CN117178635A - Power converter packaging structure with copper bar heat enhancement type interposer with cooling fins - Google Patents

Abstract

The power converter module has a switch Printed Circuit Board (PCB) with power transistors that generate heat. The power transistor's ground, power input and power output are directly connected to an interposer heatsink soldered between the switch PCB and the system PCB through metal traces on the switch PCB. Copper bars attached to the bottom of the interposer heat spreader may be inserted into holes in the system PCB for connection. The metal traces and interposer heat sinks carry power or ground current and heat away from the power transistors. These power and ground currents flow from the interposer heat sink to the system PCB through the copper bars. The interposer PCB has pads and solder balls thereon to transfer control signals from the system PCB to the switch PCB, bypassing the interposer heat sink. The copper strips may be sintered, welded or brazed to the interposer heatsink or integrally formed therewith.

Description

Power converter packaging structure with copper bar heat enhancement type interposer with cooling fins

[ related application ]

The present application is a partially extended application (CIP) of U.S. patent application US17676960, "thermally enhanced interposer with cooling fins" filed on 22 nd 2022.

[ field of technology ]

The present invention relates to electronic modules, and in particular to a Switch Mode Power Supply (SMPS) module having a heat sink in the conductive path.

[ background Art ]

Power converters are widely used to convert one power supply voltage to another. A Switched Mode Power Supply (SMPS) has a transistor that turns on and off rapidly to cause current to flow from a supply input voltage terminal to a supply output inductor and capacitor that can filter the load.

Fig. 1 shows a prior art Switched Mode Power Supply (SMPS). The power input voltage vin+ will be converted to a power output voltage vout+. Both the input and output use a common ground GND, but some systems have separate grounds.

An input capacitor 320 between vin+ and GND filters the input of the drains of the pull-up transistors 302, 306 and is connected to the sources of the pull-down transistors 304, 308. The source of pull-up transistor 302 and the drain of pull-down transistor 304 are connected together to drive vout+ through inductor 312 to charge output capacitor 330.

The gate G1 of the pull-up transistor 302 is driven high to turn on the transistor 302 for a period of time to charge the output capacitor 330. Once G1 is driven low, the gate of pull-down transistor 304 is driven high to discharge output capacitor 330. The signals of G1, G2 are typically clock signals in the kHz frequency range, the duty cycle being adjusted to obtain the desired output voltage vout+ for a particular input voltage vin+. For example, by increasing the high level time (duty cycle) of G1 relative to G2, a higher vout+ can be obtained.

Similarly, the source of pull-up transistor 306 and the drain of pull-down transistor 308 are connected together to drive vout+ through inductor 314 to charge output capacitor 330. The switching signals applied to the gates of transistors 306, 308 may be 180 degrees out of phase with the switching signals driving the gates of transistors 302, 304 to reduce output ripple.

Transistors 302, 304, 306, 308 may be n-channel Metal Oxide Semiconductor Field Effect Transistors (MOSFETs), but gallium nitride (GaN) transistors are recently being used because they can provide higher currents for a particular physical transistor size. GaN transistors allow for higher density power converter modules because higher power supply currents can be provided using GaN devices for a given power converter module or package size.

One disadvantage of the higher density power converter modules is that very high power supply currents generate a large amount of heat. The thermal performance of the power converter module and its packaging becomes very important. The heat generated by the large current through GaN transistors 302, 304, 306, 308 must be conducted and dissipated quickly or hot spots may occur. These hot spots can damage the GaN transistor and even melt the solder joints within the module.

Traditionally, heat sinks are attached directly on top of switching transistors or other heat generating Integrated Circuit (IC) packages. The fan can provide better air flow and radiate the heat of the radiator.

Unfortunately, transistor packages are typically made of materials that have poor thermal conductivity, such as plastics or ceramics. Heat may also be conducted through package leads, pins, or solder balls at the bottom of the package that electrically connect the package transistor to an external system, such as traces on a Printed Circuit Board (PCB). The heat may then be distributed through the PCB, which typically has a much larger surface area than the power converter module. However, PCBs also have thermal insulation materials, such as fiberglass, so the amount of heat that the PCB can dissipate may be limited.

