WO2004042874A1

WO2004042874A1 - Board-to board electrical connector assembly

Info

Publication number: WO2004042874A1
Application number: PCT/US2003/034761
Authority: WO
Inventors: Toshihisa Hirata; Masami Sasao
Original assignee: Molex Incorporated
Priority date: 2002-11-01
Filing date: 2003-10-31
Publication date: 2004-05-21
Also published as: AU2003286824A1; TW200414635A; JP4116503B2; JP2004281364A

Abstract

A board-to board electrical connector assembly is provided for effecting a connection between two circuit boards. The assembly includes a first connector having a dielectric housing mounted on a first circuit board. The housing has a mating face with a mating recess. A plurality of first terminals are mounted on the housing and each terminal includes a tail portion for connection to an appropriate circuit trace on the first circuit board and a contact portion exposed generally at the mating recess. A second connector has a dielectric housing mounted on a second circuit board. The housing has a mating projection for insertion into the mating recess of the first connector. A plurality of second terminals are mounted on the housing of the second connector. Each second terminal includes a tail portion for connection to an appropriate circuit trace on the second circuit board and a contact portion for engaging the contact portion of one of the first terminals of the first connector.The dielectric housings of the first and second connectors are structurally configured such that the second circuit board mounted on the housing of the second connector closes the mating recess of the housing of the first connector when the connectors are mated.

Description

SPECIFICATION

BOARD-TO-BOARD ELECTRICAL CONNECTOR ASSEMBLY

Field of the Invention

This invention generally relates to the art of electrical connectors and, particularly, to an electrical connector assembly for effecting a connection between two circuit boards.

Background of the Invention

A variety of electrical connectors have been used to make electrical connections between the circuits on different printed circuit boards. These printed circuit boards must be joined together with connectors in a manner to effectively and reliable interconnect the circuits on one circuit board to the circuits on another circuit board. This is done by a pair of mating connectors which are surface mount connectors and may include a male or plug connector mateable with a female or receptacle connector to form a "board- to-board" electrical connector assembly.

Figure 27, herein, shows an example of a typical board-to-board electrical connector assembly as might be seen in Japanese Patent Laid Open No. 08-148240 A (Fig.

9). As shown, a plug or male connector, generally designated 32, is inserted into a receptacle or female connector, generally designated 34, in the direction of arrow "A". The male connector includes a plurality of conductive terminals 36 which engage a plurality of conductive terminals 38 of the female connector. Terminals 36 of plug connector 32 are connected to circuit traces 40 on a first circuit board 42 by a plurality of solder connections

44. Terminals 38 of female connector 34 are connected to circuit traces 46 on a second circuit board 48 by a plurality of solder connections 50. The connectors are shown in Figure

7 by full lines in their unmated condition and by phantom lines in their mated condition.

With the ever-increasing tendency in the electronics industry to miniaturize overall systems and, thereby, miniaturize all electrical components, it is desirable that board- to-board electrical connectors not only have low profiles, but the spacing "S" between the two circuit boards in the mated condition of the connectors be as small as possible. Unfortunately, as the number of terminals and the number of solder connections 44 and 50 become large, it becomes more difficult to reduce the spacing "S" between the two circuit boards.

Therefore, proposals have been made in the prior art to reduce this spacing, as is seen in Japanese Patent Laid Open No. 2001-273949 A (Figs. 1 and 2) and as shown in Figures 28 and 29 herein. As shown, a female connector, generally designated 52, receives a male connector, generally designated 53. The male connector is surface mounted to a first circuit board 54, and female connector 52 is surface mounted to a second circuit board 55. Again, the connectors are shown in Figure 29 by full lines in their unmated condition and by phantom lines of the male connector in its fully mated condition. The male connector is mateable with the female connector in the direction of arrow "A" (Fig. 29). Male connector 53 includes a plurality of conductive terminals 56 which are connected to appropriate circuit traces on circuit board 54 by a plurality of solder connections 44. Female connector 52 includes a plurality of conductive terminals 57 connected to appropriate circuit traces on circuit board 55. hi order to reduce the spacing between circuit boards 54 and 55 when connectors 52 and 53 are mated as shown in Figure

29, a mating face 58 of female connector 52 is provided with recessed areas 59 which accommodate solder connections 44 of male connector 53. The recessed areas 59 can best be seen in Figure 28. By providing the recessed areas in the mating face of the female connector, circuit boards 54 and 55 can be brought closer together during mating of the connectors.

