WO2007144428A1

WO2007144428A1 - Electrical connector

Info

Publication number: WO2007144428A1
Application number: PCT/EP2007/055976
Authority: WO
Inventors: Nobuhito Iseki; Masahiko Motoyama; Haruki Yamazaki
Original assignee: Fci; Fci Connectors Singapore Pte Ltd
Priority date: 2006-06-15
Filing date: 2007-06-15
Publication date: 2007-12-21

Abstract

The invention has the object of improving the ease of making press-fit connections and preventing degradation of impedance characteristics. The electrical connector of the present invention has a group of contacts comprising a plurality of signal contacts and a plurality of ground contacts, to be press-fit connected to through holes on a PCB, such that the plurality of signal contacts and plurality of ground contacts have bulge portions of larger lateral dimension than the through holes, and the bulge portions have openings in a direction lateral to a direction of insertion of the contacts; and at least one of the ground contacts has an extension portion extending from the bulge portion thereof.

Description

ELECTRICAL CONNECTOR

TECHNICAL FIELD

The present invention relates to an electrical connector for high-speed transmission to be mounted on a printed circuit board (PCB), and more specifically relates to an electrical connector that is easily handled for press-fit connection to a PCB and has good frequency characteristics.

BACKGROUND

With the increasing information capacity and higher speeds of information transmission of recent years, interfaces capable of transmitting high-speed signals between various electronic devices are being employed. Electrical connectors used in such interfaces have a contact group including signal contacts and ground contacts, and must have high frequency characteristics such as low loss, low leakage (low crosstalk) and low reflection. Therefore, in order to improve these characteristics, various connection formats have been applied to electrical connectors and PCBs.

Backplanes (receiving-side circuit boards or devices having sockets or slots for connecting circuit boards) used in communication devices or the like predominantly use a connection format in which the leg portions of the contacts of an electrical connector are pressed into a PCB (known as press-fitting or compliant pins).

Conventional press-fit connection type electrical connectors are explained with reference to Figs. 6, 7 and 8. Fig. 6 shows a PCB 63 comprising an electrical connector 60 and a group of through holes 65 in the thickness direction. The positions of the tips of leg portions 62 of the group of contacts 61 are matched to a standard height in order enabling them to be placed on the PCB, and each contact is provided with a bulge portion 67 having a through hole 66 in the direction perpendicular to the direction of insertion of the electrical connector 60 into the through holes 65 of the PCB 63. The width of the bulge portions 67 is greater than the diameter of the through holes 65. Additionally, in a process of press-fit connection of the electrical connector 60 to the PCB 63, as the bulge portions 67 are inserted into the through holes 65, they are squeezed by the inner wall surfaces of the through holes to be deformed to the diameter of the through holes as shown in Fig. 7, establishing electrical connections with conductive films 75 coated inside the 5 through holes 65 at a predetermined contact pressure. As a result, an electrical path is formed through an inner layer trace 77 inside the thickness of the PCB.

DISCLOSURE OF THE INVENTION

o However, the press-fit connection format has a serious problem in that the impedance is extremely low, so reflection occurs when high-speed signals are introduced. The cause of this problem, as shown in Fig. 7(a), is that the excess length A of the conductive film 75 in the through holes of the PCB and the excess length B of the leg portions of the contacts connected to the conductive films 75 in the through holes (these 5 electrically extraneous portions will be referred to as "stubs") carry a large capacitance component and form a coupled capacitance, thus greatly reducing the characteristic impedance of the electrical connector at the contact portions, as a result of which signal reflections and crosstalk occur.

o One solution to the above problem is known as "backdrilling". As shown in Fig.

7(b), backdrilling is a method of removing, by means of a drilling process, the stubs A of the conductive films inside the through holes of the PCB from the surface opposite the surface on which the electrical connector is mounted. However, this method requires extremely high machining precision and thus involves a high processing cost, and is 5 therefore not widely used.

Another solution is to provide electrical connector with contacts of short legs. However, if the legs of the contacts are too short, the leg portions of the contacts can only be shallowly inserted into the through holes of a PCB, as shown in Fig. 8, when 0 temporarily placing the electrical connector over the through holes of the PCB during the press-fitting work, and this is unstable (see Fig. 8(a)). As a result, the leg portions of the contacts can become easily displaced from the through holes due to impacts and vibrations (see Fig. 8(b)), and even if the electrical connector is to be pressed in at a predetermined position, it can easily become displaced if the direction of pressing is not the direction perpendicular to the PCB, which causes problems in terms of handling when processing.

