A filter device having a first housing and a second housing clasping therebetween a filter membrane. The housings are domed or convexly-shaped and have cylindrical hubs. A peripheral flange extends radially away from each of said dome-shaped housings and one of the pheripheral flanges has integrally formed thereon a plurality of ribs of predetermined length laying on a circumference of said one peripheral flange at arcuate locations therearound. The filter membrane is of circular configuration having radial projections extending around the circumference thereof. The ribs fit between the projections so that ultrasonic welding melts the ribs and fuses the two housings together, holding the filter membrane therebetween.
