Carbon materials of graphite conductive and origin of

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					Carbon materials of graphite conductive and origin, and it is very
difficult to crushing and dispersion, to the application to bring very
great difficulty; carbon black conductive although very good, but the
processing difficulties; TiOz, Pd0 metal oxide conductive property is
poor, it is difficult to make high quality electrode. Commonly used metal
conductive phase for the low resistance of Au, Ag, Cu, Ni and other metal
powder, the best performance of the Au powder, Ag powder but is
expensive; the price is relatively low, but under the action of the
electric field Ag can generate electric migration phenomenon, the
conductivity decreases, affect the service life of Cu,; Ni powder is
cheaper, in the electric field does not produce migration, but when the
temperature increase, oxidation will occur, leading to resistivity,
therefore can only be used under low temperature. In order to reduce the
contact resistance between the particles, improve the conductive
performance, some low melting point alloy applied in low temperature
slurry. In the electronic slurry curing process, with the rise of
temperature, the low melting point alloy in the metal particles forming
the connection between channels, reduce the resistance to.
The 1.2 bonding phase ( glass )
Bond is usually made of glass, crystal or two mixtures of combination,
its main role is to firmly combine curing coating and substrate, bonding
phase selection on film mechanical properties and electrical properties
have certain effect, bonding glass, glass type, mixture type three class.
Glass refers to a certain metal or non-metal oxide, its main role is in
the thick film components during sintering, taut, connecting fixed
conductive phase particles [3], and the whole film layer and substrate is
firmly bonded together. According to the glass in the main role, oxide
can be broadly divided into three categories: the first category is
composed of glass basic skeleton of the oxides, such as SIOZ, BZ O, etc.,
they alone can form excellent mechanical and electric properties of
glass; second category is the regulation of glass physics, chemical
properties of oxides, such as A1203, PbO, BaO, ZnO, they can improve the
coefficient of thermal expansion of the glass, mechanical strength,
thermal and chemical stability; third for improved glass properties of
oxides, such as PbO, BaO, BZ 03, Ca van, they can reduce the temperature
of the molten glass, but also to ensure that the glass electrical and
chemical properties.
Glass bonded phase is mainly through the oxide and the substrate to react
and form and binding, the bonded phase is generally a copper oxide,
commonly used is Cu0 or Cue O, sometimes adding some Cd, Cu-Cd
aluminosilicate formation, so that the reaction temperature.
Bonded phase is a mixture of the two glass and glass phase mixing, play
their respective advantages.
1.3 organic carrier
Organic carrier is dissolved in an organic solvent of the polymer
solution, it is a function of phase and binder phase particulate carrier,
plays in the control of slurry rheological behavior, adjust slurry
viscosity, so that the solid state conductive phase, adhesive phase and
the other roles in the solid particle mixture is dispersed into a fluid
properties of the slurry, in order to transfer to a substrate, forming a
desired pattern. Organic carrier is mainly composed of organic solvent
and a thickener called, in order to improve their mobility, can add
surfactant; in order to control the firing is easy to occur when the two
flow phenomenon, should add flow control agent in order to improve
ductility; paste thixotropy, to add thixotropic agents, gelling agent; in
order to reduce the medium paste in printing after the hole, ensure the
insulating properties, also need to add defoaming agent.
Organic solvents are mainly terpineol, mushroom products alcohol (
molecular weight: 154.3), butyl carbitol, butyric acid butyl carbitol,
isopropanol or toluene, content requirements for 9100-9500. Thickener
organic binder, its role is to increase the viscosity of the slurry,
covering the solid particles to prevent particles agglomeration,
agglomeration and precipitation, and give appropriate rheological
properties of slurry in the slurry, printing, after drying, so that the
solid particles are bonded together, has a certain strength. Commonly
used thickener with ethyl cellulose, nitrocellulose, acrylic resin,
resin, polyethylene of ethylene, butyraldehyde poly hexene ethanol, poly
a methyl styrene, poly hexylene acetic acid cool and styrene [S7, to
adjust the viscosity of organic solvent. In organic solvents can also add
methyl silicate, silicic acid four ethyl ester or benzene methyl silicone
oil as defoaming agent. In addition, adding poly methacrylate or phthalic
acid two small fat can improve medium pulp molding and leveling of the [
[ s.77
1.4 electronic slurry preparation method
Electronic slurry preparation process such as shown in figure 1. Metal
powder, glass powder, organic carrier were ready, can carry on the mixing
and dispersing. In order to make the metal powder and glass and organic
carrier composed of homogeneous and fine paste, mixed powder must mix
with carrier, and then grinding, which is uniformly dispersed in the
carrier. Slurry to repeated grinding, to meet the requirements of the
dispersion.
Fig 1 electronic slurry preparation process flow diagram

The 2.1 noble metal slurry
Ag and Ag based electronic slurry
In 2.1 . 1 Ag slurry
Ag is conducting the best performance of the metal material, cheaper than
Au, Pd, Pt and other precious metals in low, is used widely in the
production of. But Ag conductor as thick film hybrid circuit conductive
strip, capacitor and resistor termination materials, can produce Ag `
migration [8 ].
