since 1981

The Computer - how it's made

A computer is made of electronic, plastic and metal components assembled together , with different pur pose. There are four main parts:

• Main unit
• Monitor
• Keyboard
• Peripherals

Main unit
The main uniti s made of boards and printed circuits with a plastic support, on which are fixed integrated circuits, condensers, resistors and  inductors. All these elements are connected together with a conductor material.

Boards and printed cirucits
For the production of the printed circuits boards, the main raw materials used are:

• polymer laminates made of thermosetting  resin reinforced with fibre glass (usually epoxy or phenolic sometimes also polyesters, melamine, etc…);
• Inks  and screen printing pastes;
• photopolymers  (made of  polyester, acrilic, etc.);
• inorganic chemicals  and organic  for the phases of filler and removal by means of electrochemical processes and for the removal of the photopolymer and copper;
• protective coatings;
• holding and thinners;
• precious and non-precious metals.

A printed circuit is made of:
• 33% of ceramic and glass components and packaging, reinforcements PCB (Printing Wiring Board);
• 33% of plastics in the PWB, components and packaging in the connectors;
• <1% of paper and liquids in the capacitors;
• 33% of metals in the conductors of the components, in the boards of PWB.

Present also the following componets:
• 12% coil (conductor components, the slopes of the PWB, connectors);
• - 7% iron (conductors of the components, mechanical details, inductors);
• 2% nichel (components and conductors of the components);
• < 1% zinc (surface treatments);
• < 1% tin (welding);
• 1% lead (welding);
• < 1% manganese (dry electronic capacitors);
• < 1% antimony  (welds components and assemblies);
• - < 8% other metals (chrome, titanium, tungsten, silver, palladium, aluminum, barium, boron, beryllium, cobalt, ecc.).

Integrated circuits
The integrated circuits are made of a matrix in a semiconductor material, usually silicon, encapsulated in a case that can be ceramic or plastic with metal conductors linked to the other components. Plastic case is the most widespread for printed circuits, it represents more than 90% of all the cases for the printed circuits.
The plastic case components:
• inert filler 65-75%, usually silicate, SiO2;resina epossidica 20-30%;
• a flame retardant consisting of 2-6% antimony oxide Sb2O3;
• hardener 1-10%, typically an amine hardener (5-30% del peso totale della resina);
• 0.6 to 1% accelerator consisting of a Lewis acid, eg boron trifluoride, in the form of its complex monoetilamminico (approximately 3% of the weight of the resin);
• 0.5% dye usually made from carbon black;
• release agent of the compound usually natural carnauba wax.

Leadframe has made of silicon, small part  of bromo, phosphor, arsenic and antimony, and is covered by a very small layer of aluminum, about 0.001 mm, sometimes even as plastic or ceramic to protect the whole.
The connections of the chip with the leadframe are generally constituted by alumina, with the addition of oxides of magnesium, calcium, silicon and titanium. Other semiconductor materials generally used are germanium, gallium arsenide, gallium phosphide, indium phosphide and arsenide / gallium phosphide.  The germano is used for diodes and other materials, usually for the LEDs. The diodes are usually constructed using silicon and germanium.

There are several types of capacitors, characterized by different dielectric materials. The capacitors most commonly used are:
• metallized paper capacitors consist of two strips of cellulose, metallized on one side with a thin film of zinc or other metal with low melting point, also contain paper, zinc, lead, tin, iron and copper;condensatori di plastica metallizzata, con la stessa composizione   dei precedenti, possono contenere policarbonato, polipropilene;
• aluminum electrolytic capacitors, contain boric acid, mixed with glycol, salts and organic solvent, the latter may be butyrolactone, dimethylformamide or dimethylacetamide, as electrolyte. Other substances usable in this sense, are the methylpyrrolidone, ethylene glycol, adipic acid, a nitrophenol and organic amine compounds;
• Tantalum electrolytic capacitors, run through the same principle of aluminum electrolytic capacitor and use as Ta2O5 dielectric layer and manganese dioxide as the electrolyte.
They are composed of a ceramic support in alumina on which is deposited a layer of conductive metal or mixture of glass-coal. The terminals are generally of gold, palladium-silver or materials having the same electrical properties.

