2Principle of glass frit bonding Using glass glass as a special intermediate layerAdvantages: Hermetic sealing, metallic lead - throughs,narrow bonding frames, and high bonding yield
3Glass Frit MaterialsLow melting point glass which allow reflow in the temperature range 400C- 450CMain components of Ferro FX glass frit pasteRoHS directive constrict the use of lead additves
4Screen Printing Structurd film supported by the mesh Bond frames are structured in silicon and printed with glas frit paste
5Thermal ConditioningOrganics from the binder and te solvents would cause large bubbles in the glass at the process temperature at which the glass compound melt and wet he surfaceThree step thermal preprocess to burn out the primer and to transform the paste into real pre melted glass is essential for higj quality bond
6Thermal Conditioning1) Directly after printing, the glass paste has to be dried and stabillized at 120C. Solvents disappear and the binder is internally crosslinked and stabillized2) Binder is burned out at 360C. Glass is not melted but viscosity is reduced. Complete burn out takes 10 min.3) The glass particles are completely melt and fuse into glass at 450C. Filler particles are enclosed in the glass but not fused into it.
7Wafer Bond Process The bonding process, which is, from the physics, driven by temperature, has to be supported by mechanical pressureon the wafers, in order to compensate for wafer bow influences and screenprinting inhomogeneities