Released on September 19, 2014, this 4.7" screen iPhone is the smaller version of the iPhone 6 Plus.

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Soldering Big Power IC U1202 (Thermal Curve)

Hi, i do motherboard repair about half of year but i still have big problem with solder PMIC. Always when i try solder PMIC i always become short, phone do not want boot and PMIC or processor goes really hot. So my question is:

Need i special thermal curve or thermal profile for solder PMIC? I have professional BGA repair machine with top and bottom heater but i am not able solder PMIC perfectly.

How to solder big power ic?

Sorry for my bad english, i am not from states :)

Best regards

Tomas

Answered! View the answer I have this problem too

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Hi Tomas. The vast majority of the iPhone micro-solderers replace the PMIC by hand with a hot air station, not with a BGA Reballing machine. Micro-soldering on iPhone logic boards is as much an art as it is a science and most of the folks you see regularly publishing on Youtube (Jessa, Jason, Louis, etc...) do it by hand.

The big difference between repairing a motherboard (i.e. laptop or computer) and a logic board (iPhone, Smartphone and tablet) is the thinness and component density. iDevice logic board are very thin, have ~10 layers of traces and have high component density. No doubt the large-scale GPU's on motherboards represent their own set of challenges but using a reballing machine for replacing a PMIC is like using a jackhammer to repair cabinetry.

What I suspect is happening is that excessive amounts of heat are bleeding over to adjacent components and IC's and you are probably creating shorts underneath them. By the time the PMIC is at the proper temperature, you probably have half of the logic board at the right melting temperature as well.

Also, as some IC's have lots of underfill, when they get heated the pressure builds up underneath and eventually the solder balls explode out from the sides. That's a sure sign you shorted out that component.

So you can keep experimenting with heat curves and you may just find something that works consistently well but the best bet is to develop the "right touch" and then you will become a micro-soldering "artisan" :>).

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Comments:

I use always 330-350 C for solde rand desplder components. So which temp do you recommend for soldering PMIC?

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I set my Hakko 810 hot air station to ~380C (360-380 depending on variables).

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And do you have not problem solder PMU? Do you protect CPU anf other components on board with capton tape when do you solder PMU?

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If you can do a clean pull, that is remove it without any lifted or damaged pads, then re-soldering it is relatively straightforward. I say relatively because every time you apply massive amounts of heat to a logic board, there are always risks.

I usually cover adjacent IC's with a penny, nickel or dollar coin to sink some heat. If there are any FPC connectors then I will cover those with Kapton tape. This is where the "artisanry" comes in...you have to practice a lot to get the right amount of heat to the IC and pcb but not more than you need.

I also clean the pads with a concave tip to remove as much lead-free solder as possible and then apply some leaded solder with the same tip but with the well filled up. Braiding is always risky even though it does clean the pads better...it has a tendency to lift pads.

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