DE1900392A1 - Manufacturing process for electromagnetic components, in particular pulse transformers - Google Patents

Description

IBM Germany International »Büro-Maschintn Getellechaft mbH

Applicant:

Official File number:

File number of the applicant in:

Boeblingen, January 2, 1969 at-hl

International Business Machines Corporation, Armonk, N.Y. 10504

New registration

Docket FI 967 106

Manufacturing process of electro-magnetic components, especially pulse transformers

The invention relates to a method for producing electromagnetic Components, in particular pulse transformers, whose preferably magnetic and ring-shaped core is wrapped in turns.

Such pulse transformers, or similar electro-magnetic components, whose dimensions are so small that they are among the miniature components, are used in large numbers in the circuit arrangements for data processing systems, used in electronic control systems or, for example, in televisions. They are also used as storage elements.

The pulse transformers generally known to the person skilled in the art were previously manufactured in such a way that the turns manually of small quantities

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Hand made from very thin insulated wire. This The manufacturing process is costly and also has the disadvantage that the electrical values of these pulse transformers are unimportant have a relatively large spread. The use of toroidal winding machines is only possible with larger components and not with such small designs, whose dimensions are approximately at 12.5 χ 6.5 3.5 mm.

■ k Through the German patent specification 1. 245.495 a method

known for the mass production of electro-magnetic components, where a magnetic toroidal core is to be provided with turns. In this process, a pipe is made of magnetic Material covered inside and outside with an insulating potting compound and in this potting compound are in precisely defined intervals The conductor wires are embedded running in the axial direction. Then the pipe surrounded by the ladders is cut, so that ring-shaped disks are formed. The connections between the outer and inner conductors produced so that the core cross-section wrapping turns or windings result. This method, in spite of its advantages, still has the disadvantages that a number of operations are required for complete manufacture of a component and that the manufacturing process of

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Connections between the outer and inner winding sections, as well as the connection connections is still too expensive and therefore not fully satisfied.

By the American patent 3,319,207 a method for the production of turns surrounding a core known, in which the core of an annular insulating compound z. B. Ceramic consists, in which a helical course having grooves z. B. are incorporated by grinding. These Grooves are filled with a metal precipitate, whereby there is a winding.

Another manufacturing process for miniaturized windings which are arranged on an elongated core and z. B. in clocks was used by the German Offenlegungsschrift 1,439. 264 known. In this process the core is provided with a metal coating and through a photolithographic process the pattern of the winding is shown on the metal coating. The metal coating not required for the winding is removed again by etching or grinding.

These aforementioned known methods of manufacturing windings that a preferably ring-shaped magnetic core around

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In addition, the method allows unavoidable dimensional deviations to balance the sintered cores.

The invention is explained in more detail below with reference to the exemplary embodiments and the associated drawings. Show it:

Fig. 1 schematically shows the individual operations of the Her

recruitment procedure,

Fig. 2 is a side view of an injection molding device for

Embedding a magnetic core in plastic according to a first embodiment of the invention,

3A shows a sectional view of the opened plastic injection molding

mold with inserted magnetic core,

3B is a sectional view of the closed mold;

4 shows an enlarged perspective illustration of a

embedded core made with the apparatus shown in Figures 3A and 3B,

Fig. 5 shows the various stages before and during the metal

Injection molding according to the first embodiment,

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Loops are manufacturing technology for mass production and too expensive in terms of price.

The invention is based on the object of creating a manufacturing method for the mass production of electro -magnetic components, especially pulse transformers, the one preferably contain magnetic, ring-shaped core, which is looped helically by turns or windings. This new process technology should be limited to just a few work steps, be simple and inexpensive complete components deliver.

According to the invention, this object is achieved in that, in a first step, the core is made of plastic using a casting mold is embedded that in the surface of the plastic casing made channel-like depressions to form the winding space and that in a second step the windings and the conductive connections are made by metal injection molding will.

This method according to the invention considerably simplifies the otherwise steps necessary in the manufacture of pulse transformers and the like and, above all, eliminates the need to form grooves in the ferrite or ceramic material of which the core is made.

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(ρ

6 shows an enlarged perspective diagram

position of a finished magnet component, z. B. a pulse transformer, according to the first example,

7 along an enlarged sectional view

the line 7-7 in Fig. 6 of a cast bearing tongue,

8 shows an enlarged sectional view along

the line 8-8 in Fig. 6 of a cast connecting line and a similar one Connection,

9A and 9B are sectional views of the plastic injection molding

form to form a "unit carrier" with a magnet embedded in plastic

* ■ core according to a second embodiment

example of the invention,.

