EMRFD Message Archive 9961

Message Date From Subject
9961 2014-04-27 21:25:18 bob_ledoux State-of-the-Art Op Amps Require A Sense of Humor

I was looking for an ultra low noise op amp for a Tayloe-based DC receiver project. I wanted something that could touch the characteristics of the LT1115, with its 0.8 nV/sqrtHz at audio frequencies. I found the ADA4898-2 which includes two amps in a SOIC package for $7.50. This is less expensive than buying two of the single circuit LT1115’s.


As a hobby builder I was a bit taken back when I received the parcel from Mouser. The single, 8 pin SOIC was packaged in the normal electrostatic protection package, but it was about an inch thick with obvious additional protective materials.


The real surprise was the label, which listed the date the package was sealed and noted the sealed bag had a 12 month shelf life. Once the bag was opened the device must be mounted within 168 hours. Additionally, based on an enclosed humidity indicator card the component might require baking according to standard IPC/JEDEC J-STD-033.


This all seemed a bit much for a guy who just wanted to build a low noise receiver. I have decided to place the package on the wall where I can show it to friends, until I find an appropriate project. In the mean time I have decided to use a slightly noisier LT6231 for my current project. Hopefully, that component will arrive in less intimidating cover.


Those of you who must deal professionally with such specs have my sympathy.


9962 2014-04-27 22:31:24 Eamon Egan Re: State-of-the-Art Op Amps Require A Sense of Humor

Hi Bob,

 

Dealing professionally with such specs is not in practice a huge issue, as there are standard procedures that are applied routinely to the handling of moisture sensitive parts when they are used in manufacturing quantities. As you have alluded to, there are even procedures to “re-bake” parts in open packages that have not been used up but which have exceeded their exposure to moisture-laden air. And many parts are packaged in individual compartments on tape reels where they don’t get popped out until shortly before being soldered.

 

I have never worried about this when assembling prototypes. Particularly for small parts it is more of a theoretical or hypothetical concern, due to the possibility of absorbed moisture boiling and cracking the package. It is more of an issue where the smallest risk of defect must be managed, as would be the case in large quantity manufacture of large circuits where a single defect is one too many.

 

I would suggest you simply ignore the warning and go ahead and use the part. If you want to get into the spirit of MSL handling, even if not adhering to the letter, just re-seal it in its original package with whatever dessicant it came with, until you’re ready to solder it.

 

My 2 cents.

 

73

Eamon

VE2EGN or AB1NK


9963 2014-04-27 22:48:09 Todd F. Carney / ... Re: State-of-the-Art Op Amps Require A Sense of Humor
Here's a link to the official AD datasheet for this device. 


There is *no* indication of special environmental, storage, or installation requirements whatsoever. Nor is there any other indication that the SOIC encapsulation is different from any other SOIC in terms of immunity to moisture, permeability to gases, or some special coating that also needs special handling. Stickers stuck on the wrapping by who-knows-who do not carry *any* weight compared to a current datasheet. That's what professionals rely on.

Personally, I suspect the labeling to be part of boilerplate ass-covering much like all those stickers you get on prescription-drug bottles cautioning you the drug might make you nauseous or sleepy, or like the labeling on a hammer that warns you to wear eye protection when using, or not to take Vicks VapoRub internally. 

I might add that what might seem like extra-special packaging may just be the standard for all solid-state devices from that vendor. One receives components in static-protection packaging all the time even for devices (such as bipolar transistors) not in the least bit static sensitive. Rather than having the shipping department distinguishing between sensitive and non-sensitive components, everything is packaged in a standard way.

Personally, I wouldn't give it a moment's thought before I used the ADA4898. 

73,

Todd
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9965 2014-04-28 05:15:42 Alberto I2PHD Re: State-of-the-Art Op Amps Require A Sense of Humor
9967 2014-04-28 06:18:21 Graham / KE9H Re: State-of-the-Art Op Amps Require A Sense of Humor
 Bob:

Those handling instructions are for high volume, high manufacturing yield processes
involving robotic assembly, trying to get their soldering errors well better than
one in a million opportunities.

For home/hobby/prototype use, just do what you need to do.

The rules are different for prototypes, versus building millions per month.

--- Graham / KE9H

==


9968 2014-04-28 06:27:50 Weddig, Henning-C... Re: State-of-the-Art Op Amps Require A Sense of Humor
Bob,

my guess is that thes precautions are necessary when doing wave or IR
soldering i.e. completrely heating the whole chip.
Any moisture which the IC might have caught up will evaporate and
probably by "exploding" within the IC damage the chip.

This big amount of heat will probably not be put onto the chip if You
use hand soldering...

