EP0340574A2 - Electrical press-fit contact member, and method for its production - Google Patents

Abstract

In this contact member for pressing into a hole in an electrical printed-circuit board, the press-in element (23) has an essentially U- shaped cross-section with two elastically flexible U-limbs (24) and a U-web (25) which connects these limbs to one another. In the cross- section of the press-in element (23), the U-web has a strength which exceeds the thickness of each U-limb (24). On its outer surface (26) facing away from the U-limbs (24), the U-web (25) is provided with a rib (27) running in the pressing-in direction. When the press-in element (23) is inserted into a printed-circuit board hole, the rib (27) and the externally located end elements of the two U-limbs (24) come into contact on the circumference of the hole, the U-limbs (24) being bent in an elastically sprung manner against one another and the contact piece being provided with good retention in the hole. The press-in element (23) is preferably produced by extrusion moulding in a moulding shape, the creation of sharp edges on the press-in element (23) being avoided. …<IMAGE>…

Description

The present invention relates to an electrical contact piece for pressing into a bore in an electrical printed circuit board, with a press-in part which is resilient transversely to the press-in direction and which has an essentially U-shaped cross section with two elastically flexible U-legs and a U-web connecting them to one another. The invention further relates to a method for producing the contact piece and a pressing tool for carrying out the method.

It often happens that individual conductor tracks of an electrical circuit board have to be connected to external electrical circuit components or circuit arrangements that do not belong to the circuit board in question. For this purpose, electrical contact pieces are known, which are each pressed into a hole in the circuit board and can thus be mechanically attached to the circuit board. It is also known to provide the peripheral walls of the bores of the printed circuit board receiving the contact pieces with an electrically conductive coating, in particular made of copper with a tin plating, which coating is connected to at least one of the conductor tracks, so that when each contact piece is pressed in automatically A perfect electrical connection between the contact piece and at least one assigned conductor track is created and soldering is unnecessary.

There are already numerous forms of contact pieces for the press-in technique described. These generally have the shape of a pin, which has a widened press-in section with properties that are resilient in the direction transverse to the longitudinal axis of the pin, so that a good fit of the pressed-in contact piece is ensured even if the inside diameter of the holes in the printed circuit board is within defined tolerances varies.

The widened press-in section of the contact pieces has hitherto usually been formed by local splitting into two legs running approximately parallel, spread apart from one another or laterally offset with respect to one another, a stamping or cutting technique being used which generally led to sharp longitudinal edges of the press-in section. Such sharp longitudinal edges have the disadvantage that when the contact piece is pressed in, they may cut out fine chips from the metallic coating on the peripheral wall of the hole in the printed circuit board, which chips may stick somewhere on the printed circuit board and can form disruptive contact bridges between conductor tracks. In order to avoid this danger, the outer longitudinal edges of the press-in section, which come into contact with the peripheral wall of the circuit board bore, have already been rounded, an additional work step being necessary in the manufacturing process.

Several known contact pieces of the type described have the further disadvantage that their press-in section is pressed in Condition of use only with two approximately diametrically opposed outer longitudinal edges on the peripheral wall of the hole in question of the circuit board and therefore does not always sit sufficiently tilt-stable in the hole. Contact pieces of the type described are shown, for example, in US Pat. No. 4,186,982 and in BE Pat. No. 818,173.

It is also known to shape the press-in section of the contact pieces by flat pressing and then rolling them in such a way that they have an approximately horseshoe-shaped, W-shaped or cloverleaf-shaped cross section, e.g. in U.S. Patent 3,783,433. Such types of construction require relatively complicated multi-stage manufacturing processes.

The present invention is primarily based on the object of designing a contact piece of the type mentioned in such a way that its press-fit part in a circuit board bore with a width within the usual tolerance limits is sure to find a good, tilt-proof hold and when pressed into the bore certainly does not give rise to any metal forming deformation adhering to the peripheral wall of the bore.

This object is achieved by creating the contact piece according to the invention as defined in claim 1. Advantageous further developments according to the invention result from the dependent claims 2 to 5.

Another object of the present invention is to provide an expedient and relatively simple method for producing the contact piece according to the invention. The method according to the invention which achieves this object is defined in patent claim 6, while advantageous developments of the method result from the dependent claims 7 and 8.

Finally, a further object of the present invention is also to be seen in the creation of a pressing tool which is particularly suitable for carrying out the method according to the invention. The pressing tool which achieves this object according to the invention is defined in claim 9, and preferred further refinements of the same result from the dependent claims 10 and 11.

