17-01-2013, 02:42 PM
Nanomaterials for “Green” Electronics
[attachment=47354]
Abstract:
This paper examines the use of nanomaterials in the
area of “green” technology. A variety of green materials for
advanced organic packaging have been developed. These
include capacitors and resistors as embedded passives, resin
coated Cu (RCC) as buildup layers, highly conducting nanomicro
media for Z-interconnects, lead free assembly paste,
ZnO based additives, magnetic materials, inductors and
thermal interface materials (TIM). Nanocomposites can
provide high capacitance densities, ranging from 5 nf/inch2 to
25 nF/inch2, depending on composition, particle size and film
thickness. The electrical properties of capacitors fabricated
from BaTiO3-epoxy nanocomposites showed a stable
capacitance over a temperature range from 20°C to 120 °C. A
variety of printable discrete resistors with different sheet
resistances, ranging from 1 ohm to 120 Mohm, processed
utilizing a large panel format (19.5 x 24 inches) have been
fabricated. Low resistivity nanocomposites, with volume
resistivity in the range of 10-4 ohm-cm to 10-6 ohm-cm
depending on composition, particle size, and loading can be
used as conductive joints for high frequency and high density
interconnect applications.
Introduction:
The electronics industry is under pressure from
environmental groups to remove potentially toxic compounds
such as brominated flame retardants, lead based solders and
other environmental pollutants from consumer products and
electronics [1]. It has been estimated that a 2g microchip
requires 1.6 kg of secondary fossil fuels, 72 gm of chemicals,
32 kg of water, and 0.7 kg of elemental gases [2]. European
Union (EU) generates ~ 8 million tons of electronic/electrical
waste every year.
Results and Discussion
In electronic applications, the HF materials are generally
required to possess a wide range of favorable properties
including high mechanical strength, good thermal stability and
chemical resistance, low heat distortion, high resistance to
aging, good electric insulation properties, consistent
dimensional stability over a wide temperature range, good
adhesion to glass and copper, high surface resistivity, low
dielectric constant and loss factor, ease of drillability, low
water absorption and high corrosion resistance.
In addition, a key requirement that is governed by the
Underwriters' Laboratory (UL) is the ability to meet the
flammability standard of UL 94-V0. In general thermosetting
resins alone or in combinations with other additives, which
are widely used in the electronic industry for PCB laminate
applications, meet these requirements only because they
contain approximately 20-40% brominated components.
These brominated compounds have excellent flame-retardant
properties. In the thermal processes, brominated compound
can release corrosive byproducts such as HBr, Br2 etc. The
greatest concern of brominated compound is the risk of
forming potential dioxins (extreme health hazards) by
uncontrolled pyrolysis. We have developed halogen free
laminating resins for substrate material. Halogen free resins
have advantages for multilayer substrates in terms of
processibility, thermal stability, low moisture absorption, high
Tg, and versatility.
Capacitors, resistors and inductors:
Embedded capacitors provide the greatest potential
benefit for high density, high speed and low voltage IC
packaging. Capacitors can be embedded into the interconnect
substrate (printed wiring board, flex, MCM-L, interposer) to
provide decoupling, bypass, termination, and frequency
determining functions [6]. In order for embedded capacitors to
be useful, the capacitive densities must be high enough to make
layout areas reasonable. In this paper, we report novel BaTiO3-
HF Epoxy based polymer nanocomposites that have the
potential to surpass conventional composite to produce high
capacitance density, low loss, and applicable over large surface
areas, thin film capacitors. Specifically, novel halogen free and
lead free Resin Coated Copper Capacitive (RC3)
nanocomposites capable of providing bulk decoupling
capacitance for a conventional power-power core, or for a
three layer Voltage-Ground-Voltage type power core, is
described. The second capacitor in this case study was discrete
capacitor. This capacitor is constructed using a screen/stencil
process. In the case of laminates, two thin films were prepared,
dried and then laminated together. RC3 with suitable thickness
favors buildup layers for sequential buildup process as can be
seen in Figure 3. On the other hand, laminates with proper
processing can be used as a central core for buildups. It is
interesting to note that the present process can manufacture
large size (19.5 inch X 24 inch) halogen free RC3, laminates
and printable capacitors.
