WAVE SOLDERING

A SUMMER TRAINING REPORT

Submitted by

MANJEET

Enrollment Number : 07814802813

in partial fulfillment of Summer Internship for the award of the degree

of

BACHELOR OF TECHNOLOGYIN

ELECTRONICS AND COMMUNICATION ENGINEERING

MAHARAJA AGRASEN INSTITUTE OF TECHNOLOGY

Guru Gobind Singh Indraprastha University, Delhi

2013-2017

Maharaja Agrasen Institute of Technology

To Whom It May Concern

I, Manjeet, Enrollment No. 07814802813, a student of Bachelors of Technology (ECE), a class

of 2013-17, Maharaja Agrasen Institute of Technology, Delhi hereby declare that the Summer

Training project report entitled “Wave Soldering” is an original work and the same has not been

submitted to any other Institute for the award of any other degree.

Date: 01/08/2016

Place: New Delhi

MANJEET

Enrollment No: 07814802813

Electronics and Communication Engineering

7E123

ACKNOWLEDGEMENT

I am highly grateful to Bharat Electronics Limited, Kotdwara, one of the leading defense

organizations of the nation, for providing me an opportunity to undertake six weeks training at

their manufacturing premises at Kotdwara, Uttarakhand.

It was a great learning experience as I was introduced to various aspects of the working of the

organization, the latest state of the art technologies & machines used in the manufacturing

processes. It was wonderful to see the company striving hard to keep up the national security at

par with the rest of the world. I would like to express my sincerest gratitude towards Mr. Sunil

Srivastava (Sr. Engineer, Human Resource and Development) and Mr. Mohd. Shahid Sami

(Manager) for their regular support and guidance that helped me in successful completion of my

six weeks training. At the end I would like to thank all the staff members of BEL, Kotdwara who

made this training a rich learning experience.

Manjeet

Enrollment Number: 07814802813

7E123/E3

PREFACE

With the ongoing revolution in electronic & communication where innovations are taking at the

blink of eye, it is impossible to keep the pace with the emerging trends. Excellence is an attitude

that whole of human race is born with. It is the environment that makes sure that whether the

result of this attitude is visible or otherwise. A well planned, properly executed and evaluated

industrial training helps a lot in including a professional attitude. It provides a linkage b/w the

student and industry to develop an awareness of industrial approach to problem solving, based on

broad understanding of process and mode of operation of organization.

During this period, the student gets the real experience for working in the actual industry

environment. Most of the theoretical knowledge that has been gained during the course of their

studies is put to test here. Apart from this the student gets an opportunity to learn the latest

technology, which is immensely helps in them in building their carrier.

I had the opportunity to have a real experience on many ventures, which increased my sphere of

knowledge to great extent. I got a chance to learn many new technologies and was also

interfaced to many instruments.

And all this credit goes to organization Bharat Electronics Ltd.

S.No. Chapter Page Number

List of Figures and Photographs 01

List of Tables 02

1. Introduction 03

2. Company Profile 04

3. Manufacturing Units 07

4. Wave Soldering 11

4.1 Introduction 11

4.2 Wave Soldering Process 12

4.2.1 Fluxing 12

4.2.2 Isopropyl Alcohol (IPA) 14

4.2.3 Pre-Heating 15

4.2.4 Solder Bath/Pot 19

4.2.5 Solder Wave Zone 19

4.2.6 Hot Air Debridging 22

4.2.7 Cooling Zone 22

5. Wave Soldering Machines 24

6. Conclusion 27

7. References 28

TABLE OF CONTENTS

LIST OF FIGURES AND PHOTOGRAPHS

1

S.No. Figure No. Figure Description Page Number

01 Fig.1 Manufacturing Units 08

02 Fig.2 PCB Tray Movement 13

03 Fig.3 Flux Nozzle 13

04 Fig.4 Reservior Tank 14

05 Fig.5 IPA Reservior 15

06 Fig.6 Conveyor 15

07 Fig.7 Wave Soldering (Through Hole Only) 18

08 Fig.8 Reflow Profile (Surface Mount Only) 18

09 Fig.9 Solder Bath/Pot 19

10 Fig.10 Solder Wave Zone 21

11 Fig.11 A simple wave soldering machine 24

12 Fig.12 A new and fully automated wave soldering machine. 25

13 Fig.13 Wave Soldering machine(Automated Lead Free) operated by a operator 25

14 Fig.14 14 Internal Structure and different zones of Wave Soldering machine. 26

LIST OF TABLES

S.No. Table Description Page Number

01

Manufacturing Units 07

CHAPTER 1

2

INTRODUCTION

1.1 INTRODUCTION

With the ongoing revolution in the field of electronics & communications where innovations are

taking place at the blink of an eye, it is impossible to keep the pace with the emerging trends.