10 shows an enlarged perspective illustration

a core embedded in plastic according to the second embodiment,

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Figure 11 is a bottom plan view of a similar one

carrier with embedded core,

Fig. 12. a winding scheme for the in Fig.

shown core embedded in plastic,

13 shows the manufacture of the windings, ver

connections and connections on a core embedded in plastic with schematic Representation of the metal injection molding facility,

14A shows the state of the magnetic component

after metal injection molding and before etching,

14B shows the state of the magnetic component

the metal injection molding and after etching away the excess metal and

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15 is a perspective illustration of a

Group of pulse transformers that are connected to form a module of four.

According to the scheme shown in Fig. 1, the ring-shaped cores are first embedded in plastic. This step is performed in the ψ in Figs. 2, 3A and 3B unit

and thereby the embedded core shown in FIG. 4 is produced.

In Fig. 2, a conventional plastic injection molding device 10 is shown. The elements of this facility outside the actual form comprise a hydraulic cylinder 12 and a piston 13 with which the plastic material is pressed into the mold 14, as well as the upper and lower pressure tables 15A and 15B. According to the illustration In Fig. 3A there is a chamber 16 in the upper printing table with the through channels 18 in the upper half of the mold 14A in connection. This allows plastic material to flow into the mold cavity 20 when the piston 13 after is driven down. The pure magnetic core 100, still without

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the plastic casing is inserted into the lower part 14b of the mold as shown in FIG. 3A, as indicated by arrows.

The cavity 20 in the lower part 14b of the mold is substantially annular for receiving the illustrated annular magnetic core formed. The walls of the cavity are complementary to the desired outer one Form of the completely embedded core 110 shown in Fig. 4, i.e. the side walls and bottom of the cavity 20 of the mold are provided with a series of elevations or ribs 24, which the corresponding depressions or Grooves 120a on the base and top surface, as well as the inner and outer side walls in the one surrounding the core 100 (FIG. 4) Form plastic casing 120. The upper part 14a of the mold is also provided with the necessary elevations 26, to define the corresponding indentations 120a on the top of the embedded core.

When the two mold halves as shown in FIG. 3B

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brought together and the plastic material is pressed into the mold 14, the cavities remaining between the core 100 standing in the lower mold half 14b and the walls of the casting mold 20 are completely filled with plastic material. The core is thus completely surrounded by the plastic casing 120. In the form of support W pins 27 are for correct storage and alignment of the core

which lead to depressions 120b in the casing 120.

For the purposes of the method described, it turns out a thermosetting plastic material and consequently an epoxy resin as for the envelope 120 of the magnetic core 100 as best for. Epoxy resin is an insulator and can thus provide the necessary insulation for the conductive iron core 100 from take over the windings 250 shown in Fig. 6 best. The selected working temperature in the plastic injection molding facility is around 170 ° C, i.e. preferably between 140 and 180. Nevertheless, the following is the

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• For the sake of simplicity, only one mold is described in text and drawings, can of course be very diverse Forms are used. The injection molding process for producing the sheathing of the cores 100 with plastic represents represents a significant step forward in compensating for any dimensional deviations in these ring-shaped iron cores. So it is no longer necessary to first embed all the magnetic cores, then carefully examine them and then go through them any facility such. B. a grinding machine to be brought to mass with close tolerances, but the Cores can be brought directly from the sintering treatment into the casting device and embedded within wide dimensional limits will. The embedded cores 110 are practically identical as they come from the casting device, there they have all been cast in the same form or in proportionally the same form.

The grooves 120a are formed by the wall of the mold 14, which is designed in a complementary manner. These grooves are in series like this connected to each other that they are continuous turns

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form. If the metal for making the windings is subsequently poured into these grooves, this will result in Helical windings are generated which completely surround the annular core 100.

The finished cast part in the form of the fc core 110 embedded in plastic with the winding space open at the top

does not come out of the pouring device as completely as it is shown in FIG. 4, of course. When pouring can namely especially because of the grooves 120a, the formation of casting burr cannot be avoided. The excess plastic can be however, relatively easily removed in a well known manner so as to complete the embedded core 110.

The cores embedded in plastic are then sent to the metal injection molding station. Besides the screw-like windings for the encapsulated magnetic cores and the necessary connections in the same operation and connections are made from the windings to the associated terminals. In this station, if necessary

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The core is also attached to a plastic carrier strip so that it can be inserted into a circuit board or a integrated circuit pack can be used.

