A printed circuit board 130 has a heating element 138 printed on at least part of its edge. Different boards can have elements generating different temperatures from the same voltage or current. The element can be positioned in the guide path of a film-closure apparatus 10 which has drive means 12 for moving the film material along the guide path 14. The heating element can include four spaced parallel exposed conductors extending along the edge. The element could extend all the way along a longitudinal edge of a rectangular PCB. The heating element could protrude from the edge. The circuit substrate could be polyimide and the heating element can be copper. The heating element can project from a casing 20 which includes sprung terminals to electrically connect the PCB to a power source. There can be two heating elements projecting towards each other from cases on opposite sides of the guide paths. The PCB can include a screw hole for mounting. A printed resistance track can be configured to give a desired resistance and a thermistor to regulate temperature.
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