Conducting adhesives for interconnects:
Greater I/O density at the die level, coupled with more
demanding performance requirements, is driving the need for
improved wiring density and a concomitant reduction in
feature sizes for electronic packages, and alternatives to the
traditional plated through hole are required for high frequency
and high density interconnect applications. One method of
extending wiring density is a strategy that allows for metal-tometal
z-axis interconnection of subcomposites during
lamination to form a composite structure [7]. There has been
increasing interest in using electrically conductive adhesives as
interconnecting materials in the electronics industry.
Conductive adhesives are composites of polymer resin and
conductive fillers. Metal–to-metal bonding between conductive
fillers provides electrical conductivity, whereas a polymer resin
provides better processability and mechanical robustness.
Conductive adhesives have been used to fill vias in
subcomposite structures, and form conductive joints to metal
planes during lamination to adjoining circuitized cores.
Typically, adhesives formulated using controlled-sized micro
particles have been used to fill small diameter holes for Zinterconnect
applications.
Thermal Interface Materials (TIM):
Thermal interface materials (TIM) are critical packaging
materials that are intended to fill gaps between mating
surfaces to enable efficient heat transfer. TIM are used in a
variety of forms like silicone and epoxy adhesives, gels,
greases, phase change materials, and metal alloys like solders.
For example, nanoparticle – aqueous ethylene glycol (EG)
based nanofluids are proposed as the next generation heat
transfer fluids because of their significantly higher thermal
transport capacities compare to the base liquids [10-11]. In
parallel significant research work has focused on nanopastes
for Z-axis interconnections, die attachments and thermal
interface materials (TIM). Nanogels have the potential to
combine the advantages of both nanofluids and nanopastes.
The combination of high thermal conductivity and stability
makes nanogels very attractive candidates for TIM.
Conclusions:
“Green” nanocomposites can be used to enhance the
conductivity of ECAs, form integrated resistors with controlled
sheet resistance, and form capacitors with high capacitance
density. The incorporation of silver nanoparticles and
microparticles has been shown to improve the sintering
behavior, and hence the conductivity, of the ECAs. A variety
of green nanocomposites well suited to fabrication of
sequential buildup technology has been developed. These
materials enable fine-feature definition with excellent control
of layer thickness. The nanocomposites can produce low loss,
low k dielectrics as buildup layers. Experiments demonstrated
that coating material is suitable for SBU whereas screen or
contact printing is suitable for conducting lead free adhesives
for interconnects, thermal interface materials (TIM) and dieattachments.
[attachment=47354]
Abstract:
This paper examines the use of nanomaterials in the
area of “green” technology. A variety of green materials for
advanced organic packaging have been developed. These
include capacitors and resistors as embedded passives, resin
coated Cu (RCC) as buildup layers, highly conducting nanomicro
media for Z-interconnects, lead free assembly paste,
ZnO based additives, magnetic materials, inductors and
thermal interface materials (TIM). Nanocomposites can
provide high capacitance densities, ranging from 5 nf/inch2 to
25 nF/inch2, depending on composition, particle size and film
thickness. The electrical properties of capacitors fabricated
from BaTiO3-epoxy nanocomposites showed a stable
capacitance over a temperature range from 20°C to 120 °C. A
variety of printable discrete resistors with different sheet
resistances, ranging from 1 ohm to 120 Mohm, processed
utilizing a large panel format (19.5 x 24 inches) have been
fabricated. Low resistivity nanocomposites, with volume
resistivity in the range of 10-4 ohm-cm to 10-6 ohm-cm
depending on composition, particle size, and loading can be
used as conductive joints for high frequency and high density
interconnect applications.
Introduction:
The electronics industry is under pressure from
environmental groups to remove potentially toxic compounds
such as brominated flame retardants, lead based solders and
other environmental pollutants from consumer products and
electronics [1]. It has been estimated that a 2g microchip
requires 1.6 kg of secondary fossil fuels, 72 gm of chemicals,
32 kg of water, and 0.7 kg of elemental gases [2]. European
Union (EU) generates ~ 8 million tons of electronic/electrical
waste every year.
Results and Discussion
In electronic applications, the HF materials are generally
required to possess a wide range of favorable properties
including high mechanical strength, good thermal stability and
chemical resistance, low heat distortion, high resistance to
aging, good electric insulation properties, consistent
dimensional stability over a wide temperature range, good
adhesion to glass and copper, high surface resistivity, low
dielectric constant and loss factor, ease of drillability, low
water absorption and high corrosion resistance.
In addition, a key requirement that is governed by the
Underwriters' Laboratory (UL) is the ability to meet the
flammability standard of UL 94-V0. In general thermosetting
resins alone or in combinations with other additives, which
are widely used in the electronic industry for PCB laminate
applications, meet these requirements only because they
contain approximately 20-40% brominated components.
