Method of manufacturing and attaching a coil to an electric circuit using a circuit fixture

A method of manufacturing a coil and attaching the coil to contact points of an electric circuit. One end of a winding filament is brought in a stretched state to a first position in a winding machine, the filament is wound to provide a coil, and the filament after the finished coil is stretched to a second position and cut. The first and second positions are located inwardly of the coil. A circuit fixture carrying an electric circuit at a third position, which corresponds to the first and second positions inwardly of the coil, is caused to collect the wound coil, and the filament ends are welded together at the contact points on the electric circuit. The ends of the winding filament are held firmly at the first and second positions, respectively, by means of a hole with subpressure in the winding machine, and at the third position by means of a hole with subpressure in the circuit fixture.

FIELD OF INVENTION
 The present invention relates to a method of manufacturing a coil and
 attaching the thus manufactured coil to the contact points of an electric
 circuit. The invention also relates to apparatus for carrying out the
 method.
 More specifically, the invention relates to the manufacture of electric
 components of very small dimensions, and in particular components that
 include a coil which is connected to one or more electronic circuits or to
 one or more chips or integrated circuits, printed circuits or like
 electronic elements. Reference to electric circuits in the following will
 be understood to include one or more kinds of the aforesaid elements on
 each mentioning occasion.
 DESCRIPTION OF THE BACKGROUND ART
 Certain problems arise in the manufacture of components of the
 aforedescribed nature. These problems are essentially caused by the very
 small dimensions of the elements concerned and require manufacturing
 precision. Typical dimensions of electronic circuits of the kind in
 question are in the order of 0.9.times.0.9.times.0.4 mm and such a circuit
 will typically weigh 4 mg. The copper filament used in winding the coil
 has a typical diameter of 0.03 mm including insulation.
 In manufacturing such a component, it has earlier been necessary to
 pre-attach, e.g., a chip to a tool and then wind a coil with the aid of a
 so-called flyer with one end of the copper filament affixed to a contact
 point on the chip, and thereafter affix the other end of the copper
 filament across the next contact point and therewith establish contact
 across the whole of the circuit, upon completion of the coil winding
 process. One such method of procedure is described in European Patent
 Specification 0573469.
 A coil that has been manufactured in this traditional manner will have a
 very non-uniform quality, because the filament, or wire, is taken from an
 external source and placed adjacent the bobbin centre, which initially has
 a given shape (thickness), and is wound initially from within and
 outwards. Consequently, fewer layers of copper filament are obtained where
 the first end of the filament has passed in towards the centre of the coil
 and winding has commenced. As a result, the coil will be wider in this
 region in order to obtain the same number of turns. The corresponding side
 of the coil then receives more layers and will thus be thicker.
 An object of the present invention is to make possible the manufacture of a
 coil of greater and more uniform quality, by coiling the filament instead
 of winding the filament with the aid of a flyer, whereby the electronic
 circuit or circuits is/are kept outside the actual coiling procedure. This
 more uniform quality is achieved by placing the filament in the centre
 from the very beginning and then coiling the filament outwards in the
 tool.
 Another object of the invention is to place the chip, etc., in the coil
 centre hole directly, thereby avoiding the need to fold-in the chip
 manually.
 A further object of the invention is to enable copper filament and chip to
 be held in place with the aid of sub-pressure, which has been found to be
 a much simpler and much cheaper solution than the mechanical holders that
 are otherwise usual.
 SUMMARY OF THE INVENTION
 A method of manufacturing a coil and attaching the manufactured coil to the
 contact points of an electric circuit, wherein one end of a winding
 filament is brought in a stretched state to a predetermined first position
 in a winding machine; wherein the winding filament is wound to form a coil
 in the winding machine while maintaining said filament end at said first
 position inwardly of the coil; wherein the end of the winding filament
 after the coil is brought in a stretched state to a predetermined second
 position in the winding machine, also inwardly of the coil, and the
 filament then cut; wherein a circuit fixture or jig coacting with the
 winding machine and having an electric circuit inlaid in a predetermined
 third position that corresponds to said first and said second positions in
 the winding machine is brought into contact with the winding machine to
 collect the wound coil; and wherein the filament ends of the coil are
 finally welded together with the contact points on the electric circuit
 located inwardly of the coil.
 These and other characteristic features of the inventive method and the
 inventive apparatus for carrying out the method will be evident as set
 forth herein.

