Hey-hoee, ' ridiculous things we've done '...then we are not alone. Yeah, microwave LTCC is really magic, as you said. So magic, that you don't get nearly any spent money back....we call it daVinci-engineering, so advanced that it's not produceable. Before polishing and Fodel'ing we must remove the sealframe (Kovar). Your advice seemed mad at a first glance, but perhaps ain't not so crazy after all. The substrate are so advanced, that the supplier can only make a dozen or so a week. If we reject and force them to make replicas, they will panic. Doing your way would save a lot of money and time. If it works, then we can 'cofire' on both sides...with champagne. My slow brain would never found out such a solution..he-he. If someone asks from where I got this, I'll ask 'never heard of the Thayer method? ' Inge -----Ursprungligt meddelande----- Från: TechNet [mailto:[log in to unmask]] För Wayne Thayer Skickat: den 3 april 2007 15:16 Till: [log in to unmask] Ämne: Re: [TN] SV: [TN] SV: [TN] Cofired gold Hey Inge- Our guy in charge of LTCC production has been watching this exchange and reminded me of some of the ridiculous things we've done in the past. We've worked with very high density, difficult to manufacture LTCC layups. The high density was via density and line/space resolution, not layer count. But we would occasionally have issues with outer metal when we'd already invested a boatload of money in the substrates. So we "simply" polished off the conductors and printed new material on top. We used gold and used etching to define the conductors--very pretty job! While polishing, you could figure out how thick the metal is too! Not the ultra-cheap solution, but possible given the value you have locked up in the substrates. Wayne >>> [log in to unmask] 4/2/2007 6:40:52 am >>> Wayne - Ingemar, It seems that our experiences are similar. From my perspective, by the time the adhesion is low enough to fail the tape test, it is pretty pathetic [ie - scrap bin]! Depending upon the bonding mechanism, there IS a minimum/maximum required print/dry thickness. If it isn't there, properties [how ever you spec them] will not develop. Depending on what conductor it is, there is also a desired firing profile - along with that goes atmosphere. Yes oxygen! But also be greatly aware of the negative aspects of some hydrocarbons in the furnace atmosphere. Every engineer, regardless of nationality likes hard, clear data to base decisions on. That is what we are - whether we have PhDs or not. However, if the product is advertised as being wire bondable, and you have metallization lifts during wire pull, one of reasonable attitude would surmise that, "Hey! There might be a problem with our conductor. Let's get our heads together and work this out." And if you can't get past the Sales guys, there is always the long and arduous task of finding another supplier - and don't forget to mention that to them with respect to all future projects. Maybe you should bond up a panel and send it back for THEM to do wire pull and analyze the "failure", because it appears [rightfully so] unlikely that you will be willing to send these panels up in an aircraft or satellite. There is more to building a good part than just 'meeting the spec' afterall. Steve -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Wayne Thayer Sent: Sunday, April 01, 2007 9:38 PM To: [log in to unmask] Subject: Re: [TN] SV: [TN] SV: [TN] Cofired gold Hi Inge- Unfortunately, I don't have much more to offer with respect to the chemistry creating the adhesive bond. I only have commiseration in having had to deal with this situation previously when we have made our own substrates. Standard adhesion testing techniques also seem inadequate for the wirebonding process. Seems everyone uses the 3M Scotch #600 cellophane tape as the standard--if that doesn't rip off the coating, then it is declared good! Do your incoming parts fail even that test? If so, then what does the substrate manufacturer have to say about the situation? >>> [log in to unmask] >>> Nothing wrong being a yank, or southerner or even anyone from Iowa. The US is a remarkable phenomenon to me. People from 200 nations living together without knocking the head off each ones. Using a cliché, Americans are openminded, frank, bold, cooperative, helpful, have go and are optimistic and positive people. Of course, there are negative sides, but in fact