Traditional soldering, or rather through-hole soldering, is out. This assembly process had once predominated electronics manufacturing. Major manufacturers are now looking for a more sophisticated alternative. All those manufacturing players who were affected due to low productivity or quality issues associated with through-hole soldering are now finding a quantum of solace in surface-mount technology (SMT). Moreover, SMT is environment-friendly due to the possibility of lead-free mode of operation.
If you are an entry-level electronics professional, it’s a good opportunity to make your career recession-proof by adopting the SMT path. Let’s delve a little deeper into the sector and figure out what skills your employer may expect from you.
Know the field
Open any electronic gadget and observe minutely the circuit. You will see some tiny components mounted on a board. In most cases, these are surface-mount devices (SMDs) assembled using the SMT.
The SMT market in India will grow proportionally with the growth of electronics manufacturing dominating all other production technologies. The electronics consumption in India has over the years seen phenomenal growth and is now valued at over $300 billion with an estimated growth rate of 23 per cent. The increased investments by global EMS (electronic manufacturing services) players in anticipation of the tremendous electronics demand will further accelerate the market size.
Ernst & Young projects that India can target an EMS share of one per cent in North America, two per cent in Western Europe, one per cent in Asia and five per cent in the rest of the world. It could account for 2.2 per cent of the worldwide electronics EMS market of $497 billion by 2010, which works out to $11 billion.
Market players at the top
The SMT players can be categorised into SMT production equipment suppliers and SMT equipment users for manufacturing. Juki, Panasonic, American Tec, Tyco and CDIL are the prominent names in the SMT field. EMS players are also major stakeholders.
Considering the skilled manpower of India, India is being seen as the logical outsourcing destination. Original equipment manufacturers such as LG Electronics, Nokia and Samsung already have their footprints in India. Moreover, some large EMS providers operating in India at present range from global participants such as Solectron, Flextronics International, Jabil Circuit, Celestica and Foxconn Technology to local firms like Deltron, TVS Electronics (TVS-E), D-Link and Bharat Electronics Limited (BEL).
Telecom equipment are in demand. So companies like Nokia, Siemens and Bharti Teletech are the potential recruiters of SMT professionals. Bharti Teletech has already started recruiting in this field.
Find your role
SMT is broadly dedicated to electronics and telecom professionals. Most companies look for degree or diploma holders with some hands-on experience in electronics. The scope for postgraduates or doctorate degree holders is rather limited. More precisely, in-hand experience may be more advantageous than higher educational degrees. You will find no threat from your contemporary fellows with IT or computer science background. But, at the same time, you should be prepared for a typical blue-collar job.
As an SMT engineer, you will work either at the manufacturing plant handling the process line or in the service sector dealing with maintenance and troubleshooting of SMT machines. Often, it involves quality control and shop-floor management. The designation and responsibilities may change with time but it is almost impossible to get rid of hardware if you decide to build a foothold in this sector.
What you can get?
The SMT sector offers a decent starting salary in the range of Rs 8000 to Rs 10,000 per month (excluding allowances) for diploma holders and Rs 15,000 to Rs 20,000 for degree holders .
One may continue career either in SMT services or in SMT manufacturing. But the growth prospects are higher in the latter case.
—Vishal Dahiya, Factory Automation, Panasonic
The workshop is revealed
It is quite possible that you never came across the term ‘SMT’ in your textbook. Don’t get disappointed. Two top executives of American Tec, Avishek Tyagi, regional manager-sales and marketing, and Pradyunma Salaria, deputy manager-SMT, reveal that the basic knowhow of electronics as well as other allied fields like electrical engineering and mechanical engineering is quite important. However, they specifically mention that it is no longer enough to know the fundamentals. The professionals are operating in a very cut-throat environment, so they should know not only how to survive but also compete.
N. Chandramohan, country head-SMT division, Juki India, opines that “proper training along with professional degree would be the turnkey for a fresher. This training should be totally industry-focused.” He feels that an effective collaboration between the industry and academia may be fruitful for both the parties. The existing industry-institute partnership models of some reputed foreign universities are ideal to follow.
