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Comment by formerly_proven | Hacker News Reader

> The electronics seemed to be fabricated using bare dies attached to some substrate, probably to lower cost and improve reliability at higher temperatures. The board is made up of two parts, a low-power part with the CPU and CAN transceivers, and some high-power part with 6 MOSFETs forming a three phase H-Bridge.

> https://blog.willemmelching.nl/images/vw/IMG_3181.jpg

It doesn't really look cheap to me (large machined surfaces on the cast aluminium casing, two ceramic PCBs, everything connected with wire bonding, even the motor windings and the external connector, which means that at least those bonds are carried out on an almost completely assembled product; also look at the sheer size of the motor bonds) but it does look very reliable - everything is bonded or welded, zero connectors, no fasteners, all solid state.

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Yeah, it looks like it's extremely optimised for reliability. The construction reminds me of some of the space stuff I'd seen made by a company I worked for (it was all done before my time though).

It probably wouldn't be incredibly expensive in this case (automotive) because all the wire bonding and tab welding can be automated, but clearly cost isn't the main concern behind the design!

Automotive has quite broad temperature and vibration requirements and is supposed to work for 15 years+ so it makes sense to pick something like this.

I'm really surprized this is reliable (of course they know what they are doing). Maybe because all the wirebonds to the dies are encased in epoxy (?) and the other bonds are so thick. Even then I would be worried they would snap off or lift their pads.

I wasn't directly involved but I still have nightmares about wirebonding. For a large partice physics experiment, we bonded electronics to silicon (wafer) sensors. Those small bonds would start oscillating and break as soon as there was any noise with their resonance frequency. It took cooling and heating cycles also pretty badly. In the end they sorted out all problems somehow, but the association "wirebond = delicate" stuck with me.

This isn't epoxy, it's some sort of sticky soft coating. Wirebonds looks fragile to me too, but after all every packaged chip have wirebonded pins, so at least it shouldn't be worse.

It’s called conformal coating.

This also makes the component prone to lights. All in all, very exotic and interesting.

Recently I opened up a Mitsubishi Electric power steering unit, and while mine looked a bit like a parallel world Enterprise, this one looks like Enterprise with a suffix couple alphabets later than the one in the intro. Mine was just a two PCB build of a logic board with Fujitsu microcontroller and a power board with an H bridge and input/output emergency isolation MOSFETs.

I agree but if that was in the world of consumer electronic it would have been frowned for repairability.

Yeah, if some power transistor fails these things are nightmare to repair, eg. https://www.youtube.com/watch?v=133qU9sMatA

Ferrari used this method for their ECUs in the 360 to reduce risk of damage from vibration and heat.

Ah, so they're designed to be on fire.

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