Electric resistance heating devices – Heating devices – Radiant heater
Patent
1990-07-18
1991-08-13
Reynolds, Bruce A.
Electric resistance heating devices
Heating devices
Radiant heater
392418, 392419, 219388, 414157, 19880314, 198848, F27B 924
Patent
active
050402366
ABSTRACT:
An open-weave conveyor moves a printed wiring board through a region of radiant energy. The conveyor has a plurality of supporting projections extending from the major surface of the conveyor to minimize engagement between the conveyor and the board, providing at least three projections supporting each board above the open-weave conveyor to eliminate a shadow effect caused by radiation blocked by conveyor strands. Guides move the conveyor along an arcuate path away from the printed wiring board in the radiation region, assuring irradiation of the entire printed wiring board surface. This technique is advantageous for simultaneously irradiating both sides of a board during a dry film solder masking technique. The solder mask is radiated to promote cross-linking of the film polymer. To reduce thermal shock and abrupt temperature rise in the workpiece, the ultraviolet source includes a water envelope to absorb infrared radiation. A series of irradiation devices, one with and one without the aforementioned water envelope, may be utilized. A liquid component utilized in the dry film solder masking tecnique to fill voids and irregularities in the printed wiring board surface irradiated in this manner remains stable, preventing the overlaying film from cracking during a semi-curing step followed by further UV processing which provides a full cure. A lamp regulator permits smooth regultion of radiant energy while eliminating the need to regulate or change capacitors. A sensor monitors the UV lamp output to adjust and maintain the desired radiation operating levels.
REFERENCES:
patent: 3552645 (1971-01-01), Boyd
patent: 3655173 (1972-04-01), Costello
patent: 3744557 (1973-07-01), Costello
patent: 3960081 (1976-06-01), Gustaus et al.
Argus International
Jeffery John A.
Reynolds Bruce A.
Weinstein Louis
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