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BGA chip desoldering tips
1, BGA chip Removal
① good element protection, when removing BGA IC, pay attention to see if it affects the surrounding
elements, some of the phone's font, staging, CPU * very close. When desoldering, flooding the cotton
group can be placed on the adjacent IC. Many plastic amplifier, high temperature capability soft font
package is poor, difficult blow soldering temperature is too high, otherwise, it is easy to blow them bad.
② IC to be demolished in the above into the amount of flux, and try to bottom blown IC, so shocked pads
help chip under a homogeneous melt.
③ hot air gun to adjust the temperature and the wind, the general temperature 3-4 shift, wind 2-3 stalls,
wind mouth move around 3cm above the chip is heated until the chip under the tin completely melted,
tweezers pick up the entire chip. Note: To blow when heated IC IC around, do not blow IC middle, or easy
to blow the IC uplift, heating time not too long, otherwise the board to blow bubbles.
④ after the BGA chip removed, the chip pads and the machine board has more than tin, this time, in the
circuit board solder paste add a sufficient amount of aid, electric iron to remove excess solder board, and
may be appropriate on tin each fillet board are smooth and rounded, and then use the day that water
flux chips and machine will clean the board, except when the solder to be especially careful, otherwise it
will scrape the pad above masking or so that the pad off.
2, Plant tin
① ready to work. Solder on the surface of the IC can be cleaned with the right amount of help paste in
BGA IC surface, electric iron would be too large to remove the solder on the IC, and the IC into the wash
water that day, washed and check whether the IC pads bright, as part of the oxygen required plus electric
iron flux and solder, making it bright, so plant tin.
There are a variety of fixation methods ② BGA IC's, here are two practical and convenient method: paper
label fixed law: The IC-sik tin plate holes align with the IC tag stickers with plant tin plate firmly affixed,
IC Align , the tin plate plant by hand or forceps firmly fixed, and then on the other hand squeegee tin.
In the IC underneath napkin fixation: the IC underneath several layers of paper towels and then plant tin
plate hole is aligned with the IC pin placed, press firmly planted by hand or forceps tin plate, then scrape
③ on the solder paste. If the solder paste is too thin, it is easy to weld when blowing boiling lead into the
ball difficult, so the solder paste dry as possible, as long as not harden into blocks can be done, if it is too
thin, the available dry a little pressure on a napkin. Usually can pick some solder paste solder paste on the
inside cover, let it dry a little. Use a flat knife to pick the right amount of solder paste tin plate plant,
scraping down hard, while scraping edge pressure, the solder paste evenly fill holes in the tin plate plant.
④ transfer of small hot air gun to 2nd Wind, shaking wind mouth to slow uniform heating plant tin plate,
tin syrup slowly melted. When you see an individual planting holes in tin plate, tin ball has been generated,
indicating the temperature already in place, then it should raise a hot air gun, avoid temperature continues
to rise. High temperature solder paste will boil violently, leading to plant tin fail. Will be IC overheat serious
damage. If successful blow welding, we found some solder ball flood uneven, and even individual not on the
tin, to use the blade along the surface of the tin plate plant tin ball too much exposed part flattened, and
then whipped the ball over the knife tin small and lack the full foot hole in the solder paste, and then use a
hot air gun to blow once. If the flood is also uneven solder ball, then repeat the operation until the desired
state. Replanting amount must be clean tin plate plant Gan, dry. When taking sik tin plate, hot tweezers sharp
downward pressure on the IC at the four corners, so it is easy to remove much of it.
3, BGA chip mounting
① first BGA IC has a fillet that side coated with an appropriate amount of help paste, hot air gun temperature
to 2 files a wind blowing gently, so help paste evenly distributed in the surface of the IC. Thereby positioning
the IC is soldered tin beads to prepare. And then hot air gun temperature to 3 files, first heated board, blow
melt flux. Then plant good solder beads BGA IC by location Remove the front of the circuit board into the
same time, by hand or tweezers and gently move around the front and rear IC pressure, then you can feel the
exposure of both sides of the fillet. After the alignment, because advance IC foot painted a little help paste,
there is a certain viscosity, IC does not move. If the position side, and to re-locate.