Excellence is an attitude that whole of human race is born with. It is the environment that makes

sure that whether the result of this attitude is visible or otherwise. A well planned, properly

executed and evaluated industrial training helps a lot in including a professional attitude. It

provides a linkage between the student and industry to develop an awareness of industrial

approach to problem solving, based on broad understanding of process and mode of operation of

organization.

During this period, the student gets the real experience for working in the actual industry

environment. Most of the theoretical knowledge that has been gained during the course of their

studies is put to test here. Apart from this the student gets an opportunity to learn the latest

technology, which is immensely helps in them in building their carrier. I had the opportunity to

have a real experience on many ventures, which increased my sphere of knowledge to great

extent. I got a chance to learn many new technologies and was also interfaced to many

instruments.

The word quality holds out different meaning for different people, but for an industry it is most

important and can be defined as ―The totality of features and characteristics of a product /

services that bear on its ability to satisfy given needs.

And all the credit goes to organization Bharat Electronics Ltd.

CHAPTER 2

3

COMPANY PROFILE

2.1 COMPANY PROFILE

Bharat Electronics Limited (BEL) is a state-owned electronics company with about nine

factories, and few regional offices in India. It is owned by the Indian Government & primarily

manufactures advanced electronic products for the Indian Armed Forces.BEL is one of the eight

PSUs under Ministry of Defence, Government Of India. It has even earned the government's

Navratna status.

Bharat Electronics Limited (BEL) was set up at Bangalore, India, by the Government of India

under the Ministry of Defence in 1954 to meet the specialised electronic needs of the Indian

defence services. Over the years, it has grown into a multi-product, multi-technology, multi-unit

company serving the needs of customers in diverse fields in India and abroad . BEL is among an

elite group of public sector undertakings which have been conferred the Navratna status by the

Government of India.

The growth and diversification of BEL over the years mirrors the advances in the electronics

technology, with which BEL has kept pace. Starting with the manufacture of a few

communication equipment in 1956, BEL went on to produce Receiving Valves in 1961,

Germanium Semiconductors in 1962 and Radio Transmitters for AIR in 1964. In 1966, BEL set

up a Radar manufacturing facility for the Army and in-house R&D, which has been nurtured

over the years. Manufacture of Transmitting Tubes, Silicon Devices and Integrated Circuits

started in 1967. The PCB manufacturing facility was established in 1968. In 1970, manufacture

of Black & White TV Picture Tube, X-ray Tube and Microwave Tubes started. The following

year, facilities for manufacture of Integrated Circuits and Hybrid Micro Circuits were set up.

1972 saw BEL manufacturing TV Transmitters for Doordarshan. The following year,

manufacture of Frigate Radars for the Navy began. Under the government's policy of

decentralization and due to strategic reasons, BEL ventured to set up new Units at various

places. The second Unit of BEL was set up at Ghaziabad in 1974 to manufacture Radars and

Tropo communication equipment for the Indian Air Force. The third Unit was established at

Pune in 1979 to manufacture Image Converter and Image Intensifier Tubes. In 1980, BEL's first

4

overseas office was set up at New York for procurement of components and materials.

In 1981, a manufacturing facility for Magnesium Manganese Dioxide batteries was set up at the

Pune Unit. The Space Electronic Division was set up at Bangalore to support the satellite

programme in 1982. The same year saw BEL achieve a turnover of Rs.100 crores. In 1983, an

ailing Andhra Scientific Company (ASCO) was taken over by BEL as the fourth manufacturing

Unit at Machilipatnam. In 1985, the fifth Unit was set up in Chennai for supply of Tank

Electronics, with proximity to HVF, Avadi. The sixth Unit was set up at Panchkula the same

year to manufacture Military Communication equipment. 1985 also saw BEL manufacturing on

a large scale Low Power TV Transmitters and TVROs for the expansion of Doordarshan's

coverage.