When the power converter has an array of solder balls attached to the system PCB, heat can be safely transferred through the Ball Grid Array (BGA). However, when the array of solder balls is not large enough, or a non-BGA package is used, more heat is transferred through fewer package leads. These fewer wire bond pads may then become hot spots, heating to the point where they melt or otherwise damage the bond pads. The insulating material in the PCB may prevent this heat from being dissipated from these solder joints at a high enough rate to cause localized hot spots and potential damage. The heat dissipation efficiency of the PCB is much lower than that of the metal heat sink.

Patent application US17676960 shows a power converter module with a heat sink integrated into the electrical signal path between the power conversion transistor and the system PCB. Heat flowing through the electrical path to the system PCB is intercepted by the metal heat sink and effectively dissipated. Instead of attaching heat sinks on top of the package, several heat sinks are soldered to the electrical interconnections of the package with solder balls, and then these heat sinks are connected to the system PCB, with electrical connections made through the heat sinks.

Solder ball connections, while useful, have a lower melting point than other components and thus may be points of failure. It is desirable to replace these solder ball connections with copper bars or pins to improve reliability and increase the cross-section of current flow.

[ description of the drawings ]

Fig. 1 shows a prior art Switched Mode Power Supply (SMPS).

Fig. 2 shows a side view of a power converter module with an interposer heat spreader that conducts heat and electrical signals to a system board, and copper bars.

Fig. 3 shows an exploded view of a power converter module with an interposer heat sink and copper bars.

Fig. 4 shows a cross-sectional view of a power converter module with an interposer heat sink and copper bars, with metal PCB traces highlighted.

Fig. 5 shows an exploded view of a power converter module with an interposer heat sink and copper bars, with metal PCB traces highlighted.

Fig. 6 shows an exploded view of a power converter module with an interposer heat spreader and copper bars, with the solder highlighted.

Fig. 7 shows a side view of the final assembled power converter module with interposer heat sinks and copper bars, increasing the gap between PCBs.

Fig. 8 shows a side view of the final assembled power converter module with interposer heat sinks and copper bars, but attached to the interposer PCB using solder balls.

Fig. 9 shows a 3D top view of a power converter module with an interposer heat spreader and copper bars.

Fig. 10 shows a 3D top view of a power converter module with copper bars and a vertical fin interposer heat sink.

Fig. 11 shows a 3D top view of an asymmetric power converter module with interposer PCBs placed in the corners with copper bars on the interposer heat spreader.

Fig. 12 shows a 3D bottom view of a power converter module with copper bars and a vertical fin interposer heat sink.

Fig. 13 shows a 3D bottom view of a power converter module with copper bars on one side and pins on the interposer PCB side.

Fig. 14 shows a 3D bottom view of the power converter module with interposer heat sinks having pins instead of copper bars.

[ detailed description ] of the invention

The present invention relates to improvements to power supply modules. The following description is presented to enable one of ordinary skill in the art to make and use the invention in the context of a particular application and its requirements. Various modifications to the preferred embodiment will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments. Thus, the present invention is not intended to be limited to the particular embodiments shown and described, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Fig. 2 shows a side view of a power converter module with an interposer heat sink and copper bars that conduct heat and electrical signals to a system board. Copper bars 62 replace the solder ball connections between interposer heat sinks 22, 24 and PCB 10 in the parent application. Since the melting point of the copper bar 62 is higher than that of the solder ball, the reliability is improved. Moreover, the cross-sectional area of the copper bar 62 may be greater than the cross-sectional area of the solder ball connection, thereby reducing current crowding and heating. Another benefit is that the bottom of the interposer heat sink 22 may be farther from the top surface of the system PCB 10, thereby allowing some air flow in the horizontal gap between the interposer heat sinks 22, 25, the interposer PCB 50, and the system PCB 10.

