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Reflow soldering BGA rework and inspection

Reflow soldering BGA rework and inspection

Reflow soldering settings

1 When reflow soldering operation, set the welding temperature curve according to the size of the component and the thickness of the PCB. In order to avoid damage to the BGA device, the preheating temperature is controlled at 130~150°C, the heating rate is controlled at 1~2°C/s, The welding temperature of BGA is about 15 °C higher than that of traditional SMD, and the preheating temperature of pcb bottom is controlled between 160-180 °C.

2 Select the square hot air nozzle that matches the size of the device, and install the hot air spray on the connecting rod of the upper heater, taking care to install it smoothly.
3 Fasten the hot air nozzle on the BGA device, and be sure uniform distance around the device.

4 Turn on the heating power, adjust the amount of hot air, and start reflow welding of the BGA device.

5 After welding, lift the hot air nozzle up and remove the surface assembly board.
Prototype pcb manufacturing BGA inspection

BGA welding quality inspection requires X-ray or ultrasonic inspection equipment; there is also a fiber microscope, which is checked from the periphery of the BGA on the pcb circuit board, and the image is displayed on the display. This method can only observe 7 rows of solder ball images, and the inspection speed is slow. If there is no inspection equipment, the quality of pcb welding can be judged by functional test; it can also be checked by experience: lift the SMA with welded BGA, observe the light around BGA, observe whether the light transmission, the distance between the BGA and the PCB is Consistent or not, whether the solder paste is completely melted, whether the shape of the solder ball is correct, the degree of collapse of the solder ball, etc., the experience is used to judge the soldering effect. Please refer to the following items when judging.
1 If it is opaque, it means that there is a solder ball between the solder joints of the prototype pcb fabrication or the solder balls.

2 If the shape of the solder ball is not correct, there is a buckle phenomenon, indicating that the temperature is not enough, and the self-positioning effect is not fully completed when the reflow welding is performed.

3 Solder ball collapse degree: after the reflow soldering, the distance between the BGA bottom and the PCB collapse 1/3~1/2 is normal than the pre-welding ; the solder ball collapses too little, indicating that the temperature is not enough, easy to occur, virtual welding and cold welding; The ball collapses too much, indicating that the temperature is too high and bridging is likely to occur.

4 If the distance between the BGA and the PCB is inconsistent, indicating ambient temperature is not uniform.