Unfortunately, both of the prior art connectors shown in Figure 27 as well as in Figures 28 and 29 present problems of allowing dust and dirt to enter the mating interface area of the connectors and accumulate on the mating terminals which could conceivably cause electrical contact failure caused by accumulation of the dust and dirt. Access to the mating terminals in Figure 27 is quite clear, and Figure 29 shows how recessed areas 59 are open at the sides of the connector assembly to allow dust and dirt to migrate into the connecting interface of the terminals.

Figure 30 shows another electrical connector assembly according to the prior art and as shown in Japanese Patent Laid Open No. 2000-260509 A (Fig. 1). As shown, a male connector 60 is mateable with a female connector 62. The male connector includes a plurality of conductive terminals 63 having contact portions 64 which are engaged by contact portions 65 of a plurality of conductive terminals 66 of male connector 62. Terminals 63 of the female connector are connected to appropriate circuit traces 67 on a first circuit board 68 by solder connections 44. Terminals 66 of female connector 62 are connected to appropriate circuit traces 69 on a second circuit board 70 by solder connections

44. This connector structure as shown in Figure 30 points out another problem with board- to-board connector assemblies in that it is very difficult, if at all possible, to determine when the male and female connectors are fully mated. In other words, contact portions 65 of terminals 66 of male connector 62 simply ride along straight surfaces of contact portions 64 of terminals 63 of female connector 60. This smooth sliding relationship of the contact portions of the two connectors do not give any tactile indication or "feel" when the connectors are mated. In order to solve the above problems of the prior art connector assembly shown in Figure 30, Figure 31 shows a terminal 63 having a contact portion 64 engageable by a contact portion 65 of a terminal 66 corresponding to the terminals described above in relation to Figure 30. However, it should be noted in Figure 31 that terminal 63 has a recessed or cut-out area 71 into which contact portion 65 of terminal 66 "snaps" in order to provide some form of tactile indication of the mating of the connectors. Unfortunately, due to the increasing miniaturization of such connector assemblies, this recessed area 71 is so small that very little "feel" actually can be sensed by an operator.

The present invention is directed to solving the various problems of the prior art described above and particularly to the provision of a board-to-board electrical connector assembly which effectively reduces the spacing between two circuit boards when a pair of connectors are mated and effectively prevents dust and dirt from migrating to the interfacing area of contact between the respective terminals of the mating connectors.

Summary of the Invention

An object, therefore, of the invention is to provide a new and improved board-to-board electrical connector assembly for effecting a connection between two circuit boards. In the exemplary embodiment of the invention, the connector assembly includes a first connector having a dielectric housing including a mounting face for mounting the connector on a first circuit board and a mating face having a mating recess. A plurality of first terminals are mounted on the dielectric housing and each terminal includes a tail portion for connection to an appropriate circuit trace on the first circuit board and a contact portion exposed generally at the mating recess. A second connector has a dielectric housing including a mounting face for mounting on a second circuit board and a mating projection for insertion into the mating recess of the first connector. A plurality of second terminals are mounted on the dielectric housing of the second connector and each second terminal includes a tail portion for connection to an appropriate circuit trace on the second circuit board and a contact portion for engaging the contact portion of one of the first terminals of the first connector. The dielectric housings of the first and second connectors are structurally configured such that the second circuit board mounted to the housing of the second connector closes the mating recess of the housing of the first connector when the connectors are mated. Therefore, dust and dirt cannot migrate to the interfacing contact area between the terminals of the two connectors because the second circuit board of the second connector closes the mating recess of the first connector.

As disclosed herein, the first terminals are mounted in a plurality of terminal- receiving passages in the dielectric housing of the first connector. The housings of the two connectors are structurally configured such that the second circuit board mounted to the housing of the second connector closes the terminal-receiving passages in the housing of the first connector when the connectors are mated, hi the preferred embodiment, the dielectric housing of the second connector is sized to be substantially entirely disposed in the mating recess of the housing of the first connector when the connectors are mated.

