My first answer would be heck no. Enough trouble with 16 pin chips. BUT now you have set the bait. A cesium standard. That would grab my attention. So indeed if there were not a time limit, I would invest in a very small tip iron and the correct solder. I have come to the conclusion also that the tips Greg suggests can work. I simply have equipment thats to large. (Funny I stayed clear of that hair size solder at the Flea markets) This will be resolved I hope at the first MIT flea or heaven forbid really ordering new. Second those days of soldering might be non-coffee days. :-) I have done some crazy stuff if the price to value ratio is correct. Regards Paul
On Fri, Mar 25, 2011 at 1:56 PM, Bob Camp <[email protected]> wrote: > Hi > > I'm guessing that's a yes to each of the questions in the poll. > > Bob > > -----Original Message----- > From: [email protected] [mailto:[email protected]] On > Behalf Of Greg Broburg > Sent: Friday, March 25, 2011 2:53 PM > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] Parts Selection > > I have assembled hundreds of such parts using only a > low cost Antex 15W soldering iron, some fine diameter > solder and some solder wick. A hot air gun makes > removal very easy and I have never damaged a PCB > using the hot air removal method. > > Solder diameter should be .010 - .015 mils Large > diameter solder is a problem with this method. > > To put a .5mm pitch part down without any fancy stuff > > 1: Carefully align the part with the pads, double check > that Pin 1 is in the correct alignment. Now solder a > couple of pads at two opposite corners to stabilize the > part. Expect to solder two to four pads at the corners > and that they will be shorted. Do not worry if you have > shorts between closely spaced pads. We will fix that later. > > 2: If the pad alignments are not perfect then reheat one > of the two opposite corner pad (s) and move the part > until it is correctly aligned. > > 3: When all pads are aligned then carefully solder all of > the leads to all of the pads. Do not worry if some pads > are shorted. do not worry if all pads are shorted. > > 4: Using .025 mil solder wick dipped in RMA solder flux > if not already fluxed, desolder all of the pads. In other > words, the solder wick is not effective at removing all of > the solder. What is left from surface tension will be the > correct amount. > > 5: Using a QTip with alcohol / acetone / dope thinner > clean all pads of flux. Do this twice or more each time > with a fresh QTip tip. > > 6: Inspect using magnification if necessary, to verify no > shorts or solder balls between pads. If so, use the solder > wick to remove the short. > > I have done this hundreds of times. > > Greg > > > > > With regards to soldering .5mm pitch parts: > > > > I've never done that professionally or as a hobby. > > > > I don't see myself doing this at home. > > > On 3/25/2011 11:07 AM, Bob Camp wrote: > > Hi > > > > > > > > Just a show of hands sort of thing. It comes up each time we talk about > > projects and never really gets answered. Rather than trying to work it > out > > as a part of a project, let's see if it can be addressed by it's self. > > > > > > > > How many people are willing to solder up a project with multiple 0.5mm > > spacing>=144 pin package IC's on it? There's a typical package drawing at > > the end of: > > > > > > > > http://www.national.com/ds/DP/DP83816EX.pdf > > > > > > > > I'm sure it's a "what's in it for me?" sort of question. Let's assume > it's > > just neat piece of bench gear rather than a home grown cesium standard > for > > $100. > > > > > > > > I don't think this part really matters, but it might to some people. Say > > each chip is well below $100, but above $20 each. There might be only one > > part like this on some projects, but for the sake of this poll, let's say > > there are two or three of them. Net is roughly 250 to 500 pins like this > to > > solder, on some number of packages. It's part of a project that will cost > > you $250 to $500. > > > > > > > > I'm not talking about opinions on weather it can or can't be done. It > > certainly can be done and is done every day. What I'm asking is - would > you > > buy a bag with the parts all in it? If you do are you going to put it > > together in a reasonable amount of time? Reasonable time might mean > > different things to different people. For the sake of completeness, yes > you > > also need to get it working after you assemble it. > > > > > > > > Next layer (you knew there had to be more) - have you done it before > > (anywhere)? / done it in the last 2 years (at home)? / are you set up to > do > > it today (at home)? > > > > > > > > I'm not trying to get into "how would you do it / what would you need / > > could you farm it out". Those are also neat questions, but not part of > this. > > > > > > > > > > I'll start off the voting (and yes the answers are out of order): > > > > > > > > Done it in the before - yes. > > > > > > > > Done it in the basement / last 2 years - no. > > > > > > > > Set up to do it in the basement - yes, but not set up well. > > > > > > > > Would I buy one - done that before. Likely would again. (counts as a > yes). > > > > > > > > Would actually do it in a reasonable amount of time - unlikely. (That > > counts as a no). > > > > > > > > Any more votes? > > > > > > > > > > > > Bob > > > > > > > > > > > > > > > > _______________________________________________ > > time-nuts mailing list -- [email protected] > > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
