I bought a Thinkpad X31.
Fails video memory test and the image looks like
it's in 8-bit color mode.
Pushing hard on the motherboard fixes the image.
Lots of googling uncovers many people who've reflowed
the nVidea BGA chip by means varying from oven to hot
air to a blowtorch.
The bad news about this one is that the video BGA
and a RAM BGA are sitting on a carrier that's looks
like it's made out of circuit board material and is also
BGA'd to the mother board.

I'm not optimistic about getting the heat thru the chips
and the carrier to the motherboard without burning up something.

The thing works well enough to surf the web or control stuff.
I'd hate to brick it. Certainly not worth a replacement motherboard
that has or will soon have the same problem.

Anybody got experience reflowing this dual-stack kind of thing?

Thanks,
mike

On Thu, 07 Jul 2011 09:21:16 -0700, mike wrote:

I bought a Thinkpad X31.

I have one on the bench as I write. Nice machine with a few design
defects. The plastic case is really flimsy and easy to crack along
the sides. I have yet to see an X30, X31, or X32 that does NOT have a
crack in the case somewhere. Plastic epoxy will fix it if you don't
care what the result looks like. Mine resembles Frankenstein:
http://802.11junk.com/jeffl/crud/Thinkpad-X31.jpg
X30 on the left, X31 on the right.

Fails video memory test and the image looks like
it's in 8-bit color mode.
Pushing hard on the motherboard fixes the image.
Lots of googling uncovers many people who've reflowed
the nVidea BGA chip by means varying from oven to hot
air to a blowtorch.

The X31 uses an ATI Radeo Mobile 7000 video chip.
http://www.thinkwiki.org/wiki/Category:X31

Before you blame the video chip, carefully inspect the video ribbon
cable. I've had failures with that cable that looked much like a
video chip problem. They're available on eBay for about $7.

The bad news about this one is that the video BGA
and a RAM BGA are sitting on a carrier that's looks
like it's made out of circuit board material and is also
BGA'd to the mother board.

Yep, that's the problem. Hit it with too much heat and it will melt
or burn (I forgot which). I monitor the heat with an IR thermometer.
Not hugely accurate because it's mostly measuring the temperature of
the hot air gun tip, but good enough. It really doesn't take much
heat or time to reflow the solder with the "skirt" of PCB material
around the BGA. Work fast. This should give you an idea of what to
expect:
http://www.youtube.com/watch?v=NJlgPbELL0E
(Drivel: Not the giant blob of Arctic Silver on top of the CPU to the
right. That's about 100 times too much. Oh well).

Incidentally, I just hot air reflowed and fixed 4 out of 6 HP
JetDirect J4169A cards, which have the same style BGA chip.

I'm not optimistic about getting the heat thru the chips
and the carrier to the motherboard without burning up something.

Rosin flux really helps. It largely prevents oxidation (cold solder
joint). It conducts the heat to odd places. It explodes if you get
it too hot.

In my limited experience, a real hot air desoldering station is a
must. You don't really need all the BGA nozzles as a small 3mm nozzle
is usually sufficient. I bought mine on eBay for about $80 with 4
nozzles. I suggest you practice on an old PCB before trying the real
thing. Getting the temperature right and how fast you move the
nozzle, require some practice.

The thing works well enough to surf the web or control stuff.
I'd hate to brick it. Certainly not worth a replacement motherboard
that has or will soon have the same problem.

It's worth saving.

Anybody got experience reflowing this dual-stack kind of thing?

Yep. My success rate was about 2 out of 5 motherboards with that
configuration. Can't win them all. You have a better chance than
most because you can sorta tell where to reflow.

A few hints:
1. Don't push down on the "skirt" while hot. That will cause the
solder balls to migrate across adjacent pads.
2. Use flux even if it makes a mess. I messy working computer is
better than a clean brick.
3. Build a heat shield out of aluminum foil. The hot air will melt
adjacent plastic quite easily.
4. Give it time to cool down.

Good luck.

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com
# http://www.LearnByDestroying.com AE6KS

Jeff Liebermann wrote:
On Thu, 07 Jul 2011 09:21:16 -0700, mike wrote:

I bought a Thinkpad X31.

I have one on the bench as I write. Nice machine with a few design
defects. The plastic case is really flimsy and easy to crack along
the sides. I have yet to see an X30, X31, or X32 that does NOT have a
crack in the case somewhere. Plastic epoxy will fix it if you don't
care what the result looks like. Mine resembles Frankenstein:
http://802.11junk.com/jeffl/crud/Thinkpad-X31.jpg
X30 on the left, X31 on the right.

Fails video memory test and the image looks like
it's in 8-bit color mode.
Pushing hard on the motherboard fixes the image.
Lots of googling uncovers many people who've reflowed
the nVidea BGA chip by means varying from oven to hot
air to a blowtorch.

The X31 uses an ATI Radeo Mobile 7000 video chip.
http://www.thinkwiki.org/wiki/Category:X31

Before you blame the video chip, carefully inspect the video ribbon
cable. I've had failures with that cable that looked much like a
video chip problem. They're available on eBay for about $7.

