Know More About BGA Rework Process

BGAs have become one of the most prevalent package types for active devices. They have a variety of benefits to the user including increasing the density of interconnections vis-à-vis leaded devices saving as much as 40% in real estate compared to other leaded devices. In addition, their design is more robust meaning there are fewer damaged devices in the assembly and handling process for these devices. Leaded devices tend to get damaged, especially as their pitches approach 0.4mm on center. A recent survey says that the increased use of BGAs and the underlying trend of ever-smaller package sizes, finer pitches, and their placement on to ever denser printed circuit boards have led to greater and greater challenges in BGA rework. In addition, BGAs have matured enough to where they are simple to place and reflow with tin-lead versions being "self-centering" during the reflow process. BGAs also enjoy high-speed operation as the capacitive coupling from the die to the lead frame is reduced over leaded device package designs.

In the use of BGA devices, the necessity to remove and replace them becomes a necessity in today’s modern PCB assembly process. After determining that the BGA needs to be replaced due to an upgrade in processor speed, misplacement, a defection the device, more memory or a host of other issues, the BGA rework or removal and replacement process needs to begin.

The BGA rework process begins with the identification of the device to be removed of and replaced. In a majority of cases, users will simply remove the older device and replace it with a brand new one in the BGA rework process. A good idea to the start the BGA rework process is to make sure you have the correct part number of the replacement device. Also, make sure that the replacement device has the proper orientation markings and that you understand what that corresponds to on the PCB in terms of the silk screen pattern indicating the orientation of the replacement BGA. Once that is done confirm the alloy of the solder balls in order to dial in the proper reflow profile required to perform the BGA rework process. Next, mount the PCB to the BGA Rework Station selecting the proper nozzle or shutter system depending on whether a hot air or an infrared reflow resource will be used. Begin the reflow process using the removal profile developed given the type of solder alloy, the thermal density of the board and the surrounding components. The BGA rework process then proceeds to the bottom side of the removal location coming up to temperature with the topside area following in and around the area to be reworked. After the reflow temperature is reached and the solder then goes into the liquid phase the device can be removed. The next step in the BGA rework process is to perform the site preparation of the pads of the BGA once the BGA has been removed. Using paste flux, a soldering iron and solder wick the pads can be cleaned in preparation for the replacement BGA. Next, the proper paste flux is brushed onto the pads. The paste flux should be formulated based on the solder reflow temperature as determined by the solder alloy and cleaning chemistry desired. A replacement BGA is then loaded onto the BGA rework system for placement. The placement profile is then run through in order to place the BGA as part of the BGA rework process.

After cleaning the inspection of the replaced BGA is then performed as the next part of the BGA rework process. The BGA rework process can be inspected visually in order to make sure the balls are collapsed. An endoscope is used to inspect the size, shape and flux residue underneath the BGA for proper BGA rework collapse. Lastly x-ray analysis is used to determine if there are any shorts, opens or bridging underneath the device. In some cases, functional or another electrical testing will confirm the proper interconnection of the device to the PCB and make sure that no other areas of the board were disturbed through the BGA Rework process.

I am principal of BEST Inc. I have 18+ years experience in running small businesses. I am a practicing instructor in IPC certification and have a passion for teaching in a variety of life skills as well as in soldering and PCB repair.