The switch PCB 30 is a circuit board with wiring traces connected to Integrated Circuit (IC) packages 32, 34 mounted on its top surface. For example, the IC packages 32, 34 may contain GaN switching transistors, such as one or more of the transistors 302, 304, 306, 308 in fig. 1. Other devices such as capacitors or inductors may be mounted on top or bottom of the switch PCB 30, such as the capacitor 36.

The switch PCB 30 is not directly mounted to the system PCB 10. Instead, metal trace pads on the bottom of the switch PCB 30 are soldered to the interposer heat sinks 22, 24. The bottom of interposer heat spreader 22 and the bottom of interposer heat spreader 24 have copper bars 62 extending downward. Similarly, interposer heatsink 24 also has copper bars 62 extending downward. The bottom of the copper bar 62 may be loaded into the hole and then soldered to the system PCB 10.

For example, the interposer heat spreader 22 may be connected to ground traces on the system PCB 10 by copper bars 62, while the interposer heat spreader 24 may be connected to vin+ power traces on the system PCB 10 by copper bars 62. Another interposer heatsink and its copper bars 62 (not shown) located behind interposer heatsink 22 may be connected to vout+ power traces on system PCB 10.

Some control signals switch quickly, for example, to gates G1-G4 of transistors 302-308 (FIG. 1). These control signals are sensitive to large capacitive loads, such as those from interposer heat sinks 22, 24. These control signals are not connected to any interposer heat sink, but rather are connected from the system PCB 10 to the interposer PCB 50 through pins 88. The interposer PCB 50 has holes into which the pins 88 fit, with metal traces running around the holes. The reflowed solder then fills the gaps between the pins 88 and the metal traces on the interposer PCB 50, establishing secure electrical connections for the various control signals.

The capacitance added to these control signals by interposer PCB 50 and pins 88 is much smaller than the capacitance added to the power and ground signals vin+, vout+, GND (which pass through interposer heat sinks 22, 24). Since the power and ground signals already have large capacitances, such as those from the input capacitor 320 and the output capacitor 330 (fig. 1), the additional capacitance from the interposer heat sinks 22, 24 is not a problem.

The interposer PCB 50 is located in the cavity 26 between the interposer heat sinks 22, 24. The thickness of the interposer PCB 50 is approximately the same as the thickness of the interposer heat sinks 22, 24.

Fig. 3 is an exploded view of the components of a power converter module with an interposer heat sink and copper bars. Copper strips 62 may be attached to the bottom of interposer heatsink 22, as shown in fig. 2, or inserted into slots in the bottom of interposer heatsink 22, as shown on the left side of fig. 3, or copper strips 62 may be integrally formed with interposer heatsink 24, as shown on the right side of fig. 3. Some methods of attaching the copper bars 62 to the interposer heat sinks 22, 24 include sintering (e.g., nano-silver sintering), ultrasonic welding, brazing, and the like. Copper bars 62 may be attached to the bottom surface of interposer heatsink 22, or grooves, depressions, slots, holes, or other reserved areas. The copper strips 62 may be pre-assembled with the interposer heat sinks 22, 24.

The switch PCB 30 has mounted thereon IC packages 32, 34 and a capacitor 36 to form a subassembly. After the IC is mounted to form a subassembly, the interposer heat sinks 22, 24 with copper bars 62 and the interposer PCB 50 may be secured to the bottom surface of the switch PCB 30. Once the interposer heat sinks 22, 24 and interposer PCB 50 are soldered to the bottom surface of the subassembly of switch PCB 30, the bottom of copper bar 62 may be inserted into hole 65 in system PCB 10, thereby connecting the enhanced subassembly to system PCB 10. Copper strips 62 are then soldered into these holes by standard reflow soldering. Moreover, the pins 88 of the interposer PCB 50 are inserted into other smaller holes in the system PCB 10, and soldering may be performed in the same reflow step that connects the copper bars 62 to the system PCB 10.