According to one aspect of the invention, the first terminals are mounted in a plurality of terminal-receiving passages at inside edges of the mating recess in the dielectric housing of the first connector. The passages are closed at outer sides thereof and open at inner sides thereof communicating with the mating recess. Each of the first terminals includes a body portion secured in a respective one of the terminal-receiving passages. A first arm portion of each first terminal projects from one end of the body portion through the dielectric housing of the first connector and defines the tail portion for connection to the first circuit board. A second arm portion of each first terminal projects from an opposite end of the body portion into the mating recess and defines the contact portion for engaging the contact portion of one of the second terminals of the second connector.

According to another aspect of the invention, the second terminals are mounted in a plurality of terminal-receiving passages at outside edges of the dielectric housing of the second connector. The passages are closed at inner sides thereof and open at outer sides thereof. Each of the second terminals includes a body portion secured in a respective one of the terminal-receiving passages. A first arm portion of each second terminal projects from one end of the body portion out of the dielectric housing of the second connector and defines the tail portion for connection to the second circuit board. A second arm portion of each second terminal projects from the dielectric housing and defines the contact portion for engaging the contact portion of one of the first terminals of the first connector. The invention contemplates that the first arm portion of each second terminal be convex on a side thereof facing the second circuit board to form a solder storage cavity to facilitate solder connection of the tail portion of the second terminal to a respective one of the circuit traces of the second circuit board. According to a further aspect of the invention, the dielectric housing of the first connector includes a positioning hole in a bottom wall of the mating recess. The dielectric housing of the second connector includes a positioning projection for insertion into the positioning hole during mating of the connectors. The positioning projection has chamfered sides to facilitate guiding the positioning projection into the positioning hole. In the exemplary embodiment of the invention, the mating recess in the dielectric housing of the first connector is generally rectangular. Four of the positioning holes are provided at four corners of the rectangular recess. A complementary four positioning projections are provided on the dielectric housing of the second connector.

Other objects, features and advantages of the invention will be apparent from the following detailed description taken in connection with the accompanying drawings. Brief Description of the Drawings

The features of this invention which are believed to be novel are set forth with particularity in the appended claims. The invention, together with its objects and the advantages thereof, may be best understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements in the figures and in which:

FIGURE 1 is a perspective view, partially in section and partially in phantom, of a board-to-board electrical connector assembly according to a first embodiment of the invention, in conjunction with the ends of a pair of circuit boards; FIGURE 2 is an enlarged, fragmented perspective view of the full-lined portion of the assembly in Figure 1;

FIGURE 3 is a view similar to that of Figure 1, but only of the female connector mounted to a first circuit board shown in phantom;

FIGURE 4 is a view similar to that of Figure 3, but of the male connector mounted to a second circuit board shown in phantom;

FIGURE 5 is a fragmented perspective view, partially in section, of the male and female connectors in unmated condition;

FIGURE 6 is a top plan view of the female connector;

FIGURE 7 is a side elevational view of the female connector looking in the direction of arrow "NIT' in Figure 6;

FIGURE 8 is a side elevational view of the female connector looking in the direction of arrow "NIII" in Figure 6;

FIGURE 9 is a top plan view of the male connector;

FIGURE 10 is a side elevational view of the male connector looking in the direction of arrow "X" in Figure 9;

FIGURE 11 is a side elevational view of the male connector looking in the direction of arrow "XI" in Figure 9;

FIGURE 12 is an enlarged vertical section through the male and female connectors in unmated condition; FIGURE 13 is a view similar to that of Figure 12, but with the male and female connectors in an initial position of mating;

FIGURE 14 is a view similar to that of Figure 13, but with the connectors in the process of further being mated; FIGURE 15 is a view similar to that of Figure 14, but with the connectors fully mated;

FIGURE 16 is an enlarged view of the area encircled at "XNI" in Figure 15;

FIGURE 17 is an enlarged vertical section taken generally along line XNII- XNII in Figure 1;

FIGURES 18-21 are views similar to that of Figures 1-4, but of a second embodiment of the invention;

FIGURES 22-25 are views similar to that of Figures 12-15, but of the second embodiment of the invention; FIGURE 26 is an enlarged vertical section taken generally along line 26-26 in Figure 18; and

FIGURES 27-31 are views of the prior art connector assemblies as already described in the "Background", above.

