WO2013023877A1

WO2013023877A1 - Method for pre-deforming a contact pin, use of a pre-deforming device, and contact pin

Info

Publication number: WO2013023877A1
Application number: PCT/EP2012/064350
Authority: WO
Inventors: Juergen Meyer; Thomas Fili
Original assignee: Fci Automotive Holding
Priority date: 2011-07-21
Filing date: 2012-07-20
Publication date: 2013-02-21

Abstract

According to the invention, a method for pre-deforming a contact pin is provided. The contact pin is adapted to be mounted to a printed circuit board. The method comprises the step of providing a contact pin with a fastening portion having two opposite side walls connected with each other by an elastic connecting web. The method further comprises the step of pre-deforming a first part of the fastening portion near the free end of the pin for locally weakening this first part of the fastening portion before the pin is mounted. A remaining part of the fastening portion is thereby not pre-deformed. It is further provided the use of such pre-deforming device for pre-deforming contact pins, and a contact pin for insertion into a hole of a PCB, whereby a first part of a fastening portion of the pin near its free end is pre-deformed for locally weakening the first part of the fastening portion.

Description

METHOD FOR PRE-DEFORMING A CONTACT PIN, USE OF A PRE- DEFORMING DEVICE, AND CONTACT PIN l. Field of the invention

The present invention relates to a method for pre-deforming a contact pin, and in particular to a method for pre-deforming a contact pin by means of a pre-deforming device comprising at least two rotatable rollers and a circumferential guidance. The present invention further relates to a contact pin for insertion into a hole of a printed circuit board (PCB) and to the use of a pre-deforming device for pre-deforming of contact pins.

2. Technical background

Printed circuit boards commonly comprise a number of holes for the insertion of electrical contact pins. The holes are connected to electrical traces of the PCB and the contact pins thus allow for example the connection of parts of the PCB with a connector.

In manufacturing, the contact pins are pressed by force into the holes and held therein due to frictional forces. The insertion forces must not exceed certain values, since otherwise the PCB and/or the pins could be damaged upon insertion of the contact pin into its respective hole. This is even more so the case in mass production, where a large number of contact pins is pushed by the same automated tool together into a PCB.

On the other hand, the insertion forces must not go below certain values, as when the insertion forces are too small, then the retention forces of the inserted pins are also too small and the pins may become loose.

During insertion of a contact pin into a hole of a PCB, commonly first an increase of the press-in force up to a maximum force is present, followed by a decrease of the force. The final force corresponds essentially to the pull-out or retention force of the contact pin in the PCB hole. With many contact pins, the maximum force is reached shortly before the contact pin is plastically deformed at a predetermined breaking point to prevent an easy release of the contact pin from the PCB.

To prevent a plastic deformation or destruction of the PCB and/or of the PCB hole leading to an affected electrical and mechanical connection between the contact pin and the PCB, an optimization of the

performance of the contact pin should preferably lead to a smaller maximum press-in force and to a larger retention force of the contact pin.

A typical prior art document dealing with such an optimization of the performance of a contact pin is the US 4,867,710 A. This document discloses a pin-shaped contact element with an insertion region with two parallel side parts that can move elastically towards one another. The elasticity of this insertion region is increased by providing an opening in the insertion region which runs transversely to the connecting web of the side parts and interrupts this connecting web in the transition region to the lower end of the pin.

However, the manufacture of this contact pin with the opening(s) in the connecting web of the side parts of the pin is quite elaborate and expensive, since each pin has to be drilled at exactly the correct position, whereby tight tolerances have to be observed.

Although neither the contact pins nor the PCBs are expensive components, they are mass products and have therefore a considerable influence on the production quality and the production costs of a large number of products. Therefore, it is important to optimize the manufacture of such contact pins to reduce the manufacture costs while, at the same time, securing a tight and sufficient fit in a PCB. Therefore, it is an object of the present invention to improve the above described situation by providing an improved method for manufacturing a contact pin, and in particular a manufacturing method with reduced manufacturing steps and costs. It is a further object of the present invention to provide an improved contact pin, and in particular a pin which can be manufactured with reduced number of steps and costs.

