Split welding of BGA IC

Mobile phone bga ic welding and troubleshooting skills

Zhu haiqing

Selection of a tin planting Tool

1. Tin planting Board

Commercially available tin planting boards are generally divided into two categories: one is to make all models on a large connected tin planting Board; the other is a board of each IC, the two planting

The tin board is used in different ways. The method of using the connected tin pad is to print the tin paste on the IC, then pull the tin pad, and then blow it into the ball with a heat gun. The advantage of this method is that the operation is simple and fast, and the disadvantage is that

1. Tin paste cannot be too thin.

2. For some IC that is not easy to apply tin, such as soft flash or the CPU after removing the glue, the tin balls will roll around and it is very difficult to apply tin.

3. After one tin planting, the size of the tin balls and the defects of blank content cannot be processed twice.

4. When planting tin, do not use a heat gun to blow the tin planting board together. Otherwise, the tin planting board will be deformed and bulge, resulting in no tin planting.

The use of small tin planting board is to fix the IC under the tin planting board, scrape the tin paste and then blow the board together, compress the ball and then remove the IC. It has the advantage of tin planting Board during hot air blowing

Basically no deformation, if there is a lack of feet or the tin ball is too small after a tin planting phenomenon can be secondary treatment, especially suitable for new users. I usually use this tin board. The method we will introduce below is to use this tin board.

2. Tin Paste

We recommend that you use the imported tin paste in a bottle, for example, 0.5-1 kg. Fine and even particles, slightly dry for High. We do not recommend that you purchase the tin paste containing the syringe. In

In emergency use, the tin paste can also be self-made, can be used for low melting point ordinary soldering tin wire with a heat gun melt into a block, with a fine grinding wheel grinding into a powder, and then use a proper amount of flux stirring even.

3. Scraping Tool

There are no special requirements for this, as long as you can use it. We use the six pieces of the goot tool to assist welding. Some friends use

You can use the marker or even the toothpick.

4. Hot air gun

It is best to use a heat gun with the function of numerical control constant temperature, remove the wind nozzle and directly blow the welding. We use the 950 heat gun from Tianmu.

5. Flux

We use the 'solaule 'sold by the company, which is a soft paste similar to butter. Advantage:

1. Excellent welding performance.

2. No corrosive effect on IC and PCB.

3. the boiling point is only slightly higher than the melting point of soldering tin. The melting of soldering tin begins to boil heat absorption and evaporation shortly after welding, so that the temperature of IC and PCB can be kept at this temperature-this

The truth is the same as that of using a pot to boil water. As long as the water is not dry, the pot will not heat up and burn out.

6. It is best to use the cleaner in the sky. The water in the sky has excellent solubility to Rosin Solder Paste and so on, and it cannot be used to clear wine with poor solubility.

Binzhi tin operation

1. Preparations

Add a proper amount of solder paste on the ic surface, and remove residual solder on the IC with a soldering iron (note that it is best not to use a tin line to suck, because for those soft-encapsulated IC such

Torura font library, if the use of tin wire to suck, will cause IC welding pin indent brown soft skin inside, resulting in difficulty in tin), and then wash with the water that day.

2. Fixed IC

There are many plug-ins on the market, all equipped with a base made of aluminum alloy for fixing IC. In fact, this seat is not easy to use: first, the operation is very troublesome, you need to use a fixed fixture, If the fixed is not strong when the soldering pad is a move, the success of a loss; second, the IC on the base when blowing, even the large aluminum alloy base is blown hot, the tin paste on the IC will melt into a ball. In fact, the fixed method is very simple, as long as the IC is aligned with the tin planting board of the hole (Note that if you are using the one side of the hole large side of the hole small tin planting board, the big hole side should face the IC), the opposite side with the price sticker can be stuck, not afraid of planting tin board moving, how to blow it. For skilled maintenance personnel, you can not even use the sticker. After the IC is aligned with the tin board, press the hand or tweezers to hold it tight, and then the other hand scrape the tin and blow it into the ball.