Detailed Description of the Preferred Embodiments

Referring to the drawings in greater detail, Figures 1-17 show a first embodiment of the invention, and Figures 18-26 show a second embodiment of the invention. Referring first to the embodiment of Figures 1-17, the invention is incorporated in a board-to-board electrical connector assembly, generally designated 72, which includes a first or female connector, generally designated 73, mateable with a second or male connector, generally designated 74. Female connector 73 is surface mounted to a first printed circuit board 75, and male connector 74 is surface mounted to a second printed circuit board 76. Therefore, the two connectors 73 and 74 effect connection between the two circuit boards 75 and 76.

More particularly, referring specifically to Figures 6-8 in conjunction with Figures 1-5, female connector 73 includes a dielectric housing, generally designated 77, which, has a rectangular shape and which may be unitarily molded of plastic material. A plurality of conductive terminals, generally designated 78, are mounted in housing 77. The terminals are arranged along two sides of the housing as best seen in Figure 6. Four metal fitting nails 79 are engaged with the housing at the outside four corners thereof for securing the female connector to circuit board 75. As is known, the fitting nails are soldered to appropriate mounting pads on the circuit board.

Housing 77 of female connector 73 includes a mating face, generally designated 77a, having a rectangular mating recess 77b for matingly receiving male connector 74 therein. The mating recess is bounded by opposite sides 77c and opposite sides 77d of the housing. The mating recess has a bottom wall 77e which is provided with four positioning holes 80 therethrough at the four corners of rectangular mating recess 77b as seen best in Figure 6. The mating recess is chamfered, as at 77f to facilitate insertion thereinto of the male connector. The housing is provided with four slots 77g into which fitting nails 79 are press-fit. Finally, a plurality of terminal-receiving passages 82 are formed through opposite sides 77d of the housing for mounting terminals 78 in two rows at opposite sides of the connector.

Referring particularly to Figures 9-11 in conjunction with Figures 1-5, male connector 74 includes a generally rectangular, molded plastic housing, generally designated

83, which is small enough to be entirely disposed within mating recess 77b of housing 77 of female connector 73 when the male and female connectors are mated as seen in Figures 1 and 2. Housing 83 mounts a plurality of conductive terminals, generally designated 84, which are mounted in a plurality of terminal-receiving passages 83a at opposite sides of the housing as seen in Figure 9. Two metal fitting nails 85 are press-fit into a pair of slots 83b at opposite ends of the housing and are secured, as by soldering, to appropriate mounting pads on circuit board 76. Terminal-receiving passages 83a and slots 83b extend from an upper surface 83c and a lower surface 83d of the housing. As will be seen in greater detail hereinafter, contact portions of terminals 84 are exposed at opposite sides 83e of housing 83. The housing has corner portions 83f which project outwardly at opposite sides of fitting nails 85. Finally, four positioning projections 86 are molded integrally with housing 83 at the four corners of the rectangular housing for positioning into positioning holes 80 (Fig.6) of housing 77 of female connector 73 when the connectors are mated. The edges of positioning projections 86 are chamfered to facilitate guiding the positioning projections into positioning holes 80.

Referring to Figures 2 and 12, it can be seen that terminal-receiving passages 82 which extend through opposite sides 77d of housing 77 of female connector 73 are closed at outer sides thereof and are open at inner sides thereof, hi other words, passages 82 communicate with mating recess 77b of the female connector. Each terminal 78 includes a main body portion 78a which includes teeth 78b for skiving into the plastic material of the housing at opposite sides of a respective passage 82. The terminals may be stamped and formed of conductive sheet metal material, and teeth 78b are stamped at opposite edges of body 78a. A first arm portion 78c projects from one end of body portion 78a through the dielectric housing and forms a tail portion for solder connection to appropriate circuit traces 75a (Fig. 3) of circuit board 75. A second arm portion 78d projects from an opposite end of body portion 78a and into mating recess 77b to a contact portion 78e for engaging the contact portion of one of the terminals 84 of male connector 74, as will be seen hereinafter. As seen best in Figure 12, contact portion 78e is rounded in configuration and reference numeral 78f defines the point that the contact portion projects furthest into mating recess 77b furthest from the main body portion 78a. The edge of the rounded contact portion extends at an angle back toward the body portion 78a along the edge of a distal end 78g which projects into the mating recess a lesser degree or distance than maximum point of projection 78f. This configuration forces the first and second connectors together when the contact portion of the male terminal 84 slides beyond the maximum point of projection 78f. Still referring primarily to Figures 2 and 12, it can be seen that terminal- receiving passages 83a in housing 83 of male connector 74 are located at opposite edges of the housing. Therefore, the passages are closed at inner sides thereof and open at outer sides thereof. Each terminal 84 includes a main body portion 84a with teeth 84b at opposite edges of the body portion for biting into the plastic material at opposite sides of the respective terminal-receiving passage 83a. Like terminals 78, terminals 84 are stamped and formed of conductive sheet metal material, and teeth 84b are stamped at opposite edges of body portion 84a so that the terminals can be press-fit into passages 83e.

