Patent Application
20060097704
The present invention relates to voltage regulators, and more particularly, the present invention relates to voltage regulators for controlling voltage and current supplied from a generator or alternator used in maritime, automobile or motorcycle charging systems.
The charging system for an automobile, truck, motorcycle or boat typically includes an alternator or generator with appropriate windings, armature and stator components. A voltage regulator regulates the charging voltage and output current to provide consistent alternator or generator operation during varying loads that would create voltage drops and other operational problems. Many different regulator designs are commercially available, including discrete transistor, custom integrated circuit systems using Application Specific Integrated Circuits (ASIC), or hard-wired circuits that define a specific function for a specific type of application. These voltage regulators typically require the use of a heat sink for drawing heat away from the active and passive voltage regulator components, which are typically mounted on a conventional printed circuit board (PCB) or printed wiring board (PWB). The heat sink radiates excessive heat generated because of the voltage regulator operation into the atmosphere or mounting system.
This unwanted heat is generated at an integrated circuit (IC) junction or by other active components forming the voltage regulator circuit. When not carried away properly, this generated heat can impair or destroy the voltage regulator. In some cases, the heat can be so excessive, fires are started because of the proximity of the voltage regulator to a carburetor, fuel line, or other flammable substance or device. This problem is more problematic in those instances when space is minimal, and many vehicle components, including the engine, charging system, fuel delivery system and other components and associated vehicle systems are arranged in close proximity to each other.
Also, designed performance specifications for most commercially available voltage regulators assume the use of proper heat sinking. To ensure proper heat flow from the voltage regulator into a heat sink, it is sometimes possible to lower ambient temperature using ventilation, including a fan or other cooling technique. This adds cost and noise to a design and may not be in the original design specifications. It is also possible to lower the ambient heat by lowering the system operating power, but this is not always an adequate option because at peak load requirements, the voltage regulator will not adequately regulate voltage and/or current. It is also possible to choose higher current rated active and passive components, including any integrated circuits. This also adds cost and often requires a larger volume voltage regulator, which is not an acceptable design choice in some instances. Typical commercial heat sinks include Thermalloy, Wakefield, IERC, Staver, TO-204AA, TO-204AB, TO-226AA and similar commercially available heat sinks that have been applied to voltage regulator designs.
There are believed to have been some prior art proposals, for example, a voltage regulator sold by Unit Parts of Oklahoma City, Okla., for CS130 alternators, which uses a substrate board having conductive traces forming a printed circuit pattern, an insulator layer and a copper base layer operative as the heat sink. A lead frame assembly formed in the voltage regulator body includes interior terminals attached directly to the substrate board to connect components or the circuit pattern on the circuit board. This structure has not been found adequate because the direct connection of lead frame components is expensive to tool for automation, difficult to manufacture, and requires high tolerance.
It is therefore an object of the present invention to provide a voltage regulator that has lower operating temperatures, longer operating life, and is more durable and robust than prior art voltage regulators that use standard printed wiring (or circuit) boards or thick-film ceramics.
It is another object of the present invention to provide a voltage regulator that does not require the use of a large heat sink.
It is yet another object of the present invention to provide a voltage regulator that has a reduced board size, increased power density, lower operating temperature, and a reduced number of interconnects.
It is still another object of the present invention to provide a voltage regulator that uses surface mount technology.
The present invention is directed to a voltage regulator that controls voltage and current supplied from a generator or alternator, and includes a substrate board received on a voltage regulator body. The substrate board minimizes thermal impedance and conducts heat more efficiently and effectively than standard printed wiring boards and is more mechanically robust than thick-film ceramics and direct bond copper constructions often used in prior art voltage regulators.
The substrate board is received on the voltage regulator body and is formed as a metallic base layer, an insulator layer on the metallic base layer, and a circuit layer on the insulator layer and defining a printed circuit pattern. Active and passive voltage regulator components are mounted on the substrate board and interconnected by the printed circuit pattern to form a voltage regulating circuit. Connectors are carried by the voltage regulator body and adapted to be connected to devices controlled by the voltage regulator, including other components of the vehicle. Terminal connections are secured to the substrate board and operatively connected to selected active and passive components or printed circuit pattern and extend from the substrate board and interconnect the connectors carried by the voltage regulator body.