1986 witnessed the setting up of the seventh Unit at Kotdwara to manufacture Switching

Equipment, the eighth Unit to manufacture TV Glass Shell at Taloja (Navi Mumbai) and the

ninth Unit at Hyderabad to manufacture Electronic Warfare Equipment. In 1987, a separate

Naval Equipment Division was set up at Bangalore to give greater focus to Naval projects. The

first Central Research Laboratory was established at Bangalore in 1988 to focus on futuristic

R&D. 1989 saw the manufacture of Telecom Switching and Transmission Systems as also the

setting up of the Mass Manufacturing Facility in Bangalore and the manufacture of the first batch

of 75,000 Electronic Voting Machines.

The agreement for setting up BEL's first Joint Venture Company, BE DELFT, with M/s Delft of

Holland was signed in 1990. Recently this became a subsidiary of BEL with the exit of the

foreign partner and has been renamed BEL Optronic Devices Limited. The second Central

Research Laboratory was established at Ghaziabad in 1992. The first disinvestment (20%) and

listing of the Company's shares in Bangalore and Mumbai Stock Exchanges took place the same

year. BEL Units obtained ISO 9000 certification in 1993-94. The second disinvestment (4.14%)

took place in 1994. In 1996, BEL achieved Rs.1,000 crores turnover.

In 1997, GE BEL, the Joint Venture Company with M/s GE, USA, was formed. In 1998, BEL

set up its second overseas office at Singapore to source components from South East Asia. The

year 2000 saw the Bangalore Unit, which had grown very large, being reorganized into Strategic

Business Units (SBUs). There are seven SBUs in Bangalore Unit. The same year, BEL shares

5

were listed in the National Stock Exchange. In 2002, BEL became the first defence PSU to get

operational Mini Ratna Category I status. In June 2007, BEL was conferred the prestigious

Navratna status based on its consistent performance.

CHAPTER 3

6

MANUFACTURING UNITS

3.1 MANUFACTURING UNITS

BEL has a total of nine manufacturing complexes spread throughout the nation with Banglore

being the biggest of them. The details about the different manufacturing units of BEL along

with their product specialities are a s follows:-

Sr. No. COMPLEX STATE

1. Ghaziabad Uttar Pradesh

2. Panchkula Haryana

3. Navi Mumabi Maharashtra

4. Kotdwara Uttaranchal

5. Pune Maharashtra

6. Hyderabad Andhra Pradesh

7. Banglore Karnatka

8. Machlipatnam Andhra Pradesh

9. Chennai Tamilnadu

Table 1 : Manufacturing Units

7

Fig. 1: Manufacturing Units

In 1954 with a factory of Jallahali, Bharat Electronics grew into nine units, spread all over India.

The locations & products of the units are given below:-

1. BANGALORE: This is also called BG Complex. Jallahali unit which is the mother unit is

now a part of the BG Complex. This is the biggest unit with approx. 10,000 employees

working here. Among the products here, the important ones are:

Communication equipment

Air & Doordarshan equipment like mobile van for live telecast etc.

Radar-mobile, one dimensional, 3-dimensional & multi-dimensional Radars are

manufactured here. Different range of semi-conductor devices like ICs.

Resistors & black & white color TV picture tube glasses.

8

ISRO‘s requirements are met at space electronics department at Bangalore. Satellite

launch vehicle was also manufactured here.

