reflowing BGA with a hot air gun?

I have a laptop that is acting really weird. It's an older ASUS, probably ten or twelve years old. It was plugged in, closed, sitting on a table. It worked fine a few days before the problems started. The display keeps shaking. The machine takes forever to boot up. And then acts weird. But if I push down hard on the lower left side of the machine it works fine. As long as the pressure is kept up and in just the right area. I spoke to my son about this problem because he knows more about this kind of thing than I do. He said it sounded like a video card problem that he and some of his computer whiz friends have run into. Apparently the video processor can get too hot and the BGA under it can start to debond. He has a hot air rework tool and he said I might be able to reflow the chip. Is this something that a rank amateur can likely do? Eric

Reply to
etpm
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Since the machine is on its way out anyway, why not give it a whirl? Do your backups first, of course.

Laptops use the circuit board as a stressed structural element, so they sometimes crack when mistreated, e.g. when picked up horizontally by a front corner. I had one go like that, and the symptoms were similar to yours. Now when I need to one-hand a laptop I pick it up near the hinge instead.

Cheers

Phil Hobbs

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Reply to
Phil Hobbs

I'd try mechanically doing what your fingers were doing, with silicone rubber sleeving stretched/twisted appropriately, wooden wedges (ex-sprung clothes pegs) etc . Don't overdo the pressure, just enough to emulate the finger action.

Reply to
N_Cook

We all have to start learning somewhere. My domain is LearnByDestroying.com which should offer a clue as to how I start learning. If you've never worked on a laptop before, your problem will not be the hot air reflow, but rather the disassembly and reassembly. Spare screws, mangled flat ribbon connectors, and broken plastic are common. I suggest you use a digital camera to record the disassembly to help with the reassembly. You might be lucky and NOT need to remove the motherboard from the case, but that's not typical. Before you blow dry your machine, you might look inside, around the lower left corner, and see if any connectors have come loose. Also, find an air compressor and blow out the dust, especially around the fan.

There are YouTube videos showing how to use a hot air gun to reflow a BGA. Make sure you build a heat shield out of aluminum foil to prevent melting nearby plastic parts. Practice on scrap PCB's before attempting to fix the unspecified model Asus laptop. It's quite difficult to tell if the low temperature solder balls have reflowed. I'm undecided if liquid flux does anything useful.

Good luck.

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Jeff Liebermann     jeffl@cruzio.com 
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Reply to
Jeff Liebermann

Thanks for the advice Jeff. And the link. I did take this machine apart once about 5 years ago to replace the hard drive. That all went fine. Your "unspecified model ASUS" remark made me laugh because when I was typing out the original message I realized I didn't have the model number on hand and knew at the time that I really should have included it with my post. I always seem to get caught. Thanks Again, Eric

Reply to
etpm

I have a laptop that is acting really weird. It's an older ASUS, probably ten or twelve years old. It was plugged in, closed, sitting on a table. It worked fine a few days before the problems started. The display keeps shaking. The machine takes forever to boot up. And then acts weird. But if I push down hard on the lower left side of the machine it works fine. As long as the pressure is kept up and in just the right area. I spoke to my son about this problem because he knows more about this kind of thing than I do. He said it sounded like a video card problem that he and some of his computer whiz friends have run into. Apparently the video processor can get too hot and the BGA under it can start to debond. He has a hot air rework tool and he said I might be able to reflow the chip. Is this something that a rank amateur can likely do? Eric

Reply to
Gareth Magennis

It's worth a go if the laptop is scrap otherwise.

Chances of success are extremely slim though.

The success stories you see on Youtube are either fake, or the tiny percentage of these repairs that lasted long enough to make the video.

Gareth.

I have a laptop that is acting really weird. It's an older ASUS, probably ten or twelve years old. It was plugged in, closed, sitting on a table. It worked fine a few days before the problems started. The display keeps shaking. The machine takes forever to boot up. And then acts weird. But if I push down hard on the lower left side of the machine it works fine. As long as the pressure is kept up and in just the right area. I spoke to my son about this problem because he knows more about this kind of thing than I do. He said it sounded like a video card problem that he and some of his computer whiz friends have run into. Apparently the video processor can get too hot and the BGA under it can start to debond. He has a hot air rework tool and he said I might be able to reflow the chip. Is this something that a rank amateur can likely do? Eric

Reply to
Gareth Magennis

You can give it a try.