I discounted the ribbon cable because it fails video ram test
and because it has the same problem at the VGA output connector on the back.
Is there something I'm missing?

The bad news about this one is that the video BGA
and a RAM BGA are sitting on a carrier that's looks
like it's made out of circuit board material and is also
BGA'd to the mother board.

Yep, that's the problem. Hit it with too much heat and it will melt
or burn (I forgot which). I monitor the heat with an IR thermometer.
Not hugely accurate because it's mostly measuring the temperature of
the hot air gun tip, but good enough. It really doesn't take much
heat or time to reflow the solder with the "skirt" of PCB material
around the BGA. Work fast. This should give you an idea of what to
expect:
http://www.youtube.com/watch?v=NJlgPbELL0E
(Drivel: Not the giant blob of Arctic Silver on top of the CPU to the
right. That's about 100 times too much. Oh well).

I watched a bunch of videos, including that one.
Difference is that they all have a BGA mounted directly to the main board.
That intermediate carrier is the wild card. I don't know what to
expect except that it's a thermal insulator and have nothing equivalent
to practice on.
I haven't taken it apart far enough to try to determine if the chip
or the carrier is where the fault lies.

Incidentally, I just hot air reflowed and fixed 4 out of 6 HP
JetDirect J4169A cards, which have the same style BGA chip.

I'm not optimistic about getting the heat thru the chips
and the carrier to the motherboard without burning up something.

Rosin flux really helps. It largely prevents oxidation (cold solder
joint). It conducts the heat to odd places. It explodes if you get
it too hot.

In my limited experience, a real hot air desoldering station is a
must.
I have three temperature controlled air guns. I've made air nozzles
with baffles in the past...way past...to rework gull-wing and J-leaded
packages.
I've got zero experience with BGA and even less with two-layer stacks
of BGA.

I thought I'd build a hollow platform out of bricks and blast it from
underneath with a power-controlled heat gun while I watched the pre-heat
temperature.
Then hit it from the top to reflow it. Sounds like reflow temp
is about 260C. Any recommendations on what air temperature
I oughta use to get there?

You don't really need all the BGA nozzles as a small 3mm nozzle
is usually sufficient. I bought mine on eBay for about $80 with 4
nozzles. I suggest you practice on an old PCB before trying the real
thing. Getting the temperature right and how fast you move the
nozzle, require some practice.

The thing works well enough to surf the web or control stuff.
I'd hate to brick it. Certainly not worth a replacement motherboard
that has or will soon have the same problem.

It's worth saving.

Anybody got experience reflowing this dual-stack kind of thing?

Yep. My success rate was about 2 out of 5 motherboards with that
configuration. Can't win them all. You have a better chance than
most because you can sorta tell where to reflow.


A few hints:
1. Don't push down on the "skirt" while hot. That will cause the
solder balls to migrate across adjacent pads.
2. Use flux even if it makes a mess. I messy working computer is
better than a clean brick.
3. Build a heat shield out of aluminum foil. The hot air will melt
adjacent plastic quite easily.
4. Give it time to cool down.

Good luck.

Thanks, I gotta go find some flux...
mike

Jeff Liebermann wrote:
On Thu, 07 Jul 2011 09:21:16 -0700, mike wrote:

I bought a Thinkpad X31.

I have one on the bench as I write. Nice machine with a few design
defects. The plastic case is really flimsy and easy to crack along
the sides. I have yet to see an X30, X31, or X32 that does NOT have a
crack in the case somewhere. Plastic epoxy will fix it if you don't
care what the result looks like. Mine resembles Frankenstein:
http://802.11junk.com/jeffl/crud/Thinkpad-X31.jpg
X30 on the left, X31 on the right.

Fails video memory test and the image looks like
it's in 8-bit color mode.
Pushing hard on the motherboard fixes the image.
Lots of googling uncovers many people who've reflowed
the nVidea BGA chip by means varying from oven to hot
air to a blowtorch.

The X31 uses an ATI Radeo Mobile 7000 video chip.
http://www.thinkwiki.org/wiki/Category:X31

Before you blame the video chip, carefully inspect the video ribbon
cable. I've had failures with that cable that looked much like a
video chip problem. They're available on eBay for about $7.

The bad news about this one is that the video BGA
and a RAM BGA are sitting on a carrier that's looks
like it's made out of circuit board material and is also
BGA'd to the mother board.

Yep, that's the problem. Hit it with too much heat and it will melt
or burn (I forgot which). I monitor the heat with an IR thermometer.
Not hugely accurate because it's mostly measuring the temperature of
the hot air gun tip, but good enough. It really doesn't take much
heat or time to reflow the solder with the "skirt" of PCB material
around the BGA. Work fast. This should give you an idea of what to
expect:
http://www.youtube.com/watch?v=NJlgPbELL0E
(Drivel: Not the giant blob of Arctic Silver on top of the CPU to the
right. That's about 100 times too much. Oh well).