2. GHAZIABAD: This is the second unit which was set up in 1974, & approx. 2500

employees working here. Radars & some communication equipment are The products

manufactured here are:

Radars

SATCOM

Microwave components

3. PUNE: To diversify further one more branch was added 1979 & this was in Pune. In

this branch around 700-800 employees are working. The product profile includes:

Image convertor, image intensifier,

X-ray tubes

Batteries

Electro-optics

4. MACHLIPATNAM: There was one Andhra scientific company, which was a sick unit.

This was taken over by BEL & is called ASCO unit in 1983. The products include:

Optical & optoelectronic equipment like binoculars, microscopes

Medical Electronics

5. NAVI MUMBAI: This is an industrial place near Mumbai. This unit makes:

9

Glass shells for black & white TV picture tubes

Shelters for Electronic Equipment

Train Actuated Warning System

Electronic Equipment Assembly

6. PANCHKULA: Panchkula & Kotdwara were proposed simultaneously by the Government

in 1985. It was proposed to set up one unit each in Haryana & Uttar-Pradesh. But the place in

U.P. for setting up a BEL unit could not be decided while that at Haryana was decided &

hence this unit started earlier. This unit manufactures only tactical communication equipment

like VHF, UHF transceivers etc.

7. KOTDWARA: This is a unit in Garhwal district of Uttaranchal. This unit manufactures

radio relay, multiplex equipments & exchanges etc.

8. CHENNAI: The eight unit of BEL was established in Chennai. This unit manufactures:

Tank related electronic equipments

Optical fire control systems

9. HYDERABAD: This is another unit of BEL which manufactures electronic warfare

equipments.

CHAPTER 4

WAVE SOLDERING10

4.1 Introduction:- Wave soldering is a bulk soldering process used in the manufacture of printed circuit boards.

The circuit board is passed over a pan of molten solder in which a pump produces an upwelling

of solder that looks like a standing wave. As the circuit board makes contact with this wave, the

components become soldered to the board. Wave soldering is used for both through-hole printed

circuit assemblies, and surface mount. In the latter case, the components are glued onto the

surface of a printed circuit board (PCB) by placement equipment, before being run through the

molten solder wave.

As through-hole components have been largely replaced by surface mount components, wave

soldering has been supplanted by reflow soldering methods in many large-scale electronics

applications. However, there is still significant wave soldering where surface-mount technology

(SMT) is not suitable (e.g., large power devices and high pin count connectors), or where simple

through-hole technology prevails (certain major appliances).

Surface Mount Technology (SMT) has brought the electronic industry many benefits. Size and

cost reduction as well as increased in quality and reliability have been demonstrated in numerous

cases. There are many success stories and these are driving the industry in the direction of

greater implementation of SMT every day. The major users of SMT have found that SMT is a

process which can result in continuous improvements in product performance.

Many of the users have reported that product life in the field is increased as a result of a “no

repair” goal in the manufacturing environment. This, of course, does not mean that the product is

discarded if it needs repair. What it does mean is that the process engineer has established a very

achievable goal of “no repair”. The processes are being fine tuned every day, with much of the

feed back coming from the repair station. The repair station is a part of the solder process. In less

focused operations, the solder process and repair areas are two separate processes, but

unfortunately seen as necessary to making the product.

4.2 Wave Soldering Process :-

There are many types of wave solder machines; however, the basic components and principles of

these machines are the same. The basic equipment used during the process is a conveyor that

11

moves the PCB through the different zones, a pan of solder used in the soldering process, a pump

that produces the actual wave, the sprayer for the flux and the preheating pad. The solder is

usually a mixture of metals. A typical solder has the chemical makeup of 50% tin, 49.5% lead,

and 0.5% antimony.

The solvents in use within the wave soldering process are Isopropyalchol (IPA) andSenju Flux.

The use of these two solvents within this process are as follows:

4.2.1 Fluxing:-Flux in the wave soldering process has a primary and a secondary objective. The primary

objective is to clean the components that are to be soldered, principally any oxide layers that may

have formed. There are two types of flux, corrosive and noncorrosive. Noncorrosive flux

requires precleaning and is used when low acidity is required. Corrosive flux is quick and

requires little precleaning, but has a higher acidity.

Flux is applied to the underside of the Printed Circuit Board (PCB) to aid the wave soldering

process. The purpose of the flux is to remove surface oxides, prevent oxidation of the soldering

pads during the pre-heat and soldering process and improve wettability to ensure a strong low

resistance solder joint.

The PCB travels through the fluxer and solderwave machine on a conveyor. Inside the fluxer

machine there are three spray nozzles that move across the width of the PCB. As the PCB passes

through the fluxer unit the nozzles moves along the width of the PCB and flux is sprayed on the

underside of the PCB.

