Chips being cheap makes sense at the lithography / wafer level because sure, you can stamp out thousands of them at once. But once you need to dice them up, bond wires to them, and package them... how on earth do you do that so efficiently that each chip can be sold for fractions of a cent?
Today, it's cheaper mostly because of flip chips and Wafer Level Chip Scale Packaging (WLCSP). You build the bond pads as a normal litho step, and use a dielectric that's non-wettable between them. Then you can just use a mask to produce a grid of solder balls in the right places, drop the chip on them and put it in an oven. When the solder melts, the chip will self-align on it, so long as it's not too far off. It's uncanny to see it move.
The bonding machines are crazy. Definitely look it up on YouTube, the machine puts down bond wires super fast.
The other part of it is sheer scale. Once you start making thousands or millions of something, economies of scale drive the costs way down
This does not match my experience, although I imagine it's true in some parts of the industry. I've seen bare dice usually delivered as KGDs (known good dice -- tested at the individual level, not just the wafer level). These used to be shipped in waffle packs, but I've more recently seen blue tape used for delivery, and going straight into pick-and-place.
Not being programmable at all and just transmitting a 128 bit number would help get the size down.
Let's compare to a Monza R6 chip that was introduced in 2014, I think. This thing is 0.464 by 0.442 mm according to the datasheet, so quite a bit larger even than the 2001 read-only μ-Chip.
But it it has a two-way communication with the controller, and writable memory. You can enable password protection and such.
The newer M800 series is smaller: 0.247 mm × 0.362 mm, but still larger than the 2005 read-only μ-Chip. There are more features: fatter datasheet. Things like a privacy mode: tag remains radio silent unless it sees a specific 32 bit code from the reader.
You know how you can hold a totally unrelated RFID tag to a door reader and have the reader beep, indicating it has communicated with the tag? This looks like the feature that would prevent that. That could be useful.
So you could spray sticky rfid chips into an enemy’s hair, undetectable when scanned, and later on you could send the correct signal to identify enemies in the room. Later their hair would be trimmed, leaving no trace.
Aside from the cool privacy aspect, it seems like it would be cool to:
- Attach to insects to later use a detector to find their homes.
- Coat it and eat it to track your digestion.
- Use it in a miniature tornado model or wind tunnel along with a radio spectrograph to have cool visualizations.
- Embed in paintings, 3D models, clothing labels, and more to verify authenticity, get serial numbers, or track inventory.
- Drop a trail of them behind you so others can follow the trail and find you!
https://www.tirereview.com/michelin-connect-car-tires-rfid-2...
https://www.scientificamerican.com/article/invisible-ink-cou...
Hand waiving a lot of the details, each note basically becomes a hardware wallet with some additional features to prevent double spending.
but its still has flaws imo and just makes it a novelty rather than something practical or useful, for example unless the vendor has change, you would have to spend your btc cash denomination as a whole or exchange it for fiat. what if both the vendor & customer didn't have internet access, how would they check if the cash hasn't been used? idk if you can write back to an rfid that may solve some problems
Is there any way I can use these as general-purpose HSMs outside of bitcoin/cryptocurrency contexts? Just as a novelty.
Let's say I just want to store a private key on it and use it for SSH/etc authentication - would that be possible?
Here's a video.
The tags got cheaper and you can even get tags that are intentionally designed for metal surfaces. Unlike NFC (or barcodes, obviously), you can read hundreds of tags essentially simultaneously. But because the reading is far from being perfectly reliable (one thing we found out is that human body blocks the 868MHz RFID completely, even at something like 50dBm EIRP, which is well above what is considered safe for human presence) the applications are indeed somewhat limited.
But apparently there are two classes of applications where this technology is really common: libraries and bulk checkout at sports equipment retailers (seems oddly specific). Both of these things also benefit from the "advanced" features of UHF RFID tags like dual-mode RFID/EAS tags and ability to permanently deactivate the tag by simple command.
https://www.huayuansh.com/uniqlo-global-stores-applied-rfid-...
