SMD desoldering tutorial?

[DarkMatter]

On Sun, 4 Jan 2004 14:36:57 -0800, DaveC <me@privacy.net> Gave us:

On Sun, 4 Jan 2004 12:22:52 -0800, Sunny wrote
(in message <uB_Jb.1834$D21.279420@news20.bellglobal.com&gt:

If at all possible, practice on junk hardware first. Each package type
and location presents it's own challenges, and the first attempts often
result in bent pins until you get a feel for the technique.

I need to preserve one set of ROMs from a PCB. This PCB can be trashed; I
have no need for it afterward. The ROMs on another board can be trashed
(they're defective), but the PCB needs to be preserved.

One job I need to be careful with the chips; the other, with the PCB.

Feeler gauges... hmm, I have several old sets of those lying around.

Thanks,

On the PCB with the chips that are trash, cut one lead at a time
until all leads are cut. Remove the chip, then desolder one lead at a
time from their pads. Carefully wick the pads (no pressure, just
heat) clean. That PCB is now ready to accept the new (used) chips.

If they are j-lead (likely). If it is SOIC or fine pitch, the same
thing goes, but it is a little harder to cut the pins.

Anyway, the point is that the chips to be trashed can be removed by
cutting the pins, and then de-soldering the remaining pin segments
from the board individually.

Half way there. You could look up a good contract Mfgr in your
area, and ask what it would cost for removing two PLCC
(j-lead) chips. If they are fine pitch or soic, the quote may be bit
more. J-lead is easy though as hot air can pass under the chip.

They might want like $50 or $100 for the job. Is there no way to
obtain a pair of pre-programmed chips?

 

[DarkMatter]

On Sun, 04 Jan 2004 22:39:55 GMT, John Popelish <jpopelish@rica.net>
Gave us:

DarkMatter wrote:

Considering that 63/37 solder does not melt until it reaches nearly
500 degrees F, I'd say that you just described how to fuck up a PCB.

It is not as bad as all that.
http://www.rfcafe.com/references/electrical/solder.htm

But I am still reluctant to cook boards or components that long.

Yes, but the chamber temp, and lead temp need to be settled in. I
would go higher temp, faster settle.

Most reflow ovens, and wave solder machines only pre-het assemblies
to nearly 350F. The reflow area, and wave area finish the job with
the least component stress.

As long as the cycle is a slow ramp up, the parts should remain
stable.

Of course, this does NOT include any electrolytics or other "wet"
parts that heat can damage.

As an aside, we hd a CPU that looked like an old LCC in micro size.

There were no points to solder to on the chip edge. They were all
underneath it.

Needless to say, this presents a problem for the proto first piece
assy, as they are typically hand assembled.

I used our air bath and heat pencil to no avail. So, I broke out
the big guns. Heat guns to be specific.

The whole key is the preheat. If the heat bath has the PCB assy up
to a high starting temp, the reflow operation should be easy.

Ok. Hot PCB. Hot air gun. It works! We were worried though about
the chip. I re-reflowed it back off with the heat gun, and replaced
it on ther demo PCB.

It worked. It proved our layout to be defective, and proved that
hot air does not a dead chip make.

If this guy can handle the slight risk, that does work. I held the
chip with tweezers as I heated it. As soon as the solder reflowed, I
removed the heat, so it couldn't have been heated much more than it
should have been.

All heat was kept local to the part too. Except for the air bath,
of course.

Anyway... it survived at least 4 cycles of that, and still works.
It is a cpu with 8k of flash in it.

Very doable, unless he s a huge long term reliability issue with the
heat damage potential. I would try to copy the chips after removal,
and insert new chips.

 

[DarkMatter]

On Sun, 04 Jan 2004 22:46:31 GMT, Robert Grizzard
<grizzarv@mindspring.com.invalid> Gave us:

http://www.kester.com/alloy_temp_chart.html

HTH

The difference between a chart and reality can be sharp.

I do not know of anyone that can successfully solder AT ALL at those
temperatures. The settle time for an assy placed in an oven that
barely makes said temperature is way too high for me.

I would ramp it up from a 250 F oven, into a 350F oven, and then use
hot air for the removal. Much less stressful.

I would also STILL bet that full reflow on that many pins requires a
temp were one can be sure that all pins are molten. Being right at or
near the charted melt point temp is NOT that assured temp.

HTH

 

[Garrett Mace]

Given your requirement is to avoid damage to the SMD components, I
assume you need to re-use them?

