[time-nuts] Subject: Re: Working with SMT parts (Bob Albert)

Bob Albert bob91343 at yahoo.com
Thu Aug 18 22:40:16 EDT 2016

I have a Chinese hot air gun with several nozzles.  Mine are the quarter-turn type but that doesn't work too well due to sloppy tolerances.  I have had nozzles fall off in the midst of use.  With some care they can be made to stay on, and if necessary bend them a bit to make them more secure.
I have used my hot air device a lot but only for disassembly.  For assembly, as I mentioned earlier, I would want to use solder paste.  I can't control the hot air well enough to heat just a bit of solder from a spool, and clipping off a piece while trying to put it where it belongs is a poor system.  So the paste seems to be the way to go.
Someone needs to invent a low cost paste that doesn't spoil in a few months.  It does seem that the Mechanics paste might be an answer to this; I would keep it refrigerated although that might be locking the barn door after the theft.
Again, I am not trying to meet some government soldering specification; I just want something to work without a lot of fuss and cost.
What do major companies do when they discover their stuff is outdated?  I need a connection to some of those people, maybe pick up some of it now and then at low cost.


    On Thursday, August 18, 2016 7:26 PM, Bob Stewart <bob at evoria.net> wrote:

 The stuff I use is Chipquik SMD291AX.  The first syringe of it I bought was from Mouser and was 15 grams.  That was back in 2014.  The second syringe I got was SMD291AX10, which is 35 grams.  It's dated 3/15/16, so you can see how long solder paste will last if you take reasonable car of it.  I pumped about 15 grams of that into the original syringe and put them both in the fridge.  I've had the small one out on the workbench for several weeks now, and there doesn't seem to be a problem.  I fold a piece of tape around the needle when it's not in use to keep the air out.  When I pull the tape off, I pump out about a 1/4" string and throw that away.  The rest works just fine.
If you haven't switched to using a hot air gun, I strongly suggest it.  They take a bit of getting used to, but after that, they're a time-saver.  I have the cheap ebay solder station labeled 852D+.  It has solder pencil and hot air.  There are two things I don't like about it.  One is that you can't turn the air flow down enough to use narrow nozzles for anything other than blowing soldered components off the board.  But it's Much better than trying to use a pencil for that chore!  The other is that the tips are attached by tightening a screw.  There are units out there that have a little tool that you use to give the tip a 1/4 turn twist to attach.  I don't change tips much, but not having to wait for the hot air gun to cool down would be nice.  The first time you reach for the hot air gun to shrink tubing or to solder the center pin for an SMA connector, you know you've "arrived".



      From: Bob Albert via time-nuts <time-nuts at febo.com>
 To: Discussion of precise time and frequency measurement <time-nuts at febo.com> 
 Sent: Thursday, August 18, 2016 8:49 PM
 Subject: Re: [time-nuts] Subject: Re: Working with SMT parts (Bob Albert)
I don't care about lead-free since I am not manufacturing, just repairing or building or experimenting.  But there seems to be more than one way to view this stuff.  Yes, it might be expired, but some say that's not a major issue.  I can't justify the prices asked by US distributors, especially in light of the fact that I use very little.  So the fresh stuff, carefully refrigerated, would be expired by the time I use the second or third scoop of it, anyway.
What's a casual experimenter to do?

    On Thursday, August 18, 2016 3:33 PM, Chuck Harris <cfharris at erols.com> wrote:

 The Chinese are certainly using a lot of solder paste, so they
are a source.  I tend to buy mine from Mouser, Digikey, TekSource,
places like that.

The last stuff I bought was made by Kester, and came from TekSource.

The only problem with using the real sources is in the summer, they
will pack your paste in an ice pack, and send it over night unless
you insist otherwise (and absolve them of any warranty).  That kind
of shipping is very expensive.

And, there is absolutely no possible way the paste you get from
China is going to make it here and follow the manufacturer's
guidelines for safe handling.  So, even if you buy new and pay
a premium price from China, you are getting paste that is expired
by the poor handling (not refrigerated).

I would bet that any paste you get on ebay is expired, for a variety
of reasons.

Also, I only buy tin/lead, though it is getting very hard to find.
It works so much better than lead free.

-Chuck Harris

Bob Albert via time-nuts wrote:
> Well I have found some Chinese sources of 42 - 50 grams on ebay for around $3.  Is
> this the right stuff?  The brand is Mechanics.
> Bob
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