Waveguide losses in thin film polyimides using waveguide loss spectroscopy and photothermal deflection spectroscopy as a function of cure cycle and structure were studied. Fluorinated sidegroups on the polyimide backbone lead to decreases in birefringence and absorption. The primary waveguide loss mechanism is absorption, not scattering. Waveguide losses as low as 0.4 dB/cm at 800 nm have been measured. Losses as low as 0.3 dB/cm at 1300 nm can be inferred from the photothermal deflection spectroscopy.
We report studies of the optical and electro-optic properties of guest–host polymeric nonlinear optical materials based on aromatic, fluorinated, fully imidized, organic soluble, thermally, and photochemically crosslinkable, guest–host polyimides. We have introduced temperature stable nonlinear optical chromophores into these polyimides and studied optical losses, electric field poling, electro-optic properties, and orientational stability. We measured electro-optic coefficients of 5.5 and 12.0 pm/V for ((2,6-Bis(2-(3-(9-(ethyl)carbazolyl))ethenyl)4H-pyran-4-ylidene)propanedinitrile (4-(Dicyanomethylene)-2-methyl-6-(p -dimethylaminostyryl)-4H-pyran) DCM-doped guest–host systems at 800 nm using a poling field of 1.3 MV/cm. Poling induced nonlinearities in single-layer films were in agreement with the oriented gas model, but were lower in three-layer films due to voltage division across the layers.
The use of a “microvia” process for the fabrication of high density printed circuit boards and IC packages offers many advantages in terms of producing high interconnect density, cost competitive substrates for portable communications products. Motorola has put into production a sequential build HDI process that uses photoimageable dielectrics and semi‐additive copper metallization on a PWB substrate. Design capabilities for the current HDI process are 100μm/100μm line/space and 125μm /250μm via/pad. Plated through holes in the substrate are filled with a screen printable ink so that traces can be routed over the through hole area. This design capability meets routing and reliability requirements for current Motorola portable products. Future PWBs and IC packages, however, will need higher density features and higher performance materials. These features include finer line width, multiple HDI layers for routing dense SMT packages, low loss dielectrics for RF circuitry, higher Tg, and lower moisture dielectrics for DCA and IC package assembly.
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