Surface mount device and use thereof

Details Surface mount device and use thereof Surface mount device and use thereof

1999-12-06

2002-07-23

Patel, Tulsidas (Department: 2839)

Electrical connectors

With circuit component or comprising connector which fully...

Termination circuit

C439S083000

Reexamination Certificate

active

06422901

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a surface mount device such as a resistor or diode, and to an electrical connector having such a surface mount device.
BACKGROUND OF THE INVENTION
As is known, a surface mount device (SMD) is an electrical device particularly useful in manufacturing circuit boards and the like. Such SMD may be a two-terminal device such as a resistor, a capacitor, an inductor, or a diode; a three-terminal device such as a transistor, a four-terminal device; etc.
In one preferred form of SMD, electrical leads do not extend therefrom. Instead, the SMD includes electrodes integral with the surface thereof. That is, such electrodes are positioned on a contact surface of the SMD such that the electrodes contact corresponding conductive pads on a substrate when the contact surface is brought into aligned contact with such substrate. Typically, a solder or the like is employed to securely bond the SMD to the substrate by way of the electrodes at the contact surface and the corresponding conductive pads and in doing so to maintain a good electrical connection between such electrodes and conductive pads.
As should be understood, then, the lack of electrical leads allows the aforementioned SMD to be relatively small as compared with a conventional circuit element having leads. Accordingly, the real estate used by such SMD on the underlying substrate (i.e., the circuit board) is also relatively small, with the net result being that more circuitry may be placed on the substrate in a smaller space if SMDs are employed as circuit elements.
In one typical two-terminal SMD
10
, such as that shown in
FIG. 1
, the actual circuit device (i.e., a resistor, a capacitor, an inductor, a diode such as an LED, etc.) is encased within a generally rectilinear block
12
, and each electrode
14
extends from a top side
12
t
to an end side
12
e
and then to a bottom side
12
b
of the block
12
. As maybe appreciated, the portions of the electrodes
14
at the bottom side
12
b
of the block
12
define a contact surface
16
that faces and at least partially contacts a substrate
18
, and such electrodes
14
at the contact surface
16
are positioned to align with corresponding conductive pads
20
on the substrate
18
.
A protrusion
22
may extend from the top side
12
t
of the block
12
between the electrodes
14
. Such protrusion
22
may for example contain the operative portion of an LED if in fact the SMD
10
is an LED. In addition, a mounting pad
24
may be present at the bottom side
12
b
of the block
12
between the electrodes
14
. Such mounting pad
24
forms a portion of the contact surface
16
along with the portions of the electrodes
14
at the bottom side
12
b
of the block
12
, and may assist in securely bonding the SMD
10
to the substrate
18
.
The SMD
10
as shown in
FIG. 1
is entirely appropriate for being mounted to the substrate
18
as shown, where the electrodes
14
at the contact surface
16
align with the corresponding conductive pads
20
on the substrate
18
. However, the SMD
10
may not be appropriate for being mounted to other substrates. For example, it may be desirable to mount a SMD
10
containing an LED to a conductive substrate such as a shield of an electrical device, where the LED SMD
10
is coupled to the electrical device and is present on the conductive shield of such electrical device as a visual indicator of some function of the electrical device. However, mounting such LED SMD
10
to such shield by way of the contact surface
16
of such LED SMD
10
would of course produce the unwanted effect of shorting out the LED SMD
10
.
Accordingly, a need exists for an SMD
10
that could be employed in a situation where the SMD
10
is not being mounted to a substrate
18
having conductive pads
20
that correspond to the electrodes
14
on the contact surface
16
of such SMD
10
, and also in other similar situations.
SUMMARY OF THE INVENTION
In the present invention, the aforementioned need is satisfied by a surface mount device (SMD) having a plurality of electrodes and a generally planar contact surface for facing and at least partially contacting a substrate such as a conductive shield. At least one electrode is present at the contact surface and electrically contacts the substrate. In several embodiments of the present invention, at least one electrode is absent from the contact surface and does not electrically contact the substrate. In these embodiments of the present invention, the shield is part of an electrical device which has a lead electrically coupled to the at least one electrode absent from the contact surface. In another embodiment, the SMD includes all electrodes and is mounted to a split conductive shield.


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