Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
2000-11-09
2002-03-26
Tolin, Gerald (Department: 2835)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C257S724000, C361S719000
Reexamination Certificate
active
06362964
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device module and, more specifically, relates to a novel module employing an insulated metal substrate (IMS), one or more power circuit boards, interconnects and other components that are arranged in a novel manner.
Known semiconductor device modules are used for housing a plurality of interconnected semiconductor chips. The chips may be of the same or of diverse kind and may be mounted on a heatsink or other substrate within a common housing having terminal electrodes which extend from the housing.
In a power application, such as for a motor control circuit or similar functions, both high power devices, from which heat must be removed, as well as low power devices, which do not require heatsinking, are employed. Typically, the heatsinking may be provided by mounting the devices on an IMS which is enclosed in a module housing. Such substrates and modules are described in U.S. Pat. No. 5,408,128, issued Apr. 18, 1995 in the name of the inventor of the present application and assigned to International Rectifier Corporation, the present assignee. However, when both high power and low power devices are required for an application, the inclusion of low power devices on an IMS greatly increases the cost of the module. Alternatively, the high power devices are included within the IMS module and the low power devices are mounted externally in other modules, thus greatly increasing the footprint of the circuit as well as requiring additional interconnections between the high and low power devices.
It is therefore desirable to provide a device package which houses both the high and low power devices and in which the package size is reduced, and the number and lengths of interconnects are minimized.
SUMMARY OF THE INVENTION
The present invention provides an “adaptable planar module” (APM), namely a new packaging concept for motor control and similar functions. The package is especially suited for low cost and small motor control systems, though the basic concept can be extended to larger, higher power systems.
The APM of the invention includes a minimum IMS substrate suitable for the power devices and other devices. The IMS substrate may support an input bridge, an inverter, and other components and sits beneath an open cavity of a printed circuit board (“PCB”). The PCB and the IMS substrate are potted in a molded shell that is provided with connectors. The PCB provides a low cost platform for the low power devices that do not require heatsinking and thus need not be situated on the IMS substrate. Interconnecting the IMS and the PCB are standard wire bonds that connect the semiconductor die on the IMS substrate and those on the PCB.
The invention thus eliminates redundant interconnects, provides cost savings and improves reliability. Specifically, the partitioning of the devices and the IMS size reduction save cost. The size reduction and direct bond to the die also reduce the unit IMS cost by eliminating the need for special plating and by allowing for a thinner IMS.
The APM of the present invention typically includes an IMS, a printed circuit board, a support base or shell, power terminals, and grounding terminals. Environmental considerations may also be taken into account. An external control PCB with keypad and I/O terminals, a cover, and a heatsink may also be included.
The IMS substrate of the APM may include an inverter, one or three phase inputs, a thermistor, a negative buss shunt and a ground fault shunt. Epoxy or solder die attachments may be used. The substrate may be suitable for any or all of 0.18, 0.37 or 0.75 kilowatt applications. The size of the substrate is, for example, 1.2 inches by 0.8 inches. Also, pollution
1
standard compliance with a coating may be provided, as may be 2500 V dielectric isolation.
The shell or package of the APM may include a molded shell that supports the IMS, the power PCB and the cover. The shell, for example, has a footprint of about 2.83 inches×5.12 inches (72×130 mm) with extended terminals. Three or four, for example, M4 mounting screws may be used for earth, panel, internal and heatsink grounding, respectively. The package preferably has a low profile of 0.375 inches, as an example, and may be made of high temperature and high strength plastic.
The power PCB of the APM may typically be a single PCB that can include a drive circuit, protection circuits, SMPS, filters, buss capacitors, soft-charge, terminals and a control board interface connector. The PCB is generally, for example, about 5.2 inches×2.6 inches. Preferably, the PCB is formed of two layers, though four layers are also possible. The top side of the PCB may include an SMD and a through-hole. The bottom side of the PCB may include a SMD of, preferably, up to 1.3 inches. The PCB may also include pollution
1
spacing with both sides coated or potted.
The power terminals are typically LMI or Schneider type. As an example, a three output motor is used as well as a two or three input line. The PCB may be grounded to earth at the input end, and preferably meets UL 508C specifications at 600V. The power terminals may be soldered to the power PCB.
Preferably, the APM conforms to a pollution level 2 requirement, though level 3 conformity may be provided if select control pins are managed. The APM may also be protected from vibration, shock and other mechanical stresses.
The primary grounding of the APM is preferably the heatsink. A motor shield may be clamped to the heatsink for EMC specification compliant grounding and for motor grounding to the heatsink. An input side mounting screw may connect the line earth, panel and panel ground to the heatsink and to the internal ground. A jumper from the heatsink that internally grounds the EMC terminal may also be provided.
A control PCB may be included in the APM or may be provided externally and interface with a connector and ribbon cable. The control PCB may preferably include a microprocessor, “shrubbery”, keypad and a Wago I/O connector. The control PCB typically mechanically snaps into the cover and is connected by flex cable.
A cover may interface with the APM shell and is preferably a molded cover with a product-dependent height. The cover may provide a mechanical and electrical connection to the components, and may include a snap-on coupling to the shell and may permit mounting screws through the shell to the heatsink. The cover may also provide support for the control board and vents for capacitor cooling. Optionally, the cover is UL 50 specification compliant.
An external heatsink serves as the mounting surface for the APM. Three sizes are preferable for the heatsink, all of which preferably have the same footprint, namely an extruded aluminum heatsink for 0.37 kilowatt applications, extruded aluminum for 0.75 kilowatt applications, or an aluminum plate for 0.18 kilowatt applications. The heatsink is preferably sized for providing final power dissipation without using a fan. Typically, three or four tapped holes may be provided to connect the heatsink to the APM. The heatsink may also be mountable to a back panel or to a DIN rail.
The innovative shell design may provide any or all of the following features: location and support of the IMS substrate, optimum contact to the heatsink mounting surface, support of the PCB including wire bond support, space for SMD components on the bottom surface of the PCB, space for both SMD and leaded components on the top side of the PCB. A small depressed cavity above the IMS is provided for the IMS components and is preferably filled with a hi-grade potting compound that contacts the IMS die. The remainder of the package, including the PCB and other components, can thus be covered with a lower cost potting compound.
The shell may also create an external terminal housing, when such a housing is more cost effective than using procured terminals. Alternatively, the shell can create a partitioned area to attach procured terminals to the PCB.
Other, larger components such as buss capacitors, filter capacito
Corfield Michael A.
Dubhashi Ajit
Lin Heny W.
Siu Stephen Nicholas
Vaysse Bertrand P.
International Rectifier Corp.
Ostrolenk Faber Gerb & Soffen, LLP
Tolin Gerald
LandOfFree
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