SD, SM, MS, etc. sockets

D Yuniskis wrote:

> Hi Vladimir,
> 
> Vladimir Vassilevsky wrote:
> 
>> D Yuniskis wrote:
>>
>>> I'm now thinking about putting "consumer" flash memory
>>> devices in a design in lieu of equivalent components
>>> soldered onto the PCB.
>>> The point is, this is done AS IF it was a permanently
>>> attached device.  I.e., imagine fab'ing the board,
>>> slipping an SD card into the socket, and then encasing
>>> the entire assembly in a sealed box (so the SD card is
>>> socketed yet never removed).
>>
>>
>>> Anyone with any experience in this regard?  
>>
>> Once we did exactly that for an industrial device. Even if you secure 
> 
> 
> Which technology did you use?

Compact Flash.

>  I.e., I would expect SD and SM
> to have different issues as a consequence of their physical
> characteristics.

BTW, there is a considerable difference in the reliability of the cards 
depending on particular make.

> How was the "media card" used by the application?

Cards were used for raw data storage. Hundreds of files, gigabytes of 
data, sustained write ~several MB/sec. Environmental: shock and 
vibration, temperature variations. Unsupervised operation in outdoor 
conditions.

   I.e.,
> *booting* off it but otherwise executing out of RAM places
> infrequent demands on it.  OTOH, using it in a datalogger
> would place *continuous* demands on it.

Yes.

> Did you use any special selection criteria when picking the
> socket?  Or, just some run-of-the-mill part for consumer
> devices?

Tried several TH and SMT sockets, looking for best quality of contacts 
and overall mechanical robustness.

>> the card and socket with additional straps, the socket + card assy 
>> remains one of the least reliable places. It is also prone to 
> 
> 
> Yes.  But, what sorts of failures did you encounter?  Problems
> because folks "played" with the parts (because they *looked*
> like they were removable)?  Failures of the connections over
> time (oxidation, biological agents, etc.)?  Intermittent
> due to things like vibration?

Random problems in connection card<->socket and socket<->board.
Cured by replacement of card and socket.

>> we changed to the bare NAND flash soldered 
>> directly on the board, and that was heck of a lot better.
> 
> 
> That's what I would expect.  Though I'm not sure how to put
> a "figure" on "heck of a lot better".

Card failure was one of the common problems; no such issue with ICs 
soldered on the board.

   :<  Removable media
> offers some advantages (i.e., it can be replaced/upgraded
> over time so you don't end up replacing the entire device)

Removable media works fine for tabletop conditions; however it is 
difficult to design a removable media that should work reliably in the 
field.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

news@rblack01.plus.com wrote:
> In article <hj6dcs$3st$1@speranza.aioe.org>, not.going.to.be@seen.com 
> says...
>> Hi,
>>
>> I don't like using sockets in products.  They add to
>> cost, decrease reliability, tempt customers to "play"
>> with the device(s) in those socket(s), etc.  So, most
>> of the things I work on simply can't tolerate them
>> (either for reliability or "regulatory" requirements).
>>
>> But, the sockets I *have* used in the past have always
>> been for *components* that would otherwise be soldered
>> onto the PCB.  And, were of high enough quality that
>> I didn't fear the socket+device failing.
>>
>> I'm now thinking about putting "consumer" flash memory
>> devices in a design in lieu of equivalent components
>> soldered onto the PCB.  E.g., mount an SD socket and
>> use an SD *module* (or other media choices).
>>
>> The point is, this is done AS IF it was a permanently
>> attached device.  I.e., imagine fab'ing the board,
>> slipping an SD card into the socket, and then encasing
>> the entire assembly in a sealed box (so the SD card is
>> socketed yet never removed).
>>
>> But, I'm not sure that these types of sockets are
>> really intended for this type of long term use.
>> I.e., do they *expect* frequent insertions and removals
>> to wipe the contacts clean periodically?
>>
>> Anyone with any experience in this regard?  And, any
>> preferences to a particular technology that would be
>> least likely to cause problems when used this way?
>> (not sure what criteria would need to be maximized,
>> there).
>>
>> Thanks!
>> --don
> 
> We have just done exactly this - micro-SD card in a socket on the board, 
> to hold calibration data.
> The card and socket contacts are both gold-plated, so I'm not expecting 
> any problems.  Other contact materials, I'd be a bit wary.
> 
> Lots of embedded-PC-based systems (including ours) boot from a Compact 
> Flash card.  These usually have gold-plated contacts on both sides; our 
> oldest machines have been in the field for about 5 years with no 
> problems in this area.
> 
> HTH
   Check.
   Solder "plating" on PCB fingers and tin socket contacts last roughly 
2 years before a likely failure - which can be fixed by unplugging and 
re-insertion.

