The target of this study was to develop a semiconductor SMD lowcost package suitable for an absolute pressure sensor. Key demands werean in-line concept for production (reel to reel) and an `open package'due to micromechanically moveable structures at the sensor surface. ANiPd plated Cu leadframe was chosen, on to which a thermoplastic casewas to be injection moulded. Several high temperature thermoplasticmaterials were investigated. Finally, a polymer was chosen for its goodprocessability, dimensional stability, low impurities in the polymer(e.g. monomeric ingredients) and therefore a chemically clean surface.For die attach, a number of epoxy, silicone, and thermoplastic adhesiveswere checked. The evaluation was made with respect to good adhesion tothe thermoplastic package and to low stress characteristics, due to thestress sensitive chip. The investigation then turned to an appropriateencapsulant for the composition. Eight different encapsulants wereinvestigated until one specific silicone gel was found to be the mostapplicable. Key requirements were a low loss factor (tan δ), goodcreep behaviour and self-degassing behaviour. A two component materialwith fast curing characteristics was selected
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