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CHAPTER 1

COMPANY PROFILE

1.1 INTRODUCTION

Autopal group, a 40 years old enterprise with excellence and pioneer-ship in many engineering

and lighting products. Embedded with many international acclaimed quality & product

certification the company has established world-wide marketing network with agents, distributors

and customers across the globe. Autopal was the first company to manufacture the CFL

technology in India. It has continued to shape the group by breaking new grounds & pioneering

critical developments in automotive & lighting industry. The group extends its State-of-Art

technology, Avant-garde design in consumer durable goods like CFL, MHL, domestic use Fan

Series. Autopal forays wide products range of Energy saving lamps CFL, MHL, Down-lighters,

LED Series & Tube-light.

Lighting is our business, World is our market”

1.2 HISTORY

Autopal Industries Limited was promoted by Shri Dharam Pal Gupta and his brothers as an

energy saving lighting manufacturing industry. The Company become Public Limited in 15th

oct,1985 and started it’s commercial production on 27th April, 1992. The Company was first in

India to manufacture Compact Fluorescent Lamp (CFL) in India with Koren technology and also

manufactured automotive/domestic Halogen lamps & General lighting products.

The unit was established with installed capacity of 12.00 lacs nos. per annum unit of CFL and 30

lakh nos per annum unit of Automotive/Domestic Halogen Lamp. With its substantial investment

and effort in R&D, the company achieved various milstones, in terms of Patents and technology

awards.

1.2 VISION

Innovative and energy conscious solutions are our future. With Autopal’s significant and

sustained development in state of the art lighting technology and globally competitive



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manufacturing operations, supported by award winning product designers sales team and

engineers, Autopal Industries is confident of a progressive and environmentally conscious future.

Fig 1.1 Vision of Autolite (India) Limited

Whether your lighting design challenges are interior, exterior, industrial, and commercial or

architectural, we at Autopal are confident that we have the experience, service locations and

design solutions to meet your every need.

1.3 ACHIVEMENTS

Rajasthan State Export Award in 2010

Vendor Award from Lucas India Service in 2005

EEPC – Export Excellence Award in 2002

ACMA Technology Award in 1998

MARUTI SUZUKI Vendor Performance Award in 1998

ACMA Best Export Performance Award in 1997

State Award for Export Excellence in 1996



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National Productivity Award in 1995

Vishwakarma Award for Best Unit in 1995

ACMA Certificate of Merit in 1995

Vishwakarma Award for Highest Exporter in 1995




Govt. of India National Award ‘Certificate of Merit’ in 1992




Govt. of India National Award ‘Certificate of Merit’ in 1988

1.5 SERVICES

Avant-garde design in consumer durable goods like CFL, MHL

Domestic use Fan Series

Energy saving lamps

CFL

MHL

Downlighters

LED Series & Tubelight

Halogen Bulbs

LED Lamps

Head Lamps

Universal Head Lamps

Lamps for Trucks



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1.6 NETWORK

Fig 1.2 Network of Autolite (India) Limited

Autopal empoers its people to build sturdy & lasting relationship with its business partners,

employees & customers, thus paning the way for continuous growth throughout the nation.

Autopal empowers its people to build sturdy & lasting relationship with its business partners,

employees & customers, thus paning the way for continuous growth throughout the nation

Head Office & Works

Jaipur Address : E-195 (A), RIICO Industrial Area, Mansrovar, Jaipur (Raj) 302020

E-Mail : [email protected], [email protected]

Branch Office

Branch Address: B-Wing, Office No.1005, Express Zone Building, Western Express Highway

(Dindoshi Flyover) Malad (East), Mumbai-400063

E-Mail: [email protected], [email protected]

mailto:[email protected]


















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CHAPTER 2

LED

2.1 INTRODUCTION

A light-emitting diode (LED) is a semiconductor light source. LEDs are used as indicator lamps

in many devices and are increasingly used for general lighting. Appearing as practical electronic

components in 1962, early LEDs emitted low-intensity red light, but modern versions are

available across the visible, ultraviolet, and infrared wavelengths, with very high brightness.

When a light-emitting diode is switched on, electrons are able to recombine with holes within the

device, releasing energy in the form of photons. This effect is called electroluminescence, and the

color of the light (corresponding to the energy of the photon) is determined by the energy band

gap of the semiconductor. An LED is often small in area (less than 1 mm2), and integrated

optical components may be used to shape its radiation pattern. LEDs have many advantages over

incandescent light sources including lower energy consumption, longer lifetime, improved

physical robustness, smaller size, and faster switching. However, LEDs powerful enough for

room lighting are relatively expensive, and require more precise current and heat management

than compact fluorescent lamp sources of comparable output.

Light-emitting diodes are used in applications as diverse as aviation lighting, automotive lighting,

advertising, general lighting, and traffic signals. LEDs have allowed new text, video displays,

and sensors to be developed, while their high switching rates are also useful in advanced

communications technology. Infrared LEDs are also used in the remote control units of many

commercial products including televisions, DVD players and other domestic appliances. LEDs

are also used in seven-segment display.

2.2 LED DOWNLIGHTERS

A recessed light or downlight (also pot light in Canadian English, sometimes can light (for

canister

light) in American English) is a light fixture that is installed into a hollow opening in a ceiling.



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Fig 2.1 LED Downlighters

When installed it appears to have light shining from a hole in the ceiling, concentrating the light

in a downward direction as a broad floodlight or narrow spotlight. There are two parts to recessed

lights, the trim and housing. The trim is the visible portion of the light. It is the insert that is seen

when looking up into the fixture, and also includes the thin lining around the edge of the light.