• Fig. 1 eine perspektivische Darstellung eines ersten Ausfüh­rungsbeispiels des erfindungsgemässen Kontaktstückes zum Einpressen in eine Bohrung einer Leiterbahnen-­Platine;
• Fig. 2 einen Querschnitt entlang der Linie 2-2 in Fig. 1 durch eine der stiftförmigen Endpartien des Kontaktstückes gemäss Fig. 1, in grösserem Massstab;
• Fig. 3 einen analogen Querschnitt entlang der Linie 3-3 in Fig. 1 durch die Einpresspartie des Kontaktstückes;
• Fig. 4 eine der Fig. 3 analoge Schnittdarstellung für den Fall, dass das Kontaktstück in eine Platinenbohrung mit einem an der oberen Toleranzgrenze liegenden Durch­messer eingepresst ist;
• Fig. 5 eine Schnittdarstellung analog der Fig. 4 für den Fall, dass das Kontaktstück in eine Platinenbohrung mit einem an der unteren Toleranzgrenze liegenden Durchmesser eingepresst ist;
• Fig. 6 eine schematisierte Schnittdarstellung einer Vorrich­tung mit einem Presswerkzeug zur Herstelleung des Kon­taktstückes gemäss Fig. 1 durch ein Fliesspress-Ver­fahren;
• Fig. 7 in grösserem Masstab einen Ausschnitt aus Fig. 6, zu­sammen mit einer Querschnittsdarstellung eines in das Presswerkzeug eingelegten Ausgangs-Werkstückes vor Beginn des Fliesspressens;
• Fig. 8 eine der Fig. 7 analoge Darstellung der Teile in einem Zeitpunkt während des Fliesspressens;
• Fig. 9 eine weitere der Fig. 7 analoge Darstellung der Teile am Ende des Fliesspressens;
• Fig. 10 eine perspektivische Darstellung eines zweiten Ausfüh­rungsbeispiels des erfindungsgemässen Kontaktstückes;
• Fig. 11 einen Querschnitt nach der Linie 11-11 in Fig. 10 durch eines der stiftförmigen Endpartien des Kontaktstückes gemäss Fig. 10, in grösserem Massstab;
• Fig. 12 einen analogen Querschnitt nach der Linie 12-12 in Fig. 10 durch die Einpresspartie des Kontaktstückes gemäss Fig. 10;
• Fig. 13 eine der Fig. 12 analoge Querschnittdarstellung für den Fall, dass das Kontaktstück in eine Platinenbohrung mit einem an der oberen Toleranzgrenze liegenden Durch­messer eingepresst ist;
• Fig. 14 eine weitere der Fig. 12 analoge Querschnittdarstellung für den Fall, dass das Kontaktstück in eine Platinen­bohrung mit einem an der unteren Toleranzgrenze liegen­den Durchmesser eingepresst ist;
• Fig. 15 eine der Fig. 9 analoge Querschnittdarstellung einer Ausführungsvariante des Presswerkzeuges und des damit herstellbaren Kontaktstückes.

The invention and its advantages are explained in more detail in the following description of preferred exemplary embodiments with reference to the accompanying drawings. Show it:

• Figure 1 is a perspective view of a first embodiment of the contact piece according to the invention for pressing into a bore in a printed circuit board.
• 2 shows a cross section along the line 2-2 in FIG. 1 through one of the pin-shaped end parts of the contact piece according to FIG. 1, on a larger scale;
• 3 shows an analogous cross section along the line 3-3 in FIG. 1 through the press-in section of the contact piece;
• FIG. 4 shows a sectional illustration analogous to FIG. 3 in the event that the contact piece is pressed into a circuit board bore with a diameter lying at the upper tolerance limit;
• FIG. 5 shows a sectional view analogous to FIG. 4 in the event that the contact piece is pressed into a circuit board bore with a diameter lying at the lower tolerance limit;
• FIG. 6 shows a schematic sectional illustration of a device with a pressing tool for producing the contact piece according to FIG. 1 by means of an extrusion process;
• 7 shows, on a larger scale, a section from FIG. 6, together with a cross-sectional representation of an initial workpiece placed in the press tool before the start of extrusion;
• FIG. 8 shows a representation analogous to FIG. 7 of the parts at one point in time during the extrusion; FIG.
• FIG. 9 shows a further illustration of the parts analogous to FIG. 7 at the end of the extrusion;
• 10 shows a perspective illustration of a second exemplary embodiment of the contact piece according to the invention;
• 11 shows a cross section along the line 11-11 in FIG. 10 through one of the pin-shaped end parts of the contact piece according to FIG. 10, on a larger scale;
• 12 shows an analogous cross section along the line 12-12 in FIG. 10 through the press-in section of the contact piece according to FIG. 10;
• FIG. 13 shows a cross-sectional illustration analogous to FIG. 12 in the event that the contact piece is pressed into a circuit board bore with a diameter lying at the upper tolerance limit;
• FIG. 14 shows a further cross-sectional illustration analogous to FIG. 12 in the event that the contact piece is pressed into a circuit board bore with a diameter lying at the lower tolerance limit;
• 15 is a cross-sectional view analogous to FIG. 9 of an embodiment variant of the pressing tool and the contact piece that can be produced therewith.