In comp.arch.embedded news@rblack01.plus.com wrote:
> Lots of embedded-PC-based systems (including ours) boot from a Compact 
> Flash card.  These usually have gold-plated contacts on both sides; our 
> oldest machines have been in the field for about 5 years with no 
> problems in this area.

One of the new Freescale ARM CPUs has an SD interface for flash, and enough
logic in it to be able to boot from SD.  So you can have (micro) SD as the
only nonvolatile storage on the board.  

I know one consumer device (the Chumby One) that does just this.  It has
hidden microSD inside - accessible if you unscrew it from the board, but
otherwise intended to be hidden (the idea is easier user fixing of
problems... brick your box?  Just pop the firmware card in a Linux box and
run 'dd')

Theo

On 20/01/2010 23:28, Theo Markettos wrote:
>
> I know one consumer device (the Chumby One) that does just this.  It has
> hidden microSD inside - accessible if you unscrew it from the board, but
> otherwise intended to be hidden (the idea is easier user fixing of
> problems... brick your box?  Just pop the firmware card in a Linux box and
> run 'dd')

http://www.ifixit.com/Teardown/chumby-one/1614/1

-- 
Adrian C

Hi Vladimir,

[attributions elided]

>>> Once we did exactly that for an industrial device. Even if you secure 
>>
>> Which technology did you use?
> 
> Compact Flash.

Wow!  And you had problems with that?  I would have thought the CF
connector to be more reliable than SD, MS, SM, etc.  Though CF's
tend to also be more massive which might make vibration more of
an issue...

>> How was the "media card" used by the application?
> 
> Cards were used for raw data storage. Hundreds of files, gigabytes of 
> data, sustained write ~several MB/sec. Environmental: shock and 
> vibration, temperature variations. Unsupervised operation in outdoor 
> conditions.

So a pretty hostile environment?  I might be able to win, there,
as these *should* see nothing more than temperature extremes
(~60C ambient).  If I open source the design, then folks may
actually *welcome* the "memory card" approach.  :-/  I'll
have to think hard about the consequences for *my* uses...

>> Did you use any special selection criteria when picking the
>> socket?  Or, just some run-of-the-mill part for consumer
>> devices?
> 
> Tried several TH and SMT sockets, looking for best quality of contacts 
> and overall mechanical robustness.

But, this was a datalogger so the card was (frequently?) removed
and reinserted (?).  I.e., what if it had been plugged and left?

>> Yes.  But, what sorts of failures did you encounter?  Problems
>> because folks "played" with the parts (because they *looked*
>> like they were removable)?  Failures of the connections over
>> time (oxidation, biological agents, etc.)?  Intermittent
>> due to things like vibration?
> 
> Random problems in connection card<->socket and socket<->board.
> Cured by replacement of card and socket.

And this wasn't related to insertion/removal fatigue?

>   :<  Removable media
>> offers some advantages (i.e., it can be replaced/upgraded
>> over time so you don't end up replacing the entire device)
> 
> Removable media works fine for tabletop conditions; however it is 
> difficult to design a removable media that should work reliably in the 
> field.