They consist of a winding of copper wire around a ceramic core or ferromagnetic. The inductor can then be coated with an epoxy resin. The ferromagnetic core may be in sintered iron with organic binders, alloy Fe-Ni or Fe-Zn, and may contain Sm, Pr, Co or Nd.

Relays are used with peripheral control functions and are characterized by low power loss, low sensitivity to external noise and high reliability.
The most common materials used in relays are iron, copper and epoxy resins. The properties of the spring contacts copper are generally improved with the use of beryllium. In the magnetic parts are used Fe, Ni, Mn, Zn, Co, Cr, Si, Mo, Ti, C, V, Ba, Sm, Sr, If, Pr and Nd. A core for high performance often contains Fe combined with Sm, Nd and Co. 

Welding and adhesives
The welds are generally made with alloys consisting of from 63% tin and 37% lead. For SMT (Surface Mount Technology) are commonly used alloys to 2% silver, 36% lead and 62% tin. The total use of silver is not significant since only 10% of electronic components using SMT soldering. Other welding materials are antimony-tin alloys, bismuth-tin, indiostagno. The adhesives most commonly used are generally constituted by compounds of nature epoxy or acrylic.

Printed Wiring Board (PWB)
There are two major groups of PCB with and without reinforcement. The PWB without reinforcement may be flexible or rigid. The most common types of reinforcement are constituted by plots of glass and cellulose paper. The resins used for the PCB with reinforcement generally contain brominated flame retardants.

The lights are typically made up of LEDs. They contain small amounts of semiconductor materials consisting of InP or GaP.

The casing of the unit of processing data is metal with plastic parts (about 300 gr).

The monitor of the computer equipment also contain printed circuit boards with a total area of 500 cm2, as well as CRT and LCD display.

Cathodic Tube
A cathode ray tube for and consists essentially of four parts: Part conical, Screen, Connection BETWEEN cone and screen and alter the electronic part.
The glass used for the manufacture of cathode ray tubes may be of different types, but all containing metallic oxides capable of absorbing the rays (PbO, BaO, SrO). The fluorescent substances contained within the screen are typically sulfides or phosphides of zinc, europium, yttrium, cadmium batteries.
In older models the fluorescent coating contains mainly sulphides, cadmium and zinc, while in newer models accounting for 94% of zinc sulphide and rare earths.

There are various types of display:
• Liquid crystal display which use 2000 different types of liquids, including trans-4-propyl-(4-cyanophenyl)-cyclohexane and the azossilbenzene, while, the lamp for backlighting the screen generally contains mercury or other rare metals;
• Plasma display contain mercury or radioactive isotopes such as Ni63, Kr85 or H3;
• Electroluminescent displays are generally based compounds ZnS and heavy metals or metals of the group of rare earths.
Display case
The casing of the monitor is made of ABS plastic or similar containing about 20% of the flame retardant (deca or octa-BDE) and has a weight of about 1.7 Kg

Consists essentially of printed circuit boards for an extension of about 200 cm2 and the plastic coating.
The main materials that make up a computer can be broadly grouped in this way:

Items                                                         Weight (kg)               %
Ferrous metals                                          7,5                          32
Non ferrous metals                                   0,5                            2
Galss                                                           3,6                          15
Plastic                                                          5,2                          22
Printed circuit borads (PCB)                    5,3                          23
Disks                                                            1,2                             5
Total                                                            23,3                         100
CHIBO S.r.l.
Via Nobel, 27/29A SPIP- 43122 Parma - Italy
Tel. (+39) 0521/606611
Fax. (+39) 0521/607750
P.IVA 00762480341
Cap. Soc. iv 109.200,00 Euro

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