Contact module, connector and method of producing said contact module

The present invention provides a contact module, a connector, and a method of producing the contact module. The contact module includes a base and a plurality of contacts. Each of the contacts is bent at both ends in one direction. In a section view of each of the contacts, an insulating film, a barrier film, a plating base film, and a plating film are formed on a sheet in this order. The base that bridges the contacts has only the insulating film laminated on the sheet. The plating film has contact points at the bent parts, and a circuit pattern that is interposed between the contact points. The circuit pattern functions as a signal line.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a contact module, a connector, and a method of producing the contact module.

2. Description of the Related Art

Connectors are classified into various types, according to the shape, the purpose of use, the connecting method, and other factors.

For instance, according to the mounting type, connectors can be classified as LSI sockets that are connected to LSIs, wiring board connectors that are connected to wiring boards, and relay connectors that are used for connecting cables to cables.

Among the above connectors of various types, the wiring board connectors can be further classified into edge-card connectors and two-piece connectors.

FIGS. 1 and 2show conventional edge-card connectors, each of which is used to connect a mother board1and a daughter card2. A pad3provided in the pattern (not shown) formed on each side of the daughter card2is interposed between the daughter card2and a contact4. Here, the patterns on the daughter card2are used as the inserting ends. A connector5ashown inFIG. 1is a through-hole mounting type. More specifically, one end of each of the contacts4is inserted into a through hole (not shown) formed through the mother board1, and is then soldered and fixed thereto, so that the connector5ais mounted to the mother board1. On the other hand, a connector5bshown in FIG.2is a surface mounting type. More specifically, one end of each contact4is soldered and fixed to a pad6formed on the mother board1, so that the connector5bis mounted to the mother board1.

FIG. 3shows a two-piece connector5c. InFIG. 3, a receiving connector5c-1is mounted to a wiring board7, while an inserting connector5c-2is mounted to a wiring board1. The two connectors5c-1and5c-2are engaged with each other, so as to form the two-piece connector5c.

Although the connectors differ in shape according to the type of mounting as described above, the wiring board connectors, the LSI sockets, and the relay connectors each have a number of pin-shaped or tongue-shaped contacts that are made of a metal material and are accommodated in a housing (denoted by reference numeral8inFIGS. 1 through 3) made of an insulating resin.

If the contacts are of press-fit types, having pin-like shapes, a flat metal material is formed into a plurality of contacts by a cut-out technique, a stamp-out pressing technique, bend pressing technique, or a mold pressing technique. If the contacts have tongue-like shapes, a flat metal material is also formed into a number of contacts by a cut-out technique or a stamp-out pressing technique.

A connector is required to have certain mechanical characteristics, as well as electric characteristics that will be described later.

When a connector is fitted to a substrate or the like, it is desirable that the connector can be inserted into the connecting opening of the substrate with only low insertion force. Also, after the insertion, it is essential for the contacts to be in sure contact with the electrodes of the substrate. In view of this, a so-called LIF (Low Insertion Force) structure in which the contacts have spring-like characteristics should be employed, so as to obtain great contact force after the contacts are inserted with low insertion force. Meanwhile, when the contacts are inserted, it is not desirable to cause abrasion and wear due to the sliding contact between the contacts and the electrodes. In view of this, a so-called ZIF (Zero Insertion Force) structure, in which the electrodes are brought into contact with the contacts only after the connection is completed, should be employed so as to prevent the sliding contact between the contacts and the electrodes. Also, to prevent the above problems, various types of contacts have been developed in terms of shapes, materials, and surface-finishing methods.

Other than the above characteristics, a connector is always required to have low noise by reducing the size, increasing the contact density, increasing the speed (or the transmission speed), and restricting crosstalk.

However, a conventional connector has pin-like contacts as described above. Because of this, there is naturally a limit to the size of the connector and the contact density. As for the contact density, for instance, it is difficult to arrange the contacts at intervals narrower than 0.2 or 0.3 mm.

Having a three-dimensional structure as described above, a conventional connector is designed and manufactured by using a simulation and three-dimensional CAD or CAE in such a manner that the electric characteristics satisfy predetermined conditions. Because of the complicated three-dimensional shape, it is difficult of maintain the variation of the impedance level within ±10%. This leads to difficulties in eliminating noise due to non-matched impedance.

