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productronica 2025 16 Die offizielle Messezeitung www markttechnik de Advanced Packaging New Frontiers in Semiconductor Packaging Precision Dispensing Unlocks Design Freedom Anew generation of semiconductor packaging technology is redefining the limits of design flexibility and performance By combining innovative materials with stateoftheart microdispensing systems and ultraprecise motion platforms engineers are opening up unprecedented possibilities for electronic and photonic integration The ability to dispense minute material volumes with exceptional accuracy and repeatability is setting new standards in heterogeneous integration and optical packaging This breakthrough enables the creation of virtually unlimited freeform structures with feature widths below 100 µm – paving the way for new package designs Miniaturization in semiconductor and microelectronics packaging is reaching its physical limits New approaches are required to advance heterogeneous integration and optical packaging — such as micro dams ultrafine adhesive structures that can minimize keepout zones or serve as optical barriers At the core of every electronic device are semiconductor chips mounted on PCBs alongside other highperformance components and integrated into final applications To achieve maximum functionality within the smallest possible space the microelectronics industry has long relied on heterogeneous integration in which multiple individually manufactured chips with distinct functions are combined into socalled systeminpackages SiP However as more functional units are integrated and device sizes continue to shrink space on printed circuit boards is becoming increasingly limited At the same time valuable space is often wasted for manufacturing reasons for example through designated keepout zones KOZ These areas typically protect components such as resistors or sensors from the flow of encapsulants and capillary underfills CUF To define the boundaries of the keepout zones flowstop structures are applied which must be as small as possible to minimize the required space Construction of tiny micro dams Apromising solution to this challenge is the use of socalled micro dams microscopically small adhesive structures that act as miniature barriers and can reduce the space required for keepout zones Structures smaller than 100 µm can be achieved with both the adhesive material and dispensing technology playing a decisive role On the material side the formation of micro dams is made possible by specialized adhesives with high surface tension minimal shrinkage and unique flow behavior The latter is reflected for example in the high thixotropy index of 6 6 for these materials The thixotropy index indicates the ratio of an adhesive’s viscosity at two different shear rates This property allows adhesive to be dispensed at speeds of up to 30 mm s or more while maintaining a stable bondline geometry without intermediate curing Dispensing needles with diameters of less than 100 µm are used — roughly equivalent to the thickness of a human hair To build tiny barriers approximately 1 mm high 20 or more ultrafine lines can be applied layer by layer in rapid succession achieving aspect ratios of 5 or greater all without intermediate curing The dispensing of the microstructures is performed wetonwet meaning that all applied bondlines are fully cured in a single step within a few seconds using UV light This significantly shortens the process time compared with conventional methods where each applied layer requires a separate curing step In addition to pure light curing microdam adhesives can also be cured using only heat or through a combined lightandheat process This makes micro dams suitable not only for purely lightcuring applications but also for those where shadowed areas would otherwise prevent full curing Applications beyond flow stops Optical sensing and LEDpackaging In addition to their role as flow stoppers the formation of ultrafine structures also offers advantages in the packaging of optical sensors For example in proximity sensors barriers are applied to prevent signal interference between the transmitter and receiver Until now a limiting factor in placing these two units closer together on the circuit board and thereby enabling smaller housing has been the dispensing technology as conventional methods cannot apply barriers that are narrow enough Athird application area for micro dams is LED packaging For years the density of individual dies in arrays has been increasing Fig 1 Schematic illustration of a micro dam used as a flow stopper The ultrafine structures help reduce keepout zones Images Delo Fig 2 Illustration of a proximity sensor with a micro dam shown in magenta The microstructure prevents signal interference between the transmitter and receiver Fig 3 The dispensing image and corresponding diagram demonstrate that lines can be precisely dispensed at very small intervals Fig 4 Results of tensile strength and elongation at tear testing