Electronics > Beginners
Chip making process
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coppice:

--- Quote from: Wimberleytech on October 16, 2018, 06:08:33 pm ---
--- Quote from: ZeroResistance on October 16, 2018, 06:01:12 pm ---
--- Quote from: Wimberleytech on October 16, 2018, 05:48:35 pm ---
To work with a foundry, you will have to commit to many thousands of wafers in production.

--- End quote ---
So did you have to commit for like 5000 wafers?

--- End quote ---
That is a detail I do not recall.  I would think at least 1000 wafers/month.  A foundry is in the speculation business.  They will make a bet on your viability.  If they believe in your business plan, they will be willing to do much smaller quantities while betting on the future large volumes.

--- End quote ---
A foundry will happily process a single wafer for you. The price won't be the same as when you run a thousand wafers a month, though.
ZeroResistance:

--- Quote from: Wimberleytech on October 16, 2018, 06:08:33 pm ---
--- Quote from: ZeroResistance on October 16, 2018, 06:01:12 pm ---
--- Quote from: Wimberleytech on October 16, 2018, 05:48:35 pm ---
To work with a foundry, you will have to commit to many thousands of wafers in production.

--- End quote ---
So did you have to commit for like 5000 wafers?

--- End quote ---
That is a detail I do not recall.  I would think at least 1000 wafers/month.  A foundry is in the speculation business.  They will make a bet on your viability.  If they believe in your business plan, they will be willing to do much smaller quantities while betting on the future large volumes.

--- End quote ---
Ok so that makes it 1000 * $1600  per wafer or USD 1.6M per month. But you also do get 15000 dies per wafer or 15000 * 1000 = 15M dies per month.
So per die cost is 15000/1600 that is around $0.11. Seems to be pretty good for a 10F.
But Microchip need to have assured sales right for it to be profitable?
Another issue for Microchip 15M chips per month is a lot, how will they sell that much, they may probably have another deal with the foundry?
jmelson:

--- Quote from: ZeroResistance on October 16, 2018, 04:00:10 pm ---
--- Quote from: srce on October 16, 2018, 01:57:39 pm ---You will get the dies from Europractice in a little tray like this:


--- End quote ---
Whats the problem in soldering the die directly to a pcb? are the bond pads too small that they can't be soldered directly to the board, similar to a LGA package? And then pour epoxy on it similar to a COB package. Like many chinese items have.

--- End quote ---
The bonding pads are something like 40 um square and aluminum.  Not likely you can solder to that!

Jon

coppice:

--- Quote from: ZeroResistance on October 16, 2018, 05:47:17 pm ---Do foundries have a minimum wafer quantity. I mean wemberlytech showed cost of a wafer as USD 1600. So do the foundries expect you to order something like 100 wafers.
And if each wafer has 15000 dies on it. Do the foundries also charge you per die on that wafer.
I guess it should have been area based, if a wafer is 200mm in dia that comes to 31400mm^2. So Do they charge on area of silicon?

--- End quote ---
In general a foundry doesn't care what is on a wafer. They just process the wafer according to the mask set, ship it to the customer, and charge the agreed wafer price. If the wafer processing went OK, and the number of good die is pretty much in line with expectations, that's the end of the story. If the wafer wasn't processed well, and the yield of good die is low, arguments may ensue. If a large number of wafers have a low yield these arguments might get rather heated.  :)
jmelson:

--- Quote from: ZeroResistance on October 16, 2018, 04:54:34 pm ---
--- Quote from: coppice on October 16, 2018, 04:38:58 pm ---You need to test a wafer, to locate the good dies. Then you package the good dies. Finally you need to test again, to make sure the packaging went OK.

--- End quote ---
If a wafer has 100 dies on it what would be the typically percentage of good dies?

--- End quote ---
On one of our designs, we got close to 100% yield, on another we got more like 60%, although the issues were subtle.  That problem was a threshold shift in a chain of amplifiers, a bit of a risky design.

Jon
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