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Created page with "===3.5 Stamped Contact Parts=== Stamped electrical contact parts typically consist of a base carrier material to which a contact material is attached by various methods ''(Fig..."
===3.5 Stamped Contact Parts===
Stamped electrical contact parts typically consist of a base carrier material to
which a contact material is attached by various methods ''(Fig. 3.17)''. They serve
as the important functional components in many switching and
electromechanical devices for a broad range of electrical and electronic
applications. On the one hand they perform the mostly loss-free electrical
current transfer and the closing and opening of electrical circuits. In addition the
contact carriers are important mechanical design components selected to meet
the requirements on electrical, thermal, mechanical and magnetic properties.
The increasing miniaturization of electromechanical components requires ever
smaller stamped parts with low dimensional tolerances. Such precision
stamped parts are needed in the automotive technology for highly reliable
switching and connector performance. In the information and data processing
technology they transfer signals and control impulses with high reliability and
serve as the interface between electronic and electrical components.
Fig. 3.17:
Plated and contact
containing pre-stamped strips and
stamped parts for different
applications
===3.5.1 Types of Stamped Parts===
Stamped parts are produced as single pieces, in pre-stamped strip and comb
configurations. Depending on the requirements and application the contact and
base material as well as the coating and attachment technology is carefully
selected.
*Coated stamped parts
Stamped parts can be selectively or completely coated with precious metal
containing materials based on gold, palladium, and silver as well as
non-precious materials such as tin, nickel and copper ''(Fig. 3.17)''. For stamped
parts in high volumes like those used as electrical components in automobiles
the carrier material is mostly coated in a reel-to-reel process starting with either
solid or pre-stamped strips (see also chapter 7.1.1.3). Frequently the prestamped
strip will be used directly in further automated assembly of the finished
functional component. As an alternative finished stamped parts can be
electroplated using barrel and rack plating methods.
Very thin coating layers with tight tolerances are deposited by electroplating. For
many applications the high mechanical wear resistance is advantageous. Since
even very thin layers are mostly pore-free, these coatings also act as an
effective corrosion inhibitor. The type of coatings, the sequence of multiple
layers, and the coating thickness, for example for connectors, are chosen
according to the requirements for the end application.
*Clad stamped parts
For many applications thicker precious metal surfaces or AlSi layers are
necessary. These cannot be deposited by electroplating. Besides meltmetallurgically
produced materials on the basis of gold, palladium and silver,
also powder-metallurgical materials are required frequently. The metallurgical
bond between these contact materials and the mostly copper based substrates
is achieved through various mechanical cladding methods (see also chapter
3.2.1). In this way also aluminum clad strips are manufactured in which the
aluminum layer serves as the bondable surface in the interface between
electromechanical connections and electronic circuits. These clad semifinished
materials can be further fabricated into pre-stamped strips, in comb
form, or single stamped parts ''(Fig. 3.18)''.
Fig. 3.18:
Examples of clad stamped parts
*Welded stamped parts
Welded stamped parts can be fabricated by various methods (see also Chapter
3.3.3). Single contact pieces can be attached to pre-stamped or finished
stamped strips as weld buttons and wire or profile segments by electrical
resistance welding. Contact parts can also be stamped from seam-welded
semi-finished strip. Fitting the end application contact materials based on gold,
palladium and silver. Depending on the contact material and the design of the
finished contact component the contact bottom surface may be consist of a
weldable backing material.
*Brazed stamped parts
Brazed stamped contact assemblies are manufactured by two joining methods
(see also chapter 3.3.2). The contact material is either attached by resistance
or induction brazing to base metal carriers as prefabricated contact tip or they
are stamped from brazed semi-finished toplay strip. It is typical for brazed
contact parts that the contact material consists of silver based contact material
and a good conducting copper base material with larger cross-sectional area
for the usually higher current carrying capacity.
*Stamped contact parts with rivets
Riveted stamped contact parts are manufactured with the use of contact rivets
which are transferred over suitable feed mechanisms correctly oriented into
holes punched into the carrier ''(Fig. 3.19)''. Frequently also wire or wire segments
resp. are used which are subsequently coined and formed into the desired
contact shape (see also chapter 3.3.1). Both attachment methods have their
distinct advantages. Using composite or tri-metal rivets allows limiting the use
of precious metal custom tailored to the volume needed for specific switching
requirements. For wire staking the precious metal usage is usually higher but
the staking can be performed at significantly higher production rates
and the additional rivet making step is eliminated.
