Timothy J. Harpster

A passive humidity monitoring system for in situ remote wireless testing of micropackages

Reports a small passive wireless humidity monitoring system (HMS) for continuous remote monitoring of humidity changes inside miniature hermetic packages, presents its application in determining hermeticity of an implantable biomedical package, and presents long-term performance results obtained from packages implanted in guinea pigs. This 7/spl times/1.2/spl times/1.5 mm/sup 3/ system consists of a high-sensitivity capacitive humidity sensor that forms an LC tank circuit together with a hybrid coil wound around a ferrite substrate. The resonant frequency of the circuit changes when the humidity sensor capacitance changes in response to changes in humidity. The HMS can resolve humidity changes of /spl plusmn/2.5% RH over a 2-cm range. The resolution is sufficient enough to monitor internal package humidity for either in vitro or in vivo testing.

A passive wireless integrated humidity sensor

This paper presents a single-chip integrated humidity sensor (IHS) capable of wireless operation through inductive coupling with a remote transmitter. The 1.5/spl times/0.5/spl times/8mm/sup 3/ sensor chip consists of a planar electroplated copper coil (20 /spl mu/m thick, 30 /spl mu/m pitch, and 23 turns) and a silicon substrate separated by a 4100-5600 /spl Aring/ polyimide film. The resonant frequency of the IHS changes with humidity and the measured sensitivity ranges from 4-16 kHz/%RH. Measurements show a hysteresis of 4.5%RH over a range of 30-70%RH for a 5600 /spl Aring/-thick polyimide film IHS.

A passive humidity monitoring system for in-situ remote wireless testing of micropackages

This paper reports a small passive wireless humidity monitoring system (HMS) for continuous monitoring of humidity changes inside miniature hermetic packages, presents its application in determining hermeticity of an implantable biomedical package, and presents long-term performance results obtained from packages implanted in guinea pigs. This 7/spl times/1.2/spl times/1.5 mm/sup 3/ system consists of a high-sensitivity capacitive humidity sensor that forms an LC tank circuit together with a hybrid coil wound around a ferrite substrate. The resonant frequency of the circuit changes when the humidity sensor capacitance changes in response to changes in humidity. The HMS can resolve humidity changes of /spl plusmn/2.5%RH over a 2 cm range. The resolution is sufficient enough to monitor internal package humidity for either in in-vitro or in-vivo testing.

Long-term testing of hermetic anodically bonded glass-silicon packages

This paper reviews long-term test results obtained from a series of tests on glass-Si hermetically sealed packages. Results are presented from: 1) a 6.7-year ongoing room temperature phosphate buffered saline (PBS) soak test of 4 packages; 2) a 2.3-year ongoing in-vitro 97/spl deg/C PBS soak test of a single package; and 3) in-situ hermeticity and biocompatibility tests from 12 packages implanted in 4 guinea pigs - 3 packages implanted in each of 2 guinea pigs for 1-month and another 2 guinea pigs for 19-months, and 22-months. The long-term room temperature soak test is the longest running of any micropackage reported to date.

Long-term hermeticity and biological performance of anodically bonded glass-silicon implantable packages

This paper reviews long-term test results obtained from a series of tests on glass-silicon (Si) hermetically sealed packages. Results are presented from 1) a 9.9-year ongoing room temperature phosphate-buffered saline (PBS) soak test of four packages; 2) accelerated soak tests in high temperature saline of 28 samples resulting in an extrapolated mean-time-to-failure (MTTF) at 37/spl deg/C of 177 years; 3) a 2.7-year in vitro 97/spl deg/C PBS soak test of a single package; and 4) in situ hermeticity and biocompatibility tests from 12 packages implanted in four guinea pigs-three packages implanted in two guinea pigs (each) for 1 month and another two guinea pigs for 20 and 22 months. All of the packages remained hermetically sealed over the lifetime of the implant. A detailed histological report of the implants is provided suggesting that they elicit no profound adverse reaction from the body.

Field-assisted bonding of glass to Si-Au eutectic solder for packaging applications

A new approach for high-yield bonding of Pyrex 7740 glass to a silicon wafer using field-assisted glass to Si-Au eutectic bonding is presented. It is found that by applying an anodic bias, as is typically used in direct Si-glass wafer bonding, in a standard Si-Au eutectic bond, one can obtain a significant improvement in bond quality, uniformity, and reproducibility. Experimental results obtained from bonded silicon wafers and Pyrex 7740 glass wafers using silicon-gold eutectic solder on planar and non-planar surfaces are presented. Samples bonded at 410/spl deg/C show bond strengths of >5.24MPa which falls within the range 2 to 25MPa reported for direct Si-Pyrex anodic bonding. Other samples bonded at 450/spl deg/C show a bond strength >31.4MPa.

1.09 – Wafer Bonding

This chapter reviews different wafer bonding techniques and discusses their advantages and disadvantages. After providing a brief review of applications of wafer bonding technologies, requirements and desirable characteristics for these technologies are listed. Wafer bonding technologies are discussed under three main categories: direct wafer bonding (DWB), mediated wafer bonding (MWB), and specialized techniques developed for localized and selective heating of wafers. DWB techniques reviewed in this chapter are field-assisted anodic bonding, fusion bonding (including hydrophobic and hydrophilic, high and low temperature, and vacuum- and plasma-assisted), and chemical assisted bonding of glass surfaces. MWB techniques reviewed are anodic bonding using deposited films, thermocompression, solder and eutectic, bonding using glass films, and polymer-assisted wafer bonding. Finally, selective wafer heating techniques reviewed include localized resistive heating, radio frequency (RF) and microwave and electromagnetic heating, ultrasonic bonding, rapid thermal processing (RTP), and laser-assisted bonding. This chapter compares these technologies and ends with concluding remarks.

Increasing Condenser Capacity Without Adding Tubes to Support a Station Uprate

A station uprate provides an economical opportunity to improve the generation capacity of a power plant if all the major system components are able to handle the effects of increased generation. The magnitude of uprate from increased steam generation will be limited by the maximum capacity of the weakest link in the cycle, which for many plants is the condenser. The condensers on many units are already pushed to their limit. This is especially true if a cooling tower is employed, where the condenser inlet cooling water temperatures are high on high wet-bulb temperature days. This condition forces many units to throttle down load to prevent excursions above the backpressure limits on their turbines. For condensers limited by the present duty, however, the options have been historically limited to rebundling the whole condenser with a larger surface area design and perhaps changing the tube material to a material with a higher heat transfer coefficient. Recently, a very low cost option has been demonstrated that should be considered by any plant looking to increase condenser duty or prevent station power reductions. Advances in the proper management of steam, condensate and noncondensable flows have permitted an upgrade for almost all vintage condensers, unlocking inactive surface area without a bundle replacement or complete redesign. This paper reports the results of a condenser retrofit effort, with emphasis on an upgrade applied to a load limited condenser concurrent with a major reduction in its operating backpressure. The performance of the condenser is presented before and after the upgrade showing significant backpressure reduction and heat transfer improvement accompanied by exceptional condensate chemistry results. It will be shown that 30% of the effective condenser surface area (or similarly, an additional 30% average heat transfer coefficient) was unlocked by activating the previously idle surface area.Copyright