Yes, Steve, you are the unquestionable King of Microelectronics in TN. Am
sure all agree.  Basta!

I've sent a rather good article to Howard with the title 'Issues in
Hermetic Sealing of Medical Products' . The author briefs some common
matters, no academic, endless argumentation. I will even prepare for
shareing  some deeper papers for downloading, if someone wish to learn
more. Maybe I could let Steve Gregory 'administrate' .?

Inge




On 14 December 2012 11:51, Steven Creswick <[log in to unmask]>wrote:

> Inge,
>
>
>
> Not so sure I desire / deserve that title.
> mew
>
>
>               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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