Each terminal 84 of male connector 74 includes a first arm 84c which projects from one end of body portion 84a out of dielectric housing 83 and defines a tail portion for connection to a circuit trace 76a (Fig. 4) on circuit board 76. Arm portion 84c is bent so that it is convex on a side thereof that faces circuit board 76 to form a convex section 84d that provides a solder storage cavity for storing solder 87 by surface tension to facilitate a good solder connection between tail portion 84c and a respective one of the circuit traces 76a on circuit board 76.

Each terminal 84 of male connector 74 further includes a second arm 84e which is bent, as at 84f, outwardly from body portion 84a to a contact portion 84g that projects outwardly of the respective terminal-receiving passage 83a, for engaging contact portion 78e of a respective one of the terminals 78 of female connector 73. Figures 12- 17 are sequential views showing the mating of connectors 73 and

74, as male connector 74 is mated with female connector 73. The male connector is inserted into mating recess 77b of the female terminal in the direction of arrow "A" (Fig. 12). With convex sections 84d of terminals 84 of the male connector 74 providing solder storage cavities for solder material 87, the eventual spacing between the circuit boards is reduced after the connectors are completely mated.

Figure 13 shows contact portions 84e of terminals 84 of male connector 74 having come into engagement with contact portions 78e of terminals 78 of female connector 73. This is the first engagement of the terminals of the respective connectors when male connector 74 is inserted into mating recess 77b of the female terminal in the direction of arrow "A".

As male connector 74 is further mated with female connector 73, the contact portions of terminals 84 of the male connector ride along the contact portions 78e of terminals 78 of the female connector as shown in Figure 14. The contact portions of the terminals of the male connectors eventually ride over and around the maximum points of projection 78f of contact portions 78e of terminals 78 as the contact portions are biased outwardly as indicated by the full lines and phantom lines in Figure 14.

Figures 15-18 show male connector 74 fully mated with female connector 73 as the male connector is inserted completely into mating recess 77b of the female connector.

It can be seen in Figure 15 that housing 83 of the male connector has bottomed out onto the top of bottom wall 77e of housing 77 of the female connector. The contact portions of terminals 84 of the male connector have now moved onto distal ends 78g of contact portions 78e of terminals 78 of the female connector. In essence, as the contact portions of the terminals of the male connector engage the contact portions of the terminals of the female connector in an initial point of engagement as shown in Figure 13, minimal engaging or mating forces are encountered. As the contact portions of the terminals of the male connector ride over the maximum points of projection 78f of the terminals of the female connector, maximum forces are encountered until the contact portions of the terminals of the male connector reach the final mated positions at the distal ends 78g of the terminals of the female connector, whereat minimal mating forces again are encountered at the fully mated condition of the connectors. This not only provides a good contact engagement between all of the terminals, but a good latching means is provided between the connectors, and a distinct tactile indication or "feel" is given that the connectors are fully mated. Figures 15-17 also show a unique feature of the invention wherein circuit board 76 completely closes mating recess 77b when the connectors are mated. In fact, due to the structural configuration of the two connectors, not only is the mating recess 77b completely closed, but terminal-receiving passages 82 for terminals 78 of the female connector and terminal-receiving passages 83a of the male connector also are completely closed at the mating interface of the terminals. As seen best in Figure 15, not only is housing 83 of the male connector completely contained within mating recess 77b, but substantially the entirety of the male connector is disposed within the mating recess. Therefore, circuit board 76 engages mating face 77a of the female connector housing as seen in Figure 15, completely around mating recess 77b to form a closed space 90. Consequently, dust and dirt is prevented from entering the interfacing area between the connectors, and the dust and dirt cannot accumulate on the contact portions of the terminals which, otherwise, would contaminate the engaging surfaces of the terminal contact portions. To help ensure that the printed circuit board 76 closes the mating recess 77b, the terminal configuration as discussed above causes the connectors to be pulled together after the contact portion of the male terminals ride over the maximum point of projection 78f of the female terminals. This will force the board 76 to remain in contact with side 77d of housing 77 even if the board and housing are not completely co-planar. When using terminals without this pull, one or more terminals could slip partially out of engagement with each other, while maintaining electrical continuity, h this situation one edge of the board could be located away from the housing exposing the recess 77b with contaminates.