3. Tin Paste

If the tin paste is too thin, it is easy to boil during soldering, resulting in difficulties in ball formation. Therefore, the more dry the tin paste, the better, as long as it is not dry hard into a block. If it is too thin, use a napkin to press it and suck it up. Our usual practice is to pick some tin paste and place it on the inner cover of the tin paste bottle so that it can naturally dry a little.

Use a flat knife to select a proper amount of tin paste to the tin pad, and press it down to make the tin paste evenly filled in the small hole of the tin pad. Pay special attention to the four corners of the IC

. The key to the tin paste is to compress the tin pad. If there is a gap between the tin pad and the IC, the tin paste in the gap will affect the formation of the tin ball.

4. Blow welding into ball

Remove the nozzle of the hot air gun and set the air volume to the maximum. If you use the tmc950 air gun of Guangzhou Tianmu company, set the temperature to-degrees. Shake wind Tsui pair

The tin planting board is slowly heated evenly, so that the tin paste is slowly melted. When a tin ball is generated in some small holes of the tin board, it indicates that the temperature is in place. In this case, the nozzle of the hot air gun should be raised to avoid the temperature rising. If the temperature is too high, the tin paste will boil sharply, resulting in tin planting failure. If the temperature is too high, the IC will be overheated and damaged.

5. Resize

If we find that the sizes of some tin balls are uneven, or even some feet are not planted with tin, we can use a paper cutter to expose the large tin balls along the surface of the tin board.

Split and flat, and then use a scraper to fill up the tin paste in the small and missing holes, and then blow it again with a hot air gun. Generally, this will be done. If the size of the tin ball is uneven, repeat the above operation until the ideal state.

Positioning and installation of Tri-IC

First, apply the right amount of solder paste to the side of the bga ic with welding feet, and gently blow it with a heat gun to make the solder paste evenly distributed on the ic surface and prepare for welding.

On some mobile phone circuit boards, bga ic positioning boxes are printed in advance. The welding and positioning of such IC is generally not a problem. Below I will mainly introduce the absence of a positioning box on the circuit board. The IC positioning methods are as follows:

1. Wire painting and Positioning Method

Draw a line on the week of the bga ic with a pen or needle before removing the IC, remember the direction, make a mark, and prepare for the heavy welding. The advantage of this method is accuracy.

It is really convenient. The disadvantage is that it is easy to clean the line with strokes. If the needle is hard to grasp, it is easy to hurt the circuit board.

2. sticker Positioning Method

Before removing the bga ic, paste the paper on the circuit board along the four sides of the IC with the tab paper. The edge of the paper is aligned with the edge of the bga ic and compacted and pasted with tweezers. In this way, after the IC is removed, there will be a labeling box attached to the circuit board. When reinstalling the IC, we only need to put the IC Back to the space in several tabs. Pay attention to the selection of labeling paper with good quality and strong viscosity, so that it is not easy to fall off during the blowing welding process. If you think that a layer of label Paper is too thin to find the feeling, you can fold several layers of Label paper into a thick one, and use scissors to flatten the edge and paste it on the circuit board, in this way, the feel will be better when the device is loaded back into the IC. Some netizens use plasticine gypsum powder and other materials to stick to the circuit board for marking, some netizens also made metal jigs for bga ic welding positioning. I think the Paster method is simple and practical, and will not pollute the damaged lines and other components.

3. Visual Method

When installing the bga ic, first erect the IC, then you can see the pins on the IC and the circuit board at the same time, first compare the welding position, and then vertically compare the welding position. Remember which line on the circuit board overlaps or is parallel to which component on the edge of the IC in the vertical and horizontal directions, and then install the IC according to the reference object according to the visual results.

4. Feel Method

After removing the bga ic, add a sufficient amount of solder paste on the circuit board, and remove excess solder paste from the board with a soldering iron, in addition, the solder joints of the circuit board can be smooth and round (the solder joints cannot be flushed with tin wires; otherwise, the feel cannot be found in the following operations ). Then place the bga ic with the tin balls on the circuit board in the approximate position. Move the left and right sides of the IC with hands or tweezers and gently pressurize it. Then you can feel the contact situation of the welding feet on both sides. Because the welding feet on both sides are circle, if you aim at the back and forth movement, the IC will have a feeling of 'crawling to the climb. After alignment, the IC will not be moved because we have applied a welding paste on the foot of the IC beforehand. From the four aspects of the IC, if you can clearly see that the circuit board has an empty foot in a certain direction, it indicates that the IC is incorrect and you need to locate it again.

