[coreboot] smd work

Peter Stuge peter at stuge.se
Fri Dec 29 13:45:25 CET 2017


Alberto Bursi wrote:
> Basically you blob solder on all pins to have the thing heat up all
> the pins together so you can then remove the chip.

I would not recommend this method to a beginner reworking a consumer PCB.

For an SO chip I would recommend buying a pair of fine tip pliers,
e.g. Piergiacomi TR 20 or TR 25, and cutting all SO chip pins flush
with the chip body. The chip body is then loose and can simply be
removed, leaving only individual soldered pins.

Pins can then be removed one at a time by simply touching the the
solder pad with the soldering iron.

Get a soldering iron with a fine flat tip (something like 2mm x 1mm is good)
and ideally no less than 30 W, in order to ease rework of the ground pin.


> Solder wick is magic stuff. Very recommended for any fine soldering job.

It takes getting use to. Successfully using wick requires more heat,
ie. a more powerful soldering station.


Do use desoldering wick to clean solder off the pads after removing the
pins one by one, but don't overdo it. Only rework each pad ONCE!

Commerical PCBs can't be relied upon to tolerate very much heat
beyond the original assembly - so rework should be swift.

Once the wick has pulled most solder off the pad move on to the next pad,
repeating for all pads.


When soldering the new chip in, heat one pad and apply some solder
onto the pad. Keep heating the pad and then place the chip with one
pin into the flowed solder, with all pins aligned to the pads. Then
solder the pin opposite to the first one for mechanical stability.
Then solder the remaining pins.


Use solder with a flux core.


//Peter



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