The voltage regulator body includes a board receiving cavity into which the substrate board is received. An insulator material typically fills the board receiving cavity and covers the substrate board and active and passive voltage regulator components. The voltage regulator body can also include a metallic surface on which the metallic base of the substrate board is secured.
In yet another aspect of the present invention, wire terminals are carried by the voltage regulator body and connected to the terminal connections and form a wiring harness. The voltage regulator body could be formed as an integrally formed metallic housing, or the voltage regulator could include a lead frame assembly formed of an insulator material with conductors embedded within the lead frame assembly and connected to the terminal connections. In this aspect of the invention, the terminal connections could be conductor pins that connect to internal terminals of the embedded conductors.
In yet another aspect of the present invention, the voltage regulator body is formed as an integrally formed, one-piece metallic housing, which can be configured for mounting on a powered vehicle, including a boat, automobile or motorcycle. The active and passive regulator components can be surface mounted components and adhered to the substrate board by reflow soldering.
The metallic base layer of the conductive substrate is typically formed from copper or aluminum, and in one aspect of the present invention, is preferably formed from aluminum. Solder connections secure at least a portion of the active and passive voltage regulator components on the circuit layer. The coefficient of thermal expansion for the aluminum base layer minimizes solder joint fatigue and enhances heat spreading. This aluminum base layer can have a thickness of about 0.020 to about 0.125 inches, in one non-limiting example.
The voltage regulator can be adapted for use in marine engine system applications, motorcycle system applications, A-circuit (low-side) vehicle system applications, B-circuit (high-side) vehicle system applications, and permanent magnet applications, as non-limiting examples. The same manufacturing techniques could even be applied to an ignition module used on magnetic pick-up vehicle system applications. A method of forming a voltage regulator in accordance with the present invention is also disclosed.
Other objects, features and advantages of the present invention will become apparent from the detailed description of the invention which follows, when considered in light of the accompanying drawings in which:
The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout, and prime notation is used to indicate similar elements in alternative embodiments.
The present invention advantageously provides a voltage regulator that overcomes the disadvantages of prior art voltage regulators that require large heat sinks to withdraw heat from the voltage regulation circuit, which controls voltage and current supplied from a generator or alternator in different vehicle applications, including automobile, motorcycle and marine systems. In accordance with the present invention, a substrate board is received on a voltage regulator body, for example, formed as a metallic housing or lead frame assembly.
This substrate board could be referred to as an insulated and conductive board because it includes a metallic base layer, such as formed from copper or aluminum, an insulator layer on the metallic base layer, and a circuit layer on the insulator layer and defining a printed circuit pattern. Active and passive voltage regulator components, such as transistors, resistors, capacitors, diodes and similar voltage regulator components, are mounted on the substrate board and interconnected by the printed circuit pattern to form a voltage regulating circuit. Terminal connections, for example, conductive pins, are secured to the substrate board and operatively connected to selected active and passive components and extend from the substrate board and interconnect connectors that are carried by the voltage regulator body. These connectors carried by the voltage regulator body could be conductors embedded in a lead frame assembly.
The use of the substrate board allows the active and passive components to be surface mounted on the substrate board use reflow soldering in an efficient manner. The use of the substrate board also minimizes thermal impedance and conducts heat more effectively and efficiently than conventional printed circuit (or wiring) boards. This substrate board is stronger than typical thick-film ceramics or direct bond copper construction systems, and does not require a large heat sink or heat interface material using clamps, brackets, fastening screws, or other mounting hardware typically associated with prior art heat sinks used in voltage regulators.
The use of the substrate board also reduces overall operating temperature, and can extend the life of active and passive components, including any semiconductor dies mounted on the board. Surface mount technology, including reflow soldering, is preferably used, thus, reducing the number of interconnects and improving thermal and mechanical performance.