Figures 18-22 show a second embodiment of the invention incorporated in a board-to-board electrical connector assembly, generally designated 101, which includes a first or female connector, generally designated 107, and a second or male connector, generally designated 109. The female connector again is surface mounted on a first circuit board 75, and male connector 109 is surface mounted on a second circuit board 76. Referring to Figure 21 in conjunction with Figures 18, 19 and 22, female connector 107 includes a molded plastic housing, generally designated 111, which has a rectangular configuration and which mounts a plurality of terminals, generally designated 113. The terminals are mounted at constant pitch along two opposite sides of the housing as seen best in Figure 21. Four metal fitting nails 115 are used to surface mount the housing to circuit board 75 similar to that described above in relation to the first embodiment.

Housing 111 of female connector 107 has a mating recess 11 la bounded by two opposite long sides 11 lb and two opposite short sides 111c. A central "island" portion

114 runs down the center of mating recess Ilia lengthwise thereof. The central island portion has opposite convex sides 114a as seen in Figure 22. Terminals 113 are mounted in a plurality of terminal-receiving passages 123 in opposite long sides 111b of the housing. Finally, as in the first embodiment of the invention, four positioning holes 112 (Fig.21) are formed through a bottom wall 11 Id (Fig. 22) of the housing.

As best shown in Figure 21, housing 111 of female connector 107 mounts two rows of terminals 113 on the opposite sides of central island portion 114. The terminals maybe stamped and formed of conductive sheet metal material, and the configuration of the terminals are best shown in Figure 22. Specifically, the terminals are mounted in long side portions 11 lb of the housing. Each terminal includes a main or body portion 117 which is generally E-shaped in a sideways direction and includes a main horizontal portion 117a located in a passage 123; a center leg 117b press-fit into a hole 123a of the passage; an inside leg 117c located in a groove portion 123b of the passage at the inside of long side 11 lb of the housing; and an outside leg 117d located in a groove 123c of the passage at the outside of long side 11 lb of the housing. An arm 120 extends inwardly from the distal end of inside leg 117c away from the center leg 117b adjacent a bottom wall of the housing 111 to an upwardly extending arm portion 120b which terminates in a contact portion 120a. Arm portion 120b is located in the convex side 114a on one side of central island portion

114 of the housing. Arm portion 120b and contact portion 120a can flex as shown by the full and phantom lines in Figure 22. Because arm 120 is longer than arm portion 120b, the arm 120 will flex in the direction toward the bottom wall of the housing 111 before the contact portion 120a flexes away from the center leg 117b. This results in better tracking between the edge of contact portion 120a and the contact arms 121a. The distal ends of outside legs 117d of terminals 107 are connected, as by soldering, to circuit traces 75a of circuit board 75 as seen in Figure 21. Finally, as seen clearly in Figure 22, long side portions 11 lb and central portion 114 of housing 111, in conjunction with inside leg 117c, arm 120 and arm portion 120b of terminals 107, form two mating recess portions 100 which run longitudinally of the female connector as seen in Figure 21.

Referring particularly to Figures 20 and 22, male connector 109 includes a housing, generally designated 118, which mounts two rows of terminals, generally designated 121. The housing has a flat wall 118a and two long side portions 118b which form an elongated channel therebetween. Terminals 121 are mounted in the same number and at the same pitch as terminals 113 of female connector 107. Housing 18 is generally rectangular, and four chamfered positioning projections 119 are formed at four corners of the housing as seen clearly in Figure 20. Finally, terminals 121 are mounted in terminal- receiving passages 124 in long side portions 118b of the housing. As seen in Figure 18, four metal fitting nails 116 are press-fit into grooves 116a in long side portions 118b for securing the male connector to circuit board 76.