The housing is the fixture itself that is installed inside the ceiling and contains the lamp holder.

TRIM STYLES

Recessed lighting styles have evolved with more manufacturers creating quality trims for a

variety of applications. You can find recessed lighting trim with the standard baffle in black or

white, which is the most popular. They are made to absorb extra light and create a crisparchitectural appearance. There are cone trims which produce a low-brightness aperture.

Multipliers are offered which are designed to control the omni-directional light from "A" style

incandescent light bulbs and compact fluorescents. Lens trim is designed to provide a diffused

light and protect the lamp. Lensed trims are normally found in wet locations.

The luminous trims combine the diffused quality of lensed trim but with an open down light

component. Adjustable trim allows for the adjustment of the light whether it is eyeball style,

which protrudes from the trim or gimbal ring style, which adjusts inside the recess. These lights



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allow for full versatility. Lastly, there are the wall-washer trims, which are designed to eliminate

the often seen "scalloped light effect".

LAMP STYLES

There are two types of lamps for recessed lighting: directional and diffuse. Directional lamps (R,

BR, PAR, MR) contain reflectors that direct and control the light. Diffuse lamps (A, S, PS, G)

control light distribution through their omni-directional light.

2.3 SURFACE LED

Surface Mount LEDs are cost-efficient solutions for low-power, compact designs. The products

come in a variety of available color, lens, and package types and are highly durable.

Surface Mount LEDs are smaller than leaded components, making them ideal for space-limited

board sizes and equipment. They are also highly resistant to shock and vibration and are available

in packages with a considerably higher number of pins than leaded LEDs.

The light weight of Surface Mount LEDs makes them optimal for mobile appliances. They are

also ideally suited for RF applications because of their low levels of parasitic inductance and

capacitance.

2.3.1 FEATURES

Low Power Consumption

Wide Viewing Angle

Variety of Available Colors, Lens and Package Types

High Reliability

Durable



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Fig 2.2 Surface LED

2.3.2 APPLICATIONS

LCD Backlighting

Pushbutton Backlighting

Keypad Backlighting

Automotive Interior Lighting

Symbol Indicators

Front Panel Indicators

Small Message Panel Signage

2.4 LEADED LEDs

Fig 2.3 Leaded LEDs



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Leaded LEDs, also called through-hole LEDs, have for many years played an integral role in

electronic designs. These LEDs are known for their ruggedness, long lifespan, and low power

consumption.

Leaded LEDs are available in a variety of package shapes and sizes and colors.

2.4.1 FEATURES


Highly Reliable

Range of Viewing Angles from Narrow to Wide

Long-Life Solid State Reliability

Rugged Design

Variety of Available Colors, Package Styles

2.4.2 APPLICATIONS

Outdoor LED panels,

Traffic Signals

Automotive Lighting

Instrumentation Indicators

Front Panel Indicators

Small Area Backlighting

2.5 ULTRAVOILET LEDs

Ultraviolet electromagnetic radiation, commonly known as UV, is currently employed in many

industries and applications. The emerging UV LEDs will be an enabling, competitive technology

that drives new and innovative applications. UV-LEDs have a long operating life and are more

environmentally friendly than traditional mercury UV lamps.



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Fig 2.4 Ultraviolet LED

2.5.1 APPLICATIONS

Industrial Curing

Fluorescence disclosing and verification

Air Purification

Medical and Biomedical Applications

Dermatological Equipment

Currency Validation

Forensics Equipment

Photo Polymerization

Spectroscopy

Dental Curing and Teeth Whitening

Sterilization and Medical

DNA Gel



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2.5.2 FEATURES


Low Current Requirement

Tight Tolerance of Wavelengths

Long Life

Environmentally Friendly

Fig 2.5 Electromagnetic Spectrum of LED

2.5.3 WARNINGS AND HANDLING INSTRUCTIONS

UV-LEDs emit invisible ultraviolet radiation when in operation, which may be harmful to eyes

or skin, even for brief periods. Do NOT look directly into the UV-LED during operation. Be sure

that you and all persons in the vicinity wear adequate " UV " Safety protection for eyes and skin.

If you incorporate a UV-LED into a product, be sure to provide WARNING labels.

2.6 FLOOD LIGHT

Floodlights are broad-beamed, high-intensity artificial lights often used to illuminate outdoor

playing fields while an outdoor sports event is being held during low-light conditions.



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Fig 2.6 Flood light in Football Stadium

In the top tiers of many professional sports, it is a requirement for stadiums to have floodlights to

allow games to be scheduled outside daylight hours. Evening or night matches may suit

spectators who have work or other commitment earlier in the day. The main motivation for this is

television marketing, especially in sports such as Gridiron which rely on TV rights money to

finance the sport. Some sports grounds which do not have permanent floodlights installed may

make use of portable temporary ones instead. Many larger floodlights (see bottom picture) will

have gantries for bulb changing and maintenance. These will usually be able to accommodate

one or two engineers.

2.6.1 TYPES OF FLOODLIGHT

The most common type of floodlight is the Metal Halide which emits a bright white light,

however most commonly used for sporting events are high pressure Sodium floodlights which

emit a soft orange light, similar to that of street lights; SON lamps have a very high lumens-to-

watt ratio making them a cost effective choice where certain lux levels have to be met.[citation

needed]



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In the recent years there have been new developments and the LED technology has come a long

way and now LED flood lights are bright enough to be used for illumination purposes on large

sport fields.

