The Samsung Galaxy Note 7 was the device of the year when it was released late last year in August. However, the highly praised device was quickly recalled after a series of unfortunate explosions. Ultimately, the Samsung Galaxy Note 7 was pulled off the global market. Samsung promised to undertake intensive and costly investigations to find the source of the explosions. In light of the global recall of the device, Samsung said that 96% of the devices sold have been returned.
Earlier today, the South Korean company had a global broadcast to announce the findings of both their internal and third party investigations into the failure of the Galaxy Note 7. As a very inept and overarching summary, the battery explosions were the result of a flawed design and more grossly, some insignificant manufacturing flawed exacerbated by design.
Samsung’s Internal Investigation
A number of units of the Samsung Galaxy Note 7 were put through its paces. In fact, Samsung claims that 700 engineers tested 200,000 completed Note7 units and 30,000 batteries from their various suppliers. Samsung claims to have checked every inch of the Note 7’s functionality from charging, IP certification, the Iris Scanner, electrostatic interference of the USB-C port to Application overload. However, their extensive tests of other components and device functions showed no abnormalities or correlation to the reported incidents. Samsung also claims that a thorough investigation of their component logistics and manufacturing processes showed no abnormalities or correlation as well. With all of these factors investigated, the South Korean corporation looked to the battery.
With all of these factors investigated, the South Korean corporation looked to the battery. The created a massive Charge-Discharge facility to replicate the reported incidents. It was through the repeated charging and discharging cycles that they were able to replicate the reports. They found similar occurrences in both completed Note7 units and batteries. In their report, Samsung categorised the batteries into batteries by Company A and Company B. It was made clear that the initial recall was due to the defective battery from Company A. If initial reports are accurate, this means that Company A is Samsung’s own subsidiary, Samsung SDI. Leaving its other supplier, Chinese company AMPEREX Technology as company B.
Company A (Samsung SDI) Batteries
In their own investigations, Samsung found that batteries made by Company A had a localised area in which incidents occurred. This was in the top right corner of the “jelly roll” of the battery. This was due to a physical defect in the battery which led to the negative electrode being deflected. The deflection also caused the incorrect positioning of the negative electrode tips leading to an internal short circuit.
Company B (Amperex Technology) Batteries
Samsung found a localised point of short-circuiting in their investigations. They found melted copper in the negative electrode area which faced the positive tap. These marks were found to be caused by abnormally high welding burrs which were caused during the attachment process of the positive tap. These burrs were high enough that they penetrated the insulation tape and separation layers resulting in both positive and negative terminals meeting causing a short circuit. Some units of the batteries were also missing their separators increasing the chances of a short circuit.
Third Party Investigations
Third party investigations were undertaken by three companies: UL, a global independent safety science company, Exponent, an engineering and science consulting company and TÜV Rheinland, a technical testing organisation. UL and Exponent’s investigations were focused on the reported incidences while TÜV Rheinland’s was focused on the manufacturing processes and regulatory compliance of Samsung’s manufacturing facilities in South Korea and Vietnam.
UL & Exponent Findings
Both companies undertook an array of tests to determine the cause of the explosions reported by early adopters of the Samsung Galaxy Note 7. Both companies came to a conclusion that the incidents had no correlation to the smartphone’s hardware, features or software. Their investigations again pointed to the batteries which were used by Samsung in their ill-fated device.
Batteries from Company A (Samsung SDI)
Investigations by UL and Exponent on the battery made by Samsung’s subsidiary revealed that there was a physical deformity on the top right corner of all the batteries. This area was identified by both third parties as the location of the internal short circuits in all units produced. UL reported some other minor anomalies such as small bubbles or voids in the batteries and uneven stress throughout the battery. Exponent’s investigations further revealed that in addition to the physical deformities there were several other factors leading to the short circuit which include separator failure and cell faulting, and delamination (splitting) of the active materials.
The main cause of the explosions seen in the Galaxy Note 7 units with the SDI made battery was identified as the physical deformity seen in the batteries. This deformity caused the negative materials in the battery (cathode) to come in direct contact with the positive materials (anode).
Batteries from Company B (Amperex Technology)
Batteries supplied by Amperex Technology bore even worse news for Samsung. Their third party investigators found multiple defects and short circuit areas in their investigation. The representative from UL commented that these defects were “readily found” under 3D CT scan investigation. Some of the factors that were revealed by their reports include missing insulation tape on the cathode, poor alignment of insulation tape, inconsistencies in shape and dimensions of the tabs and insulation tapes and sharp edges at the terminals from welding.
While it may seem like UL and Exponent are suggesting a need for Samsung to revamp their Quality Assurance processes, the companies identified a singular cause for the explosions in the batteries. This was the sharp edges that occurred as a result of the UV welding technic which was used to attach the tabs on to the positive and negative terminals of the batteries in the Samsung Galaxy Note 7. These edges were higher than 80microns which was the extremely limited space allowed between the different layers of the battery. This resulted in the edges piercing the separators and causing the positive and negative materials to mix. Evidence of this was seen in the impressions of the welding edges on the negative terminals. This problem was exacerbated in some units where the separator was missing.
Both companies undertook device level compatibility investigations with the batteries made by Amperex. These investigations revealed that the Samsung Galaxy Note 7 showed no incompatibility issues with the battery. Exponent highlighted that the battery system of the short-lived Note 7 was designed with multiple levels of protection for the volatile Lithium ion cells. They also mentioned that these measures met the international standards for industry and some even exceeded them.
In both batteries, UL and Exponent highlight that the biggest flaw of the battery in the Note 7 laid with its design. The batteries lacked space between the negative and positive materials due to the high capacity requirement. This meant that a higher density of materials was needed to be packed into a very limited amount of space which increased the likelihood of short circuits. While the separator between the layers helped prevent such occurrences, it was highlighted that the very thin separator did little to help prevention.
While UL and Exponent focused on the battery itself, TÜVRheinland scrutinised the manufacturing processes employed by Samsung in their South Korean and Vietnam plants. In their investigations, it was found that all the manufacturing practices met international standards. In fact, they highlighted that they could not identify any specific weaknesses, concerns or obvious dangers affecting battery safety.
Samsung has said that they are taking responsibility for failing to identify and address the issues in battery manufacturing and assembly prior to the release of the ill-fated Note 7. Moving forward, the South Korean company will be taking proactive steps to ensure the safety of their devices with a broad range if internal processes to ensure battery safety and integrity. These include improved battery safety standards for materials, improved battery design allowing more space in the new bracket design to further protect the battery even when the phone is dropped and improved software measures to regulate battery charging temperature, voltage and duration.