DETAILED DESCRIPTION OF THE INVENTION
 Apparatus Description
 The invention will now be described in more detail with reference to the
 accompanying drawing which illustrates schematically apparatus for
 carrying out the inventive method.
 The apparatus includes a winding machine 1 and a circuit fixture or jig 2
 which coacts with the winding machine.
 The winding machine 1 includes a rotatable bobbin plate 11 which has in the
 centre thereof a hole 110 for firmly holding filament ends by means of
 subpressure, and also has a slightly raised centre part 115 (about
 0.15-0.35 mm). Provided on the periphery of this centre part, to the left
 in the drawing, are a first pin 113 and a second pin 114 which lie
 relatively close to one another and which are intended as supports for the
 filament ends. The machine also includes a movably arranged bobbin lid 12
 which can be moved towards and away from the bobbin plate 11 and which has
 holes (not shown) corresponding to the pins 113, 114, a filament guiding
 means 13 for guiding the filament 30 during winding of a coil, and
 filament guide 14 for locking the outer filament end of a wound coil to
 the bobbin plate 11, whereas the filament guiding means 13 guides the
 filament transversely across the centre hole 110 to a filament holder 15
 having filament cutting means 151. The bobbin plate 11 has a first
 position 111 and a second position 112 to which one end of the winding
 filament is brought in a stretched state prior to winding the coil, and to
 which the terminal end of the coil is brought in a stretched state
 subsequent to winding the coil. A small recess (groove) is provided in the
 plate at said two positions, between the periphery and the centre, for
 receiving respective filament ends.
 The circuit fixture or jig 2 has a bottom plate 21 which corresponds to the
 bobbin plate 11 and which has a hole 210 in the centre of the plate for
 firmly holding filament ends with the aid of subpressure, corresponding to
 the hole 110 in the bobbin plate, and also has a pre-selected third
 position 231 for firmly holding electric circuit 3 with the contact points
 31, 32, said third position corresponding to said first and said second
 positions on the bobbin plate 11. The plate has a slightly raised centre
 part 215, in whose periphery there is provided a third pin 213 and a
 fourth pin 214 which are seated relatively close together and placed so as
 to take over the function of the pins 113, 114 as filament end support
 means. The positions of these filament ends will herewith be changed
 slightly, although not sufficient to risk the filament ends releasing
 their direct contact with the contact points of the electric circuit. The
 bottom plate 21 is mounted on a rotatable arm 22, which rotates about an
 axis 23. The arm can be rotated through 180.degree. in relation to the
 plate 11, such as to collect a finished coil (with subpressure). The ends
 of the coil will herewith automatically be brought into abutment with the
 contact points on the electric circuit, so that the coil ends and contact
 points can be welded together.
 Method Description
 1. The bobbin lid 12 is open and the filament 30 is stretched over the hole
 110 through the medium of the first pin 113, and is held by the filament
 holder 15.
 2. The filament holder 15 is opened and the filament end is drawn down into
 the hole 110 by suction and the bobbin lid 12 closed.
 3. Coil winding is commenced with the filament end fixed in the hole 110
 and stretched over said first position 111.
 4. Subsequent to having wound the coil, the bobbin lid 12 is opened and the
 filament guide 14 enters and locks the filament end firmly in the outer
 turns of the coil.
 5. The filament guiding means 13 moves to the filament holder 15 with the
 filament which is herewith stretched over the hole 110 through the medium
 of the second pin 114, whereafter the filament cutting means 151 cuts off
 the filament, which is then sucked down into the hole 110.
 6. The filament guide 14 moves to one side and the coil is ready.
 7. The circuit fixture or jig 2 with the inlaid electric circuit 3 is
 rotated counter clockwise through 180.degree. and collects the finished
 coil, wherein filament fixation is effected by means of subpressure in the
 hole 210. The coil and the electric circuit are also fixated with the aid
 of subpressure