General in the Ag slurry only add trace metals, and according to
different use requirements of the added metal is also different. The new
process is added to the slurry of metal organic compounds, metal Ag and
organic form of coordination compounds, to improve the dispersion of the
slurry [ 9).
With China's rapid development of the electronic industry, Ag powder
material in electronic technology, chemical industry, medicine and other
fields has been more widely used, more and more big market potential.
2.1.2 Ag-Pd slurry
In Ag add certain quantity of Pd, Ag-Pd prepared conductor paste can
effectively inhibit the silver ion migration. In Ag-Pd paste, Ag +
diffusion speed of only a fraction of the pure Ag, and even an order of
magnitude less. The content of Pd according to the use requirement and
constant, usually 15% - 25%, the commonly used value of 200o0
In the Ag-Pd conductor, conductor resistance values with the Ag content
increased and decreased, but the content of Ag if too much will not only
cause the Ag + migration, may also make the soldering decline. When the
Pd / ( Pd+Ag ) > 0.1, has a remarkable effect on improving migration. Ag-
Pd line conductor in the 400 ^ - 700 DEG C occurs between the oxidation
of Pd, Pd0, will reduce the conductor weldability, thus the content of Pd
too much will result in welding zone of wettability variation.
2.2 Au and Au based electronic slurry
In 2.2 . 1 Au slurry
Has been the development of a variety of types of Au conductor paste is
mainly divided into glass containing Au conductor material and impose
human Cu0 oxide glass Au conductor paste and adding glass and oxide Au
conductor paste. The Au conductor paste containing glass won't appear
like Ag migration phenomenon, and the performance is stable, reliable.
But its adhesive strength is poor, and after repeated heavy firing,
attachment strength will decline [ Elol
Au conductive paste for multilayer wiring conductor, microwave hybrid
integrated circuit, and thin film technology matching circuit, and a
power transistor chip and lead frame welding etc..
In 2.2 . 2 Au-Pd slurry
In order to improve the adhesion strength of pure Au conductor of the
shortcomings of poor, in the Au add certain quantity of Pd, Au-Pd formed
of conductive paste. Au-Pd conductor not only higher adhesion strength,
weldability, but also with the Pd-Ag series resistance, while firing,
forming low noise exposure [ Ell]. Because the system does not exist the
diffusion phenomena, it is often used in high reliability and multilayer
wiring.
According to the experiment, Au-Pd conductor paste for major constituents
in the following range of desirable: Pd : 80o-150o, Au: 73%-800o, glass:
1200 - 1900. It should be noted, Au-Pd is a Pd content of not more than
2500, or because the Pd0 appeared in large numbers, will make the
conductor resistance increases, not suitable for conductor.
2.3 Pd-Ag slurry
Pd-Ag resistor paste is the earliest development and widely application
of thick film resistor material. Pd-Ag slurry making resistor performance
depends mainly on the firing of Pd0 content; Ag addition can reduce the
noise and improve the stability, temperature coefficient. General Pd : Ag
= 1.5: 1
Pd-Ag resistor pastes whether electric performance and process
performance is good, cost is low, but the firing conditions are very
sensitive, and when the resistance is larger when the noise is big,
temperature is difficult to control to the smaller numerical, in addition
to a reducing atmosphere is also very sensitive.
2.4 group Pt slurry
This kind of resistance paste with platinum, iridium ( Pt ) ( Ir ), nail
( Ru ) and other precious metals for resistance material, which is mainly
used for thick film platinum resistor temperature measuring element.
Thick film platinum resistance thermometer in the nineteen seventies
began development, now the international market, have been sold as a
commodity. The thick film platinum temperature measuring element for heat
storage stability and resistance to thermal shock stability is very good.
Pt resistor paste function which is mainly composed of 99.95% purity,
particle size < 0.5 [ cm ultrafine Pt powder.
3 base metal slurry
3.1 Ni slurry
Metal Ni has good conductivity, chemical stability and weldability.
Nanometer Ni powder made of conductive phase Ni conductive paste screen
printing performance. So Ni conductive paste is a kind of more ideal
thick-film conductive paste. But should pay attention to guarantee the Ni
metal particle surface in high temperature burning conditions without
oxidation.
Ni powder in the paste content is very high, it was decided to main
factors of electrode performance [12 ] O Ni powder by high temperature
sintering sintering to form a metal network structure, but with the
ceramic substrate binding strength of low, only by glass bonding. In
general, the glass powder content is very low, the degeneration is very
good, in the electrode sintering temperature, rheology good glass can
flow through the metal net of small gap, so that the metal net firmly
attached to the substrate. Some Ni slurry to be in low oxygen content and
sintering atmosphere sintering, sintering process is complex, the
requirement of equipment high [13 ].
3.2 Cu slurry
Cu metal than gold has more excellent high frequency characteristics and
conductivity, and no Ag + migration defects. Has been the development of
the Cu electrode paste is mainly divided into glass containing Cu
electrode material, adding oxides without Cu glass electrode slurry, and
at the same time adding glass and oxide Cu electrode slurry [ 14j. In
preparing to consider when Cu particles may be in high temperature
oxidation burning condition.