These and other objects which become apparent upon reading the following description are solved by a method according to claim l, the use of a pre-deforming according to claim 17 and a contact pin according to claim 18.

3. Summary of the invention According to the invention, a method for pre-deforming a contact pin is provided. The contact pin is adapted to be mounted to a printed circuit board. The method comprises the step of providing a contact pin with a fastening portion and the step of pre-deforming a first part of the fastening portion near the free end of the pin for locally weakening this first part of the fastening portion before the pin is mounted. Thus, the remaining part of the fastening portion is not pre-deformed. By this pre- deformation the maximum press-in force can advantageously be reduced, while at the same time the retention force is not or only minimally affected thereby. Thus, it is important that only a part of the fastening portion is pre-deformed, and not the whole fastening portion, since otherwise the retention force would undesirably also be reduced.

According to the invention, the fastening portion of the contact pin comprises two opposite side walls connected with each other by an elastic connecting web, similar to the prior art disclosed in US 4,867,710 A. The fastening portion may be produced e.g. by stamping. Preferably, the first part of the fastening portion constitutes between 10 % and 70 % of the overall length of the fastening portion, preferably between 15 % and 60 %, more preferably between 20 % and 55 % and most preferably between 30 % and 50 %. In other words, the pre-deforming does not affect the entire longitudinal extension of the fastening portion.

As a result, the method for pre-deforming a contact pin according to the invention leads to a smaller maximum force and to a larger retention force of the contact pin. Thereby, a plastic deformation or destruction of the PCB and/or of the PCB hole leading to an affected electrical and mechanical connection between the contact pin and the PCB and a loosening of the pins is prevented.

The pre-deforming may comprise a pre-pressing, pre-stamping, pre- breaking or the like. Preferably, the pre-deforming of the first part of the fastening portion however comprises the further steps of providing a dedicated pre-deforming device and inserting the contact pin into the pre-deforming device. The pre-deforming device of the invention comprises at least two rotatable rollers arranged adjacent and axially parallel to each other and a circumferential guidance as part of at least one of the rollers. The pre-deforming by this device, and in particular by the rollers, enables an easy and comfortable processing of the contact pin without the necessity for any tight tolerances. Compared to the prior art, the step of creating openings in the fastening portion is omitted, leading to reductions in manufacturing time, steps and costs.

Further preferably, the guidance of the pre-deforming device may be formed by a circumferential groove provided on the surface of the roller(s). For an increased stability, each rotatable roller may comprise a circumferential guidance and the circumferential guidances are then arranged adjacently to interact with each other.

Further preferably, the pre-deforming device may further comprise a supporting structure for the rollers in the form of at least four additional rotatable support cylinders. Thereby, also the stability and the amount of transmittable force are increased. The four support cylinders may be arranged axially parallel to the rotatable rollers and may be in contact with at least one of the rotatable rollers. Respective two of the support cylinders may then be in contact with one roller, such that the axes of the roller and the two support cylinders being in contact therewith form a triangle.

When inserting the contact pin into the pre-deforming device, the contact pin is preferably inserted into the circumferential guidance to such an extent that the first part of the fastening portion pre-deforms. Further preferably, the pin is only partially inserted into the pre- deforming device, such that only said first part to be deformed of the fastening portion is inserted between the at least two rollers. Preferably, the pre-deforming comprises a deformation of the connecting web to enable an approach of the sidewalls to each other. Further preferably, the pre-deforming comprises a breaking of a part of the connecting web to enable an approach of the sidewalls to each other. The breaking of the part of the connecting web may also lead to a superposition of the broken parts of the web in the affected area.

After the pre-deforming, the fastening portion may comprise a cross- section with two semi-circular concave elements being arranged opposite to each other or a cross-section shaped as a "bow-tie".

