Subhotosh Khan

Comparison of the dielectric constant and dissipation factors of non‐woven aramid/FR4 and glass/FR4 laminates

Permittivity and dissipation factor (Dk and Df) are effects of polarization of different components of the dielectric substrate material when subjected to an electrical field. A database of these important design parameters for PWBs has been developed for Thermount RT. Effects of variations in the level of moisture (bone‐dry to completely saturated at various relative humidity levels), testing temperature (room temperature to 120uC) and testing frequencies (1MHz to 1.5GHz) on Dk and Df are reported. As the frequency of test is increased from 1MHz to 1.5GHz, the effect of moisture on the properties is reduced. Comparison with conventional glass/FR4 laminate properties shows the distinct advantage of Thermount. It is increasingly used in high frequency cellular telephone, satellite, and wireless applications which require HDI PWBs to achieve the highest packaging density at the lowest cost and weight.

Finite element modeling to analyze durability of BGA/CSP connections during thermal shock

Personal electronic devices at the user interface, like cell phones, utilize BGA/CSP structure for miniaturization of circuits. These structures are subjected to severe thermal loads due to environment of use. Starting with a microstructure of a failed board due to thermal cycles, the stresses/strains in this structure were analyzed from –408C to 1258C. In the finite element models (ABAQUS), we represented the structure as a composite of three‐dimensional (3‐D) elastic materials. The model showed stress/strain/energy concentrations at the actual failure points. The model also provided a route to improved durability by reducing these failure potentials, through change in the substrate of the printed circuit board (PCB). We observed significant reduction in failure potential when resin coated copper was replaced by THERMOUNT1 in PCB. This improved performance can be directly related to better‐matched modulus and coefficient of thermal expansion (CTE) of the PCB substrate to the chip (silicon). A more sophisticated model is under construction, where the time dependent material properties and non‐linear effects such as solder creep will be included.

Integrated Electronic Interconnection Solutions With Non-Woven Aramid

Every economic studies and OEM surveys show that communications and high-speed computing are the fastest growing electronics applications. The old rules for making these electronic devices are being broken such that whenever possible, space and weight are being saved, while still maintaining reliability and cost of the system. The consumer mobile phone exemplifies this technology trend. Many models are now equipped with personal organizers, multimedia, and wireless communications capabilities. To achieve these, there is much interest in homogeneous materials systems to improve mechanical and electrical performance from the semiconductor packaging to the assembled devices. System-on-chips (SOC), system-on-package (SOP), and rigid-bend-to-fit (3D) packaging are examples of the technologies being explored to get the most performance per space. Aramid substrates are used in 100% PWB and HDI microvia stack-ups in IC packaging, handheld devices, high-end computing, backplanes, and military/ avionics, while providing reliability and reduced overall costs. The talk will focus on why non-woven aramid substrates as homogeneous materials systems improve mechanical and electrical performance from the semiconductor packaging to the assembled devices. We will share data showing the versatility and applicability of aramid non-woven reinforced substrates impregnated with various resins, including why and how non-woven aramid substrates are laser ablateable; are able to be made thin and handleable, lightweight and bendable, thermally and dimensionally stable; and has low CTE able to be used in 100% PWB and HDI microvia stack-ups in IC packaging, handheld devices, high-end computing, backplanes, and military/ avionics, while providing reliability and reduced overall costs.Copyright