4 Jun
2000
4 Jun
'00
3:58 p.m.
Hi,
This isn't strictly on-topic, but I guess it could be applied to maintaining
classic stuff, so...
Can anyone recommend a way of removing surface-mounted ICs (specifically SOJ
package DRAM chips) from a board? It's not critical to keep the board
undamaged, but the chips must be kept intact since I want to solder them into
another device.
I read of a technique involving turning the board upside-down and heating the
board area opposite the ICs in question with a blowtorch. The ICs drop off
when the solder melts. I don't have a blowtorch, but do have a gas stove.
Heating the board over the stove will probably not be a good idea, since the
ICs would need to be lifted off when the solder melts. Since I want to
recover several chips, they are likely to get too hot doing it this way.
I do have an electric grill. The element is at the top of the oven. What about
putting the board component side down in the oven (near the heating element),
and heating until the solder melts?
It will be important to get the temperature profile right here, I think.
Putting the board straight into a hot oven might not be a good idea, but on
the other hand having it in the oven as it warms up from cold may be too
long.
In a way, doing this would be similar to IR reflow soldering.
What is a typical melting temperature for solder used on surface-mount
components? The oven control goes up to 260 Celsius (from memory), which I
hope is high enough.
Has anyone else attempted something like this? Do you have any advice?
I guess the same technique could also be used for soldering surface-mount
components (with board component side up, and solder paste applied to the
pads).
-- Mark
4 Jun
4 Jun
1:21 p.m.
From: Mark <mark_k(a)iname.com>
To: classiccmp <classiccmp(a)classiccmp.org>
Date: Mon, 05 Jun 2000 00:58:27 +0000
Subject: Removing surface-mounted ICs
Reply-to: classiccmp(a)classiccmp.org
Hi,
Heating the board over the stove will probably not be a good idea, since the
ICs would need to be lifted off when the solder melts. Since I want to
recover several chips, they are likely to get too hot doing it this way.
I do have an electric grill. The element is at the top of the oven. What about
putting the board component side down in the oven (near the heating element),
and heating until the solder melts?
Get a old heavy alumium baking pan and start cooking on electric or
gas. Heat on high starting with piece of solder wire dabbling
the pan till solder melts and balls up then turn low bit towards
medium. Wait for few minutes, then tap the chips you want to take
till it is free and pick them up with tweezers or needle long nose
pliers. I often find the melting point of solder is hot enough even
on low on any stoves.
Warning: It will smell if heat is too high.
For those dual SOJ or gull wing (not the quad SOJ/gullwing kind), I
take two 40W solder irons (grounded) and melt excessive solder acts
as heat capacity to keep solder molten and keep moving both solder
together. Till chip is loose then pinch the chip with the solder
iron tips quickly lift up and let it drop on the metal or cardboard.
Clean leads up with fresh blob of solder dragged across them by
holding the chip vertical using gravity and surface torison do the
work. I do that same for installing all SOJ and gull wing pitch of
.025 by tacking two leads down to hold it in place and solder
excessively then drag the blob, solder will want to leave the leads
and try to run off at the last pin but you can prevent it when
moving the solder tip carefully.
What is a typical melting temperature for solder used
on surface-mount
components? The oven control goes up to 260 Celsius (from memory), which I
hope is high enough.
All cooking of any types are hot enough, over 500F on high without
water load. Heated metals that are glowing red and orange ia over
1000F and bit more. Because of this glow the water has very high
specific heat capacity and that takes so much heat to bring it to
boil quickly and keep it there.
Oh yes can melt cheap aluminum spun thin pots with a stove. I
had this happen few times. Without warning too.
Look at burned buses and airplaces, aluminum melted because fire is
hot enough.
-- Mark
Wizard
4:19 p.m.
You use solder wick. You lay it over the pins, you wick up the solder that
is holding them down. Alternatively you use a suction grabber device and a
very small torch or hot air gun. (the latter is preferred). Attach the
pickup to the top of the chip, then blow the hot air gun on it, and lift it
off.
--Chuck
At 12:58 AM 6/5/00 +0000, you wrote:
Can anyone recommend a way of removing surface-mounted
ICs (specifically SOJ
6:52 p.m.
