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question about reflow- it it ever a long term solution?

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#66731

question about reflow- it it ever a long term solution? | 3 July, 2012

Hi I did a reflow on an HP laptop a while back- it was a DV6000 series. The original problem was the internet stopped working- turns out the south bridge chipset was causing the issue (its a very common issue I found out after searching online). Some people said they did a reflow on the south bridge chipset and that fixed it, but lots of people warned that it will not last. They said the only true solution was to reball with lead solder. So I gave the reflow a try- it worked but they were right it only lasted about a month.

So I recently had a customer bring me a mac book pro (2008 model) and the problem was soon as you hit the power button it would turn on and then go right off after 2 seconds. I took the machine apart and saw that the vents were fully clogged with dust. It obviously overheated. I purchased a replacment board on ebay and they said it was a factory refurb board. So I got it and I could tell it was not a factory refurb, I called the guy and he told me it was pulled from a working unit and he reflowed it himself, he said he does it with all the boards he sells, and then sends them to Coremac (a mac repair center) for inspection and they give him a pass certificut. So that gave me an idea- I tried to reflow the chips on the broken board myself. I reflowed the following three chips: 1. GPU,2. CPU, and 3. Northbridge chipsets. I put the board back in after the reflow, and the mac book pro laptop powers up!

My question is will this problem come up again on the mac book pro in a month or so, like the wifi problem came back on the HP laptop? If the problem is likley to return, wouldnt the guy who reflows them all be doing more harm then good? Or was that issue of it only being a short term fix apply to just the south bridge chipset on the HP laptop?

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#66740

question about reflow- it it ever a long term solution? | 3 July, 2012

Just so that we both on the same page: * When you "reflow the chips on the broken board," what do you actually do? How do you do it? What kind of controls do you use? * When someone "did a reflow on the south bridge chipset," what do they do?

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#66742

question about reflow- it it ever a long term solution? | 3 July, 2012

Hi, when they did the reflow with the south bridge chipset they took a heat gun and went arround the chip in circles. This is what I did with the broken apple motherboard. I covered the board in tinfoil and cut out the squares arround the gpu, cpu and north bridge chipset and took my hot air gun and went in circles over the chip (one at a time). I let it cool down for an hour then I took the tin foil off and tested it and it worked. I just dont know if it is a long term solution or if it will soon fail again. I know with the south bridge chipset it failed after a month. I was wondering why it would fail so soon?

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#66743

question about reflow- it it ever a long term solution? | 3 July, 2012

Reflowing a BGA can be a reliable and long term fix, but it has to be done correclty, and using a heat gun and going in circles around the part is definitly not the right way to do it.

To do it correctly you would flux under the bga, use a rework station with a proper profile, and clean under the component properly after you're done with it (I would use a water soluble flux and make sure you clean very well under it, but if you don't feel that you'll be able to clean under it well enough then use a no clean flux).

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#66749

question about reflow- it it ever a long term solution? | 4 July, 2012

Phil is correct in his description of proper rework technique.

Possible explanations of the reason for popping of your BGA are: * Thermal cycling of components cause them to flex on a different point in the cycle that the board possibly resulting in cracking of solder balls * Board was not laid-up properly during fabrication causing it to warp and when it is fixtured into the assembly, it may be putting stress on solder connections * Component is defective causing it to overheat

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