Marvin W. Cowens

Ultraviolet downconverting phosphor for use with silicon CCD imagers

The properties and application of a UV downconverting phosphor (coronene) to silicon charge coupled devices are discussed. Measurements of the absorption spectrum have been extended to below 1000 A, and preliminary results indicate the existence of useful response to at least 584 A. The average conversion efficiency of coronene was measured to be ~20% at 2537 A. Imagery at 3650 A using a backside illuminated 800 x 800 CCD coated with coronene is presented.

Coronene and liumogen as VUV sensitive coatings for Si CCD imagers: a comparison

Phosphor coatings have long been employed in the detection of UV radiation. With the interest in the use of silicon charge coupled device (CCD) imagers as the detector for the space telescope and other space-borne astronomical missions, a UV sensitive phosphor is desired the emission spectrum of which usefully matches the spectral response of the CCD. Such a phosphor would provide an unparalleled opportunity to image in the UV, the visible, and near IR wavelengths with the same detector. A recent study has suggested that coronene and sodium salicylate (which emit at 500 and 420 nm, respectively) are the most promising candidate phosphors. The potential of a third organic phosphor, liumogen, is the subject of this Letter.

800 X 800 Charge-Coupled Device Image Sensor

The design and performance of an 800 X 800 pixel charge-coupled device (CCD) imager are described. This device is fabricated utilizing a three-phase, three-level polysilicon gate process. The chip is thinned to 8 um and is employed in the rear illumination mode. Detailed measurements of the device performance, including dark current as a function of temperature, linearity, and noise, are presented. The device is coated with an ultraviolet (UV) downconverting phosphor which allows imaging with the same device over an extremely wide optical bandwidth.

Texas Instruments (TI) 800X800 Charge-Coupled Device (CCD) Image Sensor

The design and performance of the Texas Instruments 800 x 800 CCD imager are described. This device is fabricated utilizing a three phase, three level polysilicon gate process. The chip is thinned to ~ 8 μm and is employed in the rear illumination mode. Detailed measurements of device performance including dark current as a function of temperature, linearity, and noise are presented. The device is coated with a UV downconverting phosphor which allows imaging with the same device over an extremely wide optical bandwidth.

Effect of compatibility between fluxes and cyanate ester underfill on lead free flip chip assembly and reliability

The quality and reliability of flip-chip assembly is severely impacted by the compatibility between various materials used in the package. Currently, no-clean fluxes are widely used for the assembly of flip chips. Poor compatibility between the flux residue and the underfill can lead to the formation of voids, and consequently, reliability problems. Therefore, a major concern for flip-chip assembly is the compatibility between the flux residues and the underfill. The principal objective of this research was to develop a flux for lead-free packaging, which would be compatible with high performance moisture resistant cyanate ester-based underfills. During this study, commercially available fluxes, along with tailor made epoxy-based flux, were tested for their compatibility with the underfill. The results indicated that the assembly process window for the rosin-based fluxes was much wider than the epoxy-based fluxes. Synthetic flux had poor soldering performance and relatively poor compatibility with the cya...