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Search continues for cause of exploding Samsung smartphones

Some three months after reports of a serious defect in Samsung Electronics' flagship Galaxy Note 7 began to emerge, the search for a cause goes on as the South Korean government becomes involved.

Despite preorders for Samsung's premium Note 7 smartphone pouring in, a spate of reports of the phone catching fire or exploding began emerging just a few weeks after the device went on sale in South Korea and the U.S. on Aug. 19. In September, the South Korean tech giant announced a global recall of the device and promised to replace every unit already sold. But following user complaints about replacement phones overheating, the company stopped production of the Note 7 less than two months after its launch.

On Aug. 24, shortly after its release, some users posted on a South Korean online community website messages claiming that their handsets burst into flames while charging and included pictures of severely damaged devices. Samsung has begun to investigate the damaged Note 7 units collected from users to determine the cause of the fires. 

"Based on our investigation, we learned that there was an issue with the battery cell," Samsung explained on Sept. 2. "Although we rely on two companies, Samsung SDI and Hong Kong-based Amperex Technology, for lithium-ion battery supply, an overheating of the battery cell occurred when the anode-to-cathode came into contact. This is a very rare manufacturing process error." The company identified the batteries made by its affiliate Samsung SDI as the cause of the defective handsets.

Samsung decided to source all of the batteries used in new Note 7 phones from Amperex Technology. The company said, "For customers who already have Galaxy Note 7 devices, we will voluntarily replace their current device with a new one over the coming weeks or provide full refunds for customers who want their money back." Samsung's exchange program proceeded smoothly as customers started receiving replacement models on Sept. 19.

Down in flames

In Seoul, however, a replacement Galaxy Note 7 erupted into flames on Oct. 1. An owner of a new handset in China also claimed that the device caught fire.

On Oct. 2, the South Korean electronics giant requested the government-backed Korea Testing Laboratory, a certification body dedicated to enhancing the safety and quality of electronic products, to conduct an investigation into the cause of the Note 7 handset overheating and exploding. On Oct. 5, the test lab concluded that it has found no evidence of burnout that results from a decline in the performance of batteries and that external pressure could have been applied to the isolation plates that separate the anode and cathode.

Even worse, a replacement unit for a Galaxy Note 7 caught fire in Kentucky on Oct. 4. In the same U.S. state, on Oct. 6 a passenger's replacement phone also began smoking on a Southwest Airlines plane shortly before takeoff, forcing all passengers and crew members to evacuate.

After multiple reports of its Galaxy Note 7 explosions, the South Korean company had no choice but to halt production and sales of the fire-prone device. The official announcement was made in the U.S. on Oct. 10 and in South Korea the following day.

The South Korean media reported that the move represents Samsung's complete abandonment of the Galaxy Note 7. The company did not deny the report.

In an unprecedented step, the world's biggest smartphone vendor recalled a product a second time. More importantly, Samsung has no idea why its premium phone keeps catching fire, initially blaming faulty batteries for its Note 7 woes. As Samsung engineers are still unable to reproduce the explosions, there is a long way to go before the company works out what went wrong with the smartphone. The situation could lead to a considerable loss of consumer confidence.

A TV news program produced by the Korean Broadcasting System, the national public broadcaster of South Korea, cast some doubt on whether Samsung might have known what caused the handset to explode and might have already learned the exact reason behind the latest fires, intentionally putting the blame on the batteries. The program is titled "The batteries are unable to speak."

On Oct. 11, Samsung posted just a simple message to its website that said, "A close investigation into overheating replacements of the Galaxy Note 7 is underway." The company has not yet officially announced the cause of the defective units. As a result, speculation persists over what is behind the problems with the Note 7 handsets among journalists and social media users.

Government wades in

On Oct. 13, a public debate was held at the National Assembly of South Korea to discuss the situation. The assembly summoned Lee Won-bok, president of the Korea Testing Laboratory. He said it was careless of us to say that the battery caught fire after external pressure was applied to it.

During the question and answer period, Lee admitted that the test lab did not conduct a fire simulation test, but only used the battery test results that were submitted by Samsung when it issued the first recall to make a comparative analysis between batteries produced by Samsung SDI and those by Amperex. Based on the results, the Korea Testing Laboratory concluded that batteries might have caught fire and those made by the Hong Kong company are safer.

At the assembly, several ruling and opposition legislators argued that the president of the Korea Testing Laboratory should bear heavy responsibility for deciding that Amperex batteries are safer, without clearly knowing the cause of exploding Note 7 units. They noted that if the test lab had carried out the first round of safety tests diligently, it would have prevented the company from issuing a global recall for a second time. Lee immediately explained, "As we are committed to serving the needs of customers, we performed the test as requested by Samsung [to find any sign of external pressure placed on plates contained within battery cells]. Our lab didn't confirm whether pressure is applied to the battery before or after explosion." He added, "We cannot undertake other tests at our discretion."

On the same day, the National Assembly also focused on discussion of why circuits and systems for controlling the thermal heat generated by the application processor did not work, especially since the Note 7 phone is packed with multiple high-performance functions that heat up the battery, including an iris scanner and fast-charging technology.

Because premium smartphones are equipped with high-performance semiconductors, a certain degree of heat generated by the battery is unavoidable. To reduce the impact of heat buildup, the handset incorporates a system to regulate the battery's temperature. If this system detects that the battery temperature is continuing to rise, it sends a warning signal to the application processor in order to reduce power usage by dimming the display. But if the temperature increases further, the heat control system forcibly shuts off power to prevent the battery from catching fire. However, the control system for the Note 7 unit did not function properly, a failure that is seen as a serious problem.

The Galaxy Note 7 is equipped with a heat pipe designed to keep the application processor's temperature in check. But some people pointed out that the heat pipe failed to function. Even if the handset burst into flames due to the battery being squeezed by external pressure, the battery should be less vulnerable to that pressure. 

Following a debate at the National Assembly, the Korean Agency for Technology and Standards on Oct. 17 decided to launch a joint team with Samsung to thoroughly investigate the cause of the explosions. The team includes 10 South Korean experts. According to the results, the government may impose disciplinary action against the South Korean company.

As a first step, the test lab will look into Samsung's internal documents on the fire incidents and those from the phones that have caught fire in the country. Using four to five Galaxy Note 7 phones as samples, the lab will adopt a wide range of investigative methods, which will include destructive and nondestructive tests, CT scanning, a high-heat influx test, and testing on application processors and electronic circuits. The test lab plans to make a comprehensive survey to pinpoint the exact cause of the incidents. It will reconsider Korea testing Laboratory's previous conclusion that blames the batteries.

The three-month research project is slated to be completed by January 2017. The explosions were first reported at the end of August. Particularly serious damage is seen on the battery side of the devices. There were many burn scars on replacement units that caught fire in early October, according to government sources. If the explosions are attributable to more than one factor, it will likely take more than three months to finish the survey. 

Instances of the Note 7 phones catching fire and exploding in the U.S. are immediately reported to the U.S. Consumer Product Safety Commission. While investigation into the fire incidents is gradually proceeding in the U.S., the two countries are unlikely to conduct joint inspections in the near future.

Cho Changeun is an IT journalist. She was born in Seoul and spent time from elementary school through high school in Japan. After graduating Ewha Womans University in South Korea, she earned a master's degree in the Socio-Information and Communication Studies Course and completed a doctorate in the Graduate School of Interdisciplinary Information Studies at the University of Tokyo.

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