Difference between revisions of "Manufacturing Technologies for Contact Parts"

From Electrical Contacts
Jump to: navigation, search
(Stamped Contact Parts)
 
(41 intermediate revisions by 5 users not shown)
Line 1: Line 1:
Besides the selection of the most suitable contact materials the design and type
+
Besides the selection of the most suitable contact materials, the design and type of attachment is critical for the reliability and electrical life of contact components for electromechanical switching devices. The most important factors here are the material-saving use of precious metals and the most economical manufacturing method for contact parts..
of attachment is critical for the reliability and electrical life of contact
 
components for electromechanical switching devices. The materials saving use
 
of high cost precious metals and the most economic manufacturing method for
 
contact parts are most important factors.
 
  
There are two basic manufacturing solutions available: One can start with single
+
There are two basic manufacturing solutions available: One can start with single contact parts, such as contact rivets or tips, which then are attached mechanically or by brazing or welding resp. to carrier parts. In the second case, a base material coated or clad with the precious contact metal - for special applications also clad with another non-precious material – in the form of strips or profiles is manufactured as a semi-finished pre-material from which the contact components are then stamped and formed. Besides mechanical cladding other processes such as electroplating and deposition from the gas phase are utilized.
contact parts such as contact rivets or tips which then are attached
+
Which of the following manufacturing processes is finally chosen, depends on the final application of the contact components in their respective switching devices or electromechanical components. Other considerations, such as the required number of electrical operations, the most economical use of precious metals and the anticipated volumes of parts are also important for the process selection.
mechanically or by brazing or welding resp. to carrier parts. In the second case
 
a base material coated or clad with the precious contact metal - for special
 
applications also clad with another non-precious material – in the form of strips
 
or profiles is manufactured as a semi-finished pre-material from which the
 
contact components are then stamped and formed. Besides mechanical
 
cladding other processes such as electroplating and deposition from the gas
 
phase are utilized.
 
Which of the following manufacturing processes is finally chosen depends on
 
the final application of the contact components in their respective switching
 
devices or electromechanical components. Other considerations such as the
 
required number of electrical operations, the most economical use of precious
 
metals and the anticipated volumes of parts are also important for the process
 
selection.
 
  
===3.1 Manufacturing of Single Contact Parts===
+
==Manufacturing of Single Contact Parts==
The group of single contacts includes contact rivets, contact tips, and formed
+
The group of single contacts includes contact rivets, contact tips and formed parts such as weld buttons. Contact spheres (or balls) are today rarely used because of economical considerations. <br>
parts such as weld buttons. Contact spheres (or balls) are today rarely used
+
Main Articel: [[Manufacturing of Single Contact Parts| Manufacturing of Single Contact Parts]]
because of economical considerations.
 
  
===3.1.1 Contact Rivets===
+
==Manufacturing of Semi-Finished Materials==
 +
Semi-finished contact pre-materials can be manufactured from solid precious metals, precious metal alloys or precious metal containing composite materials. <br>
 +
Main Articel: [[Manufacturing of Semi-Finished Materials | Manufacturing of Semi-Finished Materials]]
  
===3.1.1.1 Solid Contact Rivets===
+
==Attachment of Single Contact Parts==
 +
The following segments give an overview of the usually applied attachment technologies for contact parts to carrier components. They include mechanical, as well as brazing and welding methods used for electrical contact assemblies.
  
Solid contact rivets are the oldest utilized contact parts. Their manufacturing
+
Main Articel: [[Attachment of Single Contact Parts | Attachment of Single Contact Parts]]
requires a ductile contact material and is done without scrap on fully automated
 
special cold heading machines. A wire slug is cut off and the rivet head is
 
formed by pressing and hammering. This way contact rivets with various head
 
configurations such as flat, domed, spherical, or pointed can be manufactured
 
depending on the final application and switch or relay design.
 
