Hi again, this seems to be a never ending story. Well, I add some from our production of GaAs and InGaAs MEMS like upcons. We found that the Indium oxidized very fast for a number of alloys, so, after a lot of experimenting, we found the best solution. We used a SSEC vacuum soldering machine, put the hundreds of objects in the vacuum chamber, with 25 micrometers thick InSn preforms and a small weight on them all. Then we sprayed a "cloud" of ant's acid (forgot the chemical name) and put the cover on, vacuum pumped and soldered at +115C for 15 minutes. Don't ask me why this and that, because I don't have all details in mind. If I remember right, noble Mr In helped us.. There is a somewhat useful article about the process in Dropbox under Soldering " Development of..Indium Soldering..." Inge On 31 March 2013 16:05, Mike Fenner <[log in to unmask]> wrote: > Hmm > Not sure there is much benefit from inerting at low temperature in presence > of flux. > Viability of performs against paste would depend on the volumes involved > and > geography of assembly. > I see Guy talked about T5 paste. If T5 really is needed that implies a tiny > dot size and implies a small perform also which might give supplier issues > and handling issues in use. > Personally I would recheck the T5 requirement on the one hand and > availability on the other. [This to make sure it isn't a "price book" > quote]. > Possibly other solder processes might be possible. > So far as non solder attached is concerned: > H20E is OK, but like Steve I prefer 84-1 series more, I step back to take > notes on wire bonding etc. > > Best Wishes > > > > Mike > -----Original Message----- > From: TechNet [mailto:[log in to unmask]] On Behalf Of Steven Creswick > Sent: Sunday, March 31, 2013 11:43 AM > To: [log in to unmask] > Subject: Re: [TN] solder which does ot scavenge gold > > Guy, > > A couple of additional thoughts for you. > > Instead of paste, consider the use of performs. Like Mike says, flux will > be a challenge. Definitely use inerting and possibly a localized reflow > apparatus that provides a very good localized reflow atmosphere. The low > temp of the proposed IN alloy, and the high temp of the Au/Sn will > definitely introduce speedbumps in a nice process flow. > > If your substrate were LTCC or 96-99% alumina the CTE of the GaAs would be > almost a perfect match [3-7, 6-7, and 6-7 PPM/°C respectively]. The > slickest thing to do with LTCC is create a pocket to drop the diode in > [face > up] and use no-loop ribbon bonds to bond from diode to substrate using 0.5 > x > 2 or 4 mil Au ribbon. Bonding would readily be performed below your max > allowable temp limits. > > Since most adhesives do not bond well to gold or solder, the potential for > CTE mis-match in your system [and subsequent bad connections] would seem to > require a thorough examination. > > If you could use ENEPIG for a surface finish, you could non-conductively > bond the diode, face up, and wire, or ribbon, bond the diode to the > circuit. > Can you get away with it from a frequency response/circuit function point > of > view? This still presents issues from a process flow point of view, but > seems to be the cleanest approach to a hybrid guy. That or bumping... > > A blessed Easter to all. > > Steve C > > > -----Original Message----- > From: Steven Creswick [mailto:[log in to unmask]] > Sent: Friday, March 29, 2013 10:57 AM > To: 'TechNet E-Mail Forum'; 'Guy Ramsey' > Subject: RE: [TN] solder which does ot scavenge gold > > Guy, > > Others likely have already touched on this but the Indalloy #2 has a 154°C > liquidus which meets your temp limitations. 80/20 Au/Sn is a 280°C > eutectic > which will not meet your temp limitations. > > I suspect that 80/20 will be just as expensive as the #2. > > Don't know what you substrate/board is, but it will likely not take kindly > to the temps required of 80/20 either. > > I view a conductive adhesive as being THE last thing I would do. Instead > or > H20E, I would definitely steer you to Ablebond 84-1 [anything in the > 84-1LMI, LMINB1, etc series]. Much better thermal characteristics! But > getting any adhesive to adhere to gold is problematic! ANY amount of > substrate/board flex, and the die will pop right off. > > Generic silver glasses have too high a cure temp as well. > > You could thermosonically flip chip bond this low I/O device to the board > if > you could bump either the diode or the board. Simply requires one or two > gold ball bonds [to form the bumps] on each diode [or substrate/board pad]. > The Au/Au bond will form nicely at 150°C + ultrasonics and about 35-50 gms > of force per 'bump'. Alas, you require a bondable board and a $250K > bonder... Au/Au thermocompression could work to, but temps will be way > too > high. Additionally, the face of the diode will standoff the > substrate/board > by 25-50 µm, depending on wire size used, and actual bumping process. > > I don't like working with high Indiums either, but don't see an immediate > alternative. > > > Steve Creswick > Sr Associate - Balanced Enterprise Solutions > http://www.linkedin.com/in/stevencreswick > 616 834 1883 > > > > -----Original Message----- > From: TechNet [mailto:[log in to unmask]] On Behalf Of Guy Ramsey > Sent: Friday, March 29, 2013 9:28 AM > To: [log in to unmask] > Subject: [TN] solder which does ot scavenge gold > > Background info: > We were asked to populate and assembly with a Ma-Com part, MA46H120, a GaAs > Constant Gamma Flip-Chip Varactor Diode. The data sheet says: > > Mounting Techniques - These chips were designed to be inserted onto hard or > soft substrates with the junction side down. They can be mounted with > conductive epoxy or with a low temperature solder preform. The die can also > be assembled with the junction side up, and wire or ribbon bonds made to > the > pads. > > Solder Die Attachment - Solder which does not scavenge gold, such as > Indalloy #2 (80In-15Pb-5Ag) is recommended. Sn-Pb based solders are not > recommended due to solder Embrittlement. Do not expose die to a > temperature > greater than 235C, or greater than 200C for longer than 10 seconds. > > The Indalloy #2 cost $2,222.00 for 100gm or type five solder paste. > > We now have another customer asking for us to solder to thick gold. They > don't have a low temp requirement and asked for SnAu solder (Indalloy #182) > 80Au-20Sn. . . I shudder to think what that will cost, and I don't think > the > part, an inductor, will survive the 300C reflow. > > Question: > Does SAC 305 "scavenge gold"? Would it form a brittle solder connection on > a > thick soft gold pad? > > Guy > > > > > > > ______________________________________________________________________ > This email has been scanned by the Symantec Email Security.cloud service. > For more information please contact helpdesk at x2960 or [log in to unmask] > ______________________________________________________________________ > > > ______________________________________________________________________ > This email has been scanned by the Symantec Email Security.cloud service. > For more information please contact helpdesk at x2960 or [log in to unmask] > ______________________________________________________________________ > > > ______________________________________________________________________ > This email has been scanned by the Symantec Email Security.cloud service. > For more information please contact helpdesk at x2960 or [log in to unmask] > ______________________________________________________________________ > ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. 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