Ball grid array (BGA) reworking typically involves de-soldering and resoldering the chip to remove defective components and mount new ones. However, it’s a complex task, and people can easily make mistakes that could lead to adverse outcomes and wasted time. Here are some of the most common errors people make with BGA rework.
1. Lacking an adequate rework station
Starting rework without the proper equipment significantly raises the risks of problems later. Rework stations typically include a minimum of:
- An X-Y table with adjustments that allow printed circuit board (PCB) manipulation during rework
- A temperature-controlled system to heat the PCB and soldering paste
- A suction tool to pick up the BGA — ideally with a pressure adjuster
- A split-beam prism alignment system to match the BGA with the proper site ON the PCB
- Cameras to help verify process adherence and placement
- Supplementary software and electronics
Discussions of BGA rework stations generally concern either hot air or infrared types. The main difference between the two is how they heat the PCB component. A hot-air station features nozzles of various sizes and pumps that promote warm airflow and distribute heat evenly. In contrast, the infrared stations use lights, ceramic heaters or fixed beams for the necessary warmth. Having the correct equipment for the job creates the required foundation for success.
BGA rework station (Source: Shutterstock)
2. Failing to assess the job before beginning rework
Mistakes also occur when people fail to account for the specific factors that could complicate the rework of a BGA chip. For example, plastic BGAs are particularly susceptible to moisture absorption. People must also check that the components can tolerate the expected heat generated during the BGA reworking.
People should look at the solder ball’s size and coplanarity. Checking for solder mask damage and missing or contaminated pads will also help people prepare properly for the rework.
3. Attempting to do the job without the necessary skills
People interested in BGA reworking can take specialized courses to get the knowledge they need. Learning in a hands-on environment allows students to develop good habits while reducing the likelihood of major future errors.
Ohio’s Lorain County Community College has one such program. The community college is the first to offer an applied bachelor’s in microelectronics manufacturing and opened its hands-on training lab two years ago.
The art of soldering from a design engineer’s perspective
4. Forgetting about rework station upkeep
Experts throughout the manufacturing industry engage in preventive maintenance to reduce the chances of vital machines failing and cutting into profits. The goal is to become aware of abnormalities before they cause disruptions. People engaging in BGA rework can help ensure success by following some best practices for upkeep.
Using a high-quality solder paste is a good starting point. The lower-quality varieties are more likely to have impurities that gradually build up on the solder gun tip. When people touch the soldering iron tip, they should only do so with a soft cloth or sponge. Anything rough, such as sandpaper, could damage the solder. Once someone finishes soldering, they should clean the gun tip, then flood it with high-quality solder before turning off and unplugging the machine.
Finally, people must follow all manufacturer guidance about the specialized components, such as the temperature control and cameras. Staying on top of maintenance on the recommended schedule helps BGA rework efforts proceed without unexpected interruptions.
5. Using the wrong inspection options
After people tackle BGA rework, they must choose the right inspection technique to ensure they get the expected results. For example, electrical tests are not appropriate because they only detect a few defects and cannot pinpoint the locations of those problems.
However, performing a visual inspection with an endoscope allows people to see the outer row of connections between a BGA and PCB. Sometimes, they can even examine some interior rows if the lighting is good enough.
Some manufacturers also make dedicated BGA chip sensors that can detect issues such as scratches, contamination, and missing parts. Choosing a sensor with a dual-head design allows people to see the BGA from two perspectives, helping them catch things they may otherwise miss.
High-quality BGA rework requires care and skill
BGA rework is a challenging but necessary task. It’s impossible to completely remove the risk of unwanted outcomes. However, if people stay aware of these five mistakes, they’re more likely to get the desired results.
About the author
Emily Newton is a technical writer and the editor-in-chief of Revolutionized. She enjoys researching and writing about how technology is changing the industrial sector.