NAND flash package economics

I suspect the answer to this one is 'stop asking stupid questions', but here goes anyway...

When a top-of-the-line flash chip comes out, does anyone happen to know what the economics dictate the common package format is? A lot of them come in TSSOP, BGA and possibly bare dice/chip-scale packaging of some kind.

What I'm trying to do is get hold of a few-off of fast, high density NAND flash chips in TSSOP48. The distributor is going to laugh, or ask for a million dollars. But if I go to the corner shop I can buy USB sticks for the commodity prices of the flash. I'm quite prepared to saw off the end and unsolder the chip, but I'd like to make an informed guess at what's going to be inside before I start buying every model under the sun.

So, for example, bare dice could come out first and be the first to be integrated into products (micro SD can be nothing but bare dice, for example). Or, on the basis that large capacity USB sticks tend to start large and shrink over time, they could come out in TSSOP (bigger die sizes) and then move to BGA after process shrink. Or they could be BGA all the time but need multiple chips initially which makes the enclosure bigger. Since it's NAND, the pinout doesn't change with capacity (unlike NOR, SRAM, DRAM, etc).

Anyone have any feelings? My guess would be the wind's blowing strongly in favour of BGA but it puzzles me because I still see a lot of TSSOP48 around (in routers, dev boards, etc). Or is TSSOP48 the province of small and old chips?

Thanks Theo

Reply to
Theo Markettos
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NAND dice are physically large and have relatively few I/O. This maps well to TSSOP.

Example: These mSATA SSDs are new(ish) and use TSSOP for the NAND and BGA for the controller:

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Regards, Allan

Reply to
Allan Herriman

Not what you're asking, but: have you considered just putting a micro SD socket on your board?

Unless your production numbers are huge, it'll make your product that much more future-proof.

And if your production numbers _are_ projected to be huge, you may be able to get samples out of the manufacturer or distributer.

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Reply to
Tim Wescott

This is a retrofit to any existing board that has both a nice set of pads for a NAND and a spare port on the SDIO controller. But the interest in NAND is the low latency, because I want to use this as swap[1]. MicroSD tend to be slow (MLC?) devices, while the fast SLCs as used in SSDs have much lower erase times (which I think is the killer for use as swap, and where a swap system that can do lazy erasing could come in handy).

My volume is about three ;-)

Theo

[1] I've done this before with USB sticks and it does work... flash wear isn't a problem over a few years of constant hammering. And there's even a Linux driver for using raw flash as swap: mtdswap.
Reply to
Theo Markettos

Thanks, that's useful to know.

I'd seen various SSDs using TSSOP but wasn't sure on how new they were (various 16GB stuff on ebay, using 4x TSSOP). So that's a helpful newer data point...

Theo

Reply to
Theo Markettos

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