Incidentally, I just hot air reflowed and fixed 4 out of 6 HP
JetDirect J4169A cards, which have the same style BGA chip.

I'm not optimistic about getting the heat thru the chips
and the carrier to the motherboard without burning up something.

Rosin flux really helps. It largely prevents oxidation (cold solder
joint). It conducts the heat to odd places. It explodes if you get
it too hot.

In my limited experience, a real hot air desoldering station is a
must. You don't really need all the BGA nozzles as a small 3mm nozzle
is usually sufficient. I bought mine on eBay for about $80 with 4
nozzles. I suggest you practice on an old PCB before trying the real
thing. Getting the temperature right and how fast you move the
nozzle, require some practice.

The thing works well enough to surf the web or control stuff.
I'd hate to brick it. Certainly not worth a replacement motherboard
that has or will soon have the same problem.

It's worth saving.

Anybody got experience reflowing this dual-stack kind of thing?

Yep. My success rate was about 2 out of 5 motherboards with that
configuration. Can't win them all. You have a better chance than
most because you can sorta tell where to reflow.

A few hints:
1. Don't push down on the "skirt" while hot. That will cause the
solder balls to migrate across adjacent pads.
2. Use flux even if it makes a mess. I messy working computer is
better than a clean brick.
3. Build a heat shield out of aluminum foil. The hot air will melt
adjacent plastic quite easily.
4. Give it time to cool down.

Good luck.

Flux turned out to be a much more difficult question than I thought.
What flux do you recommend?

On Thu, 07 Jul 2011 21:29:05 -0700, mike wrote:

Jeff Liebermann wrote:

I discounted the ribbon cable because it fails video ram test
and because it has the same problem at the VGA output connector on the back.
Is there something I'm missing?

Ok. It's not the ribbon cable.

I watched a bunch of videos, including that one.
Difference is that they all have a BGA mounted directly to the main board.
That intermediate carrier is the wild card. I don't know what to
expect except that it's a thermal insulator and have nothing equivalent
to practice on.

Well, the real test is at what point the solder melts. Try taking
small pieces of solder and scattering them onto a PCB. You might have
to glue them down with some Cyanoacrylate adhesive. Then play with
the hot air SMT rework gun to see what it takes to melt the solder.

I haven't taken it apart far enough to try to determine if the chip
or the carrier is where the fault lies.

I'll remove the kbd from my A31 and see what I can find. I don't
recall seeing a video carrier board, but it's possible. Hopefully,
you wont have to remove the PCB in order to do the reflow.

I have three temperature controlled air guns. I've made air nozzles
with baffles in the past...way past...to rework gull-wing and J-leaded
packages.
I've got zero experience with BGA and even less with two-layer stacks
of BGA.

Good. You have proper tools. Think of it as using a soldering iron
made of air. Practice with any PCB at melting solder and removing
parts. It's not a perfect analogy of the X31, but it will help with
the temperature and timing. I don't recall if the X31 uses ROHS high
temp solder, or leaded low temp.

I thought I'd build a hollow platform out of bricks and blast it from
underneath with a power-controlled heat gun while I watched the pre-heat
temperature.

I don't know if that will work. You're blowing air into a dead end
"box" canyon, where most of the air is going to blow back towards the
nozzle. It will probably spray hot air in a much larger area than
intended. Try doing it very quickly, and check the result with a fast
acting contact thermometer (thermocouple and DVM).

Then hit it from the top to reflow it. Sounds like reflow temp
is about 260C. Any recommendations on what air temperature
I oughta use to get there?

Nope, but I know how to check. Same trick with the tiny piece of
solder. Put it where it won't do any damage if it melts. Tack it
down with some glue. Add flux. When it melts, you're hot enough.

Thanks, I gotta go find some flux...

Try blowing hot air at a puddle of flux to give you a clue what it
will do. Most use alcohol, which might catch fire.

Lenovo X31 hardware service manual:
http://download.lenovo.com/ibmdl/pub/pc/pccbbs/mobiles_pdf/39t6189.pdf

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Thu, 07 Jul 2011 23:28:15 -0700, Jeff Liebermann
wrote:

More on BGA flux use:
http://www.circuitnet.com/articles/article_80293.shtml
I hadn't thought of bulding a "dam" to keep the liquid flux in place,
but I'll give it a try next time.

Rework Fluxes:
http://www.zeph.com/zephlux.htm
http://www.coprise.com/Rework_Liquid_Flux_Page.html
http://www.aimsolder.com/Products/NoClean/NC280LowResidueLiquidReworkFlux.aspx
etc...

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Fri, 08 Jul 2011 07:49:05 -0700, mike wrote:

I find it annoying, although not unexpected, that the cost of a bottle
of flux is 8X the cost of the laptop. Sigh...

Huh? I paid $20 for my X31, but had to replace the HD, add RAM, and
upgrade the 2100b wireless to a 2200bg card. My guess is I have about
$100 into it. Ebay completed auctions show selling prices of $90 to
$180 so this is not going to make me rich.

Incidentally, there are motherboards for sale for about $45 which is
probably too high to use as a replacement or practice board.

