D printed recycled glass showed significant anisotropy, especially beyond peak firing temperatures of 730°C. The average shrinkage ratios for the slow‐ and fast‐axes to the Z‐axis were 1:1.37 and 1:2.74, respectively. These extreme differences can be attributed to the layer‐by‐layer production method and binder burn‐off. At 760°C, the apparent porosity reached a minimum of 0.36 percent, indicative of asymptotic behavior that approaches a fully dense 3DP glass specimen. At low firing temperatures, the bulk density was similar to water, but increased to a maximum of 2.41 g/cm³. This indicates that 3DP recycled glass can behave similarly to common glass with accepted published bulk densities ranging from 2.4‐2.8 g/cm³.

Heating schedule analysis and optimization may reduce geometric variations, therefore, the firing method should be investigated in greater depth.

This paper provides a guide to successfully adopting glass to commercially available 3DP hardware. This research has also enabled rapid prototyping of recycled glass, a monumental step towards a sustainable future for 3DP.

This paper presents a numerical and experimental investigation of ceramic shell cracking during the burnout process in investment casting with internally webbed laser stereolithography patterns. Considered are the cracking temperature of the ceramic shell, the buckling temperature of the web link, and the glass transition temperature of the epoxy resin. Our hypothesis is that shell cracking will occur if the ceramic rupture temperature is lower than the temperature of glass transition and the temperature of web buckling. This hypothesis is validated by a good agreement we obtained between experimental observations and numerical simulations. It is found that the shell cracking and web link buckling are strongly related to the cross‐sectional dimensions and span length of the web structure and the shell thickness, and that shell cracking can be prevented by buckling of the epoxy webbed pattern in early stages of the burnout process.

This paper presents a reliability assessment of adhesive joints using chip‐on‐glass (COG) technology which was conducted by testing samples at various aging temperatures and at high humidity.The range of aging temperatures took into account the glass transition temperature (Tg) of the adhesive films. The effects of high temperature and high humidity on the bond strength of flip‐chip‐on‐glass joints were evaluated by shear testing as well as by microstructural examination.It was found that aging generally caused a decrease in shear strength while the aging temperature was below the glass transition temperature of ACF. When the aging temperature was slightly above the Tg of the ACF, a significant decrease in shear strength was observed. Moreover, results from scanning electronic microscopy revealed the presence of some voids near the component bumps, resulting in high stresses at the high aging temperature. DSC results showed that the ACF was not fully cured, allowing moisture absorption more seriously than a fully cured ACF, leading to joint degradation.

This study aims to characterize a novel glass/epoxy architecture sandwich structure for electronic boards. Understanding the thermo-mechanical behavior of these composites is important because it is possible to pre-determine whether defined “internal” thick laminates will be suitable for embedding components in the direction of the axis “z,” i.e. this method of manufacturing multilayer laminates can be used for incoming miniaturization in electronics.

Laminates with a low glass transition temperature (Tg) and high Tg with E-glass type were treated, tested and compared. Testing samples were manufactured by nonstandard two steps unidirectional lamination as a multilayer structure based on prepreg layers and as “a sandwich structure” to explore its effect on thermo-mechanical properties. The proposed tested method determines the time and temperature-dependent viscoelastic properties of the board by using dynamic mechanical analysis, thermo-mechanical analysis and three-point bend tests.

This testing method was chosen because the main property that promotes sandwich structure is their high stiffness. Glass/epoxy stiff and thermal stabile sandwich structure prepared by nonstandard two-stage lamination is proper for embedding components and the next miniaturization in electronics.

Compared with by-default applied glass-reinforced homogenous laminates, novel architecture sandwich structure is attractive because of a combination of strength, stiffness and all while maintaining the miniaturization requirement and multifunctional application in electronics.

The build characteristics of two liquid crystal (LC) reactive monomers were studied using a table‐top stereolithography apparatus (TTSLA). LC materials contain stiff, rod‐like mesogenic segments in their molecules, which can be aligned causing an anisotropy in properties. When cured in the aligned state the anisotropic structure is “locked in” resulting in materials with anisotropic physical and mechanical properties. By varying the alignment of layers, properties such as thermal expansion coefficient can be optimized. High heat distortion (or glass transition) temperatures are possible depending on the monomer chemical structure. Working curves for the LC resins were developed under various conditions. A permanent magnet placed outside the TTSLA vat was used to uniformly align the monomer in the nematic state. Photo‐initiator type and content; alignment of the nematic phase; and operating conditions affected the working curve parameters. Glass transition temperatures of post‐cured parts ranged from 75 to 1488C depending on the resin and processing conditions. Mechanical analysis data revealed a factor of two difference between glassy moduli measured in the molecular alignment versus the transverse alignment directions. Based on these initial studies, more advanced resins with higher glass transitions are being developed at the University of Dayton.

Polyurea is an elastomeric two-phase co-polymer consisting of nanometer-sized discrete hard (i.e. high glass transition temperature) domains distributed randomly within a soft (i.e. low glass transition temperature) matrix. A number of experimental investigations reported in the open literature clearly demonstrated that the use of polyurea external coatings and/or internal linings can significantly increase blast survivability and ballistic penetration resistance of target structures, such as vehicles, buildings and field/laboratory test-plates. When designing blast/ballistic-threat survivable polyurea-coated structures, advanced computational methods and tools are being increasingly utilized. A critical aspect of this computational approach is the availability of physically based, high-fidelity polyurea material models. The paper aims to discuss these issues.

In the present work, an attempt is made to develop a material model for polyurea which will include the effects of soft-matrix chain-segment molecular weight and the extent and morphology of hard-domain nano-segregation. Since these aspects of polyurea microstructure can be controlled through the selection of polyurea chemistry and synthesis conditions, and the present material model enables the prediction of polyurea blast-mitigation capacity and ballistic resistance, the model offers the potential for the “material-by-design” approach.

The model is validated by comparing its predictions with the corresponding experimental data.

The work clearly demonstrated that, in order to maximize shock-mitigation effects offered by polyurea, chemistry and processing/synthesis route of this material should be optimized.

The purpose of this paper is to understand the recovery mechanism of poly(trimethylene terephthalate) (PTT) shape memory fabrics.

Tests were designed to study the effects of force, temperature and their combinations on the fabrics' crease recoveries. In the test a cantilever device and an ironing force which simulated people ironing their clothes were used, respectively.

Temperature was found to have little effect on the recovery of both the warp and filling of the fabrics. Crease recoveries did not improve significantly when the temperature was increased to above the polymer's glass transition. However, forces, applied in primarily compressive and tensile modes to simulate ironing and hand stroking actions, were found to be very effective in the fabrics' crease recoveries. Recoveries were 81‐87 per cent even when the applied force was very small, at 5 N/cm². When forces were applied at elevated temperatures, just below and above the polymer's glass transition, there were no significant improvements in crease recoveries. Therefore, force was the main factor in PTT shape memory fabrics' recovery mechanism for the fabrics to return to their initial shapes.

The results suggest that PTT shape memory fabric has excellent shape recoverability and easy care property and it has large application potentiality.