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Created page with "==== Electroplating Solutions – Electrolytes==== The actual metal deposition occurs in the electrolytic solution which contains the plating material as metal ions. Besides t..."
==== Electroplating Solutions – Electrolytes====
The actual metal deposition occurs in the electrolytic solution which contains
the plating material as metal ions. Besides this basic ingredient, the electrolytes
contain additional components depending on the processes used, such as for
example conduction salts, brighteners, and organic additives which are codeposited
into the coatings, influencing the final properties of the electroplating
deposit.
===== Precious Metal Electrolytes=====
All precious metals can be electroplated with silver and gold by far the most
widely used ones ''(Tables 7.1 and 7.2)''.
The following precious metal electrolytes are the most important ones:
==== Electroplating of Parts====
The complete or all-around electroplating of small mass produced parts like
contact springs, rivets, or pins is usually done as mass plating in electroplating
barrels of different shape. During the electroplating process the parts are
continuously moved and mixed to reach a uniform coating.
Larger parts are frequently electroplated on racks either totally or by different
masking techniques also partially. Penetrating the coating into the interior of
drilled holes or tubes can be achieved with the use of special fixtures.
'''Electroplated Parts'''
bild
*'''Materials'''
<table border="1" cellspacing="0" style="border-collapse:collapse"><tr><td><p class="s9">Coatings</p></td></tr><tr><td><p class="s9">Precious metals</p></td><td><p class="s9">Pure gold, hard gold (HV 150 – 250), palladium, palladium-nickel, rhodium,</p><p class="s9">pure silver, hard silver (HV 130 – 160)</p></td></tr><tr><td><p class="s9">Non-precious metals</p></td><td><p class="s9">Copper, nickel, tin, tin alloys</p></td></tr><tr><td><p class="s9">Carrier materials</p></td><td><p class="s9">Copper, copper alloys, nickel, nickel alloys, iron, steel,</p><p class="s9">aluminum, aluminum alloys, composite materials</p><p class="s9">such as aluminum – silicon carbide</p></td></tr></table>
*'''Coating thickness'''
Precious metals: 0.2 – 5 μm (typical layer thicknesses; for Ag also up to 25 μm)
Non-precious metals: Up to approx. 20 μm
Tolerances: Strongly varying depending on the geometrical shape of
parts (up to 50% at a defined measuring spot).
It is recommended to specify a minimum value for the
coating thickness at a defined measuring spot
als Bild?
*'''Quality criteria'''
Besides others the following layer parameters are typically monitored in-process and documented:
*Coating thickness *Solderability
*Adhesion strength *Bonding property
*Porosity Contact *resistance
These quality tests are performed according to industry standards, internal
standards, and customer specifications resp.
==== Electroplating of Semi-finished Materials====
The process for overall electroplating of strips, profiles, and wires is mostly
performed on continuously operating reel-to-reel equipment. The processing
steps for the individual operations such as pre-cleaning, electroplating, rinsing
are following the same principles as those employed in parts electroplating.
The overall coating is usually applied for silver plating and tin coating of strips
and wires. Compared to hard gold or palladium these deposits are rather
ductile, ensuring that during following stamping and forming operations no
cracks are generated in the electroplated layers.
==== Selective Electroplating====
Since precious metals are rather expensive it is necessary to perform the
electroplating most economically and coat only those areas that need the layers
for functional purposes. This leads from overall plating to selective
electroplating of strip material in continuous reel-to-reel processes. Depending
on the final parts design and the end application the processes can be applied
to solid strip material as well as pre-stamped and formed continuous strips or
utilizing wire-formed or machined pins which have been arranged as bandoliers
attached to conductive metal strips.
The core part of selective precious metal electroplating is the actual
electroplating cell. In it the anode is arranged closely to the cathodic polarized
material strip. Cathode screens or masks may be applied between the two to
focus the electrical field onto closely defined spots on the cathode strip.
Special high performance electrolytes are used in selective electroplating to
reach short plating times and allow a high flow rate of the electrolyte for a fast
electrolyte exchange in the actual coating area.
