Transcript Applications of PMC - USM :: Universiti Sains Malaysia

Applications of PMC
PMC for electronics
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Alternative names are printed wiring board
(PWB)
Printed circuit boards, or PCBs, are used
to mechanically support and electrically
connect electronic components using
conductive pathways, or traces, etched from
copper sheets laminated onto a nonconductive substrate
Most PCBs are composed of between one and
twenty-four conductive layers separated and
supported by layers of insulating material
Printed Circuit Board (PCB)
Printed Circuit Board (PCB)
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Layers may be connected together
through drilled holes called vias
Some PCBs have trace layers inside the
PCB and are called multi-layer PCBs
Via
SR (Solder Resist)
PTH
(Plated
Through
Hole) with
plugging
material
Core
PCB- Core
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Made of woven textile-E glass
reinforcement reinforced epoxy;
designated as FR-4
Why continuous fiber is used as core in
PCB?
PCB-Solder Resist
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Areas that should not be soldered to
may be covered with a polymer solder
resist (solder mask) coating
The solder resist prevents solder from
bridging between conductors and
thereby creating short circuits.
Solder resist also provides some
protection from the environment.
PCB-Holes
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The walls of the holes, for boards with
2 or more layers, are plated with copper
to form plated-through holes
Function; electrically connect the
conducting layers of the PCB
Electrical Conductive
Adhesives
Alternatives to solder interconnection.
Metal filled polymer
composites
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Metal fillers act as conductive path to
conduct heat and electric in the
composites
Electrical Conductivity
Thermal Conductivity
Silver (Ag)
Silver (Ag)
Copper (Cu)
Copper (Cu)
Gold (Au)
Aluminium (Al)
Nikel (Ni)
Aluminium (Al)
Gold (Au)
Nikel (Ni)
Typical dependence of electrical conductivity
(logarithm) on conductive filler volume fraction
Sharp conductivity increase
occurs within the concentration
region φc1<φ<φc2 . This
phenomenon is called
percolation threshold
Insufficient physical contact of metal fillers
The percolation behavior is primarily affected
by;
(1) particle size (nano & micron size)
(2) shape of the filler (flake, spherical, etc)
(3) filler particle distribution (segregated or
random)
(4) Filler concentration
(5) Oxide layer thickness
Example; Polyimide Electrically
Conductive Die Attach Adhesive
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silver filled, electrically conductive polyimide adhesive
This product is designed for die attachment and surface mount applications.
Other applications include, but are not limited to assembling electrical and
electronic components.
The cure schedule allows for rapid processing and the resulting bond
exhibits excellent thermal stability and adhesion at high temperatures.
APPLICATIONS:
• Die attachment
• Printed circuit board fabrication
• Sealing and high performance coatings
• Advanced material composites
PMC as Underfill Encapsulant
Materials
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Typically are silica-filled epoxies
Underfill encapsulants were
developed to encase flip-chip ICs
A flip chip has a lower coefficient of
thermal expansion (CTE) than the
substrate onto which it is assembled.
During thermal cycling, this CTE
mismatch results in movement of the
flip chip, board and mechanical fatigue
of solder joints. Cyclic fatiguing
eventually ends in IC failure.
An encapsulant’s effectiveness is
measured by its ability to delay or
prevent failures.
PMC for automotives
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Composites are being used more and more in
the automotive industry
Due to their strength, weight, quality and
cost advantages
Many automotive components are already
produced in natural composites, mainly based
on polyester or PP and fibres like flax, hemp
or sisal.
The adoption of natural fibre composites in
this industry is lead by motives of a) price b)
weight reduction and c) marketing
('processing renewable resources') rather
than technical demands
The use of natural fibres in automotive
industries has grown rapidly over the last 5
years, see Table 2:
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Interior part pf Mercedes A-200 made
By natural mat thermoplastic
Table 2: The use
of natural fibres
in automotive
industries
1996
1999
Germany
4000
14400
Rest of
EU
300
6900
Total
4300
21300
2000
(Forecast
)
24000
In 1999, natural fibres used in the automotive industries comprised 75 percent flax,
10 percent jute, 8 percent hemp, 5 percent kenaf and 2½ percent sisal.