The solder wick method can work, but one is tempted to lift up on the pins
to pop the part loose, which will deform them forever. If you're better at
it than I am, you might succeed with that method. The gull-wing parts I've
used after using this extraction method have always been a source of
trouble, needing special care to solder them into a new application.
Dick
----- Original Message -----
From: Chuck McManis <cmcmanis(a)mcmanis.com>
To: <classiccmp(a)classiccmp.org>
Sent: Sunday, June 04, 2000 7:19 PM
Subject: Re: Removing surface-mounted ICs
You use solder wick. You lay it over the pins, you
wick up the solder that
is holding them down. Alternatively you use a suction grabber device and a
very small torch or hot air gun. (the latter is preferred). Attach the
pickup to the top of the chip, then blow the hot air gun on it, and lift
it
off.
--Chuck
At 12:58 AM 6/5/00 +0000, you wrote:
>Can anyone recommend a way of removing surface-mounted ICs (specifically
SOJ
8:33 p.m.
The classic way of removing SOJ parts is to use two soldering irons and a
big blob of solder on both rows of pins. The solder blobs heat all the
pins simultaneously and the chip can be slid right off.
Also, you'll be removing the chip without damage -and- you can easily
clean up the PC pads to install a new chip.
It's a great Silicon Valley hack I've see here performed many times.
-Mike
On Sun, 4 Jun 2000, Richard Erlacher wrote:
The solder wick method can work, but one is tempted to
lift up on the pins
to pop the part loose, which will deform them forever. If you're better at
it than I am, you might succeed with that method. The gull-wing parts I've
used after using this extraction method have always been a source of
trouble, needing special care to solder them into a new application.
Dick
----- Original Message -----
From: Chuck McManis <cmcmanis(a)mcmanis.com>
To: <classiccmp(a)classiccmp.org>
Sent: Sunday, June 04, 2000 7:19 PM
Subject: Re: Removing surface-mounted ICs
You use solder wick. You lay it over the pins,
you wick up the solder that
is holding them down. Alternatively you use a suction grabber device and a
very small torch or hot air gun. (the latter is preferred). Attach the
pickup to the top of the chip, then blow the hot air gun on it, and lift
it
off.
--Chuck
At 12:58 AM 6/5/00 +0000, you wrote:
>Can anyone recommend a way of removing surface-mounted ICs (specifically
SOJ
5 Jun
5 Jun
3:42 a.m.
my hack is a bit cleaner...
Two weller or ungar elements with various sized screw on blocks of copper
that have been shaped for the job of heating both sides at once mounted in
a handle that is adjustable. Workes well for boards being repaird. for
non working board and salvage parts I tourch them off directly or use
some tooled copper to heat specific parts. Years of stripping salvage
for choice transistors and what not gained me good practice.
Allison
6:19 a.m.
The thing I've noticed over the past few years is that there are more and
more really small parts that could be of use once you've relegated your
subject board to the rubbish heap. Space is always a problem in small
circuits and I've dealt with that to large extent by using the small
components that are on many of today's dense boards. Keeping them from
getting too hot is fairly important, though I've had pretty good yields.
Once I've determined I'll sacrifice a board for its components, I put a
cookie sheet with about 3.8" of water in it on the table on my patio. Then,
I start by heating the back side of any through-hole components I want to
salvage, often using a tool to remove them from the board. Then, I go after
the front-side surface-mounted parts, not heating them directly, but heating
the space between them, i.e. heating the pads where they're soldered to the
board. Once those are thoroughly heated, (usually with light charring and
blistering in the case of multilayered boards) I rap the board's component
side against the edge of the table, causing the loose components to fall
into the water in the cookie sheet. I don't know how well this works for
cooling the larger parts, but I've had pretty good luck all around. I find
it much more difficult to find out the values of the passives that end up in
the cookie sheet, which are pretty handy for sticking a "fix" on the back of
an IC, but it surely doesn't hurt them, and it keeps them from bouncing all
over the place.
After I'm done, there are very few bent pins and all I have to do is pour
the water through a sieve to get the teensy little passives, SOT's etc.
Then I can spend endless hours picking out these SO parts and trying to
figure out what's what. It's not much fun, but it beats watching TV.
Dick
4 Jun
4 Jun
6:50 p.m.
