Applications of PMC

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Applications of PMC
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PMC for electronics

• 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 non-conductive substrate
• Most PCBs are composed of between one and
  twenty-four conductive layers separated and
  supported by layers of insulating material

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Printed Circuit Board (PCB)
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Printed Circuit Board (PCB)

• 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
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PCB- Core

• Made of woven textile-E glass reinforcement
  reinforced epoxy designated as FR-4
• Why continuous fiber is used as core in PCB?

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PCB-Solder Resist

• 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.

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PCB-Holes

• 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

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Electrical Conductive Adhesives

• Alternatives to solder interconnection.

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Metal filled polymer composites

• Metal fillers act as conductive path to conduct
  heat and electric in the composites

Thermal Conductivity Silver (Ag) Copper
(Cu) Aluminium (Al) Gold (Au) Nikel (Ni)
Electrical Conductivity Silver (Ag) Copper
(Cu) Gold (Au) Aluminium (Al) Nikel (Ni)
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Typical dependence of electrical conductivity
(logarithm) on conductive filler volume fraction
Sharp conductivity increase occurs within the
concentration region fc1ltfltfc2 . This
phenomenon is called percolation threshold
Insufficient physical contact of metal fillers
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• The percolation behavior is primarily affected
  by
• particle size (nano micron size)
• shape of the filler (flake, spherical, etc)
• filler particle distribution (segregated or
  random)
• Filler concentration
• Oxide layer thickness

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Example Polyimide Electrically Conductive Die
Attach Adhesive

• 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

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PMC as Underfill Encapsulant Materials

• 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 encapsulants effectiveness is measured by its
  ability to delay or prevent failures.

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PMC for automotives

• 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

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The use of natural fibres in automotive
industries has grown rapidly over the last 5
years, see Table 2

• Table 2 The use of natural fibres in automotive
  industries

Interior part pf Mercedes A-200 made By natural
mat thermoplastic
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.
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Table 1 Properties of glass and natural fibres
tensile strength strongly depends on type of
fibre, being a bundle or a single filament
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Natural Fibers

• 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

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Natural Fibers

• 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.

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Natural Fibers

• 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.

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BONE CEMENT

• 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)

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BONE CEMENT

• 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.

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PMC for Medical Applications

• 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.

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Problems of PMMA Bone Cement

• 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

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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)