In Fig. 5, the production of magnetic components is greatly simplified in individual steps from right to the right shown on the left. On the right-hand side of the picture, the is made up of several interconnected carrier plates 210 existing carrier strips 200 introduced into the casting machine, not shown here. The carrier strip 200 of about 50 m in length generally consists of support plates 210 in an articulated row. In this way, the strip of plastic plates can easily be wound onto a supply roll and in this Form of the casting machine are fed.

At point A in the figure, the carrier strip is in the injection molding machine introduced. At the same time, a nappy-changing room is embedded and finished according to the description above formed core 110 in the correct position also introduced into the machine.

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The casting machine is described below in connection with the second embodiment of the invention described. It should only be pointed out here that for the special construction of this first embodiment, a suitable mold with the necessary depressions and recesses for producing the connections 220 and the bearing tongues 230 are provided. The metal that wraps the core, to form the connections, etc., is pressed into the mold with such a pressure that the flowing Metal can penetrate into all cavities defined by the grooves and walls of the mold.

With the reverse arrangement according to the illustration in In FIG. 5, the core lies below the carrier plate 210 in each case in the illustration of the finished magnetic component in FIG. 6 above plate 210.

The carrier plates 210 exist at least in this exemplary embodiment made of soft plastic and are therefore extremely flexible. Each carrier plate 210 has a large one in the middle

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Cutout 210a for receiving the encapsulated core 110, as well as two holes 210b on the side for receiving dowel pins the form. In the vicinity of the plate edge a series of holes 210c is arranged, which are used to attach the connecting lines 240 on the plate. Furthermore, a series of holes 21Od for are in the plate around the central cutout 210a the correct fastening of the bearing tongues 230 is provided. As can be seen from FIGS. 5 and 6, there are on each carrier plate 210 on one side balls 212 and on the opposite side corresponding recesses 214 attached. A number of plates can thus be put together in series, and the balls 212 in the recesses mentioned 214, a long strip 200 of carrier plates can be engaged in this way before the actual injection molding operation 210 form. Each individual carrier plate can be moved by feeding this panel strip with a correspondingly accurate scale Insert 210 in the correct position in the casting machine, which can be achieved either by separating the individual carrier plates 210 from the whole strip 200 upon reaching point A and subsequent feeding in pieces or by continuous

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Feeding of the entire strip 200 to the casting machine without Individual plates 210 can be separated out, as shown in FIG. 5. After inserting the carrier plates in the machine, the embedded core 110 is held in place, the i'orm is closed and the metal is then in the shape is pressed around the windings 250 in this manner

ψ around the core, the bearing tongues 230, the connecting lines

240 and, if necessary, also to form the connections 220.

With the method described above of embedding the magnetic cores in plastic while simultaneously forming the The winding space and the subsequent metal injection molding of the winding and connections can be arranged in numerous ways produce. In addition to the pulse transformer mentioned above, another example is an arrangement with a primary winding called with center tap and a secondary winding. Such a construction requires internal connections to the five connections 220 shown in FIG. 6,

In metal injection molding, the embedded core 110 and

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the carrier plate 210 is pressed onto one another between two preheated parts of a casting mold with a force of approximately 450 kg. The mold is generally depending on the metal used to a temperature of about

ο
Heated to 230 C. This temperature has been found to be the best after numerous tests. At lower temperatures

o Doors in the range of, for example 210 C, problems arose with certain compositions or alloys that were used in the tests because the metals solidified when they entered the mold or did not fill the mold properly or flowed into it too quickly or because Too much excess metal produced casting burr. In the tests, a tin-silver alloy proved to be ideally suited, in which the silver content was changed from 5% to around 15%. Certain problems also arise from the fact that the metal has to be poured into the inner grooves of the winding space with cross-sectional dimensions in the order of 0.1 mm 0.15 mm. However, these problems are solved by the method described here.

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One example is a successfully carried out experiment: The tin-silver alloy is melted on a hot plate at a temperature of about 310 C and the so-called hot crucible is also preheated on the hot plate. When the crucible has reached the right temperature, it is clamped onto the injection molding machine and the molten tin-silver alloy is poured into the crucible. For injection molding, a hydraulically driven piston presses the molten alloy into the mold, ie practically into the cavities of the winding space in the plastic casing of the core. Once the metal has solidified, the shape is removed and the magnetic component 260 in the form of a pulse transformer * or the like, which is shown in its finished state in FIG. 6, can be removed.

