Image sensor having shortened wires

Details Image sensor having shortened wires Image sensor having shortened wires

2003-01-09

2004-06-08

Pyo, Kevin (Department: 2878)

Radiant energy

Photocells; circuits and apparatus

Photocell controlled circuit

C250S239000, C257S692000

Reexamination Certificate

active

06747261

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an image sensor, and in particular to a package structure of an image sensor having shortened wires.
2. Description of the Related Art
Referring to
FIG. 1
, a conventional image sensor includes a substrate
10
, a frame layer
18
, a photosensitive chip
26
, a plurality of wires
28
, and a transparent layer
34
. The substrate
10
has a first surface
12
on which signal input terminals
15
are formed, and a second surface
14
on which signal output terminals
16
are formed. The frame layer
18
has an upper surface
20
and a lower surface
22
adhered to the first surface
12
of the lower surface
22
to form a cavity
24
together with the substrate
10
. The photosensitive chip
26
is placed within the cavity
24
formed by the substrate
10
and the frame layer
18
and is mounted to the first surface
12
of the substrate
10
. Each of the wires
28
has a first terminal
30
electrically connected to the photosensitive chip
26
, and a second terminal
32
electrically connected to a corresponding signal input terminal
15
of the substrate
10
. The transparent layer
34
is placed on the upper surface
20
of the frame layer
18
.
According to the above-mentioned wire bonding structure, the lengths of the wires
28
from the bonding pads of the photosensitive chip
26
to the signal input terminals
15
of the substrate
10
are quite long. Therefore, the signal transmission speed is slow and the image sensor is impractical.
Referring to
FIG. 2
, which is a cross-sectional view showing an image sensor disclosed in a U.S. patent application Ser. No. 10/146,997, filed on May 15, 2002. The lengths of the wires
88
are also long, and the signal transmission speed of the image sensor is slow and the signal transmission efficiency thereof is also low.
SUMMARY OF THE INVENTION
An object of the invention is to provide a practical image sensor with shortened wires so as to enhance the signal transmission efficiency.
To achieve the above-mentioned object, the invention provides an image sensor having shortened wires. The image sensor includes a substrate composed of a plurality of metal sheets arranged in a matrix, a photosensitive chip, a plurality of bonding pads, a frame layer, a plurality of wires and a transparent layer. Each of the metal sheets has a first board and a second board located at a height different from that of the first board. A chamber is defined under a bottom surface of the substrate. The photosensitive chip is arranged within the chamber. The bonding pads are formed on the photosensitive chip at positions corresponding to the first boards of the substrate. The bonding pads and the first boards of the substrate are staggered so that each of the bonding pads is arranged between adjacent two of the first boards. The frame layer is formed on a periphery and the bottom surface of the substrate to encapsulate the photosensitive chip. Upper faces of the first boards and bottom faces of the second boards are exposed out of the frame layer, and the bottom faces of the second boards are electrically connected to the printed circuit board. Each of the wires has a first terminal and a second terminal. The first terminals are electrically connected to the bonding-pads of the photosensitive chip, respectively, and the second terminals are electrically connected to the corresponding staggered first boards of the substrate, respectively. The transparent layer is placed on the frame layer to cover the photosensitive chip so that the photosensitive chip may receive optical signals passing through the transparent layer.
Accordingly, the signal transmission distance can be shortened, and the signal transmission speed may be increased.


REFERENCES:
patent: 3622419 (1971-11-01), London et al.
patent: 5122861 (1992-06-01), Tamura et al.
patent: 6649834 (2003-11-01), Hsieh et al.

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