Hi Mark,

Mark Borgerson wrote:
>> I'm now thinking about putting "consumer" flash memory
>> devices in a design in lieu of equivalent components
>> soldered onto the PCB.  E.g., mount an SD socket and
>> use an SD *module* (or other media choices).
>>
>> The point is, this is done AS IF it was a permanently
>> attached device.  I.e., imagine fab'ing the board,
>> slipping an SD card into the socket, and then encasing
>> the entire assembly in a sealed box (so the SD card is
>> socketed yet never removed).
>>
>> But, I'm not sure that these types of sockets are
>> really intended for this type of long term use.
>> I.e., do they *expect* frequent insertions and removals
>> to wipe the contacts clean periodically?
>
> Many cell phones use micro SD cards for music and
> picture storage.  They often put the music on
> through a USB connection.  The pictures are often
> taken and sent out via the phone.   I've never
> removed the 2GB sd micro in my phone, but it
> still works fine after more than a year.

Yes.  I think cameras are probably a more "abused"
device in this regard.  E.g., I do a remove/insert
cycle each time I use one of my cameras.  But, they
are SD, MS (I've since discarded the SM camera).
I think my phone has a mini SD (not micro)

> A lot of digital cameras use SD memory and have the
> capability to upload the photos via high-speed
> USB.  The card may stay in the camera for many
> months at a time.

I have found it easier to remove the card.

But, even if the card sits in the camera for ages,
it *can* be removed to "freshen" the connection.
What if removing the card is complicated (e.g.,
imagine your oceanographic probe spending a few
*years* under water)

> I came to the conclusion a few years ago that SD
> and SD micro sockets were OK for data storage,
> and have incorporated them in a number of
> data loggers.  Before that, I had only used
> CF cards for storage---but they had worked out OK.
> 
> I'll add the disclaimer that I'm using the
> SD and SD micro cards primarily in oceanographic
> data loggers.  The loggers are in sealed pressure
> cases, so dust and humidity are not an issue.

But, they aren't filled with inert gases, are they?
(i.e., there still is *some* atmosphere that they
are exposed to)

> (If anything gets wet, it's generally a catastrophic
> failure!).

A wee bit of a leak...  :>

Hi Theo,

Theo Markettos wrote:
> In comp.arch.embedded news@rblack01.plus.com wrote:
>> Lots of embedded-PC-based systems (including ours) boot from a Compact 
>> Flash card.  These usually have gold-plated contacts on both sides; our 
>> oldest machines have been in the field for about 5 years with no 
>> problems in this area.
> 
> One of the new Freescale ARM CPUs has an SD interface for flash, and enough
> logic in it to be able to boot from SD.  So you can have (micro) SD as the
> only nonvolatile storage on the board.  
> 
> I know one consumer device (the Chumby One) that does just this.  It has
> hidden microSD inside - accessible if you unscrew it from the board, but
> otherwise intended to be hidden (the idea is easier user fixing of
> problems... brick your box?  Just pop the firmware card in a Linux box and
> run 'dd')

But, what if they solvent welded the case shut?

E.g., you can find wireless routers that have PCMCIA wireless
cards buried within.  You *know* they aren't expecting anyone to
remove that device but just opted to take that approach for
whatever manufacturing/availability reason...

"D Yuniskis" <not.going.to.be@seen.com> wrote in message 
news:hj88mi$vam$3@speranza.aioe.org...
> E.g., you can find wireless routers that have PCMCIA wireless
> cards buried within.

Mini-PCI WiFi cards seem popular in routers too -- even in brands like Netgear 
where they're going after very high volume markets and you'd think it'd be 
cheaper for them to just solder down the chips.

Hi Joel,

Joel Koltner wrote:
> "D Yuniskis" <not.going.to.be@seen.com> wrote in message 
> news:hj88mi$vam$3@speranza.aioe.org...
>> E.g., you can find wireless routers that have PCMCIA wireless
>> cards buried within.
> 
> Mini-PCI WiFi cards seem popular in routers too -- even in brands like 
> Netgear where they're going after very high volume markets and you'd 
> think it'd be cheaper for them to just solder down the chips.