The electrical contact piece 20 illustrated in FIGS. 1 to 3 has two pin-shaped end sections 21, 22 and an intermediate press-in section which is formed in cross section 23 on. From Fig. 2 it can be seen that the end portions 21 and 22 have a rectangular, approximately square cross-section. The press-in section 23 is broadened in cross section, as can be clearly seen from FIG. 3 in comparison to FIG. 2. The cross-sectional profile of the press-in section 23 is essentially U-shaped. It has two U-legs 24 and a U-web 25 connecting them to one another. The thickness of the U-web 25 significantly exceeds the thickness of each U-leg 24. On the outer surface 26 of the U-web 25 facing away from the U-legs 24 there is a rib 27 running in the longitudinal direction of the press-in section 23. The outer end parts 27 of the two U-legs 24 facing away from one another are rounded in cross section. The rib 27 also has an end portion 29 which is rounded in cross section. The inner surface 30 of the U-web 25 facing the U-legs 24 runs approximately through the center of an imaginary circle 31 which surrounds the cross section of the press-in section 23 and affects the rounded end parts 28 and 29 of the two U-legs 24 and the rib 27, 3 shows. The entire cross-sectional shape of the press-in section 23 is symmetrical with respect to a plane 32 which runs between the two U-legs 24 and through the rib 27.

At the transition points between the press-in section 23 and each of the rod-shaped end sections 21 and 22, as shown in FIG. 1, there are inclined ramp surfaces 33, 34 and 35 which allow the press-in section to be inserted into a bore 36 in a printed circuit board 37 (FIGS. 4 and 5). facilitate. The diameter of the bore 36 may be within a tolerance of plus or minus about 10% of the nominal diameter vary, but must in any case be smaller than the diameter of the imaginary circle 31 (Fig. 3). If the diameter of the bore 36 is at the upper tolerance limit, the two U-legs 24 are only relatively little elastically bent against each other when the press-in section 23 is inserted into the bore, as shown in FIG. 4. However, if the press-in section 23 is inserted into a bore whose diameter lies at the lower tolerance limit, the two U-legs 24 experience stronger elastic bends relative to one another, as shown in FIG. 5. In both cases, only the surface portions 28 of the U-legs 24 which are rounded in cross section and the end surfaces 29 of the rib 27 which are likewise rounded in cross section come into contact with the inner wall of the bore 36. Since the contact surfaces 28 and 29 have no sharp edges, they are machined Injury to metal plating on the inner wall of the bore 36 practically impossible. The inserted contact piece 20 has a firm, tilt-proof seat in the bore 36, because the three surface portions 28, 29 lying against the inner wall of the bore 36 are distributed along the circumference of the bore. The pin-shaped end parts 21 and 22 of the contact piece 20 serve, for example, as plug pins for connecting plug connectors or as posts for connecting lead wires by soldering or by means of so-called wirewrap technology. In the embodiment variants not shown, the end parts of the contact piece can be designed as a contact knife or contact springs.

