BGA Rework: A Comprehensive Guide to Repairing Ball Grid Arrays

Four major tasks, in particular, are included within the BGA rework process starting with heating the board and removal of BGA. After that, the board is cleaned and a new component is attached.

Whether you become successful with BGA rework depends heavily on how good you are at controlling heat and cleaning.

What Tools Are Needed for BGA Rework?

For BGA rework, you will require the following tools:

Wrist strap
Isopropyl alcohol
Liquid flux
Heating nozzle
Solder wick
Solder paste
Mini stencil
Tweezers
X-ray machine

What is the BGA Rework Process?

The simple steps in the BGA rework process are:

Step 1: Preparing the Site for Rework

You must prepare the site before removing it. The site preparation tasks include the following:

Use station grounded wrist strap to ensure safe condition in site.
Using isopropyl alcohol, thoroughly clean the board’s BGA area.
Around the BGA perimeter, apply the liquid flux. During the reflow, it will aid in the heat transfer process.
On the BGA rework station, secure a board and calibrate optics.

Step 2: BGA Removal

You can heat the BGA and remove it by applying the flux. To remove the BGA, do the following:

Place a preheating nozzle under the board, centered below the BGA.
To gently warm the board, set the preheater to 150°C and heat it for one to two minutes.
The top IR heating nozzle should be positioned 1 mm from the surface, directly above the BGA.
Set the upper heating element to 350°C.
To blast the BGA region with infrared heat, turn on the top nozzle. Pay attention to the temperature.
For reflow, keep heating the solder as long it has not reached about 240°C – 260°C.
To guarantee that the solder completely liquefies, keep the reflow temperature at that level for 30–45 seconds.
Using a pick tool, carefully slide the BGA from its site after lifting the top nozzle.
To prevent harming the pads, heat and remove them gradually.
Make sure the residual solder remains on the pads after removing the BGA.

Step 3: Site Cleaning for Rework

Prior to reworking, the site must be thoroughly cleaned once the BGA is removed:

To get rid of all solder residue from the pads, use a solder wick filled with flux.
To be sure there is no lifting or damage, examine the pads under a microscope.
Use a soldering iron set to 350°C to gently rewet any pads that have been lifted.
For a clean surface, use isopropyl alcohol to remove any leftover flux.

Step 4: Replacing Solder Balls

Replace solder balls on the BGA pads for reassembly in the following ways:

Use tiny amounts of solder paste to center part of the pads with a dispenser or stencil.
Using tweezers, following the ball layout pattern, place a new solder ball on each paste spot.
Make sure the solder ball sits properly and doesn’t overlap.
Heat the site to 150°C. Use a heating nozzle to secure the balls in their proper place so that they don’t cause a reflow.

Step 5: New BGA Alignment & Installations

Now, you can align and solder the new BGA onto the board in the following ways:

Place the BGA above the site with a pick tool. Make sure it fits perfectly with fiducials.
Bring down the BGA onto the pads. Apply slight downward pressure to make it touch the self-center point.
You can use a microscope to check if the solder balls are touching the solder paste on the pads properly.
Put flux around the edges to ensure solder flow.
Use a heating nozzle to reflow the solder while maintaining a thermal profile that peaks at 250°C.
Consistently heat the solder until it is fully bonded to the pads.
Wait for the assembly to cool down.

Step 6: Joint Quality Inspection

Examine the BGA joints after the replacement to verify quality:

Inspect the outer joints visually to confirm proper fillet formation.
Use an x-ray machine to check the hidden solder joints beneath the BGA.
Ensure all joints are fully formed with no shorts or open connections.
Capture high-magnification images to document the rework process if needed.

Step 7: Testing

Perform functional testing on the board to confirm successful rework:

Run in-circuit tests if testing fixtures are available.
Power up the system and check functionality under normal operation.
Execute self-tests, diagnostics, or functional test routines on the board.
Retest and verify any previously out-of-spec parameters.
Record all electrical test results for documentation.

BGA Rework Mistakes You Must Avoid

The common mistakes to avoid in BGA rework are:

1. Inadequate Preparation

Whether you become successful or not depends on how well you are prepared for it.

Before touching the BGA, you should make enough preparations.