Referring now to
As illustrated, the substrate board 106 is adhered by an adhesive 112, for example, a conductive epoxy into the board receiving cavity 104. An example of such adhesive is an RTV, gray/white, SYLGARD, Q3-6605 adhesive. A conformal coating 114 can be applied over the substrate board 106 and active and passive electronic components 116 that are surface mounted, such as by reflow soldering onto the substrate board.
The assembly process for the voltage regulator illustrated in
The substrate board and its active and passive components are covered completely with the conformal coating 114 and cured at room temperature for 15 minutes. It is possible to inspect with a UV inspection light and further curing can occur at 80° C. for 15 minutes.
As shown in
The substrate board can be formed by different manufacturing techniques, and one example of a board and its manufacturing process that can be used for the present invention is disclosed in U.S. Pat. No. 4,810,563, the disclosure which is hereby incorporated by reference in its entirety. Commercially available substrate boards that can be used as boards for the present invention include substrate boards manufactured by the Bergquist Company of Minneapolis, Minn. under the tradename ThermalClad®, or a similar thermal interface substrate board manufactured by Thermagon, Inc. of Cleveland, Ohio and sold under the tradename T-Lam.
Although a metallic base layer 150 such as aluminum or copper is disclosed and preferred, it is possible in some applications that the base layer altogether could be avoided. The benefits of the substrate board 106 include the avoidance of a large heat sink and its associated mounting hardware or other thermal interface material, because the substrate board is operable to minimize solder joint fatigue and enhance heat spreading. The board has a lower operating temperature with increased power density and a reduced board size when active and passive components are mounted thereon. The number of required interconnects is reduced because surface mount technology and reflow soldering techniques are used. Automatic pick and place equipment can be used for inserting the substrate board into the board receiving cavity.
Typically, the metallic base layer 150 is formed from aluminum, but copper can also be used. For example, the metallic base layer could be about 0.040 inches (1.0 millimeter) aluminum thickness and range from about 0.020 to about 0.125 inches in thickness. The metallic base layer is typically thicker than the other layers and has a coefficient of thermal expansion such that the solder joint fatigue is minimized and heat spreading enhanced. The copper base layers can also be formed about 0.020 to about 0.125 inches thick.
The dielectric layer 152 is typically a polymer/ceramic blended material that provides electrical isolation and low thermal impedance. This layer 152 resists thermal aging and has high bond strengths and incorporates a preferred ceramic filler to enhance thermal conductivity and maintain high dielectric strength. It is a thin layer and typically about 0.003 inches, but can range in thickness from as little as 0.001 inches to about 0.012 inches depending on what isolation is required.
The circuit layer 154 is the component-mounting layer and forms a printed circuit pattern 156 that interconnects the active and passive components 116. The trace width of the printed circuit lines forming the pattern 156 can vary depending on the type of dielectric, its thickness, and base layer. The circuit layer can typically be thinly formed as a foil layer from copper. In one non-limiting example, the thickness of the circuit layer can be as little as 0.0014 inches to as much as 0.0140 inches depending on voltage regulator design and application. In another example of the invention, the copper circuit layer 154 can be about 10% of the base layer thickness or thinner. This proportion can aid in maintaining circuit flatness, especially when an aluminum base layer 150 is used. The circuit design can include various etched surfaces, including vias. Minimum circuit width of the printed circuit patterns formed as traces can be about 0.005 inches or smaller to as much as 0.015 inches or larger. An exemplary minimum space/gap for a single layer (non-plated) can be about 0.007 inches to as much as 0.030 inches. It is also possible to form the substrate board as a multilayer board. A solder mask and silk screen design can be used during production.
Different surface finishes can be available, including Hot Air Solder Leveling (HASL), which is a 63/37 pB/Sn coating. Organic Solderability Protectant (OSP) can be used a thin coating to protect copper. Flow Solderable Tin (FST) can be used. If a copper base layer is used, the soldering process during a reflow process typically should not exceed 260° C. and, if an aluminum base layer is used, should not exceed 300° C. Usually a minimum of about 0.004 inches of solder is recommended to allow a good heat transfer and withstand thermal cycling. Silver can be added and an RMA flux used.