Table 1: Properties of glass and natural fibres
Fibre
Properties
Eglass
flax
hemp
jute
ramie
coir
sisal
abaca
cotto
n
Density g/cm3
2.55
1.4
1.48
1.46
1.5
1.25
1.33
1.5
1.51
Tensile strength*
10E6 N/m2
2400
800 1500
550 900
400 800
500
220
600700
980
400
E-modulus (GPa)
73
60 - 80
70
10 - 30
44
6
38
12
Specific (E/density)
29
26 - 46
47
7 - 21
29
5
29
8
Elongation at failure
(%)
3
1.2 - 1.6
1.6
1.8
2
15 - 25
2-3
3 - 10
Moisture absorption
(%)
-
7
8
12
12 -17
10
11
8 - 25
1.3
(1.7/3.
8)
- 1.5
(2/4)
0.6 1.8
(2/4)
0.35
1.5/0.9
-2
1.5 2.5
0.25 0.5
0.6 0.7
price/Kg ($), raw
(mat/fabric)
* tensile strength strongly depends on type of fibre, being a bundle or a single filament
1.5 2.5
1.5 2.2
Natural Fibers
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Bast fibres (flax, hemp, jute, kenaf,
ramie (china grass)) - the bast consists
of a wood core surrounded by a stem.
Within the stem there are a number of
fibre bundles, each containing individual
fibre cells or filaments. The filaments
are made of cellulose and
hemicellulose, bonded together by a
matrix, which can be lignin or pectin
Natural Fibers
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Leaf fibres (sisal, abaca (banana),
palm) - In general the leaf fibres are
coarser than the bast fibres.
Applications are ropes, and coarse
textiles. Within the total production of
leaf fibres, sisal is the most important.
Natural Fibers
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Seed fibres (cotton, coir, kapok)
Cotton is the most common seed fibre and is
used for textile all over the world. Other seed
fibres are applied in less demanding
applications such as stuffing of upholstery.
Coir is an exception to this. Coir is the fibre of
the coconut husk, it is a thick and coarse but
durable fibre. Applications are ropes, matting
and brushes.
BONE CEMENT
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Acrylic cement is used for the fixation of
total joint prosthesis
The cements used in orthopedic surgery
are combination of prepolymerized PMMA
solid particle and the liquid monomer
The powder particles are sphere (30 to
150 µm in diameter), molecular weight of
20,000 to 2 million
For the reaction to occur,prepolymerized
PMMA needs to contain an initiator,
dibenzoyl perioxide (BP)
BONE CEMENT
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Bone cement, or
poly(methyl
methacrylate) (PMMA), is
commonly used to
anchor hip prostheses in
the femur.
The material is very
brittle, however, and
prone to fracture, fatigue
and wear.
PMC for Medical Applications
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Currently PMMA is the polymer most commonly used
as a bone cement for the fixation of total hip
prostheses.
Ideally, a bone cement material should be easy to
handle, biologically compatible, nonsupporting of oral
microbial growth, available in the particulate and
molded forms, easy to obtain, nonallergenic,
adaptable to a broad range of dental and medical
applications, in possession of high compressive
strength, and effective in guided tissue regenerative
procedures.
Problems of PMMA Bone
Cement
1)
2)
3)
4)
Strong exothermic setting reaction
Toxic effect of the monomer
Inability to bond directly to bone caused loosening at the interface
Brittle nature
- To overcome these problems, many
types of bioactive bone cements have
been developed.
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To improve the biochemical properties
of PMMA bone cement, many types of
bioactive particle fillers have been
added into the cement
Example of particle fillers are glass
ceramic, titania (anatase & rutile), etc
Recent studies on Bone Cement + titania particles (K. Goto
et al., Biomaterials 26 (2005))
Figure (c)
Shows direct
Contact
Between bone (B)
And Cement (C),
while Figure (b)
Shows soft
Tissue layer
Less than
10 um. The soft
Tissue layer
In (a) and (d)
Is thicker
Than (b) and (c)