2.6.2 APPLICATIONS

Cricket

Association football

Rugby League

Racing

Baseball

Tennis



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CHAPTER 3

WORKING OF LED’S

A light emitting diode (LED) is known to be one of the best optoelectronic devices out of the lot.

The device is capable of emitting a fairly narrow bandwidth of visible or invisible light when its

internal diode junction attains a forward electric current or voltage. The visible lights that an

LED emits are usually orange, red, yellow, or green. The invisible light includes the infrared

light. The biggest advantage of this device is its high power to light conversion efficiency. That

is, the efficiency is almost 50 times greater than a simple tungsten lamp. The response time of the

LED is also known to be very fast in the range of 0.1 microseconds when compared with 100

milliseconds for a tungsten lamp. Due to these advantages, the device wide applications as visual

indicators and as dancing light displays.

We know that a P-N junction can connect the absorbed light energy into its proportional electric

current. The same process is reversed here. That is, the P-N junction emits light when energy is

applied on it. This phenomenon is generally called electroluminance, which can be defined as the

emission of light from a semi-conductor under the influence of an electric field. The charge

carriers recombine in a forward P-N junction as the electrons cross from the N-region and

recombine with the holes existing in the P-region. Free electrons are in the conduction band of

energy levels, while holes are in the valence energy band. Thus the energy level of the holes will

be lesser than the energy levels of the electrons. Some part of the energy must be dissipated in

order to recombine the electrons and the holes. This energy is emitted in the form of heat and

light.

The electrons dissipate energy in the form of heat for silicon and germanium diodes. But in

Galium- Arsenide-phosphorous (GaAsP) and Galium-phosphorous (GaP) semiconductors, the

electrons dissipate energy by emitting photons. If the semiconductor is translucent, the junction

becomes the source of light as it is emitted, thus becoming a light emitting diode (LED). But

when the junction is reverse biased no light will be produced by the LED, and, on the contrary

the device may also get damaged.

LEDs create light by electroluminescence in a semiconductor material. Electroluminescence is

the phenomenon of a material emitting light when electric current or an electric field is passed



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through it - this happens when electrons are sent through the material and fill electron holes. An

electron hole exists where an atom lacks electrons (negatively charged) and therefore has a

positive charge. Semiconductor materials like germanium or silicon can be "doped" to create and

control the number of electron holes. Doping is the adding of other elements to the

semiconductor material to change its properties. By doping a semiconductor you can make two

separate types of semiconductors in the same crystal. The boundary between the two types is

called a p-n junction. The junction only allows current to pass through it one way, this is why

they are used as diodes. LEDs are made using p-n junctions. As electrons pass through one

crystal to the other they fill electron holes. They emit photons (light).

Fig 3.1 A 5 Watt LED, one of the most powerful LEDs available

Phosphors are used to help filter the light output of the LED. They create a more pure "harsh"

color.

Engineers had to figure out how to control the angle the light escapes the semiconductor, this

"light cone" is very narrow. They figured out how to make light refract or bounce off all surfaces

of the

Semiconductor crystal to intensify the light output. This is why LED displays traditionally have

been best viewed from one angle.



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Fig 3.2 A laser also creates light, but through a different construction

Fig 3.3 Phosphors

3.1 LED CHARACTERISTICS

The forward bias Voltage-Current (V-I) curve and the output characteristics curve is shown in the

figure above. The V-I curve is practically applicable in burglar alarms. Forward bias of

approximately 1 volt is needed to give significant forward current. The second figure is used to

represent a radiant power-forward current curve. The output power produced is very small and

thus the efficiency in electrical-to-radiant energy conversion is very less.



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Fig 3.4 LED Characteristics

The figure below shows a series resistor Rseries connected to the LED. Once the forward bias of

the device exceeds, the current will increase at a greater rate in accordance to a small increase in

voltage. This shows that the forward resistance of the device is very low. This shows the

importance of using an external series current limiting resistor. Series resistance is determined by

the following equation.

Rseries = (Vsupply – V)/I

Vsupply – Supply Voltage

V – LED forward bias voltage

I – Current

The commercially used LED’s have a typical voltage drop between 1.5 Volt to 2.5 Volt or

current between 10 to 50 milliamperes. The exact voltage drop depends on the LED current,

colour, tolerance, and so on.

3.2 LED BASICS: HOW TO TELL WHICH LEAD IS POSITIVE OR

NEGATIVE

LED has two leads, one longer than the other,the longer lead is the postive (also known as the

anode) lead.



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If the LED has two leads with leads that are equal in length, you can look at the metal plate

inside the LED. The smaller plate indicates the positive (anode) lead; the larger plate belongs to

the negative (cathode) lead.

Fig 3.5 Surface Mount LED Fig 3.6 LED

LED has a flat area (on the plastic housing), the lead adjacent to the flat area is the negative

(cathode) lead.

It’s a little bit harder to determine the polarity with Surface Mount LEDS. Some are marked with

a (-) to indicate the negative lead, but often, they are not. The single best way to determine the

polarity is through the use a multimeter.

Set the multimeter to the diode/continuity setting. Usually, the multimeter will supply enough

current into the LED which will just barely light it up. The black (common) lead on the

multimeter indicates

3.3 ADVANTAGES & DISADVANTAGES

ADVANTAGES

Energy efficient source of light for short distances and small areas. The typical LED requires

only 30-60 milliwatts to operate



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Durable and shockproof unlike glass bulb lamp types

Directional nature is useful for some applications like reducing stray light pollution on

streetlights

Very low voltage and current are enough to drive the LED.