9 to 15 show a second exemplary embodiment of the method described in connection with another magnetic component to be produced. In contrast

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in addition to the component already described with reference to FIG. 6, a "unit carrier" is used in this exemplary embodiment. poured. When embedding and creating the changing room the entire housing for the core is formed in one operation in the manner that the one referred to above as carrier plate 210 Part with the embedded core is cast in one piece. As a result, the whole case is made made of epoxy resin or a similar material. For the production of this core component marked with the number 300 the die-casting mold for plastic shown in FIGS. 9A and 9B is designed in such a way that it is the complement of the 10 forms the unit shown. Holes must be formed in the component through the carrier plate 210 go through so that the space for the windings surrounding the core 100 is nowhere interrupted. These Holes 216 are best seen in FIG.

As in the first exemplary embodiment, connections must also be made here between the windings surrounding the core and the connection terminals.

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From a comparison of FIGS. 3A and 3B with FIGS. 9A and 9B clearly show the differences in the form, which are required to form the unit shown in FIG. 10 in one operation. In Figs. 9A and 9B the same numbers are used for designation as in Figs. 3A and 3B. The cavity 20 shown in Fig. 9A becomes now expanded in such a way that the plastic material required to form the base or carrier plate 210 flows in can. The core 100 is again shown in position in the lower half 14b of the mold. The passages 18 are indeed now arranged a little differently, but have the same purpose and protrude through a system of pouring channels 22 and over a small, easily surmountable entrance threshold 23 with the mold cavity 20 in connection.

In the illustration of FIG. 9A, the axially extending elevations and projections 24 for delimiting the grooves in of the embedding so that they determine the required holes 216 in the carrier plate 210. Support supports 27 again have core 100 here.

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As best seen in Figures 10 and 11, are the necessary grooves for the later inclusion of the connecting lines also when pouring the plastic embedding set. Some of these were labeled with the number 218 Grooves are on the underside of the support plate 210. A groove 217 is also on the top of the plate

intended. The embedded cores 300 are shown in FIGS. 10 f

11 and 11 are the same, but the connecting means of the carrier plates for a number of such units 300 are identical in Fig. 11 slightly modified, as here on one Projection of the one side balls 213 are arranged, which in corresponding recesses 215 of an indentation of the other Side of an adjacent plate 210 can engage.

A circuit diagram of the winding for a pulse transformer or the like is shown in FIG. The two windings 320 and 322 made of a wire of rectangular cross section are connected in series between the terminals B and D and represent a secondary coil for the pulse transformer. The other two windings 324 and 326 are between the

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If the device is set up, the individual units 300 are broken out of the continuous strip and automatically the mold 400 is supplied. As with the method described above for the first embodiment, the continuous Strips can also be fed to the casting machine without being divided into individual core components.

The metal in the form of a tin-silver alloy is fed to the mold through channels 410 and applied by the Pressure pressed into the changing room. The metal is simultaneously also in the grooves 217 and 218 for the production of the connecting lines pressed. In addition, the mold 400 is usually designed in such a way that the connection terminals 220 was also formed by the flowing in of the silver-tin alloy.

A great advantage of the combined process is the simplicity of the construction of the metal injection mold 400, which is so simple because the metal is in the winding space that was already formed when the core was embedded and not in

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Connections A and E are connected in series and represent the primary winding. This primary winding has a center tap, ie the connection point between these windings is connected to connection C. The distribution of the winding according to the circuit of Fig. 12 to the grooves 120a of the core member 300 and on the grooves of the support plate 210 can be seen from Fig. 11, where for simplicity, only the primary winding, the course of which by means of arrows L ₁ M, N and P tracing is shown in dashed lines.

The injection molding process for this second exemplary embodiment and the subsequent steps are illustrated with reference to FIG. explained. The special carrier strip as shown in Figure 5 is no longer required here. Multiple in Core members 300 made in one piece become a chain or strip of elements for lighter weight Handling and, if necessary, automatic processing for the second basic step, namely metal injection molding connected with each other. By means of a corresponding, not shown

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At

Grooves of an intricate and rigid metal mold is pressed. So is in the mold 400 at least for the core part only a smooth annular cavity required. It shows that there are numerous different winding patterns can be cast without having to change the arrangement of the cavity of the metal mold, as for a different winding pattern yes only the grooves in the plastic embedding of the core have to be changed,

The magnetic component marked with the number 500 comes out of the casting machine in the shape it does shown on the left in Fig. 13 and in Fig. 14A. It should be noted that the embedded core and the base plate 210 may be completely or partially covered by a skin of excess metal, which is when Giessen has pushed out, because the metal not only penetrates into the grooves, but also bridges completely or partly the spaces between the grooves. The same applies to the spaces or openings on the Plate 210. This excess metal must of course

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removed to avoid electrical shorts between Avoid windings or cables. Compared to the metal in the plastic grooves, this layer is made of spilled material Metal, however, is relatively thin and can be easily removed by taking the entire unit 500 in a caustic bath is immersed, which eats away this thin metal film. For this purpose, Aqua Regia or Nitric acid preferred. The duration of the etching is based on empirical values. The etching must continue until then until the unwanted, thin metal coating is completely removed, and only the desired thicker metal windings and connections remain.