SUMMARY OF THE INVENTION

A general object of the present invention is to provide contact modules, connectors, and methods of producing contact modules, in which the above disadvantages are eliminated.

A more specific object of the present invention is to provide a contact module, a connector, and a method of producing the contact module, by which a small-sized connector having a high contact density can be realized.

Another specific object of the present invention is to provide a contact module, a connector, and a method of producing the contact module, by which impedance matching can be carried out with high precision, and signal coupling can be made as firm as with a circuit board (a printed board).

The above objects of the present invention are achieved by a contact module that includes: a sheet that is made of a metal material; an insulating film that is formed on at least one side of the sheet; and a contact that is made of a noble metal material, is formed as a thin film on the insulating film, and includes a contact point and a circuit pattern.

In the above contact module, the circuit pattern may be a wiring pattern or wires. The contact point and the circuit pattern may be made of a base metal material, but a noble metal material is preferable in terms of mechanical characteristics, such as abrasive resistance, hostile-environment resistance, and corrosion resistance. Here, the noble metal material may be a single noble metal or noble metals of a few different types.

With the above structure, the contact can be formed as a thin film, and a large number of such contacts can be arranged at narrow intervals. Accordingly, a small-sized connector having a high contact density can be realized.

Also, as the contact is formed by the contact point and the circuit pattern in the form of a thin film, impedance matching can be carried out with high precision.

In a conventional connector having a plurality of contacts, it is difficult to avoid differences in transmission distance (or wiring length) in the wiring pattern between the contacts of each two adjacent rows, with the connector being mounted to the substrate and the rows of contacts being connected to the wiring pattern of the substrate. Such differences in transmission distance cause a problem in parallel transmission, for instance. In the present invention, on the other hand, the pattern lengths of the circuit pattern are varied so as to avoid the above problem.

The above objects of the present invention are also achieved by a contact module that includes: a sheet that is made of a metal material; an insulating film that is formed on both sides of the sheet; and a contact that is made of a noble metal material, is formed as a thin film on the insulating film, and includes a contact point and a circuit pattern.

With this contact module in accordance with the present invention, a small-sized connector having a high contact density can be realized.

This contact module may have a belt-like base, and a plurality of contacts that interpose the base, extend from both ends of the base, and are arranged in a comb-like form. In this manner, a contact module having a plurality of contacts can be easily obtained by processing a single sheet.

In this contact module, each of the contacts may have spring-like characteristics. With the contacts having spring-like characteristics, the contacts can be flexibly inserted into a mating material, and the restoring force of the contacts after the insertion provides great contact force.

Also in this contact module, the metal material may be stainless steel or copper alloy, so that the contact module can be easily formed into a predetermined shape by an etching process, and that the sheet can obtain necessary strength and excellent spring-like characteristics. If the sheet is used as a ground terminal in this case, copper alloy is more preferable so as to obtain excellent conductivity.

If the contact point and the circuit pattern are formed by a gold plating film, excellent conductivity can be obtained, and abrasion and wear of the contacts due to repeated insertion of the contacts can be dramatically reduced. Thus, stable contact resistance can be maintained even with low contact force.

In the above structure, a nickel plating film may be interposed between the gold plating film and the insulating film, so as to surely prevent the gold plating film separating from the insulating film. In this manner, the hard nickel plating film can effectively increase the abrasive resistance.

If the insulating film is made of an insulating resin material in the above structure, a thin-film insulating film can be easily realized.

The objects of the present invention are also achieved by a connector that includes one of the above-described contact modules. In this connector, the sheet and the circuit pattern are adjusted to a predetermined characteristic impedance level, so as to reduce the noise due to signal reflection.

If the sheet is used as a ground layer or a power source layer in this connector, crosstalk can be effectively reduced.

In this structure, a ground terminal may be provided at the edge of the sheet, so that the sheet as a ground layer is connected to the ground line of a substrate to which the connector is connected. Here, the sheet that functions as a ground sheet has a part formed into at least one ground terminal.

If the circuit pattern is formed into a pair of circuit patterns that function as parallel transmission signal lines, crosstalk can be reduced for the same effect as so-called edge couplings can have in a circuit board. Also, signal coupling can be made as firm as in a circuit board.