Here is one opinion on the reflowing.

formatting link

Probably nothing to gain, but you won't loose much either.

One that old is probablly due for a change unless you need it like I need some old dos computes to program up some old equipment.

Reply to
Ralph Mowery

I experimented with it on a laptop video chip.

I built a box with a square hole in the top. Put in air baffles to point airflow at the hole. Stuck a variable paint stripper in the side of the box.

Cleaned the area under the chip with repeated applications of simple green, alcohol, water and lots of air. Dried it overnight in a hot box at about 120F. Used liquid flux designed for reflow repair under the chip.

Put thermocouples on the board and spaced it above the hole.

Adjusted the paint stripper to ramp the temperature of the bottom of the board to just below the melting point of solder. Aimed a temperature controlled air flow designed to desolder chips at the unmasked area around the chip on the topside. Heated the top of the chip to above the melting temperature of solder. Used topside thermocouples, but today would probably try a thermal imager. Fixed the intermittent video problem.

Elated with my success, I tried another. I had been using paper towels for insulation under the aluminum foil topside mask. Got careless and set the paper towels on fire. Putting out the fire jostled the board and some chips fell off the backside. EPIC fail!

over the next year... Third try fixed another laptop.

Fourth try didn't help that laptop. Fifth try didn't help that laptop.

Laptops got so cheap at garage sales that reflowing one wasn't worth trying.

YMMV

Reply to
mike

I experimented with it on a laptop video chip.

I built a box with a square hole in the top. Put in air baffles to point airflow at the hole. Stuck a variable paint stripper in the side of the box.

Cleaned the area under the chip with repeated applications of simple green, alcohol, water and lots of air. Dried it overnight in a hot box at about 120F. Used liquid flux designed for reflow repair under the chip.

Put thermocouples on the board and spaced it above the hole.

Adjusted the paint stripper to ramp the temperature of the bottom of the board to just below the melting point of solder. Aimed a temperature controlled air flow designed to desolder chips at the unmasked area around the chip on the topside. Heated the top of the chip to above the melting temperature of solder. Used topside thermocouples, but today would probably try a thermal imager. Fixed the intermittent video problem.

Elated with my success, I tried another. I had been using paper towels for insulation under the aluminum foil topside mask. Got careless and set the paper towels on fire. Putting out the fire jostled the board and some chips fell off the backside. EPIC fail!

over the next year... Third try fixed another laptop.

Fourth try didn't help that laptop. Fifth try didn't help that laptop.

Laptops got so cheap at garage sales that reflowing one wasn't worth trying.

****************************

Took me a few attempts on old Mac laptops to realise you can't do this job with a paint stripper.

Gareth.

Reply to
Gareth Magennis

That's a start. However, to reflow the BGA chips on the motherboard, you'll need to remove the motherboard from the plastic case. I take photos as dive into the machine. Seems to impress (or panic) the customer. For example:

That's a catch phrase that I use quite often. An amazing number of people ask questions without supplying much in the way of identifying the device they're trying to repair. If they're stuck on something, they will describe what they've done, but not what problem they're trying to solve. After many years, I suspect the problem is chronic. Here's my magic formula for getting mostly sane answers on forums and newsgroups:

  1. What problem are you trying to solve? No history or product reviews, just the problem.
  2. What have you done so far and where are you stuck? What happened?
  3. What do you have to work with? Maker, model, version, numbers.

This won't work for a laptop, but I've been successfully reflowing HP Jetdirect cards in a toaster oven. So far, 18 working boards out of

20: Also about 15 assorted HP printer PC boards and a few game boards. Protecting plastic parts, that are easily melted, is the main problem. Aluminum foil shields do not work, so I have to remove the parts. Most everything else that can survive PCB soldering, can survive the toaster oven reflow. Unfortunately, there are too many plastic parts on a laptop motherboard, so it's not going to work.
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Jeff Liebermann     jeffl@cruzio.com 
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Reply to
Jeff Liebermann

Jeff:

Just did the 350F bake for 8 min for an HP P2015dn printer formatter PCB a few weeks ago. Gas oven. Level. Since there was a report of melting an Et hernet jack, I used 1/2 thick felt to protect it. I also removed the stick ers. I did thermocouple the oven and did the overnight "do not disturb" th ing after turning the oven off and opening the door. Worked great!

