EP0043558A1 - Method of manufacturing a miniature adjustable inductance and inductance made by this method - Google Patents

Abstract

This process consists in particular in making two pads this connection (1, 2) with a relative positioning one vis-à-vis the other definitive from two opposite sides of a frame cut from a metal strip, to be placed a winding (5) on the frame by fixing its ends to the connection pads (1, 2), to coat the winding (5) and the connection pads (1, 2) in a plastic material leaving the internal volume free of the winding and the access orifices (7, 8) one of which (7) is threaded, then separating the connection pads from the frame and making a plunger core from a ferromagnetic stick (9) with an overmoulded headless screw (10) at one of its ends fitting the threaded access orifice (7).

Description

The present invention relates to a method of manufacturing a miniature electronic component having an adjustable inductance obtained using a winding associated with a ferromagnetic plunger core whose penetration depth is adjustable.

There are already adjustable miniature chokes encased in plastic. In general, they include a large number of small parts accessory to the winding and to the plunger core: mounting base for connection terminals, winding support mandrel, spacer for mounting the coil on the base, supporting parts the core and allowing its sliding in the coil. These small parts make assembly meticulous and expensive. In addition, these inductors generally have a distributed capacity value whose importance makes their use difficult in systems operating at high frequencies, transmission systems at 560 Mbits for example.

The object of the present invention is to produce adjustable miniature inductors with a minimum number of parts, low cost and good reliability. Another object of the invention is the production of adjustable miniature inductors having a distributed capacitance value compatible with their use at high frequencies.

• - bobiner, sous air chaud, sur un mandrin provisoire, un enroulement de fil conducteur revêtu d'un isolant thermoadhérent 'et retirer le mandrin provisoire,
• - étamer et cambrer les extrémités de l'enroulement,
• - réaliser un bâtonnet ferromagnétique d'un diamètre inférieur à l'enroulement et surmouler à une de ses extémités une vis sans tête en matière plastique,
• - réaliser deux patins de raccordement pour les extrémités de l'enroulement, avec un positionnement relatif l'un par rapport à l'autre définitif, à partir de deux côtés opposés d'un cadre découpé dans une bande métallique, lesdits côtés ayant leurs flancs repliés vers la face supérieure de la bande et étant liés au reste du cadre par des étranglements permettant leur séparation ultérieurs,
• - placer l'enroulement sur le cadre, approximativement dans sa position définitive, et le fixer par ses extrémités aux patins de raccordement,
• - placer l'enroulement monté sur un cadre dans un moule présentant une cavité de forme parallélépipèdique, ouverte sur une face de moindres dimensions qu'un cadre, avec deux parois latérales opposées ayant le même écartement que les patins de raccordement d'un cadre, le cadre supportant l'enroulement placé dans la cavité du moule venant sur la face ouverte de cette dernière avec ses patins de raccordement, pénétrant dans la cavité le long desdites parois latérales,
• - disposer une broche à l'intérieur de la cavité du moule par un orifice latéral pratiqué dans l'axe de la position définitive de l'enroulement, ladite broche ayant une partie filetée dont le diamètre et le filetage correspondent à ceux de la vis sans tête surmoulée à une extrémité du bâtonnet ferromagnétique et qui est prolongée, par l'intermédiaire d'un épaulement, d'une tige d'extrémité lisse ayant un diamètre supérieur à celui du bâtonnet ferromagnétique mais inférieur à celui de l'enroulement et s'enfilant dans ce dernier, ladite broche assurant un positionnement précis de l'enroulement et la sauvegarde de l'espace de débattement du bâtonnet ferromagnétique et de sa vis sans tête,
• - remplir la cavité du moule d'un matériau plastique d'enrobage,
• - retirer la broche par dévissage après durcissement du matériau plastique,
• - démouler et monter le bâtonnet ferromagnétique dans le logement laissé par la broche.

Its subject is a manufacturing process consisting of:

