Ohhhh, as Emporer, I have minions everywhere.....
Doug Pauls
From: "Stadem, Richard D." <[log in to unmask]>
To: TechNet E-Mail Forum <[log in to unmask]>,
"[log in to unmask]" <[log in to unmask]>
Date: 12/14/2012 09:07 AM
Subject: RE: [TN] Component issue - epoxy die attach
Now, how did you know about that, Doug?
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Pauls
Sent: Friday, December 14, 2012 8:12 AM
To: [log in to unmask]
Subject: Re: [TN] Component issue - epoxy die attach
Steve,
Hell, take the Title and have some fun with it.
At IPC, I decided that General Chairman, Cleaning and Coating Committees
was too boring a title. So I bestowed the Title of Emporer on myself.
Debbie Obitz became Vice Empress.
Graham Naisbitt is the head of the Jedi Council John Perry and Kris
Roberson are now Grand Moffs.
We have a few System Lords running around.
We definitely have more fun than the other General Committees.
So have fun. Maybe Inge can be the Marquis of Micro. Mr. Stadem can be
Duke of DRAMS........
Doug Pauls
From: Steven Creswick <[log in to unmask]>
To: <[log in to unmask]>
Date: 12/14/2012 04:53 AM
Subject: Re: [TN] Component issue - epoxy die attach
Sent by: TechNet <[log in to unmask]>
Inge,
Not so sure I desire / deserve that title.
I would submit it to you instead.
Howard, you have asked a few questions for which there likely are no
perfect answers except, "it all depends".
"Back in the day", I was familiar with some commercial 'hermetic' parts
that I would not recommend anyone use.
I agree with Inge that processes have improved [and most of the really bad
suppliers no longer exist], but I view RGA results as a planned goal
related to adhesive processing, overall component cleanliness, and
pre-seal processing conditions. The RGA results are only as good as your
process leading up to the sealing operation. Once the package is sealed,
it is a done deal. You cannot screen out for RGA on a piece by piece
basis, as you can with electrical test. Die attach, wire pull and
electrical test results should be almost transparent across the spectrum
from COM, MIL, to Space.
The only difference is that one normally imposses greater requirements,
and increased testing frequency on MIL/Space than on the COM product. And
for reference, with the exception of radiation hardness, Implantable
Medical devices were as tight, or tighter than Mil/Space
Now then, many manufacturers that make both Commercial and Mil product
will often share a great deal of processes, but sometimes Production, is
Production.. If a Mil pre-seal bake was 24-36 hrs, a corresponding Com
bake may have only been 8-12 hrs. Pre-seal bake and vacuum bake ovens
attached to the sealing chambers are limited in size, so one would not
generally allow a Com grade part to unnecessarily take up resources. Maybe
8-12 hrs is not quite good enough to meet Mil specs. that's why it is
processed as a Com part.
Sorry we are not giving you a clean answer to your questions.
Inge's wealth of documents will be helpful in your education, however.
Still time for me to bundle up and check out the meteor shower!!!
Best wishes,
Steve Creswick
From: Inge Hernefjord [mailto:[log in to unmask]]
Sent: Friday, December 14, 2012 3:08 AM
To: TechNet E-Mail Forum; Steven Creswick
Subject: Re: [TN] Component issue - epoxy die attach
Howard,
I'm afraid we do bombard you with facts so will be choked. Therefore, I'll
take it slowly.
1. Steve is King of Micro, listen to him
2. Nothing wrong with upgrading commercial to MIL or SPACE. JAN, QL,
etc
too expensive, will disappear. Semi processing been so good today, that
there is nearly no difference between commercial and MIL production.
3. I send offline to you an article, that is a good one to start with. No
meaning to complicate the question. Suitable drink for this paper: 4 cl
Isle of Jura 4. Epoxy hysteria was initially because its outgassing caused
trouble for all optics in SPACE parts. Agree with the King, well processed
epoxies do no harm.
Inge
On 14 December 2012 03:14, Steven Creswick <[log in to unmask]>
wrote:
Joyce - Agree, but so do the Ni & Au platings.
If the package had a hole so large that the helium was absorbed enmass in
the adhesive, it should have failed hermeticity due to the presence of He
-
or gross leak testing.
I hope that he can at least trust that the hermeticity test was done
properly. You are right though, if that is not done correctly, all is
lost.
Without being privy to the manufactures methods, it appears as though one
is attempting to make a silk purse from sow's ear.
It is my opinion that meeting RGA requirements is not a 'will test later'
kind of requirement - unless you plan to do 100% [destructive] testing.
Meeting RGA requirements is something that one needs to plan for, and
process accordingly, from the beginning.
Steve Creswick
Sr Associate - Balanced Enterprise Solutions
http://www.linkedin.com/in/stevencreswick
-----Original Message-----
From: Joyce Koo [mailto:[log in to unmask]]
Sent: Thursday, December 13, 2012 9:02 PM
To: [log in to unmask]; [log in to unmask]
Subject: Re: [TN] Component issue - epoxy die attach
Steven, epoxy absorb He. If he did He leak test, pass hermidicity means
nothing. My 2 cents.
--------------------------
Sent using BlackBerry
----- Original Message -----
From: Steven Creswick [mailto:[log in to unmask]]
Sent: Thursday, December 13, 2012 08:58 PM
To: [log in to unmask] <[log in to unmask]>
Subject: Re: [TN] Component issue - epoxy die attach
Howard,
Sorry, this will be a bit long.
I am glad you stated that the packages passed hermeticity testing. That
would have been the first item to check.