Therefore, the present invention is to offer an electrical connector of press-fit connection format, maintaining good high frequency characteristics and being easy to handle for making press-fit connections.

The present invention may be implemented as an electrical connector which can be securely mounted on a PCB, without degrading the frequency characteristics of the electrical connector. In one embodiment, at least one or some of the ground contacts has a leg portion longer than that of the signal contacts.. Longer ground contact legs provide desired connection strength and positional accuracy between the connector and a PCB. In the meantime, as the ground contact legs are longer than the signal contact legs, frequency characteristics of the electrical connector will not be electrically affected among the group of contacts. In another embodiment, one or more signal contacts has a leg portion in a length sufficient to provide desired connection strength positional accuracy between the connector and a PCB. An extended end portion of the leg portion of the signal contacts, which maybe too long to result in a reduction of frequency characteristics of the electrical connector, is configured to be removable. After the electrical connector is securely mounted onto a PCB, the end portion of the signal contacts may be removed. Degradation of the frequency characteristics of the electrical connector can therefore be successfully avoided.

To achieve the above purpose, an electrical connector according to an embodiment of the present invention has a group of contacts comprising a plurality of signal contacts and a plurality of ground contacts, to be press-fit connected to through holes on a PCB. At least one of the plurality of signal contacts and plurality of ground contacts has a bulge portion of larger dimension in a first lateral direction than the diameter of the corresponding through hole, and each bulge portion has a opening formed there on in a second lateral dimension. At least one of the ground contacts has an extension portion extending from the bulge portion thereof. Additionally, the group of contacts in the electrical connector of the present invention preferably form an array consisting of m rows and n columns, the ground contacts being positioned in at least the first column and n-th column or the first row and the m-th row.

Furthermore, in the electrical connector of the present invention, at least two ground contacts at the positions of row 1, column 1 and row m, column n or row 1, column n and row m, column 1 have extension portions.

Furthermore, the extension portion of the ground contact of the electrical connector of the present invention preferably has a notch portion between the bulged portion and the extension portion by which, the extension portion may be easily removed by being pulled away from the PCB.

In another embodiment, an electrical connector has a group of contacts comprising a plurality of signal contacts and a plurality of ground contacts, to be press-fit connected to through holes on a PCB. at least one of said plurality of signal contacts and plurality of ground contacts has a bulge portion of larger dimension in a first lateral direction than a diameter of a corresponding through hole, and said bulge portions has an opening in a formed thereon in a second lateral direction; and at least one of the signal contacts has an extension portion extending from the bulge portion thereof.. Advantageously, the a notch portion may be formed between the extension portion and the bulge portion, hence to ease the removal of the extension portion after the electric connection is secured on a PCB, by pulling the extension portion away from the bulge portion.

Furthermore, the tips of the signal contacts and the ground contacts are positioned at roughly the same positions after removal of the extension portions of the ground contacts and/or the signal contacts of the electrical connector.

In a further embodiment, an electrical connector has a group of contacts comprising a plurality of signal contacts and a plurality of ground contacts, to be press-fit connected to through holes on a PCB. At least one of said plurality of signal contacts and plurality of ground contacts has a bulge portion of larger dimension in a first lateral direction than a diameter of a corresponding through hole, and said bulge portion has an opening formed thereon in a second lateral direction. The length of the bulge portion and 5 the opening of at least one of the ground contacts is longer than the length of the bulge portion and the opening of the signal contacts. Thus, by providing a connector having only ground contacts with longer bulge portion, instead of having extension portion, it is also possible to provide an electrical connector allowing press-fit connections without adversely affecting impedance characteristic of the connector at the contact portion, by o maintaining said impedance characteristic as constant as possible.

Effects of the Invention

(1) Since the electrical connector of the present invention is such that at least one 5 ground contact has an extension portion extending from the bulge portion thereof, press-fit connection can be easily performed by temporarily inserting the extension portions into through holes, and providing securing points on the through holes. Additionally, by providing extension portions on only the ground contacts that are not electrically affected, it is possible to obtain good frequency characteristics for the electrical connector even o after press-fit connection.

