parts rework
BGA Removal Using Focused IR
By concentrating heat onto the part, the BGA avoids excessive temperature. by Vardaan Monga
Recently, a customer asked if we could remove a valuable BGA from an existing circuit card assembly. About 1,000 of these BGAs could be removed. Our customer is a reclamation company, and they planned to resell the BGAs, which could fetch upwards of $400 each because of the current chip shortage.

The BGA itself is an older version of the Intel Altera family of products (FIGURE 1). While deemed obsolete by the manufacturer, the part is certainly usable, and due to the chip shortage, our customer might understandably obtain a good price for these older parts, which can be used as replacements for newer models.

Using a BGA rework station, a focused infrared (IR) model, we first created a thermal profile (FIGURE 2) for removing the BGA that would heat it to below its maximum rated temperature; the upper limit for the part is typically 250° to 270°C. The rework cycle brings the part up to 220° to 225°C, melting the solder connecting the BGA to the circuit board, and permitting the BGA to be lifted off easily without pulling or damaging the solderable pads on the board. Once all the BGAs are removed, they are reballed and packaged for resale.

The thermal profile we developed for our IR rework machine is similar to the profile used to attach BGAs in an IR production oven. We ensure the part does not go above the maximum allowable temperature (250° to 270°C). The IR rework machine concentrates heat onto the part itself and, in our opinion, is more effective for BGA rework than a hot air-based system. We were also concerned the hot air might cause the BGA to exceed its maximum allowable temperature and thus damage it.

reclaimed Intel Altera BGA
Figure 1. Reclaimed BGAs like this Intel Altera are selling for up to $400.
screen capture of a reflow profile
Figure 2. A reflow profile similar to the one used to remove the BGA.
The average rework cycle time is three to five minutes per part, considering the size of the BGA and the thickness of the board. Crystal heaters on the bottom of the rework unit preheat the board from below to minimize thermal shock and make it easy to remove/reflow the part using the IR radiation from the top. A regular water-soluble, washable flux is used to facilitate clean removal.

The BGA itself has a shiny metal housing, and we were concerned at first that its reflectivity might be an issue in terms of temperature control and repeatability, but it wasn’t. The reflow unit simply adjusts the energy based on the temperature reading the thermocouple “sees.” In rare cases we can accommodate the issue by applying a special nonreflective tape to the part.

After a BGA is removed, the surfaces are cleaned by wicking away any residual solder. Once cleaned, the BGA is ready to be reballed, packed and shipped to the customer.

Vardaan Monga is an electrical engineer at BSU Inc. (bsuinc.com); vardaan@bsuinc.com.