Micro-hole method

The hardness of carbides can only be deterrnined by micro methods because of britdeness, the usual macro tests caimot be used. Neither can the extremely high melting points of the carbides be readily deterrnined by the usual methods. In the so-called Priani hole method, a small hoUow rod is placed between two electrodes and heated by direct current until a Hquid drop appears in the cavity. The temperature is determined pyrometricaHy. When high temperature tungsten tube furnaces are used, the melting point can readily be estimated by the Seger-type cone method. The sample may also be fused in a KroU arc furnace and the solidification temperature determined. 

Micro- (and even nano-) electrode arrays are commonly produced with photolithography and electronic beam techniques by insulating of macro-electrode surface with subsequent drilling micro-holes in an insulating layer [136, 137], Physical methods are, however, expensive and, besides that, unsuitable for sensor development in certain cases (for instance, for modification of the lateral surface of needle electrodes). That s why an increasing interest is being applied to chemical approaches of material nanostructuring on solid supports [140, 141],... 

R. Wiithrich, U. Spaelter, Y. Wu, H. Bleuler A systematic characterisation method for gravity feed micro-hole drilling in glass with Spark Assisted Chemical Engraving (SACE). Journal of Micromechanics and Microengineering 16 (2006), p. 1891. 

An alternative approach to decrease the time constant of electrochemical systems rests on the use of the miniaturized ITIES. Micron-scale ITIES use a micropipette to support the aqueous phase [98]. Subsequently an alternative approach, using micro-holes formed by laser ablation of thin polymer films, was reported [99]. The advantage of the micron-scale approach is that the radial diffusive flux to such an inlaid interface reaches a steady state, so the problems of transient current methods due to the double-layer charging constant are avoided. The low currents measured at such interfaces, due to their small size,... 

Recently a detailed study has been made of the methods required to obtain spectra of micro and ultra-micro amounts of sample 117). A focussing micro-illuminator is used for the detection of 1-10 micrograms of samples. Often, one can obtain the spectrum of impurities like fish-eyes in plastics by merely punching a hole the size of the imperfection in a masking material like cardboard and run the spectrum until the signal-to-noise level has reached a sufficient value to make an identification of the impurity. One can carry out a similar measurement in regions where the impurity appears to be absent and subtract the two spectra to enhance the spectra of the impurity relative to the more dominant polymer. 

The micro mixer was made by standard photolithographic and etching methods on an ultra-flat quartz substrate [160], The microstructure created in this way was shielded by a cover plate by thermal bonding. This cover plate contained access holes for fluid supply and withdrawal. Internal surfaces of the chip were activated to have a high density of silanol groups needed for the EOF transport... 

Metal-metal eutectics have been studied for many years due to their excellent mechanical properties. Recently, oxide-oxide eutectics were identified as materials with potential use in photonic crystals. For example, rodlike micrometer-scaled microstructures of terbium-scandium-aluminum garnet terbium-scandium per-ovskite eutectics have been solidified by the micro-pulling-down method (Pawlak et al., 2006). If the phases are etched away, a pseudohexagonally packed dielectric periodic array of pillars or periodic array of pseudohexagonally packed holes in the dielectric material is left. 

Figure 14 Fabrication procedure for the pile-up microreactor. (1) Photolithography Conventional photolithography/wet etching methods were applied. The back side of the glass plate was covered with polyolefin tape during the HF treatment. (2) Drilling Penetrating holes were drilled at the inlet and outlet ports of the micro-channel circuit. (3) Thermal bonding The required number of glass plates with microchannels and one cover plate were laminated and bonded thermally at 650°C.

Another advantage of the pattern-plating method is its ability to form padless micro-via holes of a diameter ranging from 0.012 to 0.016 in. Micro-via holes enable better usage of conductor channels, thereby increasing the connective capacity of the board. 

There is no perfect, nondestructive test method for evaluating the reliability of micro via holes. It is not easy to create suitable conditions for uniform plating of copper in very small holes. As a result, cross-sectional inspections should be done periodically. Also, a daisy-chain coupon arranged beside the circuits in the work should be tested periodically. 

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