BGA repair refers to the repair of physical damage to the BGA package. The package can be in need of repair of its mask if it has been damaged, the solder balls need to be reattached or changed out or pads need to be tinned prior to ball attachment.
When the solder mask on the underside of an area array package needs to be repaired, a mask repair material is used to shore up exposed conductors or repair chipped mask. A mask repair kit along with the right skills (see referenced video below) will allow you to properly repair the underside mask areas of BGAs.
When solder balls need to be re-attached to a an area array device on one or a few devices then there a few process choices you can make to the get BGA or CSP repaired and reballed.
In one of the methods solder balls are selectively attached via a metal stencil whose thickness is approximately 60-70% of the diameter of the solder balls being attached. After fluxing of the underside of the part with a StikNPeel™ stencil the stencil is aligned over the device pads solder balls are then piured onto the stencil and the balls are fitted one ball per hole into the apertures.. Once all of the balls have been pushed through each one of the apertures, the device is reflowed based on the thermal mass of the fixture , the part and the alloy being used.
In another method a reballing preform such as EZReball™ is used to attach the solder balls. After fluxing the bottom of the package pad side up the preform is aligned and placed on to the pads. The preform is “squared up” to the package and then reflowed. After reflow the preform is simply peel off the package.
BGA repair can also include the repair of BGA pads. This can be accomplished using the process as seen on the video below using BGA pad repair materials.
Proper BGA repair techniques also include the proper BGA retinning of pads on the device as seen on the video below.