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Abstract

A stereolithographic (STL) apparatus for forming structures such as semiconductor die packages is described which uses a laser beam focused to a generally annular 'spot' having an annulus of enhanced laser power surrounding a central 'hole' of reduced (or no) laser power. The structures are formed of a stack of light-polymerized photopolymer layers. Scanning of a beam having power concentrated in the annulus enables simultaneous production of a self-supporting structure having at least semisolid, smooth lateral outer polymer walls and an upper hardened polymer skin extending over liquid polymer still lying between the walls. The structure may be subjected to heat or broad source light of suitable wavelength after removal from the STL apparatus to accelerate complete polymerization of the structure to a solid state.

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First Claim