The blowtorch has served me well in this context. When a board is not
important to you and the components are, it's possible to do that with a
propane torch of the inexpensive variety. It's important that they put out
considerable heat, however. I've found my Weller butane torch to be not
terribly useful in this regard. You can use a typical butane torch of the
type you normally use to solder copper plumbing to heat the component leads,
and quickly if that's possible. I often char the board but if you make the
traces come off along with the IC, you're probably overdoing it. Normally,
I heat the board from the component side in the case of surface mounted
parts, knocking it against the table. Unless you really want to make
yourself sick, this is best done outdoors. Afterward, in fact, immediately
afterward, it's advisable to toss your clothing worn during this process
into the laundry. A shower will relieve the pungent odor, somewhat
garlic-like that you'll put out for the rest of the time before your next
ablution.
My luck has been remarkably good using this technique, but there have been
occasions when it wasn't so good.
Dick
----- Original Message -----
From: Mark <mark_k(a)iname.com>
To: classiccmp <classiccmp(a)classiccmp.org>
Sent: Sunday, June 04, 2000 6:58 PM
Subject: Removing surface-mounted ICs
Hi,
This isn't strictly on-topic, but I guess it could be applied to
maintaining
classic stuff, so...
Can anyone recommend a way of removing surface-mounted ICs (specifically
SOJ
package DRAM chips) from a board? It's not
critical to keep the board
undamaged, but the chips must be kept intact since I want to solder them
into
another device.
I read of a technique involving turning the board upside-down and heating
the
board area opposite the ICs in question with a
blowtorch. The ICs drop off
when the solder melts. I don't have a blowtorch, but do have a gas stove.
Heating the board over the stove will probably not be a good idea, since
the
ICs would need to be lifted off when the solder melts.
Since I want to
recover several chips, they are likely to get too hot doing it this way.
I do have an electric grill. The element is at the top of the oven. What
about
putting the board component side down in the oven
(near the heating
element),
and heating until the solder melts?
It will be important to get the temperature profile right here, I think.
Putting the board straight into a hot oven might not be a good idea, but
on
the other hand having it in the oven as it warms up
from cold may be too
long.
In a way, doing this would be similar to IR reflow soldering.
What is a typical melting temperature for solder used on surface-mount
components? The oven control goes up to 260 Celsius (from memory), which I
hope is high enough.
Has anyone else attempted something like this? Do you have any advice?
I guess the same technique could also be used for soldering surface-mount
components (with board component side up, and solder paste applied to the
pads).
-- Mark
5 Jun
5 Jun
9:10 a.m.
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1:17 p.m.
ard(a)p850ug1.demon.co.uk (Tony Duell) wrote:
The
best tool to use is a hot air blower. About the best sort of those is
one of those gas-powered soldering irons (the ones that run on butane
lighter fuel) with a hot air blower tip. Run it round the IC, and you'll
find that the solder melts and the chip will come off easily enough.
I have heard of the paint-stripper type of hot air gun being used for
this, with a suitable small-diameter nozzle. But I've never tried that.
Hi
I've used the shrink tubing guns and they work OK. These
are a little more controlled than a blow torch.
For a large boards of dual inline IC's, I've use peanut oil.
It has a high enough temperature that it can melt solder,
with a frying pan. I use some long tweezer. To keep them
cool I use a fan ( Don't put them in water. A drop of
water in the oil will be explosive. ). When done, I wash
the parts in dish soap.
Regardless of which you use, make sure to wear eye protection!!!
Dwight
4:33 p.m.
Be aware that most manufacturers do not recomend
reusing desoldered
surface-mount devices. That said, it seems to be possible to remove and
Not exactly in their best interest to tell you go ahead and reuse the old
parts.
The best tool to use is a hot air blower. About the
best sort of those is
Doesn't anybody have a solder pot? Thats what pretty much all the scrappers
I know use to remove parts.
3:52 p.m.
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7:43 p.m.
It does better for the PCB if you use hot air, but it takes longer, and
that's longer for the heat to get to the inards of the IC, which, if you're
not inclined to save the PCB, is a good thing to avoid. BTW, with ceramic
parts, the water thing I mentioned in an earlier transimission may not be as
good an idea. I've torched many a plastic part successfully, however.
