Is it okay to reflow an SX28AC/SS after it's programmed ?

Bean

This may be a stupid question...But
If I have a programmed SX28AC/SS chip, and I run it through a reflow oven could it lose the program ?
I know it's best to program them "in-system", but I want to sell pre-programmed chips.
Bean.


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"SX-Video·Module" Now available from Parallax for only $28.95 http://www.parallax.com/detail.asp?product_id=30012


Product web site: www.sxvm.com

"It's not getting what you want, it's wanting what you've got."


Post Edited (Bean (Hitt Consulting)) : 6/5/2005 4:08:33 AM GMT

Forrest

Should be no problem - I've assembled thousands of Microchip PIC's this way.

Beau Schwabe

Bean,

As forrest said, there shouldn't be a problem. The reflow process itself would not hurt the non-volatile memory this is done all of the time, and
I can't imagine the reflow process "flipping-bits". I think your safe.

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

Bean

Thanks guys, I'd heard that some EEPROM can be erased if reflowed. I wasn't sure about flash memory.
Bean.

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"SX-Video·Module" Now available from Parallax for only $28.95 http://www.parallax.com/detail.asp?product_id=30012


Product web site: www.sxvm.com

"It's not getting what you want, it's wanting what you've got."
·

Dave Paton

Generally, it's bad mojo to do it in production. I know of no major manufacturer that reflows chips after programming. All of the boards I've ever made for volume production always have a set of pads for pogo pins so that they can be programmed just before the end-of-line functional test. That said, I've never heard of a FLASH part going bad under reflow and losing it's memory either. It may be a holdover from the bipolar PROM days, but it just makes me (and my customers) feel better if the code doesn't get cooked

-dave

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This is not a sig. This is a duck. Quack.

Forrest

I've reflowed LOTS of Microchip PIC's after programming - there's no problem. I'm talking well over 100,000 chips. I'm assuming the SX processors behave the same way - but have no direct experience with them in a production environment. I'd check with Parallax - they probably program their chips before reflow when making Stamps.

Ken Gracey

Bean,

Not a problem. Our BS2SX, BS2pe, BS2px, BS2p24/40, SX-Keys, Ping))) sensors, and countless customer SX applications are programmed prior to PCB mounting. We don't tie many failures to having pre-programmed SX chips. Usually our problems lie with solder bridges, PCB manufacturing issues or improperly placed components (not failure of the SX due to pre-programming).

Funny thing is that when Ubicom was first created (as Scenix) the sales people used to tout the advantages of in-system programming of the SX. The benefits of programming a toaster on the assembly line still ring in my head. . .Most of the major applications I know of which use the SX are pre-programmed. In fact, our programming person handles several customer accounts. By the way, she just left to pursue some career goals. If you are looking for a job programming chips contact our HR department. We'll keep you out of trouble.

Bean, go for it.

Ken Gracey
Parallax, Inc.

PLJack

Ken Gracey (Parallax) said...

Bean, go for it.

I don't know if he is talking about pre-programming or the job offer.
But, just in case you are having a "slow" day, that is opportunity at the door Bean....

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Jack

Bean

Ken, Thanks for the offer. For the work, and to keep me out of trouble [noparse];)[/noparse]
I am interested and I will explore it.
Bean.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
"SX-Video·Module" Now available from Parallax for only $28.95

http://www.parallax.com/detail.asp?product_id=30012

Product web site: www.sxvm.com

"It's not getting what you want, it's wanting what you've got."
·

Dr. Mario

Yeah, I agree. Some chips has to be programmed before being chucked into the reflow oven. If you can't sleep at night, you can just read the datasheet for the flash. They're just transistors which you flip the bit, so it should survive the heat without losing the data. I would be cautious about Phase-change memory (PCM) chips, though. You're not likely to come across that thing very often anyways.

Still, if you're not satisfied yet, you can try reflow a programmed flash ROM onto the board and then read it out via Propeller or a special I2C driver module (which you read out the whole thing via PC's USB).

Just be careful around X-ray inspection, though (it won't apply to smaller-geometry flash ROM, as I have heard that few such chips are made by X-ray masked lithography or EUV lthography so it's already radiation-hardened...) Just don't do X-ray inspection on OTP memory (the EEPROM in opaque cover) at all - it's the way I erase the OTP.

Bean, you should be fine as-is. They're already designed to survive the punishment of heat without any data loss.

Leon

For large-scale manufacture it's common for chips to be supplied pre-programmed by the manufacturer or distributor, for reflow soldering during board assembly. It never causes any problems.

Dr. Mario

Yep. Except for PCM chips - they have low melting temperature in the memory cells, so checking datasheet is best.
But for other memories, I doubt it would be a problem. For some chips (such as OTP-based ROM), I just leave it unprogrammed, piror to X-ray exposure (such as radiological
BGA / SMT soldering inspection).