For a closely targeted electroplating of limited precious metal coating of contact
springs so-called brush-electroplating cells are employed ''(Fig. 7.1)''. The “brush”
or “tampon” consists of a roof shaped titanium metal part covered with a special
felt-like material. The metal body has holes in defined spots through which the
electrolyte reaches the felt. In the same spots is also the anode consisting of a
fine platinum net. The pre-stamped and in the contact area pre-formed contact
spring part is guided under a defined pressure over the electrolyte soaked felt
material and gets wetted with the electrolyte. This allows the metal
electroplating in highly selective spots.
Fig. 7.1:
Brush (or “Tampon”) plating cell;
1 Strip; 2 Anode; 3 Electrolyte feed;
4 Felt covered cell
For special applications, such as for example electronic component substrates,
a dot shaped precious metal coating is required. This is achieved with two belt
masks running synchronous to the carrier material. One of these two masks has
windows which are open to the spot areas targeted for precious metal plating
coverage.
'''Summary of the processes for selective electroplating'''
*'''Immersion electroplating'''
Overall or selective electroplating of both sides of solid strips or pre-stamped
parts in strip form
*'''Stripe electroplating'''
Stripe electroplating on solid strips through wheel cells or using masking
techniques
*'''Selective electroplating'''
One-sided selective coating of solid, pre-stamped, or metallically belt-linked
strips by brush plating
*'''Spot electroplating'''
Electroplating in spots of solid strips with guide holes or pre-stamped parts in
strip form
'''Typical examples of electroplated semi-finished materials'''
(overall or selectively)
bild
*'''Materials'''
<table border="1" cellspacing="0" style="border-collapse:collapse"><tr><td><p class="s8">Type of Coatings</p></td><td><p class="s8">Coating Thickness</p></td><td><p class="s8">Remarks</p></td></tr><tr><td><p class="s8">Precious Metals</p></td><td/><td/></tr><tr><td><p class="s8">Pure gold</p><p class="s8">Hard gold (AuCo 0.3)</p></td><td><p class="s8">0.1 - 3 µm</p></td><td><p class="s8">In special cases up to 10 µm</p></td></tr><tr><td><p class="s8">Palladium-nickel (PdNi20)</p></td><td><p class="s8">0.1 - 5 µm</p></td><td><p class="s8">Frequently with additional 0.2 µm AuCo 0.3</p></td></tr><tr><td><p class="s8">Silver</p></td><td><p class="s8">0.5 - 10 µm</p></td><td><p class="s8">In special cases up to 40 µm</p></td></tr><tr><td><p class="s8">Non-precious Metals</p></td><td/><td/></tr><tr><td><p class="s8">Nickel</p></td><td><p class="s8">0.5 - 4 µm</p></td><td><p class="s8">Diffusion barrier especially for gold layers</p></td></tr><tr><td><p class="s8">Copper</p></td><td><p class="s8">1 - 5 µm</p></td><td><p class="s8">Intermediate layer used in tinning of CuZn</p></td></tr><tr><td><p class="s8">Tin, tin alloys</p></td><td><p class="s8">0.8 - 25 µm</p></td><td><p class="s8">materials</p></td></tr></table>
*'''Carrier Materials'''
Copper, copper alloys, nickel, nickel alloys, stainless steel
*'''Dimensions and Tolerances'''
Bild
Dimensions
Carrier thickness d= 0.1 - 1 mm
Carrier width B= 6 - 130 mm
Distance b > 2 mm
Coating width a= 2 - 30mm
Coating thickness s = 0.2 - 5 μm
(typical range)
Distance from edge b > 0.5 mm
depending on the carrier thickness
and the plating process
*'''Tolerances'''
Coating thickness approx. 10 %
Coating thickness and position + 0,5 mm
*'''Quality Criteria'''
Mechanical properties and dimensional tolerances of the carrier materials follow
the typical standards, i.e. DIN EN 1652 and 1654 for copper and copper alloys.
Depending on the application the following parameters are tested and
recorded (see also: Electroplating of parts):
*Coating thickness *Solderability
*Adhesion strength *Bonding property
*Porosity *Contact resistance
These quality tests are performed according to industry standards, internal
standards, and customer specifications resp.
