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MOBILE PHONE SERVICING- BGA CHIP REMOVAL GUIDE

BGA chip removal and welding
1. Guide
With the rapid global development of mobile communication technology, many handset makers compete to launch new compact and powerful mobile phones. In these new phones, the widespread adoption of advanced BGAIC (Balld arrays ball grid array package), which has spread the technology can significantly reduce the volume of mobile phone, enhancements, reduced power consumption, lower production costs. But, like all things beneficial to have disadvantages, BGA package IC is easy to fall caused by Weld, and to the maintenance work led to great difficulties.
BGA packaged chips are used precision optical instrument patch installed, error is 0.01mm, while the actual maintenance work, most of the repairs were not like the SMT equipment, even with all welding hot air and feel installation, little chance of success.

To properly replace a BGA chips, except with skilled use of hot air gun, BGA solder tool set but also must master certain skills and the correct method of dismantling welding. These methods and techniques to practice in the operation are described below
2. Operating
(1) BGA IC positioning
Before the demolition BGAIC must figure out the exact location of BGA-IC to facilitate welding to install. Some phone lines in the board pre-printed with BGA-IC positioning frame, the general orientation of this IC is not a problem of welding. Here, the main circuit board is not positioning box describes the case of IC positioning method.
Drawing a line positioning method. Before removing the pen or needles IC BGA-IC of the week week draw the line, remember the direction, make signs, prepare for the re-welding. Advantage of this method is accurate and easy strokes of the line defects is easily washed, draw lines with a needle if the efforts to master the bad circuit board easily hurt.
Stickers positioning method. Remove the BGA-IC before the four sides along the IC circuit board with a label affixed in the well, the edge of the paper with the edge of BGA-IC alignment, clamp the compacted cement. In this way, remove the IC, the circuit board on the left box label affixed good positioning. Reload IC, as long as several labels in front of the IC back into the space you can, pay attention to choose good quality adhesive label paper to paste stronger, so that can not be easily blown off during the reflow process. If you find a layer of thin paper label can not find the words feel, can be several layers of overlapping labels into a thick, cut with scissors to the edge of flat, paste it into the circuit board, it will be loaded back to feel a little better when IC .
Visual method. Demolition of BGA-IC before the IC first erected, then you can also see the IC and the circuit board pins, welding first compare the horizontal position, and then compare the vertical position welding. Remember the edge of the vertical and horizontal direction of IC and the circuit board on which lines and which components overlap or parallel, and then the results by visual reference to locate the IC.
(2) BGA-IC demolition
Recognize the BGA chip chip should be placed on top after the amount of flux, we can avoid dry winds, can help chip solder joints under uniform melt, will not harm adjacent components.
Remove hot air gun with a big head in front of the first set, the general transferred to the heat switch 3-4 stalls, stall speed the switch to 2-3 in chips about 2.5cm above the Department for spiral blow, until the bottom of the tin beads complete chip melting, tweezers gently hold up the entire chip.
Need to explain two things: First, the demolition BGAIC, we should observe whether the impact on surrounding components, such as the Motorola L2000 mobile phone, the demolition of character, it must remove the SIM card seat connector, otherwise, it is easy to blowing bad. Second, Motorola T2688, Samsung A188, Ericsson T28 of the amplifier and many soft-font package, BGA-IC temperature capabilities of these poor, hard blowing welding temperature is too high (should be controlled at 200 degrees below), otherwise, it is easy blow them bad.
BGA chip removed, the chip pad and the phone has more than tin plate, this time, in sufficient quantities in the circuit board with solder paste aids, electric soldering iron to remove the extra board, and can be properly on the tin so that each solder circuit board feet smooth rounded (not smoking tin solder suction line will be flat). And then use the thinner the chip and the board of the flux machine washed. Absorption should be particularly careful when tin, otherwise it will scratch pad and the pad off the top of the masking.
(3) seed tin operation
Do your homework. To remove the IC, IC is not recommended to remove the surface of the solder, as long as not too large, and the plant without affecting the steel with tin can, if large solder somewhere can help BGAIC surface with an appropriate amount of solder paste , electric soldering iron to solder IC's too big to remove (note best not to use suction to the suction line of tin, because the IC package for those soft fonts such as Motorola, if the suction line to suction, then tin will cause IC The welding pin indent the soft brown skin, posing difficulties on the tin), and then washed with water that day.
BGA-IC fixed. Alignment of the IC after planting holes in tin plate (note that if that side of the hole using a small planting hole big side of the tin plate, large hole side should be close to IC), with a label sticker to IC and tin plate plant Posts prison, IC aligned, put the tin plate plant by hand or forceps firmly fixed, and then paste on the other hand scraping tin.