Fig. 4 is a cross-sectional view of a power converter module with an interposer heat sink and copper bars, highlighting the metal PCB traces. The switch PCB 30 has a plurality of metal layers 41, which metal layers 41 are patterned into traces. The traces on one metal layer may be connected to the traces on the other metal layer by metal vias to form interconnects that may pass from the metal pads on the top metal layer to the metal pads formed on the bottom metal layer of the PCB. The system PCB 10 also has metal layers 11, these metal layers 11 being patterned into traces that can be connected to traces on other metal layers by metallized vias.

IC package 32 has GaN transistors, such as pull-down transistor 304 (fig. 1), which generate heat when switching large currents. The ground terminal of the transistor is connected to a lead at the bottom of the IC package 32 that is soldered to a metal pad on the top surface of the switch PCB 30. The interconnect 42 is formed by metal pads on the top surface of the switch PCB 30 and metal pads on the bottom surface of the switch PCB 30, possibly with traces on other metal layers inside the switch PCB 30, and metal vias between the layers. Interconnect 42 is a metal path from the bond wire of IC package 32 to interposer heatsink 22. The copper bars at the bottom of interposer heatsink 22 fit into holes 65 on the system PCB and are then soldered to metal pads on the top surface of system PCB 10 and to other metal layers around holes 65. The sidewalls of the holes 65 may be metallized prior to insertion of the copper bars 62, similar to metallized vias, but of a larger size. These metal layers around the hole 65 are connected to other metal layers within the system PCB 10 by metallized vias and traces to form an interconnect 12, which interconnect 12 is connected to system ground.

Ground return (Ground return current) from the GaN transistors in IC package 32 passes through interconnect 42, through the metal and copper strips 62 of interposer heatsink 22, to interconnect 12, and then to ground of system PCB 10. The heat generated by this GaN transistor in IC package 32 is also conducted along the metal path of interconnect 42 through switch PCB 30 to interposer heat spreader 22, with heat dissipation fins 202 providing a large surface area to dissipate the heat. Thus, both current and heat are carried away from IC package 32 through interconnect 42. The fins 202 cause the interposer heat spreader 22, the copper bars 62, the interconnect 42, and the interconnect 12 to be at a lower temperature than the interconnect 42 and the interconnect 12 that are directly connected together without the interposer heat spreader 22 and the copper bars 62. The interposer heat spreader 22 and copper bars 62 may be constructed of a highly conductive metal, such as copper or aluminum, that is effective in conducting heat and electricity.

IC package 34 has GaN transistors, such as pull-up transistor 302 (fig. 1), that generate heat when switching large currents. The power terminal of the transistor (VIN + fig. 1) is connected to leads at the bottom of the IC package 34 that are soldered to metal pads formed on the top surface of the switch PCB 30. The interconnect 44 is formed by metal pads on the top surface of the switch PCB 30 and metal pads on the bottom surface of the switch PCB 30, possibly with traces on other metal layers within the switch PCB 30, and metal vias from layer to layer. Interconnect 44 is a metal path from the solder VIN + power lead of IC package 34 to interposer heatsink 24. The bottom of interposer heatsink 24 is connected by copper bars 62 inserted into another hole in the system PCB (which hole is surrounded by metal), through metallized vias to other metal layers within system PCB 10, forming interconnect 14, which interconnect 14 is connected to the input supply voltage vin+ of system PCB 10.

The power input current to the GaN transistor in IC package 34 passes through interconnect 44, through the metal and copper bars 62 of interposer heatsink 24, to interconnect 14, and then to the VIN + power input of system PCB 10. The heat generated by this GaN transistor in IC package 34 is also conducted along the metal path of interconnect 44 through switch PCB 30 to interposer heat sink 24, with fins 204 providing a large surface area to dissipate this heat. Thus, both the current flowing to the IC package 34 and the heat from the IC package 34 are carried by the interconnect 44. The fins 204 provide the interposer heat spreader 24, interconnect 44, copper bar 62, and interconnect 14 with a lower temperature than the interconnect 44 and interconnect 14 directly connected together without the interposer heat spreader 24 and copper bar 62.

