Ultrathin flip-chip semiconductor die packaging on paper substrates is an enabling technology for a variety of extremely low-cost electronic devices with huge market potential such as RFID smart forms, smart labels, smart tickets, banknotes, security documents, etc. Highly flexible and imperceptible dice are possible only at a thickness of less than 50 μm, preferably down to 10-20 μm or less. Several cents per die cost is achievable only if the die size is ≤ 500 μm/side. Such ultrathin, ultra-small dice provide the flexibility and low cost required, but no conventional technology today can package such die onto a flexible substrate at low cost and high rate. The laser-enabled advanced packaging (LEAP) technology has been developed at the Center for Nanoscale Science and Engineering, North Dakota State University in Fargo, North Dakota, to accomplish this objective. Presented are results using LEAP to assemble dice with various thicknesses, including 350 μm/side dice as thin as 20 μm and less. To the best of our knowledge, this is the first report of using a laser to package conventional silicon dice with such small size and thickness. LEAP-packaged RFID-enabled paper for financial and security applications is also demonstrated. The cost of packaging using LEAP is lower compared to the conventional pick-and-place methods while the rate of packaging is much higher and independent of the die size.
Direct Write Technologies are reaching the goal of entirely printable microelectronic devices on flexible polymeric
substrates. In the present work, nanoparticle inks deposited on low temperature polyimide substrates using Maskless
Mesoscale Material Deposition (M3D®) technology were laser sintered using a continuous wave 1.06 micron Nd:YAG
laser. In-situ measurements were made during sintering to capture the dynamic change in bulk resistivity as a function of
deposited energy per volume of sintered material. It was shown that less than 0.05-μJ/μm3 started the sintering and 0.34-μJ/μm3 was enough for sintering the deposited samples regardless of initial resistance.
We have demonstrated a narrowband Littman configuration dye laser longitudinally pumped by the second harmonic of a 250 Hz pulse repetition frequency microchip laser with up to 50 microjoule pulse energies at 532 nm. Rhodamine 6Gd ye in methanol with a 5 cm cavity length produced 9 microjoule pulses with a slope efficiency of 20% at the peak intensity. The dye laser can be tuned from 550 to 575 nm. A 532 nm pump threshold below 4 microjoules was observed. Adding tunability to compact, economical microchip lasers with a spectrally narrow pulsed dye laser provides ideal characteristics for biotechnological applications.
Our efforts to chemically analyze aromatic hydrocarbons by resonance enhanced multiphoton ionization (REMPI) spectroscopy has been extended to mixtures. Indene has been detected in the headspace over coal tar and creosote via a characteristic band at 287.9 nm. Both sample and data collection occur for ambient pressure and temperature conditions. The indene spectra have also been examined for the effects of pressure broadening, which are discernible but small. High resolution absorbance spectra establish the feasibility for a similar REMPI strategy to detect benzene and toluene via an on-off resonance strategy, similar to that practiced in differential absorbance LIDAR (DIAL) and differential absorbance optical spectroscopy. Angular/wavelength acceptance criteria for the frequency doubling process, by which the tunable ultraviolet light is generated, are considered. Options for ultraviolet tunable solid state lasers, which are the key to real-time monitors based on REMPI technology, are assessed.
The 1+1 and 2+2 resonance-enhanced multiphoton ionization (REMPI) spectra of gas phase indene near the origin of the first electronic transition at 287.9 nm are reported. This work relates to chemically-specific measurements of trace organic constituents in ambiant air. The spectra were acquired to help assess options for on- and off-resonance REMPI, similar in concept to differential absorbance LIDAR (DIAL) and differential optical absorbance spectroscopy (DOAS). The 1+1 REMPI spectrum for indene at 50 ppbv concentration in air compares well with published high resolution absorbance spectra obtained for much longer pathlength and higher sample concentration. Extensive sequence band structure is observed near the origin. The rotational contours of the origin and sequence bands consist of narrow, nearly symmetric features, accompanied by a lower intensity broad sideband shading to the red. The narrow feature is not as narrow as in the highest resolution absorbance spectrum and cannot be explained in terms of the laser linewidth or intensity (saturation) broadening at high laser power; pressure broadening may be the source. We also report styrene 1+1 REMPI spectrum to document instrument improvements made since our previous study.
Ion mobility spectrometry with a photoemissive electron source is a promising approach for monitoring vapors of highly electronegative species such as chlorinated solvents and explosives. Electrons are generated over well-defined intervals by ultraviolet irradiation of a metal plate or metal-coated window by either a flashlamp or a pulsed laser beam, so no gating of the drift process is required. The negative ion mobility spectrum of air exhibits features predominately due to clusters of oxygen anion with water molecules. These species readily transfer electrons to chlorinated aliphatic compounds that undergo dissociative electron attachment to generate chloride ions. The ion mobility spectra change in a predictable fashion, permitting real-time detection of chlorinated species at low ppmV concentration. In this presentation we shall describe our methodology, display the response characteristics of our instrument, and summarize our investigations of the relevant ion-molecule reactions.
The production of acetaldehyde was monitored during the simulated atmospheric oxidation of ethyl-3-ethoxyproprionate (EEP), a paint component. The detection of acetaldehyde in ambient pressure air to below 1 ppbv levels was demonstrated using resonance enhanced multiphoton ionization (REMPI) via the two photon resonant 3 s implied by n Rydberg transition at 363.5 nm. The reactions were carried out at room temperature in 100 L FEP Teflon bags while the air was continuously pumped through a parallel plate REMPI cell. Banks of black lights and sun lights provided UV radiation in the 300-450 nm region to simulate atmospheric photocatalysis by the sun. The REMPI measurements confirmed previous GC/MS and FTIR measurements but in real-time with higher sensitivity. The technique can be directly applied to the detection of atmospheric pollutants and real-time monitoring of manufacturing processes.
We have developed and begun to field test a very sensitive method for real-time measurements of single-ring aromatic hydrocarbons in ambient air. In this study, we focus on the efficient 1 + 1 resonance enhanced multiphoton ionization (REMPI) of the BTEX species in the narrow region between 266 and 267 nm. We particularly emphasize 266.7 nm, a wavelength at which both benzene and toluene exhibit a sharp absorbance feature and benzene and its alkylated derivatives all absorb. An optical parametric oscillator system generating 266.7 nm, a REMPI cell, and digital oscilloscope detector are mounted on a breadboard attached to a small cart. In the first field test, the cart was wheeled through the various rooms of a chemistry research complex. Leakage of fuel through the gas caps of cars and light trucks in a parking lot was the subject of the second field test. The same apparatus was also used for a study in which the performance of the REMPI detector and a conventional photoionization detector were compared as a BTEX mixture was eluted by gas chromatography. Among the potential applications of the methodology are on-site analysis of combustion and manufacturing processes, soil gas and water headspace monitoring, space cabin and building air quality, and fuel leak detection.
Volatile aromatic hydrocarbons such as benzene, toluene, ethylbenzene, and xylenes (BTEX), and styrene, aniline, and phenol can be directly and sensitively detected in ambient air by resonance-enhanced multiphoton ionization (REMPI) spectroscopy. The REMPI spectra closely resemble conventional absorbance spectra, but the REMPI technique is far more sensitive. Detection limits for directly focused tunable laser light into the ionization cell are less than 10 ppbv for BTEX and less than 1 ppbv for styrene, aniline, and phenol. Benzene in aqueous solution was remotely detected down to concentrations at the (mu) g/L level by a headspace analysis in which light was delivered to the ionization cell over a 20-meter long optical fiber.