Absolutely! I love destruction too. I use to be rather violent, diligently using diamond saw, pliers, drills, any tools to have a look on inside. However, ain't possible in this case. Each substrate costs 1,500 USD and we have a whole bunch of them for deciding: useful or rejection. And I have the baton. Want to change over, but noone wants it. You have a point, Wayne. The gold is extremely dense to be such thin a thickfilm. If the adhesion was indisputable, we'd went on and not been so fussy about the thickness. Now, there is another aspect too, which you are familiar with, namely the adhesion vs. thickness vs. firing conditions. I've studied internal reports from Tanaka, duPont, ESL, Heraeus and some more, and the curves demonstrate, clearly, the functions for the thickness. Varies a lot depending on what mixture and what manufacture. But there is a general tendency that the adhesion has a lower value at a minimum thickness, has an increase, a maximum, and lowers when you pass a maximum thickness. I was afraid, that we had to do with such a catastrophic minimum caused by too thin a paste. I know what you will say now, the spread isn't so dramatic, that you get a magnitude or more lower adhesion. You are maybe right. There is probably another parameter that has a stronger impact. Or it may be a combination of wrong firing and that parameter. It's a mixed binder, and the frit is the dominant one, according to our substrate maker. I'm sorry for bla-bla-bla a lot, but this matter is kind of emergency case, and I have just a few days to come with something intelligent. Now, if I compare with others, e.g. Trikeman's VSOP, there is a significant difference (if not the very parameter I search) and it's the MECHANICAL binding mechanism. Brand X, or Y or Z have zillions of microsized glass 'hooks' from the tape, glass protrusions that stretch into any void or opening in the thickfilm, thus working as very strong bonds. The thickfilm that we talk about as problematic has no such glass 'hooks' or at least very few. I've demonstrated this to the substrate maker, but they don't seem to know what I'm pointing at, or do they dislike my ambition to find a process anomaly. Thanks Wayne. Even if I didn't get a solution, at least you pushed me in the right direction. Good. Inge -----Ursprungligt meddelande----- Från: TechNet [mailto:[log in to unmask]] För Wayne Thayer Skickat: den 30 mars 2007 12:18 Till: [log in to unmask] Ämne: 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 parts without destruction of the gold. Abcd recommended confocal laser, don't think that will work. VHF transducer, 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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