WO1999044260A1

WO1999044260A1 - Contact strip for connecting two circuit boards and a process for producing the contact strip

Info

Publication number: WO1999044260A1
Application number: PCT/IB1999/000324
Authority: WO
Inventors: Gerardus Maria Van Alst; Marcus Mybrand Wilhelmus Gosselink; Lucas Soes
Original assignee: Whitaker LLC
Current assignee: Whitaker LLC
Priority date: 1998-02-25
Filing date: 1999-02-23
Publication date: 1999-09-02
Anticipated expiration: 2000-08-25
Also published as: KR20010041021A; JP2002505513A; AU2296199A

Abstract

A contact strip for the electrical and mechanical connection of two mutually perpendicular circuit boards (1, 2) consists of an insulating receiving member in the form of a strip (3) and a plurality of contact elements (8) with a respective transition zone (9) extending in the strip (3). Two contact zones (10, 10') adjoin the transition zone (9) for electrical connection to a first and a second circuit board (1, 2). The strip (3) is essentially an elongate plastic member (4) with a T-shaped cross section having a carrier web (7) and two identical transverse arms (5, 6). The plastic member (4) is arranged as a T at an angle bisecting the angle between the circuit boards (1, 2) extending perpendicularly to one another.

Description

- 1-

CONTACT STRIP FOR CONNECTING TWO CIRCUIT BOARDS AND A PROCESS FOR PRODUCING THE CONTACT STRIP

The invention relates to a contact strip for the electrical and mechanical connection of two mutually perpendicular circuit boards and a process of making the contact strip.

A contact strip of this type is known, for example, from DE-OS 14 90 440. This contact strip consists of an elongate plastic block in which a plurality of differently shaped contact elements are arranged. Each of the contact elements are inserted with a transition zone in the plastic block. The contact elements each have a first resilient contact zone which protrudes from one of the longitudinal sides of the plastic block and contacts a conductor track of a first circuit board. The second contact zone protrudes from the second longitudinal sides of the plastic block extending perpendicularly thereto and are connected through a hole to conductor tracks of a second circuit board arranged perpendicularly to the first circuit board. Production of the various contact elements and of the plastic block as well as the assembly of the contact strip are therefore complicated.

Starting from this state of the art, it is an object of the invention to provide a contact strip for the electrical and mechanical connection of two mutually perpendicular circuit boards, the contact strip being composed of as few different parts as possible and the contact strip being as versatile as possible. With regard to the contact strip, this object is achieved with a contact strip having the characteristics of claim 1. -2-

The contact strip is arranged as a T along the angle bisecting the angle between the mutually perpendicular circuit boards. The contact elements are arranged with a central transition zone symmetrically to the bisecting angle in the transverse arms of the T-shaped plastic member of the contact strip. The symmetrical arrangement results in the contact strip having a form which is simple to produce and has high stability. With a large number of contact elements which all extend side by side in the transition zone, at an angle of 45° to the circuit boards, the contact strip represents the shortest connection between the circuit boards. By freely selecting the position of the bending points between the transition zone and the contact zones of the contact elements, the .contact strip can be adapted to the spacing between rows of contact points on different circuit boards. The arrangement of an odd number of contact elements in a contact strip produces a configuration which, after a rotation of every second contact strip through 180°, can be aligned to form a contact strip of desired length, the modular dimension of the contact points on the circuit boards being utilised without wasting space.

Advantageously, the contact strip requires a minimum amount of space. This is achieved as the strip essentially has a T-shaped cross section when viewed from an end thereof with a carrier web from which two identical transverse arms extend, such that transition zones of a contact extend along the transverse arms and the carrier web is arranged at an angle bisecting the angle between the transverse circuit boards.

It is of further advantage that the contact strip is highly stable. This is achieved because all transition zones of the contact elements extend in parallel to the transverse arms of the T-shaped cross section of the strip. -3-

This is also achieved in that the ends of the transverse arms and of the carrier arm of the T-shaped strip have angled support surfaces for supporting the circuit boards.

It is of further advantage that the contact elements of the contact strip are simple to produce. This is achieved in that all contact elements may have the same electrically conducting length.

It is also of advantage that the contact strip can be used for various configurations of circuit boards. This is because all contact zones of the contact elements can be arranged side-by-side on one longitudinal side of the strip to have bending points which are arranged identically or in an alternating manner.

It is also of advantage that the contact strip can be modular in design in that the strip receives an odd number of contact elements and has a length corresponding to a multiple of the spacing between the contact elements.