These brominated compounds have excellent flame-retardant
properties. In the thermal processes, brominated compound
can release corrosive byproducts such as HBr, Br2 etc. The
greatest concern of brominated compound is the risk of
forming potential dioxins (extreme health hazards) by
uncontrolled pyrolysis. We have developed halogen free
laminating resins for substrate material. Halogen free resins
have advantages for multilayer substrates in terms of
processibility, thermal stability, low moisture absorption, high
Tg, and versatility.
Capacitors, resistors and inductors:
Embedded capacitors provide the greatest potential
benefit for high density, high speed and low voltage IC
packaging. Capacitors can be embedded into the interconnect
substrate (printed wiring board, flex, MCM-L, interposer) to
provide decoupling, bypass, termination, and frequency
determining functions [6]. In order for embedded capacitors to
be useful, the capacitive densities must be high enough to make
layout areas reasonable. In this paper, we report novel BaTiO3-
HF Epoxy based polymer nanocomposites that have the
potential to surpass conventional composite to produce high
capacitance density, low loss, and applicable over large surface
areas, thin film capacitors. Specifically, novel halogen free and
lead free Resin Coated Copper Capacitive (RC3)
nanocomposites capable of providing bulk decoupling
capacitance for a conventional power-power core, or for a
three layer Voltage-Ground-Voltage type power core, is
described. The second capacitor in this case study was discrete
capacitor. This capacitor is constructed using a screen/stencil
process. In the case of laminates, two thin films were prepared,
dried and then laminated together. RC3 with suitable thickness
favors buildup layers for sequential buildup process as can be
seen in Figure 3. On the other hand, laminates with proper
processing can be used as a central core for buildups. It is
interesting to note that the present process can manufacture
large size (19.5 inch X 24 inch) halogen free RC3, laminates
and printable capacitors.
Conducting adhesives for interconnects:
Greater I/O density at the die level, coupled with more
demanding performance requirements, is driving the need for
improved wiring density and a concomitant reduction in
feature sizes for electronic packages, and alternatives to the
traditional plated through hole are required for high frequency
and high density interconnect applications. One method of
extending wiring density is a strategy that allows for metal-tometal
z-axis interconnection of subcomposites during
lamination to form a composite structure [7]. There has been
increasing interest in using electrically conductive adhesives as
interconnecting materials in the electronics industry.
Conductive adhesives are composites of polymer resin and
conductive fillers. Metal–to-metal bonding between conductive
fillers provides electrical conductivity, whereas a polymer resin
provides better processability and mechanical robustness.
Conductive adhesives have been used to fill vias in
subcomposite structures, and form conductive joints to metal
planes during lamination to adjoining circuitized cores.
Typically, adhesives formulated using controlled-sized micro
particles have been used to fill small diameter holes for Zinterconnect
applications.
Thermal Interface Materials (TIM):
Thermal interface materials (TIM) are critical packaging
materials that are intended to fill gaps between mating
surfaces to enable efficient heat transfer. TIM are used in a
variety of forms like silicone and epoxy adhesives, gels,
greases, phase change materials, and metal alloys like solders.
For example, nanoparticle – aqueous ethylene glycol (EG)
based nanofluids are proposed as the next generation heat
transfer fluids because of their significantly higher thermal
transport capacities compare to the base liquids [10-11]. In
parallel significant research work has focused on nanopastes
for Z-axis interconnections, die attachments and thermal
interface materials (TIM). Nanogels have the potential to
combine the advantages of both nanofluids and nanopastes.
The combination of high thermal conductivity and stability
makes nanogels very attractive candidates for TIM.
Conclusions:
“Green” nanocomposites can be used to enhance the
conductivity of ECAs, form integrated resistors with controlled
sheet resistance, and form capacitors with high capacitance
density. The incorporation of silver nanoparticles and
microparticles has been shown to improve the sintering
behavior, and hence the conductivity, of the ECAs. A variety
of green nanocomposites well suited to fabrication of
sequential buildup technology has been developed. These
materials enable fine-feature definition with excellent control
of layer thickness. The nanocomposites can produce low loss,
low k dielectrics as buildup layers. Experiments demonstrated
that coating material is suitable for SBU whereas screen or
contact printing is suitable for conducting lead free adhesives
for interconnects, thermal interface materials (TIM) and dieattachments.