(2) Additionally, an electrical connector according to another embodiment of the present invention has ground contacts with extension portions positioned in at least the first row and n-th row or the first column and m-th column, so the work can be made 5 easier by enabling the work of pressing into the through holes to be performed after positioning the electrical connector on the PCB using positions of the contacts on the outermost columns or rows as a reference.

(3) Furthermore, an electrical connector according to another embodiment of the 0 present invention has ground contacts with extension portions positioned on at least two points at the ends of a diagonal, so the work can be made easier by enabling the extension portions to be reliably positioned in the through holes. (4) Furthermore, an electrical connector according to another embodiment of the present invention has a notch portion between the extension portion and the bulge portion of a ground contact and/or a signal contact, so the stubs formed by the excess lengths of

5 the leg portions of the electrical contacts are made weak and can be easily removed to eliminate the possibility that the impedance characteristics will be reduced.

(5) Furthermore, the electrical connector according to another embodiment is such that the signal contacts have extension portions with notch portions capable of being o removed by pulling, so the press-fit connector work can be performed after inserting the extension portions of the leg portions of the signal contacts to predetermined positions in predetermined through holes in the PCB, for temporary placement in a stable state, and the extension portions which are stubs can be removed after press-fit connection, so as not to affect the impedance characteristics. 5

(6) Furthermore, the electrical connector according to another embodiment is such that the tips of the contacts are positioned at roughly the same positions, so that if the tips are defined to be at the positions of an inner layer trace formed in the thickness of the PCB, the excess lengths of the connection portions of the contacts can be removed after press-fit o connection, thus eliminating coupled capacitance caused thereby.

BRIEF DESCRIPTION OF THE DRAWINGS

[Fig. l(a)] A perspective view showing an electrical connector according to one 5 embodiment of the present invention.

[Fig. l(b)] A perspective view showing the positional relationship between a group of contacts on a press-fit connection type electrical connector shown in Fig. l(a) and the through holes on a PCB.

[Fig. 2] An enlarged view showing the electrical connector of Fig. l(a) 0 temporarily placed on a PCB.

[Fig. 3] A diagram showing the arrangement of a group of contacts seen from the direction of the tips of the group of contacts in another embodiment of the present invention.

[Fig 4] (a) A side view showing the thickness of the extension portion and (b) a plan view showing the width of the extension portion in an embodiment of the extension portion of the signal or ground contacts. [Fig. 5] (a) An inner section view immediately after press-fit connection of a contact having an extension portion in a through hole of the PCB. (b) An inner section view with the extension portion removed after (a).

[Fig. 6] A perspective view of a conventional press-fit connection type electrical connector and a PCB. [Fig. 7] (a) A section view of press-fit connection of a conventional electrical connector, (b) A section view of press-fit connection using a backdrilling method.

[Fig. 8] (a) A diagram of the state of a conventional electrical connector when temporarily placed over through holes, (b) A diagram of the state in which the contacts have been displaced due to an impact or vibrations. [Fig. 9] An enlarged view of another embodiment of the present invention, in a state wherein an electrical connector is temporarily placed on a PCB.

[Fig. 10] An enlarged view of another embodiment of the present invention, in a state wherein an electrical connector is temporarily placed on a PCB.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Examples of preferred embodiments of the present invention shall here be explained with reference to the drawings. In the drawings, the same reference numbers are used to indicate the same structural elements, and their explanations may be omitted.

EXAMPLE 1

As shown in Figs. l(a) and l(b), a press-fit connection type electrical connector 10 according to one embodiment of the present invention has a group of contacts 11 for press-fit onto a PCB 14 at a group of corresponding through holes 15. This group of contacts 11 has an array consisting of two rows and ten columns with a plurality of signal contacts 12 and a plurality of ground contacts 13. Each signal contact 12 and each ground contact 13 has a bulge portion 17 with a larger dimension in a first lateral direction, depicted by line 27 in Fig. l(a), than the diameter 25 of the through holes 15. Each bulge portion 17 has an opening 16 in a direction in a second lateral direction, depicted by line 26 in Fig. l(a). It should be appreciated that while in Fig l(a) first and second lateral directions are shown by reference numbers 27 and 26 as perpendicular to each other, it also possible that first and second directions may be selected with an angular relative position. In addition, the term "lateral" used in the context should be understood as referring to directions generally perpendicular to the longitudinal axis 28 of the contacts 13, which may also include situations that first and second directions are oriented with an angular position relative to the longitudinal axis 28 of the contacts 13.