According to the invention, it is further provided the use of a pre- deforming device for pre-deforming of contact pins, and a contact pin for insertion into a hole of a PCB, whereby a first part of a fastening portion of the pin near its free end is pre-deformed for locally weakening the first part of the fastening portion. 4. Description of the preferred embodiments

In the following, the invention is described exemplarily with reference to the enclosed figures in which:

Fig. 1 shows a force-distance-progress diagram;

Fig. 2 shows different illustrations of a fastening portion of a contact pin,

Fig. 3 shows subsequent cross-sections 1 to 7 of a pre-deformed first part of the fastening portion as indicated by cutting lines 1 to 7 in Fig. 2,

Fig. 4 shows a schematic illustration from a slightly oblique angle of a pre-deforming device;

Fig. 5 shows an explosion view of the device of Fig. 4 with a partially omitted housing;

Fig. 6 shows a perspective view of the device of Fig. 4 with omitted housing;

Fig. 7 shows a further perspective view of the device of Fig. 4 with omitted housing, and

Fig. 8 is a schematic illustration of an embodiment similar to the embodiment of Fig. 5 comprising four rollers.

Figure 1 shows an exemplary force-distance-progress diagram depicting in curve a) the detected force for insertion of a prior art contact pin without a pre-deformed fastening portion into a hole of a PCB over the insertion distance. As can be seen in Fig. 1, during insertion of the contact pin from the first touch to maximum, the force first increases over a distance of only 2.65 mm up to a maximum force of nearly 70 N, followed by a decrease of the force from the maximum force to an intermediate force of 35 N. This decrease of the force is due to a plastic deformation or partial breaking of the fastening portion of the inserted pin, which occurs in the shown example at the maximum force of 70 N. After breaking or deformation the insertion force slightly increases again upon further insertion of the pin into the PCB, mainly due to the increased friction. The end force of 53 N is reached at the end of the insertion process. The force at the end of the insertion process corresponds essentially to the retention force, i.e. the force necessary to pull the pin again out from the hole.

Curve b) shows the corresponding force for insertion of a contact pin according to the invention. As one can see, the maximum force reached before (full) breaking or plastic deformation of the pre-deformed fastening portion is only 51 N and thus considerably lower than the maximum force of the prior art pin Therefore, the PCB, respectively the hole of the PCB, is less susceptible to damages or wear-out. However, the end force and thus the retention force if basically identical to the prior art pin. Indeed, in practise, namely when the hole of the PCB is slightly damaged, the retention force of the inventive pin is substantially higher than that of the prior art pins.

Thereby, according to the invention, an optimization of the performance of the contact pin is achieved leading to a smaller maximum force and a larger or at least comparable retention force of the contact pin. Thereby, a plastic deformation or destruction of the PCB and/or of the PCB hole leading to an affected electrical and mechanical connection and thus the undesired discarding of damaged parts can be prevented. According to the invention, this optimization of the performance of the contact pin 3 is achieved by pre-deforming (only) a first part 34 of a fastening portion 30 of the contact pin 3 near the free end 33 of the pin 3 for locally weakening this first part 34 of the fastening portion 30. To further explain the concept of the present invention, Fig. 2 shows different views of the fastening portion 30 of the contact pin 3 before pre-deformation. As one can see, the fastening portion 30 comprises two opposite side walls 31 connected with each other by an elastic connecting web 32. The first part 34 of the fastening portion 30 near the free end 33 of the pin 3 is shown in Fig. 2 on the left. The fastening portion 30 may be produced by e.g. stamping.

After a pre-deformation of the first part of the fastening portion, the pin 3 was cut at various points 1 to 7 in a plane perpendicular to the longitudinal direction, to allow the examination of the respective cross- sections 1 to 7. In Fig. 3 pictures of the seven cross-sections are shown.

As one may derive from Figs. 2 and 3, the pre-deformation affected the fastening portion from the beginning thereof at section 1 up to section 6. In the pictures 1 to 6 of Fig. 3, the web 32 is broken and the broken parts 32a, 32b partially superimpose each other. However, section 7 is not affected by the pre-deformation, since the web 32 is still intact in this area. Thus, in the shown example only approximately 40 % of the overall length of the fastening portion 30 is pre-deformed, whereas the remaining part of the fastening portion 30 is not pre-deformed, i.e. the rear part beginning at approximately section 6 is not pre-deformed.