Voltage range – 1 to 2 volts.

Current – 5 to 20 milliamperes.

Total power output will be less than 150 milliwatts.

The response time is very less – only about 10 nanoseconds.

The device does not need any heating and warm up time.

Miniature in size and hence light weight.

Have a rugged construction and hence can withstand shock and vibrations.

An LED has a life span of more than 20 years.

DISADVANTAGES

May be unreliable in outside applications with great variations in summer/winter

temperatures, more work is being done now to solve this problem

Semiconductors are sensitive to being damaged by heat, so large heat sinks must be

employed to keep powerful arrays cool, sometimes a fan is required. This adds to cost and a

fan greatly reduces the energy efficient advantage of LEDs, it is also prone to failure which

leads to unit failure

Circuit board solder and thin copper connections crack when flexed and cause sections of

arrays to go out

Rare earth metals used in LEDs are subject to price control monopolies by certain nations

Reduced lumen output over time



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CHAPTER 4

LED MANUFACTURING

Light-emitting diodes (LEDs) — small colored lights available in any electronics store — are

ubiquitous in modern society. They are the indicator lights on our stereos, automobile

dashboards, and microwave ovens. Numeric displays on clock radios, digital watches, and

calculators are composed of bars of LEDs. LEDs also find applications in telecommunications

for short range optical signal transmission such as TV remote controls. They have even found

their way into jewelry and clothing — witness sun visors with a series of blinking colored lights

adorning the brim. The inventors of the LED had no idea of the revolutionary item they were

creating. They were trying to make lasers, but on the way they discovered a substitute for the

light bulb.

Light bulbs are really just wires attached to a source of energy. They emit light because the wire

heats up and gives off some of its heat energy in the form of light. An LED, on the other hand,

emits light by electronic excitation rather than heat generation. Diodes are electrical valves that

allow electrical current to flow in only one direction, just as a one-way valve might in a water

pipe. When the valve is "on," electrons move from a region of high electronic density to a region

of low electronic density. This movement of electrons is accompanied by the emission of light.

The more electrons that get passed across the boundary between layers, known as a junction, the

brighter the light. This phenomenon, known as electroluminescence, was observed as early as

1907. Before working LEDs could be made, however, cleaner and more efficient materials had to

be developed.

LEDs were developed during the post-World War II era; during the war there was a potent

interest in materials for light and microwave detectors. A variety of semiconductor materials

were developed during this research effort, and their light interaction properties were investigated

in some detail. During the 1950s, it became clear that the same materials that were used to detect

light could also be used to generate light. Researchers at AT&T Bell Laboratories were the first

to exploit the light-generating properties of these new materials in the 1960s. The LED was a

forerunner, and a fortuitous byproduct, of the laser development effort. The tiny colored lights



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held some interest for industry, because they had advantages over light bulbs of a similar size:

LEDs use less power, have longer lifetimes, produce little heat, and emit colored light.

The first LEDs were not as reliable or as useful as those sold today. Frequently, they could only

operate at the temperature of liquid nitrogen (-104 degrees Fahrenheit or -77 degrees Celsius) or

below, and would burn out in only a few hours. They gobbled power because they were very

inefficient, and they produced very little light. All of these problems can be attributed to a lack of

reliable techniques for producing the appropriate materials in the 1950s and 1960s, and as a result

the devices made from them were poor. When materials were improved, other advances in the

technology followed: methods for connecting the devices electronically, enlarging the diodes,

making them brighter, and generating more colors.

The advantages of the LED over the light bulb for applications requiring a small light source

encouraged manufacturers like Texas Instruments

To make the semiconductor wafers, gallium, arsenic, and/or phosphor are first mixed together in

a chamber and forced into a solution. To keep them from escaping into the pressurized gas in the

chamber, they are often covered with a layer of liquid boron oxide. Next, a rod is dipped into the

solution and pulled out slowly. The solution cools and crystallizes on the end of the rod as it is

lifted out of the chamber, forming a long, cylindrical crystal ingot. The ingot is then sliced into

wafers.






wafers.

and Hewlett Packard to pursue the commercial manufacture of LEDs. Sudden widespread market

acceptance in the 1970s was the result of the reduction in production costs and also of clever

marketing, which made products with LED displays (such as watches) seem "high tech" and,

therefore, desirable. Manufacturers were able to produce many LEDs in a row to create a variety

of displays for use on clocks, scientific instruments, and computer card readers. The technology

is still developing today as manufacturers seek ways to make the devices more efficiently, less

expensively, and in more colors.



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Fig 4.1 Making semiconductor wafers






wafers.

and Hewlett Packard to pursue the commercial manufacture of LEDs. Sudden widespread market

acceptance in the 1970s was the result of the reduction in production costs and also of clever

marketing, which made products with LED displays (such as watches) seem "high tech" and,

therefore, desirable. Manufacturers were able to produce many LEDs in a row to create a variety

of displays for use on clocks, scientific instruments, and computer card readers. The technology

is still developing today as manufacturers seek ways to make the devices more efficiently, less

expensively, and in more colors.

4.1 RAW MATERIALS

Diodes, in general, are made of very thin layers of semiconductor material; one layer will have an

excess of electrons, while the next will have a deficit of electrons. This difference causes

electrons to move from one layer to another, thereby generating light. Manufacturers can now

make these layers as thin as .5 micron or less (1 micron = 1 ten-thousandth of an inch).