• - wind, in hot air, on a temporary mandrel, a winding of conductive wire coated with a thermoadherent insulator 'and remove the temporary mandrel,
• - tin and arch the ends of the winding,
• - make a ferromagnetic stick with a diameter less than the winding and overmold at one of its ends a plastic headless screw,
• - Make two connecting pads for the ends of the winding, with a relative positioning relative to the other definitive, from two opposite sides of a frame cut from a metal strip, said sides having their sides folded towards the upper face of the strip and being linked to the rest of the frame by throttles allowing their subsequent separation,
• - place the winding on the frame, approximately in its final position, and fix it by its ends to the connection pads,
• - place the winding mounted on a frame in a mold having a cavity of parallelepiped shape, open on a face of smaller dimensions than a frame, with two opposite side walls having the same spacing as the connection pads of a frame, the frame supporting the winding placed in the mold cavity coming on the open face of the latter with its connection pads, penetrating into the cavity along said side walls,
• - have a spindle inside the mold cavity by a lateral hole made in the axis of the final position of the winding, said spindle having a threaded part whose diameter and thread correspond to those of the screw head overmolded at one end of the ferromagnetic rod and which is extended, via a shoulder, a smooth end rod having a diameter greater than that of the ferromagnetic rod but less than that of the winding and s' threading into the latter, said spindle ensuring precise positioning of the winding and safeguarding the clearance space of the ferromagnetic rod and its grub screw,
• - fill the mold cavity with a plastic coating material,
• - remove the spindle by unscrewing after hardening of the plastic material,
• - unmold and mount the ferromagnetic stick in the housing left by the spindle.

According to an advantageous implementation, the mold used is a flexible mold filled by gravity with the plastic coating material and traversed right through by the spindle.

• - deux patins de raccordement électrique formés chacun d'une lamelle métallique pliée en forme de U avec deux ailes, de profil et de hauteur différents, réunies par une base, la plus grande aile se terminant par un doigt plié vers l'autre aile, lesdits patins étant disposés en vis-à-vis symétriquement dans deux faces latérales opposées du parallélépipède, chaque patin ayant sa base placée contre l'arête inférieure de la face latérale dans laquelle il est logé, avec sa plus grande aile affleurant la surface de la face latérale et présentant un flanc accessible de l'extérieur du parallélépipède, et avec sa plus petite aile pénétrant dans la base du parallélépipède et assurant son ancrage dans ce dernier,
• - un enroulement disposé à l'intérieur du parallélépipède avec ses extrémités raccordées aux doigts des patins de raccordement,
• - un matériau plastique remplissant tout le parallélépipède à l'exception de l'intérieur de l'enroulement et de deux orifices d'accès cylindriques, dont l'un est fileté et de plus grand diamètre que l'enroulement, disposés chacun dans l'axe de ce dernier
• - et un bâtonnet ferromagnétique, de plus faible diamètre que l'enroulement, avec une vis sans tête en plastique surmoulée à l'une de ses extrémités, de diamètre et de filetage correspondant à ceux du dit orifice d'accès.

The present invention also relates to an adjustable miniature inductor coated in a plastic material and obtained by the aforementioned manufacturing process. This miniature inductor has the shape of a parallelepiped and includes:

• - two electrical connection pads each formed by a metal strip folded in a U shape with two wings, of different profile and height, joined by a base, the largest wing ending in a finger bent towards the other wing, said pads being arranged symmetrically opposite in two opposite lateral faces of the parallelepiped, each shoe having its base placed against the lower edge of the lateral face in which it is housed, with its largest wing flush with the surface of the lateral face and having a side accessible from the outside of the parallelepiped, and with its smallest wing penetrating into the base of the parallelepiped and ensuring its anchoring in the latter,
• - a winding arranged inside the parallelepiped with its ends connected to the fingers of the connection pads,
• - a plastic material filling the entire parallelepiped with the exception of the interior of the winding and two cylindrical access orifices, one of which is threaded and of larger diameter than the winding, each arranged in the axis of the latter
• - And a ferromagnetic stick, of smaller diameter than the winding, with a plastic headless screw molded at one of its ends, of diameter and thread corresponding to those of said access orifice.

The largest wing of a skid advantageously extends over the entire width of a side face of the parallelepiped and comes halfway up the latter.

• -la figure 1 est une vue en perspective et en transparence d'une inductance miniature ajustable avec son noyau magnétique démonté,
• - la figure 2 représente les patins de raccordement de l'inductance miniature ajustable de la figure 1, à différents stades de leur fabrication,
• - la figure 3 représente , en cours de montage, les patins de raccordement et l'enroulement de l'inductance miniature ajustable représentée à la figure 1,
• .- la figure 4 représente différents stades du moulage du matériau plastique enrobant l'inductance miniature ajustable représentée à la figure 1,
• - et la figure 5 est une vue en coupe d'un moule utilisable pour le moulage du matériau plastique enrobant l'inductance miniature ajustable représentée à la figure 1.