One can further derive from Fig. 3 that the fastening portion 30 tapers towards its free end 33 (to the left in Fig. 2) and that the surface area of the cross-sections of the fastening portion 30 correspondingly increase from section 1 to section 7. The fastening portion 30 has a cross-section comprising two essentially semi-circular concave elements. This cross- section thus has the general shape of a "bow-tie".

The pre-deforming of the fastening portion 30 comprises in particular a deformation of the connecting web 32 leading to an approach of the side walls 31 to each other. This effect is strongest in the cross-sections 2 to 5, where the pre-deforming leads to a breaking of the connecting web 32 and thus to a further approach of the side walls 31 to each other. As mentioned above, also in particular shown in the cross-sections 2 to 5, the breaking of the connecting web 32 leads to a superposition of the broken parts 32a, 32b of the web 32.

The pre-deforming of the contact pin 3 can be done for example by pre- pressing, pre-stamping, pre-breaking or the like. However, preferably the pre-deforming is achieved by a device 1 as described below under reference to Figs. 4 to 8:

As can be taken from the oblique angled schematic view of Figure 4 the contact pin 3 is an electrical contact pin 3 comprising a contact end 15 with a press-fit zone or fastening portion 30. Further, the contact pin 3 comprises a stop portion 17 which in practise prevents the pin 3 from being inserted too far into the hole of a PCB. The device 1 serves for pre- deforming (only) the first part 34 of the fastening portion 30 near the free end 33 of the pin 3 for locally weakening this first part 34 of the fastening portion 30, before the pin 3 is mounted into a PCB. As will be described in more detail in the following, to this end, the pin 3 is partially inserted into the pre-deforming device 1, such that only said first part 34 to be deformed of the fastening portion 30 is inserted and deformed between two deformation-rollers.

The pre-deforming device 1 comprises a housing 9 rotatably supporting two rollers 5a and 5b, which are arranged adjacent and axially parallel to each other. The housing is made from two halves 9a and 9b, which are arranged slidable on a frame 18. The frame 18 allows for an adjustment of the distance of the two housing halves from each other and thus of the two rollers 5a and 5b. The two halves 9a and 9b can be moved on the frame 18 in a direction as indicated by the double-headed arrow and fixed in position on the frame by appropriate fixing means as e.g. screws (not shown). Thereby it is possible to adjust the pre-deforming device 1 to differently sized pins 3, respectively differently sized fastening portions 30. The halves 9a and 9b are made from two rigid steel plates having a thickness of e.g. 3 to 4 mm. The thickness of the metal plates ensures that the whole arrangement is extremely rigid so that the two rollers 5a and 5b are not pushed away from each other upon inserting of the pin 3 therebetween.

The rollers 5a, 5b are further rotatably supported by a supporting structure in the form of four support cylinders 11a, lib, 11c, and lid. As can be taken from figures 3 and 5, the cylinders are each in contact with one roller and prevent a bending or buckling of the rollers upon insertion of the pin 3, thereby further improving the rigidity of the arrangement.

As a result, the pre-deforming device 1 can be used for pre-deforming the first part 34 of the fastening portion 30 near the free end 33 of the pin 3 for locally weakening this first part 34 of the fastening portion 30, before the pin 3 is mounted.

Figure 5 shows an exploded view of the pre-deforming device 1 shown in figure 4. The housing half 9a comprises circular openings 13 to receive shafts 12 integrally formed with the support cylinders 11a, 11b, 11c, nd. For assembly, the two plates forming housing half 9a can be

