To implement and control the production of surface-mount assemblies, the dynamics of the Pb-free solder reflow process and how each element of the process is related to the end result must be thoroughly understood.
RECOMMENDED: AMD recommends that customers qualify their custom PCB assembly processes using package samples.
The primary phases of the Pb-free reflow process are:
• Melting the particles in the solder paste
• Wetting the surfaces to be joined
• Solidifying the solder into a strong metallurgical bond
The peak reflow temperature of a surface-mount component body should not be more than 250°C maximum (260°C for dry rework only) for Pb-free packages and 220°C for eutectic packages, and is package size dependent. For multiple BGAs in a single board and because of surrounding component differences, AMD recommends checking all BGA sites for varying temperatures.
The infrared reflow (IR) process is strongly dependent on equipment and loading. Components might overheat due to lack of thermal constraints. Unbalanced loading can lead to significant temperature variation on the board. These guidelines are intended to assist users in avoiding damage to the components; the actual profile should be determined by those using these guidelines. For complete information on package moisture / reflow classification and package reflow conditions, refer to the Joint IPC/JEDEC Standard J-STD-020C.
IMPORTANT: Following the initial placement and reflow process, devices should not be reflowed more than two additional times and should not be removed from the board. Any additional rework beyond that is likely to cause irreparable damage to the device.