The actual metal deposition occurs in the electrolytic solution which contains
the plating material as metal ions. Besides this basic ingredient, the electrolytes
contain additional components depending on the processes used, such as for
example conduction salts, brighteners, and organic additives which are codeposited
into the coatings, influencing the final properties of the electroplating
deposit.
===== Precious Metal Electrolytes=====
All precious metals can be electroplated with silver and gold by far the most
widely used ones ''(Tables 7.1 and 7.2)''.
The following precious metal electrolytes are the most important ones:
==== Electroplating of Parts====
The complete or all-around electroplating of small mass produced parts like
contact springs, rivets, or pins is usually done as mass plating in electroplating
barrels of different shape. During the electroplating process the parts are
continuously moved and mixed to reach a uniform coating.
Larger parts are frequently electroplated on racks either totally or by different
masking techniques also partially. Penetrating the coating into the interior of
drilled holes or tubes can be achieved with the use of special fixtures.
'''Electroplated Parts'''
bild
*'''Materials'''
<table border="1" cellspacing="0" style="border-collapse:collapse"><tr><td><p class="s9">Coatings</p></td></tr><tr><td><p class="s9">Precious metals</p></td><td><p class="s9">Pure gold, hard gold (HV 150 – 250), palladium, palladium-nickel, rhodium,</p><p class="s9">pure silver, hard silver (HV 130 – 160)</p></td></tr><tr><td><p class="s9">Non-precious metals</p></td><td><p class="s9">Copper, nickel, tin, tin alloys</p></td></tr><tr><td><p class="s9">Carrier materials</p></td><td><p class="s9">Copper, copper alloys, nickel, nickel alloys, iron, steel,</p><p class="s9">aluminum, aluminum alloys, composite materials</p><p class="s9">such as aluminum – silicon carbide</p></td></tr></table>
*'''Coating thickness'''
Precious metals: 0.2 – 5 μm (typical layer thicknesses; for Ag also up to 25 μm)
Non-precious metals: Up to approx. 20 μm
Tolerances: Strongly varying depending on the geometrical shape of
parts (up to 50% at a defined measuring spot).
It is recommended to specify a minimum value for the
coating thickness at a defined measuring spot
als Bild?
*'''Quality criteria'''
Besides others the following layer parameters are typically monitored in-process and documented:
*Coating thickness *Solderability
*Adhesion strength *Bonding property
*Porosity Contact *resistance
These quality tests are performed according to industry standards, internal
standards, and customer specifications resp.
==== Electroplating of Semi-finished Materials====
The process for overall electroplating of strips, profiles, and wires is mostly
performed on continuously operating reel-to-reel equipment. The processing
steps for the individual operations such as pre-cleaning, electroplating, rinsing
are following the same principles as those employed in parts electroplating.
The overall coating is usually applied for silver plating and tin coating of strips
and wires. Compared to hard gold or palladium these deposits are rather
ductile, ensuring that during following stamping and forming operations no
cracks are generated in the electroplated layers.
==== Selective Electroplating====
Since precious metals are rather expensive it is necessary to perform the
electroplating most economically and coat only those areas that need the layers
for functional purposes. This leads from overall plating to selective
electroplating of strip material in continuous reel-to-reel processes. Depending
on the final parts design and the end application the processes can be applied
to solid strip material as well as pre-stamped and formed continuous strips or
utilizing wire-formed or machined pins which have been arranged as bandoliers
attached to conductive metal strips.
The core part of selective precious metal electroplating is the actual
electroplating cell. In it the anode is arranged closely to the cathodic polarized
material strip. Cathode screens or masks may be applied between the two to
focus the electrical field onto closely defined spots on the cathode strip.
Special high performance electrolytes are used in selective electroplating to
reach short plating times and allow a high flow rate of the electrolyte for a fast
electrolyte exchange in the actual coating area.
