With technological changes, reflow ovens are gaining importance

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Reflow oven is as important as screen printer and pick and place machine in the surface mount process, but unfortunately the pick and place gets more importance in terms of investment than the former. While purchasing reflow ovens factors like number of heating and cooling zones and initial investment cost are usually given much importance, but performance criteria and running costs are often ignored.

By Sandhya Malhotra

Sunday, April 18, 2010:
Reflow soldering, which is the most common method of attaching surface mount components to a circuit board, is a process in which a solder paste (a sticky mixture of powdered solder and flux) is used to temporarily attach electrical and electronic components to their contact pads, after which the entire assembly is subjected to controlled heat, which melts the solder, permanently connecting the joint. Heating may be accomplished by passing the assembly through a reflow oven, under an infrared lamp or by soldering individual joints by a hot air pencil.

The reflow process melts the solder and heats the adjoining surfaces, without overheating and damaging the components. In the conventional reflow soldering process, there are usually four stages, called ‘zones’, each having a distinct thermal profile—preheat, thermal soak (often shortened to just soak), reflow and cooling.

Importance of reflow ovens in SMT line

According to Christopher J Fussner, president, TransTechnology India Pvt Ltd, which represents Heller Industries in India, “Reflow oven is a necessary processing machine for an SMT line and is indispensable. The automotive segment uses nitrogen based reflow ovens, whereas consumer durable manufacturers primarily use air reflow ovens. It’s a good sign that manufacturers are gearing up to fulfil RoHs compliance needs and reflow ovens helps them achieve it.”

These machines can be used either as a soldering machine or glue curing machine depending on the process. Says L Sampath, CEO, EMST Marketing Pvt Ltd, “Reflow is one of the three main processes in an SMT line, especially after manufacturers decided to go lead free. With higher operating temperatures and narrow process band, it has become a crucial machine in the process. Further, boards are increasingly getting complex and the ovens are crucial in soldering ball grid arrays (BGAs) and miniature chips together by maintaining a uniform temperature across the board .

Sampath points out that though big EMS companies are setting up shops in India with huge investment, what is more interesting is that several small and medium speed SMT lines are being set up for in-house manufacturing. “For companies like ours, this growth is more important,” he adds.

According to SP Arora, Senior business manager, NMTronics India Pvt Ltd, who represent US based Speedline Technologies (ITW Group company) for Electrovert reflow oven, “Reflow oven, which ensures proper melting of solder paste between PCB pad and SMT components leads to subsequent cooling for solidifying the melted solder paste. Reflow oven also needs to control the exposure of PCB w.r.t. to high temperature (upto 250ºC) for a certain time period.

Types of reflow ovens

Depending upon the volume of production, there are entry level, medium and high end reflow ovens. However, demand of high end reflow ovens is increasing as the production levels are soaring high.

In general, reflow ovens can be divided into two categories—conveyor forced air type and batch type ovens. Ashutosh Agate, director, Agate & Agate Marketing, which represents Italy based reflow oven manufacturers TWS Automation, says, “We offer various types of reflow ovens including top box ovens for low volumes, R&D ovens, and prototype ovens. Bench type conveyorised reflow oven for mid and high volumes.

Table top batch type reflow ovens are more useful for startups. “We have proven machine EMS gallant with over 150 installations all over India. Many companies started SMT production with this machine and gradually updated to high end ovens. Some EMS companies have been able to produce very complex cards with BGAs and fine pitch QFPs using this machine,” says Sampath.

For medium production companies, EMST Marketing has launched its first conveyor reflow oven—KONARK 257, which has seven heating zones and one cooling zone. “We expect this machine to be quite successful like our lead free wave soldering machine. Currently, these machines are being imported from China and Korea,” adds Sampath.

Vacuum reflow, which is a new technology introduced by SMT Germany. This is mainly for relow soldering of high end products like, network cards and high tech auto electronic cards and medical electronics.

Technological advancements

Apart from advancements in lead free technology, energy saving and emission protection are also gaining importance to ensure that reflow soldering becomes more environment friendly.

Shares Fussner, focus is on reducing nitrogen and electrical consumption, along with improving the capability of ovens for better zone to zone separations. “We believe that by reducing nitrogen and electrical consumption manufacturing process will improve. We are focusing on these factors to ensure better customer experience,” says Fussner.

