Handling skills BGA IC desoldering and frequently asked questions
The method is suitable for the motherboard north and south bridge
 #1 Choose a plant tin tools
Commercially available plant tin plate can be divided into two categories: one is to do all the models in a large piece of tin plate plant; the other is a board for each IC, two planting methods without the use of tin plate the same. Siamese tin plate plant to use after the solder paste is printed on the IC, put the tin plate plant screeching, and then use a heat gun blown The advantage of this method is simple and fast into the ball, is a disadvantage. 1.Solder paste can not be too thin. 2. For some not easy on the tin IC such as flash or cpu go after soft rubber seal, blow the ball when the ball will Luangun tin is extremely difficult on the tin. 3. Not the size of the solder ball and vacancies point after a secondary treatment plant tin. 4. Even when you can not plant tin tin plate plant, together with a hot air gun to blow, otherwise the plant will be deformed uplift tin plate, tin cause can not be planted. Small tin plate plant use is fixed to the plant after the IC tin plate below, after scraping together a good solder paste blow even board, as the ball cool before removing the IC. The advantage is that when the wind blows hot tin plate plant almost no distortion, if missing after a foot planted tin or tin ball too big too small phenomenon can be secondary treatment, especially for novices to use.
Recommend the use of bottled imports solder paste, mostly 0.5-1 kg bottle. Fine particles uniform, slightly dry as excellent. Not recommended to buy the kind of syringe filled with solder paste. In emergency use, the solder paste can also be made, the lower the melting point of ordinary solder wire is available with a hot air gun melted block, after the grinding wheel with a fine powdered form, then with the amount of flux stir well before use.
3.Squeegee tool
This is no special requirements, as long as you can easily use. We are using a set of six GOOT kind of flux tool knife flat mouth. Some friends even with a flat screwdriver toothpick can be, as long as he pulled on the line.
4.Heat Gun
The best use of a thermostat function CNC hot air gun to remove the wind blowing directly solder nozzle.
5.Flux
The shape is similar to the requirements of the butter-like paste. Flux is very effective, not corrosive for IC and PCB, having a boiling point only slightly higher than the melting point of the solder, the solder melts in the welding soon began to boil absorbs heat of vaporization, make the IC and PCB temperature was kept at this temperature.
6.Cleaner
With the best water that day, the day that water rosin flux paste has an excellent solubility, poor solubility can not use alcohol.
#2 Tin plant operation
1.Preparations
In the IC surface with the right amount of help paste, electric soldering iron to remove the residual solder on the IC (note the use of suction-line is best not to smoke, because for those software packages such as Motorola IC font, if the suction-line go suck it, will cause the IC fillet indented soft brown leather inside, causing difficulties on the tin), and then the wash water in days.
2.Fixed IC
There are many plant tin tool suite, all with a base for fixing the IC made of aluminum alloy. This seat is actually very easy to use: First, the operation is very troublesome to use jigs, if fixed is not strong blow solder tin plate plant a move would fall short; the second is to blow when the IC on the base, to even chunks aluminum base are blowing hot, IC solder paste melted before they agree on the ball. In fact, the fixed method is very simple, as long as the IC-sik tin plate alignment hole (Note that if you are using a kind of side hole big hole while planting a small tin plate, it should be towards the side of the big hole IC), with a negative price stickers prison can, tin plate plant is not afraid to move, like how to blow on how to blow. For the operation of skilled maintenance personnel, can even do not have stickers, after IC aligned by hand or forceps firmly fixed after planting tin plate, and then on the other hand squeegee blowing tin solder balling.
3.The solder paste
If the solder paste is too thin, it is easy to weld when blown into a ball of boiling lead solder paste and therefore more difficult to dry as possible, as long as not doing hair can be hard to block. If too thin, can suck a little pressure on a napkin. Our usual practice is: pick some solder paste solder paste on the inside lid of the bottle and let it dry naturally. Use a flat knife to pick the right amount of solder paste plant tin plate, scraping down hard, while scraping edge pressure, the solder paste evenly fill in holes in the tin plate plant. Note that special “care” about the IC corners holes. Solder paste on when the key is to be pressed tin plate plant, if not pressed to make the existence of a gap between the plant and the IC tin plate, then the gap will affect the solder paste solder ball formation.
4.Blowing solder balling
The hot air gun nozzle removed, the air volume to maximum, shaking wind Tsui slowly toward uniform heating plant tin plate, tin syrup slowly melted. When the individual saw the planting hole in the tin plate, tin ball has been generated, indicating that the temperature is already in place, then the wind should raise the heat gun nozzle, to avoid the temperature continues to rise. High temperature solder paste will boil violently, causing the plant tin failure; severe overheating will damage the IC.
5.Resizing
If we blow into the solder balls, solder ball size found some uneven, not even individual foot planted on the tin, to use the knife along the surface of the tin plate plant will be too exposed portion of flattened tin ball, then scraper the solder ball is too small and lack the foot of the hole on the full solder paste, and then use a heat gun to blow once again, in general, to get. If the solder ball size is also uneven, it can repeat the operation until the desired state.
#3 IC positioning and installation
First BGA IC has fillet coated side of the right amount of help paste, with a wind blowing gently heat gun, so to help paste evenly distributed on the surface of the IC, in preparation for welding. In some phone circuit board, printed in advance of the positioning frame BGA IC, such an IC positioning welding general not a problem. The following describes the circuit board I did not locate the box, the positioning method IC are the following:
Before removing the IC pen or stylus to draw a good line in week in and week BGA IC‘s, remember the direction, well marked, in preparation for re-welding. The advantage of this method is accurate and convenient, the disadvantage is easily washed off with a line strokes, using a needle to draw lines if efforts to master well, easy to hurt the board.
Before removing the BGA IC, IC‘s first four sides along with the labels attached to the circuit board is good, the edges of the paper edges are aligned with the BGA IC tweezers compacted cement. Thus, after removing the IC, the circuit board on the left labels affixed to the good positioning of the frame when reloading IC, as long as we label paper in front of several vacancies back to the IC. Pay attention to the choice of good quality strong sticky labels to stick, so that the welding process is not easy to blow off. If you think that one can not find the feeling of label paper thin, it can be used several layers of thick paper labels overlap into one, with a pair of scissors to cut the edge of the flat, attached to the circuit board, this time back to the IC equipment will feel a little better .
In removing the BGA IC after the circuit board plus a sufficient amount of flux paste, electric soldering iron to remove the excess solder board, and may be appropriate to each fillet on the tin boards are smooth and rounded (can not be used suction tin solder suction line level, or else find the handle in the following operations). Then plant a good solder ball BGA IC circuit board into the approximate location of the hand or tweezers and gently move around the front and rear IC pressure, then you can feel the contact between both sides of the fillet. Because both sides of the fillet is round, so the back and forth movement, if pointed, IC has a ‘climbed to the top of the hill‘ feeling. After alignment, as we advance in the IC‘s feet painted a little help paste, a certain viscosity, IC does not move. Viewed from the four sides of the IC that, if distinctly visible in a certain direction there is a empty foot board, described
IC for bias, and to reposition.
The excess solder on BGA IC removal, covered with a piece of white paper on top of the IC with a pencil on white paper repeatedly applied, so this piece of fillet of IC design was rubbing on the paper. Then the pattern attached to the right size and thickness of a stainless steel sheet, find a dentist drilling tool, please follow the pattern he drilled holes. Thus, a new plant Tin plate produced.
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