Hmmm, Eric, it's not quite like it ; I'd doubt good ol' KW would mean the
sensible span of alloy applicability doubling at the same time as tolerance
window of your process .
To hit 270 straps can be interesting exercise if you did not design for it .
After all, pot check is not for the sake of the pot , but the boards ; and
they come like us (allsorts) .
Some like it cool, some hot. +/- , naturlich .
paul klasek
ResMed
-----Original Message-----
From: Eric Kalgren [mailto:[log in to unmask]]
Sent: Thursday, 7 October 1999 7:32
To: [log in to unmask]
Subject: Re: [TN] Wave solder pot temperatures...
Steve,
We used to have a Hollis Future 1 and we kept the solder temp at 500 degF
and ran just like that.
My Klein-Wassink book says that for "most machine processes the temperature
of the solder bath must be chosen between 240 and 270 degC and the dwell
time between 2 and 4 seconds."
Would this be a good enough justification to discontinue checking the solder
temp as the book gives a 30 deg C tolerence? After all, when I asked the
TechNet, the response was overwhelming that K-W was a good source.
Eric Kalgren
BFGoodrich Aerospace
Data Systems Division
(505) 938-5139
>>> Hinners Hans Civ WRALC/LYPME <[log in to unmask]> 10/06/99
01:38PM >>>
Hey Steve,
Ideally, the temperature should be measured in the same location as the
Hollis' thermocouple. That's how you verify the machines' temperature
reading. Doesn't sound like she understands thermodynamics. I've got
Kittel (Stat. Thermo) and a really great book by Fermi (Notes on Thermo) if
you'd like to borrow it. :-) Who ever came up with that procedure needs a
refresher.
1). Ask for a copy of their written calibration procedure and get the
bloody thing changed! Then it will be the way they do things.
2). Is the handheld unit calibrated?
3). Is there training & certification for this inspection?
4). How long was the probe in the solder? Did the probe reach equilibrium?
(That's what killed the Challenger Shuttle, in part.)
I feel for ya bud. Remember, if engineering were easy everybody would do
it. ;-)
Hans
PS. This crisis calls for Starbucks! (Okay, I'm Jonesing for a Venti
Hazelnut Mocha.)
~~~~~~~~
Hans M. Hinners WR-ALC/LYPME Bldg. 640
Materials Engineer 380 Second Street,
Suite 104
Manufacturing Eng. Sec. Robins AFB GA 31098-1638
912-926-1970 (Voice) 468 - 1970 (DSN) 912-926-7974 (Fax)
mailto:[log in to unmask]
> It's been a frustrating day...
>
> I was at our old wave solder machine this morning (a Hollis SMT Future-1,
> about 12-years old) and one of our QA inspectors came in to check the
> calibration on it. The procedure here is to verify that the speed of the
> belt
> is what's indicated on the readout of the machine, and to check that the
> solder temperature in the pot is within +/- 5 degrees F (which seems
> unnecessarily tight to me). from what is indicated. I run my pots a
> 485-degrees F. We were in the middle of a run, so she said that she'll do
> the
> belt speed check after we were through, but would go ahead and check the
> solder temperature. We had the laminar pump running and she put the
> thermocouple in the wave. The readout on the machine was 484 F., and she
> indicated 490 F. on the hand held unit she was measuring with. She said;
> "The
> machine is out of calibration, your temperature is 6-degrees too high, it
> needs to be re-cal'ed.." I told her it wasn't, that she should wait until
> we
> finish the boards we were waving so I could shut the pumps off, let the
> pot
> stabilize, and then she could take a reading. Her reply was (which I'm
> getting so sick of); "That's not the way we do it around here..." ARRRRG!
> No
> matter how much I tried to explain about the solder being pumped up to the
> top to the wave formers and cooling down flowing back into the pot, then
> the
> thermocouple in the pot sensing this, turning the heaters on to maintain
> the
> set temperature and that's why the reading was a little high, I couldn't
> get
> through to her...so I gave up.
>
> But what's a realistic slop factor as far as the indicated temperature and
> actual temperature of the solder. I think +/- 5-degrees F is way to tight,
> I
> was thinking more like +/- 15-degrees....any opinions?
>
> Thanks!
>
> -Steve Gregory-
>
> P.S. anybody need a good engineer?
>
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