BGA Solder Reballing
Ball grid array, chip scale packages as well as other device packages with solder balls may require the solder reballing process to be performed on the package.
If the area array balled device needs to be removed from the printed circuit board it will need to have “fresh” balls placed back on to the package if the device will be re-used. In this solder reballing process the device, after removal from the PCB will have uneven deposits of solder left on its pads. After cleaning up and inspecting the device the pads need to have the remnant solder removed form them. This process is deballing. Deballing can be accomplished either through the use of a solder excavation machine, a mini way sold soldering fountain or through the use of solder wick and paste flux aided by a soldering iron. After removal of the remnant solder, solder reballing calls for inspection of the devices. Solder balls can now be re-attached using fixtures and loose solder balls, solder preforms or through semi or fully automatic solder ball attachment machines. There is a variety of reflow ability for re-attachment of the solder balls including hot air, infrared, and vapor phase reflow techniques.
Solder reballing also can be used to change the alloy of the solder balls residing on the balled package. This occurs in cases where legacy lead bearing solders are used or in applications where the reliability has not yet been done using a different alloy or in cases where a unique alloy is required. In some cases, the assembly may need to meet regulatory guidelines and the alloy needs to be changed out.
Solder reballing, when done properly, has been shown to not have a detrimental effect on the long-term reliability of the printed circuit board assembly. While each assembly is different the impact of reballing has shown that while growing the IMC of the solder joint, in most all cases studied up to 3 reballing attempts did not negatively impact the reliability of the assembly. The unique nature of each assembly along with the end use operating environment will determine what type of testing will be required to test the impact of solder reballing.
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