Patent Publication Number: US-2006018100-A1

Title: Active plate-connector device with built-in semiconductor dies

Description:
BACKGROUND OF THE INVENTION  
      In automobile industry, battery power is distributed through a module called Power Distribution Center (PDC), or Power Management Module. PDC works like a power panel. It distributes power from battery and alternator to various loads such as lights, pumps, blowers, radiator fan, door locks, power windows as well as other control modules, such as Engine Control Module, Antilock Brake Module, Air-Bag Module, etc. In addition to controlling power distribution, PDC provides various protections such as short circuit protection, overload protection, overheat protection, etc.  
      Historically, PDC utilizes relays and fuses to switch loads ON/OFF and perform short circuit protection. There are a lot of disadvantages associated with relays. Large size, contact arc, ware and tare are problems. Large coil power consumption is another problem.  
      With the development of semiconductor technology such as MOSFET, IGBT, etc., more and more relays are replaced by semiconductor switches. For the same current-handling capacity, the ON resistance of a semiconductor transistor is the same or even lower than the relay contact-resistance while the size is only a fraction of the relay. Unlike relays, when a semiconductor switch is turned ON, it needs little current to hold it ON. Semiconductor device works very well for low level current. However, when the load current is large, such as 10 A, 20 A, 50 A or more, there is a packaging problem of the semiconductor itself. There is a PCB trace problem. There is also a heat dissipation problem on the PCB.  
      For a semiconductor device, packaging is the bottleneck to reduce the ON resistance and current carrying capacity. For example, a semiconductor die has 1.0 mΩ ON resistance, but the packaged device resistance increases to 2.4 mΩ. The die can carry 307 A current, but the packaged device can carry only 100 A due to the limited space for pins and bonding wires in the package.  
      For large current, the copper on a PCB must be thick. Copper trace must be wide. It is expensive and difficult to make copper thicker than 10 OZ on the PCB. Even 10 OZ copper is not thick enough for large current. Wide trace not only takes large board space, but also is difficult to route to the board connectors for load connection. Wide traces must be narrowed down when they approach to the connectors. As a result, the copper trace consumes significant amount of energy. The copper loss could be up to 30% of the semiconductor loss. Both the copper loss and semiconductor loss are turned into heat. There was an experience that a 100 A PDC was burned out due to accumulative heat generated by PCB trace and semiconductor. To prevent fire hazard, PDC must be large and ventilated. Small size and good thermal property is not possible with packaged semiconductor devices on the PCB.  
     SUMMARY OF THE INVENTION  
      The present invention moves all large-current semiconductors out of main PCB. The semiconductor dies are used in their die form. The semiconductor dies are installed inside a plate-connector device. The plate-connector device includes power plate, power terminals, built-in PC board, dies, sensors, signal pins, etc. The power plate is the common power input for all channels. It is made of thick metal. The substrates of all semiconductor dies are soldered on the power plate. The power supply is directly connected to the power plate. The power terminals are the output of the device. Each channel has at least one power terminal. One section of the power terminals are connected to the output of the semiconductor dies through bonding wires or soldering means. The other section of the power terminals is connected to various loads through mating terminals and wires. The built-in PC board holds signal pins, sensors, etc. and provides signal pads for control and sense signal connection to semiconductor dies. The signal pads on built-in PC board are connected to signal pads of a die, such as gate pads, current-sense pads, temperature-sense pads, etc. with wire-bonding method or soldering method.  
      Since the dies are directly mounted on the power plate, the plate serves as a good heat sink. In addition, the unique structure thermally connects the power terminals to the dies. As a result, the power terminals, the mating terminals and the wires connected to the mating terminals also serve as heat sinks.  
      If a PDC has many high-current channels, several connectors can share the same power plate to form a single plate—multi connector device. The connection between a main PCB and the plate-connector device has only signal pins. There is no large current device on the main PCB. There is no large current flowing between the main PCB and the plate-connector device. The main PCB performs control functions such as ON/OFF, short circuit protection, overload protection, thermal protection, over voltage protection, under voltage protection, etc. through these signal pins. The ON resistance of the plate-connector device is virtually the die resistance. The unique package adds little resistance to the overall resistance. As a result, the maximum device current is the maximum die current, not limited by the package. The current capacity of the new device is more than three times higher compared to the traditional package. Since there is no large current trace on the main PCB, the traces on the PCB can be very narrow. The components can be densely populated on the board and the board size will be very small. With invented structure, the traditional packaging problem, thermal problem and PCB copper trace problem are all solved by the following methods: moving power devices out of main PCB, allowing spacious space for packaging compared to old package, connecting dies directly to a big power plate, connecting dies directly to a big power terminal, Reducing heat source by reducing the package resistance. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       FIG. 1  is the drawing for wire bonding connection with a separate PC Board illustration.  
       FIG. 2  is the drawing for soldering connection with a separate PC Board illustration. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       FIG. 1  shows a plate-connector with four power terminals  7 . There can be more than one connector sharing the same power plate  5 . Each connector can have any number of power terminals  7 . The connectors can be at one side of the power plate  5  or at different sides of Power Plate  5 . The following description utilizes an N-channel MOSFET die as an example, but the basic structure applies to any other types of semiconductor dies such as P-channel MOSFET, BJT, IGBT, GTO, MCT, etc. even though the pad names are different. In the drawings, if a group of elements have the same shape and size, they are identical elements. For clarity, not all identical elements have legends.  