The objects of the present invention are also achieved by a connector that includes a contact module having: a sheet that is made of a metal material; an insulating film that is formed on both sides of the sheet; and a contact that is made of a noble metal material, is formed as a thin film on the insulating film, and includes a contact point and a circuit pattern. In this connector, the circuit pattern formed on both sides of the sheet is adjusted to a predetermined characteristic impedance level, so as to effectively reduce noise caused by signal reflection.

In this connector, the circuit pattern formed on one side of the sheet preferably functions as a signal line, while the circuit pattern formed on the other side functions as a ground line or a power source line.

In this connector, the circuit pattern formed on both sides of the sheet may be formed into a pair of circuit patterns that function as parallel transmission signal lines, and the sheet may function at least as a ground layer. With this structure, crosstalk can be reduced for the same effect as so-called broad-side couplings can have in a circuit board. Also, signal coupling can be made as firm as in a circuit board.

In this connector, the circuit pattern formed on one side of the sheet may function as a signal line while the circuit pattern formed on the other side functions as a power source line, and the sheet may function as a ground layer. With this structure having the sheet as a ground layer, crosstalk can be effectively reduced.

Also in this connector, the sheet and the circuit pattern formed on both sides of the sheet may be adjusted to a predetermined characteristic impedance level, so as to effectively reduce noise due to signal reflection.

The objects of the present invention are also achieved by a method of producing a contact module, including the steps of:

forming an insulating film by applying an insulating material onto a metal sheet;

forming a plurality of rows of plating films that serve as contact points and a circuit pattern, by subjecting the insulating film to plating treatment using a mask having a pattern formed thereon; and

forming a plurality of rows of contacts formed from the plating films on a metal sheet, by removing parts of the insulating film and the metal sheet that are exposed by etching treatment using a mask having a pattern formed thereon.

The objects of the present invention are also achieved by a method of producing a contact module, including the steps of:

forming an insulating film by applying an insulating material onto a metal sheet;

forming a plurality of rows of insulating film patterns by patterning the insulating film;

forming a plurality of rows of plating films that serve as contact points and a circuit pattern, by subjecting the insulating film pattern to plating treatment using a mask having a pattern formed thereon; and

forming a plurality of rows of contacts formed from the plating films on a metal sheet, by removing parts of the insulating film and the metal sheet that are exposed by etching treatment using a mask having a pattern formed thereon.

According to this method, a contact module having a plurality of contacts can be easily obtained from a single sheet through a simple process.

The above and other objects and features of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring first toFIGS. 4 through 8, a contact module in accordance with a first embodiment of the present invention will be described.FIG. 4is a partial perspective view of the contact module, seen from the upper surface side.FIG. 5is a partial perspective view of the contact module, seen from the lower surface side.FIG. 6is a plan view of the contact module.FIG. 7is a bottom plan view of the contact module.FIG. 8is a section, taken along the line VIII—VIII ofFIG. 6, showing the contact module.

The contact module10of the first embodiment of the present invention includes a base12that is shaped like a belt extending in the direction indicated by X1-X2inFIG. 4, and a plurality of contacts14that protrude from both ends of the base12in the direction indicated by Y1-Y2inFIG. 4and are arranged in a comb-like form. Each of the contacts14is bent at both ends toward the same direction, so as to have a claw- or tongue-like shape. The base12is provided with a plurality of holes13, which will be described later.

Referring toFIG. 8, the section of each of the contacts14of the contact module10shows a laminated structure, having an insulating film18, a barrier film20, a plating base film22, and a plating film24, which are laminated in this order on a sheet16. In this structure, each of the contacts14has an end part (indicated by the arrow A inFIG. 4) in which only the insulating film18is laminated on the sheet16. Also in the base12that bridges the contacts14, only the insulating film18is laminated on the sheet16. However, the end portion of each contact14may also have the same laminated structure as the rest of the parts of the contact14, having the plating film24as the outermost layer. The base12may be formed by only the sheet16.

The sheet16serves as the base member of the laminated structure, giving certain strength to each of the contacts14and the contact module10, and spring-like characteristics to the contacts14. The sheet16is made of a metal material, such as SUS. It is preferable to employ a copper alloy material, instead of SUS, in terms of conductivity. The thickness of the sheet16should be in the range of 20 to 90 μm.

