电镀对接触电阻的影响

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【文件名】:08310@52RD_电镀对接触电阻的影响.pdf
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will be different, and the degree of orientation or texture ca
ABSTRACT
be determined.
The variation of the surface oxidation rate of single-
crystal nickel with crystalline orientation is well
A variation in texture of plated metals with plating condi-
known and has been studied for some time. A corre-
tions is not new and has been known for some time. The
sponding variation of contact resistance after ambi-
variation in texture with current density and pH for a Watts
ent exposure of single-crystal specimens has been
2
A similar variation of texture
bath is shown in Figure 1a.
observed in our laboratory and has been duplicated
with additive concentration and current density is shown in
with electroplated nickel having a preferred grain ori-
3
Figure 1 b.
entation (texture). Data on the contact resistance
behavior of separable connectors with electroplate
A variation in contact resistance due to this variation in
orientation and plating conditions are discussed.
texture could be understood if the rate of oxidation also
depends on the crystalline orientation of the nickel surface.
Fortunately, a large amount of work has been done on the
INTRODUCTION
oxidation rates in single-crystal nickel, since clean surfaces
Environmental tests at AMP have shown that test coupons
are easy to obtain and nickel has only one stable oxide.
plated with nickel exhibit surprisingly different contact
resistance when exposed to the atmosphere for long periods
of time. A series of chemical analyses showed that this dif-
OXIDATION RATES ON NICKEL SURFACES
ference could not be due to the inclusion of metallic or other
Orders of magnitude variation in electrochemical reactions
impurities. Similarly, surface analyses showed that the dif-
with crystalline orientation have been observed by a numbe
ference could not be due to any variation in the surface aris-
4
This should not be too unexpected since
of investigators.
ing from oils or other contaminants.
the arrangement of atoms on the surfaces of a face-centered
cubic (fee) crystal like nickel is quite different for various
The only significant difference that could be observed
orientations. The arrangement of the atoms on { 100),
among the various nickel platings was a variation in plating
{110], and {111 ) surfaces are shown in Figure 2. The
texture. If a polycrystalline metallic film is examined by x-
{111] planes are referred to as close-packed planes since
ray diffraction, the peaks corresponding to diffraction from
the atoms are spaced as close together as possible. The
the single-crystal grains in the film with atomic planes par-
{ 100) atomic planes are seen to have quite a different atom
allel to the surface will have certain relative intensities. If
ic arrangement. These planes make up the six surfaces of a
the grains have a random orientation, the peak ratios will
1
fcc unit lattice cell. The { 110} atomic planes consist of row
If the orientation
correspond to those listed in the literature.
of closely spaced atoms arranged in a zigzag fashion.
of the grains is not random, then the peak intensity ratios

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