At least: You can dry up the chip if You put it into some "worm"
enviroment for a longer time, but fo a hobbyist thsi precatuin may be
problematic due to the reason that he/she has not such appliances.

Henning Weddig

Am 28.04.2014 15:18, schrieb Graham / KE9H:
> Bob:
>
> Those handling instructions are for high volume, high manufacturing
> yield processes
> involving robotic assembly, trying to get their soldering errors well
> better than
> one in a million opportunities.
>
> For home/hobby/prototype use, just do what you need to do.
>
> The rules are different for prototypes, versus building millions per month.
>
> --- Graham / KE9H
>
> ==
>
>
>
9969 2014-04-28 09:27:55 David Re: State-of-the-Art Op Amps Require A Sense of Humor
I suspect this warning is related to automated soldering. Humidity absorption
by the package can cause "popcorn" failures during heating. There is nothing
special about the LT1115 which would require extra special handling.

I wonder what the difference is between the LT1115 and LT1028. They seem like
different grades of the same part.

On 27 Apr 2014 21:25:18 -0700, you wrote:

> The real surprise was the label, which listed the date the package was sealed and noted the sealed bag had a 12 month shelf life. Once the bag was opened the device must be mounted within 168 hours. Additionally, based on an enclosed humidity indicator card the component might require baking according to standard IPC/JEDEC J-STD-033.
9982 2014-04-29 05:02:14 wb9kzy Re: State-of-the-Art Op Amps Require A Sense of Humor
Fellows and Gals -

This is just a SWAG, but one other thing that might be considered is how mechanical stress brought on by surface mount manufacturing in combination with high moisture conditions would affect the various specs of a high performance linear IC.   It might not cause failure if the moisture warnings are ignored but if it changed the performance of an expensive chip into a run of the mill chip, then it'd be worth the trouble to heed the warnings.

One of the major unsung innovations which have powered modern IC production is the use of inexpensive low-stress molding compounds - they are somewhat secret concoctions, probably including volcanic sand from Japan - they have to mimic the thermal characteristics of the IC chip itself and also prevent any internal compounds from attacking the die, the bonding pads or the skinny Gold wires.

For example, one IC I've purchased with this type of anti-moisture packaging is a voltage reference chip from TI. These chips can get spendy - aren't they really just voltage regulators ? 

I can almost hear W7ZOI recommending measurements over speculation :)

73,

Chuck, WB9KZY
Jackson Harbor Press
9983 2014-04-29 05:25:33 ashhar_farhan Re: State-of-the-Art Op Amps Require A Sense of Humor
I have heard that 807's glow got better and better when exposed to fumes of certain weeds. True?
- f
Sent from BlackBerry® on Airtel

9984 2014-04-29 05:39:20 David Re: State-of-the-Art Op Amps Require A Sense of Humor
On 29 Apr 2014 05:02:13 -0700, you wrote:

>Fellows and Gals -
>
>This is just a SWAG, but one other thing that might be considered is how mechanical stress brought on by surface mount manufacturing in combination with high moisture conditions would affect the various specs of a high performance linear IC. It might not cause failure if the moisture warnings are ignored but if it changed the performance of an expensive chip into a run of the mill chip, then it'd be worth the trouble to heed the warnings.
>
>One of the major unsung innovations which have powered modern IC production is the use of inexpensive low-stress molding compounds - they are somewhat secret concoctions, probably including volcanic sand from Japan - they have to mimic the thermal characteristics of the IC chip itself and also prevent any internal compounds from attacking the die, the bonding pads or the skinny Gold wires.

They probably go to some length to avoid anything immediately volcanic to
prevent bit flips cause by radiation from package molding. This was a real
problem at one point making ceramic packaged memory have a higher soft error
rate than plastic packaged memory sometime around the 64 kbit generation.

This is not a problem for analog ICs of course but do they use different molding
compounds for analog and digital? Even if they did, I suspect they would still
avoid anything volcanic just in case.

>For example, one IC I've purchased with this type of anti-moisture packaging is a voltage reference chip from TI. These chips can get spendy - aren't they really just voltage regulators ?

Most of the cost for ICs like precision voltage regulators is in the testing and
grading instead of the silicon and packaging. Testing time is dimes or dollars
per second and I would assume the best precision references would be tested over
some temperature range and maybe even burned in which will take time.