      Power plate  5  is made of good conductive metal. Power plate  5  can be connected to power source such as a battery by various means. For example, it can be bolted to the power source through Mounting Holes  4 , or welded, or soldered to the power source. The drains of Dies  1  are soldered on Power Plate  5  through solder  8 . The sources of Dies  1  are wire-bonded to Power Terminals  7 . PC Board  6  and Insulator  9  are sandwiched between Power Plate  5  and Power Terminals  7 . Insulator  9  can be a standalone insulation layer or a coated insulation layer on the PC Board  6 . Signal pads of Dies  1 , such as gate pads, temperature sensor pads, current sensor pads, etc. are wire-bonded to Signal Pads  14  on PC Board  6 . Signal Pins  10  are mounted or soldered on the bottom side of PC BOARD  6 . Signal Pins  10  are connected to signal pads of Dies  1  through Copper Traces  11  of PC BOARD  6 , Signal Pads  14  on PC BOARD  6  and Bonding Wires  19  between PC BOARD  6  and Dies  1 . For simplicity, only a few copper traces  11 , a few copper pads, a few bonding wires, a few signal pads on the dies and a few signal pins are shown in the drawings. The actual number of those pads, traces, bonding wires and signal pins may be different from those shown in the drawings.  
      There are copper Thermal Pads  15  on both sides of PC Board  6 . Thermal Vies  13  connect Thermal Pads  15  from one side to the other. Power terminals  7  are soldered on the bottom side of PC board  6 . Sensors  12  are soldered on the bottom side of PC Board  6  or inside Sensor Holes  16  in PC Board  6 . Sensor Holes  16  pass through in Insulator  9 . Sensor Holes  16  are filled with thermal conductive material such as thermal grease or thermal compound. Insulator  9  is made of good thermal conductive material. Insulator  9  prevents copper traces on PC Board  6  from being shorted to Power Plate  5 . When assembled, PC Board  6  and associated Insulator  9  are attached to Power Plate  7 . Sensors  12  are thermally connected to Power Plate  5  through filled thermal conductive material inside Sensor Holes  16 . Power Terminals  7  are thermally connected to Power Plate  5  through Thermal Vies  13  and Insulator  9  because Insulator  9  is a thermal conductive material.  
      One of Signal Pins  10  in each channel is connected to the channel&#39;s Power Terminals  7  which is wire-bonded to associated source pad of Dies  1 . The source signal of Dies  1  is needed outside the assembly for control purpose. Some Signal Pins  10  are connected to Sensors  12  either directly or through copper traces  11  on PC Board  6 , depending on the position of Signal Pins  10 .  
      Signal pads on Dies  1  are wire-bonded to Signal Pads  14  on PC Board  6  by Bonding Wires  19 . Source pads on Dies  1  are wire-boned to Power Terminal  7  by Bonding Wires  2 . Before wire bonding, it is necessary to hold all pads to be wire-bonded in fixed position. Power Terminals  7  are soldered onto PC Board  6 . PC Board  6 , Insulator  9  and Power Plate  5  can be held together for wire bonding in any sticky means. The similar process used to glue big surface-mount IC chips to a printed circuit board before reflow is one example.  
      The plate-connector device is molded in a plastic housing in any connector shapes. The molding structure is not shown in the drawings. Molding Holes  3  pierce through Power Plate  5 , insulator  9  and PC Board  6 . During molding, plastic is filled inside the holes and forms plastic nails between the top part and the bottom part of the housing to enhance mechanical strength.  
      In  FIG. 2 , Power plate  5  can be connected to power source such as a battery by various means. For example, it can be bolted to the power source through Mounting Holes  4 , or welded, or soldered to the power source. The drains of Dies  1  are soldered on Power Plate  5  through solder  8 . The sources of Dies  1  are soldered on Power Terminals  7  through solder  18 . Solder  18  passes through Solder Holes  17  in PC Board  6 . In the drawings, there is one square Solder Hole  17  for each Power Terminal  7 . It by no means limits the shape or number of Solder Holes  17 . Solder Holes  17  can be any shape and number for each Power Terminal  7 . PC Board  6  is positioned between Dies  1  and Power Terminals  7 . Signal pads of Dies  1  are soldered onto Signal Pads  14  at the bottom side of PC Board  6 . Signal Pads  14  are connected to Signal Pins  10  through Copper Traces  11  of PC Board  6 . Sensors  12  are soldered on the bottom side of PC Board  6  or inside Sensor Holes  16  in PC Board  6  and connected to Signal Pins  10 . Sensors  12  are thermally connected to Power Terminals  7  through filled thermal conductive material inside Sensor Holes  16 .  
      The plate-connector device is molded in a plastic housing in any connector shapes. The molding structure is not shown in the drawings. Molding Holes  3  pierce through Power Plate  5  and PC Board  6 . During molding, plastic is filled inside the holes and forms plastic nails between the top part and the bottom part of the housing to enhance mechanical strength.