  
*Typical Contact Shapes of Solid Contact Rivets
+
== Evaluation of Braze or Weld Joints==
Bild
+
The switching properties of brazed and welded contact assemblies is strongly dependent on the quality of the joint between the contact and the carrier. The required high quality is evaluated through optical methods, continuous control of relevant process parameters and by sampling of finished products.
*Contact Materials
 
Bild
 
*Dimensional Ranges
 
Bild
 
The respective parameters cannot be chosen independently of each other.
 
They mainly depend on the ductility of the required contact material. Before a
 
final decision on the dimensions we recommend to consult with the contact
 
manufacturer.
 
  
*Qualitätsmerkmale und Toleranzen
+
Main Articel: [[Evaluation of Braze or Weld Joints| Evaluation of Braze or Weld Joints]]
Bild
 
  
===3.1.1.2 Composite Contact Rivets===
+
==Stamped Contact Parts==
Clad rivets for which only a part of the head (composite or bimetal rivets) or also
+
Stamped electrical contact parts typically consist of a base carrier material to which a contact material is attached by various methods (<xr id="fig:Plated and contact containing pre-stamped strips and stamped parts"/><!--(Fig. 3.17)-->).
the shank end (tri-metal rivets) are composed of contact material – with the
+
They serve as the important functional components in many switching and electromechanical devices for a broad range of electrical and electronic
balance of the body mostly being copper – have replaced for many applications
+
applications. On the one hand, they perform the mostly loss-free electrical current transfer and the closing and opening of electrical circuits, while on the other hand, the contact carriers are important mechanical design components, selected to meet the requirements on electrical, thermal, mechanical and magnetic properties.
solid rivet versions because of economical considerations. The cost savings
 
depend on the contact material and its required volume for a specific
 
application. These composite rivets are also produced scrap-less from wire
 
material on special machinery with two process variations utilized.
 
  
During ''cold bonding'' and heading the bond between the contact material and
+
The increasing miniaturization of electromechanical components requires ever smaller stamped parts with low dimensional tolerances. Such precision
the copper is achieved without external heat energy by high plastic deformation
+
stamped parts are needed in the automotive technology for highly reliable switching and connector performance. In the information and data processing
at the face surfaces of the two wire segments ''(Fig. 3.1)''. The bonding pressure
+
technology, they transfer signals and control impulses with high reliability and serve as the interface between electronic and electrical components.
must be high enough to move the lattice components of the two metals within a
+
<figure id="fig:Plated and contact containing pre-stamped strips and stamped parts">
few atom radii so that the adhesion forces between atoms become effective.
+
[[File:Plated and contact containing pre-stamped strips and stamped parts.jpg|left|thumb|Figure 1: Plated and contact containing pre-stamped strips and stamped parts for different applications]]
Therefore the head to shank diameter ratio of 2:1 must be closely met for a
+
</figure>
strong bond between the two metals.
+
<br style="clear:both;"/>
 +
Main Articel: [[Stamped Contact Parts| Stamped Contact Parts]]
  
Fig. 3.1: Cold bonding of bimetall rivets (schematic)
+
==References==
  
During ''hot bonding'' the required heat energy is applied by a short term electrical
+
Vinaricky, E. (Hrsg.): Elektrische Kontakte, Werkstoffe und Anwendungen.
current pulse ''(Fig. 3.2)''. In the case of Ag and Cu a molten eutectic alloy of
+
Springer-Verlag, Heidelberg, Berlin 2002
silver and copper is formed in the constriction area between the two wire ends.
 
When using metal oxide containing contact materials the non-soluble oxide
 
particles tend to coagulate and the bonding strength between the component
 
materials is greatly reduced. Therefore the cold bonding technology is preferred
 
for these contact materials. The during cold bonding required high surface
 
deformation ratio can be reduced for the hot bonding process which allows the
 
head to shank diameter ratio to be reduced below 2:1.
 
  
For composite rivets with AgPd alloys as well as alloys on the basis of Au, Pd,
+
Witter, G., J.; Horn, G.: Contact Design and Attachment in: Electrical Contacts.
and Pt the above methods cannot be used because of the very different work
+
Hrg.: Slade, P., G., Marcel Dekker, Inc.,New York, Basel, 1999
hardening of these materials compared to the base material copper. The
 
starting material for such composite rivets is clad strip material from which the
 
contact rivets are formed in multiple steps of press-forming and stamping.
 