As Tim H. posted, Chipquik is ideal for SMD removal by hand as it allows
you to reflow solder at temperatures low enough to avoid heat damage to
the board or component - the tricky part is removing and cleaning the
component without bending any pins. Most of the SMD rework information
available assumes devices will be discarded after removal.

I had to replace an FPGA on a development board once. I used a $20 heat gun
clamped in a partially-completed CNC machine I was building. It only takes a
few seconds for the solder to melt when the heat gun is on its lowest
setting. I also used the heat gun to solder on the new FPGA, then touched up
a few pins with a soldering iron. Ideally there would be a heat shield to
prevent heating up other components, but in this case it wasn't a problem.
The pins heat up so much faster than the rest of the chip; all you need to
do is keep the internal temperature of the device less than 450 degrees F.
Here's a photo of the removed chip:
http://www.macetech.com/desolder-close.jpg

 

[Ralph & Diane Barone]

Gingerly stepping around the current arguments about theft, etc...

Would the device shown on www.usbmicro.com/odn/index.html work in reverse?
Would an aquarium pump pull enough vacuum to desolder? It would be nice to
be able to do single-handed desoldering without shelling out hundreds of
dollars.

 

[DarkMatter]

On Mon, 05 Jan 2004 00:09:56 GMT, rdbarone@shaw.ca (Ralph & Diane
Barone) Gave us:

Gingerly stepping around the current arguments about theft, etc...

Would the device shown on www.usbmicro.com/odn/index.html work in reverse?
Would an aquarium pump pull enough vacuum to desolder? It would be nice to
be able to do single-handed desoldering without shelling out hundreds of
dollars.

Putting together a bench model from garage shelf parts is likely

going to cost several hours of someone's time.

My time is worth a lot.

Check e-bay. One can get such equipment for pennies on the dollar.

 

[Sunny]

DaveC wrote:

On Sun, 4 Jan 2004 12:22:52 -0800, Sunny wrote
(in message <uB_Jb.1834$D21.279420@news20.bellglobal.com&gt:


If at all possible, practice on junk hardware first. Each package type
and location presents it's own challenges, and the first attempts often
result in bent pins until you get a feel for the technique.


I need to preserve one set of ROMs from a PCB. This PCB can be trashed; I
have no need for it afterward. The ROMs on another board can be trashed
(they're defective), but the PCB needs to be preserved.

In that case my approach would be to remove the defective ROMS first.

With Chipquik and a temperature controlled iron, preferably at 300F but
not more than 350F, there's virtually no possibility of damaging the
PCB, so removing and cleaning the defective parts can be treated as a
practice session prior to working on the parts you need to preserve and
re-install.

If you plan to use the continuous flow method of reinstallation,
practicing by installing one or two defective parts on the trash PCB
first would also be a good plan - the temperature and solder volume need
to be just right to avoid dry joints or bridges between pins, and
bridges can be quite difficult to wick off without increasing
temperature beyond the ideal. I wasn't aware cupped SMD flow tips were
available for my station until I followed the links posted earlier, but
I plan to order one tomorrow

I have been posting to this thread under the assumption you are dealing
with fine pitch (0.5mm) gull wing lead devices, SSOP or QFP/LQFP. I have
no experience with using the techniques I've described on J-lead
devices, and after looking at a couple I expect it might be difficult to
flow Chipquik under the device to where much of the solder is.

Another post suggested cutting the leads to remove defective devices,
however that's not an approach I'd use on fine pitch leads as there is a
risk of damaging PCB pads due to mechanical stress.

One job I need to be careful with the chips; the other, with the PCB.

Feeler gauges... hmm, I have several old sets of those lying around.

The dental bands I use are .002" thick

 

[Mac]

On Sun, 04 Jan 2004 22:05:43 +0000, nobod wrote:

In article <7irgvv0mecuc1vkjjk9k978b06oh9no2sp@4ax.com>,
maxfooHeadFromButt@punkass.com says...
So let the guy know he's a plagiarist, his email is contact@nanosistemas.com

You don't think he knows? He copied. It should be the school that should
be emailed.

There are no published references to this idea any earlier than the
first publication of the app note on the usbmicro site (and in the
archives of PIClist) [as far as I am able to discover]. The idea is
there on the net for anyone to use as they wish. But any student that
can't cite sources and only slightly alters the text of the plagiarized
information is the type of person that ends up causing a lawsuit for a
company. Again, I wouldn't want such a person working for me. He would
probably never learn to do his own work if he can just steal.

There are a lot of people that can steal an idea, slightly alter it, and
claim that they did all of the original work. These people are not worth
half of a good engineer that can create new ideas. Even an engineer that
uses example material - but makes it clear that the material came from
another source - is of more value than someone that just steals.