If the price of flux is a problem, you could also make your own.
http://www.instructables.com/id/Make-your-own-Eco-friendly-soldering-flux/
I've actually done this and find that it somewhat works. The problem
was the sticky mess it created. For pine sap, I just went to the
local lumber yard and got permission to "sample" the sap oozing from
the cheap pine lumber. Very little sap is required. My guess is
about 5% solids in solution. I found that I had to add some HCL acid,
which made it "highly activated" flux and required cleaning after use.

I had better luck buying some rosin paste flux from the local hardware
store and dilluting it in denatured alcohol. It worked about the same
as the home made variety, but did not require filtering out the sap
solids, bugs, wood debris, dirt, etc.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

In article , mike
wrote:

I find it annoying, although not unexpected, that the cost of a bottle
of flux is 8X the cost of the laptop. Sigh...

As an electronic assembly house, I buy flux by the gallon. Find such an
outfit in your area and I'd bet they'd give you an ounce or two for
nothing. I would.

Jeff Liebermann wrote:
On Fri, 08 Jul 2011 07:49:05 -0700, mike wrote:

I find it annoying, although not unexpected, that the cost of a bottle
of flux is 8X the cost of the laptop. Sigh...

Huh? I paid $20 for my X31, but had to replace the HD, add RAM, and
upgrade the 2100b wireless to a 2200bg card. My guess is I have about
$100 into it. Ebay completed auctions show selling prices of $90 to
$180 so this is not going to make me rich.

Incidentally, there are motherboards for sale for about $45 which is
probably too high to use as a replacement or practice board.

I buy computers when they're a buck and I think I can fix 'em up.
I do it mostly for the challenge and to give me something to do.

Price of flux isn't a "problem", it's an annoyance.
Making your own is interesting. Wonder what my neighbor would say
if he caught me gnawing on his pine tree?
I happened by a parts store today, but they didn't have anything
I thought would work.
I'll just order some from ebay.

If the price of flux is a problem, you could also make your own.
http://www.instructables.com/id/Make-your-own-Eco-friendly-soldering-flux/
I've actually done this and find that it somewhat works. The problem
was the sticky mess it created. For pine sap, I just went to the
local lumber yard and got permission to "sample" the sap oozing from
the cheap pine lumber. Very little sap is required. My guess is
about 5% solids in solution. I found that I had to add some HCL acid,
which made it "highly activated" flux and required cleaning after use.

I had better luck buying some rosin paste flux from the local hardware
store and dilluting it in denatured alcohol. It worked about the same
as the home made variety, but did not require filtering out the sap
solids, bugs, wood debris, dirt, etc.

Jeff Liebermann wrote:
On Thu, 07 Jul 2011 09:21:16 -0700, mike wrote:

I bought a Thinkpad X31.

I have one on the bench as I write. Nice machine with a few design
defects. The plastic case is really flimsy and easy to crack along
the sides. I have yet to see an X30, X31, or X32 that does NOT have a
crack in the case somewhere. Plastic epoxy will fix it if you don't
care what the result looks like. Mine resembles Frankenstein:
http://802.11junk.com/jeffl/crud/Thinkpad-X31.jpg
X30 on the left, X31 on the right.

Fails video memory test and the image looks like
it's in 8-bit color mode.
Pushing hard on the motherboard fixes the image.
Lots of googling uncovers many people who've reflowed
the nVidea BGA chip by means varying from oven to hot
air to a blowtorch.

The X31 uses an ATI Radeo Mobile 7000 video chip.
http://www.thinkwiki.org/wiki/Category:X31

Before you blame the video chip, carefully inspect the video ribbon
cable. I've had failures with that cable that looked much like a
video chip problem. They're available on eBay for about $7.

The bad news about this one is that the video BGA
and a RAM BGA are sitting on a carrier that's looks
like it's made out of circuit board material and is also
BGA'd to the mother board.

Yep, that's the problem. Hit it with too much heat and it will melt
or burn (I forgot which). I monitor the heat with an IR thermometer.
Not hugely accurate because it's mostly measuring the temperature of
the hot air gun tip, but good enough. It really doesn't take much
heat or time to reflow the solder with the "skirt" of PCB material
around the BGA. Work fast. This should give you an idea of what to
expect:
http://www.youtube.com/watch?v=NJlgPbELL0E
(Drivel: Not the giant blob of Arctic Silver on top of the CPU to the
right. That's about 100 times too much. Oh well).

Incidentally, I just hot air reflowed and fixed 4 out of 6 HP
JetDirect J4169A cards, which have the same style BGA chip.

I'm not optimistic about getting the heat thru the chips
and the carrier to the motherboard without burning up something.

Rosin flux really helps. It largely prevents oxidation (cold solder
joint). It conducts the heat to odd places. It explodes if you get
it too hot.

In my limited experience, a real hot air desoldering station is a
must. You don't really need all the BGA nozzles as a small 3mm nozzle
is usually sufficient. I bought mine on eBay for about $80 with 4
nozzles. I suggest you practice on an old PCB before trying the real
thing. Getting the temperature right and how fast you move the
nozzle, require some practice.