Other characteristics and advantages of the invention will emerge from the appended claims and from the description below of an embodiment given by way of example. This description will be made with reference to the appended drawing in which:

• FIG. 1 is a perspective and transparent view of an adjustable miniature inductor with its magnetic core removed,
• FIG. 2 represents the connection pads of the adjustable miniature inductor of FIG. 1, at different stages of their manufacture,
• FIG. 3 represents, during assembly, the connection pads and the winding of the adjustable miniature inductor shown in FIG. 1,
• FIG. 4 represents different stages of the molding of the plastic material coating the adjustable miniature inductance shown in FIG. 1,
• - And Figure 5 is a sectional view of a mold usable for the molding of the plastic material coating the adjustable miniature inductance shown in FIG. 1.

The various elements are shown in these figures on enlarged scales, the dimensions of an adjustable miniature inductor being less than a centimeter. These scales are different from one figure to another according to the particularities to highlight.

The adjustable miniature inductor shown in Figure 1 is coated in a plastic material and has the general shape of a rectangular parallelepiped. It comprises: two connection pads 1, 2 arranged opposite at the base of two opposite lateral faces 3 and 4 of the parallelepiped, a cylindrical winding 5 placed in the center of the parallelepiped perpendicular to the lateral faces 3, 4 and connected by its ends to the connection pads 1, 2, a plastic material 6 filling the parallelepiped with the exception of the interior volume at the winding 5 and two access orifices 7 and 8 formed in the lateral faces 3 and 4, the a 7 is threaded and of larger diameter than the winding 5, and a ferromagnetic rod 9, of diameter smaller than that of the winding 5, provided at one end with a grub screw 10, of overmolded plastic material, of which the diameter and the thread correspond to those of the access orifice 7 and which is provided with a diametrical actuation slot 16.

The connection pads 1, 2 are identical. Their shape appears more clearly in Figure 3. Each of them consists of a metal tongue folded in a U shape with two wings 11, 12 of different profile and height joined by a base 13. The largest wing 11 is flush on the surface of a lateral face of the parallelepiped of which it occupies the lower half over the entire width. It is of substantially rectangular profile with in the middle of its top, a large rounded notch 14 ensuring the release of the access orifices 7 and 8 to the interior volume of the winding 5, and, on the side of its top a finger 15 which is folded towards the other wing and on which is fixed one end of the winding 5. The smallest wing 12 also has a rectangular profile. It is centered in relation to the large one and is used for anchoring the shoe in the plastic coating material. Its smaller width allows shear forces to refer to its edge and not to the finger 15 of the large wing, in the event of poor adhesion of the plastic coating material on the shoe. For better anchoring it can be provided with lateral notches.

The absence of the mandrel makes it possible to reduce the diameter of the winding and consequently the value of the distributed capacity at the same self / inductance value. The positioning of the pads serving as connection access, perpendicular to the axis of the winding, also contributes to weakening the value of the distributed capacity.

The adjustable miniature inductor which has just been described connects to the tracks of a circuit by its connection pads for example, by forming a solder fillet or also by means of spacers as is customary with the small electronic components in the form of a block with connection terminals embedded in their lateral faces. Its manufacture illustrated in Figures 2 to 5 does not require accessory mounting parts.

The winding 5 is made by winding, under hot air and on a temporary mandrel, a conductive wire coated with a thermoadherent insulator. The temporary mandrel is withdrawn at the end of the winding and the ends of the winding are tinned, one of which is also bent.

The plunger core is made from a ferromagnetic rod with a diameter less than that of the winding by overmoulding at one end of the rod a headless screw, made of plastic, provided with a diametrical actuation slot.

The connection pads are made from a metal strip by cutting and folding. This strip is for example a 0.1mm thick copper strip cut by a photoengraving technique, tinned by an electrolytic technique and then folded. Figure 2 shows sections at different stages of development.

The left section belongs to a band immediately after its cutting. It has the general shape of a ladder. The connection pads are the flat metal strips which constitute the bars. These strips are attached to the uprights of the ladder by throttles 17, 18 facilitating their subsequent separation. They have two lateral edges, each cut out in the form of a short rectangular tongue, one taking the entire length of a bar and being embellished at its end with a broad, rounded median notch 14, and with a finger 15, the other of lesser width and length being centered on the middle part of a bar. The connection pads are grouped in pairs and arranged symmetrically in each paired with their small tabs facing each other. The pads of a pair are intended for the same adjustable miniature inductor. They constitute, with the strip portions which join them, a rigid frame and have, within this frame, the final spacing which they will keep in the adjustable miniature inductor.

The middle section of Figure 2 belongs to a strip having undergone cutting and a first folding. Each bar of the ladder had its lateral sides folded towards the upper face of the strip and acquired a U-shaped section with two wings of different profile and height, the largest wing 11 corresponding to the largest tongue and located on the outside of each pair of connecting pads.