Frankly I can imagine that this student has a hard drive full of stolen
music and doesn't think anything of it.

You are talking about copyright infringement, not theft. One major
difference is that if you steal physical property, you deprive the
rightful owner of possesion. In copyright infringement, there is no such
deprivation. Also, there are some legally established justifications for
copying copyright-protected materials. That is to say, not every
unauthorized copy of copyrighted material is punishable under law, at
least in the US.

I do not practice copyright infringement, and I don't endorse it, but I do
think it is important to make the distinction between theft and copyright
infringement.

Not a big leap to stealing
property. [snip]

This seems to be an assertion that requires proof.

Mac

 

In article <pan.2004.01.05.02.55.35.312617@bar.net>, foo@bar.net says...

You are talking about copyright infringement, not theft.
snip
I do not practice copyright infringement, and I don't endorse it, but I do
think it is important to make the distinction between theft and copyright
infringement.

Valid: I don't know everything about copyright laws either. Legal or
illegal (to US law), isn't worth fighting about. I guess just seeing the
plagairism irked me. Worth a lawsuit? No.

Just not good behavior, in my book.

 

In article <BC1DEB59966816FB93@192.168.0.>, rdbarone@shaw.ca says...

Gingerly stepping around the current arguments about theft, etc...

Would the device shown on www.usbmicro.com/odn/index.html work in reverse?
Would an aquarium pump pull enough vacuum to desolder? It would be nice to
be able to do single-handed desoldering without shelling out hundreds of
dollars.

The low cost pumps dont have a tube as an input. Wouldn't the iron cool
too much with continous input airflow? Perhaps?

 

[John Popelish]

DaveC wrote:
(snip)

Feeler gauges... hmm, I have several old sets of those lying around.

Rolls of stainless steel shim stock are not very expensive. You can
cut the thinner sizes with sharp scissors.

http://www.precisionbrand.com/products/default.asp?p_catid=222

--
John Popelish

 

[Si Ballenger]

On Sun, 04 Jan 2004 22:05:43 GMT, <nobody@nowhere.com> wrote:

In article <7irgvv0mecuc1vkjjk9k978b06oh9no2sp@4ax.com>,
maxfooHeadFromButt@punkass.com says...
So let the guy know he's a plagiarist, his email is contact@nanosistemas.com

You don't think he knows? He copied. It should be the school that should
be emailed.

There are no published references to this idea any earlier than the
first publication of the app note on the usbmicro site (and in the
archives of PIClist) [as far as I am able to discover]. The idea is
there on the net for anyone to use as they wish. But any student that
can't cite sources and only slightly alters the text of the plagiarized
information is the type of person that ends up causing a lawsuit for a
company. Again, I wouldn't want such a person working for me. He would
probably never learn to do his own work if he can just steal.

There are a lot of people that can steal an idea, slightly alter it, and
claim that they did all of the original work. These people are not worth
half of a good engineer that can create new ideas. Even an engineer that
uses example material - but makes it clear that the material came from
another source - is of more value than someone that just steals.

Frankly I can imagine that this student has a hard drive full of stolen
music and doesn't think anything of it. Not a big leap to stealing
property. Sad.

Have you checked for patents on this type of gizmo? I would think
usbmicro would get a patent on this if it is their origional
idea. I bet they improvised their own version of an existing
tool.

 

[DarkMatter]

On Mon, 05 Jan 2004 04:34:32 GMT, shb*NO*SPAM*@comporium.net (Si
Ballenger) Gave us:

Have you checked for patents on this type of gizmo? I would think
usbmicro would get a patent on this if it is their origional
idea. I bet they improvised their own version of an existing
tool.

Our company owns a product that we bought several years ago.

The idea of a hot air pencil has been around for decades.
The one we use has a diaphragm pump in it.

If anything, they *stole* it from the rest of the world.
Several product are available from several makers.

Sheesh.

 

[Roger Gt]

<nobody@nowhere.com> wrote in message
news:MPG.1a6295d9f57f8650989697@news.starband.net...

In article <BC1DEB59966816FB93@192.168.0.>, rdbarone@shaw.ca says...
Gingerly stepping around the current arguments about theft, etc...

Would the device shown on www.usbmicro.com/odn/index.html work in
reverse?
Would an aquarium pump pull enough vacuum to desolder? It would be nice
to
be able to do single-handed desoldering without shelling out hundreds of
dollars.

The low cost pumps don't have a tube as an input. Wouldn't the iron cool
too much with continuous input airflow? Perhaps?