In this particular embodiment, the voltage regulator body 202 includes a lead frame assembly 260 formed from an insulator material with embedded conductors 262 forming a lead frame shown by dashed lines within the lead frame assembly. The lead frame 262 includes external lead frame terminals 264 that connect to wires and terminals of various devices controlled by the voltage regulator, or receive signals from other devices. The board receiving cavity 204 is an open cavity as illustrated and the embedded conductors 262 within the lead frame assembly 260 include internal terminals 266 that connect to the terminal connections 218 formed as conductive pins extending from the substrate board 206, which are bent and soldered onto the internal terminals 266 as shown in
During assembly, when the substrate board 206 is received into the board receiving cavity 204, all conductive pins 218 should be bent inward so that they do not interfere with the embedded conductors forming the internal terminals 266. The silicon gel or conductive epoxy or other adhesive can be used to secure the substrate board 206 and later a cavity cover. The conductive pins are bent and soldered to the internal terminals and the board receiving cavity 204 is filled with a silicon gel. The cavity cover is then placed over the cavity and secured using epoxy.
The illustrated voltage regulator 200 is predominantly used with a CS-series voltage regulator, for example, with a CS130 series alternator. The voltage regulator circuit could incorporate a field effect transistor having a drain terminal connected to B+ and to an integrated circuit chip, for example, its terminal A. An external sense connector could be connected to terminal 3 of the IC chip, which typically has dual sensing ability, either external or internal. This voltage regulator 200 is a B-circuit as a high-side drive with a voltage set point at about 14.7 volts. This voltage regulator can be light activated and the stator input can turn off the light. It preferably has a soft start feature.
The A-circuit voltage regulation in this example would typically include a slip-on brush-ring of about 26 millimeter ID. The voltage regulator 300 includes a voltage regulator body 302 that includes a lead frame assembly 360 formed from an insulator material using embedded conductors 362 include external lead frame terminals 364 and internal terminals 366 (shown by dashed lines) to be connected to terminal connections 318 as conductive pins on the substrate board 306 as shown in
The terminal connections 318 formed as conductive pins are received within pin receiving slots 359a of a brush holder 359 formed as part of the lead frame assembly 360. The internal terminals 366 from the lead frame assembly 360 connect to the conductive pins 318. The lead frame assembly 360 includes the external lead frame terminals 364 to form a B+ trio terminal 372, a stator terminal 374, and an “F” or bottom brush terminal 376 and can include a ring assembly (not shown). This type of voltage regulator for Mitsubishi is sold as one example under the designation IM265 by Transpo Electronics, Inc. and has a system voltage of 12 volts and is used on the “A” circuit or low side drive with a trio excitation. It is indicator light activated, and in one example, is a 28 millimeter brush ring and has an operating temperature range of about −40° C. to about 125° C. It has a field current of about 4 amps and a voltage set point at 4,000 rpm of about 14.5 volts. It includes a B-terminal 378 and can include a field terminal 380 at the top. The pins as terminal connections from the substrate board include a sense pin 382, light pin 384, and trio pin 386 on one side, and a field pin 388 and ground pin 390 on the other side and as shown in the plan view of the substrate board in
The conductive pins are typically inserted through the brush holder 359 as part of the lead frame assembly and are bent and soldered. Epoxy or other adhesive 395 can be added into the opening between the substrate board and the brush holder 359 as part of the lead frame assembly to fill the entire cavity during assembly.
It is also possible that the substrate board and manufacturing techniques with regard to the voltage regulators could be used for some ignition modules.
The present invention is advantageous and provides an enhanced voltage regulator used for automobile, motorcycle and marine applications in which the substrate board is secured to the voltage regulator body and receives the active and passive voltage regulator components to provide enhanced voltage regulator operation and advanced design that can withstand heat and provide greater thermal conductivity as described above.
Many modifications and other embodiments of the invention will come to the mind of one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is understood that the invention is not to be limited to the specific embodiments disclosed, and that modifications and embodiments are intended to be included within the scope of the appended claims.