I assume this is TO-5 or smaller style package. The smaller volume
packages can be problematic if there is a leak during puncture of the
package because the available tested volume is so small compared to a
potential leak.
Different labs used to test for RGA in different manners, with different
style equipment.
On one style of test equipment, the sample package would be placed into
the evacuated test chamber and punctured/broken. The sample gas would
then flow into the chamber and subsequently be taken into the mass spec.
Other equipment relied upon placing the package up against the sampling
port, sealing it via an o-ring [of sorts]. Once fixed against the
evacuated sampling port, a needle would protrude through the center of the
o-ring and puncture the package lid, allowing the test gas to enter the
mass spec.
Both methods have pro and cons. The chamber method is most convenient for
all-ceramic style packages where there is no metal lid to puncture. A
problem with it is that the entire exterior of the package must be
thoroughly cleaned, but can still carry ad/absorbed species into the test
chamber. Plated surfaces also can contain a great deal of trapped
hydrogen put down during plating. Some systems would see Hydrogen, and
log it as H2O.
With the puncture method, if the lid is too robust, the act of puncturing
could displace the sample from the seal and allow atmosphere to be
introduced, thereby squirreling up the data. Most hybrids had
0.010-0.020"
thick lids and what WE often did was to take a small end mill [~0.050"
dia]
and mill a small recess in the lid, leaving only about 0.005" of metal
thickness. The lab would than center this in the seal. Generally, this
gave us more consistent data.
Variance of data - either approach is prone to variation if everything is
not absolutely perfectly cleaned and performed. You did not say how many
samples you ran at each lab. Hopefully, you ran 4-6 at each. As a
minimum, 3, so you could throw out the low and high, and keep the middle.
I am sorry, but to test 1 or 2 is almost fruitless due to variance.
To the adhesive - Two major potential issues come to mind.
First - if you take a great adhesive and improperly process it, you end up
with garbage. The 84-1LMI is a very good adhesive which has been used by
many firms in Space, Mil, and Implantable medical applications. It can
meet the requirements of Mil Std 883, TM 5011 when properly processed.
That is a very good material to use - if properly processed!! Depending
upon the date of assembly, it was THE material to use. [I am not in any
way associated with Ablestik/Henkel, but I have indeed used this material
on many hybrids, including many space applications, one of which is still
in the Saturnian system]
Second - No matter how well you process the adhesive, if the pre-seal
conditioning [pre-seal bakes, vac bakes, package [and lid] cleanliness
[and bakes] is not adequate, one will end up trapping trash inside a
hermetic package.
Yes the limit is 5000PPM. The real issue is [if the RGA testing is
accurate] what other ionics and corruption do you have inside the package
to combine with the water??
Whether adhesive is allowed or dis-allowed is generally addressed by the
detail specification for the device. I do indeed know of quite a few
Space level parts that have adhesive inside.... properly processed
adhesives...
No one can really give you a definitive answer, at arms length, such as
this, but here are my free two bits ...
I would have to go back and review my dew point knowledge, but I strongly
suspect the 28000 PPM is bogus [unless device assembly is really sloppy -
see below]. You should be able to achieve well under 2000 PPM without too
much grief if it is a TO-5 or smaller package [properly processed].
My fear is that you are buying a commercial grade device, that was
assembled and processed as a commercial grade device, having no RGA
requirements.
Therefore, the adhesives were likely not processed in a manner which would
give you good RGA results. To make a poor analogy, it is like you are
buying a standard 75W incandescent bulb and banging it around as though it
were a Rough Service bulb. Yes, some will survive the abuse, but most
will have the filament destroyed almost immediately because they were not
constructed in a manner which would offer a much greater likelihood that
they would pass testing. That may be the situation you are in. Sorry.
Hopefully Inge is eyes-open and he can add a few comments as well.
Steve Creswick
Sr Associate - Balanced Enterprise Solutions
http://www.linkedin.com/in/stevencreswick
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Watson, Howard A
Sent: Thursday, December 13, 2012 6:24 PM
To: [log in to unmask]
Subject: [TN] Component issue - epoxy die attach
Hello 'netters,
I debated posting this, as it seems to me to be an obscure problem, but
then, I'm always amazed at your knowledge base. I have a JFET 2N6550
component to be used for space application. Unfortunately, it is not
manufactured at JANS space quality, so we buy the commercial grade, plus
an option 2 screening, which upscreens the part to "like" JANTXV. I think
this is called re-branding. Then, we send it to a lab for further
upscreening to JANS. The problem is that the parts are failing the
moisture test of the residual gas analysis (RGA). I found out that epoxy
is used for the die attach, and likely the epoxy is outgasing during
subsequent baking as part of the testing. My first question is who knows
of a standard for die attach of this component type stating that epoxy is
forbidden for military and space use? The epoxy used by the manufacturer
is Ablestik p/n 84-1LMI; Material # 1119570. I just found out today that
they do have the capability of eutectic die attach, and I'm pursing this
option, expecting a huge expense and lead time.
Secondly, I had two independent labs perform the RGA. The first lab had
results averaging ~28,000 PPM. The second lab results averaged ~5600 PPM.
The standard is no more than 5000 PPM. They both performed the testing to
the same MIL-STD-750. I can't understand the wide range of results, but
my second question is who knows of any studies related to the negative
effects of excessive (>5000 PPM) moisture inside hermetically sealed
devices used in space? By the way, they all passed the seal tests.
Perhaps some of you are knowledgeable in this area. Thanks in advance for
your help.
Howard Watson
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