Following months of speculation, Samsung's DJ Koh, President of Mobile Communications Business, announced today at a press conference in Seoul, the results of their internal investigation around the cause for the Note 7 explosions and other technical issues. He began his remarks by apologizing and expressing his gratitude to note 7 customers, business partners and operators for their patience and continued support. Koh promised that Samsung is taking active steps to prevent similar issues in the future.

Faulty battery design and workmanship by manufacturers are root cause of Note 7 issues

The announcement reflected on pressures from high consumer demand for a larger cell phone which pushed Samsung to rush and produce larger batteries. Samsung manufactured its own battery for the first Note 7, referred as Battery A in the report, which was revealed that its design flaws unintentionally allowed the positive and negative electrodes to touch resulting in fires. When customers complained about exploding Note 7's, the company recalled the phones and sent out the battery manufacturing to a Chinese manufacturer, Amperex Technology, to create Battery B in hopes of swiftly resolving the issues but unfortunately introduced further problems.

The report found that abnormal left over welding bumps from the result of poor workmanship, caused fires with Battery B when the bumps created a direct contact with the positive tab and the negative electrode.

Independent investigations come to same conclusion

At the Samsung press conference, executives from UL, Exponent and TUV Rheinland, leading independent industry groups were also at hand with results of their own investigations.

UL's failure analysis report states "One major failure mechanism for field incidents is likely: The combination of (1) missing insulation tape + (2) sharp edged protrusions on tab + (3) thin separator, all leading to a high possibility of an ISC between cathode tab and anode, subsequently resulting in heating and fire." Exponent's failure analysis report concludes that the main cause was from "the damage was caused by a cell pouch design that provided inadequate volume to accommodate the electrode assembly."

Cause of exploding cell phones

In October 2016, Applied Energy Hub released the results of their investigations on exploding cell phones.

They state on their website that the battery electrodes are separated by a layer of non-conductive polymer which is solely to prevent the electrodes from contact. When electrodes do contact each other, an internal short circuit occurs where the battery releases a large part of stored energy which causes overheating and leads to fire or explosion.