As best seen in Figure 22, each terminal 121 includes a contact arm 121a which projects from one end of a body portion 121b which is press-fit into a respective one of the teπninal-receiving passages 124. Another arm 121c extends from the opposite end of body portion 121b and forms a tail portion for connection, as by soldering, to a circuit trace 76a (Fig.20) of circuit board 76. Contact arm 121a is concave to function similar to contact portions 78e (Fig. 12) of terminal 78. In other words, a maximum point of projection 121d is formed by the concave contact arm which has a distal end 12 le. Figures 22-26 are sequential views showing the progression of mating of male connector 109 into female connector 107 of the second embodiment of the board-to- board electrical connector assembly 101. Specifically, Figure 23 shows a condition of initial engagement of contact arms 121a of terminals 121 of male connector 109 with contact portions 120a of terminals 113 of female connector 107. Contact arm portions 120b of terminals 113 are not yet flexed.

Figure 24 shows contact arms 121a of terminals 121 flexing contact arms 120b of terminals 13 as contact portions 120a of terminals 113 ride over the maximum points of projection 121 d of contact arms 121a. Figures 25 and 26 show the fully mated condition of male connector 109 in female connector 107. Long side portions 118b of housing 118 of male connector 109 move the two recess portions 100 of mating recess Ilia of female connector 107. It can be seen that, like the first embodiment of Figures 1-17, substantially the entire male connector 109 is disposed within mating recess Ilia of the female connector, and circuit board 76 engages a top mating surface 130 of housing 111 of the female connector. This completely closes mating recess Ilia of the female connector to prevent dust and dirt from migrating into the mating interface of the connectors and the engaging interface of the terminals, as described in detail above in regard to the first embodiment of Figures 1-18. hi essence, a closed space 129 (Fig. 25) is defined between the connectors, and the entire male connector 109, including terminals 121, are received in this closed space when the connectors are mated.

Air flow is prevented from entering this closed space and, therefore, dust and dirt are extremely unlikely to enter the closed space whereby contact failure due to the dust and dirt is effectively avoided. The terminal configuration, as discussed with regard to the first embodiment, pulls the connectors together thus helping to ensure that board 76 engages the top mating surface 130 of housing 111 of the female connector. Like the first embodiment, this structural combination also is effective in environments of high humidity or where corrosion gases are generated.

It will be understood that the invention may be embodied in other specific forms without departing from the spirit or central characteristics thereof. The present examples and embodiments, therefore, are to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein.

Claims

1. A board-to board electrical connector assembly for effecting a connection between two circuit boards, comprising: a first connector having a first dielectric housing including a mounting face for mounting the connector on a first circuit board and a mating face having a mating recess; a plurality of first terminals mounted on the first dielectric housing and each terminal including a tail portion for connection to an appropriate circuit trace on the first circuit board and a contact portion exposed generally at said mating recess; a second connector having a second dielectric housing including a mounting face for mounting on a second circuit board and a mating projection for insertion into the mating recess of the first connector; a plurality of second terminals mounted on the second dielectric housing of the second connector and each second terminal including a tail portion for connection to an appropriate circuit trace on the second circuit board and a contact portion for engaging the contact portion of one of the first terminals of the first connector; and said first and second dielectric housings being structurally configured such that the second circuit board mounted to the second housing of the second connector closes said mating recess of the first housing of the first connector when the connectors are mated.

2. The board-to-board electrical connector assembly of claim 1 wherein said first tenninals are mounted in a plurality of terminal-receiving passages in the first dielectric housing of the first connector, and the first and second dielectric housings are structurally configured such that the second circuit board mounted to the second housing of the second connector closes said terminal-receiving passages in the first housing of the first connector when the connectors are mated.

3. The board-to-board electrical connector assembly of claim 1 wherein said secomd dielectric housing of the second connector is sized to be substantially entirely disposed in the mating recess of the first housing of the first connector when the connectors are mated.