12

Fig. 2 :PCB Tray Movement

Fig. 3 : Flux Nozzle

The flux is pumped from its original container to a reservoir tank in the fluxer and gravity

fed to the spray nozzles. See picture below.

Cleaning of Flux :- Some types of flux, called "no-clean" fluxes, do not require cleaning; their

residues are benign after the soldering process. Typically no-clean fluxes are especially sensitive

to process conditions, which may make them undesirable in some applications.[ Other kinds of

flux, however, require a cleaning stage, in which the PCB is washed with solventsand

/or deionized water to remove flux residue.

13

Fig 4: Reservior Tank

4.2.2 Isopropylalchol (IPA):-

IPA is used within two processes within the wave soldering process.

1) Cleaning of the pallets which are used to hold the PCB as they pass over the fluxer and wave

soldering machine via conveyors. These pallets are removed from the machine on a daily basis

and are placed into two baths each off which contains approx. 100 litres of IPA. This activity

takes place in a location away from the main building at chemical shed number 7 as per “

Emission and Monitoring/Sampling Points” drawing number 401_3. Approx annual usage of

IPA (909K001) used for this particular cleaning process is 4.8T. This contaminated IPA is then

disposed of as hazardous waste.

2) The remaining annual quantity (approx. 3.7T) of IPA (909K001 & 907K009) is used within

the actual wave soldering production process to ensure that the conveyors on the solderwave

machine are clean and free moving at all times. This material is manually filled into a reservoir

on a daily basis and then pumped into a sub-reservoir that the conveyor passes through allowing

the conveyor chain to be cleaned and free to move. Some small quantities of contaminated IPA

will remain within the reservoir and sub-reservoirs and is removed as hazardous waste.

14

Fig. 5: IPA Reservoir

Fig. 6 : Conveyor

4.2.3 Preheating :- Preheating helps to accelerate the soldering process and to prevent thermal shock. The purpose

of the preheat and flux zones is to prepare the PCB assembly for soldering. To maximize

reaching the established goals, the flux should prepare the terminations and PCB solder pads for

the solder. RMA type fluxes are adequate. If the PCB or the parts do not demonstrate good

solder wetting characteristics, the supplier of these need to improve the solderability.

Concentrated efforts with the suppliers in improving solderability can pay large dividends.

15

The solder wave equipment manufacturers have recognized the importance of preheat and have

included individually controlled bottom side and top side preheat zones with individually

controlled heaters to reduce the gradual nature of the heating zones.

The goals of the process profile in the preheat zone are numerous.:-

A. The heating should be gradual and not exceed 2°C per second. Higher heating rates have

the potential of increasing the temperature differential across the board, which can increase the

amount of warp and twist (and possibly local delaminations) in the board as it exceeds the glass

transition temperature.

B. The heating should be somewhat uniform on the top and bottom side of the board.

During the preheat, the reflow solder side of the board must by necessity be kept a little lower

than the wave solder side, however, top side preheat will increase the uniformity of wave solder

preheat, and will decrease the temperature gradients the PCB is subjected to.

C. The heating should be in line with the needs of the fluxes. No clean fluxes may demand a

little more preheat. Excessive preheat should not be used.

D. The preheat should be uniform across the boards, and not be subject to board loading

and environmental conditions. The preheat zones of most wave solder machines are infrared

heating zones. Uniformity of heating is improving as more and more zones are being added to

the wave solder. However, most users have not applied the same care to the preheat zones of

wave solder equipment as they have to the reflow solder equipment themselves. Typical

problems seen with wave solder equipment preheat zones are usually as a result of the openness

of the throat and the equipment itself, and the environment the machine has been placed in. The

profile is typically established under ideal one board conditions. Then in production numerous

board loading configurations are run, resulting in excessive and different load conditions on the

preheaters.

16

Profiling under all conditions is suggested. A considerably worse situation can be encountered.

The environment around the wave solder equipment is normally very warm and uncomfortable.

Venting is added, air conditioning is sometimes made available, and doors to the room are

opened to make the environment more tolerable. All this variable cooling air is typically drawn

into the preheat zone through the bottom of the machine or the throat of the machine. Vents for

fumes accelerate this cooling tunnel. These have very large effects on the control and variability

of the profile, and can result in very large thermal stresses as the part leaves the solder wave.