The thing works well enough to surf the web or control stuff.
I'd hate to brick it. Certainly not worth a replacement motherboard
that has or will soon have the same problem.

It's worth saving.

Anybody got experience reflowing this dual-stack kind of thing?

Yep. My success rate was about 2 out of 5 motherboards with that
configuration. Can't win them all. You have a better chance than
most because you can sorta tell where to reflow.

A few hints:
1. Don't push down on the "skirt" while hot. That will cause the
solder balls to migrate across adjacent pads.
2. Use flux even if it makes a mess. I messy working computer is
better than a clean brick.
3. Build a heat shield out of aluminum foil. The hot air will melt
adjacent plastic quite easily.
4. Give it time to cool down.

Good luck.

Thanks for the inputs.
Flux arrived.
I practiced on a TiVo board. Had to get the air temp over 350C to get
enough heat to desolder a BGA.
I then took a shot at the laptop.
The intermediate board curled up on the corner when I heated it. I
feared I'd lost connection on that corner. Probably shoulda dropped the
temp cause of the thinner intermediate board.

When I tried to run it, I got no video. My heart sank...
I didn't think I needed to plug in the boards for wifi, firewire
and modem, but I took a shot and reassembled the whole thing.
IT WORKS.

Got any suggestions for a blower for a hot air gun.
This Leister is a 600W element and temperature regulator
at the end of a 10-foot air hose. They ran the power wire
down the center of the air hose and it provides a lot of back pressure.
It's designed to run off shop compressed air. My 3/4HP compressor
won't supply as much flow as I like. I haven't found anything that
can give me more volume against the back pressure. I even tried a 14"
blower designed for blow-up advertising devices. No luck. Back pressure
just stalls the impeller and the flow drops to nearly nothing.
Can't really justify a bigger air compressor and a new circuit to run it
for this.

Does it make sense to put fans in series to get better flow under
pressure? I gots lotsa fans.

Ideas?
Thanks,mike

On Tue, 12 Jul 2011 21:55:43 -0700, mike wrote:

I practiced on a TiVo board. Had to get the air temp over 350C to get
enough heat to desolder a BGA.

Argh. Too hot. It should about 220C for leaded and about 230C for
lead free BGA.
http://www.rayprasad.com/home/rp1/page_71/smt_-_lead-free_reflow_profile_development__part_2.html
This article also covers some other issues (mixing solder types).

I then took a shot at the laptop.
The intermediate board curled up on the corner when I heated it. I
feared I'd lost connection on that corner. Probably shoulda dropped the
temp cause of the thinner intermediate board.

Again, too hot and possibly not moving the hot air gun fast enough. At
that temperature, if you stay at one position for too long, you'll
burn the board. I've reflowed similar sandwiches on JetDirect boards,
and didn't have the edges curled.

When I tried to run it, I got no video. My heart sank...
I didn't think I needed to plug in the boards for wifi, firewire
and modem, but I took a shot and reassembled the whole thing.
IT WORKS.

Hold on. Have you tried flexing the board? You may have a mechanical
contact connection, but not a soldered connection. You might also
break some other BGA connections flexing the board, so you decide if
it's worthwhile.

Got any suggestions for a blower for a hot air gun.
This Leister is a 600W element and temperature regulator
at the end of a 10-foot air hose. They ran the power wire
down the center of the air hose and it provides a lot of back pressure.

The back pressure doesn't matter much. I use a little air as
possible. The only thing the air does is move the heat from the air
gun heater, to the PCB. Too much air results in premature cooling.
Too little air doesn't move enough heat or heats too slowly. If
there's some back pressure, and the reflected air remains fairly cool,
don't worry about it.

It's designed to run off shop compressed air.

Ummm... I hope it wasn't designed to run directly off a 150 psi
manifold. Got a URL for this thing? One of these?
http://www.leister.com/en/processheat-product.html?catalog=c70f3b1c-b3d6-4c64-88be-6d7b5cdc7502
I couldn't find anything that matches your description. Perhaps if
you supplied a model number?

My 3/4HP compressor
won't supply as much flow as I like.

Assuming a piston type compressor, 3/4HP should give you about 5 cubic
ft/min. That should be enough to peel parts off the top of the board
if you get too close. No way do you need that much air for
desoldering. You're not trying to blow hot solder balls all over the
board.

I haven't found anything that
can give me more volume against the back pressure. I even tried a 14"
blower designed for blow-up advertising devices. No luck. Back pressure
just stalls the impeller and the flow drops to nearly nothing.

What size nozzle are you using? That's not normal. Looking at the
various Leister models, it appears that they were not intended for use
with a small diameter nozzle.

Can't really justify a bigger air compressor and a new circuit to run it
for this.

Does it make sense to put fans in series to get better flow under
pressure? I gots lotsa fans.

Dunno. Offhand, I don't think so.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Jeff Liebermann wrote:
On Tue, 12 Jul 2011 21:55:43 -0700, mike wrote:

I practiced on a TiVo board. Had to get the air temp over 350C to get
enough heat to desolder a BGA.

