1。 The adjustment skills of thermal resistance and temperature of hot air gun of BGA module, BGA module is connected with circuit board by the whole bottom of package. Not by pin soldering, but by solder balls. The size of the module is reduced, and the size of the mobile phone is relatively reduced. However, the packaging form of this module also determines the characteristics of easy virtual welding. In order to strengthen this module, mobile phone manufacturers often use glue dripping. This increases the difficulty of maintenance. It takes a long time to remove the rubber-sealed module by blowing it with a hot air gun. Often in the process of blow welding, the temperature of disassembly and welding is not well mastered, and the module is damaged because of too high temperature. So how to effectively adjust the temperature of the air gun? Even if you can remove the module, you can't damage it! Tell you the heat-resistant temperature and welding precautions of several commonly used BGA modules. You must be familiar with the CPU of Motorola V998. Most of these modules are encapsulated with glue. The heat resistance of this module is relatively high. Generally, the temperature of air gun does not exceed 400 degrees, so it will not be damaged. We can adjust the temperature of the air gun to 350-400 degrees when disassembling and welding, and heat its surface evenly. When a solder ball pops up under the CPU, it means that the solder below has completely melted. At this time, we can gently pry it open with tweezers, so that it can be taken out safely. The module with similar welding method also uses Nokia 82 10/33 10 series CPU, but the glue used in the CPU package is different. Everyone should pay attention to the damage of glue to the pins on the motherboard when disassembling and soldering. Siemens 3508 audio module and 1 165438 CPU. These two modules are directly soldered to the motherboard, but their heat resistance is very poor, so it is generally difficult to withstand the high temperature above 350 degrees, especially the cpu with118. Generally, the temperature during welding should not exceed 300 degrees. We can put the bad CPU on the good CPU when welding, thus reducing the damage caused by direct blowing welding module. Blow welding time may be longer, but the success rate will be higher. 2. Remedial measures after the motherboard drops. Friends who have just started maintenance will definitely encounter the situation that the motherboard will fall when disassembling the module encapsulated with glue. If there are not many dropped solder joints, they can be repaired by connecting lines. When repairing this falling fault, I used the green oil of Tianmu Company as the curing agent for fixing the connecting wire.
There are basically two kinds of drops on the motherboard. One is that the pins can be seen on the motherboard, which is easier to handle. Just weld the stitches directly with wires, and leave a suitable length of wires in a circle and put them on the landing point. The other is via solder joint, which is more difficult to handle. First, dig out the lower stitches with a knife, and then draw a circle the size of a solder joint with copper wire and put it on the landing point. Add solder balls and heat with an air gun. So as to connect the ring and the pin together. Then it is cured with green oil, coated on the treated pad, and concentrated in the sun for a few seconds with a magnifying glass. The curing degree is better than that of hot air gun heating for one day. The solder joint fell off the motherboard, so we connected it with wires and cleaned it up. Apply green oil where fixing or insulation is needed,
Take it outside, illuminate the sun with a magnifying glass, and collect light and green oil. It will solidify in a few seconds.
3. Welding method when landing on the pad. After landing on the pad, clean the pad first, blow a little rosin on the module with the ball planted, and then put it on the pad. Be careful not to put it too straight, deliberately tilt it a little, but not too hard, and then heat it. After the solder ball under the module melts, the module will automatically adjust to the pad. Be careful not to swing the module during welding. In addition, when planting tin, if the solder paste is too thin, you can take out a little and put it on a napkin to suck the flux onto the paper. This solder paste is easier to use!