After bga ic is set, it can be welded. Like when we plant tin balls, we can remove the wind tip of the hot air board and adjust it to a suitable air volume and temperature so that the central part of the wind tip is aligned with the IC.

The central position of, slow heating. When the IC goes down and the surrounding Solder Paste overflows, it indicates that the solder ball has been fused with the solder joints on the circuit board. At this time, you can gently shake the heat gun to make the heating uniform and full. Due to the effect of surface tension, the solder joints between the bga ic and the circuit board will be automatically aligned and positioned. Note that do not press the bga ic hard during the heating process, otherwise, the solder may overflow, which can easily lead to disconnection and short circuit.

4. methods and skills for solving common problems

Question 1: What should I do if some unfamiliar models of the BGA IC have no corresponding tin board on hand?

Answer:

1. first, try the existing tin planting board on the hand. Is there the same distance as the bgaic welding foot that can be set up? It doesn't matter even if some feet on the tin planting board are empty, you only need to implant each foot of the bga ic into a tin ball. For example, the CPU and flash of gd90 can be applied using a tin board of 998cpu and power IC.

2. if you cannot find a tin board that can be applied, follow the method below to make a tin Board: remove the excess Solder Pad On the bga ic, and cover it with a blank sheet of paper, use a pencil on the White Paper repeatedly, so that the welding foot pattern of this IC will be printed on the White Paper. Then paste the image to a thick and appropriate stainless steel piece, find a dental doctor with a drilling tool, ask him to drill the hole according to the figure. In this way, a brand new tin planting board is made.

Problem 2: When welding bga ic, high temperatures often affect the glue-mounted IC, which often causes other faults such as no startup. I used my phone to cover all the shielded covers. The temperature was too low and the welding could not be done. It was very distressing.

Answer:

It cannot be covered with a screen cover. It can block your eyes, but it cannot block hot air. My method is simple and practical. When welding is performed

A few drops of water, water heated evaporation will suck a lot of heat. As long as the water does not work, the temperature of the IC next to it is kept at a safe temperature of about 100 degrees, so that nothing will happen.

.

Question 3: When I repair my 998 mobile phone, I often do not need to start flash after welding. I used lt48 to read the flash materials and install them back several times, it is also not open

Machine.

Answer:

There are several reasons for this:

1. When flash is blown for welding, the high temperature affects the CPU, which can be avoided with the skills I have mentioned;

2. Do not wait until the mobile phone is completely cool after flash welding. Many machines will encounter software faults. At this time, we can solve the problem by using Tianmu's enhanced type Taiji Wang without removing the font and rewriting the data;

3. I have noticed that many of my friends have problems with welding methods. They always like to use tweezers to gently drag the IC after Soldering Tin melting, for fear of poor welding. This approach is wrong, especially for soft-encapsulated IC such as the 998 font library, its welding foot is actually reduced in a brown soft film, shaking during welding, it will cause the tin ball to fall. At this time, if we use Tianmu company's Taiji Wang online, we will see that the LCD of Taiji Wang displays the word "ic touch 04", with ordinary EMMI-BOX can not see, but cannot communicate.

Problem 4: A l2000 mobile phone, originally was able to boot, because of the key failure I used the water bubble for two hours, the results can not boot, EMMI-BOX can not communicate. Excuse me

Where is the problem?

Answer:

Note that the common soft-encapsulated BGA font cannot be filled with water or Sol. Because Tianna water and soluble glue are both organic solvents, soft

The glue in the BGA font is highly corrosive, which causes the expansion of the glue to lead to decommission of the font.

You can simply remove the BGA font of the machine and use the lt48 production mode. There must be a lot of broken feet.

Problem 5: When we replace 998 of the CPU, we find that the green solder mask on the circuit board is de-painted after removing the CPU. After the CPU is reinstalled, the mobile phone suffers a large current fault, there are signs of burning when you touch the CPU by hand. I think it must be the reason why the solder mask under the CPU is damaged. A short circuit occurs in the soldering CPU. How can I solve this problem?