On the tin paste. If the paste is too thin tin, blowing welding boiling lead into a ball on the easy difficulty, so the more dry solder paste as possible, as long as not doing hard into blocks can be made. If too thin, the pressure on the napkin can be a bit dry. Usually can pick a number of tin on tin pulp slurry to stamp a bottle and let it air dry a bit. Select appropriate level the sword with tin solder paste to the plant board, scraping down hard, scraping edge pressure side to solder paste evenly fill in the holes in the tin plate plant.
Note that special "care" about the four corners of the hole IC. Solder paste on the key when the tin plate plant to be pressed, if not pressed to make tin plate plant and the gap between IC, then the gap in the tin solder paste will affect the generation.
Welding blow into the ball. To remove hot air gun nozzle, the air volume to the minimum, will set the temperature to 330 - 340 degrees, which is 3-4 stalls. Huang nozzle tin plate plant slowly toward uniform heating, so slowly melting tin paste. When the individual saw the planting hole in the tin-plate solder has been generated, indicating the temperature has been in place, this time should raise the hot air gun nozzle, to avoid the temperature continues to rise. High temperature solder paste will make intense boiling, resulting in failure of plant tin; serious damage will make IC overheating.
If you blow into the ball weld, we found some uneven solder ball size, and even not planting on individual legs of tin, may be the first plant with a cutter along the surface of tin plate will be too large exposed part of the solder ball to level, then scraper the solder ball is too small and lack of foot hole in the tin covered with paste, and then again with hot air gun blowing once. If the solder ball size is also uneven, it can repeat the operation until the ideal state. Replanting must be set tin plate clean, dry.
(4) BGA-IC installation
First BGA-IC are coated with solder side of the foot solder paste amount of help, with a wind blowing hot air gun gently to help paste evenly distributed in the IC surface preparation for welding. Then plant a good solder ball BGA-IC position by position before the demolition into the circuit board, while the IC before and after hand or forceps and gently pressing move around, then you can feel both sides of the solder pin contacts . Because both sides are welded foot round, so if targeting a move back and forth, IC has a "summit of the hill climb" feeling, align it, because pre-painted in the IC's feet a little help solder paste, there is a certain viscosity, IC Wood moves. If the IC on the side, and to re-locate.
Be a good place BGA-IC, you can weld a. And the solder ball when planting, as the hot air gun nozzle to remove, adjust to the proper air flow and temperature, so that the central nozzle aligned IC's central location, slow heat. IC shocked when you see the solder paste and help around the overflow, indicating the solder and circuit board solder joints have been fused. Then you can gently rock full of hot air gun to heat evenly, due to surface tension, BGA-IC and the circuit board between the solder joints will be automatically aligned position, pay attention not to force the heated press and hold the BGA-IC, Otherwise, solder will spill, off the feet and are very vulnerable to short-circuit. Upon completion of welding the plate with the day that water can be cleaned.
Soldering BGA-IC in the wind, the temperature often affect the rubber seal next to some of IC, which often do not start such failure. Removed with a cell phone to cover the shielding cover is not effective, because your eyes shielded cover to resist, but can not stop the hot air. At this point, next to the IC in the top drop on a few drops of water will absorb heat evaporation is a lot of heat, as long as the water quit, next to the IC's temperature is maintained at safe temperature of 100 degrees, so as not to trouble the . Of course, you can also use heat tape to paste up the surrounding components or integrated circuits.

Third, treatment of common problems
1. No corresponding tin plate plant vegetation tin BGA-IC method
For some models of BGA-IC, do without this type of plant tin plate, may first try to hand the existing plants have tin plate and piece of BGA-IC pin spacing as welding, can be set get on, even if tin plate plant some feet away empty it does not matter, as long as can BGAIC feet planted in each solder ball can be, for example, the CPU and the Flash GD90 available 998CPU and power IC's tin plate plant to apply .
2. Glial fixed BGAIC the cannibalize method
Many phone BGA-IC fixation methods used gum, this gum is difficult to deal with, very difficult to remove BGAIC, here are several common methods for the demolition of reference.
(1) Motorola mobile phones with bottom glue BGA-IC, with the current number of brands on the market is basically the glue can be up to par. The experiment found that banana water (paint thinner) soaking is better, just soak 3 to 4 hours you can remove the BGA-IC.
(2) Some mobile phone's BGA-IC is the end of glue 502 glue (such as the Nokia 8810 mobile phone), the use of blowing hot air welding gun, you can smell the smell of 502, well soaked with acetone.
(3) Some Nokia mobile phones for the end of a special plastic injection molding, incomparably better dissolve the current method of demolition should pay attention to the demolition skills, underfill and solder due to thermal expansion is not the same degree and often do not melt plastic solder the first inflated. Therefore, the blowing welding, hot air gun thermostat should not be too high, while in blowing welding, tweezers, press a little hard, you will find BGA-IC solder beads surrounded by a spill, indicating the weight of an effective, almost blown when you can translation look BGA-IC, if peace movement, shows that the bottom had been melting, then the BGA-IC exposing them relatively safe.
