Polymeric Material Adhesion and Common Failure Mechanisms in the Assembly of Jettable Fluid Devices
Abstract:The two most common methods of non-contact, jet printing technology in use today are piezo-electric crystal and thermal bubble. In operation, a piezo crystal flexes to push an ink or fluid drop out of the printhead nozzle while the thermal design uses a heating resistor to create a bubble that expands and exits the nozzle. In both designs there is intimate contact between the printhead and media being jetted. Jettable fluid delivery systems and other MEMS devices require reliable assembly of a variety of components. These components can be assembled through the use of molding materials, mechanical fasteners, and structural adhesives. Structural polymeric adhesives are most often the ideal choice because they mate the substrates to form a continuous surface. These bonding surfaces often consist of multi-layer silicon die, thin and thick wall engineered plastics, noble metals, and flexible substrates. The adhesives act as a barrier or seal, preventing the fluids from leaking while also protecting the device from potential environmental contaminates. This paper discusses polymeric material adhesion testing and common failure mechanisms associated with harsh environment fluid jetting. Some standard tests can be used to screen adhesives. One example of a widely used test is lap shear measurement, which can be developed for specific substrates. The test part can be evaluated at various temperatures as well as before and after exposure to a harsh chemical environment. If dissimilar substrates are to be bonded and a lap shear test is not practical, an alternative test can be developed. For example, a plastic and glass substrate bond may always fail with the glass fracturing. In this situation, the adhesive bond strength is not properly measured. Therefore, an alternative test, such as a shear strength push test, must be designed. In this test, a shear force is applied to an edge of a substrate bond, such as a die bonded to plastic. By altering the adhesive bond test, the failure mode will shift from a pull force to a peel force, thereby allowing for better representation of the actual bond strength for a given application.
Document Type: Research Article
Publication date: January 1, 2004
For more than 25 years, NIP has been the leading forum for discussion of advances and new directions in non-impact and digital printing technologies. A comprehensive, industry-wide conference, this meeting includes all aspects of the hardware, materials, software, images, and applications associated with digital printing systems, including drop-on-demand ink jet, wide format ink jet, desktop and continuous ink jet, toner-based electrophotographic printers, production digital printing systems, and thermal printing systems, as well as the engineering capability, optimization, and science involved in these fields.
Since 2005, NIP has been held in conjunction with the Digital Fabrication Conference.
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