Best BGA reflow practices

[ratdude747]

Many months ago I reflowed a HP DV6800 with a BGA chipset fault... the reflow was initially successful, but a month later the originally bad joints failed once again.

I used a blackjack reflow station (my college's) with a thermocouple at the chip die and plenty of rosin paste flux. Somewhere on the forum is the temp profile I used.

What I'd like to figure out is what exactly I did wrong... I was once told that I needed much higher end equipment (a reflow tunnel) to fix it, which is out of the question since I don't have that kind of tooling to play with.

So, can a laptop chipset be reflowed in that way, or do I need fancier equipment? Or any BGA reflow tips I missed?

[momaka]

Re: Best BGA reflow practices

Did the chip have epoxy glue on the side? If yes, and if you didn't remove it, that usually yields crappy reflow results. Also, did you check the chip temps when the laptop was working? If the chip runs too hot, it will always fail, no matter how good of a reflow job you did.

Moreover, reflow is rarely a solution to the problem. It's just a temporary fix, and the time it works can vary between just a few weeks to a few years (if done very well). But best hope is to lift the chip and do a reball with leaded solder. There are many fairly cheap reball kits on eBay.

[Th3_uN1Qu3]

Re: Best BGA reflow practices

It isn't the joints between the chip and the board in your case. It's the joints between the die and the chip. All nVidia chips made between 2007 and 2009 are faulty, this is a known issue. It's gonna crap out again no matter what you do to it, unless you swap it for a new chip made in 2009 or later. I have about a dozen of those dv6000 boards left if you want to try your hand at some more...

Reflow can be a long-term solution if you do it right (chip is heated until the solder is fully liquid) and the chip is good to begin with. If the laptop no longer works because it's been dropped, then a reflow will likely fix it. If it failed due to prolonged overheating, it's either reball or chip swap. Chip swap is a must for any nvidia chip made <2009. Anything else is a waste of time.

[theOracle]

Re: Best BGA reflow practices

how can someone in Romania have perfect English AND know what they are talking about? - what the %$#@???

I thought they just had beautiful women and gymnasts and vampires there?

[Th3_uN1Qu3]

Re: Best BGA reflow practices

To get those beautiful women, you need either looks, brains or money... I'm not bad-looking but i'm broke 90% of the time, so i gotta compensate with the smarts.

I just finished churning out a dv6000 myself. Out of the pile of scrap boards there was one that has been used very lightly, and never worked on, the chipsets looked factory. It is one of the two boards that had the 8400M GS 128MB, the other being in very poor shape. This board had a coffee spill and didn't power on at all.

I determined the board actually worked, but only with a charged battery. It did not detect the power adapter at all. Well, after half a day, i figured it out. Two tiny resistors, a trace, and a SOT-23 diode were damaged by corrosion. Replaced the parts and the board is now working great. I already had a complete casing and screen, pulled a hard drive out of nowhere, and we have a laptop.

[theOracle]

Re: Best BGA reflow practices

you must have spent a lot of time in USA, no one living in Romania all of their life can speak American English this perfectly, not buying it! - you're busted! - lol

[Th3_uN1Qu3]

Re: Best BGA reflow practices

Never been to the US actually. When i was 5 my dad went to the UK and brought me a lot of learning books and tapes, and until i was 9 he spent a lot of time teaching me English. That's how.

[LLLlllou]

Re: Best BGA reflow practices

Never been to the US actually. When i was 5 my dad went to the UK and brought me a lot of learning books and tapes, and until i was 9 he spent a lot of time teaching me English. That's how.

He did a damn fine job, I always assumed you where there just for the strippers.

[Th3_uN1Qu3]

Re: Best BGA reflow practices

I always assumed you where there just for the strippers.

Haha... i'm here for more than strippers.

[Behemot]

Re: Best BGA reflow practices

I have a guy for reflows/reballs saying not all the chips are really that bad and that reflowing them helped him quite many times, so where's the true in this?

Also, how much really jsut reflowing helps? The problem root - the bad solder - remains. Do you also do reballs?

[Th3_uN1Qu3]

Re: Best BGA reflow practices

Also, how much really jsut reflowing helps? The problem root - the bad solder - remains. Do you also do reballs?

