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Old 04-06-2011, 07:55 AM   #1
bigbeark
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Default Hot Air Gun vs Oven Reflow

I read with interest Unique's oven reflow methodology and noted the need to remove the electrolytic caps before "baking".

Can you avoid this step using the Heat Gun method? How do you tell when the chipset reflow is completed?

I've got a stack of boards using Nvidia 7050 chipset, some don't power on at all, some spin the fans but no POST.

Thanks, Barry
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Old 04-06-2011, 08:16 AM   #2
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Default Re: Hot Air Gun vs Oven Reflow

The answer is tricky to answer, i would say it depends on how it looks on the board. To some extent you can protect other components with tinfoil or similar things to lead the heat away from anything you're not working on. That is not a 100% solution for everything though, and its not without risks.

So if the board you're working on is not anything important i would say go for it, however if its something expensive or something you're repairing for a third party maybe not risk it.

How you can tell when its done, well when its reached the right temperature for the solder used. That can be a tricky one to know and measure.
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Old 04-06-2011, 08:57 AM   #3
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Default Re: Hot Air Gun vs Oven Reflow

If you go on YouTube, you can watch various videos of how people "reflow" their boards. Some folks use the oven method, others a heat gun and some a small butane torch. Unfortnately, you only hear from the people where these methods worked, but not so much from those where it failed. So the success rate may be skewed a bit. Even if these methods work and you install a heatsink method to draw the heat away from the chip, this "fix" still might wind up being short term. Like digge says, if these boards are for yourself, then go for it. If they're being repaired for customers or a third party, then it's not worth the risk.
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Old 04-06-2011, 09:12 AM   #4
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Default Re: Hot Air Gun vs Oven Reflow

You have more chances to screw up with the hot air gun rather than using the oven. This is a 100% honest comment from someone who has used both methods.

As for it being temporary... Reballed boards fail too if they aren't done properly. Factory made boards fail too if they aren't done properly (that's why reflows and reballs even exist, duh). Yet, i know people who've had laptops with 8400GS for over 4 years, and they still work just fine to this day without ever being serviced. If adequate thermal transfer is achieved, the board will become obsolete way before it fails.

Flux + oven is the best way to go if you don't want to shell out the big dough for an infrared station.
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Old 04-06-2011, 10:29 AM   #5
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Default Re: Hot Air Gun vs Oven Reflow

i've been thinking about one of these

http://www.frys.com/product/6389401?...H:MAIN_RSLT_PG

or better

http://www.frys.com/product/6389431?...H:MAIN_RSLT_PG

i've seen youtube videos with similar ones, they take the chip off, clean, reball with good stuff and put it back on with this simple equipment. but it bet it takes some skill without a magnifier
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Old 04-06-2011, 10:38 AM   #6
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Default Re: Hot Air Gun vs Oven Reflow

A scrap motherboard with a BGA chip can be used to get an idea of how long it takes to get the solder liquid with a heat gun. The chips won't just come loose because the solder's surface tension holds them, they have to be pushed.
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Old 04-06-2011, 09:36 PM   #7
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Default Re: Hot Air Gun vs Oven Reflow

Both. A hot air gun won't take a large BGA chip off a room temperature board without destroying something. I can only get them off in a timely fashion if I set the temperature to 450*C where the chips will be damaged. Down around 310*C all day isn't long enough.

Proper BGA equipment has a board heater along with an infrared chip heater. Better equipment has multiple board heaters because to do it right you must heat the entire board to a temperature safe for all components, heat the area being worked on to a higher temperature, then heat the chip to melt temperature. Then there's that pesky temperature profile.

A hand held heat gun is great for a lot of stuff but against big BGA chips it will break the board, the chip, or you. I cheat on a lot of small chips but I'm leaving BGA alone until I have at least an Aoyue 732 and a reball station.
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Old 04-06-2011, 10:27 PM   #8
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Default Re: Hot Air Gun vs Oven Reflow

do you have 1 1/2 grand to shell out?

this is why I think those smaller aoyue stations might do the trick. theres a lot of youtube videos about reballing with those

some don't even use stencils or balls. one used a find-point solder tip and filled in each hole with solder on the chip and the board. sure it took a long damn time, but it worked great
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Old 04-07-2011, 04:10 AM   #9
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Default Re: Hot Air Gun vs Oven Reflow

Quote:
Originally Posted by severach View Post
I cheat on a lot of small chips but I'm leaving BGA alone until I have at least an Aoyue 732 and a reball station.
That Aoyue 732 looks pretty nice... but do you trust the quality of it that much to actually buy one?
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Old 04-07-2011, 04:58 PM   #10
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Default Re: Hot Air Gun vs Oven Reflow

Quote:
BGA chip can be used to get an idea of how long it takes to get the solder liquid with a heat gun.
And that ain't very long for me Im using a 2 speed hobby gun that I have built a nozzle on. Same sorta gun that is used to heat shrink plastic covering on model planes. Knocks off them little bios chips in about a minute or less.
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Old 04-07-2011, 05:19 PM   #11
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Default Re: Hot Air Gun vs Oven Reflow

But BIOS chips aren't BGA...
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Old 04-07-2011, 06:42 PM   #12
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Default Re: Hot Air Gun vs Oven Reflow

actually being sma makes them easier to knock off cause the leads are exposed to the hot air
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Old 04-07-2011, 06:47 PM   #13
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Default Re: Hot Air Gun vs Oven Reflow

BGA I won't go there. There be madness and frustration.
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Old 04-10-2011, 01:49 AM   #14
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Default Re: Hot Air Gun vs Oven Reflow

yes, but how many computer technicians can do this kind of work? general nerdy techs will look up to you as a god, mwahahah

not only that, but you can make moneah
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Old 05-09-2011, 10:11 PM   #15
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Default Re: Hot Air Gun vs Oven Reflow

I tried using an old flat electric griddle once to preheat the board and a heatgun to melt the solder and pull the chip with good luck. Unfortunately when the chip failed it toasted some traces under it so I can't say if it would work good for reflowing or replacement, etc. YMMV
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