Bead filter for electromagnetic interference redn., for automation - comprises epoxy coating with aluminium@ and silicon@ for high impedance, mechanical strength, uniformity, and signal=to=noise ratio on PCB

摘要

Filter comprises a hollow (5) ferrite core (3) contg. an arched (8) connecting wire (7) on which a coating of epoxy resin (P) is used to bond the core and wire. The epoxy powder for coating pref. comprises (SIC) essentially Al and Si, esp. 47wt.% Al, 48wt.% Si, 5wt.% Cl, Ag, Sb, Ti, Fe and Co. Mfr. comprises (a) bending the wire (7) and assembling with ferrite core (3) to form a prefilter (1'), (b) heat-sealing (13) the prefilter to a paper tape (11) with holes (15) for indexing and conveying (upside down), (c) heating (31) the arched portion (8) of the wire (to 380 deg.C), (d) coating the wire portion (8) and top of the core (3) with epoxy powder (P), carried from a fluidised bed (27) on a coating wheel (28), which melts on the prefilter, (e) repeating (c) and (d), (three times), and with prefilter redn. to 335-340 deg.C, to ensure bonding between wire and core and a uniform coating, (f) rolling up the (tape (11) and) coated prefilters on a spool, and (g) curing the epoxy resin to form the bead filter (1), specified as '45-50 mins. at 150 deg.C in oven to raise mechanical strength'. USE/ADVANTAGE - Filter can be recovered to the prefilter condition by treatment with chemical solvent.