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Fig 4.2 Adding Epitaxial Layers

Impurities within the semiconductor are used to create the required electron density. A

semiconductor is a crystalline material that conducts electricity only when there is a high density

of impurities in it. The slice, or wafer, of semiconductor is a single uniform crystal, and the

impurities are introduced later during the manufacturing process. Think of the wafer as a cake

that is mixed and baked in a prescribed manner, and impurities as nuts suspended in the cake.

The particular semiconductors used for LED manufacture are gallium arsenide (GaAs), gallium

phosphide (GaP), or gallium arsenide phosphide (GaAsP). The different semiconductor materials

(called substrates) and different impurities result in different colors of light from the LED.

Impurities, the nuts in the cake, are introduced later in the manufacturing process; unlike

imperfections, they are introduced deliberately to make the LED function correctly. This process

is called doping. The impurities commonly added are zinc or nitrogen, but silicon, germanium,

and tellurium have also been used. As mentioned previously, they will cause the semiconductor

to conduct electricity and will make the LED function as an electronic device. It is through the

impurities that a layer with an excess or a deficit of electrons can be created.



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To complete the device, it is necessary to bring electricity to it and from it. Thus, wires must be

attached onto the substrate. These wires must stick well to the semiconductor and be strong

enough to withstand subsequent

One way to add the necessary impurities to the semiconductor crystal is to grow additional layers

of crystal onto the wafer surface. In this process, known as "Liquid Phase Epitaxy," the wafer is

put on a graphite slide and passed underneath reservoirs of molten GaAsP.

Contact patterns are exposed on the wafer's surface using photoresist, after which the wafers are

put into a heated vacuum chamber. Here, molten metal is evaporated onto the contact pattern on

the wafer surface. Processing such as soldering and heating. Gold and silver compounds are most

commonly used for this purpose, because they form a chemical bond with the gallium at the

surface of the wafer.

LEDs are encased in transparent plastic, rather like the lucite paperweights that have objects

suspended in them. The plastic can be any of a number of varieties, and its exact optical

properties will determine what the output of the LED looks like. Some plastics are diffusive,

which means the light will scatter in many directions. Some are transparent, and can be shaped

into lenses that will direct the light straight out from the LED in a narrow beam. The plastics can

be tinted, which will change the color of the LED by allowing more or less of light of a particular

color to pass through.

4.2 DESIGN

Several features of the LED need to be considered in its design, since it is both an electronic and

an optic device. Desirable optical properties such as color, brightness, and efficiency must be

optimized without an unreasonable electrical or physical design. These properties are affected by

the size of the diode, the exact semiconductor materials used to make it, the thickness of the

diode layers, and the type and amount of impurities used to "dope" the semiconductor.



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4.3 THE MANUFACTURING PROCESS

4.3.1 MAKING SEMICONDUCTOR WAFERS

First, a semiconductor wafer is made. The particular material composition — GaAs, GaP, or

something in between — is determined by the color of LED being fabricated. The crystalline

semiconductor is grown in a high temperature, high pressure chamber. Gallium, arsenic,

and/or phosphor are purified and mixed together in the chamber. The heat and pressure

liquify and press the components together so that they are forced into a solution. To keep

them from escaping into the pressurized gas in the chamber, they are often covered with a

layer of liquid boron oxide, which seals them off so that they must "stick together." This is

known as liquid encapsulation, or the Czochralski crystal growth method. After the elements

are mixed in a uniform solution, a rod is dipped into the solution and pulled out slowly. The

solution cools and crystallizes on the end of the rod as it is lifted out of the chamber, forming

a long, cylindrical crystal ingot (or boule) of GaAs, GaP, or GaAsP. Think of this as baking

the cake.

The boule is then sliced into very thin wafers of semiconductor, approximately 10 mils thick,

or about as thick as a garbage bag. The wafers are polished until the surfaces are verysmooth, so that they will readily accept more layers of semiconductor on their surface. The

principle is similar to sanding a table before painting it. Each wafer should be a single crystal

of material of uniform composition. Unfortunately, there will sometimes be imperfections in

the crystals that make the LED function poorly. Think of imperfections as unmixed bits of

flower or sugar suspended in the cake during baking. Imperfections can also result from the

polishing process; such imperfections also degrade device performance. The more

imperfections, the less the wafer behaves like a single crystal; without a regular crystalline

structure, the material will not function as a semiconductor.

Next, the wafers are cleaned through a rigorous chemical and ultrasonic process using various

solvents. This process removes dirt, dust, or organic matter that may have settled on the

polished wafer surface. The cleaner the processing, the better the resulting LED will be.

4.3.2 ADDING EPITAXIAL LAYERS



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Additional layers of semiconductor crystal are grown on the surface of the wafer, like adding

more layers to the cake. This is one way to add impurities, or dopants, to the crystal. The

crystal layers are grown this time by a process called Liquid Phase Epitaxy (LPE). In this

technique, epitaxial layers — semiconductor layers that have the same crystalline orientation

as the substrate below — are deposited on a wafer while it is drawn under reservoirs of molten

GaAsP. The reservoirs have appropriate dopants mixed through them. The wafer rests on a

graphite slide, which is pushed through a channel under a container holding the molten liquid

(or melt, as it is called). Different dopants can be added in sequential melts, or several in the

same melt, creating layers of material with different electronic densities. The deposited layers

will become a continuation of the wafer's crystal structure.

LPE creates an exceptionally uniform layer of material, which makes it a preferred growth

and doping technique. The layers formed are several microns thick.

After depositing epitaxial layers, it may be necessary to add additional dopants to alter the

characteristics of the diode for color or efficiency. If additional doping is done, the wafer is

again placed in a high temperature furnace tube, where it is immersed in a gaseous

atmosphere containing the dopants — nitrogen or zinc ammonium are the most common.