From chip to ship
Undoubtedly, this training should be balanced enough to deal with both theoretical and practical aspects of SMT. Tyagi suggests that “a holistic training for the entry-level professionals in the field of SMT should cover the basic theory and application of SMT operation, process flow of SMT, soldering technique and solder pastes, basic principles of machineries used for SMT, software and hardware related to the SMT process, maintenance and quality control procedures and protocols in the SMT process and also storage, shipping and handling of SMT products.”
Besides the basics and applications of SMT, you need to know the basics of electronic circuit designing and also production technology.
Keep in mind that SMT is a whole new package responsible for improved integration of the circuit. That’s why the reliability of both chip-to-chip and chip-to-device interconnections is important. Basically, SMT reduces the package size resulting in greater functionality in the same board area. Mobile and handheld electronic items such as video cameras and cellphones are examples of low weight, high performance and also reduction in noise (primarily due to smaller electrical paths than leaded components) achieved with SMT. SMT is particularly useful for RF and microwave circuits where low noise contribution is mandatory. Moreover, it results in a higher operating speed due to shorter interconnect distances.
At first, today’s device requirements appear to oppose each other. SMT solves this problem in a different way. New types of components, new mounting and testing techniques and a new set of design guidelines are dedicated for this purpose.
SMCs: the building blocks
Proper training along with professional degree would be the turnkey for a fresher. This training should be totally industry focused. I feel an effective collaboration between the industry and academia may be fruitful for both the parties.
—N. Chandramohan, country head-SMT division, Juki India
You need to have a clear picture of surface-mount components (SMCs) as these are the building blocks. Functionally, they are no different from leaded ones.
SMCs are mounted on the surface of the PCB. The solder joints are all the more important as these impart both electrical and mechanical connections unlike the through-hole components where the component leads sit in the plated through holes which provide certain amount of mechanical strength when soldered.
You can identify SMCs with their unique identifiers which are a combination of their dimensions (width and length) expressed in inches; e.g., 1208 component means its dimensions are 0.12 (w)x 0.08 (l) inch2. Ceramic capacitors, tantalum capacitors and thick-film resistors form the core group of passive components.
There are two main categories of chip carriers: ceramic and plastic. The plastic chip carriers are primarily used in commercial applications. The ceramic packages are expensive and provide hermeticity. These are used primarily in military applications. Both the passive and active SMCs are much smaller in size than their through-hole analogues. Not only the size but also the shape of these components is modified according to the need of automated handling and better stability.
SMCs are most commonly available in flat rectangular shape. Another interesting point is the leadless format of passive components, whereas active components may have mountable lead or leadless terminals. To reduce the size of the circuits, these components often have reduced pitches.
The current trend is towards the usage of larger pin-count packages. Packages having more than 84 pins become impractical with 50mil lead centres due to larger package area and difficulties in manufacturing. To overcome the difficulties associated with larger pin-count packages, VLSI manufacturers have adopted 25mil centre. Often, this extreme size reduction reduces the mechanical strength. Thus, it becomes a designer’s challenge also.
In summary, surface-mount components serve the same functions electrically as their through-hole counterparts. However, these have smaller package area and better electrical performance. At this stage, all the components are not available in surface-mount form and therefore the designers have to choose rightly between conventional and surface-mount components.
How to mount on the surface?
The next thing you need to know is the process flow of the mounting operation. It is the simplest form of assembly. The basic steps involved are paste application, pick-and-place of components, preheat or reflow, cleaning, inspection, touchups and, last but not the least, testing and repairing related activities. Try to know the activities associated with each of these steps as well as the machineries used. Learn how the software and hardware parts of SMT equipment are dedicated to maintain process parameters. Remember, all process parameters are focused on addressing three issues: ensure mechanical strength of the assembly, better automation without drifting of the components and higher-quality end products.
Turn to paste application. You will find various dispensing methods and adhesives available. In dispensing you will come across the terms like pin transfer, screen transfer and pressure syringe transfer. Each of these has some specific advantages and disadvantages and you have to select the most suitable according to the need of the system. For example, the pressure syringe method can handle irregular surface but requires more maintenance. Whereas, screen transfer is a comparatively simpler method but it is applicable only on flat board surfaces.
Typically, an adhesive consists of a resin and a hardener. You need to know the importance of their mixing properties. Look, no adhesive is suitable for all types of applications. So, instead of knowing them individually try to learn the process requirements and matching procedures. Here you may get acquainted with the ‘pot life’ or the extent of cross linking of the resin mix.
