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productronica 2025 Advanced Packaging Anzeige To ensure clear optical separation between each die a structure with very low light transmission is required The challenge lies in creating a grid structure in which the lines overlap as invisibly as possible something that has so far been achievable only to a limited extent with conventional dispensing technology New approaches in microdispensing and suitable materials can also help address this challenge By adjusting dispensing speed and volume at line intersections material buildup can be effectively avoided Symbiosis of material and dispensing Given the small scale dispensing technology plays an equally crucial role in the successful formation of microstructures as the material itself Avolumetric system with a pinch valve is used for dispensing microdam adhesives enabling precise fine dispensing of as little as 0 3 nl By eliminating moving parts in the dispensing chamber unwanted material mixing is prevented This is especially important for filled adhesives — such as those containing silver — to avoid material separation particle breakdown and nozzle clogging Moreover it does not require high chamber pressure to dispense the material from the nozzle ensuring a consistent dispensing volume Amaterial stabilizer within the pinch valve also keeps the adhesive temperature permanently constant maintaining stable viscosity characteristics of the material The dispensing head of the microdispensing system is equipped with ultrafine nozzles and microvalves as well as a noncontact dispensing mechanism to prevent substrate damage The dispensing volume can be precisely defined and applied at high speed with consistent accuracy The motion platform in turn ensures correct positioning and movement of the dispensing head Only through precise dynamic motion control can dots or lines be accurately dispensed as it maintains the optimal dispensing gap — typically 30–40 percent of the physical dispensing width or dot size Conducted dispensing and aging tests To test the dispensing accuracy of the fine microstructures a crossline geometry was dispensed among other patterns The dispensing image see Fig 3 shows four lines running in very close proximity to one another similar to the layout of micro LED arrays used in modern automotive headlights and industrial applications The distance between the individual applied lines is less than 250 µm To demonstrate the performance of the cured micro dam materials after aging various tests on aging behavior were carried out in accordance with test standards commonly used in the semiconductor and microelectronics industries e g JEDEC MSL 1 The results of tensile strength elongation at tear and young’s modulus tests show that material aging has only a minimal effect on the mechanical properties ensuring consistently high reliability Even after 1 000 hours at 85 °Cand 85 percent r h the tensile strength remains at 90 MPa and the elongation at tear at 15 percent The modulus increases only slightly after 1 000 hours under the same conditions Even under elevated temperature conditions of 150°Cthe aging tests show strong performance The adhesion behavior after aging also plays a key role in ensuring the longterm stability of the microstructures For the study copper and FR4 were selected as substrate materials as they are common surface materials on which the adhesive must adhere The shear strength measurements performed on copper and FR4 show stable highlevel results with no significant reduction in reliability see Fig 6 ha Delo Hall C1 Booth 755 Fig 6 Shear strength testing using standard test methods Fig 5 Results of modulus testing