The ground contacts 13 are positioned at both sides of two adjacent signal contacts 12 on the same row of the array. At least one of the ground contacts 13 has an extension portion 19 extending from the tip of the bulge portion 17. By providing such an extension portion 19 on at least one ground contact 13, a reference point can be formed for affixing the electrical connector 10 to the PCB 14, thus improving the ease of making the press-fit connection and a secured manner and with desired positional accuracy. The contact group may have an array composed of m rows and n columns.

Fig. 2 is an enlarged perspective view showing the contact group 11 with the electrical connector 10 according to the embodiment as shown in Fig. l(a) temporarily placed on the PCB 14. Since positioning is performed in a temporary state with the extension portions 19 inserted to some depth in the through holes, the leg portions of the contacts will not become displaced from the positions of predetermined through holes even upon receiving impacts or vibrations. As a result, the electrical connector can be easily connected to a PCB by press-fitting.

EXAMPLE 2

Fig. 3 shows contact group array from the direction of the tips of the contact group of an electrical connector according to another embodiment of the present invention. The contact group has m rows and n columns, so that the ground contacts having the extension portions may be positioned on the first column and n-th column or the first row and the m-th row, or at the ends of the diagonals from row 1, column 1 to row m, column n, or row 1, column n to row m, column 1. By using these arrangements of ground contacts, it is possible to reliably place and position the electrical connector on the PCB in at least two points. Additionally, press-fit connection is completed by pressing the electrical connector in the direction of insertion of the PCB after positioning. At this time, the press-fit connection can be easily performed without displacement, thus contributing to improved ease of working.

EXAMPLE 3

Fig. 4 shows an embodiment that concerns the bulge portions 17 and extension portions 19 of the leg portions of the signal contacts or ground contacts, (a) is a side view showing the thickness of the extension portion 19, and (b) is a plan view showing the width of the extension portion 19.

The extension portion 19 may be rod- shaped, and notch portions 41 are formed in the circumferential direction in the vicinity of the base portion thereof. The notch portions 41 are provided to enable the extension portion 19 to be separated from the leg portion, by reducing the strength of attachment between the extension portion 19 and the bulge portion 17. Additionally, the extension portion 19 can be made an arbitrary shape such as cylindrical or angular, and is preferably set to be longer than the depth of the through holes 15 after press-fit connection.

Fig. 5 is a partial cross sectional view of a signal or ground contact having an extension portion as shown in Fig. 4, in a state of press-fit connection to a through hole of a PCB. (a) shows the state immediately after press-fit connection and (b) shows the state after removal of the extension portion in (a).

In Fig. 5(a), the extension portion 19 passes through the through hole 15 and projects from the surface opposite the surface of mounting of the electrical connector. Since the extension portion 19 is extended from the edges of the through hole 15, the extension portion 19 can be severed from the bulge portion 17 at the notch portion 41, by being pulled in a direction of separation from the through hole 15 while rocking the extension portion back and forth and/or side to side. Alternatively, in another embodiment, the extension portion 19 maybe made roughly cylindrical, and the extension 5 portion 19 can be severed from the bulge portion 17 at the notch portion 41 by being pulled in a direction of separation from the through hole 15 while rotating or twisting the extension portion.

Accordingly, the extension portion 19 can be easily removed after press-fit o connection, thus eliminating stubs which are a cause of reduced characteristic impedance at the electrical connection portions between the contacts and the conductive films in the through holes 15.

EXAMPLE 4 5

Fig. 9 shows a variant embodiment of the ground contact 130 of the contact group 11 in Fig. l(a), and is an enlarged view of a signal contact 120 and a ground contact 130 in a state of temporary placement over a PCB. In Fig. 9, the bulge portion 137 and opening 136 of ground contacts 130 are extended in the axial direction, and are longer than that of o signal contacts 120. As a result, the length in the axial direction of the bulge portion 137 and opening 136 of the ground contact 130 is longer than the length in the axial direction of the bulge portion 127 and opening 126 of the signal contact 120. When the connector 10 of the present embodiment is temporarily placed on a PCB 14, only the end portion 21 of the ground contact 130 is inserted into the through hole 15. As a result, the connector 5 10 can be positioned in a state of temporary placement on the PCB, so the leg portions of the contact group 11 will not become displaced from the positions of predetermined through holes 15 even upon receiving an impact or vibrations. Thus, the electrical connector 10 can be easily press-fit connected to a PCB in this state.