disassembled and the shafts 12 of cylinders 11a and 11c are inserted in the respective circular openings 13. Further, a roller 5a is arranged in the semi-circular cut-out 14. After that, the two metal plates of the housing half 9a are for example screwed together and mounted to the frame 18. In figure 3, one can further see the circumferential guidance 7, which in the embodiment shown in the figures is provided in form of a groove with semi-circular cross-section, which groove is cut into the respective outer surface of the two rollers 5a and 5b. Generally, it is preferred that the diameter of the groove(s) is adapted to the diameter or shape of the fastening portion 30, such that a controlled pre-deformation can be achieved. In the shown embodiment, each of the two rollers 5a and 5b comprises a groove and the two grooves (i.e. the circumferential guidances) are arranged adjacently with each other to interact with each other. In other words, upon inserting of the contact pin 3, the pin 3 is guided from two opposed sides by the respective guidance 7 of the left hand roller 5a and the respective guidance 7 of the right hand roller 5b. Thereby, the two grooves correspond to the through-hole of a PCB and allow the controlled pre-deformation of the first part of the fastening portion 30.

In all the inventive embodiments, it is generally preferred that the diameter ds of the support cylinders 11a, 11b, 11c, and nd is larger than the diameter dR of the rotatable rollers 5a and 5b (cf. to Fig. 5).

Preferably, the diameter ds of the support cylinders is larger by a factor of at least 1.3, preferably at least 1.6, more preferably at least 1.8 and most preferably 2.0 in comparison to the diameter of the rollers dR. Thus, if the diameter of the roller dR is e.g. 10 mm, the diameter ds of the supported cylinders is preferably at least 13 mm, preferably at least 16 mm, more preferably at least 18 mm and most preferably at least 20 mm. To offer an improved support, the support cylinders should be in direct contact with one roller, such that the axes of the roller and the two support cylinders being in contact therewith form a triangle. Preferably, in all the embodiments in accordance with the invention, the angle γ (confer to figure 5) at the edge of the triangle formed by the arms between the axis of the roller and the axes of the two contacting support cylinders exceeds 8o°, preferably 90⁰ and most preferably 100⁰.

Figures 6 and 7 show different perspective views of the rollers, support cylinders and the contact pin 3, whereby the housing is omitted. Figure 6 shows a schematic top view of the arrangement of the different rollers and cylinders. As one can derive from figure 6, the length of the support cylinders (including the shafts 12) is approximately equal to the length of the rollers 5a and 5b. Thereby, a compact design of the device 1 can be achieved. In figure 7 it is shown how the contact pin 3 is inserted between the two adjacent rollers 5a, 5b through the circumferential guidances 7. Since the whole construction is very rigid and due to the rotational arrangement of the rollers a controlled pre-deformation can be obtained in a secure and repeatable manner in mass production. In many instances, the contact pins are plated with a suitable electroconductive material. The advantageous rotational arrangement of the rollers reduces the friction upon insertion of a pin, such that the plating is not scrubbed off. Still further, the reduced friction leads to a considerably reduced wear of all involved components, including the pre-deforming device itself but also the auxiliary equipment like for example the devices used for pushing the pins (partially) into the pre- deforming device.

Fig. 8 is a schematic illustration showing the arrangement of four rollers 5¾_> 5b, 5C and sd. As one can derive from the illustration, the four rollers are arranged pair-wise adjacent and axially parallel to each other.

Similar to the embodiment with two rollers shown in Figs. 4 to 7, four support cylinders 11a, 11b, 11c and nd are provided contacting and supporting the rollers. Although the housing is not shown in Fig. 6, the skilled person will recognise that the construction thereof can be identical to the construction of the embodiment with two rollers but with a second semi-circular cut-out 14 in each metal plate of the housing for reception of the respective third and fourth roller 5c and sd. In a similar way, it is of course also possible to provide further pairs of rollers if particularly long contact pins 3 have to be tested and the invention is thus not limited to embodiments with exactly two rollers.

Claims

Method for pre-deforming a contact pin (3), which contact pin (3) is adapted to be mounted to a printed circuit board (PCB), comprising the following steps:

- providing a contact pin (3) with a fastening portion (30) having two opposite side walls (31) connected with each other by an elastic connecting web (32),

- pre-deforming a first part (34) of the fastening portion (30) near the free end (33) of the pin (3) for locally weakening this first part (34) of the fastening portion (30), before the pin (3) is mounted to a PCB, wherein a remaining part of the fastening portion (30) is not pre-deformed.

