Analysis
The Longmont facility contains a full manufacturing lab capable of producing prototype volumes of any of Seagate’s drives in a fully automated fashion. The lab itself could fill an entire article in how it goes about using robotic systems, visual feedback loops for calibration, and tracking systems able to identify not the drive batch a given disk came from but also its media tray and even the slot position within that tray. It’s mind-boggling.
However, this lab is only a microcosm of the dramatically larger manufacturing facilities located abroad. Contamination is a constant focus for Seagate drive design robustness and manufacturing processes. Despite assembly happening in rigid cleanroom conditions, there’s no such thing as perfect cleanliness. Contamination could occur from factors outside the drive as well as inside—a type of lubricant, a chemical emission from a new PCB component, and so on. Some factors lie within Seagate’s factories; others can come from outside suppliers. And remember when we talked about drives getting pulled from atmospheric test chambers for analysis? Contamination can result from atmospheric influences. If contaminants get onto the media or heads, it may prove disastrous for drive reliability.
The forensic quest for contaminants starts here, with a $1.6 million secondary ion mass spectrometer. In the simplest terms, this machine allows scientists to analyze materials from the very topmost layers of heads or media, sometimes down to only a few molecules.
When we arrived in the spectrometer lab, workers were busy examining a chemical contaminant fingerprint. Most likely, it came from one of the lubricants used within the drive. Interestingly, though, different components within the drive can use different lubricants, and each gives off a unique spectral pattern under analysis. In this way, scientists can better pinpoint the root cause of potential contamination issues.
The secondary mass ion spectrometer room stands adjacent to the particle metrology lab. Here, every particulate that can be extracted from a component gets extracted and analyzed. Workers measure quantities, but they also intensively characterize the types of particulate that are either intrinsic to the material or are present as a contaminant.
Of course, no analysis lab would be complete without a scanning electron microscope (SEM) or two. During our visit, we saw one machine taking extractions filtered out from the particle metrology lab and subsequently dried, then examined by the SEM for identification. On a different SEM, shown below, white dots are observed and identified as bits of corrosion measuring only a few dozen molecules across. These were found on heads exposed to the three-week high temperature and humidity conditions mentioned earlier.
Not all analysis is chemical. Our last leg in the analysis wing took us to the metallography lab, which essentially involves lots and lots of cross-sectioning work.
“We cross section any part, any sub-assembly,” explained one senior technician. “We even cross-section whole drives here. There are many, many reasons to do that. Oftentimes, it’s for the mechanical design team to look at tolerances off of a production part. More fun is when we’re looking at parts that have been subjected to environmental conditions that are intolerable for human beings, then figuring out the robustness of the component or the sub-assembly. Increasingly, drives are expected to perform in extreme environments. We send off drives for corrosion and pollution and heat, then we evaluate what the consequences are, to the PCBA especially. Part of our concern is about the need for a longer warranty on enterprise drives, but we also need to address markets in these inhospitable environments.”
The variety of things that can be learned through cross-sectioning is fascinating. Worker may intentionally fracture a drive to see what happens to its materials, particularly on surfaces. The PCB occupies a lot of attention, especially under chips, as do solder joints around the drive. Not surprisingly, such matters become doubly important when designing and refining the integration of new drive technologies.
In these images, you see cross-sections of a new design’s base plate. When imaged through a microscope, one can see the hairline crack splitting through a corner region. This is exactly the sort of thing engineers want remedied before completing the Design phase.
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