Faulty batteries from suppliers were to blame for the Galaxy Note 7 catching fire and exploding, Samsung Electronics has announced after its near four-month-long internal investigations into the matter.
The ultimate responsibility, however, fell on the company itself for setting the battery target and signing off before the launch, said Samsung mobile president DJ Koh, who promised a new eight-step inspection plan for future models to avoid such incidents again.
The president said he "deeply apologizes" for the Galaxy Note 7 issue. "We believe as a first step to regain your trust, it's important to provide you with a cause ... and to fully investigate the issue."
The South Korean tech giant tested 200,000 Note 7 smartphones and 30,000 batteries after excluding other possibilities. The electric current or changes in the current in relation to software, iris-scanner, USB Type-C, and water- and dust-proof back covers showed that they were not linked to the fire, Koh said.
After simulating incidents with the test models, they had the same ratio of fires as they did in the market, the mobile boss said.
Batteries from supplier A, or Samsung SDI, and supplier B, ATL, had different problems but all led to a short circuit that caused the fires.
Third party investigators UL, Exponent, and TUV Rheinland, who Samsung consulted for the testings, also showed their findings at the conference.
Sajeev Jesudas of UL found the problems with the smartphone itself, but found deformation at the upper corners for Samsung SDI's batteries, while thin separators and missing insulator tapes for some ATL units were likely to blame for the faults.
Similarly, Exponent's Kevin White said the agency found no fault in the hardware or software of the phone but Samsung SDI's had unintended damage to electrode winding caused by the pressing of an inadequate pouch design. ATL's showed no such design flaw but that poor welding of separators caused the fires.
TUV Rheinland, which inspected the logistics of moving the phones and batteries from Korea, and Vietnam to China -- Samsung's main supply chain line for the Galaxy Note 7 -- found no cause of damage from processes and workstations.
Koh said the ultimate responsibility fell on Samsung Electronics for giving the go-ahead and announced a new eight-step inspection process -- durability test, visual inspection, X-ray test, charge and discharge test, leak detection test, disassembling test, accelerated usage test, and battery voltage comparison test -- to be applied to future smartphones.
"To make an innovative Note 7, we set the target specification for the batteries, and feel a grave responsibility for failing to test the battery design and manufacturing process before launch," said the president. "We will put safety and quality first going forward."
A new component team will be formed to inspect models under the quality division. A advisory board made of outside experts will also look at the new models, Koh said. Samsung is considering sharing the results of the investigations with the industry, he added.
New models will have more space reserved for batteries and a software algorithm will be applied that better controls charging speed, current flow, and temperature.
Out of 3.06 million Note 7s distributed to the market, 96 percent have been recalled globally, he added.