The contact piece 20 described is preferably produced according to that illustrated in FIGS. 6 to 9 procedures described below. The shaping of the press-in section 23 takes place by means of non-cutting extrusion with the aid of a press tool, as is shown schematically in FIG. 6. This pressing tool has a stationary stand 41, a pressure bar 42 that can be moved up and down, and a pressing mold 43, 44, 45 consisting of three parts. The latter consists of a two-part die 43, 44 and a movable punch 45. One die part 43 is fastened to the stand 41, while the other die part 44 can be moved up and down with the pressure bar 42. The upper die part 44 in FIG. 6 is arranged to be movable in the pressure bar 42 against the influence of springs 48, which springs 46 allow the upper die part 44 to retreat with respect to the pressure bar 42. The two die parts 43 and 44 together delimit an elongated cavity 47, the shape of which corresponds to the outer shape of the press-in section 23 of the contact piece 20 to be produced. Accordingly, the lower die part 43 has an elongated groove 48 for forming the rib 27 of the press-in section 23. The punch 45 is also guided in a guide recess 49 in the upper die part 44 so that it can be moved up and down so that it can be moved transversely to the longitudinal direction of the cavity 47 in the direction toward the groove 48 and out of the cavity 47. The cavity 47 and the punch 45 are symmetrical with respect to a common plane of symmetry 50.

With the help of the described pressing tool, the press-in contact piece 20 is produced, for example, as follows:

A pin-shaped, prismatic metal piece 51 (FIG. 7) made of a copper alloy is inserted into the opened mold 43, 44, 45, after which the upper die part 44 is pressed against the fixed lower die part 43 by lowering the pressure bar 42 and thus the die 43, 44 is closed, as shown in FIG. 7. Subsequently, the punch 45 is moved downward and pressed into the metal piece 51, as illustrated in FIG. 8. The metal piece 51 is deformed by extrusion, whereby the two U-legs 24 and the rib 27 are formed. At the end of this pressing process, the space between the three parts 43, 44 and 45 of the press mold is completely filled with material of the metal piece 51, as can be seen from FIG. 9. Finally, the punch 45 and the pressure bar 42 with the upper die part 44 are moved up to their starting positions in order to open the mold and to enable the finished contact piece 20 to be removed.

Instead of a metal piece 51 with a square cross section, the contact piece 20 can also be produced from a metal piece with a rectangular or round cross section by extrusion. In any case, the end sections 21 and 22 can be formed at the same time as required, be it as a winding post for the wirewrap technique or as a plug or other connecting link.

The second exemplary embodiment of a press-in contact piece 60 according to the invention shown in FIGS. 10 to 12 differs from that according to FIGS. 1 to 3 only by one somewhat modified cross-sectional shape and due to smaller dimensions. While the first embodiment of the contact piece is intended for insertion into a circuit board bore with a diameter of, for example, 1.0 ± 0.1 mm, the second embodiment is suitable for insertion into a bore with a diameter of, for example, 0.6 ± 0.05 mm . The structural details of the contact piece 60 are completely analogous to those of the first exemplary embodiment 20 and are therefore designated in FIGS. 10 to 12 with the same reference numerals as in FIGS. 1 to 3. It is therefore unnecessary to go into this in more detail. The contact piece 60 is also expediently produced in the same manner and with a similar pressing tool as was described with reference to FIGS. 6 to 9.

When the press-in section 23 is inserted into a bore 36 in a printed circuit board 37, the two U-legs 24 are bent elastically and resiliently in order to give the contact piece 60 the necessary mechanical hold on the printed circuit board. When the diameter of the bore 36 is at the upper tolerance limit of the nominal diameter, the U-legs 24 assume the positions illustrated in FIG. 13. However, if the diameter of the bore 36 is at the lower tolerance limit, the U-legs 24 are bent more strongly against one another, for example as shown in FIG. 14.

It may be expedient to modify the pressing tool used for the production of the contact piece 20 and shown in FIGS. 6 to 9, as shown in FIG. 15. The according to the lower die part 43 has on its surface facing the upper die part 44 two depressions 61 which each run in the longitudinal direction of the cavity 47 and communicate with the latter. When the die 43, 44 is closed, these depressions 61 form, together with the upper die part 44, two groove-like recesses, which make it possible for part of the material of the press-in section 23 to laterally escape into the recesses formed by the depressions 61 in an end phase of the extrusion process after the remaining cavity 47 of the die has been completely filled with material. Due to the laterally escaping material, two additional ribs 62 are produced on the press-in section 23 of the contact piece to be produced, which ribs run in the press-in direction of the contact piece and point away from the plane of symmetry 32 and are each located approximately at the transition between the U-web 25 and one of the U- Leg 24 are. The resulting hardness of the extruded material of the finished contact piece can be influenced and largely adapted to practical requirements by suitable selection of the width of the recesses formed by the depressions 61, measured in the direction of movement of the stamp 45.

