Thanks Steve, formic acid it was. No, we could not handle them, but for our MRSI cell II it was no problem. Its placement accuracy is +/- 5 microns!The machine stands on pressurised air cushions, and a 1 ton granite block absorbs vibrations that the cushions couldn't stop. In opposition to a Panasonic chip shooter MRSI is slow, but fast enough. On 31 March 2013 19:43, Steven Creswick <[log in to unmask]> wrote: > Formic acid? > > .... and Mike thinks we couldn't handle 100 x 200 µm performs chuckle > chuckle. :-) > > Ours was the medium vac model, down to about 70-80 mT... > http://www.sstinternational.com/prod_vacpres.html > > Steve C > > -----Original Message----- > From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge Hernefjord > Sent: Sunday, March 31, 2013 1:35 PM > To: [log in to unmask] > Subject: Re: [TN] solder which does ot scavenge gold > > 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] > ______________________________________________________________________ > > ______________________________________________________________________ > 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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