IPC-7530A Draft Document for Industry Consensus Only August 2016
Figure 3-9 Example of TC on Inner and Outer Rows – Drilling From Bottom of BGA and Other Components
3.1.3 Soak Zone
The soak zone is intended to bring the temperature of the entire board up to a uniform temperature. The ramp rate in this zone (100 to 180 C for tin lead and 140 to 220 C for SAC lead free) is much slower. The soak zone also acts as the flux activation zone for solder paste. The consequences of having too high a temperature in the soak zone can include: solder balls, solder splatter due to excessive oxidation of paste and spent flux activation capability. The purpose of long soak zone is to minimize voids, especially in BGAs. It is also common practice not to use soak zone but to steadily ramp the temperature from preheat zone to peak reflow. However, the likelihood of voids may be increased when ramping steadily to peak reflow temperature.
3.1.4 Reflow Zone
The peak temperature in the reflow zone should be high enough to obtain good wetting, and create a strong metallurgical bond. It should not be so high as to cause component or board damage or discoloration or, in worst case, delamination or charring of the board. Too low temperature may result in cold and grainy solder joints, nonmelted solder or poor intermetallic bonding. As shown in Table 7-3, the peak temperature in this zone should be maintained between 210 °C to 220 °C for tin lead and 230 °C to 245 °C for lead-free solder alloy. TAL should be
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