Weak current College】 【BGA IC IC processing techniques and frequently asked questions.

Methods applicable to the motherboard and South Bridge

A selection of reballing tools

1. implant Tin plate on the market of reballing Board generally fall into two categories: one is to do all the models in a big twins reballing Board; the other is a Board for each IC, the growing use of Tin plate.
Siamese reballing plate using the Tin paste printing to the IC, the implantation of Tin plate screeching, then use hot air gun into a ball. The advantage of this approach is fast and simple operation into the ball, the disadvantage is that 1. Tin paste should not be too thin. 2. for some not easy on Tin of IC such as soft sealed flash or go to glue the CPU, after blowing ball ball will roll out, very difficult on the Tin. 3. once reballing cannot on Tin ball size and vacancies point second treatment. 4. reballing cannot even reballing Board together with a hot air gun blow Tin plate, otherwise implant will lead to deformation, reballing.
Small reballing plates used by IC to the implantation of Tin plate below, scraping up Tin paste link plate with blowing, pellet cooling after IC. It has the advantage that hot air blow Tin plate base when implanted without distortion, once reballing after missing foot ball is too large or too small phenomenon to secondary treatment, especially for a novice to use. I usually just use the planting of Tin plate, the method described in the following we are using this planting Tin plate.

2. Tin paste is recommended to use bottled imported Tin paste, 0.5-1 kg of a bottle. Granule fine and uniform, slightly dry is excellent. Not recommended to buy that kind of Tin paste syringe. In emergency use, Tin paste can also be self-made, low melting point available for general use hot air gun solder wire melting into blocks, fine grinding powdered, then appropriately flux after using it, stir round evenly.
3. scrape pulp tools that do not have any special requirements, just use the convenient. We are using GOOT that six sets of help welding tool in flat mouth knife. Have a friend with a screwdriver or toothpick can, as long as smoothly.
4. hot air gun is better to use a numerical apertures of hot air gun, get rid of the wind blowing nozzle welding directly. We use the tianmu company 950 hot air gun.
5. flux we use tianmu company sold ' welding Po Le ', the contour is like butter paste. Advantage 1. auxiliary welding effect is extremely well. 2. on the IC and PCB not corrosive. 3. its boiling point is only slightly higher than the melting point of the solder, solder melts when the welding will soon begin boiling heat absorbing vaporization, IC and PCB temperature maintained at this temperature-this truth and we use water pot, as long as the saying goes: "water is not dry, the pot is not heating up burned.
6. cleaning agents used days that water is the best, the day the water on, Rosin help solder paste has very good solubility, solubility cannot be used without a good wine.

Second reballing operation

1. preparations
In the IC surface combined with the right amount of help to solder, soldering residues on the IC solder removal (note that it is best not to use the absorption line to draw, because for those soft package IC such as Motorola's fonts, if you go with absorption lines, absorption causes IC's leg indent brown soft skin, cause difficulties on the Tin), then use the days the water.
2.IC fixed
There are many reballing Kit tools, are equipped with an aluminum alloy manufactured to a fixed base of IC. This seat is very good: a is operating very troublesome, you want to use fixture fixed, if fixed is not strong blow Tin plate welding plant when a move is nothing; the second is the IC on the base blowing, to even the largest block of aluminum alloy Base are blowing hot, IC on Tin paste before melting into a ball. In fact fixed method is very simple, as long as the IC alignment reballing plate hole (note that if you are on the side of the hole side hole smaller reballing plate, large holes in one side should be facing IC), the reverse side with a price sticker in prison, not afraid of implantation of Tin plate movement, like how to blow it. For operation of skilled maintenance staff, even the stickers do not have the implantation, IC Tin plate with hands or tweezers Press firmly fixed, and then another hand scraping blow Tin solder paste into a ball.
3. on Tin paste
If Tin paste too thin, it is easy when welding the boiling causes the ball hard, so the more stem Tin paste the better, as long as not doing hair hard into blocks. If too thin, available paper napkin pressing sucks. Our usual practice to pick some Tin paste: the Tin paste inside the lid of the bottle, let it air dry naturally. With flat blade knife pick just the right amount of Tin paste to reballing plates, scrape down firmly, while scraping edge pressure, solder paste evenly fills in the holes of the implantation of Tin plate. Note in particular the ' care ' about the corners of the holes of the IC. When Tin paste on is the key to be pressed reballing plate, if not pressing the reballing Board and IC gap exists between the gaps in Tin paste will affect formation of Tin ball.
4. blow-ball
The hot air gun air nozzle removed, will air volume to maximum, if you use the Guangzhou Tian Mu company air, temperature TMC950 to 330-340 degrees. Rocking on the wind Tsui reballing slowly heating plate, Tin paste slowly melting. When you see the reballing Board of individual small holes in the ball is generated, indicating the temperature have been put in place, you should raise the hot air gun wind Tsui, avoid temperatures continue to rise. Too high a temperature will cause a violent boiling Tin paste, causing reballing failed; serious may also make the IC overheat damage.

