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===7.1.2.5 Immersion Deposition of Tin===
A tin coating by ion exchange is usually not possible since copper is the more
precious metal. By adding thio-urea the electro-chemical potential of copper is
reduced to a level (approx. 450 mV, significantly lower than tin) that allows the
exchange reaction. Using a suitable electrolyte composition and enhancer
solutions like with the DODUSTAN process ''(Fig. 7.4)'' tin coatings can be
produced that, even under usually unfavorable conditions of copper
concentrations of 7 g/l in the electrolyte, are well solderable.
Fig. 7.4: Process flow for electroless tin deposition using the DODUSTAN process
The immersion tin deposition is suitable for the production of a well solderable
surface on printed circuit boards and electronic components. It is also used as
an etch resist against ammonia based solutions or as corrosion and oxidation
protection of copper surfaces.
===7.2 Coatings from the Gaseous Phase (Vacuum Deposition)===
The term PVD (physical vapor deposition) defines processes of metal, metal
alloys, and chemical compounds deposition in a vacuum by adding thermal and
kinetic energy through particle bombardment. The main processes are the
following four coating variations ''(Table 7.6)'':
*Vapor deposition *Sputtering (Cathode atomization)
*Arc vaporizing *Ion implantation
In all four processes the coating material is transported in its atomic form to the
substrate and deposited on it as a thin layer (a few nm to approx. 10 μm)
Table 7.6: Characteristics of the Most Important PVD Processes
tabelle fehlt!
The sputtering process has gained the economically most significant usage. Its
process principle is illustrated in ''(Fig. 7.5)''.
Fig. 7.5: Principle of sputtering Ar = Argon atoms; e = Electrons; M = Metal atoms
Initially a gas discharge is ignited in a low pressure (10 – 1 Pa) argon
atmosphere. The argon ions generated are accelerated in an electric field and
impact the target of material to be deposited with high energy. Caused by this
energy atoms are released from the target material which condensate on the
oppositely arranged anode (the substrate) and form a layer with high adhesion
strength. Through an overlapping magnetic field at the target location the
deposition rate can be increased, making the process more economical.
The advantages of the PVD processes and especially sputtering for electrical
contact applications are:
*High purity of the deposit layers *Low thermal impact on the
*Almost unlimited coating materials substrate
*Low coating thickness tolerance *Excellent adhesion (also by using additional intermediate layers)
Coatings produced by PVD processes are used for contact applications, for
example on miniature-profiles, in electrical engineering and for electronic
components, for solderability in joining processes, for metalizing of nonconductive
materials, as well as in semiconductors, opto-electronics, optics,
and medical technology applications.
There are few limitations regarding the geometrical shape of substrate parts.
Only the interior coating of drilled holes and small diameter tubing can be more
problematic (ratio of depth to diameter should be < 2:1). Profile wires, strips,
and foils can be coated from one side or both; formed parts can be coated
selectively by using masking fixtures that at the same time serve as holding
fixtures.
*'''Examples of vacuum coated semi-finished materials and parts'''
bild
*'''Materials'''
Selection of possible combinations of coating and substrate materials
<table border="1" cellspacing="0" style="border-collapse:collapse"><tr><td><p class="s8">Substrate Materials</p></td><td><p class="s8">Coating Materials</p></td></tr><tr><td><p class="s8">Substrate Materials</p></td><td><p><span><IMG width="13" height="12" src="KAPITEL 7 englisch/Image_035.png"/></span></p></td><td><p><span><IMG width="13" height="10" src="KAPITEL 7 englisch/Image_036.png"/></span></p></td><td><p><span><IMG width="10" height="10" src="KAPITEL 7 englisch/Image_037.png"/></span></p></td><td><p><span><IMG width="13" height="10" src="KAPITEL 7 englisch/Image_038.png"/></span></p></td><td><p><span><IMG width="14" height="10" src="KAPITEL 7 englisch/Image_039.png"/></span></p></td><td><p><span><IMG width="9" height="10" src="KAPITEL 7 englisch/Image_040.png"/></span></p></td><td><p><span><IMG width="8" height="10" src="KAPITEL 7 englisch/Image_041.png"/></span></p></td><td><p><span><IMG width="12" height="10" src="KAPITEL 7 englisch/Image_042.png"/></span></p></td><td><p><span><IMG width="15" height="10" src="KAPITEL 7 englisch/Image_043.png"/></span></p></td><td><p><span><IMG width="11" height="10" src="KAPITEL 7 englisch/Image_044.png"/></span></p></td><td><p><span><IMG width="9" height="10" src="KAPITEL 7 englisch/Image_045.png"/></span></p></td><td><p><span><IMG width="9" height="10" src="KAPITEL 7 englisch/Image_046.png"/></span></p></td></tr><tr><td><p class="s8">Precious metal / alloys</p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_047.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_048.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_049.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_050.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_051.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_052.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_053.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_054.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_055.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_056.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_057.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_058.png"/></span></p></td></tr><tr><td><p class="s8">NF metals / alloys</p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_059.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_060.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_061.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_062.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_063.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_064.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_065.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_066.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_067.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_068.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_069.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_070.png"/></span></p></td></tr><tr><td><p class="s8">Fe alloys / stainless steel</p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_071.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_072.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_073.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_074.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_075.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_076.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_077.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_078.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_079.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_080.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_081.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_082.png"/></span></p></td></tr><tr><td><p class="s8">Special metals (Ti, Mo, W)</p></td><td><p><span><IMG width="9" height="10" src="KAPITEL 7 englisch/Image_083.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_084.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_085.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_086.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_087.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_088.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_089.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_090.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_091.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_092.png"/></span></p></td><td><p><span><IMG width="9" height="10" src="KAPITEL 7 englisch/Image_093.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_094.png"/></span></p></td></tr><tr><td><p class="s8">Carbide steels (WC-Co)</p></td><td><p><span><IMG width="9" height="10" src="KAPITEL 7 englisch/Image_095.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_096.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_097.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_098.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_099.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_100.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_101.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_102.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_103.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_104.png"/></span></p></td><td><p><span><IMG width="9" height="10" src="KAPITEL 7 englisch/Image_105.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_106.png"/></span></p></td></tr><tr><td><p class="s8">Ceramics (Al<span class="s16">2</span>O<span class="s16">3</span>, AlN)</p></td><td><p><span><IMG width="9" height="10" src="KAPITEL 7 englisch/Image_107.png"/></span></p></td><td><p><span><IMG width="9" height="10" src="KAPITEL 7 englisch/Image_108.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_109.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_110.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_111.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_112.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_113.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_114.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_115.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_116.png"/></span></p></td><td><p><span><IMG width="9" height="10" src="KAPITEL 7 englisch/Image_117.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_118.png"/></span></p></td></tr><tr><td><p class="s8">Glasses (SiO<span class="s16">2</span>, CaF)</p></td><td><p><span><IMG width="9" height="10" src="KAPITEL 7 englisch/Image_119.png"/></span></p></td><td><p><span><IMG width="9" height="10" src="KAPITEL 7 englisch/Image_120.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_121.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_122.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_123.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_124.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_125.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_126.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_127.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_128.png"/></span></p></td><td><p><span><IMG width="9" height="10" src="KAPITEL 7 englisch/Image_129.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_130.png"/></span></p></td></tr><tr><td><p class="s8">Plastics (PA, PPS)</p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_131.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_132.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_133.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_134.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_135.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_136.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_137.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_138.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_139.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_140.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_141.png"/></span></p></td><td><p><span><IMG width="8" height="8" src="KAPITEL 7 englisch/Image_142.png"/></span></p></td></tr></table>
*'''Dimensions'''