Mutli-chip module

Details Mutli-chip module Mutli-chip module

2002-12-17

2004-12-21

Nelms, David (Department: 2818)

Active solid-state devices (e.g., transistors, solid-state diode

Combined with electrical contact or lead

Flip chip

C257S778000, C257S723000

Reexamination Certificate

active

06833628

ABSTRACT:

CROSS REFERENCE TO RELATED APPLICATIONS
Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
Not applicable.
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention generally relates to circuit device packages. More particularly, this invention relates to a multi-chip module (MCM) and method adapted to permit both underfilling and overmolding of surface-mounted devices on opposite surfaces of a laminate substrate within the MCM.
(2) Description of the Related Art
A flip chip is generally a surface-mounted (SM) device in the form of a monolithic semiconductor chip, such as an integrated circuit (IC) chip, having bead-like solder terminals formed on one of its surfaces. The terminals, also referred to as solder bumps, serve to both secure the chip to a circuit board and electrically interconnect the flip chip circuitry to a conductor pattern formed on the circuit board, which may be a ceramic substrate, printed circuit board (PCB), printed wiring board (PWB), flexible circuit, or a silicon substrate.
While typically mounted directly to a substrate, flip chips have been incorporated into packages, an example of which is ball grid array (BGA) packages. An example of a BGA package
110
is shown in
FIG. 1
as including an IC semiconductor chip
112
that is wire bonded to a substrate
114
, e.g., a laminate PCB, with wires
116
. The wires
116
are electrically connected through vias (not shown) in the substrate
114
to terminals
118
on the opposite surface of the substrate
114
. Similar to the flip-chip process, the terminals
118
serve as interconnects between the chip
112
and a conductor pattern on a circuit board (not shown) to which the BGA package
110
will be mounted.
FIG. 2
is an example of the use of a flip chip
122
in a BGA package
120
to form a single-chip module. The flip chip
122
is equipped with solder bumps that form solder joint connections
126
when the chip
122
is flip-chip mounted to a conductor pattern on a substrate
124
, e.g., a high-density PCB, which can then be mounted to a circuit (mother) board (not shown) with terminals
128
on the lower surface of the substrate
124
. In the case where the substrate
124
is a PCB, it is desirable to underfill the flip chip
122
with a filled epoxy
130
to ensure the reliability of the solder joint connections
126
. Finally,
FIG. 2
shows the interior of the BGA package
120
comprising a molding compound
132
that overmolds the chip
122
.
While the packaging technique of
FIG. 2
capitalizes on the processing and assembly advantages provided by flip chips and BGA's, further improvements in packaging processes and density are continuously sought. For example, the underfilling process is both cumbersome and expensive, and becomes more difficult as the number of flip-chips mounted to a substrate increases, especially if the chips are to be mounted to both surfaces of the substrate.
BRIEF SUMMARY OF THE INVENTION
The present invention provides a package and packaging method that incorporate multiple surface-mounted devices, such as flip chips, mounted to a chip carrier, which in turn can be mounted onto a circuit board. The package is configured to provide a cost-effective, high-density multi-chip module that is also configured to facilitate underfilling and/or overmolding of circuit devices mounted on both sides of the chip carrier.
The package of this invention generally includes a pair of laminate substrates that together form a chip carrier and input/output (I/O) interface structure for a number of chips, e.g., flip chips, wire-bonded chips and/or other surface-mount components. A first of the laminate substrates has a first conductor pattern on a first surface thereof and a second conductor pattern on an oppositely-disposed second surface thereof. The second laminate substrate is attached to the first laminate substrate, and has an interior opening therethrough that is surrounded by a frame portion. The frame portion has a first surface facing the first laminate substrate and an oppositely-disposed second surface on which solder terminals are present. One or more surface-mounted devices are mounted to each of the first and second surfaces of the first laminate substrate. The first and second laminate substrates are attached to each other such that the surface-mounted device mounted to the second surface of the first laminate substrate is disposed within the interior opening of the second laminate substrate.
In view of the above, the present invention provides a process for forming an MCM package in which one or more surface-mounted devices are located within a cavity defined by the interior opening in the second laminate substrate. The second laminate substrate is preferably configured with lateral openings, preferably located in its first surface and therefore between the first and second laminate substrates. Through one of these lateral openings, a molding compound can be injected into the cavity defined by the interior opening in the second laminate substrate, with the result that the device mounted to the second surface of the first laminate substrate can be simultaneously underfilled and overmolded. As such, the present invention provides a dual-sided MCM package that can be equipped with flip chips on opposite surfaces of a laminate substrate. Advantages include a relatively lowcost, electrically testable package whose surface-mounted devices can readily be both underfilled and overmolded to promote the reliability of the package.
Other objects and advantages of this invention will be better appreciated from the following detailed description.


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European Search Report Mar. 3, 2004.

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