Yes.  This sort of thing is counterintuitive to me.
Which makes me second guess my initial assumptions.

Of course, with wireless stuff, they may simply be
"buying the certification".  Especially on the short
term.

<shrug>  Dunno.  The economics and the practical
aspects are often out of sync...

In article <hj8826$uo8$1@speranza.aioe.org>, not.going.to.be@seen.com 
says...
> Hi Mark,
> 
> Mark Borgerson wrote:
> >> I'm now thinking about putting "consumer" flash memory
> >> devices in a design in lieu of equivalent components
> >> soldered onto the PCB.  E.g., mount an SD socket and
> >> use an SD *module* (or other media choices).
> >>
> >> The point is, this is done AS IF it was a permanently
> >> attached device.  I.e., imagine fab'ing the board,
> >> slipping an SD card into the socket, and then encasing
> >> the entire assembly in a sealed box (so the SD card is
> >> socketed yet never removed).
> >>
> >> But, I'm not sure that these types of sockets are
> >> really intended for this type of long term use.
> >> I.e., do they *expect* frequent insertions and removals
> >> to wipe the contacts clean periodically?
> >
> > Many cell phones use micro SD cards for music and
> > picture storage.  They often put the music on
> > through a USB connection.  The pictures are often
> > taken and sent out via the phone.   I've never
> > removed the 2GB sd micro in my phone, but it
> > still works fine after more than a year.
> 
> Yes.  I think cameras are probably a more "abused"
> device in this regard.  E.g., I do a remove/insert
> cycle each time I use one of my cameras.  But, they
> are SD, MS (I've since discarded the SM camera).
> I think my phone has a mini SD (not micro)
> 
> > A lot of digital cameras use SD memory and have the
> > capability to upload the photos via high-speed
> > USB.  The card may stay in the camera for many
> > months at a time.
> 
> I have found it easier to remove the card.
> 
> But, even if the card sits in the camera for ages,
> it *can* be removed to "freshen" the connection.
> What if removing the card is complicated (e.g.,
> imagine your oceanographic probe spending a few
> *years* under water)

The CF versions have spent up to 9 months underwater--but only
collected data for about 6 months because of battery
life.

The SD card versions are heading for moorings on the
equator this summer.   I'm hoping that gold-on-gold
contacts, and a dry temperature-stable environment will
prove reliable.
> 
> > I came to the conclusion a few years ago that SD
> > and SD micro sockets were OK for data storage,
> > and have incorporated them in a number of
> > data loggers.  Before that, I had only used
> > CF cards for storage---but they had worked out OK.
> > 
> > I'll add the disclaimer that I'm using the
> > SD and SD micro cards primarily in oceanographic
> > data loggers.  The loggers are in sealed pressure
> > cases, so dust and humidity are not an issue.
> 
> But, they aren't filled with inert gases, are they?
> (i.e., there still is *some* atmosphere that they
> are exposed to)
> 

Many instruments and loggers are flushed with dry
nitrogen or argon before they are sealed  to avoid
condensation. They generally get assembled at about
20C, but spend most of their logging time at 5 to 10C.
> > (If anything gets wet, it's generally a catastrophic
> > failure!).
> 
> A wee bit of a leak...  :>
> 
It doesn't take much salt water when there are a few
volts across  the pins.

The worst situation is when there is enough water in the
case with the batteries to generate some gases.

Back in the 70's  a leaky case generated enough
hydrogen  that a friend was injured when opening
the pressure case.   I once opened an instrument
that had been on a mooring for several months and
it started hissing as I loosened the screws.  I
set it down and left the room for 24 hours.  After
that we added some pressure relief capability
to the design.

Two pounds of lithium batteries and 3 ounces of
salt water is a scary combination!

Mark Borgerson