The right section of Figure 2 belongs to a strip having undergone another folding phase during which the fingers 15 were folded inwardly of the connecting pads.

A winding 5 is then welded at its ends to the fingers 15 of each pair of connection pads which remain integral with the strip and held relative to each other in a definitive positioning within a rigid frame. As can be seen in FIG. 3. One of the ends 19 of the winding 5 is not arched, escapes tangentially from the latter and arrives perpendicularly to the finger 15 of a connection pad while the another end 20 is bent parallel to the axis of the winding 5 after having escaped tangentially and arrives in the axis of the finger 15 of the other connection pad. This arrangement allows the winding to be brought closer to one of the connection pads in order to provide between the winding 5 and the other connection pad sufficient space for the deflection of the ferromagnetic rod and of the grub screw which constitute the core. diver.

The frames which each consist of a pair of pads connection and portions of strips 21 which unite them and on each of which is welded a winding 5 are then separated to undergo individually a molding operation by which the plastic coating material is added.

FIG. 4 represents a base 41 supporting three identical molds with three frames supporting unwindings at different stages of the molding operation.

The molds each consist of a cavity 30 determining the external contour of an adjustable miniature inductor, pierced by a pin 31 safeguarding the clearance space of the ferromagnetic rod and its grub screw.

The spindle 31 has a smooth end rod 32 extending through a shoulder 33 a threaded portion 34 of larger diameter, itself followed by a non-threaded portion 35 ending in a screw head 36. The smooth end rod 32 has a diameter less than that of the winding 5 but greater than that of the ferromagnetic rod. The threaded part 34 has a diameter and a thread corresponding to those of the grub screw 10 (FIG. 1) and the non-threaded part 35 has the same diameter as the threaded part 34.

The cavity 30 has the shape of a rectangular parallelepiped. It is open by its upper face and has two opposite lateral faces 37, 38 having a spacing equal to that separating the pair of connection pads from a frame, and a width equal to that of a connection pad. ie the width of the largest wing 11 of the latter. These two lateral faces 37, 38 are each pierced, in their central part, with an access orifice 39 respectively 40 allowing the introduction of the spindle 31. The access orifice 39 of the lateral face 37 is crossed by the whole spindle and has a diameter equal to that of the unthreaded part 35 of the latter. The orifice 40 is crossed only by the end rod 32 of the spindle and has a smaller diameter equal to that of the latter.

The left mold of Figure 4 is shown before introduction of a winding carried by a frame. The pin 31 is removed outside the cavity 30 and the frame presented upside down above the cavity 30, the connection pad connected to the end arched 20 of the winding 5 in the extension of the side face 37 and the other shoe in the extension of the side face 38.

The middle mold of Figure 4 is shown with a coil in place. The winding '5 has been slid into the cavity 30 and the supporting frame placed on the upper face of the cavity 30, the connecting pads penetrating into the upper part of the cavity along its lateral faces 37 and 38. The pin 31 was then introduced into the cavity through the access orifice 39 and then threaded into the winding 5 and into the access orifice 40. Thanks to its shoulder 33 it ensures, as appears more clearly in the figure 5, precise positioning of the winding with respect to the connection pads and also with respect to the plunger core. The mold is ready to be filled with a plastic gravity-coated coating material.

The right mold of Figure 4 is shown at the end of a molding operation. The plastic material has solidified, the pin 31 has been removed from the cavity 30 by unscrewing and winding and the two connection pads coated in a mass of plastic lifted by the portions 21 of remaining tape.

The adjustable miniature inductor is finished by sectioning by folding the remaining portions 21 of strip and by mounting a stick provided with its grub screw in the housing left by the pin 31.

Advantageously, a flexible mold is used which facilitates demolding operations. This mold is then placed in a support during the molding operation as shown in the sectional view of FIG. 5. In this figure, there is a flexible mold 50 with its cavity 30 placed in a rigid support 51. Notches'52 and 53 are provided in the rigid support 51 to allow the introduction of the spindle 31. The rigid support 51 is provided with a lateral finger 54 which serves as a depth stop for the spindle 31 and ensures in cooperation with the shoulder 33 of the latter a precise positioning of the winding 5 inside the cavity 30 which allows good reproducibility of the electrical characteristics between the copies of the same value of an adjustable miniature inductor.

Without departing from the scope of the invention, it is possible to modify certain provisions or to replace certain means by equivalent means.