Embodiments of the invention will now be described with reference to the drawings, in which: Figure 1 is a perspective view of a contact strip connected to two mutually perpendicular circuit boards;

Figure 2 shows the contact strip of Figure 1;

Figure 3 is a section through the assembly of Figure 1; Figure 4 is a view of the underside of the contact strip of Figure 2;

Figure 5 is a section through the contact strip along line A-A of Figure 4;

Figure 6 is a section through the contact strip along line B-B of Figure 4;

Figure 7 shows a second embodiment of a contact strip connected to two mutually perpendicular circuit boards; - 4 -

Figure 8 shows the contact strip shown in Figure 7;

Figure 9 is a section through the assembly shown in Figure 7;

Figure 10 is a view of the underside of the contact strip shown in Figure 8;

Figure 11 is a section through the contact strip along line C-C of Figure 10;

Figure 12 is a section through the contact strip along line D-D of Figure 10; Figure 13 is an exploded perspective view of two contact strips and a detail of a circuit board;

Figure 14 is an exploded perspective view of a contact strip and a detail of a circuit board;

Figure 15 is an exploded perspective view of a further contact strip and a circuit board;

Figure 16 is an exploded perspective view of a further contact strip and a further circuit board; and

Figure 17 is a perspective view of the contact strip according to the invention in the successive phases of the production process.

Figure 1 shows two mutually perpendicular circuit boards 1, 2 which are mechanically and electrically connected by a contact strip 3 according to the present invention. The contact strip 3 consists of an elongate plastic member 4 with a T-shaped cross section. The plastic member 4 comprises transverse arms 5, 6 alternating with a carrier web 7. In this embodiment, five identical contact elements 8 are arranged side-by-side in the elongate plastic member 4. The contact elements 8 each consist of a transition zone 9 disposed in the transverse arms 5, 6 and two contact zones 10, 10' bent away therefrom at an angle of 45°. The contact zones 10, 10' are inserted in holes 11, - 5-

11' in the respective circuit boards 1, 2. Contact can be made with plated through holes 11, 11'. The contact zones 10, 10' are designed, at least in the zone of the holes 11, 11', such that a good electrical and mechanical connection is produced between the contact strip 3 and the circuit boards 1, 2. In order to improve the electrical contact properties, the contact zones 10, 10' can be coated with tin or silver alloys. The connection between the contact zones 10, 10' and the circuit boards 1, 2 can be produced by an interference fit or solder connection. It is also possible for the contact zones 10, 10' to be soldered directly to solder pads on the circuit boards 1, 2.

Figure 2 shows another view of contact strip 3, but without the circuit boards 1, 2. It can be seen how the contact zones 10, 10' have a specific shape, for example an additional bending point, for engagement with the circuit boards 1, 2.

Figure 3 is a sectional view of the assembly of Figure 1. The transverse arms 5, 6 and the carrier webs 7 include support surfaces 12, 12' which are bevelled at their respective ends. The support surfaces 12, 12' are arranged such that the mutually perpendicular circuit boards 1, 2 are each supported at several points. This increases the mechanical stability of the assembly. Each circuit board 1, 2 cooperates with the contact strip 3 in three different zones in the longitudinal direction of the contact strip 3: firstly, in the contact zone; secondly, in the zone of the support surfaces 12 at the respective end positions of the transverse arms 5, 6; and thirdly, in the zone of the support surfaces 12' at the end of the carrier web 7.

Figure 4 illustrates the contact strip 3 of Figure 2 as viewed from the underside. It can be seen how the bevelled support surfaces 12, 12' are formed at the ends of the transverse arms 5, 6 and in certain regions at the end - 6-

of the carrier web 7. The carrier web 7 does not extend in a rectilinear manner but in a zigzag line in the longitudinal direction of the contact strip 3. Maximum stability through a minimum amount of material is achieved by the zigzag arrangement and the arrangement of the support surfaces 12' at the end of the carrier web 7. The carrier web 7 is provided with support surfaces 12' only in the positions where a supportive action is required for the circuit boards 1. The contact elements 8 comprise two respective contact zones 10, 10' and a transition zone 9. The transition zone 9 extends, in certain regions, through the transverse arms 5, 6 formed, for example, by plastic injection moulding around the contact elements 8. The contact elements 8 can then be separated from one another by a stamping operation.

Figure 5 is a sectional view of the contact strip 3 shown in Figure 4 along line A-A. It can be seen how the contact strip 3 consists of a plastic member 4 with a T- shaped cross section and a plurality of contact elements 8 arranged in a plane.