Argh. Too hot. It should about 220C for leaded and about 230C for
lead free BGA.

Well, I asked you about this before.
I used an IR thermometer to monitor the chip temperature and stopped
heating when it got to 220C. I didn't time it, but it seemed like it took
a long time to get there with 350C air temperature.

When I practiced on the tivo, I tried air at 260C and could never get
the chip over 150C. 350C worked nicely, but it didn't have the
intermediate substrate.

The thing is still working. Good enough for me.

http://www.rayprasad.com/home/rp1/page_71/smt_-_lead-free_reflow_profile_development__part_2.html
This article also covers some other issues (mixing solder types).

I then took a shot at the laptop.
The intermediate board curled up on the corner when I heated it. I
feared I'd lost connection on that corner. Probably shoulda dropped the
temp cause of the thinner intermediate board.

Again, too hot and possibly not moving the hot air gun fast enough. At
that temperature, if you stay at one position for too long, you'll
burn the board. I've reflowed similar sandwiches on JetDirect boards,
and didn't have the edges curled.

When I tried to run it, I got no video. My heart sank...
I didn't think I needed to plug in the boards for wifi, firewire
and modem, but I took a shot and reassembled the whole thing.
IT WORKS.

Hold on. Have you tried flexing the board? You may have a mechanical
contact connection, but not a soldered connection. You might also
break some other BGA connections flexing the board, so you decide if
it's worthwhile.

Consensus seems to be that uncontrolled reflowing is a temporary solution
at best. Reballing and reworking with proper equipment is discussed
as the only reliable solution.
Remember, we're talking a dollar laptop. Not like it's the end of the world
if it quits. I hate that darn eraser mouse, so probably won't use it
anyway. I just like to fix stuff.
I can part it out for more than it's worth.

Got any suggestions for a blower for a hot air gun.
This Leister is a 600W element and temperature regulator
at the end of a 10-foot air hose. They ran the power wire
down the center of the air hose and it provides a lot of back pressure.

The back pressure doesn't matter much. I use a little air as
possible. The only thing the air does is move the heat from the air
gun heater, to the PCB. Too much air results in premature cooling.
Too little air doesn't move enough heat or heats too slowly. If
there's some back pressure, and the reflected air remains fairly cool,
don't worry about it.

It's designed to run off shop compressed air.

Ummm... I hope it wasn't designed to run directly off a 150 psi
manifold. Got a URL for this thing? One of these?
http://www.leister.com/en/processheat-product.html?catalog=c70f3b1c-b3d6-4c64-88be-6d7b5cdc7502
I couldn't find anything that matches your description. Perhaps if
you supplied a model number?

My 3/4HP compressor
won't supply as much flow as I like.

Assuming a piston type compressor, 3/4HP should give you about 5 cubic
ft/min. That should be enough to peel parts off the top of the board
if you get too close. No way do you need that much air for
desoldering. You're not trying to blow hot solder balls all over the
board.

I haven't found anything that
can give me more volume against the back pressure. I even tried a 14"
blower designed for blow-up advertising devices. No luck. Back pressure
just stalls the impeller and the flow drops to nearly nothing.

What size nozzle are you using? That's not normal. Looking at the
various Leister models, it appears that they were not intended for use
with a small diameter nozzle.

Labor 7 S
http://www.leister.com/en/plastic-welding-product.html
I don't have the tiny nozzle, opening is about half an inch across.
I built a 1/4" nozzle and experimented on the tivo board, but decided
it was worse than the full opening.

Rated 50-150 l/min at 500mbar static pressure.
I set the regulator at around 10psi, no idea how accurate the gauge is.
After about a minute, the tank pressure equalizes somewhere below 10psi
and that's all the flow I get.

It's designed for plastic welding with a small tip.

That 10 foot hose really does restrict air flow when you use the whole
half-inch
opening..


Can't really justify a bigger air compressor and a new circuit to run it
for this.

Does it make sense to put fans in series to get better flow under
pressure? I gots lotsa fans.

Dunno. Offhand, I don't think so.
When I dug up the spec, I found lotsa graphs of volume vs back pressure
for fans.
So, I've looked at this in detail back in 2005 and gave up.

On Tue, 12 Jul 2011 22:45:37 -0700, Jeff Liebermann wrote:

On Tue, 12 Jul 2011 21:55:43 -0700, mike wrote:

I practiced on a TiVo board. Had to get the air temp over 350C to get
enough heat to desolder a BGA.

Argh. Too hot. It should about 220C for leaded and about 230C for lead
free BGA.
http://www.rayprasad.com/home/rp1/page_71/smt_-_lead-
free_reflow_profile_development__part_2.html
This article also covers some other issues (mixing solder types).

I then took a shot at the laptop.
The intermediate board curled up on the corner when I heated it. I
feared I'd lost connection on that corner. Probably shoulda dropped the
temp cause of the thinner intermediate board.

