Surface mount technology (SMT) has slowly but surely started to make a place for itself in the Indian electronics manufacturing industry. The automated optical inspection (AOI) system is a vital part of the SMT line. Smallscale manufacturers, who want to start using SMT in their manufacturing process usually seek only three machines—pick and place, reflow and printers, not considering AOI important enough to invest in.
However, for bulk manufacturing, a manufacturer cannot overlook the importance of AOI machines as these not only detects defects but also help in correcting them.
By Atanu Kumar Das
Monday, July 20, 2009: Why AOI?
Repairing becomes 10 times more exorbitant in the second stage of a manufacturing process, if a flaw has been ignored in the first stage of production. The number of defects produced in an SMT device depend upon numerous factors, such as printed circuit board (PCB) design, quality of components, manufacturing consumables like solder paste or glue, process parameters, technology of SMT machines used and the associated equipment installed in the SMT line.
Ideally, the defect level of a good SMT line should be 100-200 parts per million (ppm). If a PCB assembly, on an average, contains 200 SMT components, the defective boards assembled with this kind of ppm may still be more than 2 per cent. Some of the defects are related to reliability of the product, for example, a weak solder joint may not get noticed at the electrical or functional testing stage. This is where an AOI system is relevant. An AOI machine can spot aberrations and, hence, prevent the assembly from passing on to the next stage of the process without adequate rectifications.
According to Rakesh Shetty, business development manager, ViTechnology, one of the global leaders in AOI machines, “The value of inspection in pre-and post-reflow is being appreciated and adopted. AOI systems have to be used to correct and improve the process, not merely to locate deviations and flaws.”
In a complex PCB environment, where the components are too miniscule, AOI machines help in pointing out the minutest of errors.
“If the PCBs have miniature components then one has to go in for an AOI machine that can perceive faults in such minute SMT components. In addition to evading repair costs by skipping defective boards through flaw detection, one also eliminates the possibility of losing out on precious business opportunities due to inferior assemblies,” says Sanjiv Narayan, managing director, SGS Tekniks Manufacturing Pvt Ltd, an NCR-based EMS company.
What do buyers want?
“The first essential factor that affects our decision making in the procurement of an AOI machine is whether to go for a new AOI machine or a second hand machine or demo machines. Sometimes good and not very old demo machines are available at half or one-third the price of the new machine,” explains Narayan.
“We have to calculate the return on investment (ROI) before determining what kind of AOI machine we want to buy. If our clients demand assurance of negligible quality concerns, then we have to go in for a high end AOI machine. Otherwise, one can also acquire a medium range machine,” comments a spokeperson of a multinational electronic manufacturing services (EMS) firm.
Narayan advises, “If the volumes are not great, one may opt for a simple desktop model, which is available at a lower cost. If the volumes are high, then it is more sensible to obtain inline AOI machines, with low inspection time.”
“The cost depends on the kind of component package and the defect type that needs to be identified. It is worthwhile to spend 1per cent of the bill of material costs on AOI. On an average, a new AOI machine costs Rs 5 million. Assuming an average bill of material costs of Rs 300 and 80,000 PCBs per month, the ROI for an AOI machine of Rs 5 million will be less than two years,” adds Narayan.
One of the most prominent issues on an AOI machine buyer’s mind is the kind of after sales support he will get from the vendor or the distributor. Buyers expect the vendor to provide them with technical engineers at the site of manufacturing as that helps in reducing the duration of downtime.
Manufacturers prefer to enter annual maintenance contracts with vendors after the warranty period expires. They also expect the vendor to conduct periodic preventive maintenance checks and also train (manufacturers’) technical staff for the same. Furthermore, producers expect vendors to promise a committed service response time of 4 hours for any complaints that may arise.
Factors that buyers consider while purchasing an AOI machine
- Brand reputation in the market
- Credibility of authorised dealer/ vendor
- After sales service support
- Time taken to attend to complaints
- Availability of spares
Vendors should maintain a stock of spares that are mostly demanded so as to provide them to manufacturers for replacement. Any spares other than the regular ones should also be available with the vendor within 72 hours of complaint lodging.
“Training is a key aspect of operating an AOI machine. The equipment company must have locally trained engineers to impart equipment support and programming,” stipulates Narayan.
It is obvious that the EMS industry has woken up to the many virtues of AOI machines. With the ascent in EMS activities in the nation, the deployment of these tools in manufacturing units across the country is guaranteed to go up as well.
“I have witnessed the market mature and burgeon since 1994, when there were only a handful of companies with SMT lines. The transition from through hole to SMT is an ongoing process, with only a few people still using the former. Electronics manufacturing within the country is expected to hit a positive note by 2010, with a ratio betweeen the total market and total available market reaching 43 per cent. This suggests that we have great potential to grow and amplify,” concludes Shetty.
Electronics Bazaar, South Asia’s No. 1 electronics B2B sourcing magazine