I have never met other than handsome and lively Americans. Your former vice president Al Gore is here just now to participate in some TV programs. He seems to be such one good (clichee again) representative for the US. Enough of that. Wayne, the substrates are never touched, we find the bad adhesion just from the arrival to our plant. You seem to be very familiar with morphology, can you develop little more about oxide binding, frit binding and mechanical binding for duPont's LTCC top cofire golds? When speaking poor adhesion to the bluetape, do you have some kind of ranking what parameters are most likely to have such a negative impact on the adhesion? Despite it's Magics, as you say, there must be some mentionable facts that can be used in the discussion with the substrate maker. Offline, if you prefer. Thanks in advance Inge -----Ursprungligt meddelande----- Från: TechNet [mailto:[log in to unmask]] För Wayne Thayer Skickat: den 30 mars 2007 22:11 Till: [log in to unmask] Ämne: Re: [TN] SV: [TN] Cofired gold OK, so I'm a yank.... But, either Inge doesn't know how to calculate/measure adhesion, the "proper" adhesion is not the value Inge was led to expect from the material manufacturer, the substrate vendor did not handle the material property, or Inge has not treated the material properly once it got into the sphere of his influence. I discount the first 'cause I think Inge is a pretty careful guy, and consider the last option also unlikely since properly manufactured LTCC is pretty tough stuff. My favorite with LTCC is that DuPont used to list the flexural strength in the completely dry state. Once any moisture gets into it due to ambient humidity, the flexural strength drops by as much as 30%! So if you use their material in outer space where there is no moisture, their rated flexural strength is quite applicable. Otherwise, beware! Also, this week I got nailed by another substrate manufacturer. This time HTCC package which Hittite uses. It is QFN, and the package has as much plating on the QFN pads as on the wirebond sites. WAY TOO MUCH!! Hittite response to this is that it isn't their problem, since gold embrittlement is the assembly house's concern, not their's. I agree that "lying" is an offensive and extreme term, and I hereby retract the suggestion. But perhaps they left out some important information, such as maybe the adhesion when measured on Venus might be great. Wayne Thayer >>> [log in to unmask] 3/30/2007 3:48:23 pm >>> Dear Doctor K. I have to do with a very respectable German company, and these guys (all doctors like you) only respond to facts given in a professional tone. If I gave the littleast signal of not trusting them... we would be out.. With english ditto, I could just call 'John Smith' and say 'John, what kind of stuff are you sending to us this time! Has your grandmother baked the thickfilm this time?'..and I would get something crazy back... and the negotiations would start immediately. Americans? I don't dare say anythanding in one aspect...you get a reaction instantly...but they can be very stubborn and hard to convince they are wrong. Like their pr...erh Have a Nice Weekend all! Inge -----Ursprungligt meddelande----- Från: TechNet [mailto:[log in to unmask]] För Joyce Koo Skickat: den 30 mars 2007 15:48 Till: [log in to unmask] Ämne: Re: [TN] Cofired gold Wayne, adhesion is depend upon the maturaty of the product and process control. The surface roughness, cleanliness and material compatibility all play a role. For example, "black" substrates might have less adhesion due to its intrinsic material composition. I would not to call anyone "lying" until I know more of details (Inge possibly can call them what ever he wants after spend few thousands of his analytical work...hehehe...He is a very rich man)... Best regards, jk my 1.72 cents abcd -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Wayne Thayer Sent: Friday, March 30, 2007 5:18 AM To: [log in to unmask] Subject: Re: [TN] Cofired gold Hi Inge! I always prefer destruction. Something about the finality of the job. Anyway, I think you are probably going in the wrong direction. If the deposits are not porous, then the coverage is probably OK, and as Steve points out, the print process doesn't have a big window for thickness you can deposit, anyway--certainly not the factor of 3 you are suggesting you may be thin by. If you are ball bonding to