UNIT-5
MODERN ENGINEERING MATERIALS FOR ELECTRONIC DEVICES
Introduction:
An alloy is a homogeneous substance formed by mixing two or more elements, at
least one of them being a metal. Most pure metals are either too soft, brittle or chemically
reactive for practical use. Combining different ratios of metals as alloys modifies the
properties of pure metals to produce desirable characteristics. The alloys made of aluminium,
titanium, copper, and magnesium are also important metals. The magnetic alloy
semiconductors containing lower concentrations of magnetic ions are known as dilute
magnetic semiconductors. These alloys have recently attracted much attention because of
their potential applications.
Definition: An alloy is a homogeneous substance formed by mixing two or more elements, at
least one of them being a metal.
Alloys are of three types:
1) Alloys formed by two or more metals.
Eg: brass (Cu-Zn)
2) Alloys formed between a metal and a non-metal
3) Alloys (Amalgam) formed between mercury and another metal
Eg: Zinc amalgam.
5.1.1 Need for Alloys
1. To improve hardness
Hardness of a metal is considerably increased on alloying it. Conversion of soft gold
into hard gold by alloying it with copper is an example. The tensile strength of iron is
increased ten times by alloying with 1% carbon.
2. To lower the melting point
It is lower for an alloy compared to the melting points of its constituents. e.g.; Melting
point of solder (1830C) is less than those of its constituents; Pb (3270C) and Sn (2320C).
Alloying makes the metallic system easily fusible and so alloys can be moulded at lower
temperatures compared to moulding temperatures of pure metal.
3. To improve casting property
Some metals expand on solidification. This arises due to requirement of formation of
certain lattice arrangements of the metallic atoms as the metal solidifies. This property helps
proper casting of metals into objects. Some solid metals are soft and brittle making their
5.1
, castings weak. This deficient character is eliminated by alloying the metal. Molten alloys on
solidification produce hard, durable castings. The alloy (pb + Sn + Sb) has excellent casting
property when compared to its constituents.
4. To modify the electrical conductivity
Alloys are less conductive than pure metals. The interaction of two metals in an alloy
modifies the electronic conduction bands in them to render the alloy less conductive. eg: even
traces of metallic impurities in copper reduces its electrical conductivity.
5. To modify the color
Alloying modifies the colors of metals eg: red copper and silver – white zinc, on
alloying, produces yellowish brown brass alloy.
6. To modify chemical properties
Chemical properties are either enhanced or depressed.eg: rate of dissolution of an
alloy in hydrochloric acid is different (usuallyless) from the rates of dissolutions of the
constituent metals. An alloy is less easily attacked by chlorine compounds than its constituent
metals.
7. To resist the corrosion of the metal
The most important and useful property of alloying is its ability to resist corrosion in
its alloying. Generally, alloys are more resistant to corrosion than pure metals. e.g.: stainless
steel (alloy of Fe,C, Ni and Cr) which is not corroded by the atmospheric conditions though
pure Fe easily corrodes (rusted) in moist air.
Of these property- modifications, enhanced fusion capability and resistant to
corrosion are two qualities that make alloys very useful material industrially.
Modern electronic grade alloys:
Electronic grade alloys and electrical alloys have excellent mechanical properties,
generally have high thermal and electrical conductivity, and are highly resistant to corrosion.
These alloys are often used for electronic applications in anodes, lead wires, fuel cells,
battery casings, packaging and lids.
5.2.1 Nickel alloys:
S.No Alloy Name Composition Properties Uses
1 Nickel 200 Ni-99.0% It is a It’s used in caustic
min, C-.15% max, commercially pure solutions, food
Mn-.35% max, S- nickel that exhibits handling equipment,
010% max, Si- .35% good corrosion and general corrosion-
max, Cu-.25% max, resistance and has resistant parts and
5.2
, Fe-.40% rather low electrical structures. Because it
resistivity. contains magnetic and
mechanical properties,
it can be used in
devices that require
magnetic actuated parts
2 Nickel 201 Ni- 99.0% It is similar to Desirable in
min, C- 02% max, Nickel 200 but low deep drawing, spinning,
Mn-.35%, S-.010% carbon content. It has and coining. It addition,
max, Si-.35% max, a low annealed it can be applied to
Cu- .25% max, Fe- hardness and very corrosion-resistant
40% low work-hardening equipment including
rate. but not limited to:
caustic evaporators,
spun anodes, and
laboratory crucibles.
3 Nickel 205 Ni: >99%, Mn: <.35, It exhibits good It is frequently used in
Fe: <.20, Si: <0.15, oxidation resistance. lead wires, pins,
Cu: 0.15, C: <0.15, terminals, vacuum tube
Mg: 0.010-0.080, Ti : components, support
0.010-0.050, S: wires, and comparable
<0.0080. electrical parts.
4 Nickel 270 Ni- 99.95% and Low hardness,high It is commonly used for
traces of Fe, C, Cu purity,high ductility electrical resistant
thermometers.
