To solder and remove BGAs (Ball Grid Array) chips, it’s best to use a dedicated BGA rework station. However, if you don’t have access to one for small-scale rework, you can also use tools like a hot air gun or an electric soldering iron, although the efficiency of soldering using these tools is relatively low and success is not guaranteed. Today, I’ll explain the methods and preparations for hand-soldering BGA chips.
- Required Tools:
- Hot air gun: Used for removing and soldering BGA chips.
- Electric soldering iron: Used for cleaning residual solder on BGA chips and PCB boards.
- Tweezers: Used to secure BGA chips during soldering.
- Medical needle: Used for lifting BGA chips during removal.
- LED magnifying lamp: Helps observe the position of BGA chips.
- Solder: Used for soldering.
- Solder paste stencil: Used for applying solder paste to BGA chips.
- Solder paste: Used for applying solder.
- Spatula: Typically included in solder paste stencil kits.
- Mobile phone repair platform: Used to secure PCBs; should be reliably grounded.
- Anti-static wrist strap: Worn on the wrist to prevent ESD damage to electronic components.
- Small brush, air blower: Used to remove impurities around BGA chips.
- Flux: Use specialized BGA flux.
- Specific Operating Methods:
- Apply a suitable amount of flux to the top of the BGA chip to prevent dry blowing and to evenly melt the solder balls underneath. Adjust the heat switch to 3-4 levels and the air speed switch to 2-3 levels. Hold the hot air gun about 2.5cm above the chip and blow in a spiral pattern until the solder balls underneath the chip are completely melted. Gently lift the entire chip with tweezers.After removing the BGA chip, there will be residual solder on both the chip pads and the PCB. Apply an adequate amount of flux to the PCB, and use an electric soldering iron to remove excess solder from the board. Apply solder to each pad of the PCB to ensure a smooth and rounded surface. Be careful when desoldering to avoid scraping off the green paint on the pads or causing pad detachment. Prepare for rework. It is advisable not to remove the solder on the surface of the removed BGA chip, as long as it is not too large and does not affect the compatibility with the solder paste stencil. If there is excessive solder on a certain area, apply an appropriate amount of flux to the surface of the BGA chip, use an electric soldering iron to remove the excess solder, and then clean it.Fixing the BGA chip: Align the IC with the holes on the solder paste stencil and secure it with adhesive tape. Press the solder paste stencil firmly with your hand or tweezers while holding it in place, then apply solder paste with a spatula. If the solder paste is too thin, blowing it may cause boiling and difficulty in ball formation. Therefore, the drier the solder paste, the better, as long as it is not too hard. If it is too thin, press it with tissue to absorb some. Some solder paste can be placed on the inner cap of the solder paste bottle to air dry naturally. Use a spatula to apply an appropriate amount of solder paste to the solder paste stencil, and press down while scraping to evenly fill the small holes in the stencil.Blowing solder balls: Remove the nozzle of the hot air gun and adjust the air volume and temperature to the appropriate levels. Slowly and evenly heat the solder paste by waving the central part of the air nozzle over the solder paste stencil. When you see individual solder balls forming in some of the small holes of the solder paste stencil, it indicates that the temperature is right. At this point, raise the air nozzle to avoid further temperature rise. Excessive temperature can cause the solder paste to boil violently, resulting in failure of the solder paste. Severe cases may even cause overheating and damage to the BGA chip.If, after blowing solder balls, you find that some solder balls are uneven in size or even some pins are not soldered, you can use a paper knife to trim the exposed parts of the larger solder balls along the surface of the solder paste stencil. Then, use a spatula to fill the smaller holes with solder paste, and then blow again with the hot air gun. If the solder balls are still uneven, repeat the above steps until the ideal state is achieved.Place the BGA with solder balls back onto the PCB in the same position as before disassembly. At the same time, use your hand or tweezers to move the chip back and forth and gently apply pressure. You can feel the contact situation of the pins on both sides because both sides of the pins are round. If you align them, after alignment, because a little flux is applied to the pins of the BGA in advance, it has a certain stickiness, and the BGA will not move. After positioning, you can proceed with soldering.Similar to when placing solder balls, remove the nozzle of the hot air gun and adjust it to the appropriate air volume and temperature. Slowly heat the central part of the air nozzle over the central position, and the surrounding flux will overflow. This indicates that the solder balls have fused with the solder joints on the PCB. At this point, gently shake the hot air gun to evenly heat it. Due to the surface tension, the BGA will automatically align with the solder joints on the PCB. Be careful not to press too hard during heating, as this may cause solder overflow and potential pin loss and short circuits. After soldering is complete, wash the board with deionized water.