Shadowing of the preheaters also can result in differentials of preheat across the board. It is

suggested that profiles be run with thermocouples in numerous locations across the board.

Shadowing can result from large components being placed near smaller components, tooling and

fixturing proximity, etc.

E. The temperature differential between the preheat and the wave solder peak should not

exceed 120°C. Of course, less is better. Some of the largest benefits in reduction of thermal

stresses can be achieved in the preheat zone. This recommendation is higher than that normally

given by ceramic chip capacitor suppliers. See notes under “Conclusions”. Some of the results

seen with higher thermal stresses are:

• increased solder fillet sizes

• increased solder bridging

• increased amounts of solder balls

• increased amounts of solder peaking

• increased failures of thermal stress sensitive parts such as ceramic chip capacitors

Traps to be Avoided

• Preheating from one side only

• Counting on controllers which measure heater temperature

• Establishing the profile under ideal conditions

17

• Using the same profile for all assemblies

• Using solder wave equipment which was designed for through hole soldering, and not having

adequate preheat zones.

• Large gaps between preheat and solder wave which result in large temperature drops.

Attention to the profiles as seen in the preheat zone, and then monitoring the important

parameters

Fig. 7: Wave Soldering (Through Hole Only)

Fig. 8 : Reflow Profile (Surface Mount Only)

18

4.2.4 Solder Bath/Pot :- The box containing the solder is called the solder bath, which has the capacity of 400kg. The

temperature of the solder bath is 250 – 270 degree Celsius. While the solder is heated up inside

the solder bath, the pump arrangement provides for the hot solder to flow. The solder nozzle then

produces a solder wave. After the solder bath, the conveyor belt is set on the angle of 4 – 7

degrees.

Different combinations of tin, lead and other metals are used to create solder. The combinations

used depend on the desired properties. The most popular combination is 63% tin, 37% lead. This

combination is strong, has a low melting range, and melts and sets quickly. Higher tin

compositions gives the solder higher corrosion resistances, but raises the melting point. Another

common composition is 11% tin, 37% lead, 42% bismuth, and 10% cadmium. This combination

has a low melting point and is useful for soldering components that are sensitive to heat

Fig. 9 Solder Bath/Pot

4.2.5 Solder Wave Zone :-Most SMT solder wave equipment now have dual zones. The first zone is more agitated to

increase the wetting action of the solder, and the second zone is usually a smoothing zone to

optimize the shape of the fillet and reduce bridging. Some of the waves are separated and some

are adjoining each other in the equipment.

19

As the PCB leaves the preheat zone and enters the solder wave zone, large temperature gradients

are established across the board. The differences in expansion establish twist, bow, bend, and

numerous other stresses across the assembly. These stresses are magnified for thinner boards,

and for large panels of multiple boards which have been pre-routed for separation. Adequate

fixturing and tooling is necessary to keep these stresses to a minimum.

The goals for the wave zone are:

A. The peak temperature of the wave solder should be kept to a minimum. Some tests have

shown that reduction of thermal stress between preheat and the wave solder is better

accomplished by reduction of the peak wave temperature (as opposed to increasing the preheat

temperature). A good goal is a peak wave solder temperature of 235°C. With this a peak preheat

temperature of 115°C is allowable, and the temperature does not exceed the glass transition

temperature of the board material. Wave solder peak temperatures of 250°C are common,

however, this requires larger preheat temperatures, and typically results in more stress to the

PCB.

B. Time in the wave should be kept to a minimum. Typical times in the total solder wave are 5

to 8 seconds. Time in the wave exceeding 10 seconds can begin to have detrimental effects on

the solder ability of the parts and the board, result in breakdown of the fluxes making cleaning

more difficult, and greatly magnify the stresses applied to the board.

C. Temperature between the waves should be maintained above the liquidus points. Some

equipment have gaps between the two waves, and with improper venting and room

environments, the solder temperature can go below the solidus temperature, and then be

subjected to another thermal stress in the second wave. This also will defeat the purpose of the

second wave, and greatly diminish the effect of “air knives” if they are used.

