3 Common BGA Rework Challenges

March 9, 2023
3 common BGA rework challenges

A BGA rework removes and replaces a ball grid array (BGA) device from a printed circuit board (PCB). It is one of the most challenging aspects of PCB assembly and repair. 

BGA components are surface components that have solder balls or pads on their undersides that make electrical contact with the circuit board. These components are designed to be permanently mounted on a PCB, integrating the circuits, which is why removing them during a rework is complicated. 

The rework process typically involves heating the surface mount component until the solder balls or pads melt. The component can be removed, usually done with an infrared reflow oven. After you remove the part, you can apply new solder balls or pads, and a new BGA component can be attached to the circuit board. 

This process is often executed to repair faulty circuit boards or to update those components to include the latest technology. 

What are some of the most common BGA rework challenges, and how can they be overcome?

Before you take on a BGA rework, ensure that you have the right about of scientific knowledge and an eye for detail. Unless you are a skilled technician, it is easy to make common mistakes that can result in unfavourable results like defects. 

The following are some of the biggest challenges that you can face during a BGA rework and some potential solutions to help overcome those challenges:

1. Warped BGAs

One of the most significant challenges of conducting a BGA rework is dealing with the warping of the packages, which tends to occur more and more often as they are designed to be increasingly thinner. 

One of the most common warping issues is known as the "Head in Pillow" solder joint defect, which occurs when the solder paste deposit wets the pad but does not fully wet the ball since the ball of the package is pulled away as the device warps. 

This defect results in a solder joint that lack sufficient mechanical strength, which could lead to components failing after only a tiny amount of mechanical or thermal stress is applied. 

Other common issues stemming from warping are bridging or shorts, which can occur during replacement at the outer corners of the device or the center. If this happens, it can cause the BGA to bow upwards while the corners bow down, or vice versa. 

In some cases, this can cause the corners to move closer to the surface of the circuit board, putting pressure on the corner solder joints and potentially leading to shorts or cracks at some point. 

Fortunately, there are many ways to avoid problems related to warped packagings, such as adjusting the reflow profile and solder paste chemistry, which can help determine which parts of the device will experience thermal stress, ensure the flux activity level does not expire, and ensure there is plenty of flux activity if the warping occurs over a prolonged reflow cycle. 

By controlling these factors, you can minimize distortion during the BGA rework process. Warping can remain minimal by maintaining a minimum temperature differential across the entire BGA package and by using a programmable multi-zone bottom-side heating source.

2. Neighbouring Device Damage

Due to the increasing density of the components on PCBs, it has become increasingly essential to protect neighbouring components that are temperature sensitive, such as ceramic capacitors, crystals, and plastic-bodied components, like connectors. 

Without being protected from the heat during a BGA rework, these components can be damaged in ways that may or may not be immediately noticeable. Their long-term reliability will undoubtedly be impacted negatively. Even though some of these components may technically withstand temperatures up to 260°C, problems can still occur if the IMC layer becomes too thick. 

Fortunately, it is possible to prevent such adverse effects on neighbouring devices through proper thermal shielding. 

However, historically common shielding methods, such as Kapton™ tape and stainless steel, are less effective than more modern materials, like shielding clay gel. Ceramic nonwoven fibre material is also nearly as effective. 

It does not have to be cleaned off after use, so it may be preferential due to its ease of use. 

3. Underfill Rework

 In most cases, the underfill's softening point is less than that of the PCB's reflow temperature, so under the BGA and any unprotected devices, the underfill softens and expands before the solder reaches a liquidus state. This makes removing the device challenging since the underfill will squirt out as local pressure pushes out the solder once it reaches its reflow temperature, creating a mess around the underfilled device that requires reworking. 

In addition, the necessary mechanical force applied by a lever arm or specialty nozzle to remove the underfilled device could cause extensive damage to the PCB. The solder wick or nozzle could also scratch or damage the solder mask's pads as the remnant underfill is removed. 

If the tack adhesive strength of the underfills is strong enough, it may result in the pads being pulled right off the board. 

You can avoid extensive damage if you implement a high-speed milling system. As such, a system will grind off the cured underfill material and remnant solder balls rather than applying direct heat. 

However, it is crucial that extreme precision is exercised if this method is chosen, as not grinding far enough will result in too much underfill being left at the BGA device location, making it impossible to solder the pads. 

It is essential to ensure that the mechanical vibration and the stress of the rework do not impact the PCB's reliability in any way. 

How Circuits Central Can Help You Overcome Any BGA Rework Challenges

Whether your BGA has been overused, your device contains faulty components, or has weak solder joints; Circuits Central can help simplify your BGA rework in Waterloo

Although BGA repair and reworks are often necessary, many complications can arise when tackling this complicated task without the right tools and expertise. At Circuits Central, we apply industry-proven methods and tools for BGA reworking, and through extensive research, we have established a unique technique for cost-effective and reliable re-balling. 

You can be confident in us. We always get the job done right the first time since our team is full of experienced professionals with plenty of knowledge in this field. We also always take the time to discuss your concerns to ensure our solutions will meet your specific requirements. We will get your BGA reworking and re-balling done promptly and efficiently to guarantee your satisfaction. 

For more information about our BGA repair and rework services or to learn more about some of the other PCB-related services we offer, call Circuits Central at 1 (888) 602-7264 or email us at info@circuits-central.com.

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