Method of using ionized air to remove from a coil the electrostatic charges produced by winding of the coil on a core

A manufacturing method for electronic components (1) including a coil (10), in which a distributing device (34), carrying a pay-out reel (24) on which is wound a winding wire (6), places the wire (6) in contiguous regular turns (8) onto a core (2), this method being characterised in that a flux of ionised air is forced to flow onto the coil (10) during manufacturing to remove electrostatic charges produced during the winding of the coil.

BACKGROUND OF THE INVENTION 
The present invention concerns an improved manufacturing method for 
electronic components including a coil. 
Numerous electronic components include a coil formed of a core generally 
made of ferrite around which is coiled a very fine wire, of a diameter of 
the order of a few hundredths of a millimeter. 
A manufacturing method for such circuits is known from WO Patent No. 
91/00603. This method includes a certain number of steps which will be 
described succinctly here with reference to FIG. 1 annexed to the present 
Application. 
An electronic component, designated as a whole by the general numeric 
reference 1, includes a ferrite core 2 which is applied against an 
integrated circuit 4 by means of a mechanical holding device which is not 
shown in FIG. 1. A distributing device carrying a pay-out reel, onto which 
is wound a winding wire 6, is brought into position in order to carry out 
the winding of core 2. The distributing device, moving longitudinally to 
core 2 and in rotation about the latter, allows contiguous turns 8 of wire 
6 to be laid regularly on core 2. After winding a coil 10 onto core 2, 
wire 6 is cut and the distributing device is moved in front of the next 
ferrite core. The free ends 12 and 14 of wire 6 wound onto core 2 are then 
taken up by a suitable device and applied onto contact bumps 16 of 
integrated circuit 4. 
Electronic components having a coil of the type described hereinbefore are 
used in particular in the horological industry and the automobile industry 
where they are used in association with vehicle coded anti-starting 
systems. In this latter case, integrated circuit 4 and the coil 10 
associated therewith which forms a reception antenna are integrated in a 
tube 18 made of glass or a similar material as shown in FIG. 2 annexed to 
the present Application. Tube 18 is initially open at one of its ends, and 
contains a thermosetting epoxy resin 20. After a centrifugation step which 
allows electronic component 1 to be moved to the bottom of tube 18, the 
latter is conventionally sealed by means of a high power laser beam. The 
last step of the method consists in polymerising resin 20 by placing 
sealed tube 18 in a furnace. Tube 18 is then moulded for example into the 
thickness of a handle for an automobile switch key. Integrated circuit 4 
enclosed in tube 18 includes an identification code which is transmitted 
by radio-frequency link to the central electronic control unit of the 
vehicle. After receiving the identification code and checking its 
authenticity, the central unit orders the unlocking of the vehicle 
anti-starting system. 
The above method has advantageously allowed the manufacture of electronic 
components including a coil to be mechanised and automated, thus 
contributing to a significant drop in the cost price of the finished 
coils. It has nonetheless been noted that this new manufacturing method 
was accompanied by significant problems of electrostatic discharge. Turns 
8 of wire 6 are wound onto core 2 at great speed, typically of the order 
of 50,000 revs per minute. During winding of wire 6, turns 8 of coil 10 
rub against each other, which leads to the appearance of electrostatic 
charges at the surface of wire 6. Since the outer covering of wire 6 is 
electrically insulated by means of an insulating lacquer in order to avoid 
creating short circuits between contiguous turns 8, the electrostatic 
charges accumulate in coil 10 and cannot be eliminated. In the last step 
of the method when free ends 12 and 14 of coil 10 are applied onto contact 
bumps 16 of integrated circuit 4, the static electricity is discharged 
abruptly into integrated circuit 4 and destroys it. Observed losses due to 
electrostatic discharge are currently of the order of 20% to 30% of 
integrated circuits 4. 
A manufacturing method for coils for transformers in which a winding wire 
wound onto a pay-out reel is placed in turns on a reel is also known from 
Japanese Patent No. 56 108663. Prior to winding the wire onto the reel, 
the latter is cleaned by means of a flexible brush device, then circulated 
in a cylindrical conduit into which ionised air is injected for the 
purpose of cancelling out the static electricity charges which appear in 
said wire during brushing. This document which can be considered the state 
of the art closest to the present invention thus suggests cancelling out 
the electrostatic charges prior to winding the wire onto the reel, and 
does not raise aforementioned problem of electrostatic discharges. This 
difference with the present invention is explained by the fact that, in 
the Japanese document, the electrostatic charges appear during brushing, 
and it is sought to remove these charges immediately after brushing and 
prior to winding. Moreover, the winding speeds in question within the 
scope of the present invention and in the Japanese document are very 
substantially different. Indeed, in the case of the present invention, the 
winding speed is very high (of the order of 50,000 revs per minute), hence 
significant friction between the turns which generated a large number of 
electrostatic charges which it is sought to remove. Conversely, the 
Japanese Patent concerns coils for transformers whose dimensions are 
significant, and for which the winding speed is lower, so that the winding 
of the wire is not accompanied by the creation of electrostatic charges. 
Consequently, the Japanese Patent suggests at most installing an air 
ionising device upstream of the enclosure in which the coil is 
manufactured, and does neither provide nor suggest any solution to the 
problem solved by the present invention. 
Japanese Patent No. 57 091235, which proposes arranging an air ionising 
device at the centre of a confined manufacturing enclosure, is also known. 
This document concerns the manufacture of plastic tapes which is a distant 
technical field not forming part of the knowledge of those skilled in the 
art of the invention who, in the present case, are electronic component 
manufacturers. Further, in this Japanese document, it is sought simply to 
cancel out the electrostatic charges which appear in the plastic tape on 
exiting the extruder, during the passage of the tape between the shaping 
and driving rollers, in order to avoid attracting dust which could become 
incorporated in the still hot plastic material. The problem raised by the 
invention, namely to seek to remove the electrostatic charges which are 
generated during winding of a wire at a very high speed, is not described, 
nor even suggested. 
SUMMARY OF THE INVENTION 
An object of the present invention is thus to overcome the above problems 
and drawbacks by providing a manufacturing method for coils allowing the 
electrostatic charges which appear during winding of the turns to be 
removed. 
The present invention therefore concerns a manufacturing method for 
electronic components including a coil, in which a distributing device, 
carrying a pay-out reel on which is wound a winding wire, places the wire 
in contiguous regular turns onto a core, this method being characterised 
in that a flux of ionised air is forced to flow onto the coil during 
manufacturing. 
As a result of these features, the present invention provides a 
manufacturing method in which the electrostatic charges which appear 
because of friction of the turns on each other during the winding of a 
wire onto a ferrite core are cancelled out by electric charges of the 
opposite sign originating from the ionised air generated by an air 
ionising device. The wire winding thus becomes electrically neutral, so 
that its free ends can be welded onto the contact bumps of an integrated 
circuit without risking destroying it by electrostatic discharge. 
The present invention also allows the very difficult problem of monitoring 
the electrostatic discharges of a moving device to be resolved. It seems 
difficult to envisage, given the extremely high rotational speed of the 
distributing device carrying the pay-out reel on which the wire is coiled, 
connecting this distributing device to earth by means, for example of an 
electrically conductive wire. As a result of the present invention, it 
becomes possible to monitor the state of electrostatic charge of a winding 
manufacturing bench without any contacts and without any fixed connection. 
The present invention also relates to a device for implementing the method 
according to the invention, including a pay-out reel onto which a winding 
wire is wound and a distributing device which moves longitudinally and in 
rotation around a core to allow a coil to be placed regularly in 
contiguous turns on the core, characterised in that an air ionising device 
arranged inside a frame diffuses ionised air onto the coil during 
manufacture, the electric charges of said ionised air cancelling out the 
electrostatic charges of the opposite sign induced by friction in said 
coil.

