Circuit board cleaning

Apart from obvious dry cleaning applications, potential applications of C02-based microemulsions include (i) printed circuit board cleaning, (ii) extraction of contaminants from soils, (Hi) cleaning of polymers, foams, aerogels, porous ceramics, and laser optics, (iv) regeneration of activated carbon beds or catalysts, and (v) the separation of dyestuffs from textiles. 

SAFETY SOLVENT FOR CIRCUIT BOARD CLEANING AND OEFLUXING... 

As noted previously, the major use of turpentine at one time was as a solvent, particularly in varnish formulations, and as a thinner for linseed-oil-base paints. Petroleum-based solvents have now replaced turpentine for these purposes. However, turpentine or turpentine fractions are packaged in small containers (up to 1 gallon) for the retail market for home use as paint thinners (including use with artist s oil paints) and as a general-purpose solvent. Turpentine fractionation products may recover some of the historical solvent use by replacing chlorofluoro-carbons in the specialized circuit board cleaning market (1). 

CFC-11 (CCI3F) Plastic foam blowing solvent, electronic circuit board cleaning solvent 0.063 2.4... 

Trichloroethane and other chlorinated solvents are used for vapor degreasing (84—90). Other uses include cold metal cleaning, printed ckcuit board cleaning, and as a solvent for inks, coatings, adhesives, and aerosols. 1,1,1-Trichloroethane is an excellent solvent for development of photoresist polymers used in printed ckcuit board manufacture (see Integrated circuits Photoconductivepolymers). 

Cleaning Supercritical fluids such as CO9 are being used to clean and degrease quartz rods used to produce optical fibers, produc ts used in the fabrication of printed circuit boards, oily chips from machining operations, and precision bearings in militaiy applications, and so on. Here, CO9 replaces convention chlorocarbon or chlorofluorocarbon solvents. 

Aqueous and semi-aqueous cleaning systems, used for printed circuit boards and other industrial degreasing operations (Mandich and Krulik, 1992 Davis et al., 1994)... 

Phosphates and phosphonates are valuable contents of cleaners used for technical purposes especially when anticorrosive behavior is also required. Phosphoric acid esters are a component of aqueous cleaning compositions for printed circuit boards [212]. 

Films of PATE were cast on copper plated circuit boards. Typical solutions contain from 8% to 17% PATTE solids and 0.02% Flourad FC 135 surfactant. No other additives, such as adhesion promoters, sensitizers, viscosity modifiers or stabilizers, were employed in the formulations. Films of 0.001 to 0.008 inches wet film thickness were cast on abrasively cleaned circuit boards and then oven dried for 5 minutes at 105 °C. Thus, in each case the... 

The analysis of tetramethylammonium hydroxide (TMAH) solutions manufactured by SACHEM Inc. of Cleburne, Texas, includes the determination of trace elements. These elements cause less-than-optimum performance of integrated circuit boards manufactured by SACHEM s customers that use these solutions in their processes. Alkali and alkaline earth metals (e.g., Li, Na, K, Mg, Ca, and Ba) can reduce the oxide breakdown voltage of the devices. In addition, transition and heavy metal elements (e.g., Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ag, Au, and Pb) can produce higher dark current. Doping elements (e.g., B, Al, Si, P, As, and Sn) can alter the operating characteristics of the devices. In SACHEM s quality control laboratory, ICP coupled to mass spectrometry is used to simultaneously analyze multiple trace elements in one sample in just 1 to 4 min. This ICP-MS instrument is a state-of-the-art instrument that can provide high throughput and low detection Emits at the parts per thousand level. Trace elemental determination at the parts per thousand level must be performed in a clean room so that trace elemental contamination from airborne particles can be minimized. 

SACHEM Inc., located in Cleburne, Texas, is a producer of high-purity bulk chemicals for companies that have high-purity requirements in their chemical processing. As stated in Workplace Scene 1.2, one of their products is tetramethylammonium hydroxide (TMAH), which is sold to semiconductor industries. The analysis of TMAH for trace anions such as chloride, nitrate, nitrite, and carbonate is critical for SACHEM s quality control laboratory. If these ions are present on the integrated circuit boards manufactured by one of their semiconductor customers, they may cause corrosion severe enough to affect the functionality and performance of the electronic devices in which the circuit boards are used. In SACHEM s quality control laboratory, ion chromatography procedures have been developed to measure the anion concentrations in TMAH. Because the concentration levels are trace levels, a clean room environment, like that described in Workplace Scene 1.2, is used. A special procedure for carbonate analysis is required so that the absorption of carbon dioxide from the atmosphere can be minimized. 

Uses Manufacture of fluorocarbon refrigerants, fluorocarbon plastics, and propellants solvent for natural products analytical chemistry cleansing agent soil fumigant insecticides preparation of chlorodifluoromethane, methyl fluoride, salicylaldehyde cleaning electronic circuit boards in fire extinguishers. 

Electronic cleaning Defluxing of printed circuit boards Soldering rosin... 

Finally, steps can also be taken to prevent the contaminant from ever entering the process. For example, the development of low-solids no clean rosin fluxes for soldering printed circuit boards completely eliminates the need for a cleaning process (Sapre, 1990). 

Trichlorotrifluoroethane (CFC 113) was widely used in the electronics industry for the removal of soldering flux residues from printed circuit boards, for degreasing components in the precision engineering industry, and for the dry cleaning of garments. 

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