Electrical connector

An electrical connector mounted to a PCB comprises a housing unit, a contact unit and a pair of boardlocks. The housing unit has a projection with a number of pairs of upper and lower passageways defined therethrough and a pair of slots formed in opposite sides thereof. The contact unit includes a number of pairs of upper and lower contacts respectively received in the upper and lower passageways of the housing unit. Each upper and lower contact in a pair has a bent portion bent in opposite directions from mating portions of the contacts for engaging with contacts in a complementary connector, whereby mounting tails of the contacts are spaced from each other a distance when the mating portions are received in the contact passageways in a manner that they are vertically aligned with each other. The mounting tails are used for mounting the connector to a printed circuit board by Surface Mounting Technology. The boardlocks are received in the slots of the housing unit. Each boardlock has a pair legs and a solder pad on opposite sides thereof.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to an electrical connector, and particularly
 to an electrical connector having a high density of contacts retained
 therein.
 2. Description of Prior Art
 Generally, a conventional electrical connector having a high density of
 contacts retained therein is mounted on a printed circuit board (PCB) for
 electrical connection with the PCB. An arrangement of the contacts may be
 in several rows, such as upper and lower rows. The upper and lower rows of
 contacts of some conventional connectors are often offset from each other
 whereby each contact extends downwardly to form a terminating portion for
 terminating at the PCB without contacting adjacent contacts. Examples of
 such conventional electrical connectors are disclosed in Taiwan Patent
 Application Nos. 78212155, 79204276, 79214090, 80202277, 80209366 and
 80213361 and U.S. Pat. Nos. 4,857,017; 4,955,819 and 5,451,158.
 However, upper and lower rows of contacts of some connectors are aligned.
 Thus, the terminating portions of different rows extending downwardly may
 cause a short circuit between adjacent contacts.
 SUMMARY OF THE INVENTION
 Accordingly, an object of the present invention is to provide an electrical
 connector having upper and lower rows of aligned contacts with terminating
 portions thereof offsetting from each other for properly attaching to a
 PCB.
 In the preferred embodiment of the present invention, an electrical
 connector mounted to a PCB comprises a housing unit, a contact unit and a
 pair of boardlocks. The housing unit has a projection with a plurality of
 upper and lower passageways defined therethrough and a pair of slots
 formed in opposite lateral sides thereof. The contact unit includes a
 plurality of pairs of upper and lower contacts respectively received in
 the upper and lower passageways of the housing unit. Mating portions of
 each pair of upper and lower contacts are vertically aligned, while tail
 portions thereof are offset from each other, when the contacts are mounted
 in a housing of the connector. The boardlocks are received in the slots of
 the housing unit. Each boardlock has a pair legs and a solder pad on
 opposite sides thereof.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
 Referring to FIGS. 1 to 3, an electrical connector in accordance with the
 present invention comprises a housing unit 1, a contact unit 2 received in
 the housing unit 1 and a pair of boardlocks 3 attached to the housing unit
 1. The housing unit 1 comprises a body portion 10 which forms a projection
 11 extending from a front surface thereof. Upper and lower rows of
 passageways 111, 112 aligned with each other are formed through the
 projection 11. A frame 14 forms a receiving opening 140 for receiving the
 projection 11 therein. A pair of slots 12 (only one shown) is formed in
 opposite sides of the frame 14. A pair of cutouts 13 (only one shown) is
 formed on the opposite lateral sides of the frame 14 proximate and outside
 the slots 12, respectively.
 Each boardlock 3 has a generally inverted U-shaped body 31 with an inner
 wall 311, an opposite outer wall 312 and a horizontal wall 313 connecting
 the inner and outer walls 311, 312. The inner wall 311 is used for being
 interferentially received in the slots 12 of the frame 14. The horizontal
 and outer walls 313, 312 are used to override on the lateral sides of the
 frame 1 when the boardlocks 3 are mounted to the frame 14, wherein the
 outer walls 312 are received in the cutouts, respectively. A pair of legs
 32 downwardly extended from a lower edge of the inner wall 311 for having
 an interference fit with a printed circuit board (not shown) on which the
 connector 1 is mounted. A solder pad 33 horizontally extends from a lower
 edge of the outer wall 312 for being soldered to the printed circuit board
 by Surface Mounting Technology (SMT) to enhance connection between the
 connector 1 and the circuit board (not shown). A pair of holes 331 is
 formed in each of the solder pad 33 for facilitating soldering the
 boardlock 3 to the printed circuit board.
 Further referring to FIG. 4, the contact unit 2 includes a plurality of
 pairs of upper and lower contacts 21, 22 respectively received in the
 upper and lower passageways 111, 112 of the housing unit 1. Each upper and
 lower contact 21, 22 in each pair includes a mating portion 211, 221 and a
 terminating portion 214, 224 extending from the mating portion 211, 221.
 Each mating portion 211, 221 has a fork-like front portion 210, 220 for
 engaging with a mating portion of a contact of a complementary connector
 (not shown). Each mating portion 211, 221 further forms two pairs of barbs
 212, 222 on opposite edges thereof for being interferentially received in
 the passageways 111, 112, and a shoulder 213, 223 proximate the
 terminating portion 214, 224 for facilitating insertion of the mating
 portions 21, 22 into the corresponding passageways 111, 112. The
 terminating portions 214, 224 form bent portions 215, 225 extending in
 opposite directions from the mating portions 21, 22. Mounting tails 216,
 226 for being mounted on the circuit board are coplanarly extended from
 bottom edges of the terminating portions 214, 224 in a horizontal
 orientation, respectively. Therefore, when the mating portions 21, 22 are
 received in the contact passageways 111, 112 so that the mating portions
 21, 22 are vertically aligned with each other, the mounting tails 216, 226
 are spaced from each other a distance. Each mounting tail 216, 226 forms a
 chamfer 217, 227 facing the circuit board for enhancing soldering effects.
 The thickness of each mating portion 211, 221 is 0.4 mm for withstanding a
 mating force. The thickness of each terminating portion 214, 224 is 0.25
 mm for allowing the mounting tails 216, 226 of the upper and the lower
 contacts 21, 22 to be properly arranged in a line for surface mounting on
 the circuit board.
 It will be understood that the present invention may be embodied in other
 specific forms without departing from the spirit of the 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.