The insulating film18is used to insulate the sheet16from the plating film24. The insulating film18is made of an insulating resin material, such as polyimide resin. Other than polyimide resin, it is possible to employ polyethylene terephthalate resin or epoxy resin. The insulating film18may be made of an inorganic insulating material, instead of an insulating resin material. The thickness of the insulating film18should be in the range of 5 to 6 μm.

The barrier film20ensures adhesion between the insulating film18and the plating film24. The barrier film20is made of a metal material, such as chromium or titanium. The thickness of the barrier film20should be approximately 0.05 μm. The barrier film20can be omitted from the laminated structure, if necessary.

The plating base film22increases the adhesion of the plating film24. The plating base film22is made of a conductive metal material, such as copper. The thickness of the plating base film22is approximately 0.1 μm. The plating base film22can be omitted from the laminated structure, if necessary.

The plating film24functions as a signal line as described later. The bent parts at both ends of each contact14are contact points24aand24b, and the area between the contact points24aand24bserves as a circuit pattern24cconnected to the contact points24aand24b. The plating film24is made of a metal material that is preferably a single noble metal or noble metals of a few different types. An example of the metal material is a plating laminated structure made up of copper, nickel, and gold, which are laminated in this order. In this structure, the copper plating and the gold plating ensure electric properties, corrosion resistance, and lubricity. The nickel plating ensures abrasion resistance. The thickness of the plating film24should be in the range of 4 to 5 μm in total.

The contact module10is suitably used for parallel transmission, which will be described later. Each two adjacent contacts14(as indicated by reference numerals14aand14binFIG. 4) function as a pair, and a plurality of pairs of contacts14aand14bare arranged at constant intervals. On the other hand, if each single contact14function as an independent signal line, the contacts14are arranged at uniform intervals (as shown inFIG. 20).

In the contact module10having the above structure in accordance with the first embodiment of the present invention, each of the contacts14has the sheet12of a certain thickness as a base member. Because of this, each of the contacts14can easily attain spring-like characteristics.

Also, in the contact module having the above structure, each of the contacts14can be made thin, and a large number of contacts14can be arranged at very narrow intervals. Because of this, a connector to which the contacts14are mounted can be made smaller, and the contact density can be increased. As for the contact density, each interval between the contacts14can be made as narrow as 0.1 mm. The conductive part of each of the contacts14, which is the part to function as a signal line, is formed by the thin-film contacts24aand24band the circuit pattern24c. With this arrangement, impedance matching can be carried out with high precision.

Referring now toFIGS. 9 through 12, a method of producing the contact module10in accordance with the first embodiment of the present invention will be described.

First, polyimide resin is applied, by a roll-coat technique, to an SUS substrate (a sheet, or a metal sheet)16ahaving a thickness of 26 μm, so as to form a 6 μm-thick polyimide resin layer. The polyimide resin layer is then subjected to a pre-baking treatment, and is further subjected to a post-baking treatment, so as to form a polyimide resin film (an insulating film)18a(shown inFIG. 9). Here, the polyimide resin film (the insulating film)18ais not formed on the entire surface of the SUS substrate16a, but may be patterned into rows of polyimide resin film that are separate from one another.

Next, rows of chromium film20ahaving a thickness of 0.05 μm are formed, by a sputtering technique, for instance, on the polyimide resin film18a. Further, a copper film22ahaving a thickness of 0.1 μm, for instance, is formed on the chromium film20a(shown inFIG. 10) by a sputtering technique.

Next, plating resist patterning is carried out, and the plating film24is formed by a plating technique. For instance, a copper film24dhaving a thickness of approximately 4 μm, a nickel film24ehaving a thickness of approximately 0.7 μm, and a gold film24fhaving a thickness of approximately 1 μm, are laminated in this order, thereby forming the plating film24(shown inFIG. 11).

Further, each of the films ranging from the plating film24to the chromium film20ais subjected to etching treatment by an etching technique. Here, the parts, from which the films are not removed by the etching, serve as the contact points and the circuit pattern.

Etching resist patterning is further carried out, and the insulating film18aand the SUS substrate16aare subjected to etching treatment by an etching technique, thereby shaping the exterior of the contact module. At this point, the contact module10, which has the SUS substrate16aas the base and a plurality of contacts14arranged at intervals, is almost completed (shown inFIG. 12). The method of shaping the exterior of the contact module may be a stamp-out pressing technique, instead of an etching technique.

