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Lecture Hall B2 Innovation Forum
13:00-13:30 h | Hall B2 Innovation Forum, B2, booth 441
Subjects: PCB and circuit-carrier manufacturingSpeaker: Sunny Agarwal (ITW EAE)
Underfill materials generally vary in viscosity and filler types, therefore the board heat requirement also varies. The capillary underfill process consists of dispensing a void-free fluid to encapsulate the bottom side of a silicon die or BGA device. It is critical that the gap between the die and the substrate is completely filled with underfill material, as the life of the chip assembly is dependent on it. To ensure that the material flows correctly, the substrate needs to be uniformly heated for flow capillary action to come into effect which also depends upon the underfill flow properties. If the board temperature is too low the capillary flow rate reduces, and the device may not be fully underfilled. If the temperature is too high, then the viscosity may increase again impacting the capillary flow resulting to long flow time or incomplete filling. Either scenario offers the possibility of quality issues and subsequent yield loss.
To overcome these challenges, PCB temperature monitoring is performed through Infrared Temperature Sensors which measures “real time” top-side board temperature which allows the system to provide closed-loop control to maintain the product within the specified temperature range. Infra-Red sensors can be positioned in a fixed position over a region of interest on the clamped board within the pre and post-heat zones. Dispense zone IR sensor mounted on the movable XY gantry is programmable through the software. Closed-loop process monitoring through each of the process zones: pre-heat, dispense heat and post-heat zone ensures dispenser process stability and yield improvements for underfill applications. Product will only be passed between zones and dispensed if the measured temperature is within the desired range. In short, IR sensors ensure higher quality by improving heat stability during the dispense process.