5. resize
If we blow after welding the ball found some Tin ball size is uniform, and even individual foot not implanted on the Tin, with a knife along the reballing surface is too large to reveal some of the Tin ball squared, then drag the ball too small and ischemic foot hole covered with Tin paste, and then use hot air gun and then blowing once, as a general rule it did. If the ball is not uniform in size, you can repeat the operation until the ideal State.

3 IC orientation and installation

You will have leg BGAIC side coated with just the right amount of help to solder paste, a hot air gun brush off a blow, so will solder paste uniformly distributed over the surface of the IC, ready for welding. In some mobile phonesOn the circuit board, with the position box BGAIC, this IC is not a problem of welding position in General. Here I introduce the circuit board is not positioned box, IC orientation by the following:
1. draw line positioning method before removing the IC with a pen or needles BGAIC painted line of Mo, remember the direction, well marked, centred in preparation for welding. The advantage of this approach is accurate, the disadvantage is with stroke line easily washed off, draw a line with needle grasp if force is not good, easily hurt and circuit board.
2. stickers positioning method remove BGAIC, along the sides of IC with labels in the circuit board on the edges of the good, and the edge, BGAIC tweezers compaction unstuck. In this way, remove the IC, the circuit board on the left label affixed good location box. Reload IC, we just looked at several sheets of labels in the space provided to IC back then. Pay attention to the selection of quality better adhesive strong label paper to stick to this process of blowing welding is shedding. If you feel that a layer of label paper is too thin could not find the feeling that you can use several layers of labels overlap into thick one, use scissors to cut flat edge, attached to the circuit board, which is added back to the IC when the handle is better. Some netizens use modeling clay materials such as gypsum powder sticks to the circuit board on the mark, some netizens also homemade metal fixture welding to BGAIC. I think that still use stickers of simple and practical methods, and pollute injury lines and other components.
3. Visual method to install the first BGAIC IC erected, then you can also see IC and PCB pins on the first to compare the welding position, and then compare the welding position vertically. Remember the edges of the IC in horizontal direction and circuit boards on which lines coincide or parallel with which components, and then under Visual results in accordance with the reference to install IC.
4. touch method after removing BGAIC, circuit board plus plenty of help to solder, soldering will board the excess solder removal, and it may be appropriate to the Board on a tin of each leg are smooth and mellow (cannot absorb line will solder joint aspiration, otherwise in the following operations cannot be found in touch). Then the planting good ball onto the circuit board BGAIC approximate position with the hands or tweezers and move around the IC and gently before and after compression, then you can feel the contact with both sides of the leg. Because the two sides of the leg are round, so when you move, if at the IC has a ' climb to the top of the slope ' feeling. Alignment, as we advance in IC feet a little help on coating of solder paste, a certain viscosity, IC does not move. From IC's four sides look, if in one direction can clearly see the circuit board with a row of empty legs, IC on, to relocate.
BGAIC set in place, can be welded. And when we reballing ball, put the hot plate with adjustable air nozzle removed, to an appropriate amount of wind and temperature, let the wind Tsui's central location at the center of the IC, slow heating. When you see the IC to the next sink and around help, solder paste overflow ball has and PCB solder fused together. At this point you can gently swaying hot air gun makes heating fully, because surface tension evenly, BGAIC and circuit board solder joints between automatically align positioning, note in the heating process not to push and hold BGAIC, this will make solder spills, it is easy to result of feet and short circuit.
Self-made reballing plate: BGAIC superfluous solder removal, use a paper cover to IC, pencil on white paper, so this repeatedly smudge IC's leg was rubbing the drawings on white paper. And then the pattern to a size suitable for stainless steel sheet thickness, find a dentist of drilling tool, drilling and well as his drawings. In this way, a new implant Tin plate is made of the