Joint Formation
Surface mount technology utilizes spherical solder leads positioned on the underside of a package to establish electrical and mechanical connections. Bga assembly involves the placement of components onto solder paste deposits followed by a controlled reflow cycle. The process manages the simultaneous melting of hundreds of individual connections within a confined footprint.
Thermal Profile
Precise control of the temperature ramp rate prevents the internal substrate from warping during the heating phase. Uniform heat distribution across the array ensures that every ball reaches the liquidus state at the same time. Excessive dwell time above the melting point leads to brittle intermetallic layers or solder bridging between adjacent pads.
The cooling phase is equally important for establishing a fine grain structure that can withstand mechanical stress and thermal cycling during the life of the electronic product. Controlled cooling prevents internal stresses from cracking the joints.
Inspection Protocol
Automated X-ray systems verify the integrity of the hidden solder joints after the reflow is complete. Voids or misalignment are identified by scanning through the package body to view the density of the metallic bonds. Corrective actions for defects usually require the removal of the entire component using specialized rework stations.
