Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2003-03-28
2004-08-24
Arbes, Carl J. (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S827000, C029S832000, C029S840000, C174S050510, C174S050510
Reexamination Certificate
active
06779260
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to techniques for packaging electronic circuitry, and more specifically to techniques for packaging circuit-carrying substrates interconnected to one or more connector pins of a connector housing or shroud.
BACKGROUND OF THE INVENTION
Circuit-carrying substrates typically require protection from the environment and an electrical interface to external components and/or systems. In an effort to achieve and also to improve on these two goals, a number of electronic packaging techniques have been implemented.
FIG. 1
illustrates a cross-section of one example of a popular conventional electronic package
10
having a circuit-carrying substrate
24
mounted therein and operatively connected to a number of electrical connector pins
20
. Package
10
includes a housing
14
, typically formed of a plastic resin, affixed to a substrate
12
, typically formed of metal, via an adhesive layer
16
. The housing
14
defines a connector shroud cavity
18
housing one or more electrical connector pins
20
, and the one or more pins
20
extend into a cavity
22
defined by the housing
14
. A circuit-carrying substrate
24
, typically formed of a ceramic material such as alumina, is affixed to the backplate
12
within the cavity
22
via an appropriate adhesive or epoxy
26
, which is typically thermally conductive to provide an adequate heat sink between the substrate
24
and backplate
12
. Alternatively, layer
26
may represent a solder connection between the substrate
24
and backplate
12
.
The substrate
24
may carry a number of electrical components, and two such components
28
and
30
are illustrated in FIG.
1
. Component
28
represents a printed resistor and component
30
represents an integrated circuit mounted to substrate
24
using conventional flip chip technology; i.e., conductive “bumps” are formed on the bond pads of the integrated circuit
30
, and the circuit
30
is then mounted to the substrate
24
with its circuit-defining surface facing substrate
30
such that the bumps align with and contact electrically conductive circuit pads or leads defined on the substrate
24
. The bumps are thereafter bonded to the circuit pads or leads in a known manner to mechanically and electrically connect the integrated circuit
30
to the substrate
24
. Because the mechanical connection between the integrated circuit
30
and the substrate
24
is made only via the bonds between the bumps and the circuit pads or leads, the gap between the integrated circuit
30
and substrate
24
is typically filled with a conventional formable underfill medium
36
that bonds to the circuit-carrying surface of the integrated circuit
30
and to the substrate
24
to thereby secure the mechanical connection therebetween. The underfill process, conventionally carried out via a known capillary underfill technique, is typically carried out before the substrate
24
is mounted to the backplate
12
.
The substrate defines thereon a number of bonding locations
32
, and wirebonds
34
, typically formed of aluminum, are attached between the various bonding locations
32
and corresponding ones of the electrical connector pins
20
extending through the housing
14
into the cavity
22
. The cavity
22
is typically filled with a circuit-protecting, pliable, gel-like medium or circuit passivation material
38
, and a cap or cover
40
is then mounted to the housing
14
via a suitable adhesive
42
. A vent hole
44
is typically provided through the cap
40
to allow for outgassing of one or more of the materials housed within the cavity
22
.
Referring to
FIG. 2
, a flowchart is shown illustrating a typical process
50
for constructing the electronic package
10
of
FIG. 1
, and process
50
begins at step
52
where any flip-chip mounted integrated circuits
30
carried by the substrate
24
are underfilled as described to secure mechanical connection therebetween. At step
54
, the backplate
12
is attached to the housing
14
via adhesive layer
16
, and thereafter at step
56
the circuit-carrying substrate
24
is attached to the backplate
12
within the housing cavity
22
via adhesive layer
26
. Following step
56
, the housing leads or pins
20
are wirebonded to the bonding locations
32
on the substrate
24
at step
58
, and thereafter at step
60
the housing cavity
22
is filled with the circuit passivation material
38
and the cover or cap
40
is then mounted to the housing
14
at step
62
via adhesive layer
42
.
The electronic package
50
illustrated in FIG.
1
and described hereinabove utilizes complex housing and interconnect designs, and the process of constructing package
50
involves multiple adhesive and formable medium dispense and cure operations. It is accordingly desirable to simplify the package structure and associated manufacturing processes to decrease the cost and complexity, and also to eliminate shortcomings, associated with conventional electronic packages and interconnect configurations.
SUMMARY OF THE INVENTION
The present invention comprises one or more of the following features or combinations thereof. A method of forming an overmolded electronic package including a circuit-carrying substrate may comprise the steps of providing a housing defining a cavity therein and defining a connector shroud having a number of electrically conductive leads extending into the cavity, attaching the housing to a backplate, attaching the circuit-carrying substrate to the backplate within the housing cavity, connecting the number of electrically conductive leads to corresponding conductive pads defined on the substrate, filling the cavity with a rigidly formable molding compound and curing the formable molding compound. The connecting step may comprise wirebonding the number of electrically conductive leads to the corresponding conductive pads defined on the substrate to rigidly bond together the backplate, substrate and the housing to form the overmolded electronic package.
The method may further include the step of applying an adhesion promoting layer to a circuit-carrying side of the substrate prior to the filling step, wherein the adhesion promoting layer promotes adhesion between the circuit-carrying side of the substrate and the formable molding compound.
The circuit-carrying side of the substrate may have at least one flip chip mounted thereto with the at least one flip chip and the substrate defining a space therebetween, and the formable molding compound may be configured to flow between the at least one flip chip and the substrate and fill the space prior to the curing step.
The formable molding compound may be configured to exhibit a coefficient of thermal expansion that is near that of the substrate.
Another method of forming an overmolded electronic package including a circuit-carrying substrate may comprise the steps of providing a connector shroud having a number of electrically conductive leads extending therethrough, attaching the connector shroud to one of a backplate and the circuit-carrying substrate, attaching the circuit-carrying substrate to the backplate, connecting the number of electrically conductive leads to corresponding conductive pads defined on the substrate, and overmolding at least the connector shroud and the circuit-carrying substrate with a rigidly formable molding compound to form the overmolded electronic package. The step of attaching the connector shroud may comprise attaching the connector shroud only to the backplate, wherein the overmolding step includes overmolding the connector shroud, the circuit-carrying substrate and the backplate with the rigidly formable molding compound to form the overmolded electronic package. Alternatively, the step of attaching the connector shroud may comprise attaching the connector shroud only to the circuit-carrying substrate, wherein the overmolding step includes overmolding the connector shroud, the circuit-carrying substrate and the backplate with the rigidly formable molding compound to form the overmolded electronic package.
Brandenburg Scott D.
Degenkolb Thomas A.
Myers Bruce A.
Arbes Carl J.
Chmielewski Stefan V.
Delphi Technologies Inc.
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