To implement and control the production of surface-mount assemblies, the dynamics of the solder reflow process and how each element of the process is related to the end result must be thoroughly understood.
The primary phases of the 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, Xilinx 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.