Nitrogen is often added to the top layer of the diode to make the light more yellow or green.

4.3.3 ADDING METAL CONTACTS

Metal contacts are then defined on the wafer. The contact pattern is determined in the design

stage and depends on whether the diodes are to be used singly or in combination. Contact

patterns are reproduced in photoresist, a light-sensitive compound; the liquid resist is deposited in

drops while the wafer spins, distributing it over the surface. The resist is hardened by a brief, low

temperature baking (about 215 degrees Fahrenheit or 100 degrees Celsius). Next, the master

pattern, or mask, is duplicated on the photoresist by placing it over the wafer and exposing the

resist with ultraviolet light (the same way a photograph is made from a negative). Exposed areas

of the resist are washed away with developer, and unexposed areas remain, covering the

semiconductor layers.

Contact metal is now evaporated onto the pattern, filling in the exposed areas. Evaporation takes

place in another high temperature chamber, this time vacuum sealed. A chunk of metal is heated

to temperatures that cause it to vaporize. It condenses and sticks to the exposed semiconductor

wafer, much like steam will fog a cold window. The photoresist can then be washed away with



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acetone, leaving only the metal contacts behind. Depending on the final mounting scheme for the

LED, an additional layer of metal may be evaporated on the back side of the wafer. Any

deposited metal must undergo an annealing process, in which the wafer is heated to several

hundred degrees and allowed to remain in a furnace (with an inert atmosphere of hydrogen or

nitrogen flowing through it) for periods up to several hours. During this time, the metal and the

semiconductor bond together chemically so the contacts don't flake off.

A single 2 inch-diameter wafer produced in this manner will have the same pattern repeated up to

6000 times on it; this gives an indication of the size of the finished diodes. The diodes are cut

apart either by cleaving (snapping the wafer along a crystal plane) or by sawing with a diamond

saw. Each small segment cut from the wafer is called a die. A difficult and error prone process,

cutting results in far less than 6000 total useable LEDs and is one of the biggest challenges in

limiting production costs of semiconductor devices.

4.3.4 MOUNTING AND PACKAGING

Fig 4.3 Mounting and Packaging of LED

Individual dies are mounted on the appropriate package. If the diode will be used by itself as

an indicator light or for jewelry, for example, it is mounted on two metal leads about two

inches long. Usually, in this case, the back of the wafer is coated with metal and forms an



28

electrical contact with the lead it rests on. A tiny gold wire is soldered to the other lead and

wire-bonded to the patterned contacts on the surface of the die. In wire bonding, the end of

the wire is pressed down on the contact metal with a very fine needle. The gold is soft enough

to deform and stick to a like metal surface.

Finally, the entire assembly is sealed in plastic. The wires and die are suspended inside a

mold that is shaped according

A typical LED indicator light shows how small the actual LED is. Although the average

lifetime of a small light bulb is 5-10 years, a modern LED should last 100 years or more

before it fails

Optical requirements of the package (with a lens or connector at the end), and the mold is

filled with liquid plastic or epoxy. The epoxy is cured, and the package is complete.



29

CHAPTER 5

ASSEMBLING OF LED LIGHTS

5.1 DRIVER ASSEMBLY

Fig 5.1 Driver Assembly

Driver assembly is the department where the LED’s are mounted on PCB’s using Surface Mount

Technology. The complete work in done by machine.

5.1.1 SURFACE MOUNT TECHNOLOGY



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Surface-mount technology (SMT) is a method for producing electronic circuits in which the

components are mounted or placed directly onto the surface of printed circuit boards (PCBs). The

Assembly line with SMT placement machine is shown in the fig 5.2 and 5.3 show the LED strips

which are mounted on the PCBs. An electronic device so made is called a surface-mount device

(SMD). In the industry it has largely replaced the through-hole technology construction method

of fitting components with wire leads into holes in the circuit board.

Fig 5.2 Assembly line with SMT placement machine



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Fig 5.3 LED Strips

Both technologies can be used on the same board for components not suited to surface mounting

such as large transformers and heat-sinked power semiconductors.

An SMT component is usually smaller than its through-hole counterpart because it has either

smaller leads or no leads at all. It may have short pins or leads of various styles, flat contacts, a

matrix of solder balls (BGAs), or terminations on the body of the component.

Because "surface-mount" refers to a methodology of manufacturing, there are different terms

used when referring to the different aspect of the method, which distinguishes for example the

components, technique, and machines used in manufacturing.

These terms are listed in the following table

SMp term Expanded form

SMD Surface-mount devices (active, passive and electromechanical components)

SMT Surface-mount technology (assembling and mounting technology)

SMA Surface-mount assembly (module assembled with SMT)

SMC Surface-mount components (components for SMT)SMP Surface-mount packages (SMD case forms)



32

SME Surface-mount equipment (SMT assembling machines)

Fig 5.4 Removal of surface-mount device using soldering tweezers

ADVANTAGES

The main advantages of SMT over the older through-hole technique are:

Smaller components. As of 2012 smallest was 0.4 × 0.2 mm (0.016 × 0.008 in: 01005).

Expected to sample in 2013 are 0.25 × 0.125 mm (0.010 × 0.005 in, size not yet standardized)

Much higher component density (components per unit area) and many more connections per

component.

Lower initial cost and time of setting up for production.

Fewer holes need to be drilled.

Simpler and faster automated assembly. Some placement machines are capable of placing

more than 136,000 components per hour.

