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Today, Shenzhen Da Tai Feng Xiaobian will bring you about the BGA repair table: BGA device repair process of the introduction of the ball, let's have a look ~
Planting ball:
Generally, the disassembled BGA components can be reused. However, since the welding balls at the bottom of the BGA are damaged to different degrees after disassembly, they must be treated with planting balls before use.
Choice of tin balls and accessories:
The selection of auxiliary materials used for planting balls is very important. At present, the main use of solder paste and welding paste. When using welding paste, the tin balls are often easily connected to the bridge in the hot air workstation environment after the chip heating of the ball, so it is recommended to choose tin paste for planting balls.
The tin ball is selected according to the datasheet of the chip. The main ingredients are lead-free 305, lead 63/37 and 90Pb/10Sn used by CBGA. The size is 0.3, 0.4, 0.5, 0.6 and 0.7mm. It should be noted that when selecting the solder paste process, the ingredients of the solder paste should be consistent with the ingredients of the tin ball, and the size of the tin ball should be smaller than the diameter of the original chip, so that the tin ball and the solder paste will be most close to the size of the original chip after reintegrating into the tin ball.
Several common methods of ball planting: The methods of ball planting vary according to different ball planting tools and materials, but the process is the same. That is, printing solder paste - placing ball - heating. The difference in the planting method is the second step of the ball placement. At present, there are three common ways to set the ball.
a. Multi-purpose ball planter
The opening size of the template is generally 0.05-0.1mm larger than the diameter of the tin ball. The template is fixed on the base. The tin ball is evenly scattered on the template. Then, the ball planter is placed on the repair workstation, and the BGA device printed with solder paste is drawn on the suction nozzle of the workstation (the solder paste is printed on the disk face down). The BGA is aligned according to the method of BGA welding, so that the bottom image of the BGA device is completely coincident with each tin ball image on the surface of the ball planter template. Then, the suction nozzle is moved down, the BGA device is affixed to the tin ball on the surface of the ball planting device template, and the BGA device is sucked up. The tin ball will be stuck to the corresponding pad of the BGA device, and the device is carefully removed with tweezers for subsequent heating. The advantage of this planting ball is that the template utilization rate is high. Only four templates of different specifications are needed to meet the requirements of most types of BGA planting balls. The disadvantage is that the operation is slightly complicated, and the visual alignment system of the workstation is needed, and the efficiency of mass planting balls is not high.
b. Special ball planter
The special ball planter needs to be manufactured according to the DATASHEET of the chip, a base loaded with BGA devices, plus a cover plate inlaid with printing screen plate and a cover plate inlaid with leakage ball template. In use, first of all, the cover plate of the printed mesh plate is loaded on the base loaded with BGA, after printing the tin paste, remove the cover plate, and then load the cover plate of the leakage ball template on the base, spread the tin ball evenly on the template, shake the ball plant, the excess tin ball from the template roll into the tin ball collection slot, so that the template surface exactly each leakage hole to retain a tin ball. Remove the cover vertically, observe whether there is a tin ball missing on the BGA device, and fill the tin ball with tweezers. The advantages of this planting ball are simple operation and high success rate. The disadvantages are that the cost of planting ball tooling is relatively high, and a set of BGA devices with different packages needs to be made.
c. Universal ball planter
The principle of this universal ball planter is similar to that of the special ball planter. The difference is that the base of this ball planter can control the width of X and Y direction and the height of Z direction through three screws, so that it is suitable for most BGA chips. After the chip is fixed, the subsequent process is exactly the same as that of the special ball planter. If the BGA of different packages is repaired, it is only necessary to make the corresponding printed mesh plate and leakage mesh plate, and then put the mesh plate into the cover plate adapter, adjust the alignment to the appropriate position and lock it.
Each of the three methods has its own advantages and disadvantages. Regardless of the ball planting method, the subsequent work will be placed on a pallet for reflow welding. When welding the tin sphere of BGA device is upward, it should be noted that the hot air volume should be adjusted to the minimum, so as not to blow the tin ball out of position. The temperature setting is also lower than the actual welding temperature. At the same time, the melting state of the tin ball should be observed timely, and the heating should be stopped for more than ten seconds in the melting state to reduce the thermal impact on the chip.
Well, the above is about the BGA repair table: BGA device repair process of the introduction of the ball, I hope to help you ~ to point a point of attention Oh
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