Finally, by suitable process techniques, each of the contacts14is bent at both ends, and the holes13are formed in the base12. Here, the contact module10as shown inFIG. 4is completed.

By this method of producing the contact module in accordance with the first embodiment of the present invention, a contact module having a plurality of contacts can be easily obtained from a single sheet by a simple technique, such as an etching technique.

Referring now toFIGS. 13 through 16, a contact module in accordance with a second embodiment of the present invention will be described.FIG. 13is a partial perspective view of the contact module, seen from the upper surface side.FIG. 14is a partial perspective view of the contact module, seen from the lower surface side.FIG. 15is a plan view of the contact module.FIG. 16is a section view, taken along the line XVI—XVI ofFIG. 15, showing the contact module.

A contact module26in accordance with the second embodiment of the present invention has the same laminated structure as the contact module10in accordance with the first embodiment. Therefore, the same components as in the first embodiment are denoted by the same reference numerals as in the first embodiment in the drawings, and explanation for those components will be omitted from the following description.

The contact module26of the second embodiment differs from the contact module10of the first embodiment in that a layer including the contact points24aand24band the circuit pattern24cis formed on both sides of the sheet16in each contact27. More specifically, in each contact27of the contact module26of the second embodiment, the insulating film18, the barrier film20, and the plating base film22are also formed in this order on the lower surface of the sheet16, and the plating film24that serves as the contact points24aand the circuit pattern24cis formed as the outermost layer.

The contact module26of the second embodiment further differs from the contact module10of the first embodiment in that a terminal28is provided between each two adjacent contacts27aand27b. The terminal28includes a long part30ahaving the insulating film18laminated on the sheet16, and contact points30band30cformed at either end of the long part30a. At the contact points30band30c, the films including the plating film as the outermost layer are laminated on the sheet16.

Although the contact module26of the second embodiment has the single-layer sheet16, a structure in which an insulating layer is interposed between two sheets may be employed. In such a structure, one of the two sheets may serve as a power source layer (or a power supply layer), while the other one may serve as a ground layer.

Referring now toFIGS. 17 through 20, a connector in accordance with a third embodiment of the present invention will be described, including the fitting structure of the connector.

A connector30of the third embodiment includes the contact module10of the first embodiment of the present invention, and an insulating member (or a housing)32that is made of insulating resin, for instance. In this connector30, the contact module10is mounted to the insulating member32.

The insulating member32has a base material34in the form of a right-angled triangle pole. This base material34has one rectangular side, as indicated by the arrow B inFIG. 17. The inclined surface34aof the insulating member32has a plurality of protrusions36formed in the mid section of the inclining direction. Each of the protrusions36is a square pole having a round top end. The protrusions36are forced into the holes13of the contact module10, so as to fix the contact module10to the insulating member32, as shown inFIG. 18. Here, a certain gap C is kept between the contact module10and the insulating member32, by adjusting the diameters of the holes13and the protrusions36, for instance.

As shown inFIGS. 18 and 19, the connector30is a so-called edge-card connector, which is used to connect a daughter card40perpendicularly to a mother board (or a back panel)38.

FIG. 19is a perspective view showing the circuit pattern24cof the contacts14of the connector30. As shown inFIG. 19, wiring patterns42and44are formed on the upper surface38aof the mother board38, to which the connector30is fitted, and on one surface40aof the daughter card40a. Pads42aand44aare provided for each of the wires of the wiring patterns42and44, respectively.

The connector30is first fixed to the mother board38by forcing press-fit pins46of the connector30into holes (not shown) formed in the mother board38, so that the inclined surface34aof the insulating member32faces the junction point of the mother board38and the daughter card40. Here, some other engaging members, such as screws, may be used instead of the press-fit pins46.

With the connector30being fitted to the mother board38, the contact point24aof each contact14is fixed and surface-mounted to the corresponding pad42aby soldering. Here, the surface-mounting may be carried out by using a conductive adhesive agent, instead of soldering. On the other hand, the contact point24bof each contact14stands vertically, as shown inFIG. 18.