Similar processes are used for larger contact rivets with head diameters > 8 mm
 
and Ag-based contact materials.
 
  
Fig 3.2. Hot bonding of bimetal rivets (schematic)
+
Mürrle, U: Löten und Schweißen elektrischer Kontakte. In: Werkstoffe für
 +
elektrische Kontakte und ihre Anwendungen: Hrg.: Schröder K.-H. u. a.;
 +
Expert-Verlag, Band 366, (1997), 146 - 175
  
*Typical contact shapes for composite rivets
+
Eisentraut, H.: Verbundwerkstoffe aus der Walze. Kaltwalzplattieren von
bild
+
Mehrschichtverbundhalbzeugen, Metall 48 (1994) 95-99
  
*Contact materials
+
Weik, G.: Kontaktprofile ganzheitliche Lösungen für elektrische
bild
+
Kontaktsysteme, Metall 61 (2007) H. 6, 399 403
  
*Base materials
+
Jinduo, F; Guisheng, W.; Fushu, L.; Hongbing, Z.; Wenland, L.: Study on
bild
+
Reliability of AuAg10/AgNi10/CuNi30 Micro Contacts,
 +
th Proc. 24<sup>th</sup> Int. Conf.on Electr. Contacts, Saint Malo, France 2008, 206-209
  
*Dimensional ranges
+
Dorn, L.: Grundlagen der Löttechnik. in: Hartlöten Grundlagen und
bild
+
Anwendungen. Hrsg.: Dorn, L. u.a., Expert-Verlag, Band 146 (1985) 15-40
These parameters cannot be chosen independently of each other. They depend
 
mainly on the mechanical properties of the contact material. Before specifying
 
the final dimensions we recommend to consult with the contact manufacturer.
 
  
*Quality criteria and tolerances
+
Schreiner, H.: Güte der Lötung bzw. Schweißung von Kontaktstücken auf dem
bild
+
Trägermetall - Prüfung und Beurteilung nach dem Beschalten im Prüfschalter.
 +
Metall 30 (1976) 625 - 628
  
*Typical contact shapes of tri-metal rivets
+
DVS-Merkblatt 2813: Widerstandsschweißen von elektrischen Kontakten,
bild
+
Düsseldorf: DVS-Verlag 2009
  
*Contact materials
+
Schneider, F.: Stöckel, D.: Schweißen in der Kontakttechnik.
bild
+
Zts. für wirtschaftliche Fertigung 72, (1977) H. 4 u. 6
  
*Base materials
+
Haas, H.; Martin, W.; Tschirner, U.: Widerstandsschweißen in der
bild
+
Elektrotechnik, VDE-Fachbericht 42 (1991) 113-121
  
*Dimensional ranges
+
Weik, G.: Widerstandsschweißen von Kontaktprofilen mit
bild
+
Nachsetzwegmessung, VDE-Fachbericht 63 (2007) 165-174
  
*Standard values for rivet dimension
+
Bolmerg, E.: Aufschweißtechnik von Kontakten in Hinblick auf ihre Anwendung.
bild
+
VDE-Fachbericht 51 (1997) 103-109
  
===3.1.1.3 Braze Alloy Clad Contact Rivets===
+
[[de:Technologien_für_die_Herstellung_von_Kontaktteilen]]
For special cases, especially high surrounding temperatures with high thermal
 
and mechanical stresses during switching operations, a full metallurgical bond
 
between the contact rivet and the contact carrier may be required to prevent a
 
loosening of the connection and early failures of the device. To accomplish this
 
superior bond a thin layer of brazing alloy is added to the underside of the head
 
and the rivet shank. During assembly a thermal treatment is added after the
 
mechanical staking.
 