DESCRIPTION OF A PREFERRED EMBODIMENT 
In the following description, the elements identical to those previously 
described will be designated by the same numerical references. 
The device for implementing the method according to the invention, 
designated as a whole by the general numerical reference 22 in FIG. 3, 
includes a pay-out reel 24 onto which winding wire 6 is wound. This wire 6 
enters a frame 28 via an opening 26, inside which it is guided in 
translation by means of a directional guide device 30. This guide device 
30 is for example formed of two felt pads 32 which guide and clean wire 6 
by friction. It should be noted that this first guiding and cleaning step 
can constitute a source generating electrostatic charges in wire 6. 
Wire 6 is then taken up by a distributing device 34 in position above 
ferrite core 2. Distributing device 34 which moves longitudinally to core 
2 and in rotation around the latter allows wire 6 to be placed regularly 
in contiguous turns 8 onto core 2. After winding, wire 6 is cut and its 
free ends 12 and 14 will be applied by thermocompression onto contact 
bumps 16 of integrated circuit 4. 
According to the present invention, an air ionising device 36 is arranged 
inside frame 28 in which it diffuses ionised air carrying electric charges 
which cancel out the electrostatic charges of the opposite sign induced by 
friction in wire 6. Wire 6 thus becomes electrically neutral again and its 
free ends 12, 14 can be bonded onto contact bumps 16 of integrated circuit 
4 without risking destroying the latter by electrostatic discharge. 
It goes without saying that various simple modifications and variants fall 
within the scope of the present invention.