The reported Cu conductive oxidation technology are: Cu powder surface
silver slurry, adding reductant protection, Cu powder organic phosphorus
compound, polymer dilute solution treatment, coupling agent treatment
technology. Also can use the sol - gel method in Cu powder coated with a
layer of SiOZ-Al film, coated film on improving Cu powder during high
temperature sintering oxidation resistance plays an important role in. In
addition, coating layer also reduces Cu powder sintering temperature.
3.3 Al slurry
A1 electrode paste has the advantages of low price, stable electrical
performance. A1 and Si to form a p-n junction, having a long wavelength
response characteristics, but also to the PTC thermistor porcelain body
has good ohmic contact characteristic, but also has good resistance to
aging [E157, so A1 conductor pastes were selected for the PTC thermistor
electrode material and the ground uses single crystal Si solar cell back
field material.
However, A1 paste electrode impact current is low, the bigger impact
current, electrode in contact office more prone to arc phenomenon, even
burning of the electrode. Therefore, in the A1 electrode and sintering a
layer of Ag electrode as a two protective measures.
3.4 Zn slurry
Zn on PTC thermistor porcelain body has good ohmic contact property and
ageing resistance, so the Zn slurry is also available as an PTC
thermistor electrode materials [E167, at the same time, with the Ni
conductor paste instead of Ag conductor size, can overcome the Ag
electrode of the plasma display panel on the sputtering phenomenon, the
plasma display panel of life greatly extend [ LV ].
Usually, the fine powder is Zn ( 15um ), boron silicon glass powder and
an organic binder in certain proportion according to the traditional
method of preparation of slurry. In order to prevent Zn powder on
sintering process of oxidation, in a slurry adding a certain amount of
metal organic compounds as antioxidants.
4 electronic pastes research and application development trends
( 1) electronic paste lead-free
In the electronic slurry by lead can reduce the size of the sintering
temperature, energy saving, traditional electronic slurry lead emissions
are generally more than 5000, leaded glass powder in the production
process will cause serious pollution to the environment, leading to the
leaded materials manufacturing electronic slurry method has been unable
to meet the people on the environment protection requirement. Therefore,
manufacturing lead and precious metal and has a good performance and low
price of electronic material, has become an important issue to be
resolved [ E183 has been the development of lead-free electronic pastes
are mainly Zn0-B2 O3-Si02. Zn0-Bit 03-B2 03, P2 03 and V2 O, Zn0-B2 03
series.
( 2) base metal slurry instead of precious metal pastes
Some base metal materials in some areas than the precious metal has more
excellent properties. As a result of Al, Ni and Zn on PTC thermistor
porcelain body has good ohmic contact property and ageing resistance, so
it is often chosen as the PTC thermistor electrode materials [191 o Cu
than gold is more excellent high frequency characteristics and
conductivity, more important is to do not have Ag + migration defects, so
Cu conductor paste is microwave circuit and microelectronic circuit good
materials [E201 o Ag electrodes in a plasma display panel of the
sputtering phenomenon is more serious, with Ni conductor paste instead of
Ag conductor size, can overcome these shortcomings, and the plasma
display panel greatly extended the lifespan. The base metal has the
unique superiority, has aroused the attention of people [211
( 3) cost-effective electronic paste
With the rapid development of information industry, electronic paste as
its key materials play an important role. Therefore, high performance,
low cost raw materials will greatly improve the electronic product
competition ability, must also be electronic pastes own industrial
development inevitable condition. Through the study on the composite of
precious metal pastes and other matrix slurry, which has excellent
performance to ensure the quality of electronic products, and reduce the
cost of production will be in the actual production has a good prospect.
Electronic composite slurry method mainly metal / metal ( metal oxide )
type: with excellent electrical properties of the metal cover of another
metal, forming a functional gradient composite conductive filler; metal /
non-metallic type: with excellent electrical properties of the metal
coated lightweight non-metallic core material, get a good properties
composite conductive filler; polymer / polymer coated non-metallic type:
lightweight non-metallic core material, quality of light, especially
under high frequency bandwidth shielding composite conductive filler;
blending [22?: dissimilar filler blend.

				
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Description: Carbon materials of graphite conductive and origin, and it is very difficult to crushing and dispersion, to the application to bring very great difficulty; carbon black conductive although very good, but the processing difficulties; TiOz, Pd0 metal oxide conductive property is poor, it is difficult to make high quality electrode. Commonly used metal conductive phase for the low resistance of Au, Ag, Cu, Ni and other metal powder, the best performance of the Au powder, Ag powder but is expensive; the price is relatively low, but under the action of the electric field Ag can generate electric migration phenomenon, the conductivity decreases, affect the service life of Cu,; Ni powder is cheaper, in the electric field does not produce migration, but when the temperature increase, oxidation will occur, leading to resistivity, therefore can only be used under low temperature. In order to reduce the contact resistance between the particles, improve the conductive performance, some low melting point alloy applied in low temperature slurry. In the electronic slurry curing process, with the rise of temperature, the low melting point alloy in the metal particles forming the connection between channels, reduce the resistance to. The 1.2 bonding phase ( glass )