Cost of implementation and maintenance

Cost of running a reflow oven is very little compared to other machines in an SMT line. It mainly depends on the production volume and number of hours the machine operates. “Our reflow ovens consume less power compared to other machines in the line and their maintenance cost is low,” says Prasad Gurjal, managing partner, Drive Technologies, a Pune based Indian manufacturer of reflow ovens, available in two models with 3 and 5 zones. Presently, the company has installed base of 350 machines of reflow ovens and other SMT machines.

“The main cost involved in running a reflow is that of power and air consumption,” says Suresh Nair, director, Leaptech Corporation, a supplier of Taiwan based Tangteck’s air and nitrogen reflow ovens.

Agreeing to Nair, Sampath adds, “Our principal company SMT Germany makes the most energy efficient ovens. Its latest design incorporates several innovative features including bulk heads to reduce openings down to minimum for reduced power as well as nitrogen consumption, in case of nitrogen machines; isolation of cooling and heating zones; and process gas cleaning system called ABS, which takes out the used gas, cleans it to special patented system and recirculates it.

“Maintenance cost of reflow machine varies from US$ 100–1,500 depending on the type of maintenance and consumables required,” says Arora.

The price of a reflow oven depends on its usage of air or nitrogen and number of heating zones. “Our reflow machines range from $20,000 to $100,000,” says Nair, whereas Agate & Agate Marketing offers reflow ovens ranging from Rs 2-10 lakh. Drive Technologies’ machines cost Rs 3-6 lakh.

Easy maintenance

Like any other manufacturing machine, normal service support is required for reflow ovens too. But unlike screen printer and pick and place machines, it is less critical in terms of technology, and hence, easier to maintain. The maintenance include cleaning of the machine from flux deposition at various places and filters of flux management system. The amount of time to complete these tasks depends on the usage period of the machine.

In-house maintenance is also possible if the employees operating the machine are trained by the manufacturer/agent, the vendor has a prompt spare shipping service. “Most of our customers do the maintenance of their machines on their own,” says Nair.

Gurjal says that given the simple structure of the machine, users are encouraged to do the maintenance themselves. “However, it is advised that only trained technician should do it under our guidance. Preventive maintenance covers cleaning, oiling and tightening,” says Agate.

According to Sampath, their table top reflow oven EMS Gallant does not need much maintenance, except regular cleaning. “Moreover, our mid-end automated ovens from SMT Germany is different from other leading US and European machines. Its ABS absorption system removes most of the flux through a heating system filled with special granules which drastically reduces the cleaning efforts,” Samapth says.

After sales service

Usually, after sales service is provided by manufactures and imported machines are serviced by authorised suppliers in India.

According to Gurjal, preventive maintenance should be done periodically for ensuring continued satisfactory performance. “We advice the customers to regularly check the health of their machine by changing consumables, calibration and shift in programme profiles to avoid machine failure. We offer modular or simple design, proper maintenance training to user and a cost effective service support with timely backup in terms of advice or personnel visit, if necessary,” he adds.

Leaptech Corporation provides full end to end service support to its customers including installation, commissioning, process assistance, profile setting and troubleshooting.

“Installation, training on operation and maintenance of machine, trial run, setting of product temperature profile as per customer requirement, etc, are some of the key services we provide to customers,” informs Agate.

Tips for setting up reflow ovens

Before buying reflow ovens, buyers should do a thorough study of their requirements, relevance of the machine’s feature to their needs, cycle timing, user friendliness, easy availability of spares and investment. Nair advices, “Plan your oven requirement keeping in mind your future expansion requirement, as you can’t keep changing your machine every time.”

“We advise our customers to go for low cost, low power consuming machine, which is more reliable,” adds Gurjal.

Selection of proper machine is important. Sometimes decisions are taken based on figures for a number of heating zones, whereas there are other more important aspects that need to be looked into like heating length, volume of air circulated, initial and steady state power consumption, N2 consumption for nitrogen machines and maintenance required, etc. Therefore, buyers should do a detailed analysis of these aspects to ensure maximum returns on their investment. “Cheaper machines often result into more power consumption and maintenance (loss of production) cost which offset the initial savings on investment. Thus, care must be taken in this regard,” says Sampath.

Buying Tips

  • Check the length of heating tunnel with respect to production requirement
  • Check the type of soldering environment inside machine
  • Check heating blowers per zone (Top & Bottom)
  • Ensure whether the machine is upgradable from air operation to inert atmosphere with nitrogen gas application
  • Buy performance enhancement tools like flux extraction system, refrigerated chilling system, etc
  • Check the type of conveyor system
  • Ensure that the machine is power efficient

Electronics Bazaar, South Asia’s No. 1 electronics B2B sourcing magazine

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