Fig. 3.19:
Examples of riveted stamped parts
*Pre-mounted component stamped parts
Components stamped parts consist of a minimum of two carrier parts which
differ in their material composition and geometrical form and the contact
material
''(Fig. 3.21)''. The assembly of these components as single pieces or stamping
progressions is performed in a stamping die by riveting or coining. To increase
the current carrying capacity at the joining area an additional welding step can
be added. Depending on the requirements the different properties of the two
carrier components can be combined. As an example: the high electrical
conductivity of a contact carrier blade is joined with the thermal or mechanical
spring properties of a second material to form a functional component. For this
process both carrier base materials can also be coated with additional
layers of other functional materials.
Fig. 3.20:
Examples of pre-mounted stamped
component parts
Stamped parts which are insert molded into or combined with plastic parts are
used in electromechanical components (see Chapter 10).
===3.5.2 Stamping Tools===
For the design of stamping tools the latest CAD software systems are used.
Modern stamping tools usually employ a modular design with integrated
dimensional and functional controls ''(Fig. 3.21)''. Depending on the requirements
on the parts and the volumes they are built with steel or carbide (-steel) inserts
which are coated with a wear resistant material such as for example TiN for
longer life.
A special stamping process is precision stamping for contact parts made from
thin strip materials with thicknesses in the range of 0.05 – 2.5 mm. With high
capacity stamping technology up to 1400 strokes/min can be reached for high
volume parts. During the actual stamping operation frequently other processes
such as thread-forming, welding of contact segments and insertion and forming
of contacts from wire segments are integrated. Depending on the production
volumes these operations can also be performed in multiples.
The quality of the tools used for stamping, like progressive dies and stamp-forming
tools is important for the final precision and consistency of the parts. During high
speed stamping the tools are exposed to extreme mechanical stresses which must
be compensated for to ensure the highest precision over long production runs. With
such high quality progressive dies parts of high precision with a cutting width of less
than the material thickness and with strict quality requirements for the cutting surfaces
can be manufactured.
To ensure the highest demands on the surface quality of precision contact parts quite
often vanishing oils are used as tool lubricants. Cleaning and degreasing operations
can also be integrated into the stamping process. Additionally most stamping lines
are also equipped with test stations for a 100% dimensional and surface quality
control.
During the design of stamping tools for electrical contacts minimizing of process
scrap and the possibility to separate the precious metal containing scrap must be
considered.
Fig. 3.21:
Progressive die for stamped contact parts
[[Category:Manufacturing Technologies for Contact Parts|Category]]
Stamped electrical contact parts typically consist of a base carrier material to
which a contact material is attached by various methods ''(Fig. 3.17)''. They serve
as the important functional components in many switching and
electromechanical devices for a broad range of electrical and electronic
applications. On the one hand they perform the mostly loss-free electrical
current transfer and the closing and opening of electrical circuits. In addition the
contact carriers are important mechanical design components selected to meet
the requirements on electrical, thermal, mechanical and magnetic properties.
The increasing miniaturization of electromechanical components requires ever
smaller stamped parts with low dimensional tolerances. Such precision
stamped parts are needed in the automotive technology for highly reliable
switching and connector performance. In the information and data processing
technology they transfer signals and control impulses with high reliability and
serve as the interface between electronic and electrical components.
Fig. 3.17:
Plated and contact
containing pre-stamped strips and
stamped parts for different
applications
===3.5.1 Types of Stamped Parts===
Stamped parts are produced as single pieces, in pre-stamped strip and comb
configurations. Depending on the requirements and application the contact and
base material as well as the coating and attachment technology is carefully
selected.
*Coated stamped parts
Stamped parts can be selectively or completely coated with precious metal
containing materials based on gold, palladium, and silver as well as
non-precious materials such as tin, nickel and copper ''(Fig. 3.17)''. For stamped
parts in high volumes like those used as electrical components in automobiles
the carrier material is mostly coated in a reel-to-reel process starting with either
solid or pre-stamped strips (see also chapter 7.1.1.3). Frequently the prestamped
strip will be used directly in further automated assembly of the finished
functional component. As an alternative finished stamped parts can be
electroplated using barrel and rack plating methods.
Very thin coating layers with tight tolerances are deposited by electroplating. For
many applications the high mechanical wear resistance is advantageous. Since
even very thin layers are mostly pore-free, these coatings also act as an
effective corrosion inhibitor. The type of coatings, the sequence of multiple
layers, and the coating thickness, for example for connectors, are chosen
according to the requirements for the end application.
