Abstract: The invention provides an improved heat seal structure for electronic devices. A heat seal structure comprises a base of synthetic resin formed integrally with an outwardly extending projection, with a gas vent running through the base and projection, the gas vent being sealed off by melting the projection, the improvement that the gas vent is configured generally in the shape of the letter V or Y bifurcating in the outward direction. In another embodiment, the projection has an annular extension disposed on the outward side of the base and adapted to be melted for a double seal effect. In another version of the structure, heat-sealing is performed with a sealing member or composition interposed in the gas vent. In still further embodiments, heat sealing is performed using a sealing member melting at a temperature below the melting point of the resin forming the base.