Etching solution

Ammonium chloride has a number of iadustrial uses, most importantiy ia the manufacture of dry-ceU batteries, where it serves as an electrolyte. It is also used to make quarryiag explosives, as a hardener for formaldehyde-based adhesives, as a flame suppressant, and ia etching solutions ia the manufacture of ptinted circuit boards. Other appHcations iaclude use as a component of fluxes ia ziac and tin plating, and for electrolytic refining of ziac. 

Minor and potential new uses include flue-gas desulfurization (44,45), silver-cleaning formulations (46), thermal-energy storage (47), cyanide antidote (48), cement additive (49), aluminum-etching solutions (50), removal of nitrogen dioxide from flue gas (51), concrete-set accelerator (52), stabilizer for acrylamide polymers (53), extreme pressure additives for lubricants (54), multiple-use heating pads (55), in soap and shampoo compositions (56), and as a flame retardant in polycarbonate compositions (57). Moreover, precious metals can be recovered from difficult ores using thiosulfates (58). Use of thiosulfates avoids the environmentally hazardous cyanides. 

Resists. Resists are temporary, thin coatings appHed to the surface of the copper-clad laminate. After patterning, these films act as masks that are chemically resistant to the cleaning, plating, and etching solutions used to define the circuit traces of the PWB. Both nonphotosensitive and photosensitive types are used. 

Fig. 6. Top Morphology of FPL surface following fluorine contamination. This is to be compared to the standard FTL morphology of Fig. 14. Middle Climbing drum peel (CDP) strength as a function of F surface concentration. Bottom F concentration on FPL surfaces following doping the FPL etch solution and the rinse water with NaF. The dotted line corresponds to the surface concentration with which the CDP strength began to decrease. Adapted from Ref. [37].

Fig.. 37. Part of a Morphology Catalog illustrating the unacceptable morphologies resulting from contaminated etch solution (a) FPL with - 600 ppm F, and (b) FPL with - 400 ppm CC 1169).

Couper reports cracking of an Fe-36 Ni alloy in 10-55 days in this medium. Radd eta . have noted cracking of Fe-36 Ni alloys at ambient temperatures in an unspecified environment, but this possibly may have been residual traces of acid copper chloride etching solution. 

Etch primers are widely used. They are mostly based on polyvinyl butyral and contain chromates and phosphoric acid. They are said to act both as primers and as etching solutions because it is believed that the chromates and phosphoric acid form an inorganic him, which provides adhesion, while oxidised polyvinyl butyral provides an organic him. For direct application to new galvanised steel, the best known primers are based on calcium orthoplumbate pigment and metallic lead, but these are now less used for environmental reasons. Zinc-dust paints and zinc-phosphate pigmented paints are also used, but the trend is to use pretreatments to assure good adhesion. 

The polymer must resist the etching solutions used to remove the unwanted surface layers of the silicon wafer as the image is transferred to the microchip. 

Turner DRJ (1961) Saturation currents at n-type silicon and germanium electrodes in chemical etching solutions. Electrochem Soc 108 561-563... 

In a printed circuit board etching line using copper(II) chloride solution, 45 wt% hydrogen peroxide solution was used to recover the copper salts. The peroxide header tank became contaminated with trace amounts of the etching solution, and catalytic decomposition of the peroxide led to a pressure burst of the tank. 

In mixtures of the 3 components intended for use as chemical polishing or etching solutions [1], cone, peroxide must not be used [2],... 

Kyuchoukov, G. Mishonov, I. A new extractant mixture for recovery of copper from hydrochloric etching solution. Solvent Extr. Ion Exch. 1993, 11, 555-567. 

Etch times were investigated for aluminum and SU8 sacrificial cores patterned on silicon. Samples were periodically removed from the acid etch solution, and the amount of sacrificial core that was removed was measured using an optical microscope. We found that the etch length as a function of time follows the equation... 

The surface segregation of Sr is of particular interest as SrO affects the surface reactivity and the activation behavior of the LSM electrode. Jiang and Love [36] studied the activation behavior of Lao72Sr018Mn03 cathode after treatment of the LSM coating with diluted hydrochloric acid (HC1) solution. The etched solution... 

Hold grids for 10 20 s in an etching solution composed of saturated sodium ethoxide in absolute ethanol diluted to 50% with absolute ethanol. 

For this reason, it is possible to obtain even fine pattern areas with a clean reproduceability. The rubber plates obtained with zinc and other metal plates require considerable exacting control of shoulder angles and actually desired adjustments can not be made at will. The reason for this exacting control of shoulder angles may be because the shape of shoulder is dependable upon acid concentration of etching solution, deteriority degree of... 

The etch rate is further increased if H202 is added to the solution, as shown in Fig. 2.5 b. At such low rates the reaction is controlled by the kinetics of the reaction at the interface and not by diffusion in the solution. This etching solution is therefore found to be perfect to remove micro- and mesoporous silicon selectively from a bulk silicon substrate or to increase the diameter of meso- or macropores in an well-controlled, isotropic manner [Sa3],... 

Tab. 2.2 Etch rates of common materials used in semiconductor manufacturing in the most popular wet etching solutions. Note that this table gives only a rough overview etch rates may vary significantly depending on the details of thin film formation parameters, etchant composition, temperature and additives, e.g. surfactants.

Table 2.2 gives an overview of the most common materials in silicon device manufacturing and their etch rates in different etching solutions. 

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