*Clad stamped parts
For many applications thicker precious metal surfaces or AlSi layers are
necessary. These cannot be deposited by electroplating. Besides meltmetallurgically
produced materials on the basis of gold, palladium and silver,
also powder-metallurgical materials are required frequently. The metallurgical
bond between these contact materials and the mostly copper based substrates
is achieved through various mechanical cladding methods (see also chapter
3.2.1). In this way also aluminum clad strips are manufactured in which the
aluminum layer serves as the bondable surface in the interface between
electromechanical connections and electronic circuits. These clad semifinished
materials can be further fabricated into pre-stamped strips, in comb
form, or single stamped parts ''(Fig. 3.18)''.
Fig. 3.18:
Examples of clad stamped parts
*Welded stamped parts
Welded stamped parts can be fabricated by various methods (see also Chapter
3.3.3). Single contact pieces can be attached to pre-stamped or finished
stamped strips as weld buttons and wire or profile segments by electrical
resistance welding. Contact parts can also be stamped from seam-welded
semi-finished strip. Fitting the end application contact materials based on gold,
palladium and silver. Depending on the contact material and the design of the
finished contact component the contact bottom surface may be consist of a
weldable backing material.
*Brazed stamped parts
Brazed stamped contact assemblies are manufactured by two joining methods
(see also chapter 3.3.2). The contact material is either attached by resistance
or induction brazing to base metal carriers as prefabricated contact tip or they
are stamped from brazed semi-finished toplay strip. It is typical for brazed
contact parts that the contact material consists of silver based contact material
and a good conducting copper base material with larger cross-sectional area
for the usually higher current carrying capacity.
*Stamped contact parts with rivets
Riveted stamped contact parts are manufactured with the use of contact rivets
which are transferred over suitable feed mechanisms correctly oriented into
holes punched into the carrier ''(Fig. 3.19)''. Frequently also wire or wire segments
resp. are used which are subsequently coined and formed into the desired
contact shape (see also chapter 3.3.1). Both attachment methods have their
distinct advantages. Using composite or tri-metal rivets allows limiting the use
of precious metal custom tailored to the volume needed for specific switching
requirements. For wire staking the precious metal usage is usually higher but
the staking can be performed at significantly higher production rates
and the additional rivet making step is eliminated.
Fig. 3.19:
Examples of riveted stamped parts
*Pre-mounted component stamped parts
Components stamped parts consist of a minimum of two carrier parts which
differ in their material composition and geometrical form and the contact
material
''(Fig. 3.21)''. The assembly of these components as single pieces or stamping
progressions is performed in a stamping die by riveting or coining. To increase
the current carrying capacity at the joining area an additional welding step can
be added. Depending on the requirements the different properties of the two
carrier components can be combined. As an example: the high electrical
conductivity of a contact carrier blade is joined with the thermal or mechanical
spring properties of a second material to form a functional component. For this
process both carrier base materials can also be coated with additional
layers of other functional materials.
Fig. 3.20:
Examples of pre-mounted stamped
component parts
Stamped parts which are insert molded into or combined with plastic parts are
used in electromechanical components (see Chapter 10).
===3.5.2 Stamping Tools===
For the design of stamping tools the latest CAD software systems are used.
Modern stamping tools usually employ a modular design with integrated
dimensional and functional controls ''(Fig. 3.21)''. Depending on the requirements
on the parts and the volumes they are built with steel or carbide (-steel) inserts
which are coated with a wear resistant material such as for example TiN for
longer life.
A special stamping process is precision stamping for contact parts made from
thin strip materials with thicknesses in the range of 0.05 – 2.5 mm. With high
capacity stamping technology up to 1400 strokes/min can be reached for high
volume parts. During the actual stamping operation frequently other processes
such as thread-forming, welding of contact segments and insertion and forming
of contacts from wire segments are integrated. Depending on the production
volumes these operations can also be performed in multiples.
The quality of the tools used for stamping, like progressive dies and stamp-forming
tools is important for the final precision and consistency of the parts. During high
speed stamping the tools are exposed to extreme mechanical stresses which must
be compensated for to ensure the highest precision over long production runs. With
such high quality progressive dies parts of high precision with a cutting width of less
than the material thickness and with strict quality requirements for the cutting surfaces
can be manufactured.
To ensure the highest demands on the surface quality of precision contact parts quite
often vanishing oils are used as tool lubricants. Cleaning and degreasing operations
can also be integrated into the stamping process. Additionally most stamping lines
are also equipped with test stations for a 100% dimensional and surface quality
control.
During the design of stamping tools for electrical contacts minimizing of process
scrap and the possibility to separate the precious metal containing scrap must be
considered.
Fig. 3.21:
Progressive die for stamped contact parts
[[Category:Manufacturing Technologies for Contact Parts|Category]]
