HELP!!!!Water Damag...
 
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HELP!!!!Water Damaged iPhone

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(@ebwahlberg)
Eminent Member
Joined: 17 years ago
Posts: 34
 

I would be careful with blow dryers and anything that blow air on the device. I the device was in an environment that has contaminants you could blow those contaminants under chips and short out leads under the body of the chip.
Eric


   
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(@trewmte)
Noble Member
Joined: 19 years ago
Posts: 1877
 

In the videos identified in Mobile Phone Chip Off [ http//trewmte.blogspot.co.uk/2011/02/mobile-phone-chip-off.html ] they shows heat being applied to the board and chip. The temperature of the heat is significantly higher than an ordinary blow dryer.


   
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jaclaz
(@jaclaz)
Illustrious Member
Joined: 18 years ago
Posts: 5133
 

In the videos identified in Mobile Phone Chip Off [ http//trewmte.blogspot.co.uk/2011/02/mobile-phone-chip-off.html ] they shows heat being applied to the board and chip. The temperature of the heat is significantly higher than an ordinary blow dryer.

Sure it's the same kind of temperature needed for smd or BGA reballing/reflowing/reworking, you have to reach the fusion point of the soldering, typically something between 200 and 210°, but often higher.
Compare with
http//www.emulation.com/pdf/102003BGA_Reballing_Instruction_Manual.pdf
(includes a simple temperature reflow profile)

But this heat is generally appied only to a limited area of the board (hence the use of pre-heating the whole board to 150÷180° to avoid cracks due to differential temperatures).
The thermal profile used is anyway a RSS one
http//en.wikipedia.org/wiki/Thermal_profile
http//en.wikipedia.org/wiki/FileRSS_Components_of_a_Profile1.svg

But common sense must be used, some components (microphone, loudspeaker, *any* insulated wire) cannot bear those high temperatures.
Actual "proper" re-balling or de-soldering tools/stations use an infrared heater to just raise the temperature of the chip to the fusion point (or hot air stations with aptly sized nozzles).
What I personally do (poor-man's way) is to make masks in cardboard covered with tin foil to protect the surroundings of the chip when using hot-air.

@EBWahlberg
The thingy is WASHED accurately before drying it, exactly for those reasons.

jaclaz


   
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jhup
 jhup
(@jhup)
Noble Member
Joined: 16 years ago
Posts: 1442
 

[…]
What I personally do (poor-man's way) is to make masks in cardboard covered with tin foil to protect the surroundings of the chip when using hot-air.
[…]

I like that. PCB, cardboard and tin (aluminum) foil cutouts?


   
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jhup
 jhup
(@jhup)
Noble Member
Joined: 16 years ago
Posts: 1442
 

Talking about cleaning, what type of polymer or similar encasing have any of you ran across?

I have seen some polymers, but have not specifically identified them.

I have heard of polyurethane, epoxy, phenoxy, and silicone used. I heard of 3M's Novec electronic grade coatings. I have also perused "Handbook of Polymer Coatings for Electronics - Chemistry, Technology and Applications" by Licari.

How would alcohol react with such coatings?


   
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jaclaz
(@jaclaz)
Illustrious Member
Joined: 18 years ago
Posts: 5133
 

I like that. PCB, cardboard and tin (aluminum) foil cutouts?

Yep, I take a piece of cardboard from a box, cut a hole in it slightly larger than the chip, cover the whole card board with aluminum foil (the one for cooking/kitchen, I have a slightly thicker "professional" type but don't think that it would make any difference, the idea is that the aluminum reflects heat, while cardboard is an excellent thermal insulating material).

Then I put between the board and the cardboard "peeking" in a corner of the hole a thermal sensor (el-cheapo), the ones which come with most multimeters, example
http//www.multimeterwarehouse.com/MAS838f.htm
and apply the hot air, using a common hot air pistol, mine is "deluxe" as it has some three fan speeds and 8 thermal settings, but almost any would do, it's just a matter of finding the right combination of temperature/air flow/distance of the gun nozzle.

jaclaz


   
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