The difference between an operational amplifier tested for 10 Hz spot noise and
0.1 to 10 Hz noise is about 10 seconds. The TL07x series operational amplifiers
are low noise tested versions of the TL08x series. The National LMC6001 ultra
low input current operational amplifier is an LMC6081 that spent enough time on
the tester to verify a maximum 25 femtoamp input current which is a time
consuming measurement.
9985 2014-04-29 10:14:46 wb9kzy Re: State-of-the-Art Op Amps Require A Sense of Humor
David -

You are probably correct about Japanese volcanic sand - I said that because:

1) the handful of companies I recall that make molding compounds are Japanese
2) I assume that sand=silica => something with similar mechanicals to single crystal Silicon
3) when I used to look at chip dies under the microscope, the acid etched molding compound reminded me of volcanic sand  :)


73,

Chuck, WB9KZY
Jackson Harbor Press
9986 2014-04-29 10:39:39 Todd F. Carney / ... Re: State-of-the-Art Op Amps Require A Sense of Humor
Any special environment requirements would certainly show up in the official datasheet, wouldn't it? 

I mean, they put dimensioned drawings of standardized chip packages and of common component-reel dimensions to provide as much information--in this case, pretty superfluous--as they can. 

It would be an incredible oversight to not also include info on special environmental needs beyond the storage and operating temperatures they always provide. 

73,

Todd
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K7TFC / Medford, Oregon, USA / CN82ni / UTC-
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9987 2014-04-29 11:05:46 Dana Myers Re: State-of-the-Art Op Amps Require A Sense of Humor
9988 2014-04-29 11:27:54 Jim Strohm Re: State-of-the-Art Op Amps Require A Sense of Humor
For our purposes, we can pretty much ignore the strict environmental storage and bake-out requirements.  The first time I got samples bearing this documentation I called the field engineer on the devices and asked "so what does this spec MEAN for me?  I'm doing hand-soldered prototypes and may not get to these samples before the expiration date."

Her answer was, "store them per the datasheet* in a climate-controlled environment in the original package or similar moisture-resistant anti-static packaging, and handle as any normal static-sensitive semiconductor.  For your prototyping purposes, it's a 'don't care /don't matter' situation.  When you're ready to go to production, call us back."

IIRC they went in a closed plastic storage bin in my bathroom for five years, where the additional moisture from the daily shower served as a static-reducing environmental control.

73
Jim N6OTQ

*Almost always this is something like 5 - 95% relative humidity, non-condensing, -40 to 75C, 0 - 15,000 feet altitude for storage.  So as long as you don't get water IN your storage container, if you can be in the same room with the parts, they'll be fine. OTOH, never leave your roll of solder outdoors overnight.  I ruined a new roll of .020 60/40 like that once.


9989 2014-04-29 12:07:13 Todd F. Carney / ... Re: State-of-the-Art Op Amps Require A Sense of Humor
9990 2014-04-29 12:09:39 David Re: State-of-the-Art Op Amps Require A Sense of Humor
On Tue, 29 Apr 2014 11:05:21 -0700, you wrote:

>I can easily believe there's a generic application note regarding the care and handling
>of a family of parts instead of repeating the information in every datasheet.
>
>In fact, I googled "bake-out components" and found this:
>
>http://electrocomptr.com/Moisture-Bake-Out/
>
>which explains the popcorn effect in SMD assembly.
>
>I tend to believe there's nothing special about the component performance
>(the die is likely passivated) other than mechanical issues related to popcorn effect.

Not to be confused with the other electrically related popcorn effect (*) which
is hopefully confined to the past:

http://en.wikipedia.org/wiki/Burst_noise

I *have* seen this, the mechanical popcorn effect and not the electrical one
although I have seen that as well, happen to plastic power packages where rapid
heating after assembly during operation caused the plastic to spall and it did
sound like popcorn.

(*) While this is suppose to be humorous in keeping with the thread subject, it
is unlikely to be funny dealing with it in real life.
9991 2014-04-29 12:18:50 David Re: State-of-the-Art Op Amps Require A Sense of Humor
I was just trying to be weakly humorous. I doubt (and hope) that the Japanese
would not even risk repeating that mistake.

I do wonder though if different plastic package encapsulants are used for
digital, analog, and precision analog parts. I know that in the last case, the
leakage current through the plastic encapsulant has been really good for a while
now so ceramic packaged parts lost their advantage there. I suspect the
improvement could have been in just the quality control of the raw material.

On 29 Apr 2014 10:14:46 -0700, you wrote:

>David -
>
>You are probably correct about Japanese volcanic sand - I said that because:
>
>1) the handful of companies I recall that make molding compounds are Japanese
>2) I assume that sand=silica => something with similar mechanicals to single crystal Silicon
>3) when I used to look at chip dies under the microscope, the acid etched molding compound reminded me of volcanic sand :)
>
>
>73,
>
>Chuck, WB9KZY
>Jackson Harbor Press