[time-nuts] Parts Selection

Bob Camp lists at rtty.us
Fri Mar 25 18:08:53 UTC 2011


Hi

For the sake of the poll, let's say it wasn't something crazy valuable. Pick
a piece of gear that's already on your bench (or that could easily be) and
assume we're talking about that. The cost to buy ratio may or may not be in
favor of the kit. A lot would depend on how much of a shopper you are. 

Put another way, it's interesting enough to make you buy it, but not
interesting enough to go nuts over it. 

On that basis, I'll put you down as a no to the question set. 

Bob

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of paul swed
Sent: Friday, March 25, 2011 2:03 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Parts Selection

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 <lists at rtty.us> wrote:

> Hi
>
> I'm guessing that's a yes to each of the questions in the poll.
>
> Bob
>
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] 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
> >
> >
> >
> >
> >
> >
> >
> > _______________________________________________
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> >
>
>
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