Though solders are available in many forms, solder pastes are the most suitable form for surface mounting. Most of the solder pastes used for surface mounting are lead-free in nature, leading to an environment-friendly manufacturing process.
The efficiency of soldering is dependent on the rheology of the solder paste as well as its solderability. Solderability is the property of wetting. Good wetting results in the formation of a uniform, smooth, unbroken, adherent coat of solder on the base metal. Therefore wetting is an essential prerequisite for soldering. Wetting means that molten solder diffuses into the solid surface of the metal to be soldered. It is possible only if the solder can come into immediate contact with the metallic surface of the solid metal part. Any filmy adhering contamination such as oxides or oil on the surface to be soldered will act as barrier to metallic continuity and thus prevent wetting. A drop of solder on a contaminated surface behaves in the same way as an isolated drop of water on a greasy plate.
Pick and place
Now, paste is applied. The interconnection will fail if the components are not placed properly on the board. Let’s see how ‘pick and place’ takes place. You have to be cautious in this step to avoid drifting. All pick-and-place machines operate in automatic mode. For small-to medium-volume productions, single-arm machines are sufficient for the job. For large-scale production, simultaneous placement machines are required.
The basic principle of ‘pick and place’ is driven by the movement of vacuum nozzles. Moreover, there is a sensor to recheck picking before proceeding for placement. Precisely, the operation takes place by using a combined setup of hardware and software.
In large-scale automation, the pick-and-place machines are able to handle more than 40,000 components per hour. According to a Frost & Sullivan report, pick-and-place equipment software account for more than 70 per cent of total SMT software. So try to understand both the hardware and the software aspects of the operation.
Soldering is the most significant step of the process. It marks the difference between SMT and traditional through-hole techniques. Major SMT operations follow either preheating or reflow soldering.
Reflow soldering is the most preferable. Reflow soldering of surface-mount components is advantageous over through-hole methods due to provision of mass soldering, consistency in manufacturing through precise control of process parameters and also flexibility to run small production as well.
A holistic training for entry-level professionals in the field of SMT should cover the basic theory and applications of SMT, process flow, soldering techniques and solder pastes, basic principles of machineries used for SMT, software and hardware related to SMT process, maintenance and quality control procedures and protocols in the SMT process and also storage, shipping and handling of SMT products.
—Avishek Tyagi, regional manager-sales and marketing, American Tec.
You need to know the advantages of this method over the wave soldering. It does not need any extra solder as the solder paste already exists on the board. The paste reflows on heating and solder joints are formed on cooling.
In most cases, the heating is done either using infrared rays or by immersing in the vapour of a liquid boiling at a temperature higher than the melting point of the solder. Usually, liquid fluorocarbons are the liquid of choice.
Other modes of heating in use are hot-air and hot-gas. Try to get some knowledge about the specific application, advantages and loopholes of each process. For example, application of vapour provides uniform heating but the process may be costly and produce pollutants. As an SMT engineer you will be expected to understand the process optimisation. Keep in mind that reflow soldering often takes more time but is also more versatile from the application point of view.
Now you are almost at the finishing line of the chip-to-ship cycle. Soldering is done. The raw products are ready. But it is mandatory to clean them and assure their quality before serving to the customers. Cleaning of paste residues is important to avoid corrosion of joints.
Selection of proper cleaning solvent is really a tough job. In most cases, water-based solvents serve well. But for the sake of better understanding, try to get information about other types of solvents also. For example, flu orinated solvents are good cleaner but not used due to environmental hazards.
After cleaning, the finished products are stored and tested. Storage, handling and testing are continued as per the quality standard protocols designed by regulatory bodies like SMEMA.
Get set go…
Now that you have had a deep understanding of SMT, you are ready to explore the SMT field. So pull up your socks, plan your final-year project in SMT field and find a suitable firm to pursue it. To grab every possible opportunity, surf the websites of related organisations and send requests for your project work. You can even visit the 15th Componex Nepcon India 2009, which will be held from 24th to 26th February at Pragati Maidan, Delhi. Perhaps, it will be your first interaction with the industry, but believe me it will be really fruitful.