Solvent and chemical etching

Etching is another preparation method that potentially enhances the information available by microscopy while at the same time providing opportunity to introduce many artifacts. Samples are etched and then generally used directly by AFM, or replicas made for TEM, or a conductive coating is applied to the etched surface for imaging by SEM. 

There are two general categories of etching chemical attack or bombardment with charged particles as in plasma and ion beam etching. Chemical attack can be further divided into several categories, including dissolution, which implies the removal of whole molecules of a material as it dissolves acids and other chemicals. Solvent extraction with xylene was used for the study of PE [294] however, dissolution is not recommended due to the artifacts that 

Solvent and chemical etching is a complementary technique in the determination of microstructure. Chemical etching has been arbitrarily divided into two sections for the purpose of this discussion, and acid etching will be dealt with separately. Early studies involved etching to reveal the interior of polymers for replica formation (see Section 4.6). 

Peck and Kaye [296] immersed cellulose acetate specimens in acetone, at -50°C, and then flooded the surfaces with cold absolute alcohol, followed by replication, which showed the skin, orientation, voids, and pigment. Reding and Walter [29] etched PE with hot carbon tetrachloride (high density PE), benzene (low density PE), or toluene, which removed the amorphous material. Bailey [297] used a rapid 

An etching technique was developed to study the structure of crystalline polymers, such as nylon 6, nylon 6,6, and PP [88]. Aromatic and chlorinated hydrocarbons were used to etch surfaces of ground and polished plastic parts, which removed the surface detail with a series 

Solvent and chemical etching is conducted for The same reason as ion and plasma etching, that is as a complementary technique in the determination 

Isopropanol vapor was used to dissolve the matrix in polymer blends [245]. Williams and Hudson [246] etched microtomed blocks of high impact polystyrene so that the rubber particles protruded from the matrix. Later, Kesskula and Traylor [130] removed rubber particles from Hire and ABS polymers by dissolving the matrix in a cyclohexane solution of osmium tetroxide and extracting the dispersed phase for SEM. Olefin particles were removed from impact modified nylon and polyester [6]. Selective etching of the polycarbonate phase with triethyl-amine in a mixture with styrene-acrylonitrile copolymer (SAN) revealed the nature of the blend [247]. 

Amine etching was used to reveal the structure of PET as early as 1959 [55] when PET fibers were etched with n-propylamine for replica formation. Methylamine was also used [248], although the selectivity of the reagent was questioned. Tucker and Murray [249] etched PET filaments with 42% aqueous solutions of n-propylamine at 30°C. Apparently, the first step in the reaction is the removal of the fiber skin and then crazing. A 

Finally, an etching technique was developed to study the structure of crystalline polymers, such 

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Because of the solvent and chemical resistance of acetal copolymer, special etching treatments have been developed for surface preparation prior to adhesive bonding. A chromic acid etch and a hydrochloric acid etch have been suggested. Acetal parts that have been formed by heat treatment or machining should be stress-relieved before etching. 

Commonly used adhesives for both PET and PBT substrates are isocyanate cured polyesters, epoxies, and urethanes. Surface treatments recommended specifically for PBT include mechanical abrasion and solvent cleaning with toluene. Gas plasma surface treatments and chemical etch have been used where maximum strength is necessary. 

Polyethylene terephthalate (PET) and polybutylene terephthalate (PBT) parts are generally joined by adhesives. Surface treatments recommended specifically for PBT include abrasion and solvent cleaning with toluene. Gas plasma surface treatments and chemical etch have been used where maximum strength is necessary. Solvent cleaning of PET surfaces is recommended. The linear film of polyethylene terephthalate (Mylar ) surface can be pretreated by alkeiline etching or plasma for msiximum adhesion, but often a special treatment is unnecessary. Commonly used adhesives for both PBT and PET substrates are isocyanate-cured polyesters, epoxies, and urethanes. Polyethylene terephthalate cannot be solvent cemented or heat welded. 

Poly(phenylquinoxaline—arnide—imides) are thermally stable up to 430°C and are soluble in polar organic solvents (17). Transparent films of these materials exhibit electrical insulating properties. Quinoxaline—imide copolymer films prepared by polycondensation of 6,6 -meth5lene bis(2-methyl-3,l-benzoxazine-4-one) and 3,3, 4,4 -benzophenone tetracarboxyUc dianhydride and 4,4 -oxydianiline exhibit good chemical etching properties (18). The polymers are soluble, but stable only up to 200—300°C. 

Our Electronic Chemicals group is an industry leader in most basic manufacturing of Wet Process Chemistries, from UHP Straights (100 ppt qualities). Custom formulated Wet Etch, Solvents and Solvent Blends, and Cleaning Products. 

PTFE IS insoluble in all known solvents and resists attack by most chemicals, although its surtace is readily degraded by alkah metal-anunonia solutions. Such solvated electron media etch PTFE to produce a brown-black layer quite unlike the onginal white, low-friction, nonstick surface... 

For a compound semiconductor to be useful as a substrate in studies of electrodeposition, it is desirable that clean, unreconstructed, stoichiometric surfaces be formed in solution prior to electrodeposition. For CdTe, the logical starting point is the standard wet chemical etch used in industry, a 1-5% Brj methanol solution. A CdTe(lll) crystal prepared in this way was transferred directly into the UHV-EC instrument (Fig. 39) and examined [391]. Figure 66B is an Auger spectrum of the CdTe surface after a 3-minute etch in a 1% Br2 methanol solution. Transitions for Cd and Te are clearly visible at 380 and 480 eV, respectively, as well as a small feature due to Br at 100 eV. No FEED pattern was visible, however. As described previously, a layer of solution is generally withdrawn with the crystal as it is dragged (emersed) from solution (the emersion layer). After all the solvent has evaporated, the surface is left with a coating composed of the... 

The nanostructures grown by SMPs were easily detached from the substrate by ultrasonic treatment, so the material can be dispersed into organic solvents and may be used for further preparation, chemical modification (etching), assembly and other nanochemical modifications. The SMPs seem to be promising candidates for the controlled growth of nanostructures, allowing us to circumvent the complexity associated with multi-parametric situations. 

It is necessary to prebake the PI film to 200°C to improve its resistance towards negative photoresist with a commercial stripper. After baking, remove the photoresist with a commercial stripper which is usually composed of phenol, strong mineral acids and solvents. 11) Neutralization and rinse. 12) final cure. Typical schedules are 30 min. at 350°C or 15 min. at 400°C. 10)PIasma,chemically etching) or physically (roughening) treat the polyimide surface to improve adhesion for next level metal. 

A distinction can be made between a positive and a negative resist, according to the action of light. In a positive working resist the monomer is deposited on the copper surface in the form of a viscous liquid. It is then irradiated through a mask (this is simply a drawing of the required pattern on a transparent sheet) and polymerization takes place only at the exposed places. The unirradiated liquid monomer is then washed away in a suitable solvent, and the exposed copper can be dissolved in an etching bath. Finally the protective polymer layer is removed by chemical or mechanical means, and the printed circuit is ready. 

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