Provides detailed overview of investigation.

Samsung executives today announced that the cause of the Galaxy Note7 incidents was due to a fault in the design and manufacturing of the devices’ battery. The press conference was held in Seoul, South Korea, after four months of comprehensive investigations.

In his address, Samsung president of mobile communications, DJ Koh said:

“I deeply apologise to all of our customers, carriers, retail and distribution partners. We thank you for your patience and continuous support. We believe that as a first step to regain your trust, it is important to provide a thorough understanding of the cause behind the Note7 incidents and our plan to take preventative measures.”

Photo: Jung Yeon-Je/AFP/Getty Images

The Galaxy Note7 launched globally on August 19, 2016. Two weeks later, on September 2, Samsung announced a global product replacement program. The device was discontinued on October 11. The current device return status globally to date is 96% of devices sold and activated.

“We are grateful to Note7 owners, carriers, retail partners and business partners for their help to expedite this process and achieve this exceptional return rate,” Koh said.

Over 700 Samsung researchers and engineers analysed more than 2,000 fully assembled Galaxy Note7 devices and more than 30,000 Galaxy Note7 batteries. These were subjected to repeated charge and discharge testing. We found that both fully assembled devices and batteries exhibited incidents at similar rates to those in the field.

“This indicated that the incidents occurred from the battery cell itself so we proceeded to focus our investigation on the batteries. Lithium-ion batteries are arranged in layers consisting of a positive electrode, negative electrode and the physical separator between the electrodes. These layers are rolled in to what is called a jelly roll.

“In general, a short circuit within the battery cell may occur when there is damage to the separator that allows the positive electrode and negative electrode to meet within the jelly roll.

“Based on a detailed analysis of the affected batteries, both battery A (from first recall) and battery B (from second recall) we identified two different factors. From Battery A units, we found the incidents consistently occurred in the upper right corner of jelly roll in battery.

“Our analysis showed that the cause of the incidents was deflections in the negative electrode. We were also able to confirm additional contribution factors, such as incorrect positioning of the negative electrode meant a higher likelihood of incidents.

“When we examined Battery B, we consistently found melted cupper on the negative electrode area, facing the positive tap, indicating a short circuit had initiated in that area of the battery. Based on our analysis, the main reason for the incident was an internal short circuit as a result of abnormally high welding bars that formed during the ultrasonic welding process to attach the positive tap.

“Due to the high welding bars, penetration of the insulated tape in the separator resulted in direct contact with negative electrodes. In addition, we found a number of batteries that were missing the insulation tape.”

Overview of investigation

All aspects of the device including hardware and software, assembly, quality testings and logistics, were all reviewed in detail to determine the cause of the incidents.

“To ensure that we conducted a comprehensive investigation, we believed the most important step was to replicate the incidents. In order to do that, we built a large scale charge and discharge facility where we were able to replicate the incidents and complete a detailed analysis,” Koh explained.

  • Fast charging feature: Samsung conducted a test of the fast charging feature both on and off using both wired and wireless charging methods and a variety of range voltages and currents.
  • Water-resistant feature: Samsung carried out charged and discharged tests with and without the back cover.
  • Newly introduced iris scanner: Samsung tested whether an active iris scanner had a significant effect on electrical current use.
  • USB Type C port: Samsung subject the port to a more than 4,000 volt electrostatic discharge to check if it was related to the incidents.
  • Software: the company ran tests on variety of preloaded and downloaded third party apps as well as under abnormal software conditions to see if there was excessive current drain on the battery.

“None of these tests demonstrated an abnormality or correlation to the reported incidents. We also conducted a full investigation of every aspect of the process beyond the product itself from quality assurance to manufacturing and logistics handling stages starting from the receipt of the battery through shipping of the assembled and tested complete devices,” Koh said.

“We tracked the handling of all parts and devices throughout the manufacturing and logistics process in an effort to determine whether there were any contributing factors. Although none of these tests demonstrated an abnormality or correlation to incidents, we have nonetheless, taken additional steps to enhance safety,” he said.

In addition to its own investigation, Samsung also retained independent industry expert organisations, including UL, Exponent and TUV Rheinland, to provide objective, unbiased analysis. The company has taken several corrective actions to ensure this never happens again, including the implementation of a multi-layer safety measures protocol at the product planning stage, and an 8-Point Battery Safety Check.