President Mobile Communications Business at Samsung Electronics Dong-jin Koh announced for the nth time that he was sorry and thankful to his manufacturer partners, retailers and customers.

At a press conference just wrapped up, Koh and representatives of independent investigators detailed the process into finding out why dozens of Galaxy Note 7 units exploded, causing the phone to be entirely recalled.

The company’s internal investigation involved the testing of features like fast charging, wireless charging, USB-C electrostatic vulnerability, the iris scanner’s operation and user software.

“None of these tests an abnormality or correlation to the reported incidents,” Koh said through a translator.

The company claimed that its inspection into the step-by-step manufacturing and logistics process found no abnormalities as well.

Through large-scale charge cycle testing that involved 200,000 devices and 30,000 batteries, the company found that batteries as well as fully assembled devices were malfunctioning at the approximately the same rate as in the population.

Investigating Note 7 units from the first recall made on September 2, Samsung found that one cell of the lithium-ion battery in affected units had a deflected or bent corner. One common aggravating factor found was that the negative electrode tip was misplaced.

One other cell obtained after the second recall took effect was victim to short circuiting and thermal overrun because of welding issues that led to the clashing of the positive and negative layers. Some units lacked the required insulating tape between the layers.

United Laboratories was one of three independent firms looking into the companies that manufactured the batteries — Samsung SDI and China’s Amperex Technology.

Comparing exploded batteries to analysis of new batteries before and after use, UL found results consistent with Samsung’s investigation — but it pushed three causes of explosions to the fore for “Company A”:

  1. The manufacturing and/or assembly line may be at fault for the deformation of the first cell.
  2. The design of the battery included a thinner insulation layer between the positive and negative electrode layers and little tolerances for defects. That combined with a high-capacity package made it more explosion-prone.
  3. Combining both of the above with regular charge cycling and the stresses may have proved too much for any separation of the positive and negative layers of the battery to be effective.

United Laboratories claims more investigation is needed on how the deformation of the corner comes about.

With regards to explosions involving batteries from “Company B,” there were two major factors:

  1. Common manufacturing issues found included missing or misaligned insulation tape and shoddy welding of the positive tab that led to positive and negative electrodes meeting and causing thermal runaway.
  2. There’s concern over the battery’s design as explained in the brief for Company A.

Failure events came about within Samsung’s maximum operating limits for the batteries.

Another lab, Exponent, also published investigation results with similar findings. TÜV Rhineland inspected the manufacturing and logistics process within Samsung Electronics and found no cause of fault.

Samsung is enacting remedial measures in the wake of this incident. It will further checks on manufacturing processes, including an eight-point battery check and revised battery hardware and software standards.

We’ll embed the full press conference from Samsung if it becomes available on YouTube.

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