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..." On 31 March 2013 19:34, Inge Hernefjord <[log in to unmask]> wrote: > 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. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________