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The detection of subsurface objects by near infrared ͑NIR͒ spectroscopy and imaging has usually been done with a large number of source positions and a corresponding large number of detector positions. Significant signals have been obtained with a multitude of sources and detectors, to be exact, 4 multiwavelength light emitting diodes ͑LEDs͒ and 16 nearby detectors photodiode silicon diode detectors. A great simplification is made by a dedicated device in which two out of phase sources and a single detector, used in a differential circuit, enable sensitive detection of the appearance of a functionally induced inhomogeneity, for example, a breast cancer or a brain functional signal. By using two LED NIR sources in antiphase at a wavelength appropriate to blood volume increment for the in detection of breast cancer angiogenesis, it is possible to design and construct a very efficient handheld scanner which will indicate the presence of a subsurface angiogenesis by creating imbalance of the optical patterns of the two 800 nm LED sources. Localization and an estimate of the size of the subsurface object may be obtained by scanning the device serially across the breast, as shown in a dynamic 1 cm 3 model tumor to be valid to a depth of 5 cm.

There has been a significant research effort on area-array flip-chip solder joint technology in order to reduce package footprint, enhance current handling capability, and improve heat dissipation. However, there is a lingering concern over cyclic fatigue of solder alloys by thermo-mechanical stresses arising from mismatched thermal expansion coefficients of expansion among the various components of the package. In this paper, some strategies taken to improve the reliability of solder joints on power devices in single-device and multi-chip packages are presented. A strategy for improving solder joint reliability by adjusting solder joint geometry, underfilling and utilization of flexible substrates is discussed with emphasis on triple-stacked solder joints that resemble the shape of an hourglass. The hourglass shape relocates the highest inelastic strain away from the weaker interface with the chip to the bulk region of the joint while the underfill provides a load transfer from the joints. Flexible substrates can deform to relieve thermo-mechanical stresses. Thermal cycling data show significant improvements in reliability when these techniques are used. The design, testing, and finite-element analyses of an interconnection structure, termed the Dimple-Array Interconnect (DAI), for improving the solder joint reliability is also presented. In the DAI structure, a solder is used to join arrays of dimples pre-formed on a metal sheet onto the bonding pads of a device. Finite-element thermo-mechanical analyses and thermal cycling data show that the dimple-array solder joints are more fatigue-resistant than the conventional barrel-shaped solder joints in flip-chip IC packages.

We simulated the effects of compression of the breast on blood volume and tissue oxygenation. We sought to answer the question: how does the compression during breast examination impact on the circulatory systems of the breast tissue, namely blood flow, blood pooling, and oxygen concentration? We assumed that the blood was distributed in two compartments, arterial and venous. All the parameters were expressed with oxy- and deoxyhemoglobin quantities and were measured with a non-invasive method, Near Infrared Spectroscopy (NIRS). The simulated data showed that the blood volume pool in the breast decreased due to lower arterial flow and higher venous outflow, as the breast was squeezed under 100 cm H2O with a 10 cm diameter probe (or 78 cm2). The blood volume was reversed when the pressure was released. The breast venous oxygen saturation dropped, but overall tissue saturation (presenting NIRS signal, volume weighted average saturation) was increased. The results showed that simulation can be used to obtain venous and average oxygen saturation as well as blood flow in compressed breast tissues.

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