The Desoldering iron is about 20 Watts. The airflow from an aquarium pump
is quite limited. With the Steel Wool to distribute the heat and impede the
air flow there is ample power to heat the passing air to the temperature
needed to flow a small volume of solder. In my experience it would be of no
value for anything of significant size, like the tab on a power device.

Without air the temperature will rise to about 800 degrees F. It is not
regulated!

For desoldering there are pumps with a fitting on the input, but I never
tried anything like that.
I made my own hot air soldering units from Quartz tubing and NiChrome heater
wire, but the element is about 20 watts, so the result is nearly the same!

 

[cornytheclown]

"Mac" <foo@bar.net> wrote in message news:<pan.2004.01.05.02.55.35.312617@bar.net>...

On Sun, 04 Jan 2004 22:05:43 +0000, nobod wrote:

In article <7irgvv0mecuc1vkjjk9k978b06oh9no2sp@4ax.com>,
maxfooHeadFromButt@punkass.com says...
So let the guy know he's a plagiarist, his email is contact@nanosistemas.com

You don't think he knows? He copied. It should be the school that should
be emailed.

There are no published references to this idea any earlier than the
first publication of the app note on the usbmicro site (and in the
archives of PIClist) [as far as I am able to discover]. The idea is
there on the net for anyone to use as they wish. But any student that
can't cite sources and only slightly alters the text of the plagiarized
information is the type of person that ends up causing a lawsuit for a
company. Again, I wouldn't want such a person working for me. He would
probably never learn to do his own work if he can just steal.

There are a lot of people that can steal an idea, slightly alter it, and
claim that they did all of the original work. These people are not worth
half of a good engineer that can create new ideas. Even an engineer that
uses example material - but makes it clear that the material came from
another source - is of more value than someone that just steals.

Frankly I can imagine that this student has a hard drive full of stolen
music and doesn't think anything of it.

You are talking about copyright infringement, not theft. One major
difference is that if you steal physical property, you deprive the
rightful owner of possesion. In copyright infringement, there is no such
deprivation. Also, there are some legally established justifications for
copying copyright-protected materials. That is to say, not every
unauthorized copy of copyrighted material is punishable under law, at
least in the US.

I do not practice copyright infringement, and I don't endorse it, but I do
think it is important to make the distinction between theft and copyright
infringement.

Not a big leap to stealing
property. [snip]

This seems to be an assertion that requires proof.

Mac

He took the page down............

Remember how the interent was supposed to be this great free exchange
of information ??? Now its become a commercialized porn emporium and
the basis for a great many lawsuits. Even usenet has become a place
more for personal rants and personal fights between posters....People
coming here looking for help or discussion are just as likely to be
cussed out in a fiery tirade of flames than they are to get honest
decent help.

I do agree the kid should not have copied information without giving
due credit but who is to say that the originator of the idea did not
know about the page and just didnt care.

I see many many pages with the same exact electronic circuits and no
credit is given to the original designer, even the big semiconductor
companies must realize that half the info from their datasheets is out
on the net on someones presonal web page with no credit given to
them,of course with the semi companies I guess if someone builds the
circuit they sell an ic, if the builder uses their brand....

 

[Garrett Mace]

The low cost pumps dont have a tube as an input. Wouldn't the iron cool
too much with continous input airflow? Perhaps?

You're probably right.

I'd suggest just attaching the bulb to the end of the tube, and stepping on
it to create a foot-activated vaccum bulb. Probably could devise a more
elegant bellows solution if necessary.

 

[Active8]

On Sun, 04 Jan 2004 17:14:58 GMT, nobody@nowhere.com said...

In article <MPG.1a6205647fbe38e1989692@news.starband.net>,
nobody@nowhere.com says...
In article <0001HW.BC1D2B5B0013B776F0080600@news.individual.net>,
me@privacy.net says...
I need to desolder (with no damage to the components) some SMD ROM chips. Is
there a good tutorial somewhere on the 'net about how to go about this?

BTW, I found a great tutorial on technique and equipment (lo-cost, some of it
make-yourself) on the 'net about soldering SMDs:

http://www.wku.edu/~barceed/SolderPage/index.htm

Thanks,


The author of that page - Eduardo Barcellos - should consider giving
proper credit to the original source of his idea
(www.usbmicro.com/odn/index.html). He presents the hot-air idea as if it
were his own.

I was going to ask what made you think that he didn't come up with
the idea on his own but your comparison of the write ups kinda
makes it look like the guy cheated. What a guy.

