1. The temperature rise rate of the lead-free preheating zone is generally controlled at 1.2~5℃/s (sec), the temperature of the preheating zone is generally not more than 160℃, the temperature of the holding zone is controlled at 160-190℃, and the peak temperature of the reflow zone is normal It is controlled at 235-245℃, and the temperature is maintained for 10-45 seconds. The time from heating to peak temperature should be maintained at about one and a half to two minutes.
2. The melting point of leaded solder paste is 183 degrees, while the lead-free solder paste is 217 degrees. That is to say, when the temperature reaches 183 degrees, the leaded solder paste begins to melt, and the melting point of the actual solder ball will be higher due to chemical characteristics. Solder paste.
3. Common sense of the machine: 1. Widely used: upper hot air + lower dark infrared, 2. Three-temperature zone model: upper hot air + lower hot air + lower dark infrared, 3. Full infrared type: upper infrared + lower dark Infrared, the main point: different types of products have different heating methods and temperature programs when they are used.
4.The following uses hot air as an introduction; hot air heating uses the principle of air heat transfer, using high-precision, controllable and high-quality heating controls to adjust the air volume and wind speed to achieve uniform and controllable heating. When soldering, the BGA chip body is due to The reason for heat transfer is that the temperature of the tin bead part of the BGA chip will be different from the hot air outlet. When setting the temperature for heating, (because different manufacturers define different temperature control temperatures for the machine, there are certain temperature requirements (The data in this article are all used by Zhuomao models), we must take the above factors into account, we also need to understand the performance of the tin beads, and set the temperature range (for specific setting methods, please refer to the manufacturer’s technical guidance), The key is to adjust the maximum temperature range. First, set a value (235 degrees for lead-free, 220 degrees for lead), and pay attention when running the desoldering station for test heating and heating. In the case of temperature resistance, the entire heating process should be monitored. When the temperature rises above 200 degrees, observe the melting process of the solder ball from the side (you can also see from the patch next to the BGA, use tweezers to gently Touch it, if the patch can be displaced, it proves that the temperature has reached the requirement), when the BGA chip solder ball is completely melted, it will be obvious that the BGA chip sinks. At this time, we need to compare the temperature displayed on the machine instrument or touch screen Record the running time of the machine, and add 10-20 seconds to the temperature time when it melts at this time to get a very ideal temperature!
Conclusion：
When doing BGA, the solder ball starts to partition when it reaches the highest temperature section for N seconds. You only need to set the highest temperature section of the temperature curve to the highest temperature constant temperature N-20 seconds. For other procedures, please refer to the temperature provided by the manufacturer. The curve parameters are generally controlled at about 210 seconds for the entire process of lead soldering, and the lead-free control at about 280 seconds should not be too long. Too long may cause unnecessary damage to PCB and BGA! BGA rework station temperature setting introduction.