The problem with the 2006-2009 nvidias isn't the solder, it's always the chips themselves. I know someone who put put 3 Sony Vaio with failed 8400M GS in a x-ray machine and the soldering was perfect on all three (!!!). Two had the old chips reballed, the third had a new chip installed. First two failed again after 3 and 4 months respectively, 3rd one never failed again and it's been more than an year.

With other chips, it can be just the solder, just the chip, or both... It depends. A reball is generally required if the pads have oxidized - however, there's really no way of finding that out without lifting the chip, so many people reball "by default" when they encounter a no video issue.

Yes i also do reballs, but i have only done a few.

[Behemot]

Re: Best BGA reflow practices

Just that this guy whome I sometimes send stuff to reball says he did reflow/reball and all of it worked fine after that. I was surprised as well as I know it was said before those chips has substrate problems thus are defective themselfs.

[infringer]

Re: Best BGA reflow practices

substrate issues can be caused from excess heat or even reflowing ... In many cases it is in fact tin whiskers that cause the issue initially which causes the excess heat that I am aware of ... If you follow the correct reflow temperature curves it does make a difference on your success of reflowing. Proof for me was a PS3 that I owned that had the YLOD I actually found a temperature curve graph from a reflow oven after I fixed the PS3 at first and 3months later same thing then I reflowed the chip again using the reflow ovens temperature curve as a guideline but raising the temperature a bit being that I was in open air with a hot air station and bingo still working after a couple of years so for me I will say that there is a science to getting a proper reflow same thing with the HP's I would like to add though that 20xx it don't matter most all of hp/compaq laptops ATI and Nvidia chipsets have issues with overheating which is why I am so glad that AMD hased moved to the APU with integrated graphics built in to the processor the problem is the design of the socket IMHO I firmly believe somethings should not be packaged in BGA form when in confined spaces they are fine for desktops but gaming stations and laptops not a good idea from my investigations this package has a high rate of failure for any intense power hungry device in a confined area it is just not a good idea period... ROHS could be to blame or UL or whatever with the lead free solder but why bother with something that is known to be a complete utter failure and cost your company way more in repairs than what it is saving by not adding the socket why not make a more solid product and protect your companies name a bit better I just don't get it really I don't....

Reflow does work but there is a science behind it and the proper ends for your hot air station that is temperature regulated helps along with a digital thermostat and a timer and a steady hand or rig to hold your air gun at a steady distance while monitoring it all helps as well. Any one can go ahead and attempt a reflow but the problem I find is just most people heat it up until solder melts on top of the chip or until they feel it is good enough and this is wrong you need a ramping up of heat and a fairly brisk cool down.

Basically you need to start off warming below the top temp for a couple of minutes then you hold it at peak temp for a minute let it cool down a little slowly at first and then rapidly cool down this is typically how most all temp graphs look for reflow ovens for all different things.

[Th3_uN1Qu3]

Re: Best BGA reflow practices

Reflow does work but there is a science behind it and the proper ends for your hot air station that is temperature regulated helps along with a digital thermostat and a timer and a steady hand or rig to hold your air gun at a steady distance while monitoring it all helps as well. Any one can go ahead and attempt a reflow but the problem I find is just most people heat it up until solder melts on top of the chip or until they feel it is good enough and this is wrong you need a ramping up of heat and a fairly brisk cool down.

Basically you need to start off warming below the top temp for a couple of minutes then you hold it at peak temp for a minute let it cool down a little slowly at first and then rapidly cool down this is typically how most all temp graphs look for reflow ovens for all different things.

Of course there's a science. I have built a stand for my hot air station, have proper BGA nozzles, and also have a preheater underneath. That way my hands only need to keep steady on the knobs.

For laptops (lead free) i've settled on this:

1. Bring the board up to 150C using the preheater only, this should take 3-5 minutes.
2. Turn on top heat, turn on timer, bring chip to 217C over 1 minute.
3. Hold for 30 seconds at 217C.
4. In another 30 seconds, bring the chip up to 240-250C. Chip should not be over 230C more than 5-10 seconds.
5. Turn off all heat and allow to cool.

If i reball (with 63/37 Sn/Pb), the profile stays the same, just the temps change a little. Hold at 190 and peak no higher than 230.

I haven't fried a single chip since i've settled for this profile. 1 minute at peak temp is way, way too long and i've learned this the hard way. Even just 230C for 1 minute will burn the chip.

All temperatures are measured with the thermocouple directly on top of the die, and this is valid for hot air only.