User Guide To BGA Reballing

There are various reasons that would necessitate a BGA to have to be reballed. After the device is removed from an assembled printed circuit board the solder balls underneath eh area array component such as a BGA. CSP or WLC, will not be suitable for re-attachment. Upon removal some of the remnant solder will be attached to the PCB, some to the device and some solder ball solders may be "co-joined" thereby creating a larger than necessary solder fillet. In addition, there may be cases where the solder ball alloy needs to be changed out. In both of these cases, if the original component needs to be re-used, the component pads will need to be re-dressed, cleaned up and inspected prior to the re-attachment or reballing of the device.

There are a variety of methods available for BGA reballing. These methods are described as generically below:

BGA reballing using a preform.

In cases where one at a time repairs are being accommodated or when up to a few thousand devices to be reballed this method uses a single-use soldering BGA reballing preform. This preform is custom made and it holds the balls into the correct location during the reballing process. Automation may come into play when tens of thousands of devices need to be reballed.

BGA reballing using mechanical fixturing.

This BGA reballing method consists of providing a mechanical means to hold the component body and the solder balls for alignment. The tooling is specific to each device and may consist of a reballing stencil, a flux attachment stencil and a holding fixture for the component body. This method can also be employed when there are massive quantities of balls which need to be attached.

BGA reballing using an automated solder jetting machine

In this approach molten solder is jetted onto the pad location. This solder takes on the minimum surface area shape, which is a sphere. This method is well-suited for low to medium volume of when highly sensitive devices need to be reballed as the entire component is not stressed by a thermal cycle.

Each of these methods has its place depending on the volume of the device requiring reballing. In addition, there are a variety of permutations on these reballing methods depending on the end user operating environment. For example, for high-reliability devices there are numerous tests required as well as more specific inspection criteria required for BGA reballing. For space applications, these methods, the testing and inspection criteria become even more rigorous and specific.

There are numerous resources one can use to further understand the nuances of the re-balling process. The IPC 7721 list 3 different methods as of this writing describing the more manual lower volume methods. In addition, many of the requirements for these methods are outlined in the IPC 7095 area array process document. Further resources include a deeper discussion of these issues at. There are numerous YouTube videos that are a good show and tell including one on cleaning and site prep, one on non-collapsing BGA ball reballing method and one on the most common reballing method of a plastic packaged body using a preform.

Hey, I am Betty Hunt working as course counselor and trainer at Best Inc. You can find more about IPC Certification and its benefits here. If you want experts help, feel free to call us at 847.797.9250 or send an e-mail to info@solder.net.