Chromium layer thickness

The shrinkage of the material being processed is taken into account when dimensioning the components in the cavity areas. Hard chrome-plated molds, which consist of individual segments, are designed and manufactured so that the individual mold parts are compensated for their chromium layer thickness. A self-contained chromium layer has to remain for any adjustment work. Unplated areas should be avoided in any case to prevent a separation of the hard chromed plating from the mold steel. 

Electroplating. Chromium is electroplated onto various substrates in order to realize a more decorative and corrosion- or wear-resistant surface (24—32). About 80% of the chromium employed in metal treatment is used for chromium plating over 50% is for decorative chromium plating (see Metal surface treatments). Hard chromium plating differs from decorative plating mostiy in terms of thickness. Hard chromium plate may be 10 to several 100 p.m thick, whereas the chromium layers in a decorative plate may be as thin as 0.25 p.m, which corresponds to about two grams Cr per square meter of surface. 

If a sample of polycrystalline material is rotated during the sputtering process, the individual grains will be sputtered from multiple directions and nonuniform removal of material can be prevented. This technique has been successfully used in AES analysis to characterize several materials, including metal films. Figure 9 indicates the improvement in depth resolution obtained in an AES profile of five cycles of nickel and chromium layers on silicon. Each layer is about 50 nm thick, except for a thinner nickel layer at the surface, and the total structure thickness is about 0.5 pm. There can be a problem if the surface is rough and the analysis area is small (less than 0.1-pm diameter), as is typical for AES. In this case the area of interest can rotate on and off of a specific feature and the profile will be jagged. 

Decorative coatings of nickel plus chromium are cathodic to steel or zinc alloy substrates and with these protective systems deliberate use may be made of discontinuities in the chromium topcoat where corrosion of the underlying nickel will occur. If the number of these discontinuities in the chromium layer is greatly increased the current density at each individual corrosion site is reduced, penetration of corrosion through the thickness of the nickel layer is thus slowed down and the period of protection of the substrate metal is prolonged. 

Fig. 13.20. Optical heterodyne force microscopy (OHFM) and its application to a copper strip of width 500 nm, thickness 350 nm, on a silicon substrate, with subsequent chemical vapour deposition (CVD) of a silicon oxide layer followed by polishing and evaporation of a chromium layer of uniform thickness 100 nm and flatness better than 10 nm (a) amplitude (b) phase 2.5 [im x 2.5 m. Ultrasonic vibration at fi = 4.190 MHz was applied to the cantilever light of wavelength 830 nm was chopped at fo = 4.193 MHz and focused through the tip to a spot of diameter 2 im with incident mean power 0.5 mW the cantilever resonant frequency was 38 kHz. The non-linear tip-sample interaction generates vibrations of the cantilever at the difference frequency f2 — f = 3 kHz (Tomoda et al. 2003).

Fig. 6.9 shows an SEM image of a modulated Cu-Ni alloy with a thickness down to about 30 nm for each single layer. Laminated chromium layers being crack-free and with reduced internal stress are of great technical interest [6.112]. 

A photomask is a nearly optically flat glass (transparent to near UV) or quartz plate (transparent to deep UV) with a metal absorber pattern printed on one side. The metal pattern is typically a 0.1 /zm thick chromium layer. The metal absorber pattern on a photomask is opaque to ultraviolet radiation, whereas glass... 

Disposable microprizm and photodiode were placed on a rotary table (10 arc sec resolution). Before depositing metal layers, the glass surface of the microprizm was treated with a chromium mkture, rinsed in bi-distilled water and then dried in a dust-fiee airflow. Au layer (thickness 45 run) was deposited onto the quartz surface of microprizm in special vacuum sets equipped with oil pumps and nitrogen traps (pressure 10 Pa). Before deposition, the mikroprizm surface was ion-bombarded in a vacuum (pressure 1 Pa). In order to increase the chip stability in the aqueous environment, Au film was modified by covalent binding of the thiol contained 12-carbohydrate spacer. 

Bright surfaces can be obtained by polishing or by using bright nickel electrolytes. However, in industrial atmospheres, tarnishing will occur. Therefore, in many cases, a thin chromium layer is plated above the nickel coating with thickness between 0.25 and 1.5 xm (see Sect. 5.5.4.3). The presence of the... 

The system of a copper layer, a nickel layer (see Sect. 5.5.4.2), and an additional chromium coating (see Sect. 5.5.4.3) is one of the classical layer combinations for an effective corrosion protection. The nobility of each successive layer in the stack decreases. With possible variations in layer thickness, layer properties such as sulfur content (in the case of nickel layers), heat treatment, and so on, any protection can be obtained, either in a reductive (cities, industrial complexes), or in an oxidative atmosphere (land and sea atmosphere). 

The corrosion protection is increased if a crack-free chromium layer or a chromium layer with microcracks is added to the copper/nickel or to the nickel or double nickel layer. A crack-free chromixun film is possible if special additives are added to the chromium-plating electrolyte. Manganese salts, selenic acid, and indium sulfate are mentioned in the literature. The film also has to be sufficiently thick (>22 pm). The stabiKty of the film is not very high because crack formation is a permanent process in these films. 

Figure 12-6. Time dependence of the layer thickness dp of adsorbed mass per unit surface area f and of the polymer concentration cf in the adsorbed layer for the adsorption of poly(styrene) of < Mvv) = 176 000 g/mol from a solution of 5 mg/crn in cyclohexane onto a chromium surface. (From data of E. Killmann, J. Eisenlauer, and M. Korn.)...

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