Electromechanical Components

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Plastic molded or encapsulated components are of increasing importance due to rising requirements for smaller, lighter, and more compact designs with cost efficient pricing. Wherever mechanics and electronic meet, electromechanical components can be used in a multitude of applications, such as in automotive, communications, appliance, and consumer electronics engineering. In automotive applications such components are used in ever increasing volumes. In hybrid housings electronic components are integrated into components for increasingly more complex engine management functions. Strip-molded contact parts are for example used for seat adjustment, and airbag sensors; assembled contact parts are important functional components among others for memory mirror positioning units.

Electromechanical components usually consist of stamped circuit patterns (lead frames) which are coated in the contacting areas with functional surface layers. They serve as the electrical connections of the component to the outside wiring. The lead frames are over-molded with plastics or mounted into plastic molded parts. In addition electronic components can be added to increase the level of product integration. Utilizing the metal–plastic compound the mechanical stability of the plastic is combined with the conduction of electrical energy and electronic signals through the lead frame. In this way protective enclosures for electronic controls of machinery are created which at the same time serve as connecting points to the outside wiring. This can be achieved through hybrid frames and housings. Over-molding of contact components or assembly of different single parts in plastic enclosures can also be used to manufacture electromechanical components.

For achieving the highest possible functionality of the end product a close cooperation between the manufacturer and the end user in the early phases of development and design of new custom tailored electromechanical components is recommended. Innovative and cost-efficient designs can be realized through the combination of the know-how of the manufacturer in for example contact, coating, stamping, plastics processing, and assembly technologies and the mostly rather complex requirement profile given by the end user.

Besides the contact components the plastic materials are the critical building blocks for electromechanical components. Plastics used are mostly technical thermoplastics and heavy-duty plastics which fulfill the requirements for high mechanical strength, temperature stability, and fatigue strength Table 1. For the final selection of a plastic material economical considerations and the avoidance of environmentally hazardous ingredients such as for example flame retardants must be considered. The application of the most suitable contact material coating and the selection of carrier materials are covered in chapters Contact Carrier Materials, Surface Coating Technologies and Applications for Bonding Technologies.

Table 1: Frequently Used Plastic Materials and their Properties
Type of Plastics:
Sub-Type: Thermo-
plastics Abbrev.
mechanical electrical thermal resistant against
PPS 1.34 - 1.64 glass fibers,
graphite fibers
very high mechanical strength and
stiffness even at high temperatures,
low toughness, very low creep,
better properties with addition of
40% glass fibers
excellent isolation
properties, very low
dielectric losses
usable up to 240°C, short term
up to 270°C, low combustibility,
self-extinguishing, non-dripping
up to 220°C no known solvents,
conc. sodium hydroxide,
conc. hydrochloric and sulfuric
acid, good hydrolysis resistance
A amorph
1.12 - 1.14
1.13 - 1.14
1.06 - 1.08
1.01 - 1.02
1.06 - 1.12
glass fibers,
graphite fibers,
mineral powders,
glass beads, chalk,
lubricants such as
graphite, MoS2
depending on the PA type, crystalline
structure and water content; high
mechanical strength, stiffness, and
toughness; higher mech. strength
through stretching; very tough after
water absorption; high fatigue strength,
good impact toughness, abrasion
resistant, good sliding properties
through addition of graphite and MoS2;
increased mechanical strength with
glass and graphite fiber addition
depending on water
content, good surface
resistance reduces static
surface charge, high
dielectric losses, good
resistance against creep
upper use temperature 80 – 120°C
depending on type, short term
up to 140 – 200°C, mostly
boil resistant, can be sterilized,
narrow softening range
aliphatic and aromatic
hydrocarbons, gasoline, oils,
greases, some alcohols, esters,
ketenes, ether,
many chlorinated hydrocarbons,
weak alkaline solutions
PBT 1.29 glass fibers,
glass beads, minerals,
very high toughness at low
temperatures, good stiffness and
mechanical strength, good long term
stability, low abrasion at good sliding
good isolation properties,
good dielectric strength,
little effect of humidity
good thermal stability, use
temperature 60 – 110°C, short
term higher, with glass
reinforcement up to 200°C, low

tendency to turn yellow, very low
thermal expansion, burns with
sooty flame and drips

aliphatic and aromatic
hydrocarbons, fuels, oils, greases
LCP 1.40 - 1.92 glass fibers,
very high precision and dimensional
stability, high stiffness at low wall
thickness, low thermal expansion
coefficient; reinforced, better sliding
ability, electrically conductive and
suitable for electroplating types
dielectric losses depend
on surface coating, good
electrical conductivity;
depending on type
suitable for anti-static


use temperature 200 – 250°C,
good high temperature stability,
very low thermal expansion,
resistant to soldering
temperatures < 250°C, difficult to
combust and self-extinguishing
good resistance against widely
used organic solvents, i.e.
acetone, methanol, chlorine gas,
acetic acid
PPA 1.26 - 1.85 glass fibers,
high impact strength with good
mechanical strength and stiffness, very
high dimensional stability at high
temperatures, very low humidity
very low electrical losses use temperature up to 185°C,
standard types with UL94-HB
classification, special flame
protective types
very good resistance against
typically used organic solvents, i.e.
acetone, methanol, etc., water
based solutions (DI water, 10%
ammonium hydride, typical liquids
used in the automobile such as
brake fluid, motor oil, etc

Hybrid Frames and Housings

Hybrid frames and housings serve as the connecting points between mechanics and electronics Figure 1. They allow the transmission of signals or electrical energy. The connection to the current paths inside the housing is mostly done by bonding with aluminum wires. The over-molded lead frames are typically manufactured from aluminum clad strip materials which are well suited for bonding. The connectors integrated into the housing for transferring the current paths to the outside are coated with tin, silver, or gold, depending on specific requirements.

Component with hybrid housing for use in automobiles

Continuous Strip Over-Molding

In strip form over-molded contact parts reduce the complexity of assembly of the finished product. This complexity constantly increases with adding additional subcomponents Figure 2.

The strip over-molded contact parts can be tested for various quality parameters during manufacturing to continuously ensure the ever increasing reliability requirements of the end components.

Combining stamping and molding techniques in an automated production line allows the stamped contact parts to be molded into plastics as a complete functional unit. This also allows to reduce manufacturing tolerances to levels below those achievable with conventional assembly methods.

Examples of strip over molded contact components
Examples of assembled contact components

Assembled Contact Components

For applications and materials which do not allow strip over-molding, semi or fully automated assembly processes can be utilized. Different single parts like printed circuit boards, stamped parts, or contact components are assembled together with plastic molded parts on specialized equipment to complete functional components with low tolerances and high levels of functionality Figure 3. This also allows to integrate components which otherwise are difficult to mount onto circuit boards or carriers, such as capacitors, coils, or sensor elements into the functional component assembly. Contact parts used in these components are already tested on the assembly machine for quality parameters and functionality.