Comment by pjc50

Comment by pjc50 3 days ago

> market failure

Industrialization has massively optimized the "hot path" for any kind of production, largely by taking out the humans. It is incredibly cheap to manufacture consumer electronics - because everything is standardized and predictable and amenable to machine operation. This is what market success looks like.

The downside is that as soon as there is a deviation from the process, it gets more expensive.

It's worth thinking about what happens to repair inside the factory. Some percentage of units will be coming off the production line defective and fail initial QA. This is usually a very low percentage, well below 1%, because the entire economics of the factory depends on not having to do any rework. Even there, the technicians will take a look, determine if it's something that can be fixed quickly, or is a novel kind of failure, and if not just throw it away right there. Why? Because while you're standing there looking at it, another hundred have come off the production line. The broken one in your hand is not a unique snowflake.

At the start of a run though, this is an interesting and important job, because any failure is a novel failure. The first batch through the process should have high yield, but it might not, and then you stop the line ( https://mag.toyota.co.uk/andon-toyota-production-system/ ) and figure out what's happened (something misaligned? Defective inputs? Material problems? Design issue?)

The first batch will often get reworked and sent out as demo units.

KeplerBoy 3 days ago

What happens when a unit is defective and not easily repairable, maybe because the PCB itself was already defective?

Do technicians salvage the high value components, like the CPLD in this case, off the board? That chip alone is probably worth 15$.

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pjc50 3 days ago

As other commenter says, spending human time to save a $15 chip is uneconomic. This only happens if they're especially expensive parts or (as during COVID) supply is short and you can't just buy some more.
(COVID shortages saw the opposite phenomenon in a few places: working consumer electronics being bought and stripped for a particular part critical to something else, then the rest thrown away!)
Remember that after you've hotgunned it off the board and cleaned the solder you have to re-ball BGA parts. Again, a process that's cheap in the original manufacturing line and very hard to do by hand. It also means the part has been through more thermal stress which will shorten its life. You don't want to have to rework a unit again if you put a recycled chip in it which fails.

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ElectricalUnion 3 days ago

The engineering time to "salvage" and test the 15$ chip, and the cost of downtime reintegrating the part to the production line is probably worth more that 15$, so unless the lack of that specific part is a bottleneck, probably no?

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- KeplerBoy 3 days ago
  
  Yeah, probably, but I do wonder where it starts to make sense to desolder a chip and give it another try.
  Surely at the point of high end GPU Boards one would invest considerable amounts of time and money to salvage a chip, which could sell for thousands of dollars.
  
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  coldpie 3 days ago
  
  I think you're right that for high end chips, it is worth the time to salvage it[1]. But I think that's the vast minority, like you said, most stuff being manufactured isn't at the cutting edge of consumer tech like GPUs are.
  [1] They show a bit of the RMA/failed unit process towards the end of this surprisingly good GPU factory tour from Linus Tech Tips. There's some discussion of de-soldering and testing retrieved components. https://www.youtube.com/watch?v=GS35VHEfFDU
  
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xnzakg 3 days ago

Not the user you replied to from my experience usually it's not worth it due to several reasons:
- desoldering the chips takes time and is a manual process ($), with risk of tearing off a pad or bending leads. In case of BGA ICs reballing is needed to reuse them. - components are usually not rated for a lot of reflow (heat/cool) cycles, and some are moisture-sensitive and may crack if they have managed to absorb moisture - you usually end up with some solder and flux left on the IC, which can cause issues - ICs come on tape for feeding into automated pick-and-place machines, so you would need to feed and mount them manually ($)
And if you only realize you have damaged the IC after mounting it on the new board you end up having to rework it again ($).
Sure, it might be worth it if the chip is really expensive or hard to get, or you're soldering everything by hand anyway, but usually the math just doesn't work out.

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