Figure 6 illustrates a further section of the contact strip 3 shown in Figure 4 along line B-B. It can be seen how a contact element 8 comprises a transition zone 9 and two contact zones 10, 10' respectively. The contact zones 10, 10' are bent away at an angle of 45° from the plane of the transverse arms 5, 6. This causes the contact zones 10, 10' on the mutually opposed longitudinal sides of the contact strip 3 to extend at an angle of 90° to one another. The plastic member 4 is arranged with the carrier web 7 along the angle bisecting the angle between the two circuit boards 1, 2, and the contact zones 10, 10' are orientated perpendicularly to the respective circuit board 1, 2. -7-

Figures 7 to 12 illustrate a second embodiment of the contact strip 3. The same reference numerals relate to the same elements of the assembly. The difference between the contact strip 3 shown in Figures 1 to 6 and the contact strip 3 shown in Figures 7 to 12 is that the contact zones 10, 10' are bent in a different manner from the plane of the transverse arms 5, 6. However, the plastic member 4 is the same in the two embodiments . By bending the contact elements 8 in a different manner, the same contact elements 8 can be used for a different configuration of the circuit boards 1, 2 while still retaining the same electrical length. Figures 7 and 9 show how the holes 11, 11' in the circuit boards 1, 2 are arranged in two mutually spaced apart rows. It can also be seen in Figure 9 that the spacing of the rows of holes 11, 11' is smaller on the first circuit board 1 than on the second circuit board 2. The contact strip 3 in the embodiment shown in Figure 7 to 12 is produced using the same material and the same tools as in the embodiment in Figures 1 to 6. The processing steps during production are also substantially the same. Only the tools required for bending the contact zones 10, 10' have to be exchanged. By selecting the position of the bending point between the transition zone 9 and the contact zones 10, 10', the contact strip 3 can be adapted to the respective configuration of the circuit boards 1, 2.

Figures 13 to 16 show how the contact strip 3 can be used for various configurations of the circuit boards 1, 2. Figure 13 shows two contact strips 3, 3' each with five contact elements 8 arranged directly side by side. The holes 11, 11' are shown in the circuit board 2 in two rows, each comprising five holes 11, 11'. This shows that the contact strip 3, 3' can make contact with as dense an arrangement as possible of holes 11, 11' in the circuit boards 1, 2. Figure 14 shows a contact strip 3 with five contact elements 8 pre-orientated relative to a further circuit board 2' with five holes 11, 11'. The view in Figure 14 can be derived from the view in Figure 13 by omitting the second contact strip 3' and the five associated holes 11, 11* .

Figure 15 shows how the second contact strip 3' in Figure 13 can also be used relative to the same circuit board 2' of Figure 14. The contact strip 3' shown in Figure 15 is identical with the second contact strip 3' shown in Figure 13, but has been rotated through 180°. After rotation through 180°, the configuration of the plastic member 4 and the arrangement of contact elements 8 of the second contact strip 3 is completely identical with the configuration of the first contact strip 3.

Figure 16 illustrates the second contact strip 3' pre- orientated relative to a further circuit board 2". It is indicated in the illustrations in Figures 13 to 16 that the contact strips 3, 3' can be used for a plurality of different circuit boards 2, 2', 2" without wasting space.

The contact strips 3, 3' each comprise an odd number of contact elements 8, for example five. The contact elements 8 are each bent differently in the first contact zone 10 and in the second contact zone 10'. Owing to the different position of the bending point in the first and in the second contact zone 10, 10' of each contact element 8 and owing to the alternate arrangement of the adjacent contact elements 8, the first and second contact zones 10, 10' form two rows on each longitudinal side of the contact strip 3, 3'. The first contact zones 10 of three of the five contact elements 8 on a first longitudinal side of the contact strip 3 are located in a first row, for example an internal row. In this embodiment, the bending points have been located further inwards towards the centre line of the - 9-

plastic member 4 of the contact strip 3. On the second, opposing longitudinal side of the contact strip 3, the opposing bending points of these three contact elements 8 have been located further outward from the centre line of the plastic member 4.

The two additional contact elements 8 are arranged alternately between the first three contact elements 8. The second contact zones 10' of these two contact elements 8 are located in the second outer row on the first longitudinal side of the contact strip 3. The opposing bending points of these two contact elements 8 have been located further inwards towards the plastic member 4 on the second opposing longitudinal side of the contact strip 3. If the spacing between rows is selected so as to be identical on the two longitudinal sides of the contact strip 3, a further contact strip 3 which also has five contact elements 8 can be connected directly after the first contact strip 3 to the contact points of the circuit board, after a rotation through 180°. An upper contact strip with a desired length for connection of the circuit boards can be constructed in this way with a single configuration of the contact strip 3, without wasting space in the modular dimension of the contact points.

The process for producing a contact strip for connecting two mutually perpendicular circuit boards will now be described with reference to Figure 17. Initially, a metal grid 31 with carrier rails 32 and a plurality of contact elements 8 located transversely to the strip direction is punched from a metal strip 30. The carrier rails 32 extend in the longitudinal direction of the metal strip 30 and are arranged equidistantly from the centre of the strip 30.