0 Additionally, as explained in Example 3, the bulge portion 137 and opening 136 of the ground contact 130 are formed such as to have adequate length in the axial direction and circumferential notch portions are formed at predetermined positions, and after press-fit connection, the portion with the opening 136 can be shaken forward-backward and right-left, to remove the stubs so that the end portions of the signal contacts 120 and the ground contacts 130 are at roughly the same position.

In order to reduce insertion loss during the press-fit connection of the connector, as shown in Fig. 10, en electrical connector according to embodiments of the invention may advantageously have the lateral dimension of the bulge portion 227 of the signal contact 220 configured smaller than that of the ground contact 230. Accordingly, the lateral dimension of signal through hole 152 of PCB 140 may also be smaller than that one of the ground through hole 154. As described above, the electrical connector according to embodiments of the present invention provides extension portions from the tips of the bulge portions of ground contacts, or has bulge portions and through holes of the ground contacts which are longer in the axial direction than the bulge portions and through holes of the signal contacts, so that the overall lengths of the leg portions are longer than those of the signal contacts, thus enabling press-fit connections to be made without degrading the impedance characteristics and being affected by impacts or vibrations.

Additionally, the electrical connector of the present invention enables stubs to be removed after press-fit connection by severing of the extension portions from the tips of the bulge portions.

Furthermore, the electrical connector of the present invention provides severable extension portions from the tips of the bulge portions of the signal contacts, thus enabling press-fit connections to be made without being affected by impacts or vibrations, and preventing degradation of impedance characteristics by severing the extension portions after press-fit connection.

Claims

1. An electrical connector having a group of contacts comprising a plurality of signal contacts and a plurality of ground contacts, to be press-fit connected to through holes on a PCB, characterized in that at least one of said plurality of signal contacts and one of the plurality of ground contacts has a bulge portion of larger dimension in a first lateral direction than a diameter of a corresponding through hole, and each of said bulge portions has an opening formed thereon in a second lateral direction ; and at least one of the ground contacts has an extension portion extending from the bulge portion thereof.

2. An electrical connector of claim 1, wherein said group of contacts form an array of m rows and n columns, said ground contacts being positioned in at least a first column and n-th column or a first row and the m-th row.

3. An electrical connector of claim 2, wherein at least two ground contacts at the positions of row 1, column 1 and row m, column n or row 1, column n and row m, column 1 have extension portions.

4. An electrical connector of any one of claims 1 to 3, wherein said at least one of the ground contacts has a notch portion between said extension portion and the bulge portion.

5. An electrical connector of claim 1, wherein a largest lateral dimension of the bulge portion of the signal contacts is smaller than a largest lateral dimension of the bulge portion of the ground contact.

6. An electrical connector having a group of contacts comprising a plurality of signal contacts and a plurality of ground contacts, to be press-fit connected to through holes on a PCB, characterized in that at least one of said plurality of signal contacts and plurality of ground contacts has a bulge portion of larger dimension in a first lateral direction than a diameter of a corresponding through hole, and said bulge portions has an opening in a formed thereon in a second lateral direction; and

5 at least one of the signal contacts has an extension portion extending from the bulge portion thereof.

7. An electrical connector of claim 6, wherein said at least one of the signal contacts has a notch portion between said extension portion and said bulge portion. 0

8. An electrical connector of claim 7, wherein the tips of said signal contacts and said ground contacts are positioned at the same positions after removal of the extension portions.

5 9. An electrical connector having a group of contacts comprising a plurality of signal contacts and a plurality of ground contacts, to be press-fit connected to through holes on a PCB, characterized in that at least one of said plurality of signal contacts and plurality of ground contacts has a bulge portion of larger dimension in a first lateral direction than a o diameter of a corresponding through hole, and said bulge portion has an opening formed thereon in a second lateral direction ; and the length of the bulge portion and the opening of at least one of the ground contacts is longer than the length of the bulge portion and the opening of the signal contacts. 5

10. An electrical connector in accordance with claim 9, wherein a largest lateral dimension of the bulge portion of the signal contacts is smaller than a largest lateral dimension of the bulge portion of the ground contact.