② BGA IC good location, you can weld it. Sik tin ball and, as a hot air gun to adjust air flow and temperature
suitable, let the air nozzles aligned central location central IC and slowly heated. When you see the IC sank
around helps paste overflow, indicating the solder ball and solder circuit boards have been fused together.
Then you can gently shaking the hot air gun heating evenly full, due to surface tension. Automatically the
alignment between the BGA IC and PCB solder joints, attention during heating do not force BGA, otherwise
it would solder spill off the foot and can easily cause a short circuit. After welding is completed the board
with the day that water can be cleaned.
4, Removing with plastic BGA chip
Currently many brands of mobile phones BGA IC are filling plastic closures, when removing it more difficult to
glue tips for disassembly of such IC's. The following detailed description. For Motorola phones sealed plastic,
the market there are many brands of sol gel water can easily go through several experiments found that the
CPU V998 banana water immersion, to glue better, generally soak for 3-4 hours, sealed plastic on easily
removed. It should be noted that: V998 phone soaking must take before removing the font, font otherwise
be damaged. Because 998 is a soft font package, BGA, you can not use banana water, water that day, or sol
water immersion, these solvents BGA soft font package in plastic with strong resistance, will lead to gum
swelling font scrapped. Of course, if you do not sol water, it may also be demolished, Motorola sealant
temperature is low, easy to soften, and the CPU relatively high temperature, as long as attention method
can also be successfully demolished.
① first hot air gun wind speed and temperature to an appropriate position (typically 3-speed air flow, heat
4 files, can adjust depending on the brand of hot air gun)
② hot air at the top of the mobile CPU 5cm blow, after about half a minute, start with a small blade from the
CPU ground pin more direction, usually from the first leg, which is above the scratchpad starting pry * Note
the hot air does not stop .
③ CPU removed, and then is in addition to plastic, while blowing hot air gun, a force little by little, slowly and
carefully scrape with a knife until the pads clean.
④ Nokia primer initially issued a special injection molding, currently very good off the glue method.
5, Note that disassembly operation skills:
① fixed board, adjust the heat gun at a temperature between 270 ℃ -300 ℃, transfer large amount of wind,
so as not to blow shift RC components subject to the demolition of the IC sealant preheat about 20 seconds,
then move the air gun, and other board cools after preheating, the preheat three times, to be added every
time the oil is heavy flux preheat for oil to flow into the pad protection.
② the hot air gun temperature to between 350 ℃ -400 ℃, continue to IC heating, while heating gently press
tweezers IC, when you see the solder ball from the sealant extrusion, the less they can from one element
tweezers tip to the edge of the sealed plastic pick a few holes, so tin flow out, then still have to keep in mind
that put oil flux.
③ Detach IC, IC below when you see no smoke when tin, with a fine-tipped forceps with hooks placed under
the IC at risk tin, gently pick up can be removed.
④ clean up plastic closures, after removing most of the IC, plastic closures are left on the board, the first solder
points on the motherboard put flux, with iron on the tin sealant sucked, suck a few times more, can clearly
see the bottom of the pad light up, the main role is to completely let pads and sealed plastic separated.
Adjust air gun temperature between 270 ℃ -300 ℃, the sealant is heated on the motherboard, this time the
sealant is basically out of the pad, spotted a safe place with tweezers and solder joints between the pick,
pick efforts To control the good, if attempts just right, you can remove a pick a blockbuster. For clear sealant
on the IC is not the same slow, first IC wash, then in the back of the IC double-sided adhesive glue, express it
fixed desoldering stage, air gun temperature is still adjusted to between 270 ℃ -300 ℃, put flux, heat sealed
plastic tweezers can be a challenge to remove.
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