The hot air approach left me trying to aid the process mechanically,
resulting in a hellish task getting the j-leads properly aligned for future
socketing. Gull-wing parts seem to fare somewhat better, though at .025"
pin pitch it gets a mite difficult finding just the right amount of
deflections so they don't have to be nursed when resoldering them.
The manufacturers are probably not concerned about the 100 or so parts all
of us together will cost them in sales in a year as much as they're
concerned about the frustrated phone calls to their rep's or FAE's wondering
why the parts don't work the way they should.
Dick
----- Original Message -----
From: Tony Duell <ard(a)p850ug1.demon.co.uk>
To: <classiccmp(a)classiccmp.org>
Sent: Monday, June 05, 2000 6:52 PM
Subject: Re: Removing surface-mounted ICs
is
>
> >Be aware that most manufacturers do not recomend reusing desoldered
> >surface-mount devices. That said, it seems to be possible to remove and
>
> Not exactly in their best interest to tell you go ahead and reuse the
old
parts.
True, but I've never seen a similar comment in a databook or service
manual for pin-through-hole parts. But it's in just about every
databook/service manual/etc for SMD ones.
>
> >The best tool to use is a hot air blower. About the best sort of those >
> Doesn't anybody have a solder pot? Thats what pretty much all the
scrappers
I know use to
remove parts.
I must admit that I've never been in the position of caring more about
the component than the PCB. Every time I've wanted to remove an SMD part,
it's been essential to preserve the (probably irreplaceable) PCB.
Many times I've managed to separate them without damaging either part
using the hot air tool, though.
-tony
6 Jun
6 Jun
9:17 p.m.
Hi Mark,
I would recommend against putting the board in an oven. This will
result in the entire IC getting too hot, and possibly breaking.
Modern plastic package absorb a small amount of water from the air.
Heating the part may result in a small steam explosion. ICs are
shipped from the factory in sealed bags with some desiccant inside.
The label on the outside says to solder them down within a fairly
short time after opening (couple days IIRC).
That being said, you can pick up a small propane torch at most
hardware stores. Any typical propane or MAPP type torch will do. Or you
can use a dremel (or equivalent) to carve enough of the board away
to unsolder one pad at a time (very slow, but the only way to remove
plastic shrouded connectors without destroying them).
Finally, I have access to a hot air desoldering station at work, and
can desolder them for you. Contact me OL for this option.
clint
vaxman(a)uswest.net
On Mon, 5 Jun 2000, Mark wrote:
Hi,
This isn't strictly on-topic, but I guess it could be applied to maintaining
classic stuff, so...
Can anyone recommend a way of removing surface-mounted ICs (specifically SOJ
package DRAM chips) from a board? It's not critical to keep the board
undamaged, but the chips must be kept intact since I want to solder them into
another device.
I read of a technique involving turning the board upside-down and heating the
board area opposite the ICs in question with a blowtorch. The ICs drop off
when the solder melts. I don't have a blowtorch, but do have a gas stove.
Heating the board over the stove will probably not be a good idea, since the
ICs would need to be lifted off when the solder melts. Since I want to
recover several chips, they are likely to get too hot doing it this way.
I do have an electric grill. The element is at the top of the oven. What about
putting the board component side down in the oven (near the heating element),
and heating until the solder melts?
It will be important to get the temperature profile right here, I think.
Putting the board straight into a hot oven might not be a good idea, but on
the other hand having it in the oven as it warms up from cold may be too
long.
In a way, doing this would be similar to IR reflow soldering.
What is a typical melting temperature for solder used on surface-mount
components? The oven control goes up to 260 Celsius (from memory), which I
hope is high enough.
Has anyone else attempted something like this? Do you have any advice?
I guess the same technique could also be used for soldering surface-mount
components (with board component side up, and solder paste applied to the
pads).
-- Mark
7 Jun
7 Jun
8:44 a.m.
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8816
days inactive
8819
days old
14 comments
10 participants
participants (10)
-
allisonp＠world.std.com -
ard＠p850ug1.demon.co.uk -
cmcmanis＠mcmanis.com -
elvey＠hal.com -
jpero＠cgocable.net -
mac＠Wireless.Com -
mark_k＠iname.com -
mikeford＠socal.rr.com -
richard＠idcomm.com -
vaxman＠uswest.net