Method according to claim 1, wherein the pre-deforming of the first part (34) of the fastening portion (30) comprises the following steps:

- providing of a pre-deforming device (1), wherein the device (1) comprises at least two rotatable rollers (5a, 5b) arranged adjacent and axially parallel to each other, wherein at least one of the rollers (5a, 5b) comprises a circumferential guidance (7),

- inserting the contact pin (3) to such an extend into the circumferential guidance (7) so that the first part (34) of the fastening portion (30) pre-deforms, and

- removing the contact pin (3) before the remaining part of the fastening portion (30) is pre-deformed.

Method according to claim 2, wherein the guidance (7) is formed by a circumferential groove provided on the surface of the roller(s) (5a, 5b).

Method according to claim 2 or 3, wherein each rotatable roller (5¾; 5b) comprises a circumferential guidance (7) and wherein the circumferential guidances (7) are arranged adjacently to interact with each other.

Method according to one of the claims 2 to 4, wherein the pre- deforming device (1) further comprises a supporting structure for the rollers (5a, 5b) in the form of at least four additional rotatable support cylinders (11a, lib, 11c, lid), the four support cylinders (11a, 11b, 11c, nd) being arranged axially parallel to the rotatable rollers (5a, 5b) and each being in contact with at least one of the rotatable rollers (5a, 5b).

Method according to the preceding claim, wherein respective two of the support cylinders (11a, 11b, 11c, nd) are in contact with one roller (5a; 5b), such that the axes of the roller (5a; 5b) and the two support cylinders (11a, 11b, 11c, nd) being in contact therewith form a triangle.

7. Method according to one of the claims 2 to 6, wherein the pin (3) is only partially inserted into the pre-deforming device (1), such that only said first part (34) to be deformed of the fastening portion (30) is inserted between the at least two rollers (5a, 5b).

Method according to any one of the preceding claims, wherein the pre-deforming comprises a deformation of the connecting web (32) enabling the sidewalls (31) to become closer each other.

Method according to any one of the preceding claims, wherein the pre-deforming comprises a breaking of a part of the connecting web (32) enabling the sidewalls (31) to become closer each other.

Method according to the preceding claim, wherein the breaking of the part of the connecting web (32) leads to a superposition of the broken parts (32a, 32b) of the web (32) in the affected area. Method according to any one of the preceding claims, wherein the first part (34) of the fastening portion (30) constitutes between 10 % and 70 % of the overall length of the fastening portion (30), preferably between 15 % and 60 %, more preferably between 20 % and 55 % and most preferably between 30 % and 50 %.

Method according to any one of the preceding claims, wherein the pre-deforming affects not the entire longitudinal extension of the fastening portion (30).

Method according to any one of the preceding claims, wherein the pre-deforming comprises a pre-pressing, pre-stamping, pre- breaking or the like.

Method according to any one of the preceding claims, wherein the fastening portion (30) comprises a cross-section with two essentially semi-circular concave elements being arranged opposite to each other.

Method according to any one of the preceding claims, wherein the fastening portion (30) comprises a cross-section essentially shaped as a "bow-tie".

Method according to any one of the preceding claims, wherein the fastening portion (30) is produced by stamping.

Use of a pre-deforming device (1) for pre-deforming of contact pins (3),

wherein the device (1) comprises at least two rotatable rollers (5a, 5b) arranged adjacent and axially parallel to each other, and a circumferential guidance (7) in at least one of the rollers (5a, 5b), and wherein a first part (34) of a fastening portion (30) of the contact pin (3) is pre-deformed in the guidance (7) when the at least two rollers (5a, 5b) are rotating.

Contact pin (3) for insertion into a hole of a PCB, comprising a fastening portion (30) having two opposite side walls (31) connected with each other by an elastic connecting web (32), whereby a first part (34) of the fastening portion (30) near the free end (33) of the pin (3) is pre-deformed for locally weakening the first part (34) of the fastening portion (30) and the remaining part of the fastening portion (30) is not pre-deformed.