Small errors in component placement are corrected automatically as the surface tension of

molten solder pulls components into alignment with solder pads.

Components can be placed on both sides of the circuit board.

Lower resistance and inductance at the connection; consequently, fewer unwanted RF signal

effects and better and more predictable high-frequency performance.

Better mechanical performance under shake and vibration conditions.

Many SMT parts cost less than equivalent through-hole parts.



33

Better EMC compatibility (lower radiated emissions) due to the smaller radiation loop area

(because of the smaller package) and the smaller lead inductance.

DISADVANTAGES

Manual prototype assembly or component-level repair is more difficult and requires skilled

operators and more expensive tools, due to the small sizes and lead spacings of many SMDs.

SMDs cannot be used directly with plug-in breadboards (a quick snap-and-play prototyping

tool), requiring either a custom PCB for every prototype or the mounting of the SMD upon a

pin-leaded carrier. For prototyping around a specific SMD component, a less-expensive

breakout board may be used. Additionally, stripboard style protoboards can be used, some of

which include pads for standard sized SMD components. For prototyping, "dead bug"

breadboarding can be used.

SMDs' solder connections may be damaged by potting compounds going through thermal

cycling.

Solder joint dimensions in SMT quickly become much smaller as advances are made toward

ultra-fine pitch technology. The reliability of solder joints become more of a concern, as less

and less solder is allowed for each joint. Voiding is a fault commonly associated with solder

joints, especially when reflowing a solder paste in the SMT application. The presence of

voids can deteriorate the joint strength and eventually lead to joint failure.[5][6]

SMT is unsuitable for large, high-power, or high-voltage parts, for example in power

circuitry. It is common to combine SMT and through-hole construction, with transformers,

heat-sinked power semiconductors, physically large capacitors, fuses, connectors, and so on

mounted on one side of the PCB through holes.

SMT is unsuitable as the sole attachment method for components that are subject to frequent

mechanical stress, such as connectors that are used to interface with external devices that are

frequently attached and detached.



34

CHAPTER 6

MANUAL ASSEMBLY OF LED LIGHTS

6.1 FRAME MOUNTING

Best way to accurately position strip, once you have decided where to mount it, is to draw or

scratch a guide line that you can follow with one edge of the LED strip, this will minimize

handling and over working the delicate flexible PC board.

Attach the LED Strip using the adhesive back to hold it in place before applying the 1” wide

fibreglass ribbon which runs along the length of the LED strip. Prepare surfaces with a solvent

that evaporates quickly but first, make sure it doesn't attack your existing finishes.

Leave the end contacts exposed for final connecting and sealing.



35

Masking off the area where the strip will adhere and then painting or spraying contact cement on

will give an exceptional bond when combined with the strip’s adhesive. Take care however,

because repositioning will be a problem once it grabs.

When applying the LED strip - first, peel the backing paper back about 2 inches and press the

strip into place, next, put a bit of tension on the LED strip holding it about a foot from the

adhesion point while applying it and peeling back the paper backing, 2-4 inches at a time, apply

good pressure with a finger every 1/2 inch or so. Make sure the adhesive has grabbed, this will

assure an even line of LEDs and provides the best heat transfer, which will help extend their

performance.

Never just peel the LED strip off once it has bonded to a surface, instead use a thin scraper or

dull blade and slide it between the bonded surfaces while lifting the LED strip away and

minimize distorting it.

When applying the fibreglass, the best results can be had by brushing the resin onto the strip/pipe

area before applying the fibreglass then brushing another coat over the ribbon once it’s been

applied. A small 1/2" disposable paint brush works well to dab out any air bubbles and ensure

good fibreglass contact over the LEDs.

6.2 SOLDERING

Soldering is a process in which two or more metal items are joined together by melting and

flowing a filler metal (solder) into the joint, the filler metal having a lower melting point than the

adjoining metal. Soldering differs from welding in that soldering does not involve melting the

work pieces. In brazing, the filler metal melts at a higher temperature, but the work piece metal

does not melt. In the past, nearly all solders contained lead, but environmental concerns have

increasingly dictated use of lead-free alloys for electronics and plumbing purposes.

LED strips have two common features which are important to this Instructable. First, LED strips

are divided into segments. The strips can be cut at any length provided the cut is on the line

usually indicated by a small scissors icon. LED strips that are severed or cut between these lines

will not function to the fullest. Second, LED strips have a positive (+) and a negative (-)

soldering hard point that is on the strip. The convention does matter, since they run from DC

power. There are a pair of these points at the beginning and the end of each segment.



36

Step 1: Cut the LED strip along an indicated line to give you a length close to the desired length.

If you cut too long, you can always cut again, too short and you may have to do more soldering.

Step 2: Remove the waterproofing or plastic covering, if applicable, so that the soldering hard

points are free.

Step 3: Pre-tin the hard points. Pre-tinning refers to the procedure by which you solder a small

blob of solder onto the object in question. In order for this to work the best, you must heat up the

element so that the solder wicks onto it...not just lays on top and cools. This works best with a

conical soldering tip and a small amount of solder for thermal conductivity. Once the desired

temperature is reached, you will see the solder wick onto the surface. Add more in necessary.

You should have enough to cover the hard point, but not be at risk of melting through the strip or

reaching the other hard point, causing a short.



37

Fig 6.1 Soldering of LEDs

Step 4: Cut and strip the wire a desired length. Again, cut longer than you think you will need.

Strip only a small length of wire, like 1/8" or less. If the wire is stranded, twist the strands

together to keep them from separating. The best wire will be thin enough to move around tightly,

I prefer 22-24 AWG solid core.