In a next step of the process, the metal grid 31 can be coated electrolytically in the contact zones 10, 10'. - 10-

Electrolytic coating leads to the deposition of one or more layers of metal composed, for example, of tin, silver or gold. After the coating process, the metal grid 31 is injection moulded with a non-conductive plastic material on both sides of the strip 30 in a transition zone 9 between the carrier rails 32. The carrier rails 32 can be used in part to seal the injection moulding tool during an injection moulding process. An elongate strip 33 is produced by plastic injection moulding and has a substantially T-shaped cross section comprising two transverse arms 5, 6 which receive the transition zones 9 of the contact elements 8, and a carrier web 7 which extends perpendicularly to the transverse arms 5, 6, as in the letter T. The carrier rails 32 and, in certain regions, the plastic material are removed from the strip 33 in a further step of the operation. As a result, individual electrically separated contact elements 8 are formed from the metal grid 31, and a gap 34 is formed in the longitudinal side of the strip 33 for the bending of every second contact element 8.

The contact zones 10, 10' are then bent away at an angle of 45° from the plane of the transverse arms 5, 6 of the T-shaped strip 33. The contact zones 10, 10' of each individual contact element 8 essentially are mutually perpendicular in such a way that the contact zones 10, 10' are orientated perpendicularly to the circuit boards. In the bending tool, the position of the bending points between the transition zone 9 and the contact zones 10, 10' can be selected differently according to the configuration of the respective circuit board.

The T-shaped strip 33 is separated in the longitudinal direction into individual contact strip portions 35, 35', 35" as the last step of operation. The contact strip portions 35, 35', 35" comprise an odd number of contact - 11 -

ele ents 8 and have a length which is a multiple of the spacing between the elements 8. The contact strips are used for the electrical and mechanical connection of two mutually perpendicular circuit boards, for example for connecting a so-called "daughter board" to a so-called "mother board" in electrical or electronic devices.

Claims

- 12 - CLAIMS

1. A contact strip for the electrical connection of a first and a second mutually perpendicular circuit boards, comprising: an insulating receiving member in the form of an elongate strip (3) is provided; a contact element (8) with a transition zone (9) extending in the strip (3), a first contact zone (10) for electrical connection to the first circuit board and a second contact zone (10') for electrical connection to the second circuit board the first contact zone (10) and the second contact zone (10') of the contact elements (8) protrude from the strip (3) in the direction of the respective circuit board; characterised in that_<? the insulating receiving member has a carrier web (7) and two transverse arms (5, 6) such that the transition zone (9) extends along the transverse arm (5, 6) and the carrier web (7) is arranged at an angle bisecting the angle between the circuit boards.

2. The contact strip according to claim 1, characterised in that the transverse arms (5, 6) and the carrier web (7) have ends angled to form support surfaces (12, 12') corresponding to the circuit boards .

3. The contact strip according to claim 1 or 2, characterized in that the transverse arms (5, 6) and carrier web (7) define a T-shaped cross-section. - 13-

4. The contact strip according to claims 1-3, characterized in that the contact strip includes multiple contacts.

5. The contact strip according to claim 4, characterized in that the alternating transverse arms, along the length of the contact strip include support surfaces corresponding to alternating ones of the printed circuit boards.

6. The contact strip according to claim 4, characterised in that the strip (3) has a length corresponding to a multiple of the spacing between contact elements (8) .

7. A process for producing a contact strip for connecting two mutually perpendicular circuit boards, consisting of the following steps: forming a metal grid (31) with carrier rails (32) and a plurality of contact elements (8) located transversely to the strip direction in such a way that adjacent contact elements (8) remain connected to one another as a grid by means of two carrier rail (32) , moulding a plastic material about the metal grid (31) and between the carrier rails (32) in such a way that an elongate strip (33) with a substantially T-shaped cross section and two longitudinal sides is formed, removing the carrier rails (32) and the plastic material from the strip (33) in certain regions in such a way that individual electrically separated contact elements (8) are formed from the metal grid (31), and a gap is formed in the plastic material on the longitudinal sides of the strip (33), for each second contact element (8) in an alternating manner, - 14 -

bending the contact zones (10, 10') of the contact elements at an angle of 45° from the plane of the T-shaped strip (33) on the longitudinal sides in such a way that the contact zones (10, 10') of each individual contact element (8) form substantially a right angle with one another, separating the T-shaped strip (33) in the longitudinal direction in such a way that individual contact strip portions (35, 35', 35") with an odd number of contact elements (8) are formed which have a length corresponding to a multiple of the spacing between contact elements (8) .

8. The process for producing a contact strip according to claim 7, characterised in that the metal grid (31) is electrolytically coated in the contact zones (10, 10') after punching.

9. The process for producing a contact strip according to claim 7 or 8, characterised in that the contact elements

(8) are bent away in such a way that the position of the bending point can be selected freely between the transition zone (9) and the contact zone (10, 10').