5 Nichrome Ni-60%, Fe-26%,Cr- High thermal and 1. They are used in
12%, Mn-25%
chemical resistance making furnace heating
coils,
2. They are used in
heating elements in
electric irons, toasters
and kettles,
5.3
MODERN ENGINEERING MATERIALS FOR ELECTRONIC DEVICES
Introduction:
An alloy is a homogeneous substance formed by mixing two or more elements, at
least one of them being a metal. Most pure metals are either too soft, brittle or chemically
reactive for practical use. Combining different ratios of metals as alloys modifies the
properties of pure metals to produce desirable characteristics. The alloys made of aluminium,
titanium, copper, and magnesium are also important metals. The magnetic alloy
semiconductors containing lower concentrations of magnetic ions are known as dilute
magnetic semiconductors. These alloys have recently attracted much attention because of
their potential applications.
Definition: An alloy is a homogeneous substance formed by mixing two or more elements, at
least one of them being a metal.
Alloys are of three types:
1) Alloys formed by two or more metals.
Eg: brass (Cu-Zn)
2) Alloys formed between a metal and a non-metal
3) Alloys (Amalgam) formed between mercury and another metal
Eg: Zinc amalgam.
5.1.1 Need for Alloys
1. To improve hardness
Hardness of a metal is considerably increased on alloying it. Conversion of soft gold
into hard gold by alloying it with copper is an example. The tensile strength of iron is
increased ten times by alloying with 1% carbon.
2. To lower the melting point
It is lower for an alloy compared to the melting points of its constituents. e.g.; Melting
point of solder (1830C) is less than those of its constituents; Pb (3270C) and Sn (2320C).
Alloying makes the metallic system easily fusible and so alloys can be moulded at lower
temperatures compared to moulding temperatures of pure metal.
3. To improve casting property
Some metals expand on solidification. This arises due to requirement of formation of
certain lattice arrangements of the metallic atoms as the metal solidifies. This property helps
proper casting of metals into objects. Some solid metals are soft and brittle making their
5.1
, castings weak. This deficient character is eliminated by alloying the metal. Molten alloys on
solidification produce hard, durable castings. The alloy (pb + Sn + Sb) has excellent casting
property when compared to its constituents.
4. To modify the electrical conductivity
Alloys are less conductive than pure metals. The interaction of two metals in an alloy
modifies the electronic conduction bands in them to render the alloy less conductive. eg: even
traces of metallic impurities in copper reduces its electrical conductivity.
5. To modify the color
Alloying modifies the colors of metals eg: red copper and silver – white zinc, on
alloying, produces yellowish brown brass alloy.
6. To modify chemical properties
Chemical properties are either enhanced or depressed.eg: rate of dissolution of an
alloy in hydrochloric acid is different (usuallyless) from the rates of dissolutions of the
constituent metals. An alloy is less easily attacked by chlorine compounds than its constituent
metals.
7. To resist the corrosion of the metal
The most important and useful property of alloying is its ability to resist corrosion in
its alloying. Generally, alloys are more resistant to corrosion than pure metals. e.g.: stainless
steel (alloy of Fe,C, Ni and Cr) which is not corroded by the atmospheric conditions though
pure Fe easily corrodes (rusted) in moist air.
Of these property- modifications, enhanced fusion capability and resistant to
corrosion are two qualities that make alloys very useful material industrially.
Modern electronic grade alloys:
Electronic grade alloys and electrical alloys have excellent mechanical properties,
generally have high thermal and electrical conductivity, and are highly resistant to corrosion.
These alloys are often used for electronic applications in anodes, lead wires, fuel cells,
battery casings, packaging and lids.
5.2.1 Nickel alloys:
S.No Alloy Name Composition Properties Uses
1 Nickel 200 Ni-99.0% It is a It’s used in caustic
min, C-.15% max, commercially pure solutions, food
Mn-.35% max, S- nickel that exhibits handling equipment,
010% max, Si- .35% good corrosion and general corrosion-
max, Cu-.25% max, resistance and has resistant parts and
5.2
, Fe-.40% rather low electrical structures. Because it
resistivity. contains magnetic and
mechanical properties,
it can be used in
devices that require
magnetic actuated parts
2 Nickel 201 Ni- 99.0% It is similar to Desirable in
min, C- 02% max, Nickel 200 but low deep drawing, spinning,
Mn-.35%, S-.010% carbon content. It has and coining. It addition,
max, Si-.35% max, a low annealed it can be applied to
Cu- .25% max, Fe- hardness and very corrosion-resistant
40% low work-hardening equipment including
rate. but not limited to:
caustic evaporators,
spun anodes, and
laboratory crucibles.
3 Nickel 205 Ni: >99%, Mn: <.35, It exhibits good It is frequently used in
Fe: <.20, Si: <0.15, oxidation resistance. lead wires, pins,
Cu: 0.15, C: <0.15, terminals, vacuum tube
Mg: 0.010-0.080, Ti : components, support
0.010-0.050, S: wires, and comparable
<0.0080. electrical parts.
4 Nickel 270 Ni- 99.95% and Low hardness,high It is commonly used for
traces of Fe, C, Cu purity,high ductility electrical resistant
thermometers.
5 Nichrome Ni-60%, Fe-26%,Cr- High thermal and 1. They are used in
12%, Mn-25%
chemical resistance making furnace heating
coils,
2. They are used in
heating elements in
electric irons, toasters
and kettles,
5.3
