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| PCB black blob of glue ICs during the 70's-90's |
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| eti:
--- Quote from: RoGeorge on November 02, 2022, 02:13:10 pm ---I'm curious if those chip were of a particular technology, or if they were whatever size/technology was available back then, just that it was glued on a PCB instead of heaving their on case with pins and datasheets and everything else a standalone chip use to have. Might be a personal bias, but I think those COB (Chip On PCB) were very low power compared even with today tech (batteries in such devices used to last for 5-10+ years). What technology/size was that? Was it CMOS or something else? --- End quote --- I believer the proper term is "glob tops" |
| eti:
--- Quote from: tooki on November 02, 2022, 04:54:26 pm --- --- Quote from: Ranayna on November 02, 2022, 02:20:06 pm ---I do not remember where i read it, but supposedly labor costs in china were so cheap at some point, that the bonding and blobbing of such a chip was done by hand. And it was still cheaper than using a packaged IC. --- End quote --- There are videos on YouTube showing how it’s done. A human places the die on the PCB and loads it into the wire bonding machine, which uses machine vision to identify the bond pads and then bonds them. --- End quote --- Sure are: |
| tooki:
--- Quote from: RoGeorge on November 02, 2022, 05:17:28 pm ---I suspect those chips were less advanced, something like um rather than nm tech. I wonder how far fetched would be to do that in a DIY manner, without ordering the dies from a chip fab. It's been about 50 years since the blob chips started to be a thing, should be achievable with today DIY tech, isn't it? --- End quote --- LOL no. Even manufacturing the first generation of discrete transistors is fundamentally out of reach for DIY. Here are some videos on the history of the transistor that explain the process. The first link is a playlist of a 2.5h documentary that I highly recommend to anyone despite the length: https://youtube.com/playlist?list=PL2JLMUvYJIRI_OBwm9BW3Wh2M4GXbtDhB This one focuses on Fairchild: https://youtu.be/z47Gv2cdFtA Yes, there are one or two folks who have made transistors and extremely basic ICs on their own, but it’s extremely difficult, and difficult to do consistently. But semiconductor factories aren't called “foundries” without reason. You need ovens. Special equipment. And lots of toxic chemicals. Semiconductors are a modern miracle. It’s miraculous that integrated circuits work at all*, but the truly miraculous part is that they can be manufactured at scale and affordably, never mind at the low cost we have now. *The principles are simple. The difficulty is in actually making the damned things. The levels of cleanliness and materials purity required are absolutely mind-boggling. The silicon used in the most advanced semiconductors today (the processors in our phones and computers) has “eleven nines” of purity: 99.999999999%. That’s one atom of contaminant per 100 billion. To the best of my knowledge, there’s no other consumer product in existence that requires raw materials even remotely that pure. In one of the videos above, they told how Fairchild figured out that one reason for wildly fluctuating yield in batches of their transistors (first generation!) was determined to be whether workers had washed their hands after urinating — even though nothing was handled with bare hands. |
| RoGeorge:
Seen the videos from the playlist and added them already to this collection https://www.eevblog.com/forum/chat/fun-for-nerds/msg3297026/#msg3297026, but didn't know the Fairchild one, thanks! In the playlist they were showing about the beginnings of manufacturing germanium transistors in Japan during the 50's, and how they were controlling the purifying of the crystalline germanium rod with a pierced bucket of water and a piece of floating wood in it. ;D https://youtu.be/ihkRwArnc1k?list=PL2JLMUvYJIRI_OBwm9BW3Wh2M4GXbtDhB&t=1165 (at minute19:25) Closer to our times, DIY ICs in a garage: "Z2" - Upgraded Homemade Silicon Chips Sam Zeloof |
| SiliconWizard:
This is still used as others have mentioned. It's just basically a naked die with wire bonding directly to the PCB. For large volumes, it can be worthwhile. May also have some benefits in terms of reliability in harsh environments, at least compared to conventional SMD packages. These days, flip-chip is more common than wire bonding on PCB. It's basically a naked die with balls on the die pads and mounted like a BGA. Underfilling is also a common practice in this case to improve reliability. But back in the 70's, SMD was virtually non-existent. Hence those CoBs. Why CoBs became "popular" in small consumer electronics (such as watches and calculators) before SMD, such is history. |
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