Copper surface preparation

Time to delamination, or T260 time, which is the time it takes for a sample to delaminate when held at an isotherm temperature of 260°C, is not a fundamental base material property, but is a functional test related to the other material properties. In multilayer PCBs, this property can be affected by the quahty of the innerlayer copper surface preparation and multilayer lamination quality, among other things. 

Sulfuric-peroxide systems are used extensively for copper surface preparation by microetch-ing the surface to provide texture and active surfaces. These formulations have been used in... 

The painting procedure for other metal surfaces, although similar, the process of pre-treatment for cast iron components or non-ferrous metals, such as aluminium and copper, may need more care. The process of pre-treatment in such cases may vary slightly than for MS, as noted below. Such surfaces may require a change in the type of chemicals, their concentration and duration of treatment. The final surface preparation and painting procedure, however, will remain the same for all. 

The introduction of enamel into the wastestream results in an increase in the concentration of metals, but these metals (antimony, titanium, zirconium, tin, cobalt, and manganese) are in solid form whereas the metals generated by surface preparation are normally in dissolved form. These solid metals increase the suspended solids concentration of the stream. Other metals that may be found in the enamel preparation and application wastestream in significant amounts include aluminum, copper, iron, lead, nickel, and zinc. Table 8.2 presents pollutant sampling data for the processes used in the porcelain enameling on steel industry. 

Wastewater from this subcategory is generated as in the previous subcategories, by surface preparation, enamel application, ball milling, and related operations. Wastewater constituents generally consist of copper and the components used to form the enamel. 

The role of thermal fluctuations in bubble nucleation of pool boiling was shown experimentally by Dougall and Lippert (1967) see Figure 2.4. Their experiments were conducted using water, at atmospheric pressure, boiled from a 2-in. (5 cm)-diameter copper surface that was located in the bottom plate of a 2-gal (7.6-liter) aluminum container. The copper boiling surface was prepared by pol-... 

In order to confirm the plating uniformity a copper panel electrode was prepared by etching depressions on the copper surface. These depressions are... 

The most popular method involves deposition initially of a layer of electroless copper up to 2 /an thick. The excellent conductivity of the copper ensures that this gives good results for attenuation (that is, for shielding). The copper layer is followed by electroless nickel up to 1 /an thick, which protects against abrasion and corrosion. Obviously it is important that the nickel not be porous and with this in view an activation stage may be interposed, with chemical deposition of palladium on the surface of the copper in preparation for the nickel. 

Brass is an alloy of copper and zinc, and bronze is an alloy of copper and tin. Sandblasting or other mechanical means of surface preparation may be used for both of these copper alloys. Surface treatment combining mechanical and chemical treatment with a solution of zinc oxide, sulfuric acid, and nitric acid is recommended for maximum adhesion properties. Adhesives similar to those recommended for copper may be used on brass and bronze substrates. 

The normal Ullmann reaction is the formation of an Ar-Ar bond by a thermally activated coupling of a thienyl halide in the presence of Cu, Ni, Pd, or their compounds, but this method is not suitable for the preparation of oligothio-phene and polythiophene films of nanoscale thickness. A photoactivated Ullmann coupling has now been described for the in situ synthesis of such polythiophene films <2006CC729>. The concept involves the selective photodissociation of the C-I bond in 2,5-diiodothiophene on a copper surface the resultant thienyl radicals react with the copper to produce thienyl-Cu intermediates in a thin monomer film at room temperature. These intermediates react with the monomer and produce polythiophene. 

Tadepalli and Thompson focused on the bonding strength of copper-to-copper bonded structures using four-point bending characterization [66]. Adhesion energy was characterized for three different surface preparation... 

The influence of the preparation method of methanol catalysts composed of copper associated with rare earth oxides (eg Cu-La2Zr207 and ZnO promoted Cu-La2Zr20y systems) on the catalytic behaviour is discussed. Good activities and improved aging properties are always associated with a high copper surface area and a reasonnable crystallinity of the La2Zr207 pyrochlore. 

The characteristics of the catalytic systems depend not only on the preparation technique but also on the annealing temperature. Both catalysts have a poor thermal stability and a calcination above 350°C led to very low BET and copper surface areas e.g. 3m2/g (Cu-Zn [ex carbonate]) and lm2/g (Cu-Zn [ex oxalate]) at 550°C. Since the copper surface area determines for the catalytic activity only the samples calcined at T = 350°C have been used for the catalytic tests. 

The catalytic activity of the catalysts in presence of a CO2 + H2 mixture between 250°C and 320°C (figure 1) can be more or less related to the copper surface areas as observed in table 1. Thus the catalysts prepared using carbonate precipitation are the most active in methanol formation. This can be attributed to the higher selectivity easily related with the high copper coverage of the catalyst. 

Considering the catalysts annealed at 710°C it can be observed that the system originating from the carbonates has a lower activity that the sample calcined at 550°C, whereas on the Cu-LaZr [ex oxalate] system the methanol yield is increased if the annealing temperature goes from 550 to 710°C. All these results can more or less be explained by the change of the copper surface area with the preparation and the annealing temperature as described in table 2. Finally each preparation technique needs the use of the best selected annealing temperature labelled in table 2. 

It can also be observed that despite the same copper surface areas of 12 m2/g the Cu-LaZr ([ex carbonate] 550) system has a noticiable different catalytic behavior that Cu-LaZr ([ex oxalate] 710). This proves that, appart the copper surface areas, variation of morphology, presence of impurities as well as other factors related with the preparation can be responsible for difference of catalytic properties related to the preparation technique. 

For copper-zinc catalysts if the same preparation technique [carbonates] or [oxalates] is used a nearly linear correlation can be established between the copper surface area, the amount of formates and the methanol yield. But if the preparation technique is changed the formates and methanol formation, related to a unit of copper surface area, is not maintained and the observed correlation is restricted to catalysts prepared by the same technique as shown in figure 7. 

---