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
Core 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
PCB- Core • Made of woven textile-E glass reinforcement reinforced epoxy; designated as FR-4 • Why continuous fiber 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.
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)
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; • particle size (nano & micron size) • shape of the filler (flake, spherical, etc) • filler particle distribution (segregated or random) • Filler concentration • 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 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 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.
Table 1: Properties of glass and natural fibres * 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
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.
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.
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 • 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 • 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 • 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.
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)