Electricity: conductors and insulators – Boxes and housings – Hermetic sealed envelope type
Reexamination Certificate
2000-08-17
2003-03-18
Reichard, Dean A. (Department: 2831)
Electricity: conductors and insulators
Boxes and housings
Hermetic sealed envelope type
C264S272110, C257S687000, C257S787000
Reexamination Certificate
active
06534711
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The invention relates to the interconnection and packaging of electronic components and, more particularly, to a circuit module which may include a sensor and be disposed in a harsh environment.
BACKGROUND OF THE INVENTION
As used herein, the term “circuit module” refers to an interconnection substrate such as a printed circuit board (PCB) having electronic components mounted thereto. A PCB is a multi-layer substrate, having alternate layers of insulating material and conductive material. The conductive material of a conductive layer is patterned to have conductive “lines” or “traces” for routing signals (and power) from one location on the PCB to another location on the PCB. In the case of multiple conductive layers, typically at least one of these layers is disposed on a surface (e.g., the “top” surface) of the PCB. Additionally, the conductive layer on the top surface of the PCB may be patterned to have “pads” which serve as terminals for (i) connecting to leads of electronic components mounted to the PCB, or (ii) making connections to external instrumentalities such as sockets. In this manner, electronic components which are mounted to the PCB may be interconnected to one another via pads on the top surface of the PCB and conductive traces of the PCB.
Examples of electronic components which may be incorporated in a circuit module include:
(a) “active” electronic components such as integrated circuit (IC) devices, and the like;
(b) “passive” electronic components such as resistors, capacitors, and inductors (including transformers), and the like;
(c) switches, relays and the like; and
(d) sensors, transducers and the like.
The electronic components incorporated in a circuit module may either be “packaged” or “bare” (not packaged).
An example of a “packaged electronic component” is a semiconductor memory device (e.g., dynamic random access memory, or DRAM, chip) which has been mounted and electrically connected to a leadframe having a plurality of elongate conductive members (“fingers”) and overmolded with plastic. Outer portions of the leadframe fingers extend (protrude) out of the molded plastic body and can be connected to the conductive pads on an interconnection substrate (PCB). In this manner, a plurality of plastic-packaged DRAM memory devices can be mounted and connected to a PCB, thereby forming a memory module. The memory module can be plugged into a socket which is mounted on another interconnection substrate, such as a “motherboard” of a computer system, with conductive pads disposed on one or both surfaces of the memory module making electrical contact with resilient contact members in the socket.
An example of a “bare electronic component” is a semiconductor device which is glued (using “die attach” adhesive) onto an interconnection substrate and electrically connected thereto with fine wires extending between pads on the semiconductor device and pads on the interconnection substrate. In order to protect the electronic component and the wires, it is known to apply a dollop of “glob-top” epoxy, or the like, over the electronic component and the fine wires.
A well-known technique for making such connections to semiconductor devices is “wirebonding”. An exemplary wirebonding technique involves:
a. feeding a fine (e.g., 1 mil diameter) gold (or gold alloy) bond wire through a capillary which is located above a terminal (pad) of an interconnection substrate or electronic component mounted thereto;
b. bonding (e.g., welding) an end of the bond wire to the terminal using a combination of pressure and heat or ultrasonic vibration;
c. withdrawing the capillary so that the bond wire “pays out” of the capillary, thereby forming some slack in the bond wire;
d. moving the interconnection substrate (or, conversely, the capillary), so that the capillary is located above another terminal (pad) on the electronic component or interconnection substrate;
e. bonding an intermediate portion of the bond wire to the other terminal; and
f. severing the bond wire, thereby resulting in a “loop” of bond wire extending between the terminal (pad) on the electronic component and the terminal (pad) on the interconnection substrate.
The present invention draws upon many of the techniques described hereinabove to effect a novel technique for packaging electronic circuit modules and components. Prior to proceeding with a description of the invention, certain additional relevant aspects of electronic packaging should be understood.
There is often a need to test or, more broadly, exercise electronic components and circuit modules prior to their being shipped for installation (e.g., assembly into systems) to ensure that they will perform to their design specification. This would include, in the case of electronic components and circuit modules that can and need to be calibrated or personalized, calibrating or personalizing the electronic components and circuit modules.
Returning to the example of a DRAM device which has been overmolded with plastic and which has outer portions of leadframe fingers protruding out of the molded plastic body, the DRAM device can be tested by making “temporary” electrical connections to portions of the leadframe fingers which protrude from the package body, using pins, needles and the like. An example of a pin suitable for making a temporary electrical connection to a terminal (in this example, the terminal being the protruding portion of the leadframe finger) of an electronic component is a so-called “pogo” pin, which is generally a pin having an inner part protruding from an outer part, and a spring maintaining the inner part biased to an extended position. Or, in the case of a memory module having a plurality of plastic-packaged DRAM memory devices mounted and connected to a PCB, the entire module can be tested by plugging the module into a test socket of a test system, the test socket making temporary electrical connections to the PCB and “accessing” the components mounted to the PCB via the conductive traces of the PCB.
Personalizing or calibrating a packaged circuit module similarly involves, in a broad sense, having access to protruding terminals of the module. For example, the module may have a non-volatile memory (NVM) component which can be programmed by providing signals to external terminals of the module. Or, for example, a module can be programmed via personalization components such as DIP-switches which are part of the module and accessible from external the module.
In contrast thereto, consider the case of a packaged circuit module which in its final form does not have any terminals protruding from its exterior or access to personalization components from its exterior—not even power connections (e.g., battery terminals). The problem is, how to exercise the module. An example of such a packaged circuit module lacking the inherent ability of be exercised or personalized in its final form is a transponder module that is fully encased to isolate its electronic components from the ambient environment, save for a sensor (e.g., a temperature sensor) that is exposed to the ambient environment on the exterior of the packaged circuit module.
As will become evident, the present invention is directed to a package for encapsulating electronic modules and components having at least two chambers (cavities).
European Patent No. EP-A-0289439 discloses a single chamber of an enclosure which is partially filled over a first circuit module, thereby encapsulating a “first chamber,” and leaving the unfilled remainder of the chamber as a “second chamber.” A second circuit module is placed on top of the first filling, and then the second chamber is filled with a second filling which covers the second circuit module. Appropriate interconnections between circuit modules and external connectors are made by conductors embedded in the first and second fillings, and thereby passing between chambers.
U.S. Pat. No. 5,239,126 (Sony, 1993) discloses a high-frequency circuit package including a conductive substrate, and upper and lower shielding cases wh
Cohn Howard M.
Oliva Carmelo
Reichard Dean A.
The Goodyear Tire & Rubber Company
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