Reply to
Ron D.

I had to LOL at that. I have an HP Envy dv7 laptop that I don't use anymore even though it's by far my most modern computer. Being an invalid with chronic lower back pain vacuuming is one of the most crippling household chores so it doesn't get done as often as I'd like.

The Envy has such a high air through-put that it doesn't take long to injest enough dust to start causing problems. Also it's no IBM ThinkPad when it comes to dis/assembly and has quite a few plastic tabs which won't handle many cycles before breaking.

So I still use my ThinkPad T60 / 2GB RAM Win XP while my envy with i7 / full HD display / 32GB SSD-accelerated 1TB HDD / 16GB RAM sits in a drawer. I used it for a week or two but could tell that even in tat time and trying to be careful of dust the airflow was reducing... This T60 pushes far less air through and is simple to pull down once a year to clean the fan and fins.

I got the dv7 from a neighbour who offered it to me in return for data recovery from it. (It got so hot that it wouldn't run for long, the RAM was 'cooked' and causing HDD corruption every time they tried to read from it and it randomly shut down. I installed the new 16GB after I was happy there was a good chance it would work again.) Maybe I'll get to use it when I finally have to go into assisted living - if people still use laptops then.

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Reply to
~misfit~

Photo of the above heat pipe radiator AFTER I blew compressed air into the area from the outside. The only way to get the crud out is to tear it apart.

Also, this one way it could be easily cleaned: The bottom cover comes off exposing the entire heat pipe assembly, which is then easily cleaned. Too bad Dell (or Foxcom) designed it into a crappy machine (Inspiron 1525) with miserable BGA soldering.

More later. Gotta run.

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Jeff Liebermann     jeffl@cruzio.com 
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Reply to
Jeff Liebermann

The HP envy that I have likewise must be stripped down to where the top and bottom shells are apart to clean the fan. This is what the fins looked like when I finally got there:

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I was fully intending to cut a hole in the bottom case (and make a hinged door with tape) so I could access the fan / fins for the frequent cleaning it will require but the fan lifts out *upwards* and is half under the keyboard.

(In that picture the heatpipe that you can see is the one from the GPU that's already been past a smaller set of fins [out-of-shot to the right]. Behind that are the two heatpies that come directly from the 3GHz quad core i7 CPUs heat collector.)

I've not seen setups like that on recent machines. IMO manufacturers are using 'heatsink clog' combined with difficulty of disassembly / reassembly (with fragile plastic clips and ribbon cables) as a form of built-in obsolescence. After all CPUs and SSDs aren't becoming obsolete / underpowered as quickly as they once did...

Cheers,

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Shaun. 

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Reply to
~misfit~

get a piece of foam and make an external intake filter

much easier to clean an external filter

m
Reply to
makolber

I thought of that but the air enters in multiple places so that ancilliary hardware gets airflow. Short of sitting it on a full-sized pad of fine-pored open-cell foam that wraps up the front and sides (and supporting that above the desk on a grating-type thing) it's not really an option.

Cheers,

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Shaun. 

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Reply to
~misfit~

Won't work. The basic problem is that the typical laptop fan air intake is on the bottom of the laptop, where it can play vacuum cleaner and suck all the dust, hair, and food debris from the table and into the fan. The fan then uses centrifugal force to launch all this crud into the heat pipe fins, where they get stuck. Plugging the intake with a filter might prevent clogging the downstream fins, but just moves the problem to the intake filter, which can also become clogged. Granted, an intake filter is easier to clean, but from experience, nobody ever cleans the filters until they are totally clogged.

A better solution would be to find a more protected air intake location, such as on the top of the machine. That could be done with a plenum or duct, but with todays ultra-thin laptops, there's no room. Worse, most of the top is obstructed by the keyboard. There are a few laptops that have the air intake on the side, and exhaust out the back. Those don't clog as easily, but do tend to have larger cases.

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Jeff Liebermann     jeffl@cruzio.com 
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Jeff Liebermann

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