First, check out the size of the solder ball. Check out the coplanarity of the solder balls and the device. Think and pick your solder paste type, stencil, and alloys.

2. Wrong Equipment Selection

When you are handling BGA rework, you must have the right tools. You should pick equipment that is durable enough to perform repetitive tasks. Using high-quality tools will minimize the risk of reworks. Cutting corners in equipment can cause more problems.

3. Lack of Operator Training

A proper training is required to become a BGA technician. A solid understanding of how different materials work together and how different tools work is highly important. You should also have a solid knowledge of when to start the BGA repair process and the steps you will take ahead.

4. BGA Rework Profile’s Poor Development

An accurate thermal profile is recommended for BGA reworks.

You will need a lot less time and effort with a thermal profile in place.

If your thermal profile is inaccurate it will increase the risk of damaging the BGA and PCB components.

The thermocouple must be installed on the PCB for the creation of the thermal profile. Finally, go through the data you receive from the sensors.

Nozzle and TC1 Profiles During Typical Hot Air Real BGA Rework

5. Collateral Heat Damage

Collateral damage occurs if you do the thermal profiling incorrectly. The damage will create more issues afterward based on the level of intensity.

You should apply heat cautiously. Make sure it is at the correct level all the time. An optimal temperature for one component can damage another component. That’s why having the right thermal profile is important to reduce heat migration.

6. Insufficient Post-Placement Inspection

BGA components are intricate. And you must inspect them to ensure defect-free solder connections. You can prevent failures if you inspect beforehand.

However, technicians rely on three main inspection methods to achieve this:

Optical Inspection: You can use endoscopes to see tiny defects that you won’t be able to see with the naked eye.
Electrical Testing: It tests BGA stability with electric current.
X-ray Imaging: Advanced X-ray tools are used to get a thorough picture of solder joint patterns.

During inspections, wrongly oriented BGA is found to be one of the most common issues. Failing to ensure accurate positioning can cause heat damage.

7. Poor Setup of BGA Rework Stations

You must have a proper for successful BGA rework. A well-equipped rework station should include essential tools like:

Supplementary electronics
Specialized software
A pressure-adjustable suction tool
Cameras
An adjustable X-Y table
A split-beam prism alignment system
A temperature-controlled system.

PCBs of different sizes can be handled using these tools. But you will have to maintain them properly to avoid breakdowns.

8. Extreme Solder Joint Voiding

It will occur if the right solder paste is not selected. Attachments become weakened due to these issues and you will burdened with more reworks.

Why is BGA Rework Tough?

Although BGA comes with high circuit density, their hidden solder joints and fine pitch make reworking defective components extremely challenging.

However, their hidden solder joints and fine pitch make reworking defective components difficult. BGA rework can be tough for the following reasons:

Solder Inaccessibility: Solder joints are located beneath the package. Thus, they are unreachable for direct access.
Small Pads/Balls: Tight spacing between pads reduces the precision of heat application.
Thermal Mass: Large BGAs absorb heat, slowing down the melting process.
Collapse During Reflow: If the solder liquefies the components can loosen and collapse
Warping Stress: Boards may get cracks due to uneven thermal expansion.
Precision Alignment: Extreme level of precision is required for the right placements during assembly.
Process Complexity: Adjust the heating correctly for the desired results.

You can easily achieve success in BGA reworks. With the right tools and experience.

Frequently Asked Questions

What is the Use of a BGA Rework Station?

A BGA rework station replaces, repairs, or removes the BGA components from PCBs (Printed Circuit Boards).

How Many Times Can a BGA Be Reworked?

Usually, a BGA can be reworked one to two times. However, with each rework cycle, the reliability of the BGA components decreases.

What is the Minimum Spacing for BGA?

0.4mm is the minimum spacing line for BGA, and 0.5mm is the conventional spacing line.

How Can I Validate Successful BGA Rework?

The first thing that you need to do is inspect the joints yourself. You can use an X-ray too for the inspection. Also, you need to check for pad alignment. Finally, run diagnostics and functional tests before powering up the board.

Final Thoughts

The BGA rework process isn’t easy. But if you get the proper training, you can slowly become an experienced BGA rework technician. And with the right tools and processes in place, you can continue to rework BGA perfectly.