It must be explained: the Motorola V998 phone, soaked to remove the former must take the character, otherwise the character will be damaged. Because the V998's character is a soft package BGA, can not use banana oil, thinners or sol blisters. Because these solvents on the soft seal in plastic BGA font strong corrosive plastic expansion will lead to Fonts scrapped.
3. PCB stripping approach
For example, in replacement of V998 of the CPU, remove the CPU are likely to find the green circuit board solder layer stripping phenomenon, reinstall CPU-current fault occurs after the mobile phone, hand-to-hot CPU have signs. CPU solder layer must be destroyed following reasons, re-solder CPU short circuit occurred.
This phenomenon desoldering V998's CPU, it is common, the main reason is lack of time soaking solvent, there is no bubble through. Also remove the CPU in time, to side with the hot wind, while the surface of tweezers in the CPU to fully tap the various parts, so that the prevention of PCB circuit board solder stripping and broken legs, a very good prevention.
In the event of a "stripping" phenomenon, can go to the production of printed circuit board manufacturers to find a dedicated solder (commonly known as "green oil") smear in the "stripping" of the place, let it dry slightly, with a soldering iron to solder circuit board little can be welded on to open a new CPU. In addition, we bought in the market of the CPU on the original package solder balls are relatively large and easy to cause a short circuit, and we do use tin plate plants are smaller solder balls. The original adoption of the solder balls can be removed, then re-plant tin filled to the circuit board, it is not prone to short circuit.
4. Solder joints broken foot treatment
Many mobile phones, as wrestling or demolition do not pay attention, is likely to result BGA-IC circuit board solder joints under the broken legs. At this point, circuit boards should first be put under the microscope, to determine which is the empty legs, which is indeed broken. If you only see a smooth bottom of the "fossa", next to no line extension, which is empty legs can not do care; if broken legs next to the bottom line extension or side-track, the burr, is not illustrate the point empty legs, according to these methods remediation.
(1) connection method
For the next to extend the breakpoint line, you can use a knife to gently scratch the line next to that, spend enough tin enameled (enameled wire should not be too thin or too thick, such as too small, then reload BGA-IC enameled easy to move when bit) one end of the welding line next to the breakpoint, one end of the extension to the breakpoint location;
For the sandwich to the circuit board to the breakpoint, you can gently under the microscope with a needle to the breakpoint in the digging, dug the roots of highlights after the break, carefully solder a short wire with out. All after the break with a good line, carefully place the BGA IC soldering.
(2) fly line method
The connection method for the difficulties with breakpoints, first of all you can access information and more normal way to determine the board is where access to the circuit board, and then use a very fine enameled wire soldered to the BGA-IC corresponding solder ball. Welding method is to have solder ball BGA-IC side facing up, with a hot air gun blowing heat, it will insert one end of magnet wire solder balls, and the line after the line leads to the gap along the solder ball, turn to the opposite IC Heat the sticker with a fixed and ready welding. Carefully weld, IC cooling, and then leads the line of welding to pre-position look good.
(3) seed ball
For there is no line that extends around the breakpoints, we gently under the microscope with a needle digging, to see bright spots, the use of needle dig a little when we used tin tin plant pulp on top, with a small fine, blowing hot air gun into a ball, if the solder does not fall with a small brush, brush lightly, or control data measurements confirmed a good solder joint has indeed received. Note that the board slightly larger solder balls to do that, if done too little in the welding on the BGA-IC, the board will be IC solder balls on the solder ball to attract in the past and come to naught.
5. Board approach to blister
Sometimes demolition BGA-IC, because the temperature of hot air gun control is not good, resulting in BGA-IC circuit board under the blistering uplift because of overheating. Generally speaking, most will not cause foaming and overheating disconnection, maintenance as long as cleverly weld the above BGA-IC, mobile phones will be able to function properly. Maintenance can use the following three measures:
(1) flatten the circuit board. Hot air gun will be transferred to the appropriate temperature and light wind blowing circuit boards, the back edge blowing Gently press edges to clamp the line into part of the Long board, make it as smooth 1:00.
(2) IC plant on top of a large solder ball. No matter how circuit boards, lines are not completely flat, we need to plant into a larger IC, solder balls easy to adapt to the rugged circuit board welding, we can take two pieces of the same plant and with the use of tin plate Tape cement, and then a piece of "thickening" of the plant to plant tin tin plate. Good tin plant will find difficult to remove the IC, this time not to rush to remove, can be coated in tin plate plant paste a little help, will tin plate plant overhead, IC down, gently blowing with hot air gun, IC solder will melt and the easy separation of tin plate plant.
(3) In order to prevent the solder on the BGA-IC circuit board when the original blister Office has also uplifted by the high temperature, we can install the IC when the circuit board in the opposite mat a sponge absorbing enough water, so too can avoid the circuit board temperature high.

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