Electronic packaging

About: Electronic packaging is a research topic. Over the lifetime, 3977 publications have been published within this topic receiving 48510 citations.

Thermo-mechanical deformation of underfilled flip-chip packaging

Abstract: An experimental technique of in-situ moire interferometry has been applied to investigate the thermo-mechanical deformations induced by to thermal loading in an underfilled flip-chip-on-board packaging. Thermo-mechanical deformations and shear strains generated from CTE mismatch are determined experimentally as a function of thermal loading. Semi-quantitative agreement is established between measured and FEA-simulated deformations. The results show that moire interferometry with in-situ thermal loading capabilities is effective for experimental studies of electronic packaging. Through this study, the role of underfill in reducing shear strains over solder bumps and thus in improving solder shear fatigue reliability is clarified. A methodology is demonstrated to differentiate effects of underfill properties on packaging thermo-mechanical performance.

Improving signal integrity in circuit boards by incorporating absorbing materials

Abstract: Electrical signals that propagate through vias between layers of metal planes in circuit boards will generate radial waves that are guided by the planes. Multiple reflections of these parallel plate waves from the edges of the circuit board will cause resonances that greatly increase the effective impedance between the two planes at the resonant frequencies. Such resonances are highly undesirable for operation of high performance electronic packaging systems since they degrade signal qualities, increase crosstalk level and enhance simultaneous switching noise. In this paper we show that the magnitude of the resonances can be greatly reduced by incorporating an absorbing material between the metal planes at the perimeter of the circuit board. As a result the signal integrity of the system is improved. By using absorbing materials whose loss depends upon magnetic rather than electric effects, it is possible to choose materials whose resistivity is of the order of 10/sup 12/ ohm-cm, making it possible to place the materials directly between power and ground planes without introducing any DC current leakage. These materials are available commercially in flexible and hard, dense forms and can be chosen to enhance losses at either the UHF band or various microwave frequency bands to accommodate different needs. Results of theoretical computation are compared with experiments performed on test boards characterized using a vector network analyzer between 50 MHz and 6 GHz. Significant reduction in input impedance of the test structure at resonance frequencies is obtained, which shows the effectiveness of the proposed method and the accuracy of the calculation method. The paper also evaluates several ways of applying the lossy material.

Low-cost and low-electromagnetic-interference packaging of optical transceiver modules

Abstract: The low-cost and low-electromagnetic-interference (EMI) packaging of optical transceiver modules employing housings of plastic composites are developed and fabricated. Optical transceiver modules fabricated by the plastic composites with transmission rates of 1.25 and 2.5 Gb/s are tested to evaluate the electromagnetic (EM) shielding against emitted radiation from the plastic packaging. The results show that these packaged optical transceiver modules with their high shielding effectiveness (SE) are suitable for use in low-cost and low-EMI Gigabit Ethernet lightwave transmission systems. By comparison of cost, weight, and shielding performance for optical transceiver modules fabricated by the housings of nylon and liquid-crystal polymer with carbon fiber filler composites, woven continuous carbon fiber (WCCF), and nanoscale hollow carbon nanocapulses (HCNCs) epoxy composites, the WCCF composite shows lower cost, lighter weight, and higher EM shielding than the other types of composites. Future studies may develop the low-cost and low-EMI optical transceiver modules using nanoscale HCNCs that have the combination of excellent physical and mechanical properties, light weight, and thinness compared with the conventional fabrication techniques.

Thermal Stability Characterization of the Au–Sn Bonding for High-Temperature Applications

Abstract: There is a need for electromechanical devices capable of operating in high-temperature environments (>200°C) for a wide variety of applications. Today's wide-bandgap semiconductor-based power electronics have demonstrated a potential of operating above 400°C, however, they are still limited by packaging. Among the most promising alternatives is the Au-Sn eutectic solder, which has been widely used due to its excellent mechanical and thermal properties. However, the operating temperature of this metallurgical system is still limited to ~250°C owing to its melting temperature of 280°C. Therefore, a high-temperature-resistant system is much needed, but without affecting the current processing temperature of ~325°C, typically exhibited in most high-temperature Pb-free solders. In this paper, we present the development and characterization of a fluxless die-attach soldering process based on gold-enriched solid-liquid interdiffusion (SLID). A low-melting-point material (eutectic Au-Sn) is deposited in the face of a substrate, whereas a high-melting-point material, gold in this instance, is deposited in its mating substrate. Deposition of all materials was performed using a jet vapor deposition (JVD) equipment where thicknesses are controlled to achieve specific compositions in the mixture. Sandwiched coupons are isothermally processed in a vacuum reflow furnace for different reflow times. Post-processed samples confirm the interdiffusion mechanism as evidenced by the formation of sound joints that prove to be thermally stable up to ~490°C after the completion of the SLID process. Differential scanning calorimetry demonstrate the progression of the SLID process by quantifying the remaining low-melting-point constituent as a function of time and temperature, this serving as an indicator of the completion of the soldering process. Mechanical testing reveals a joint with shear strength varying from 39 to 45.5 MPa, demonstrating to be stable even after 500 h of isothermal aging. Moreover, these investigations successfully demonstrate the use of the Au-Sn SLID system and the JVD technology as potential manufacturing processes and as a lead-free die-attach technology.