14B shows the finished magnetic component 600 with the metallic conductors 650 which run radially and axially in the grooves and which represent the helical windings of the core.

After etching, the parts are electrically tested and then combined to form the desired modules or the like.

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set. The components 600 are designed in such a way that they can be easily moved by means of the cast-on ball connections put together. In Fig. 15 a module of four is shown in the form of a cube. After assembling into one For such a four-module, the whole thing is immersed in a liquid plastic compound so far that the connections 220 are straight still stick out. A subsequent oven curing polymerizes the liquid plastic material into a solid Resin and on the one hand forms an electrical insulating layer over the windings 650 and the lines 217, 218 and on the other hand makes the base joints 212 and 214 a rigid connection of the quad module.

If some of the magnetic components 600 turn out to be faulty, these can easily be reworked so that a can achieve quite a high yield. If z. B. a short circuit is detected, the defective component 600 goes to the caustic bath back and all the cast metal is etched away or melted on a heated vibrating table. Through this

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the component gets the original shape of the embedded one again The core 300 and the metallic conductors can be re-cast. If the Plastic embedding is faulty, it can be chemically be replaced or burned down. The pure iron core is then re-embedded in plastic material and afterwards newly potted with metal.

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Claims (16)

Claims 1. Process for the production of electro-magnetic components, in particular pulse transformers, the preferably magnetic core of which is wrapped in windings, characterized in that, that in a first step using a mold, the core (100) is embedded in plastic that in the surface of the plastic casing (120) channel-like depressions (120a) are made to form the winding space, and that in a second step by metal injection molding the windings (250, 650) and the conductive connections (240) getting produced. 2. The method according to claim 1, characterized in that the embedding of the core (100) in plastic takes place by injection molding. 3. The method according to any one of claims 1 or 2, characterized in that that the plastic is a thermosetting plastic material. 4. The method according to any one of the preceding claims, characterized in, that the plastic is an epoxy resin. 909831/097 « FI 9-67-106 - 26 - 5. The method according to claim 1, characterized in that the electrical conductors can be made from a tin-silver alloy. 6. The method according to claim 1 or 5, characterized in that that the alloy has a silver content of 5% to 15%. 7. The method according to any one of claims 1 or 2, characterized in, that the core (110) embedded in plastic is connected to a carrier plate (210) made of plastic. 8. The method according to one of claims 1, 2, 5 or 7, characterized characterized in that in the second process step by metal injection molding simultaneously with the electrical conductors as well Bearing tongues (230) for connecting the core and carrier plate are cast on. 9. The method according to any one of claims 1 or 2, characterized in that that in the first method step of embedding of the core in plastic, a carrier plate for forming a core component (300) is cast in one piece. 909831/097 6 FI 9-67-106 - 27 - 10. The method according to any one of claims 1 or 8, characterized in, There are electrical connections in the second step (220) can be produced simultaneously with the windings (250, 650). 11. The method according to any one of claims 1, 7 or 9, characterized in that that the carrier plates (210) are provided with devices (212 to 215) for connecting the plates to one another will. 12. The method according to any one of claims 1 to 6, characterized in that that the embedding of the core (100) in plastic takes place in the temperature range 140 to 180 C, and that the metal injection molding takes place in the temperature range 210 to 250 C. 13. The method according to any one of the preceding claims, characterized in, that the liquid plastic through a centrally arranged in the injection mold (14) EinfüUkanal (16) of a has annular mouthpiece (18), is pressed in and that a radial distribution of the plastic in the injection mold (14) takes place. 909831/097 8 FI 9-67-106 - 28 - 14. The method according to any one of the preceding claims, characterized in, that the liquid metal through centrally arranged in the top and bottom of the Spritzgußforni (400) Channels (410) is pressed in, and that a radial distribution of the liquid metal in the injection mold (400) takes place. 15. The method according to any one of the preceding claims, characterized in, that casting flash and excess metal are removed by etching. 16. The method according to any one of the preceding claims, characterized in, that in each case four finished magnetic components (600) are assembled in a cube shape to form a four-module (700). 909831/0976 FI9-67-106 - 29 -