 
 
===3.1.1.4 Contact Rivets with Brazed Contact Material Layers===
 
For certain applications contact rivets with non-ductile or brittle materials such
 
as tungsten, silver–tungsten, or silver–graphite are required. Rivets with these
 
contact materials can only be fabricated by brazing. Small round tips are brazed
 
to pre-fabricated copper or steel bases using special brazing alloys in a
 
reducing atmosphere.
 
 
 
===3.1.2 Contact Tips===
 
Flat or formed contact tips, welded or brazed to contact carriers, are frequently
 
used in switching devices for higher power technology. Depending on the
 
contact material and specified shapes these tips are produced by various
 
manufacturing processes. The most frequently used ones are:
 
 
 
*Stamping from strips and profiles
 
*Cutting from extruded rods
 
*Pressing, Sintering, and Infiltrating
 
*Pressing, Sintering, and Re-Pressing
 
*Pressing and Sintering
 
 
 
For stamping sufficiently ductile semi-finished materials are needed. These are
 
mainly silver, silver–alloys, silver–nickel, silver–metal oxide, and silver–graphite
 
(with graphite particle orientation parallel to the switching surface). silver–metal
 
oxides and silver–graphite need an additional well brazable or weldable silver
 
layer on the underside which can be bonded to the bulk of the contact material
 
by various processes. To further facilitate the final attachment process strips and
 
profiles are often coated on the brazing underside with an additional thin layer of
 
brazing alloy such as L-Ag 15P (CP 102 or BCuP-5).
 
For Ag/C with the graphite orientation perpendicular to the switching surface the
 
brazable underside is produced by cutting tips from extruded rods and burning
 
out graphite in a defined thickness.
 
 
 
The press-sinter-infiltrate process (PSI) is used mainly for Ag/W and Cu/W
 
material tips with tungsten contents of > 50 wt%. A silver or copper surplus on
 
the underside of the tip later facilitates the brazing or welding during final
 
assembly.
 
 
 
The press–sinter–re-press method (PSR) allows the economic manufacturing of
 
shaped contact parts with silver or copper contents > 70 wt%. This process also
 
alloys parts pressed in two layers, with the upper being the contact material and
 
the bottom side consisting of pure Ag or Cu to support easy attachment.
 
 
 
Press–sinter processes are limited to smaller Ag/W contact tips with a Ag
 
content of approximately 65 wt%.
 
 
 
*Contact materials
 
bild
 
 
 
*Typical contact shapes of tips and formed contact parts
 
bild
 
 
 
*Dimensional ranges
 
bild
 
Because of the wide variety of shapes of contact tips and formed contact parts
 
the user and manufacturer usually develop special parts specific agreements
 
on quality and tolerances.
 
 
 
===3.1.3 Weld Buttons===
 
 
 
For contacts used at higher temperatures, such as for example in controls for
 
stove tops, the use of contact rivets or the direct welding of silver based contact
 
materials on steel or thermo-bimetal carriers is usually not feasible. For such
 
applications weld buttons are suitable contact components.
 
 
 
Weld buttons are round or rectangular tips manufactured from clad contact bimetal
 
or in some cases tri-metal semi-finished materials. The surface layer is
 
produced from the specified contact material, the bottom weldable layer from a
 
material with higher electrical resistivity such as steel, nickel, or for example a
 
copper-nickel alloy. For precious metal savings a third high conductive layer of
 
copper may be inserted between the contact material and weld backing. To
 
improve the welding process the underside often has an embossed pattern with
 
one or more weld projections.
 
 
 
The manufacturing of weld buttons from bi– or tri–metal strip requires a ductile
 
contact material. Weld buttons with tungsten contact layers are therefore
 
produced by brazing of tungsten discs to a weldable pre-formed base.
 
 
 
*Typical contact forms of weld buttons
 
bild
 
 
 
*Contact materials
 
bild
 
 
 
*Carrier materials
 
bild
 
 
 
*Dimensional Ranges
 
bild
 
 
 
Equipment for the Production of Wires, Rivets and Miniature - Profiles
 
bild
 
 
 
*Quality criteria of standard weld buttons
 
bilder
 
 
 
===3.2 Manufacturing of Semi-Finished Materials===
 
Semi-finished contact pre-materials can be manufactured from solid precious
 
metals, precious metal alloys, or precious metal containing composite materials.
 