Answer:

This phenomenon is very common when welding 998 of the CPU, the main reason is that the time spent soaking with soluble glue is not enough, not transparent. In addition, when removing the CPU, you need to use hot air to blow the edge and use tweezers to fully tap into each part of the CPU surface-to prevent circuit board paint and circuit board solder joints from broken feet.

If the problem occurs, you can go to the manufacturer of the Production Circuit Board to find the special resistance flux (commonly known as 'aligreen') and paste it in the place where the paint is removed.

, Use a soldering iron to solder the circuit board to a new CPU. In addition, the tin balls on the original CPU package we purchased on the market are too large to cause short circuits, while the tin balls we made with the planting tin board are relatively small. You can remove the original tin balls, re-plant the tin and then install it on the circuit board, so it is not prone to short circuit.

Question 6: I have been plagued by a problem, that is, many 998 of mobile phones cannot start up because the solder joints of the circuit boards under the CPU are broken when the CPU is down or detached. Some mobile phones are still quite new, so it's a pity that they will be scrapped in vain. What are the tips and methods?

Answer:

This kind of fault is indeed very 'put' and has been plagued by the majority of maintenance personnel. Next I will introduce our own processing experience: first, put the circuit board under the microscope to determine which are empty feet and which are indeed broken. If you only see a smooth 'nest 'At the bottom, there is no line extension next to it. This is an empty foot;

If there is a line extension next to the broken foot or a split 'burr' at the bottom, it indicates that this point is not an empty foot and the CPU must be reloaded after processing.

1. Connection Method

For a breakpoint with a line extension next to it, we can use a knife to gently scrape the line next to it and use a tin-coated wire (the paint line should not be too thin or too rough, if the CPU is too small, it is easy to shift the paint line when the CPU is reloaded.) one end is welded to the line next to the breakpoint, and one end is extended to the breakpoint position, we can use a needle under the microscope to gently dig into the breakpoint, dig into the root highlights of the broken line, and then carefully weld a short line. After connecting all breakpoints to the thread, carefully weld the CPU in place. During the welding process, the CPU cannot be switched.

2. Flying Line Method

For breakpoints that are difficult to use the above connection method, we can first check the information and the method of comparing the normal Board to determine where the point is to go to the circuit board. Then weld it to the corresponding tin balls of the bga ic with a very fine patent wire. (The method of welding is to put bga ic with a tin ball face up, blow the heat with a heat gun, insert one end of the paint wire into the tin ball, after connecting the wire, the line along the gap of the tin ball, turn to the opposite side of the IC and fix it with a heat-resistant sticker to prepare for welding. Be careful when welding. After the IC is cooled, weld the lead wire to the position we have found in advance.

3. Edge Method

We can note that many bga ic (for example, 998 power IC 2000cpu 8210cpu, etc.) have a thin edge. We can find that there are many golden yellow feet on the edge, this is a trace left by the manufacturer when producing the IC. We found that these feet have a one-to-one relationship with the bga ic feet, and clever use of these feet can greatly facilitate our repair work. The use of these feet to fly lines can solve the problem of a large number of circuit boards and IC disconnection. Sometimes, as long as the data is accurate to the number of bga ic problems, we can repair the edge of the IC, so as to eliminate the trouble of welding bga ic. For example, if a 147 * key failure occurs on a nokia8210 mobile phone, the system determines that the CPU is broken to the keyboard matrix, it is found that this line is in line with the central gap on the top side of the CPU to the right, and the faulty machine is disconnected. Through the flying line, it is easy to solve the fault, if we use the traditional method to remove the welding CPU, the difficulty and risk can be imagined. Another example of 998 to 8088: When we use 998 to change the phone number to 8088, we usually upgrade the software first and then change the button panel. modify the antenna interface. shift the recording key. the most difficult thing to solve when changing the chassis is the problem of displaying lights by phone. Usually we use an additional flashlight circuit, or fly to 998 of the original back flashing light. These "Crossing the sea" parties are easily identified, because no matter how the flashing lights are made, they cannot be controlled by the menu options on the mobile phone. Is there a complete solution?