Again, too hot and possibly not moving the hot air gun fast enough. At
that temperature, if you stay at one position for too long, you'll burn
the board. I've reflowed similar sandwiches on JetDirect boards, and
didn't have the edges curled.

When I tried to run it, I got no video. My heart sank... I didn't think
I needed to plug in the boards for wifi, firewire and modem, but I took
a shot and reassembled the whole thing. IT WORKS.

Hold on. Have you tried flexing the board? You may have a mechanical
contact connection, but not a soldered connection. You might also break
some other BGA connections flexing the board, so you decide if it's
worthwhile.

Got any suggestions for a blower for a hot air gun. This Leister is a
600W element and temperature regulator at the end of a 10-foot air hose.
They ran the power wire down the center of the air hose and it provides
a lot of back pressure.

The back pressure doesn't matter much. I use a little air as possible.
The only thing the air does is move the heat from the air gun heater, to
the PCB. Too much air results in premature cooling. Too little air
doesn't move enough heat or heats too slowly. If there's some back
pressure, and the reflected air remains fairly cool, don't worry about
it.

It's designed to run off shop compressed air.

Ummm... I hope it wasn't designed to run directly off a 150 psi
manifold. Got a URL for this thing? One of these?
http://www.leister.com/en/processhea...alog=c70f3b1c-
b3d6-4c64-88be-6d7b5cdc7502
I couldn't find anything that matches your description. Perhaps if you
supplied a model number?

My 3/4HP compressor
won't supply as much flow as I like.

Assuming a piston type compressor, 3/4HP should give you about 5 cubic
ft/min. That should be enough to peel parts off the top of the board if
you get too close. No way do you need that much air for desoldering.
You're not trying to blow hot solder balls all over the board.

I haven't found anything that
can give me more volume against the back pressure. I even tried a 14"
blower designed for blow-up advertising devices. No luck. Back
pressure just stalls the impeller and the flow drops to nearly nothing.

What size nozzle are you using? That's not normal. Looking at the
various Leister models, it appears that they were not intended for use
with a small diameter nozzle.

Can't really justify a bigger air compressor and a new circuit to run it
for this.

Does it make sense to put fans in series to get better flow under
pressure? I gots lotsa fans.

Dunno. Offhand, I don't think so.

I had an NVidia 8500 that the gpu was BGA. I cooked it in the oven at
450F for 5 minutes and it fixed the problem I was having, a system freeze
hard lock. Internet suggestions were a BGA problem and the reflow or
whatever the oven did fixed it. I thought solder melted higher than 450F
though.



--
Live Fast Die Young, Leave A Pretty Corpse

Meat Plow wrote in
:

On Tue, 12 Jul 2011 22:45:37 -0700, Jeff Liebermann wrote:
=20
On Tue, 12 Jul 2011 21:55:43 -0700, mike wrote:
=20
I practiced on a TiVo board. Had to get the air temp over 350C to get
enough heat to desolder a BGA.
=20
Argh. Too hot. It should about 220C for leaded and about 230C for le=
ad
free BGA.
http://www.rayprasad.com/home/rp1/page_71/smt_-_lead-
free_reflow_profile_development__part_2.html
This article also covers some other issues (mixing solder types).
=20
I then took a shot at the laptop.
The intermediate board curled up on the corner when I heated it. I
feared I'd lost connection on that corner. Probably shoulda dropped t=
he
temp cause of the thinner intermediate board.
=20
Again, too hot and possibly not moving the hot air gun fast enough. At
that temperature, if you stay at one position for too long, you'll bur=
n
the board. I've reflowed similar sandwiches on JetDirect boards, and
didn't have the edges curled.
=20
When I tried to run it, I got no video. My heart sank... I didn't thi=
nk
I needed to plug in the boards for wifi, firewire and modem, but I too=
k=20
a shot and reassembled the whole thing. IT WORKS.
=20
Hold on. Have you tried flexing the board? You may have a mechanical
contact connection, but not a soldered connection. You might also bre=
ak
some other BGA connections flexing the board, so you decide if it's
worthwhile.
=20
Got any suggestions for a blower for a hot air gun. This Leister is a
600W element and temperature regulator at the end of a 10-foot air hos=
e.
They ran the power wire down the center of the air hose and it provid=
es
a lot of back pressure.
=20
The back pressure doesn't matter much. I use a little air as possible=
=20
The only thing the air does is move the heat from the air gun heater, =
to
the PCB. Too much air results in premature cooling. Too little air
doesn't move enough heat or heats too slowly. If there's some back
pressure, and the reflected air remains fairly cool, don't worry about
it.
=20
It's designed to run off shop compressed air.
=20
Ummm... I hope it wasn't designed to run directly off a 150 psi
manifold. Got a URL for this thing? One of these?
http://www.leister.com/en/processhea...og=3Dc70f3b1c=
-
b3d6-4c64-88be-6d7b5cdc7502
I couldn't find anything that matches your description. Perhaps if yo=
u
supplied a model number?
=20
My 3/4HP compressor
won't supply as much flow as I like.
=20
Assuming a piston type compressor, 3/4HP should give you about 5 cubic
ft/min. That should be enough to peel parts off the top of the board =
if
you get too close. No way do you need that much air for desoldering.=20
You're not trying to blow hot solder balls all over the board.
=20
I haven't found anything that
can give me more volume against the back pressure. I even tried a 14"
blower designed for blow-up advertising devices. No luck. Back
pressure just stalls the impeller and the flow drops to nearly nothing=

On Tue, 12 Jul 2011 21:55:43 -0700, mike wrote:

Jeff Liebermann wrote:
On Thu, 07 Jul 2011 09:21:16 -0700, mike wrote:

I bought a Thinkpad X31.

