Component Placement
Positioning of submillimeter surface mount devices requires advanced automated placement systems with high resolution camera alignment. During this manufacturing stage, micro bga assembly demands precise control of stencil printing and component placement to avoid bridging.
Reflow Solder
Solder paste deposition must be monitored closely because the small ball pitches, often below 0.5 millimeters, leave very little margin for error. If paste volumes vary across the array, some joints will lack sufficient solder while adjacent joints may touch during heating. Nitrogen reflow ovens are commonly utilized to prevent oxidation and assist the self alignment of the balls onto the board pads.
This controlled atmosphere improves wetting and ensures that the surface tension of the molten solder centers the component accurately.
Inspection Method
Post solder inspection of these grid arrays is challenging because the connections sit entirely underneath the package body. Automated X-ray systems are therefore deployed to scan through the silicon and substrate layers to check for voids and bridges. If voids exceed twenty five percent of the ball area, the risk of thermal fatigue failure during product use increases.
Underfill materials can be injected below the component to distribute stress and protect the delicate solder joints from mechanical shock. This step is critical for assemblies destined for hand held devices where drop resistance is a primary performance criterion.