They are made in wire, strip, and profile form by known processing technologies
 
such as extrusion and subsequent annealing and drawing or roll-forming. They
 
are supplied following the manufacturer's internal standards usually related to
 
DIN EN specifications for copper based materials. The most important materials
 
are two – or multiple material layered semi-finished materials with the contact
 
material bonded in its solid phase to non-precious carriers by cladding, brazing,
 
or welding. The contact material can also be deposited on the carrier from the
 
liquid or vapor phase.
 
 
 
===3.2.1 Clad Semi-Finished Pre-Materials (Contact-Bimetals)===
 
Clad materials consist of two or more layers of different materials, the contact
 
material and the carrier, which are firmly bonded to each other. Depending on
 
the electrical requirements the contact material is mainly an alloy of gold,
 
palladium, or silver based while the carrier material are mainly copper alloys. To
 
bond these materials various technologies are utilized, the two most important
 
ones being described in more detail below.
 
 
 
During ''hot cladding'', the classic process, the materials to be clad are
 
assembled into a cladding package in block or plate form, heated to about
 
800°C and clad (or “welded”) together under high pressure ''(Fig. 3.3)''. At the
 
interface between the two materials a non-separable bond is formed by either
 
diffusion of the reaction partners or in liquid phase by forming a AgCu eutectic
 
alloy when an additional brazing alloy foil is placed between the two materials.
 
Further processing is done by rolling with required annealing steps between
 
subsequent thickness reductions. The disadvantage of this process is the
 
usually limited short length of final material strips.
 
 
 
Fig. 3.3: Hot cladding of pre-materials (schematic)
 
 
 
In the ''Cold Roll-Cladding'' process the bond between the contact and carrier
 
material is achieved by cold deformation of > 50% in one rolling pass ''(Fig. 3.4)''.
 
The high plastic deformation causes cold welding in the boundary layer between
 
the two materials. To increase the quality and strength of the bond a subsequent
 
diffusion annealing is performed in most cases. This process is most suitable for
 
clad semi-finished strips with thin contact material layers (> 2 μm) and large strip
 
length (> 100 m).
 
 
 
Fig. 3.4: Cold roll-cladding of semi-finished strips (schematic)
 
 
 
*Typical configurations of clad contact strips
 
bild
 
 
 
*Contact materials
 
bild
 
 
 
*Carrier materials
 
bild?
 
 
 
*Dimensions
 
bild
 
When specifying the contact material layer thickness it is recommended to use the
 
minimum required thickness.
 
 
 
*Quality criteria and tolerances
 
Strength properties and dimensional tolerances of clad contact bi-metals are
 
derived from the standards DIN EN 1652 and DIN EN 1654 for Cu alloys. When
 
specifying the width of the contact material layer it is recommended to use the
 
minimum required value. All dimensions should be specified originating from one
 
strip edge.
 
 
 
===3.2.2 Brazed Semi-Finished Contact Materials (Toplay–Profiles)===
 

Latest revision as of 09:18, 12 January 2023

Besides the selection of the most suitable contact materials, the design and type of attachment is critical for the reliability and electrical life of contact components for electromechanical switching devices. The most important factors here are the material-saving use of precious metals and the most economical manufacturing method for contact parts..

There are two basic manufacturing solutions available: One can start with single contact parts, such as contact rivets or tips, which then are attached mechanically or by brazing or welding resp. to carrier parts. In the second case, a base material coated or clad with the precious contact metal - for special applications also clad with another non-precious material – in the form of strips or profiles is manufactured as a semi-finished pre-material from which the contact components are then stamped and formed. Besides mechanical cladding other processes such as electroplating and deposition from the gas phase are utilized. Which of the following manufacturing processes is finally chosen, depends on the final application of the contact components in their respective switching devices or electromechanical components. Other considerations, such as the required number of electrical operations, the most economical use of precious metals and the anticipated volumes of parts are also important for the process selection.

