Over-current protection device

Details Over-current protection device Over-current protection device

2003-07-08

2004-10-26

Vortman, Anatoly (Department: 2835)

Electricity: electrothermally or thermally actuated switches

Electrothermally actuated switches

Fusible element actuated

C337S297000, C361S106000, C338S0220SD, C338S328000

Reexamination Certificate

active

06809626

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an over-current protection device, and more particularly, to an over-current protection device that can provide a uniform and stable conductive strength and reliability.
2. Description of Related Art
As portable electronic devices such as mobile phone, laptop computer, portable video camera and personal digital assistant, etc., are widely used, the importance of the over-current protection device, used to prevent electronic devices from the occurrence of over-current or over-temperature, is increased. Since the positive temperature coefficient (PTC) over-current protection device possesses advantages of reusability being sensitive to temperature variation and, high reliability etc., it is very commonly and widely used in high-density circuit boards and the above-mentioned portable electronic devices.
The PTC over-current protection device uses a positive temperature coefficient conductive material as a current sensor. The resistance of the PTC conductive material is very sensitive to temperature variation, which can be kept extremely low at normal operation so that the circuit can operate normally. However, if an over-current or an over-temperature event occurs, the resistance will simultaneously be increased to a very high resistance state (e.g. above 10,000 ohm.) Therefore, the over-current will be reversely eliminated and the objective to protect the circuit device can be achieved.
FIG. 1
is a schematic diagram of a PTC laminate
10
according to the prior art. The detailed inner structure of the PTC laminate
10
is available in U.S. Pat. No. 6,377,467, entitled “SURFACE MOUNTABLE OVER-CURRENT PROTECTING DEVICE.” From the side view, the PTC laminate
10
comprises a PTC material layer
11
, an upper electrode foil
13
and a lower electrode foil
14
covering the PTC material layer
11
, a first metal layer
15
electrically connecting the upper electrode foil
13
, a second metal layer
16
electrically connecting the lower electrode foil
14
, a solder mask
18
disposed between the first metal layer
15
and the second metal layer
16
, and an insulating layer
17
isolating the upper electrode foil
13
from the second metallic layer
16
and the lower electrode foil
14
from the first metallic layer
15
. From the top view, the PTC laminate
10
comprises a plurality of conductive through holes
12
and each conductive through hole
12
is electroplated with conductive material inside. A cutter is used to cut off the conductive through hole
12
along the center to form a half-circular conductive through hole
21
, and an packaging process is performed to complete the over-current protection device
20
, as shown in FIG.
2
.
As the size of the electronic devices shrinks, the size of the traditional over-current protection device also shrinks from 1812 (length×width) and 1210 (length×width) to 1206 and 0805, and even to 0603 and 0402. As the size of the traditional over-current protection device is smaller than 0603, the thickness of the cutter is approximately the same as the diameter of the conductive through hole
12
. In this condition, an error on cutting the conductive through hole
12
generally forms an over-current protection device that has a conductive through hole with smaller surface. This will decrease the solderability of the over-current protection device
20
for surface mounting onto a circuit board. Moreover, the material tension and extensibility of the PTC material layer
11
are both larger than those of the metal material under the high voltage condition, which influences the reliability of the PTC over-current protection device
20
on the conductive through holes.
Since the conventional over-current protection device
20
possesses the above-mentioned defects, it is necessary to provide an effective solution for these defects.
BRIEF DESCRIPTION OF THE INVENTION
The objective of the present invention is to provide an over-current protection device, which can enhance the conductive strength and the reliability.
To this end and to avoid the defects in the prior art, the present invention discloses an over-current protection device, which comprises a positive temperature coefficient material layer, an upper electrode foil, a lower electrode foil, a first metal terminal layer, a second metal terminal layer, and at least one insulating layer. The upper electrode foil is disposed on the upper surface of the positive temperature coefficient material layer, and the lower electrode foil is disposed on the lower surface of the positive temperature coefficient material layer. The first metal terminal layer electrically connects the upper electrode foil with at least one non-full-circular conductive through hole and at least one full-circular conductive through hole, and the second metal terminal layer electrically connects the lower electrode foil with at least one non-full-circular conductive through hole and at least one full-circular conductive through hole. The insulating layer isolates the upper electrode foil from the second metal terminal layer and the lower electrode foil from the first metal terminal layer.
The present invention further discloses an over-current protection device, comprising at least two over-current protection modules, a first metal terminal layer, a second metal terminal layer, and at least one first insulating layer. The at least two over-current protection modules are stacked vertically and are electrically connected in parallel, comprise a positive temperature coefficient material layer, an upper electrode foil and a lower electrode foil. The first metal terminal layer electrically connects the upper electrode foil of the at least two over-current protection modules with at least one non-full-circular conductive through hole and at least one full-circular conductive through hole. The second metal terminal layer electrically connects the lower electrode foil of the at least two over-current protection modules with at least one non-full-circular conductive through hole and at least one full-circular conductive through hole. The insulating layer isolates the second metal terminal layer from the upper electrode foil of the uppermost over-current protection module, the first metal terminal layer from the lower electrode foil of the lowest over-current protection module, and the adjacent over-current protection modules from each other.


REFERENCES:
patent: 5852397 (1998-12-01), Chan et al.
patent: 6377467 (2002-04-01), Chu et al.
patent: 6392528 (2002-05-01), Myong
patent: 6576492 (2003-06-01), Chen et al.
patent: 6593843 (2003-07-01), Becker et al.
patent: 6606023 (2003-08-01), Chiang et al.
patent: 6628498 (2003-09-01), Whitney et al.
patent: 6640420 (2003-11-01), Hetherton et al.
patent: 6665164 (2003-12-01), Chu et al.
patent: 6686827 (2004-02-01), Chen et al.
patent: 2000188207 (2000-07-01), None

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