A quick word about current. LED strips sink current and depending on the length increase the

amperage of current in the circuit. Wires can extend the reach of your LED strips and do not

count towards the drawn current (measured in amperes, A or milliamperes, mA). Please refer to

the manufacturer's documentation for the specifics. Most segments take somewhere between 20

and 100 mA. For example, my five foot section from the hardware store totals 250mA...which is

1/4 of the total my DC adapter puts out, which is 1A or 1000mA.

Step 5: Pre-tin the end of the wire.

Step 6: Using helping hands or a vice, mount the wire and the strip so that it takes minimal or no

effort to get the wire and the hard point to touch.

Step 7: Quickly touch the soldering iron to the wire and the hard point at the same time. If we

pre-tinned our connections, they should quickly form a solid contact. Remove from heat.

6.3 LEAD CUTTINGS



38

Fig 6.2 LED Components Lead Cutting Machine

6.3.1 LED COMPONENTS LEAD CUTTING MACHINE

Size L1100 * W650 * H1050mm

Voltage 220V/50-60Hz

Feeding forms Feeding plane



39

Weight 145kg

Processing 150(pcs/min)

Efficiency 80-150pcs/min

Feet long 3-20 (mm)

Package Wooden case

Type

Led Components Lead

Cutting Machine

Suit for bulk components cut work, suit for mass production, save manual labour

Special cutting method, blade imported from Japan, long service life and easy adjusted

High cutting accuracy, the shortest cutting length is 3 mm or 2.5 mm (Customer-made)

Feed table adopt imported fiber board

Feed table can be set according to the customer order, can install another counter according to

the customer requirements and the products

In order to guarantee the customers are able fully to operate the machine, if the customer need,

we can help customer training, includes:

Correct operating mode

Correct maintenance way

6.4 TESTING



40

Fig 6.3 Manufacturing and Testing of LEDs

LEDs cannot be manufactured with consistent optical properties as a result of the production

processes involved. Brightness and color can vary substantially from component to component

even in the same production batch. This is why LEDs have to be tested during production and in

their final application. Comprehensive optical characterization is also essential during research

and development of LEDs and for LED-based products.



41

Instrument Systems has developed turnkey solutions for determining luminous intensity,

luminous flux, color, spectrum and spatial radiation pattern of LEDs. The measurement systems

generate very accurate results with reliable reproducibility.

Quality in semiconductor manufacturing takes two forms. The first concern is with the final

produced product, and the second with the manufacturing facility. Every LED is checked when it

is wire bonded for operation characteristics.

Specific levels of current should produce specific brightness.

Exact light color is tested for each batch of wafers, and

Some LEDs will be pulled for stress testing, including lifetime tests, heat and power

breakdown, and mechanical damage.



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CHAPTER 7

CONCLUSION

Working with Autolite (India) Limited as a summer trainee was a very nice experience. I learnt a

lot about basics of LEDs and LED manufacturing. I also practiced what I learnt in the university

and applied it on field. Working with department enhanced my major understanding. In addition,

I gained a good experience in term of self-confidence, real life working situation, interactions

among people in the same field and working with others with different professional background.

I had an interest in understanding basic engineering work and practicing what has been learnt in

the class. Also, the training was an opportunity for me to increase my human relation both

socially and professionally.

I have learned about the working culture

During the training we gets to know about amount of hard work goes behind the making of a

products.

During the training one gets to know amount of hard work goes behind the making of a

product

This experience gives us a direction and prepares us to get ready before a getting into a

proper job.



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CHAPTER 8

LEARNINGS AND OUTCOMES

LED technology is used in Auto motive headlamps, signal lamps and for work lamps. The

production is done by Machines and Manual. Reflow oven and Reflow soldering are used for in

the manufacturing process of LEDs. During the training one gets to know amount of hard work

goes behind the making of a product. I got to learn about the working culture of the company and

how punctuality is important in making of a product.

I have learned about the different types of LED lights

According to their rating we learned about the applications of the lights

The manufacturing process of LED lights

I have learned about Surface Mount technology



REFERENCES

Books

[1.] Bergh, A. A. and P. J Dean. Light-Emitting Diodes. Clarendon Press, 1976

[2.] Gillessen, Klaus. Light-Emitting Diodes: An Introduction. Prentice Hall, 1987

[3.] Optoelectronics/Fiber-Optics Applications Manual. McGraw-Hill, 1981

[4.] Understanding Solid State Electronics. Radio Shack/Texas Instruments Learning Center,

1978

[5.] Williams, E. W. and R. Hall. Luminescence and the Light-Emitting Diode. Pergamon Press,1978

Websites

[1.] http://www.circuitstoday.com/how-a-led-works-light-emitting-diode-working

[2.] http://electronics.howstuffworks.com/led4.htm

[3.] http://www.edisontechcenter.org/LED.html

[4.] http://www.westfloridacomponents.com/blog/led-basics-how-to-tell-which-lead-is-positive-

or-negative/

[5.] http://www.madehow.com/Volume-1/Light-Emitting-Diode-LED.html

http://www.circuitstoday.com/how-a-led-works-light-emitting-diode-working



http://electronics.howstuffworks.com/led4.htm



http://www.edisontechcenter.org/LED.html



http://www.westfloridacomponents.com/blog/led-basics-how-to-tell-which-lead-is-positive-or-negative/



http://www.madehow.com/Volume-1/Light-Emitting-Diode-LED.html









7.autopal training report material

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