Manufacturing of Single Contact Parts

The group of single contacts includes contact rivets, contact tips and formed parts such as weld buttons. Contact spheres (or balls) are today rarely used because of economical considerations.
Main Articel: Manufacturing of Single Contact Parts

Manufacturing of Semi-Finished Materials

Semi-finished contact pre-materials can be manufactured from solid precious metals, precious metal alloys or precious metal containing composite materials.
Main Articel: Manufacturing of Semi-Finished Materials

Attachment of Single Contact Parts

The following segments give an overview of the usually applied attachment technologies for contact parts to carrier components. They include mechanical, as well as brazing and welding methods used for electrical contact assemblies.

Main Articel: Attachment of Single Contact Parts

Evaluation of Braze or Weld Joints

The switching properties of brazed and welded contact assemblies is strongly dependent on the quality of the joint between the contact and the carrier. The required high quality is evaluated through optical methods, continuous control of relevant process parameters and by sampling of finished products.

Main Articel: Evaluation of Braze or Weld Joints

Stamped Contact Parts

Stamped electrical contact parts typically consist of a base carrier material to which a contact material is attached by various methods (Figure 1). 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, while on the other hand, 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.

Figure 1: Plated and contact containing pre-stamped strips and stamped parts for different applications


Main Articel: Stamped Contact Parts

References

Vinaricky, E. (Hrsg.): Elektrische Kontakte, Werkstoffe und Anwendungen. Springer-Verlag, Heidelberg, Berlin 2002

Witter, G., J.; Horn, G.: Contact Design and Attachment in: Electrical Contacts. Hrg.: Slade, P., G., Marcel Dekker, Inc.,New York, Basel, 1999

Mürrle, U: Löten und Schweißen elektrischer Kontakte. In: Werkstoffe für elektrische Kontakte und ihre Anwendungen: Hrg.: Schröder K.-H. u. a.; Expert-Verlag, Band 366, (1997), 146 - 175

Eisentraut, H.: Verbundwerkstoffe aus der Walze. Kaltwalzplattieren von Mehrschichtverbundhalbzeugen, Metall 48 (1994) 95-99

Weik, G.: Kontaktprofile ganzheitliche Lösungen für elektrische Kontaktsysteme, Metall 61 (2007) H. 6, 399 403

Jinduo, F; Guisheng, W.; Fushu, L.; Hongbing, Z.; Wenland, L.: Study on Reliability of AuAg10/AgNi10/CuNi30 Micro Contacts, th Proc. 24th Int. Conf.on Electr. Contacts, Saint Malo, France 2008, 206-209

Dorn, L.: Grundlagen der Löttechnik. in: Hartlöten Grundlagen und Anwendungen. Hrsg.: Dorn, L. u.a., Expert-Verlag, Band 146 (1985) 15-40

Schreiner, H.: Güte der Lötung bzw. Schweißung von Kontaktstücken auf dem Trägermetall - Prüfung und Beurteilung nach dem Beschalten im Prüfschalter. Metall 30 (1976) 625 - 628

DVS-Merkblatt 2813: Widerstandsschweißen von elektrischen Kontakten, Düsseldorf: DVS-Verlag 2009

Schneider, F.: Stöckel, D.: Schweißen in der Kontakttechnik. Zts. für wirtschaftliche Fertigung 72, (1977) H. 4 u. 6

Haas, H.; Martin, W.; Tschirner, U.: Widerstandsschweißen in der Elektrotechnik, VDE-Fachbericht 42 (1991) 113-121

Weik, G.: Widerstandsschweißen von Kontaktprofilen mit Nachsetzwegmessung, VDE-Fachbericht 63 (2007) 165-174

Bolmerg, E.: Aufschweißtechnik von Kontakten in Hinblick auf ihre Anwendung. VDE-Fachbericht 51 (1997) 103-109