I thought of this around 9 years ago when I first bought that
desoldering iron and the obvious thing to me was to connect an
aquarium pump. Never got around to building one. I wonder if one of
those curly metal kitchen scrub pads would work. I was thinking of
rigging a larger metal tube to the iron head so I could apply
vacuum and the curly stuff would catch the solder just like the
metal strip in a real solder-sucker and it wouldn't restrict the
air flow as much as steel wool. A regular hot air station has an
air control, so rather than using a motor control, you could just
use one of those deals (or whatever) that (used to be used to, if
they're not used at all any more,) control the drip on an IV tube
by restricting the tube. Then when your done with the soldering
ops, you just disconnect both ends of the tube and reconnect your
coffee IV.

I forgot to mention to scroll down to the "Hot Ait Pencil" note.


It is an unfortunate trend that students steal ideas from the internet
and boldly present the information without due credit. A whole
generation of people without morals would be the downfall of society.

See above.
--
Best Regards,
Mike

 

[Active8]

On Sun, 04 Jan 2004 18:55:41 -0800, foo@bar.net said...

On Sun, 04 Jan 2004 22:05:43 +0000, nobod wrote:

In article <7irgvv0mecuc1vkjjk9k978b06oh9no2sp@4ax.com>,
maxfooHeadFromButt@punkass.com says...
So let the guy know he's a plagiarist, his email is contact@nanosistemas.com

You don't think he knows? He copied. It should be the school that should
be emailed.

There are no published references to this idea any earlier than the
first publication of the app note on the usbmicro site (and in the
archives of PIClist) [as far as I am able to discover]. The idea is
there on the net for anyone to use as they wish. But any student that
can't cite sources and only slightly alters the text of the plagiarized
information is the type of person that ends up causing a lawsuit for a
company. Again, I wouldn't want such a person working for me. He would
probably never learn to do his own work if he can just steal.

There are a lot of people that can steal an idea, slightly alter it, and
claim that they did all of the original work. These people are not worth
half of a good engineer that can create new ideas. Even an engineer that
uses example material - but makes it clear that the material came from
another source - is of more value than someone that just steals.

Frankly I can imagine that this student has a hard drive full of stolen
music and doesn't think anything of it.

You are talking about copyright infringement, not theft. One major
difference is that if you steal physical property, you deprive the
rightful owner of possesion. In copyright infringement, there is no such
deprivation. Also, there are some legally established justifications for
copying copyright-protected materials. That is to say, not every
unauthorized copy of copyrighted material is punishable under law, at
least in the US.

For one thing, there's an implied copyright on anything original
that you wright, but you can't enforce it until it's registered.
Then you get into other little details which I forget, but theres
at least one decent site out there that covers the major points.

I do not practice copyright infringement,

Is that why you're so bad at it?

and I don't endorse it, but I do
think it is important to make the distinction between theft and copyright
infringement.

Good point. I think c infringement becomes a type of theft (like
theft, not a type of theft in the eyes of the courts) when it
deprives the author of revenue that would otherwise have been
gained from the sale of said c'd mat'l.

Not a big leap to stealing
property. [snip]

This seems to be an assertion that requires proof.

You're more likely to get shot stealing property.

Mac
--

Best Regards,
Mike

 

[Active8]

On Mon, 05 Jan 2004 03:18:10 GMT, nobody@nowhere.com said...

In article <pan.2004.01.05.02.55.35.312617@bar.net>, foo@bar.net says...

You are talking about copyright infringement, not theft.
snip
I do not practice copyright infringement, and I don't endorse it, but I do
think it is important to make the distinction between theft and copyright
infringement.

Valid: I don't know everything about copyright laws either. Legal or
illegal (to US law), isn't worth fighting about. I guess just seeing the
plagairism irked me. Worth a lawsuit? No.

Just not good behavior, in my book.

Then *your* book's been plagiarized repeatedly and yet knowing

this should make you feel better.

--
Best Regards,
Mike

 

[Active8]

On Sun, 04 Jan 2004 12:17:41 -0800,
DarkMatter@thebarattheendoftheuniverse.org said...

On Sun, 04 Jan 2004 18:56:09 GMT, <nobody@nowhere.com> Gave us:


USBmicro originated the idea - at least this specific combination of
iron, fish pump, and stuffed steel wool.

Bullshit.

No kidding. I say it's an obvious solution even if you've never

seen a hot-air station, which I hadn't when I though of this 9
years ago. I'd heard of them and I knew the solder-sucker used a
diaphragm pump. The guy who showed me how to service the thing said
it was basically an aquarium pump. I just can't remember if the
idea came to me on the way home from RS, while I was there, or
after I got home and fired it up and blew a little hot air on my
finger.

--
Best Regards,
Mike