I have one on the bench as I write. Nice machine with a few design
defects. The plastic case is really flimsy and easy to crack along
the sides. I have yet to see an X30, X31, or X32 that does NOT have a
crack in the case somewhere. Plastic epoxy will fix it if you don't
care what the result looks like. Mine resembles Frankenstein:
http://802.11junk.com/jeffl/crud/Thinkpad-X31.jpg
X30 on the left, X31 on the right.

Fails video memory test and the image looks like
it's in 8-bit color mode.
Pushing hard on the motherboard fixes the image.
Lots of googling uncovers many people who've reflowed
the nVidea BGA chip by means varying from oven to hot
air to a blowtorch.

The X31 uses an ATI Radeo Mobile 7000 video chip.
http://www.thinkwiki.org/wiki/Category:X31

Before you blame the video chip, carefully inspect the video ribbon
cable. I've had failures with that cable that looked much like a
video chip problem. They're available on eBay for about $7.

The bad news about this one is that the video BGA
and a RAM BGA are sitting on a carrier that's looks
like it's made out of circuit board material and is also
BGA'd to the mother board.

Yep, that's the problem. Hit it with too much heat and it will melt
or burn (I forgot which). I monitor the heat with an IR thermometer.
Not hugely accurate because it's mostly measuring the temperature of
the hot air gun tip, but good enough. It really doesn't take much
heat or time to reflow the solder with the "skirt" of PCB material
around the BGA. Work fast. This should give you an idea of what to
expect:
http://www.youtube.com/watch?v=NJlgPbELL0E
(Drivel: Not the giant blob of Arctic Silver on top of the CPU to the
right. That's about 100 times too much. Oh well).

Incidentally, I just hot air reflowed and fixed 4 out of 6 HP
JetDirect J4169A cards, which have the same style BGA chip.

I'm not optimistic about getting the heat thru the chips
and the carrier to the motherboard without burning up something.

Rosin flux really helps. It largely prevents oxidation (cold solder
joint). It conducts the heat to odd places. It explodes if you get
it too hot.

In my limited experience, a real hot air desoldering station is a
must. You don't really need all the BGA nozzles as a small 3mm nozzle
is usually sufficient. I bought mine on eBay for about $80 with 4
nozzles. I suggest you practice on an old PCB before trying the real
thing. Getting the temperature right and how fast you move the
nozzle, require some practice.

The thing works well enough to surf the web or control stuff.
I'd hate to brick it. Certainly not worth a replacement motherboard
that has or will soon have the same problem.

It's worth saving.

Anybody got experience reflowing this dual-stack kind of thing?

Yep. My success rate was about 2 out of 5 motherboards with that
configuration. Can't win them all. You have a better chance than
most because you can sorta tell where to reflow.

A few hints:
1. Don't push down on the "skirt" while hot. That will cause the
solder balls to migrate across adjacent pads.
2. Use flux even if it makes a mess. I messy working computer is
better than a clean brick.
3. Build a heat shield out of aluminum foil. The hot air will melt
adjacent plastic quite easily.
4. Give it time to cool down.

Good luck.

Thanks for the inputs.
Flux arrived.
I practiced on a TiVo board. Had to get the air temp over 350C to get
enough heat to desolder a BGA.
I then took a shot at the laptop.
The intermediate board curled up on the corner when I heated it. I
feared I'd lost connection on that corner. Probably shoulda dropped the
temp cause of the thinner intermediate board.

When I tried to run it, I got no video. My heart sank...
I didn't think I needed to plug in the boards for wifi, firewire
and modem, but I took a shot and reassembled the whole thing.
IT WORKS.

Cool.

Got any suggestions for a blower for a hot air gun.
This Leister is a 600W element and temperature regulator
at the end of a 10-foot air hose. They ran the power wire
down the center of the air hose and it provides a lot of back pressure.
It's designed to run off shop compressed air. My 3/4HP compressor
won't supply as much flow as I like. I haven't found anything that
can give me more volume against the back pressure. I even tried a 14"
blower designed for blow-up advertising devices. No luck. Back pressure
just stalls the impeller and the flow drops to nearly nothing.
Can't really justify a bigger air compressor and a new circuit to run it
for this.

Recently there was a thing about high volume low pressure air for paint
guns. I bet you could find something surplus or yard sale for cheap.

Does it make sense to put fans in series to get better flow under
pressure? I gots lotsa fans.

Ideas?
Thanks,mike