Official Galaxy Note 7 investigation blames small battery cases, poor welding
Two different production problems from two different suppliers killed the Note 7.
Three months after its largest-ever recall, Samsung has finally completed its investigation of the Galaxy Note 7 fiasco. The high-profile flagship phone was recalled (twice) and canceled after reports of explosions and fires, and now Samsung thinks it has finally nailed down the issue.
Samsung’s verdict: two separate battery construction issues were to blame. Samsung Electronics used two separate suppliers for the Galaxy Note 7—Samsung SDI, a sister company in Samsung Group, and Amperex Technology Ltd (ATL)—and it turns out both manufacturers had their own issues. Given that Samsung’s first recall and attempted fix didn’t work, it’s no surprise that the problem behind the Galaxy Note 7 is a complicated one.
What went wrong
In its report, Samsung refers to the battery manufacturing partners in generic terms—possibly to help those partners save face. This “Battery A,” “Manufacturer A” obfuscation really won’t fool anyone who is paying attention, since Samsung identifies “Battery A” as “from the first recall,” and the first recall exclusively targeted batteries made by Samsung SDI.
For the Samsung SDI batteries, Samsung’s investigation determined that the corner of the battery casing was too small, which resulted in the negative electrodes in the corner of the battery being bent. This made it easier to short-circuit the battery and cause a “thermal runaway” situation where the battery explodes or catches fire. Exponent, one of the consulting companies in Samsung’s investigation, said that this “unintended damage was present in all of the cells examined by Samsung and Exponent.” This means that in the first round of Galaxy Note 7s, nearly 100 percent of devices were defective. (Think of that as a one-more-time warning for the 4 percent of Note 7 customers who still haven’t returned their devices.)
Samsung also identified an “additional contributing factor” with Battery A: the negative electrodes were too long, which led to them being bent in the curve on the long side of the battery.
With the first recall underway, “Battery B”—which previous reports said was manufactured by ATL—was used in all the replacement Galaxy Note 7s. Battery B didn’t have any of the Battery A defects; it had a defect all its own. When connecting the positive tab to the battery, “Manufacturer B’s” welding process—which Exponent called “poorly controlled”—created high, sharp welding burrs. Normal expansion and contraction of the battery electrodes during charging and discharging caused the welding burrs to scrape against the insulation between battery layers. Eventually, this scraping could penetrate the insulation and short out the battery, causing fireworks.
Another “additional contributing factor” to the failure of Battery B sounds rather alarming: some batteries were missing insulation tape. The tape helped reinforce certain trouble spots, and apparently, ATL forgot to attach it to many units.
What Samsung is changing
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