Setting appropriate temperature profiles is crucial for successful BGA chip soldering using a BGA rework station. The temperature profile for BGA rework stations generally consists of five stages: preheating, ramp-up, soak, reflow, and cooling. Let’s delve into each stage in detail.
- Preheating: The primary purpose of the preheating and ramp-up stages is to remove moisture from the PCB, prevent bubbling, and preheat the entire PCB to prevent heat damage. Typically, the temperature range for preheating is between 60°C to 100°C, with 70-80°C being commonly set for about 45 seconds. Adjustments can be made by either lowering the ramp-up temperature or shortening the time if the temperature is too high, or vice versa if it’s too low.
- Ramp-up: After the soak period in the second stage, the temperature of the BGA should be maintained between 150-190°C for lead-free solder or 150-183°C for leaded solder. Adjustments can be made by lowering the temperature or shortening the time if it’s too high, or vice versa if it’s too low. (For lead-free: 150-190°C, 60-90s; for leaded: 150-183°C, 60-120s). The ramp-up temperature should be slightly higher than the soak temperature.
- Soak: The soak stage temperature should be lower than the ramp-up stage. Its purpose is to activate the flux, remove oxides from the metal surface, and enhance wetting. The actual solder temperature during this stage should be controlled between 170-185°C for lead-free solder or 145-160°C for leaded solder. Adjustments can be made by lowering or raising the soak temperature as necessary.
- Reflow: The peak reflow temperature should reach 235-245°C for lead-free solder or 210-220°C for leaded solder. Adjustments can be made by slightly lowering the reflow temperature or shortening the reflow time if the temperature is too high, or vice versa if it’s too low. The temperature setting for the lower part of the BGA rework station should be higher than the upper part during the reflow stage.
- Cooling: The cooling stage should be set below the melting point of the solder balls to prevent rapid cooling and potential damage. Generally, the bottom reflow temperature can be set between 80-130°C, depending on the thickness of the board. This helps prevent deformation caused by significant temperature differences between the heated portion and the surrounding areas. This is one of the reasons why BGA rework stations with three temperature zones achieve higher repair rates.
By adjusting the temperatures in each stage based on the PCB characteristics, the optimal temperature profile can be achieved. After heating, ensure that the maximum temperature, preheating time, and cooling time meet the requirements. If adjustments are needed, follow the aforementioned methods and save the optimal temperature profile parameters. Typically, BGA rework station manufacturers provide detailed instructions for setting temperature profiles.
With this comprehensive guide, users can effectively set temperature profiles for BGA rework stations to achieve successful soldering of BGA chips.