Claims (10)

1 / A method of manufacturing an adjustable miniature inductor with a ferromagnetic plunger core coated in a plastic material, in which: a coil (5) of conductive wire coated with a thermoadherent insulator is wound under hot air, the temporary mandrel is removed and a ferromagnetic rod (9) of smaller diameter than the winding (5) is produced with a grub screw (10). made of plastic overmolded at one of its ends, characterized in that it consists further to - make two connecting pads (1, 2) for the ends (19, 20) of the winding (5), with a relative positioning relative to the other definitive, from two opposite sides of a frame cut from a metal strip, said sides having their sides folded towards the upper face of the strip and being linked to the rest of the frame by throttles (17, 18) allowing their subsequent separation, - tin and arch the ends (19, 20) of the winding (5), - place the winding (5) on the frame, approximately in its final position, and fix it by its ends (19, 20) to the connection pads (1, 2), - Place the winding in a mold having a cavity (30) of parallelepiped shape, open on a lesser face. dimensions than a frame, with two opposite side walls (37, 38) having the same spacing as the connection pads (1, 2) of a frame, the frame supporting the winding (5) placed in the cavity (30 ) of the mold coming from the open face of the latter with its connection pads (1, 2) penetrating into the cavity (30) along said side walls (37, 38), - arranging a spindle (31) inside the cavity (30) of the mold, by a lateral orifice (39) formed in the axis of the final position of the winding (5), said spindle having a threaded part (34) whose diameter and thread correspond to those of the grub screw (10) molded at one end of the ferromagnetic rod (9) and which is extended, via a shoulder (33), with a smooth end rod (32) having a diameter greater than that of the ferromagnetic rod but less than that of the winding (5) and threading into the latter, said spindle (31) ensuring the precise positioning of the winding (5) and the safeguarding of the clearance space of the ferromagnetic rod (9) and of its grub screw (10 ), - filling the cavity (30) of the mold with a plastic coating material, - remove the spindle (31) by unscrewing after hardening of the plastic material, - unmold and mount the ferromagnetic stick (9) with its grub screw (10) in the housing left by the spindle (31). 2 / A method according to claim 1, characterized in that the winding (5) is placed on the frame so that its axis is perpendicular to the pads (1, 2). 3 / A method according to claim 1, characterized in that the mold used for the coating is a flexible mold (50). 4 / A method according to claim 1, characterized in that the mold used for the coating is a flexible mold (50) placed in a rigid support (51) pierced with notches (52, 53) allowing the introduction of the spindle (31) in the cavity (30) of the mold (50) and provided with a lateral finger (54) serving as a depth stop for the spindle (31). 5 / A method according to claim 1, characterized in that the filling of the cavity (30) of the mold with a plastic material is effected by gravity. 6 / Adjustable miniature inductor of parallelepipedal shape coated in a plastic material, obtained by the method according to claim 1 and characterized in that it comprises: - two electrical connection pads (1, 2) each formed by a metal strip folded in a U shape with two wings (11 and 12) of different profile and height, joined by a base (13), the largest wing (11) ending with a finger (15) folded towards the other wing (12), said pads (1, 2) being arranged symmetrically, opposite, in two opposite lateral faces (3, 4) of the parallelepiped, each shoe having its base (13) placed against the lower edge of the lateral face in which it is housed, with its largest wing (11) flush with the surface of this lateral face and having a side accessible from the outside of the parallelepiped, and with its smallest wing (12) penetrating into the base of the parallelepiped and ensuring its anchoring in the latter, - a winding (5) arranged inside the parallelepiped with its ends (19, 20) connected to the fingers (15) of the connection pads, - a plastic material filling the entire parallelepiped with the exception of the inside of the winding (5) and two orifices (7, 8) of cylindrical access, one of which (7) is threaded and of larger diameter as the winding (5), each arranged in the axis of the winding (5) - And a ferromagnetic rod (9) of diameter smaller than the winding (5), with a plastic grub screw (10), molded at one of its ends, of diameter and thread corresponding to those of said orifice access (7). 7 / inductor according to claim 6, characterized in that the large wing (11) of each connecting pad is flush with the lateral surface of the parallelepiped, surface of which it occupies the lower half over the entire width. 8 / inductor according to claim 6, characterized in that the large wing (11) of each connecting shoe has a substantially rectangular profile with in the middle of its top a large rounded notch (14). 9 / inductor according to claim 6, characterized in that the small wing (12) of each connecting pad has lateral notches improving the anchoring of the pad in the plastic coating material. 10 / inductor according to claim 6, characterized in that the winding (5) is arranged perpendicular to the connecting pads (1, 2) inside the parallelepiped.

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