Electrical connectors – With coupling movement-actuating means or retaining means in... – Coupling part for receiving edge of planar board moving...
Reexamination Certificate
1997-04-25
2001-01-16
Vu, Hien (Department: 2833)
Electrical connectors
With coupling movement-actuating means or retaining means in...
Coupling part for receiving edge of planar board moving...
C439S630000
Reexamination Certificate
active
06174187
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field the Invention
The present invention relates to electrical connectors for connecting to a mother board a daughter board having a plurality of pads on a front edge thereof in a direction perpendicular, oblique, or parallel to the mother board.
2. Description of the Related Art
Recently, an increasing number of memory modules are used and there is a demand for an electrical connector for allowing high-density mounting. A conventional direct insertion type connector fails to meet the high-density mounting requirement and a variety of rotary type, zero-insertion-force connectors are used.
Japanese patent application Kokai Nos. 230378/85 and 193473/88 disclose such zero-insertion-force connectors. Contact terminals for the electrical connectors are made by stamping a metal sheet having a predetermined thickness. These contact terminals have a very high spring constant because they are stamped from flat work. Consequently, if the spring constant is set to provide a satisfactory contact power for PC boards of the minimum thickness, an excessive force is applied to PC boards of the maximum thickness, causing breakage or difficulty to plug. In addition, the contact terminals are made by stamping so that a considerable amount of rare metal material is wasted. Moreover, the contact terminals made by stamping have contact sections cut by the stamping so that the contact sections must be plated after stamping, resulting in the increased manufacturing costs.
Japanese patent application Kokai No. 78168/90 discloses contact terminals made by stamping and bending a metal sheet instead of those made by stamping alone. By stamping and bending it is possible to avoid the above problems with those made by stamping alone.
However, such an electrical connector has the following disadvantages. That is, since a daughter board is inserted and then rotated, the moment of rotations (in a direction to release the daughter board) warps the daughter board, or the positions of contact points of contact terminals vary with variations in the manufacturing precision, making uneven the contact power of the contact terminals. The warp of a daughter board makes different the contact power in upper and lower contact points and unstable the contact resistance.
Such disadvantages will be described in more detail with reference to
FIGS. 13 and 14
. As
FIG. 13
shows, an electrical connector of this type is mounted on a mother board
10
to connect a daughter board
30
such as a printed circuit board on which memory modules are mounted. The electrical connector
20
has an insulation housing
21
with an elongated opening
25
therein and a pair of latch levers
22
extending upwardly from opposite ends of the elongated opening
25
and having latch sections
23
at the upper portions thereof. A plurality of contact terminals are arranged in the insulation housing
21
along the elongated opening
25
. To connect the daughter board
30
to the electrical connector
20
on the mother board
10
, the daughter board
20
is inserted obliquely into the elongated opening
25
and rotated rearwardly. When the side edges of the daughter board contact the front faces of the latch sections
23
, the daughter board
30
flexes the latch levers
22
outwardly and passes the latch sections
23
. When the daughter board passes the latch sections
23
, the latch levers snap to the original position to hold the daughter board
30
with the rear faces of the latch sections
23
. This completes connection of the daughter board
30
to the electrical connector
20
.
FIG. 13
shows such connection conditions of the daughter board
30
to the electrical connector
20
.
Under such connection conditions as shown in
FIG. 13
, the daughter board
30
is biased to rotate forwardly by the contact terminals while the upper opposite side edges of the daughter board
30
are held by the latch sections
23
of the latch levers
22
to prevent the forward rotation. Consequently, the higher the moment of forward rotations applied to the daughter board
30
by the contact terminals, the larger the warp of the daughter board
30
as shown with an arrow W in FIG.
13
. As
FIG. 14
shows, the contact power of the rear contact terminals provided in the middle of the elongated opening
25
is decreased while the contact power of the front contact terminal provided at opposite ends of the elongated opening
25
is decreased, failing to provide stable two-point contacts.
The propositions made to solve such problems include reduction of the contact power of the contact terminals to thereby reduce the moment of rotations, minimizing the warp of a daughter board; holding projections molded with the insulation housing to correct the warped daughter board; and contact terminals made by drawing as shown in Japanese UM patent application Kokoku No. 9347/95.
However, the reduction of the contact power increases the contact resistance, reducing the contact reliability; the molded holding projections fails to meet the tolerance in thickness of daughter boards; and the drawn contact terminals have their own disadvantages.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide an economical electrical connector able to maintain the contact power and withstand the moment of rotations under connection conditions.
It is another object of the invention to provide an electrical connector able to maintain a certain level of contact power regardless of degrees of warp of the daughter board warp.
According to one aspect of the invention there is provided an electrical connector for connecting to a mother board a daughter board having a plurality of pads on a front edge thereof, which includes an insulating housing to be mounted on the mother board having front, bottom, and rear walls to define an opening into which the daughter board is inserted at an angle with the mother board and then rotated rearwardly to a connection position; a plurality of terminal receiving grooves provided in the front, bottom, and rear walls of the opening; a plurality of contact terminals provided in the terminal receiving grooves and made by stamping and bending a resilient conductive sheet so as to provide first retaining sections fixed in the terminal receiving grooves in either the front or rear walls, connection sections extending from the first retaining sections and electrically connected to conductors of the mother board, reverse U-shaped sections extending upwardly from the first retaining sections and then to inside of the opening to provide upper or lower contact portions, U-shaped sections extending from the reverse U-shaped sections toward either the front or rear wall and then upward along either the front or rear wall; and free end sections extending from the U-shaped sections toward inside of the opening to provide lower or upper contact portions; the reverse U-shaped, U-shaped, and free end sections constituting spring sections flexed at the first retaining sections; the upper and lower contact portions of the contact terminals being spaced at a distance equal to or slightly greater than a thickness of the front edge of the daughter board and brought into contact with the pads on the front edge with a predetermined contact force by rotating the daughter board rearwardly to flex the spring sections, with the spring sections being flexed at the first retaining sections so as to reduce a distance between the upper and lower contact portions in a direction of depth of the opening.
According to another aspect of the invention there is provided an electrical connector for connecting to a mother board a daughter board having a plurality of pads on a front edge thereof, which includes an insulating housing to be mounted on the mother board having front, bottom, and rear walls to define an opening into which the daughter board is inserted at an angle with the mother board and then rotated rearwardly to a connection position; a plurality of terminal receiving grooves provided in the front, bottom, and rear walls of the openi
Mtsuo Tsutomu
Sakata Tsuyoshi
Yaegashi Hirokatsu
Yamagami Yoku
Hirose Electric Co. Ltd.
Kanesaka & Takeuchi
Vu Hien
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