Applications of PMC

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

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

Core

Via

PTH(Plated

ThroughHole) withpluggingmaterial

SR (Solder Resist)

Printed Circuit Board (PCB)

PCB- Core

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 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

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.Alternatives to solder interconnection.

Metal filled polymer composites

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

Electrical Conductivity

Silver (Ag)

Copper (Cu)

Gold (Au)

Aluminium (Al)

Nikel (Ni)

Thermal Conductivity

Silver (Ag)

Copper (Cu)

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 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

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 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:

Table 2: The use of natural fibres in automotive industries 1996 1999 2000

(Forecast)

Germany 4000 14400

Rest of EU

300 6900

Total 4300 21300 24000Interior part pf Mercedes A-200 madeBy 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.

Table 1: Properties of glass and natural fibres

Properties

Fibre

E-glass

flax hemp jute ramie coir sisal abaca cotton

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

500 220 600- 700

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

price/Kg ($), raw (mat/fabric)

1.3(1.7/3.

8)

- 1.5 (2/4)

0.6 - 1.8

(2/4)

0.351.5/0.9

- 2

1.5 - 2.5

0.25 -0.5

0.6 - 0.7

1.5 - 2.5

1.5 - 2.2

* tensile strength strongly depends on type of fibre, being a bundle or a single filament

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

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

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.

Natural Fibers

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)

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.

BONE CEMENT

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.

Problems of PMMA Bone Cement

1) Strong exothermic setting reaction2) Toxic effect of the monomer3) Inability to bond directly to bone -

caused loosening at the interface4) Brittle nature

- To overcome these problems, many types of bioactive bone cements have been developed.

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 directContactBetween bone (B)And Cement (C), while Figure (b)Shows softTissue layerLess than 10 um. The softTissue layerIn (a) and (d)Is thickerThan (b) and (c)