For a closely targeted electroplating of limited precious metal coating of contact
springs so-called brush-electroplating cells are employed ''(Fig. 7.1)''. The “brush”
or “tampon” consists of a roof shaped titanium metal part covered with a special
felt-like material. The metal body has holes in defined spots through which the
electrolyte reaches the felt. In the same spots is also the anode consisting of a
fine platinum net. The pre-stamped and in the contact area pre-formed contact
spring part is guided under a defined pressure over the electrolyte soaked felt
material and gets wetted with the electrolyte. This allows the metal
electroplating in highly selective spots.
Fig. 7.1:
Brush (or “Tampon”) plating cell;
1 Strip; 2 Anode; 3 Electrolyte feed;
4 Felt covered cell
For special applications, such as for example electronic component substrates,
a dot shaped precious metal coating is required. This is achieved with two belt
masks running synchronous to the carrier material. One of these two masks has
windows which are open to the spot areas targeted for precious metal plating
coverage.
'''Summary of the processes for selective electroplating'''
*'''Immersion electroplating'''
Overall or selective electroplating of both sides of solid strips or pre-stamped
parts in strip form
*'''Stripe electroplating'''
Stripe electroplating on solid strips through wheel cells or using masking
techniques
*'''Selective electroplating'''
One-sided selective coating of solid, pre-stamped, or metallically belt-linked
strips by brush plating
*'''Spot electroplating'''
Electroplating in spots of solid strips with guide holes or pre-stamped parts in
strip form
'''Typical examples of electroplated semi-finished materials'''
(overall or selectively)
bild
*'''Materials'''
<table border="1" cellspacing="0" style="border-collapse:collapse"><tr><td><p class="s8">Type of Coatings</p></td><td><p class="s8">Coating Thickness</p></td><td><p class="s8">Remarks</p></td></tr><tr><td><p class="s8">Precious Metals</p></td><td/><td/></tr><tr><td><p class="s8">Pure gold</p><p class="s8">Hard gold (AuCo 0.3)</p></td><td><p class="s8">0.1 - 3 µm</p></td><td><p class="s8">In special cases up to 10 µm</p></td></tr><tr><td><p class="s8">Palladium-nickel (PdNi20)</p></td><td><p class="s8">0.1 - 5 µm</p></td><td><p class="s8">Frequently with additional 0.2 µm AuCo 0.3</p></td></tr><tr><td><p class="s8">Silver</p></td><td><p class="s8">0.5 - 10 µm</p></td><td><p class="s8">In special cases up to 40 µm</p></td></tr><tr><td><p class="s8">Non-precious Metals</p></td><td/><td/></tr><tr><td><p class="s8">Nickel</p></td><td><p class="s8">0.5 - 4 µm</p></td><td><p class="s8">Diffusion barrier especially for gold layers</p></td></tr><tr><td><p class="s8">Copper</p></td><td><p class="s8">1 - 5 µm</p></td><td><p class="s8">Intermediate layer used in tinning of CuZn</p></td></tr><tr><td><p class="s8">Tin, tin alloys</p></td><td><p class="s8">0.8 - 25 µm</p></td><td><p class="s8">materials</p></td></tr></table>
*'''Carrier Materials'''
Copper, copper alloys, nickel, nickel alloys, stainless steel
*'''Dimensions and Tolerances'''
Bild
Dimensions
Carrier thickness d= 0.1 - 1 mm
Carrier width B= 6 - 130 mm
Distance b > 2 mm
Coating width a= 2 - 30mm
Coating thickness s = 0.2 - 5 μm
(typical range)
Distance from edge b > 0.5 mm
depending on the carrier thickness
and the plating process
*'''Tolerances'''
Coating thickness approx. 10 %
Coating thickness and position + 0,5 mm
*'''Quality Criteria'''
Mechanical properties and dimensional tolerances of the carrier materials follow
the typical standards, i.e. DIN EN 1652 and 1654 for copper and copper alloys.
Depending on the application the following parameters are tested and
recorded (see also: Electroplating of parts):
*Coating thickness *Solderability
*Adhesion strength *Bonding property
*Porosity *Contact resistance
These quality tests are performed according to industry standards, internal
standards, and customer specifications resp.
