Many beginners in phone repair consider solder balling complex, but it is actually a core skill for solving many chip-related faults. Though this article, Phonefix breaks down the whole process of solder balling, covering basics understanding, tool preparation, step-by-step operation mastery, mid-layer techniques and answers to common stencil usage questions, all to help you confidently start solder balling.
I. Understanding and Application of Solder Balling
Solder balling repairs or reinstalls chips like CPUs and mid-layer chips by recreating uniform solder balls to restore electrical connections to the phone motherboard. It’s used in two common situations:
1. Chip Faults Requiring Removal and Repair:
When a chip, such as the CPU or power chip, is damaged, it must be solder-balled before being reinstalled on the motherboard after repair.
2. Faults Due to Solder Joint Issues:
When issues like no signal or frequent phone restarts occur due to poorly soldered mid-layer chips, removing the chip and performing solder balling can repair the solder joints and solve the fault.
II. Tools and Steps for Solder Balling
Mastering the use of tools and the operation process can greatly reduce the error rate.
1. Tool Preparation
Beginners do not need complex equipment; there are only 4 core tools, which are cost-effective and easy to obtain:
- Hot air gun: Choose an ordinary repair YCS Hot Air Gun with adjustable temperature and air flow.
- Steel mesh: It must match the chip model. A steel mesh with precise hole positions can ensure uniform solder scraping and avoid solder ball deviation.
- Tweezers: Tweezers are crucial for positioning small components in solder balling, ensuring precise alignment and stability during heating.
2. Key Steps and Tool Usage
Successful solder balling depends not only on technique but also on the proper selection and use of fundamental tools. Each tool plays a critical role in ensuring precision and consistency throughout the process. To achieve the best results, carefully follow these steps in sequence:
Step 1. Prepare solder paste with paper towels
Use a dry paper towel to absorb excess moisture from the solder paste surface, ensuring proper consistency to prevent uneven spreading and solder ball merging during heating. Then fold 3-4 paper towels into a thick cushion placed on the workbench, creating a flexible support surface that minimizes chip bending and uneven pressure.
Step 2. Position the chip and steel mesh
Place the chip with its solder pads facing down onto the paper towel cushion. Carefully align the steel mesh over the chip, making sure all holes match the soldering pads exactly.
Step 3. Secure the setup with tweezers
Use Precision Tweezers to apply gentle pressure to the center of the steel mesh, creating a slight dip. The paper towel cushion supports the edges, which helps minimize warping of the mesh as it expands under heat.
Step 4. Heat evenly with the hot air gun
Set the hot air gun to 280-300°C with the airflow at 50%. Start heating from the top-left area of the steel mesh, moving slowly toward the right until the solder paste in every hole melts completely. After all solder balls have formed, allow 10 seconds for cooling before carefully removing the steel mesh.
III. Method for Mid-Layer Solder Balling
Compared with basic solder balling, mid-layer chips are larger in size and have more solder joints, making solder balling more difficult.
1. Alternative Without Dedicated Table
If you do not have a mid-layer solder balling table, you can use a four-magnet base for assistance. The steps are as follows:
Step 1: Lay paper towels: Place 2-3 stacked thick paper towels on the Magnetic Base to play a buffering and auxiliary fixing role.
Step 2: Scrape solder and heat: Place the mid-layer chip on paper towels, cover with the steel mesh, and use magnetic force to fix it in place during solder scraping.
2. Solder Paste Selection
The selection of solder paste should be based on the motherboard design. Beginners should prioritize types that are easy to operate:
- Low Temperature Solder Paste: If the motherboard is designed for low humidity, low-temperature solder paste should be used first. It has a low melting point, so it is not easy to damage the chip during heating, reducing the difficulty of repair.
- Medium temperature solder paste: If the motherboard is designed for medium or high humidity, it is recommended to use medium-temperature solder paste. The mid-layer solder balling area is large and heat dissipation is fast; medium-temperature solder paste can ensure firm solder joints and reduce rework.
IV. Common Problems with Steel Mesh
In solder balling, the BGA Reballing Stencil is essential. It’s a metal template with precise holes that fits the chip surface, allowing solder paste to evenly cover the joints and form standard solder balls. Here are answers to common questions beginners have when purchasing and using stencils:
1. Received Steel Mesh Does Not Match the Picture
If the received steel mesh does not match the product picture, it is not a wrong delivery, but because the steel mesh has been upgraded:
- Reason for upgrade: Early steel meshes may only cover a few chip models, and later more chip models will be added.
- Impact on use: The upgraded steel mesh retains the original chip positions, with only the layout changed, offering better performance without affecting normal use.
2. How to Customize a Mesh for New Phone Models
For newly launched mobile phone models that do not have ready-made steel meshes, free customization is available:
- Customization process: Send the physical new mobile phone to the manufacturer to facilitate board copying and design by the manufacturer; the manufacturer will customize the steel mesh according to the physical product.
3. Methods for Finding Steel Meshes
Beginners do not need to search blindly for steel meshes; you can quickly locate them using this method:
- Search by mobile phone brand: When the mobile phone model is known, directly search for the corresponding model in the "Mobile Phone Brand Classification Steel Meshes" category. This operation is simple and straightforward.
Conclusion
For beginners, mastering solder balling relies less on memorizing techniques and more on hands-on practice. With consistent practice, you will soon master this essential repair technique. For more resources on mobile phone repair or to explore professional tools, visit the official China Phonefix website.