20

Fig. 10 : Solder Wave Zone

Traps to be Avoided :-

• Increasing wave temperature to improve solderability

• Increasing time in wave to improve solderability

• Increasing temperatures to reduce solder balls, bridges, skips, etc.

• Establishing wave profiles once, and not monitoring frequently

• Adding forced air cooling directly after wave solder

• Using fixturing which adds stress to the boards

• Convey or transfer systems which drop boards or introduce the possibility of twisting boards

by mechanical jamming in the conveyor.

21

4.2.6 Hot Air Debridging:-

The concept of using hot air blowing on the solder joints immediately after the wave to minimize

bridging and solder fillet size, is an excellent idea. The air temperature immediately at the exit of

the orifice is typically set near 275°C, and the impinging air on the part/board assembly is

typically less than 230°C. This concept was developed with SMT assemblies in mind, and has

been shown to be an excellent improvement.

4.2.7 Cooling Zone:-It is important that the PCBs be allowed to cool at a reasonable rate. If they are cooled too fast,

then the PCB can become warped and the solder can be compromised. On the other hand, if the

PCB is allowed to cool too slowly, then the PCB can become brittle and some components may

be damaged by heat. The PCB should be cooled by either a fine water spray or air cooled to

decrease the amount of damage to the board.

After the board assembly leaves the solder wave and the hot air debridging area, it enters a very

critical area. It is very important to let the stresses applied by the large heat and mechanical

warp, twist, and expansion differences relieve themselves in a natural slow manner. Some very

recent data indicates that thermal shock stresses applied by cooling after the wave can be more

detrimental than that applied by the heat stress of the wave itself.

The process engineer might have a tendency to supply forced air cooling directly after the wave

solder and hot air debridging areas. Some wave solder equipment is being supplied with fans and

some even have “CHILLER” zones. There are multiple reasons given for this attempt at cooling.

One is that the board needs to be cooled for people to handle it. Another is that the fans are there

and are turned on without reason.

Both of these are not valid technically and need further consideration. Another reason is that the

solder needs to be cooled rapidly to establish fine grain solder fillets (represented by nice “shiny”

solder joints).

22

While cooling can help this, it has been shown that the fine grain structure achieved this way is

only temporary. The stresses set up in the solder fillet and the board are relieved in less than 24

hours at room temperature and the solder structure begins to coarsen. Fatigue testing of various

solder joints have shown that the perceived advantage of shiny joints is not proven out.

Other sources of excessive thermal stresses can be found to be applied by:

• large heatsinks on the top side of the board which have not reached high temperatures during

the process

• excessive venting of the wave solder machine directly after or above the wave zone.

• room air inlets under the wave solder machine or through the exit and input throats of the

machine.

Air conditioned or winter air rushing through the machine can cause very stressful profiles.

23

CHAPTER 5

WAVE SOLDERING MACHINES

5.1 Different types of Wave Soldering Machines :-

There are different varieties of machine for wave soldering. Here the internal structure and some

machines are depicted in figures.

Fig. 11 : A simple wave soldering machine

24

Fig. 12 : A new and fully automated wave soldering machine.

Fig. 13 Wave Soldering machine(Automated Lead Free) operated by a operator

25

Fig. 14 Internal Structure and different zones of Wave Soldering machine.

26

CONCLUSION

The six weeks of summer training at BEL, KOTDWARA unit generated a lot more interest in

my subject.

It made me more aware of the scope of Electronics & Communication Engineering. It has also

made me appreciative of an industrial work environment.

Undergoing training on the indoor substation has helped me integrate conceptual knowledge with

real life application. I was fortunate to have personal guidance from experienced professionals

who took been interest in explaining the working details of various equipments.

I feel that without this opportunity, my own understanding of this subject and also the motivation

to acquire more knowledge would have remained incomplete.

Well, regarding future scope I think my training has given me enough motivation and an

exposure that I will try to join defence services or get linked up with the defence of the country.

“To know the technical know-how, industrial training is the best way to move forward.”

27

REFERENCES

[1] THE MAIN RESOURCES OF THE WORK WERE THE FACULTY OF HRD

DEPARTMENT.

[2] WEBSITE:

http://www.bel-india.com/

https://en.wikipedia.org/wiki/Wave_soldering

http://www.kemet.com/

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