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by koeng 1415 days ago
Super excited for this! Right now I’m working on a project to build open source DNA synthesis chips (if deployed right, drops DNA synthesis cost by 100-500x market price), and efabless with their tools created with Google’s support have simply enabled the project to even be possible. I am grateful to Google for doing this.
1 comments
octoberfranklin 1415 days ago
> have simply enabled the project to even be possible

Are you sure about that? The mandatory "Caravel" pad ring occupies the entire top layer of the chip as well as a ring around the edges. It hermetically entombs the design area that you control.

There is no exposed surface under your control for any kind of chemically-relevant device like a microwell.

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koeng 1415 days ago
"Thank you for reaching out to Efabless! To answer your questions, we can support requests for bare die in our QFN shuttle programs, with the next QFN shuttle having a tapeout of November 14, 2022. Also, the material that you were asking about is aluminum."

Correct me if I am wrong, this means I could do this. Perhaps I am wrong! In which case I should find a different chip supplier.

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octoberfranklin 1415 days ago
Unfortunately you are wrong.

The padframe and top metal layer which "entomb" Caravel designs are both part of the die. They are not part of the package. Omitting the package does not help you here.

You might be confusing the padframe with the leadframe. The padframe is part of the die, the leadframe is part of the package. In a QFN package they are connected to each other by extremely thin gold wires.

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koeng 1415 days ago
Thank god for people correcting me on the internet then! Can look for other providers thanks!
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koeng 1414 days ago
The answer is actually nuanced.

"From the ChipIgnite program you can get bare die; from the Open MPW program, you can't. If you submit something on a ChipIgnite shuttle run, then the pads will be exposed, along with any other places on the chip that you place overglass cuts (i.e., you can place your own pad cuts internal to the user area)."

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octoberfranklin 1408 days ago
Link?

The other problem is that even for $10,000 the ChipIgnite program won't give you a confirmed booking. You have to submit your design and then they decide if they feel like manufacturing it. Any chip worth paying $10k to fab is going to involve an engineering sunk cost of around 5 times that amount. Which is why Real Fabs take your money and give you a confirmed booking.

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