Deviating from FIG. 9, the depressions 61 may be present in the upper die part 44 or in both die parts 43 and 44 instead of in the lower die part 43.

Claims (11)

1. Electrical contact piece for pressing into a bore of an electrical printed circuit board, with a press-in part which is resilient transversely to the press-in direction and has an essentially U-shaped cross section, which has two elastically flexible legs and a U-web connecting them to one another, characterized in that in Cross section of the press-in section (23) of the U-web (25) has a thickness exceeding the thickness of each U-leg (24) and, on its outer surface (26) facing away from the U-legs, is provided with a rib (27) running in the press-in direction and that the entire cross-sectional shape of the press-in part of the contact piece lies within an imaginary circle (31) which affects both an end surface (29) of the rib (27) and end surface parts (28) of the two U-legs (24) facing away from one another, which are affected by the imaginary circle (31) tangent surfaces (28, 29), when pressing the contact piece into a hole in Appendix a to reach the inner wall of the bore, the end parts of the two U-legs (24) being elastically yieldingly bent against one another. 2. Contact piece according to claim 1, characterized in that the surfaces (28, 29) of the two U-legs (24) and the rib (28) intended for bearing against the inner wall of the bore are free of sharp edges. 3. Contact piece according to claim 1 or 2, characterized in that the U-web (25) has an inner surface (30) facing the two U-legs (24), which runs at least approximately through the center of the imaginary circle (31). 4. Contact piece according to one of claims 1 to 3, characterized in that the press-in section (23) has a plane of symmetry (32) extending between the two U-legs (24) and through the rib (27) of the U-web (25) . 5. Contact piece according to claim 4, characterized in that the press-in section (23) has two additional ribs (62) each running in the press-in direction without sharp edges, which additional ribs (62) point away from the plane of symmetry (32) of the press-in section and are each approximately in an area between the U-web (25) and one of the legs (24). 6. A method for producing an electrical contact piece for pressing into a bore of an electrical circuit board, with a press-in part resiliently flexible transversely to the press-in direction and having a substantially U-shaped cross section, which has two elastically flexible U-legs and a U-web connecting them to one another , according to one of claims 1 to 5, characterized in that, starting from a pin-shaped metal piece (51) with a full rectangular, square or round cross section, the press-in section (23) is produced by extrusion in a press mold (43, 44, 45) , which has a die (43, 44) with an elongated cavity (47) for inserting the pin-shaped metal piece (51) and a punch (45) which can be moved into and out of the cavity (47) transversely to the longitudinal direction. 7. The method according to claim 6 for producing a contact piece according to claim 5, characterized in that one uses a press mold (43, 44, 45), the cavity (47) and punch (45) are symmetrical with respect to a common plane of symmetry (50 ), and that in each end phase of the extrusion process, part of the material of the press-in section (23) of the contact piece is allowed to move transversely to the direction of movement of the plunger (45) into lateral recesses (61) in the die (34, 44) after the extrusion process the remaining cavity (47) of the press mold (43, 44, 45) has been completely filled with material, the additional ribs (62) of the press-in section (23) being formed. 8. The method according to claim 7, characterized in that the measured in the direction of movement of the punch (45) width of the recesses (61) of the die (43, 44) corresponding to the desired hardness of the extruded material of the finished press-in section (23) of the contact piece chooses. 9. Press tool for performing the method according to one of claims 6 to 8, characterized in that it is a die (43, 44) with an elongated cavity (47) for inserting a pin-shaped metal piece (51) with a full rectangle gene, square or round cross-section and a transverse to the longitudinal direction of the cavity (47) in this and out of the same movable stamp (45). 10. Press tool according to claim 9, characterized in that the die (43, 44) consists of two parts (43, 44) with mutually facing separating surfaces which run in the longitudinal direction of the cavity (47) of the die, and that one (44 ) the parts of the die have a guide recess (48) for the punch (45) and the other part (43) of the die has a groove (48) opposite the punch (45) for forming the rib (27) on the U-web ( 25) of the press-in section (23) of the contact piece to be produced. 11. Press tool according to claim 10, characterized in that at least one of the separating surfaces of the two parts (43, 44) of the die has depressions (61) which, together with the other of the two parts (43, 44) of the die, each have one with the The cavity (47) of the die (43, 44) form a communicating recess, which enables a part of the material of the press-in section (23) to laterally escape into the recesses formed by the depressions (61) in an end phase of the extrusion process, after the rest Cavity of the mold has been completely filled with material.

Images