A method attaches a liquid-repellent filter to an air vent of a resin molded article accommodating a component/electronic part. A thermal processing tip and a thermally welding tip and a molded article are provided. The thermal processing tip (22) forms a filter attachment surface (14) at the inlet or outlet of an air vent (16) in a thermoplastic resin molded article (13). A filter fixing rib (15) is formed around the attachment surface. The porous filter (18) is dropped onto the filter attachment surface, and a thermal welding tip (2) is used to melt the filter fixing rib such that the melted resin flows onto and covers a circumferential edge portion of the filter, penetrating the body of the filter. The melted resin penetrating the filter 18 and covering the circumferential edge portion of the filter are cooled to solid, whereby the filter is fixed to the filter attachment surface.

A method attaches a liquid-repellent filter to an air vent of a resin molded article accommodating a component/electronic part. A thermal processing tip and a thermally welding tip and a molded article are provided. The thermal processing tip (22) forms a filter attachment surface (14) at the inlet or outlet of an air vent (16) in a thermoplastic resin molded article (13). A filter fixing rib (15) is formed around the attachment surface. The porous filter (18) is dropped onto the filter attachment surface, and a thermal welding tip (2) is used to melt the filter fixing rib such that the melted resin flows onto and covers a circumferential edge portion of the filter, penetrating the body of the filter. The melted resin penetrating the filter 18 and covering the circumferential edge portion of the filter are cooled to solid, whereby the filter is fixed to the filter attachment surface.