M
Mark Rejhon
Guest
Hi,
I did a lot of electronics in the high school days (even getting 99%
in Electronics class) but that was many years ago.
I've got a Blackberry 7280 (a cellphone with very good email) which
got exposed to water by being dropped in a puddle. The battery was
removed immediately (avoid short circuits) and the Blackberry was
disassembled to dry out. Reassembled after something like 24 hours.
I now need advice on circuit board cleaning.
The good news is the Blackberry pretty much works fine with one
exception (its computer is fine; I can connect to the Blackberry phone
over USB; and the screen is working fine). But the thumb keyboard is
malfunctioning. It's as if two or three keys are stuck down, or a
matrix wire is shorted. Definitely, at least the "S" key is stuck
down because I know it tries to execute a (S)earch upon turning on. I
can override it by holding down a key while booting up the blackberry
by putting the battery in (any of the leftmost 5 keys of the first
row, or the letter 'a' in the second row). That allows me to give
limited one-keypress control of the Blackberry, but then the stuck
key(s) take over.
I disassembled the Blackberry again and scrubbed as much residue I
could out of the contacts. I removed the keyboard down to the bare
contacts, used pencil eraser, used isopropyl-dipped Q-tips, used
water, cleaned the keyboard contacts. But I booted up the Blackberry
without the keyboard buttons (just the circuit board contacts where
the keys were) and the "S" key is still stuck down, so it is obviously
that the short must be somewhere much further upstream. (Just to be
sure the behaviour was the same as having the keyboard buttons on it,
I covered the "Q" contacts with a piece of metal, and was able to
simulate the "Q" keypress if I shorted it while applying power to the
Blackberry).
I spent over an hour of time using isopropyl-dipped Q-tips scrubbing
any residue I could see, including some that I saw between
surfacemount components.
Reassembled. Still no dice. Something still seems shorted somewhere.
Looks like I have to try something more drastic, such as immersing the
circuit board completely inside a circuit board cleaning liquid, in an
attempt to dissolve any residue that might be hiding underneath the
pesky BGA chips or between ultra-high-density chip pins. There gotta
be residue hiding underneath an inaccessible area.
It's a 2003-era circuit board design, highly integrated with lots of
surfacemount components and several tiny BGA-like packaged chips, as
well as others (not sure what kind of packaging, MQFP, or whatever --
I'm very rusty on my terms)
I need to now attempt to dissolve residue that may be hiding in places
such as between BGA contacts underneath chips. Will brief 1 minute
immersion & washing in 90-97% isopropyl liquid be safe? Distilled
water? Or what liquid would be the best? Or too dangerous? I can
remove the LCD screen and put the LCD screen aside.
At this moment, I'm willing to be almost sort of kamikaze on this
circuit board since my last resort is to fork out for a Blackberry
replacement ($400). So I need to do some reasonably inexpensive
last-ditch attempt, such as washing the circuit board in a recommended
liquid. Is 90-97% isopropyl fine? Or what inexpensive chemical? At
what percentage? Keep in mind, I can only use chemicals safe enough
to use in a condo and meets Canada regulations (I'll check).
Thanks,
Mark Rejhon
I did a lot of electronics in the high school days (even getting 99%
in Electronics class) but that was many years ago.
I've got a Blackberry 7280 (a cellphone with very good email) which
got exposed to water by being dropped in a puddle. The battery was
removed immediately (avoid short circuits) and the Blackberry was
disassembled to dry out. Reassembled after something like 24 hours.
I now need advice on circuit board cleaning.
The good news is the Blackberry pretty much works fine with one
exception (its computer is fine; I can connect to the Blackberry phone
over USB; and the screen is working fine). But the thumb keyboard is
malfunctioning. It's as if two or three keys are stuck down, or a
matrix wire is shorted. Definitely, at least the "S" key is stuck
down because I know it tries to execute a (S)earch upon turning on. I
can override it by holding down a key while booting up the blackberry
by putting the battery in (any of the leftmost 5 keys of the first
row, or the letter 'a' in the second row). That allows me to give
limited one-keypress control of the Blackberry, but then the stuck
key(s) take over.
I disassembled the Blackberry again and scrubbed as much residue I
could out of the contacts. I removed the keyboard down to the bare
contacts, used pencil eraser, used isopropyl-dipped Q-tips, used
water, cleaned the keyboard contacts. But I booted up the Blackberry
without the keyboard buttons (just the circuit board contacts where
the keys were) and the "S" key is still stuck down, so it is obviously
that the short must be somewhere much further upstream. (Just to be
sure the behaviour was the same as having the keyboard buttons on it,
I covered the "Q" contacts with a piece of metal, and was able to
simulate the "Q" keypress if I shorted it while applying power to the
Blackberry).
I spent over an hour of time using isopropyl-dipped Q-tips scrubbing
any residue I could see, including some that I saw between
surfacemount components.
Reassembled. Still no dice. Something still seems shorted somewhere.
Looks like I have to try something more drastic, such as immersing the
circuit board completely inside a circuit board cleaning liquid, in an
attempt to dissolve any residue that might be hiding underneath the
pesky BGA chips or between ultra-high-density chip pins. There gotta
be residue hiding underneath an inaccessible area.
It's a 2003-era circuit board design, highly integrated with lots of
surfacemount components and several tiny BGA-like packaged chips, as
well as others (not sure what kind of packaging, MQFP, or whatever --
I'm very rusty on my terms)
I need to now attempt to dissolve residue that may be hiding in places
such as between BGA contacts underneath chips. Will brief 1 minute
immersion & washing in 90-97% isopropyl liquid be safe? Distilled
water? Or what liquid would be the best? Or too dangerous? I can
remove the LCD screen and put the LCD screen aside.
At this moment, I'm willing to be almost sort of kamikaze on this
circuit board since my last resort is to fork out for a Blackberry
replacement ($400). So I need to do some reasonably inexpensive
last-ditch attempt, such as washing the circuit board in a recommended
liquid. Is 90-97% isopropyl fine? Or what inexpensive chemical? At
what percentage? Keep in mind, I can only use chemicals safe enough
to use in a condo and meets Canada regulations (I'll check).
Thanks,
Mark Rejhon
480)460-2350 | |