Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
1999-07-09
2002-06-18
Picard, Leo P. (Department: 2841)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S780000, C361S777000, C361S794000, C361S803000, C174S255000, C174S261000, C174S263000, C439S069000, C439S074000
Reexamination Certificate
active
06407930
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims the priority benefit of Taiwan application serial no. 88110533, filed Jun. 23, 1999, the full disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a structure of a printed circuit board. More particularly, the present invention relates to a structure of a printed circuit board with a stacked daughter board.
2. Description of Related Art
After devices are packaged, the devices are mounted on a substrate such as a printed circuit board for coupling with other devices; the most common application is a mainboard or motherboard.
FIG. 1
is a schematic diagram of a conventional mainboard.
Referring to
FIG. 1
, devices such as a microprocessor
12
, a chip
14
and a slot
16
are mounted on a mainboard
10
that is usually a four-layer printed circuit board. The microprocessor
12
is used to run programs and the chip
14
is a communication bridge between the microprocessor
12
and the slot
16
or the microprocessor
12
and other devices. The slot
16
is for an expansion card such as a network card or a sound card. The devices are coupled with each other by traces
18
for transmitting data.
Since the amount of data transmitted between each device is different, the number of traces
18
between any two devices is also different. This means that the distribution of the trace density on the mainboard
10
is not even. For example, the trace density of trace region
20
between the microprocessor
12
and the chip
14
is high, because most data are transmitted between the microprocessor
12
and the chip
14
. In contrast, the trace density in trace region
22
between the chip
14
and the slot
16
is low, because fewer data are transmitted between the chip
14
and the slot
16
.
With the increasing power of the microprocessor and the increasing number of devices, the number of traces on the mainboard must increase to deal with more data transmitted between devices. This means that the distribution of the trace density on the mainboard becomes worse; the high trace density region becomes denser. However, the area of the mainboard for forming the traces is fixed, therefore the trace density is limited. When the trace density exceeds the limit, the layout of the traces cannot be formed on the general four-layer printed circuit board, and a printed circuit board having more layers is needed. However, dense traces are only formed in some regions and the cost of the printed circuit board having more layers is high, so the cost of achieving the high density trace layout is increased by using a printed circuit board having more layers.
SUMMARY OF THE INVENTION
The invention provides a structure of a printed circuit board with stacked daughter board. The structure of the printed circuit board is a daughter board stacked on a high trace density region of a mainboard or motherboard, so that a high-density trace layout is achieved. Additionally, by using the daughter board, the trace layout is flexible because a bridge circuit is formed by the daughter board, so that circuits on the motherboard can be changed by changing the daughter board. Moreover, design of the printed circuit board is modularized by using the daughter board.
As embodied and broadly described herein, the invention provides a structure of a printed circuit board with stacked daughter board. The structure includes a motherboard and at least a daughter board. The motherboard comprises two signal layers plus a power layer, and a ground layer. Isolation layers separate each of the layers. The signal layers serve as surfaces of the motherboard and contacts are formed on one of the signal layers. The daughter board also comprises two signal layers plus a power layer, and a ground layer. Isolation layers separate each of the layers. The power layer or the ground layer serves as a surface of the daughter board and contacts are formed on the surface. The surface of the daughter board formed by the ground layer or the power layer is stacked on the motherboard and the daughter board contacts are coupled with the motherboard contacts.
In another embodiment grooves are formed on opposite sides of the daughter board. The inner surface of each groove and a region around each groove are covered with a conductive layer. The surface of the daughter board formed by the ground layer or the power layer is stacked on the motherboard. The grooves on the daughter board are coupled with the contacts on the motherboard.
The daughter board is stacked on the motherboard so the high-density trace layout can be achieved for the motherboard. Furthermore, the design of the printed circuit board assembly made from the motherboard and the daughter board becomes flexible and modularized because the function of the printed circuit board is easily changed by changing the daughter board.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.
REFERENCES:
patent: 4803450 (1989-02-01), Burgess et al.
patent: 5097390 (1992-03-01), Gerrie et al.
patent: 5434745 (1995-07-01), Shokrgozar et al.
patent: 5657208 (1997-08-01), Noe et al.
patent: 5719750 (1998-02-01), Iwane
patent: 5729440 (1998-03-01), Jimarez et al.
patent: 5926377 (1999-07-01), Nakao et al.
patent: 6094354 (2000-07-01), Nakajoh et al.
patent: 6121554 (2000-09-01), Kamikawa
ASUSTek Computer Inc.
Foster David
Picard Leo P.
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