4. The board-to-board electrical connector assembly of claim 1 wherein said tail portions of the second terminals are convex on a side of the tail portions connected to the circuit traces of the second circuit board to form solder storage cavities to facilitate solder connection of the tail portions to the circuit traces.

5. The board-to-board electrical connector assembly of claim 1 wherein said first terminals are mounted in a plurality of terminal-receiving passages at inside edges of the mating recess in the first dielectric housing of the first connector, the passages being closed at outer sides thereof and open at inner sides thereof communicating with said mating recess.

6. The board-to-board electrical connector assembly of claim 5 wherein each of said first terminals includes a body portion secured in a respective one of said terminal- receiving passages, a first arm portion projecting from one end of the body portion through the first dielectric housing of the first connector and defining the tail portion for connection to the first circuit board, and a second arm portion projecting from an opposite end of the body portion into said mating recess and defining the contact portion for engaging the contact portion of one of the second tenninals of the second connector.

7. The board-to-board electrical connector assembly of claim 1 wherein said second tenninals are mounted in a plurality of terminal-receiving passages at outside edges of the second dielectric housing of the second connector, the passages being closed at inner sides thereof and open at outer sides thereof.

8. The board-to-board electrical connector assembly of claim 7 wherein each of said second terminals includes a body portion secured in a respective one of said terminal-receiving passages, a first arm portion proj ecting from one end of the body portion out of the second dielectric housing of the second connector and defining the tail portion for connection to the second circuit board, and a second arm portion proj ecting from the second dielectric housing and defining the contact portion for engaging the contact portion of one of the first terminals of the first connector.

9. The board-to-board electrical connector assembly of claim 8 wherein said first arm portion of each second terminal is convex on a side thereof facing the second circuit board to form a solder storage cavity to facilitate solder connection of the tail portion of the second terminal to a respective one of the circuit traces of the second circuit board.

10. The board-to-board electrical connector assembly of claim 1 wherein the first dielectric housing of said first connector includes a positioning hole in a bottom wall of said mating recess, and the dielectric housing of said second connector includes a positioning projection for insertion into the positioning hole during mating of the connectors.

11. The board-to-board electrical connector assembly of claim 10 wherein said positioning projection has chamfered sides to facilitate guiding the positioning projection into the positioning hole.

12. The board-to-board electrical connector assembly of claim 11 wherein said mating recess in the first dielectric housing of the first connector is generally rectangular, and including four of said positioning holes at four comers of the rectangular recess, and including a complementary four positioning projections on the dielectric housing of the second comiector.

13 A board-to board electrical connector assembly for effecting a connection between two circuit boards, comprising: a first connector having a first dielectric housing including a mounting face for mounting the connector on a first circuit board and a mating face having a mating recess; a plurality of first terminals mounted on the first dielectric housing and each terminal including a body portion secured in the first dielectric housing, a first arm potion 120 projecting from one end of the body portion through the first dielectric housing of the first connector and defining a tail portion for connection to a circuit trace on the first circuit board, and a second arm portion projecting from an opposite end of the body portion into said mating recess adjacent a bottom wall of the first dielectric housing with a bent arm portion extending from the first arm portion away from the bottom wall of the housing to facilitate more movement in the bent arm portion than in the first arm portion, the bent arm portion having a first contact portion exposed generally at the mating recess, a second connector having a second dielectric housing including amounting face for mounting on a second circuit board and a mating projection for insertion into the mating recess of the first connector; a plurality of second terminals mounted on the second dielectric housing of the second connector and each second terminal including a tail portion for connection to an appropriate circuit trace on the second circuit board and a second contact arm for engaging the contact portion of one of the first terminals of the first connector; and said first and second dielectric housings being structurally configured such that the second circuit board mounted to the second housing of the second connector closes said mating recess of the first housing of the first connector when the connectors are mated.

14. The board-to-board electrical connector assembly of claim 13 wherein the second contact arm portion of the second terminal has a maximum point of projection, extending furthest into the recess and located a distance furthest from the main body portion, which engages the contact portion of the first terminals.

15. The board-to-board connector of claim 14 wherein a distal end extends from the maximum point of projection into the recess a lesser distance from the main body portion than the distance of the maximum point of projection, whereby which, when the contact portion of the first terminal passes the maximum point of projection, the first and second connectors are forced together.