Active solid-state devices (e.g. – transistors – solid-state diode – Encapsulated
Reexamination Certificate
2003-05-21
2004-07-06
Clark, Jasmine (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Encapsulated
C257S666000, C257S723000, C257S781000, C257S784000
Reexamination Certificate
active
06759753
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to a multi-chip package and, in particular, to a multi-chip package having a transparent substrate.
2. Related Art
As an electrical system increases its functionality and at the same time becomes more compact, conventional IC package and PCB (printed circuit board) assembling technologies are no longer able to satisfy the need for reducing the system size. As a result, an obvious trend is to integrate multiple complex functions in a single IC chip.
Conventional IC fabrication technology, however, utilizes variant sets of processes to fabricate IC chips having different functions. For example, processes for a logic IC are very different from those for a memory IC. Therefore, it is difficult to integrate a logic IC and a memory IC in one single IC chip, and still maintain adequate performance. Consequently, a new technique for packaging different chips into a single package known to those skilled in the art as a multi-chip package (MCP) is disclosed.
As multi-chip package technology develops, the IC chips in a single package can perform powerful functions, such that they can already be considered as a system. Such a package having multiple chips with a system level function is known as a system in package (SIP).
Presently, there are a variety of multi-chip package types, and different manufacturing methods thereof. Two types of multi-chip packages will be described hereinbelow to illustrate the structures and disadvantages thereof.
In the first case, a multi-chip package employing a lead frame to carry IC chips is described. With reference to
FIG. 1
, a conventional multi-chip package
1
includes a lead frame
11
, at least two IC chips
13
, a plurality of wires
15
, and a molding compound
17
. Each IC chip
13
is attached to the lead frame
11
. The wires
15
respectively bond the IC chips
13
to leads or fingers of the lead frame
11
. The molding compound
17
encapsulates the lead frame
11
, IC chips
13
and wires
15
. In the multi-chip package
1
, each IC chip
13
is interconnected to the leads or fingers of the lead frame
15
. In more detail, the wires
15
bond each IC chip
13
to the lead frame
11
, so that the IC chips
13
can interconnect to each other via the leads or fingers of the lead frame
11
. People skilled in the art should know that processes for manufacturing the multi-chip package
1
are similar to processes for manufacturing a conventional single-chip package. The lead frame
11
, however, has limitation due to the conventional manufacturing technology, and it is difficult to manufacture a lead frame having fine pattern. Therefore, the lead frame is poorly suited for high pin-count chips. Moreover, since the lead frame
11
is a single layer structure, the leads or fingers of the lead frame
11
cannot cross over each other. As a result, the complexity and flexibility of the layout that the leads or the fingers can provide is restricted. To solve the previously mentioned problem, additional wires can be used to bond one lead or finger to another for connecting the leads or fingers as desired. However, this may make manufacturing processes more complex, and the size of the multi-chip package
1
may be further enlarged.
In the second case, another multi-chip package employing a BGA (Ball Grid Array) substrate to carry IC chips is described. With reference to
FIG. 2
, an additional multi-chip package
2
includes a BGA substrate
21
, at least two IC chips
23
, a plurality of wires
25
, and a molding compound
27
. The BGA substrate
21
is composed of a usual resin material. A plurality of fingers and trace lines are formed on the upper surface of the BGA substrate
21
, and a plurality of solder balls
211
are formed on the bottom of the BGA substrate
21
. Each IC chip
23
is mounted on the upper surface of the BGA substrate
21
. The wires
25
bond the IC chips
23
to the fingers of the BGA substrate
21
, respectively. The molding compound
27
encapsulates the BGA substrate
21
, IC chips
23
, and wires
25
. In the multi-chip package
2
, the IC chips
23
are interconnected to each other through the fingers and trace lines of the BGA substrate
21
. In more detail, the wires
25
bond each IC chip
23
to the fingers of the BGA substrate
21
, so that the IC chips
23
can interconnect to each other via the trace lines, which connect to the fingers. Each IC chip
23
can then electrically connect to external devices through the fingers, trace lines, and solder balls. People skilled in the art should know that the BGA substrate
21
has a plurality of conductive layers for forming the trace lines, so that a complex circuitry and the fine pattern can be provided between the IC chips. Furthermore, the IC chips
23
can be attached to the BGA substrate
21
by way of a flip-chip attachment (not shown). Thus, the wires
25
can be eliminated. In such a case, the manufacturing process of the multi-chip package
2
is simplified, and the size of the multi-chip package
2
is efficiently controlled. However, the BGA substrate has a higher production cost. In addition, the BGA substrate
21
composed of resin material has a thermal expansion coefficient higher than that of each IC chip
23
, which is made of silicon. Thus, when the IC chips
23
are attached to the BGA substrate
21
by way of a flip-chip attachment, the reliability of the multi-chip package
2
may be degraded accordingly.
Moreover, since the insulating property of the BGA substrate
21
is limited, high frequency signals transmitted in the fingers and trace lines may decay easily due to parasitic capacitance and parasitic leakage resistance.
In summary, since the conventional multi-chip package usually employs a lead frame or a BGA substrate to carry IC chips and provide circuits for connecting each IC chip, the conventional multi-chip package does not provide fine pattern (as in the case of the lead frame), or requires a higher production cost (as in the case of the BGA substrate). In addition, the conventional multi-chip package, especially for the case of using the BGA technology, still has the problems of high-frequency signal decay and degraded reliability. Thus, it is an important objective of the invention to solve the previously mentioned problems when employing the lead frame or BGA substrate.
SUMMARY OF THE INVENTION
In view of the above-mentioned problems, an objective of the invention is to provide a multi-chip package, which has a circuit of fine pattern.
It is another objective of the invention to provide a multi-chip package, which efficiently reduces high frequency signal decay caused by parasitic capacitance and parasitic leakage resistance.
It is a further objective of the invention to provide a multi-chip package, which prevents degraded reliability due to the difference between the thermal expansion coefficients of the materials inside the multi-chip package.
To achieve the above-mentioned objectives, a multi-chip package includes a transparent substrate, at least two chips, a plurality of connecting terminals, and a molding compound. In the invention, the transparent substrate has a conductive layer for electrical inter-connection. The chips are mounted on the transparent substrate, wherein at least one of the chips is provided on the transparent substrate by way of a flip-chip attachment. The chips and the conductive layer form a circuitry system. The connecting terminals electrically connect to the circuitry system through a plurality of wires, so that the circuitry system can electrically connect to external devices through the wires and connecting terminals. The molding compound at least encapsulates the wires.
Since the multi-chip package of the invention employs the transparent substrate, such as a glass substrate, to carry the chips, the conductive layer with fine pattern can be formed on the transparent substrate by utilizing existing manufacturing technology. Moreover, the transparent substrate, especially the glass substrate, has a good insulation property and a
Birch & Stewart Kolasch & Birch, LLP
Clark Jasmine
Gigno Technology Co., Ltd.
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