The daughter card40is then lowered so as to bring the top end of the daughter card40into contact with the mother board38. The daughter card40is then fixed to the connector30with engaging members (not shown) such as screws, thereby completing the connecting process of the connector30. Here, a special-purpose member for supporting the daughter card40may be employed, instead of engaging members. For instance, a supporting member may be provided at the opposite side of the daughter card40from the connector30(i.e., on the left side of the daughter card40inFIG. 18), so that the daughter card40can be pressed against and fixed to the connector30by the supporting member. In any of the above manners, each contact14remains unconnected until being fixed to the corresponding pad44aof the daughter card40. When the pads44aof the daughter card40are pressed against the contact points24aof the contacts14, the contacts14are switched to a connected state. As is apparent from these characteristics, the connector30is a ZIF-structured connector, and has the advantages of the ZIF structure that have been described in the description of the prior art.

In the above structure, a guide member having a guiding part may be employed and fixed to the connector30, the mother board38, or a housing that accommodates the mother board38. The guiding part of this guide member slides the daughter card40along the contacts14, and brings the daughter card40into contact with the mother board38. The daughter card40may be finally fixed to the guide member with some other engaging member. In this manner, the contacts14can have spring-like characteristics, being able to flex with the holes13as the supports. After the daughter card40slides along the contacts14and is then fixed by small contact force, the contacts14can display great contact force. In this case, the connector30is an LIF-structured connector, and has the advantages of the LIF structure, which have been described in the description of the prior art.

As described above, the connector30of the third embodiment of the present invention can sufficiently exhibit the effects of the contact module10of the first embodiment, and embody a small-sized connector having a high contact density.

Also, in the connector30, the conductive parts of the contacts14, i.e., the signal transmission paths, are formed by the circuit pattern24c. Because of this, the impedance level can be easily and accurately adjusted in the designing and manufacturing stages. The sheet16and the circuit pattern24care adjusted to a predetermined characteristic impedance level, so that noise due to signal reflection can be reduced.

Also in the connector30, the sheet16may be electrically connected to the ground (not shown) of the mother board, so that the sheet16can function as a ground layer. In this manner, the crosstalk between each two neighboring contacts14aand14bcan be reduced.

In this case, each two neighboring contacts14aand14bcan be used as parallel transmission signal lines (a paired line) that are suitable for high-speed transmission.

For instance, when a positive signal is transmitted to the contact14a, a negative signal that has the same magnitude as the positive signal and the opposite orientation to the positive signal should be transmitted to the contact14b, so as to realize a preferable transmission system for high-frequency signal transmission. In such a case, the sheet16, which functions as a ground layer, can sufficiently reduce the crosstalk for the same effect as so-called edge coupling in a circuit board can have.

Also, in the connector30, the signal transmission path between the mother board and daughter board, which is formed by the contacts of the connector, has a length L that is shorter than the length 11+12 of the signal transmission path of the conventional connector shown inFIG. 1, as shown inFIG. 19. Because of this, the electric path length becomes shorter than that in the prior art, and such a short electric path length is preferable especially for high-frequency signal transmission.

Referring now toFIGS. 20 through 22, a connector in accordance with a fourth embodiment of the present invention will be described below, including the fitting structure of the connector.

A connector48of the fourth embodiment includes a pair of contact modules50and a pair of insulating members52made of an insulating resin. The contact modules50are attached to the insulating members52.

As shown inFIG. 20, each of the contact modules50basically has the same structure as the contact module10of the first embodiment of the present invention. However, contacts54are arranged at uniform intervals. Also, both ends of each contact54are not bent into a claw-like shape, but each contact54is bent at an angle greater than 90 degrees, so as to form a third of the length of the straight contact54into a lead part56a. The opposite third of the length from the lead part56ais also bent toward the opposite direction, and is then bent back at an obtuse angle, so as to form a gentle protruding part that serves as a contact part56b. Each of the contacts54has a laminated structure having a plating film as the outermost layer (not shown), except for the bent part of the contact part56b. A contact point (corresponding to the contact point24a) and the circuit pattern24care formed on the lower surface (not shown inFIG. 20) of the lead part56a. The circuit pattern24cis also formed at a connecting part56cthat is formed integrally with the base12and connects the lead part56ato the contact part56b. The contact point24bis formed at the contact part56b.