I noticed that in the 8088 mobile phone, the flashlight is controlled by two CPU feet, and on the v998 mobile phone, these two feet are empty, we can achieve the goal of "false or false. However, it is unrealistic to remove the CPU lead for the lantern function. I found that these two legs are actually the same as the bottom side of the CPU close to the end side of the plug-in from the bottom side of the right to the bottom of the 3.4 thin lines, as long as an K1 Compound Pipe and two throttling resistors are added to the incoming line, our v998 will be "fake.

4. Ball planting

For the breakpoint with no line extension around and "rooted in the ground", we dig it with a needle under the microscope. After seeing the highlights, when we use a needle to dig a little bit of tin, we use the tin paste to put it on the top, and then blow it into the ball with a hot air gun. If the tin ball is flushed with a small brush, it won't fall down, or compare the measurement data to confirm that the solder joints have been properly connected. Note that the tin balls on the board should be slightly larger. If the tin balls on the board are too small to be welded to bga ic, the tin balls on the board will be attracted by the tin balls on the IC.

5. Repair Method

To deal with the breakpoint of the circuit board that "takes root", dig out the highlights under the microscope and inject a Special Circuit Board inspector into the broken foot. This German-made reducing agent is usually used to repair the broken line of the circuit board, through the hole point is very easy to use, its characteristics are low resistance, high temperature resistance and easy to Tin. After the breakpoint is repaired with the repair agent, the IC can be reinstalled after it is dry to bring the phone back to life.

Problem 7: Some repair personnel repair the l2000 and 2088 mobile phones, due to the poor temperature control of the heat gun, the result is that the circuit board under the CPU or power IC due to overheating blister bulge, so that the phone is scrapped. In this case, is the mobile phone still saved?

Answer:

I don't know whether we noticed it. When we repair the l2000 Series Mobile Phones, sometimes the circuit board under the CPU or power IC is slightly blister, as long as the CPU and power IC are properly installed, the mobile phone can work normally after it is turned on. In fact, the l2000 board base material is still good. After overheating and foaming, most of them will not cause broken lines. We just need to cleverly weld the above IC

The mobile phone will be able to return to life. To fix such mobile phones, we adopt the following three measures:

1. Flat the circuit board. Adjust the hot air gun to the appropriate wind and temperature light blow circuit board, while blowing side with tweezers back light pressure wire board lung into a part, to make it as smooth as possible.

2. Add a large tin ball to the IC. No matter how the circuit board is processed, the line cannot be completely flat. We need to plant a large tin ball on the IC to adapt to welding on the uneven circuit board. We can take two pieces of the same TIN planting board and stick them together with tape, and then use this "thickened" Tin planting board to plant tin. After planting tin, we will find it difficult to remove the IC. At this time, do not rush to remove it. you can apply a little solder paste on the surface of the tin board to overhead the tin board, IC down, and blow it gently with a heat gun, soldering Tin Melting

The IC is easily separated from the tin planting board.

3. In order to prevent the original blister of the circuit board from being elevated by high temperature when welding bga ic, We can suck enough water on the opposite side of the circuit board when installing the IC.

To avoid the PCB temperature being too high.

Question 8: I think it is too complicated to use tin planting boards. Is there a simple method?

answer:
yes! In the provincial government's largest electronic maintenance tool store, you can buy a welding tool called "tin pot". The shape is a small stainless steel box with a heat-adjustable base. We can add a proper amount of soldering tin in the tin pan, adjust the temperature to about 300 degrees, and inject a small amount of flux to increase the fluidity of soldering tin. Use tweezers to hold the IC flat for tin planting, and place it in the tin pot for a quick dip. Wait for the IC to cool down and then quickly dip it ...... after repeated 3-5 times, the beautiful tin beads are generated at the bottom of the bga ic. This method is very convenient after practice, but also can freely control the size of the tin ball, especially suitable for a large number of tin planting and maintenance. Disadvantage 1: The soldering tin in the tin pot is prone to deterioration for a long time and is not suitable for a small amount of maintenance; disadvantage 2: it cannot be soft encapsulated bga ic tin planting.
we used this method to plant tin when the tin Board was not available a few years ago, and the effect was superb.