LTCC, generally the ball goes on the part you've mounted to it and the stitch goes on the LTCC. Are you just doing some kind of qualification test? LTCC is magical stuff! It's a miracle that the stuff holds together during processing at all, especially during the densification phase of the firing process. I'd be looking for a chemistry cause for your trouble, not print thickness. If the firing environment got just a tad low in oxygen, other phases of the process may have stolen the oxygen molecules necessary for the bond between the metal and the dielectric. That's exactly what happened to me several years ago with a big LTCC job: I fired on low temperature copper on one side, and on the other side the previously fired and well-adhered gold actually fell off! So it may be that the LTCC manufacturer was lying about the adhesion you should have, or it may be that the substrate manufacturer messed up the firing environment slightly. Wayne >>> [log in to unmask] >>> Ingemar, Hmmm. 2 microns huh! Do you think this is a 'direct write' process? Sounds awful thin for a stencil don't you think? I was using a Sonix acoustic microscope. With a 200+ MHz transducer [think it was 280 MHz] I could reasonably well pick out the outline of major circuitry features on the underside of a flip chip, if I had it gated properly. Seeing internal traces within an LTCC body was always dependent upon how many internal ground planes and RF shields were placed inside the body as well. Vias above the target region were always bad news. You are on the surface. You may have a chance, but am not so sure you will be able to differentiate the top and bottom surface of the conductor when it is that thin. Definitely go for the reflected, high-frequency image. Give the challenge to a really good acoustic microscope guy with a good machine and decent software :-) Steve -----Original Message----- From: Hfjord [mailto:[log in to unmask]] Sent: Thursday, March 29, 2007 12:34 PM To: 'TechNet E-Mail Forum'; Creswick, Steven Subject: SV: [TN] Cofired gold 24 layer stack with cofired AuAg top. Lifts at ball bond pull tests, insufficient adhesion, I would say. Should take 4,000 psi. Smashed ball approx. 2 mil diameter. If the gold lifts at 10 grams, then you are > one magnitude below 4,000 psi. SEM'd edges of lifted lines= 2 micrometers thick. Paste maker recommends >7 micrometers as fired. Substrate maker denies, that's why I'm asking for method to check all incoming partsducer, not bad idea! Good. Will test that next week. Thanks. Inge -----Ursprungligt meddelande----- Från: TechNet [mailto:[log in to unmask]] För Creswick, Steven Skickat: den 29 mars 2007 16:14 Till: [log in to unmask] Ämne: Re: [TN] Cofired gold Ingemar, Are you speaking of a standard, single print of gold which has been co-fired into the body of the part, or possibly of a stack of inks which has been co-fired in at one time? XRF comes to mind, but it will require special 'standards', and the prep of the standards would result in the destruction of a sample of parts to construct them ... and even then I am not sure how successful you will be. It sounds as though a simple profilometer won't get you what you desire - especially since the bulk of the conductor is below the surface. I occasionally did internal inspection of LTCC parts back in the olden days - but that was looking more for omissions and commissions. I believe that acoustically, with a very high frequencurface of the conductor. The margin of error [due to surface imperfections] may be quite large, however. Can you get them to tell you what their stencil thickness was and based on solids content have some idea what you may have ended up with? Will ponder further Steve -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Hernefjord Ingemar Sent: Thursday, March 29, 2007 9:39 AM To: [log in to unmask] Subject: [TN] Cofired gold Trikeman or other gnu, Anyone know of a non destructive method to check cofired topgold thickness (Au over LTCC)? Inge THE INFORMATION CONTAINED IN THIS E-MAIL MESSAGE AND ANY ATTACHMENTS SENT FROM GENTEX CORPORATION IS GENTEX CONFIDENTIAL INFORMATION INTENDED ONLY FOR THE PERSONAL USE OF THE INDIVIDUAL OR ENTITY NAMED ABOVE. If you are not the intended recipient, you are hereby notified that any review, distribution, or copying of this communication is strictly prohibited. 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