Each of the insulating members52has a square-pole shape, including openings60aand60bat the top and bottom ends, as shown inFIG. 21. The upper opening60ahas a size slightly larger than the section of the daughter card40, so that the daughter card40can be inserted into the opening60a. Also, the upper opening60ais tapered, with the inlet side being wider, so as to facilitate the insertion of the daughter card40. The lower opening60bis wide enough to accommodate each of the pair of contact modules50. A plurality of protrusions64are formed on the inner surface of a side wall62of the insulating member52, and are aligned in the direction perpendicular to the plane ofFIG. 21. Each of the protrusions64has an surface inclined from the bottom to the top, and a horizontal top surface as shown inFIG. 21.

To assemble the connector48, the pair of contact modules50are upwardly inserted into the insulating members52through the lower opening60b, with each of the contact parts56bbeing the top end and facing each corresponding contact part56b. The contact modules50then slide along the protrusions64until the holes13of the contact modules50are engaged with the protrusions64. In this manner, the connector48having the pair of contact modules50fitted to the insulating members52is completed.

Like the connector30of the third embodiment, the connector48is a so-called edge-card connector that connects the daughter card40perpendicularly to the mother board38.

The mother board38and the daughter card40of this embodiment have the same structures as in the connector30of the third embodiment.

Like the connector30, the connector48is fitted and fixed to the mother board38by forcing the press-fit pins46into the holes of the mother board38. Here, some other engaging members, such as screws, may be used instead of the press-fit pins46.

With the connector48being fitted to the mother board38, the contact point24aof each contact54is fixed and surface-mounted to the corresponding pad42aby soldering. On the other hand, the contact part56bof each contact54, i.e., the contact point24b, faces inward from its respective side wall62.

In this situation, the daughter card40is lowered so as to insert the top end of the daughter card40into the connector48, with the upper openings60aof the connector48guiding the top end of the daughter card40. Here, the daughter card40pushes and separates each two facing contact parts56b, and is fixed to the connector48with suitable engaging members when the pads (not shown) of the daughter card40are brought into contact with the contact parts56b. In this manner, the contacts54can have spring-like characteristics, and therefore can display great contact force once the insertion of the daughter card40is completed by sliding the daughter card40along the contacts54.

As described above, the connector48of the fourth embodiment can sufficiently display the effects of the contact module10of the first embodiment, with each of the contacts54being used as a signal line. Accordingly, the connector48can embody a small-sized connector having a high contact density.

Also, the sheet16and the circuit pattern24cin the connector48are adjusted to a predetermined characteristic impedance level, so that noise due to signal reflection can be reduced, as in the connector30of the third embodiment.

Also in the connector48, the sheet16may be electrically connected to the ground (not shown) of the mother board38, so that the sheet16can function as a ground layer. In this manner, the crosstalk between each two neighboring contacts54can be reduced.

Next, a connector having the contact module26of the second embodiment mounted thereto will be described.

In the connector, to which the contact module26is mounted, the circuit pattern formed on one side of the sheet should preferably functions as a signal line, and the circuit pattern formed on the other side of the sheet should preferably functions as a ground line or a power source line (not shown).

In this case, the pair of circuit patterns formed on both sides of the sheet should preferably function as parallel transmission signal lines. Also, the sheet should preferably function as a ground layer, i.e., the terminals28shown inFIG. 13should be connected to a ground line of the mother board. In this manner, crosstalk can be reduced for the same effect as so-called broad-side coupling in a circuit board can have.

Also in this case, the circuit pattern formed on one side of the sheet preferably functions as a signal line, while the circuit pattern formed on the other side functions as a power source line. With the sheet functioning as a ground layer in such a structure, crosstalk can be effectively reduced.

Further, the sheet and the circuit patterns formed on both sides of the sheet are preferably adjusted to a predetermined characteristic impedance level, so that noise due to signal reflection can be reduced.

It is possible to form the laminated structure of each contact of the contact module in different arrangements from the above examples in the preferred embodiments of the present invention. It is also possible to use each of the above connectors for various purposes. For instance, each of the above connectors can be used as an LSI socket to be connected to an LSI, or as a relay connector for connecting cables.

It should be noted that the present invention is not limited to the embodiments specifically disclosed above, but other variations and modifications may be made without departing from the scope of the present invention.

This patent application is based on Japanese priority patent application No. 2001-336990 filed on Nov. 1, 2001, the entire contents of which are hereby incorporated by reference.