BGA Rework Process: A Complete Overview

The BGA rework process requires extreme care and precision. This post takes you through the rework steps, from removing the chip to reinstalling or replacing it. We also point out the mistakes to avoid, especially if you must re-ball the package.

Key Takeaways

• When Rework is Necessary: To correct assembly defects and for BGA upgrades.
• What You Need: A rework station or hand soldering and desoldering tools and materials.
• More than Just Equipment: The rework process requires expert knowledge to avoid causing damage and other mistakes.
• What Not to Do: Avoid using excessive force, too much heat, and actions that could damage adjacent components.

What is BGA Rework?

BGA rework is the process of removing and replacing a faulty ball grid array IC package on a PCB. You may either re-ball the package for reuse or install a new one in its place.

We primarily rework BGAs to correct manufacturing errors, such as alignment and soldering defects. You can also replace the chip to upgrade to a more suitable version.

A BGA has many solder spheres arranged close together on its underside. The spheres also remain hidden beneath the package, making it challenging to work with.

The process, therefore, demands extreme care to make it error-free. Its removal and replacement steps also require specialized equipment and tools, as we explain below.  

BGA Rework Equipment

BGA rework is either manual or semi-automated. A manual process requires a hot-air station, a hot-air gun, and component-pickup tools, such as tweezers. You also need solder, solder paste, and flux.

Other necessary materials and tools include a soldering braid/wick (or vacuum extractor), solder balls (if you intend to reuse the package), magnification tools, and inspection equipment.

Professional rework requires a specialized machine. This device uses advanced technology to remove, solder, and inspect the package. The typical BGA rework station has these main features.

• A workspace or platform.
• Upper and lower movable spot heaters.
• An optical vision and alignment system.
• A reflow soldering station.

A BGA creates hidden joints that you cannot see using conventional inspection methods, such as visual and optical techniques. You need an X-ray device to visualize the assembly and identify defects.

BGA Rework Process

Understanding the correct process steps is essential to avoid costly mistakes. Here is a step-by-step guide to removing and replacing a defective BGA package using a rework station.

Board Preparation

• Bake the PCB typically at 105°C to 125°C for 4 to 24 hours depending on board thickness to remove moisture and prevent delamination.
• Clean the circuit board with isopropyl alcohol to remove contaminants.
• Apply soldering flux around the package to prepare it for heating.
• Place the PCB on the rework station.

BGA Removal

• Apply the appropriate thermal profile to melt the existing solder joints so the package can be safely detached.
• Next, lower the top heater and position it directly above the BGA.
• Heat it at around 250°C for up to 40 seconds.
• Raise the heater and remove the BGA using a removal tool or vacuum nozzle.

Site Cleaning

• Use solder flux and solder wick/braid to clean the exposed pads on the PCB.
• Examine the pads for any damage using a microscope.
• Clean the pads with isopropyl alcohol to remove flux residuals.

Reballing (Optional)

• Apply a thin layer of tacky flux (or print solder paste) to the removed BGA if you intend to reuse it.
• Carefully place solid solder balls onto the flux-covered pads using a reballing stencil.
• Reflow the balls using a specific thermal profile to ensure a reliable metallurgical bond between the balls and the BGA pads.

BGA Replacement

• Position the BGA above the installation site and ensure proper alignment.
• Gently lower the BGA onto the site where solder paste or flux has been pre-applied to the pads.
• Professional stations come with automated optical alignment systems.

Reflow Soldering

• Apply a reflow temperature of up to 250°C to melt the solder balls.
• Maintain the heat until the reflow process is complete.
• Cool the PCB before proceeding to the next step.

Inspection and Testing

• Use visual inspection to examine the assembly for any visible defects.
• Use X-ray imaging to inspect joints that visual or optical inspection could not reach.
• Conduct electrical tests to ensure the package and PCB assembly meet functionality requirements.
• Perform any other required tests and record all findings for future reference.

Common BGA Rework Challenges

Removing and replacing a ball grid array (BGA) package may sound easy. However, it is complex given its dense array of solder balls and their location on the chip. The challenges include those listed below.

Alignment Problems

The ball grid array is a high-density IC package. It uses tiny solder spheres to form joints with corresponding pads on a printed circuit board. The dense network of these solder balls makes the package more prone to alignment problems.

Heat Distribution

The heat should be even when desoldering or replacing the package. Applying flux before heating the part helps control heat. It’s also crucial to heat the PCB from both sides (above and below).

Thermal Stress

Soldering and desoldering heat may damage the PCB, BGA, and other delicate SMT components. Ensure the soldering temperature is within safe limits to prevent thermal problems, such as warping.

Around 240°C-255°C is ideal for lead-free solder, while 210°C-230°C is suitable for leaded solder. Preheating the board before reflow and covering nearby delicate components also helps.

Mistakes to Avoid During BGA Rework

The rework process does not only require specialized equipment. It also needs an expert’s understanding of the process and experience. Here is a list of common mistakes to avoid if you’re starting.

Improper or Insufficient Cleaning: Contaminants affect the soldering process, reducing its efficiency. Ensure all surfaces are clean before applying solder paste and reflowing.

Pad and Trace Damage: Excessive force during BGA removal can damage pads and traces. A vacuum tool is safer than hand tools.

Insufficient Solder Paste: It affects the flow of solder and wetting. Ensure the amount is adequate without overdoing it, as excess paste causes solder bridging and short circuits.

Too Much Flux: Excessive soldering flux can leave residues and cause the BGA to ‘float’ or shift during reflow. Use it in precise amounts. The flux should also be of high quality.

Improper Reflow Profiling: Ensure reflow temperatures are accurate for the package and solder. A ramp-up temperature of 3°C every second is appropriate.

Not Shielding Other Components: Nearby components may heat up during package removal and replacement. Prevent that by shielding them with appropriate materials. Avoid touching them when removing the package.

Manually Reworking Fine-Pitch BGAs: High-density packages with pitches of less than 0.5 mm require advanced machines with optical alignment systems and computerized reflow control. Attempting manual rework may lead to defects.

Conclusion

The BGA rework process is a demanding task that requires proper training and specialized rework tools. As explained in this guide, the procedure involves removing and replacing a faulty package. It can also be an upgrade to improve a PCB’s performance.

Jamindo is your go-to PCB manufacturer for BGA PCBs. In addition to ensuring precision, we use state-of-the-art equipment to assemble and inspect surface-mount components. Choose us for your next project and experience the benefits of reliable and durable PCB assemblies.