The other transistor terminals, such as gate G1, carry control signals. For example, the gate G1 of the pull-up transistor 302 in the IC package 34 is connected to the interconnect 48, through the switch PCB 30 to the pin 88, and then to the interposer PCB 50. The interconnect 58 is formed by patterned metal traces on several layers in the interposer PCB 50 and vias between them. The top of the pins 88 may be inserted into holes or metallized through holes on the interposer PCB 50 and the bottom of the pins 88 may be inserted into holes or metallized through holes on the system PCB 10. The metal 19 surrounding the hole in which the bottom of the pin 88 is inserted is connected to the interconnect 18 by a metal trace, and the interconnect 18 is connected to control signals generated by other circuits on the system PCB 10 or to control signals generated by other circuits on another daughter board of the system PCB 10. Thus, control signals (e.g., gate control signal G1) form a circuit from system PCB 10, through interconnect 18 and pin 88 to interconnect 58, through interposer PCB 50 to interconnect 48, and through switch PCB 30 to IC package 34. While the interconnect 58 also carries heat, the interposer heat spreader 24 provides sufficient cooling through the interconnect 44 to cool the IC package 34 so that the interconnect 58 is not too hot.

Both heat and current flow through the interconnects 42, 44. Heat is dissipated by fins 202 of interposer heat spreader 22 and a current to ground flows through interposer heat spreader 22. Heat is dissipated by fins 204 of interposer heat spreader 24 and current from power input v+ (VIN +) of fig. 1 flows through interposer heat spreader 24.

Fig. 5 is an exploded view of a power converter module with an interposer heat sink and copper bars, highlighting the metal PCB traces. The switch PCB 30 has a metal layer 41, the metal layer 41 being patterned into traces interconnected by metallized vias. Interconnect 42 is connected to one or more ground terminals of IC package 32, such as metal leads, bent pins, or solder balls at the bottom of IC package 32. The interconnect 44 is connected to one or more power terminals of the IC package 34, such as leads, bent pins, or solder balls at the bottom of the metal IC package 34. Interconnect 48 is connected to a control terminal of IC package 34.

Interposer PCB 50 also has metal layers formed as metal traces with vias connecting the metal layers. The interconnect 58 is used to connect control signals directly from the switch PCB 30 to the system PCB 10 without being connected to an interposer heat sink. The pins 88 are inserted into holes in the interposer PCB 50 and soldered to the surrounding metal and interconnects 58.

Likewise, the system PCB 10 has a metal layer 11, the metal layer 11 forming an interconnect 12 connected to ground, an interconnect 14 connected to a power input v+ (vin+ of fig. 1), and an interconnect 18 connected to a control signal.

During assembly, the interposer PCB 50 is placed in the cavity 26 between the interposer heat sinks 22, 24 and soldered to the bottom of the switch PCB 30. Copper strips 62 are attached to the bottom of interposer heat sinks 22, 24. Pins 88 are inserted and soldered into holes on interposer PCB 50.

The assembly of switch PCB 30, interposer heat sinks 22, 24 with copper strips 62, and interposer PCB 50 is then connected and soldered to system PCB 10. The bottom of the copper bar 62 is inserted into the hole 65 of the system PCB 10 and the bottom of the pin 88 is inserted into the smaller hole of the system PCB 10, around which the metal 19 is located.

Fig. 6 is an exploded view of a power converter module with an interposer heat spreader and copper bars, with solder highlighted. During assembly, solder is applied to the bottom surface of the switch PCB 30. When the switch PCB 30 is placed on the interposer heat sinks 22, 24 and the interposer PCB 50 and heat is applied, the solder flows back and adheres to the exposed metal, such as metal pads, to form solder balls 64 that connect to the interposer heat sinks 22, 24 and the interposer PCB 50. Solder paste is also applied to the top surface of the interposer PCB 50 to form solder balls 69 that melt into solder balls 64 during assembly.

Instead of using solder balls to connect the bottoms of the interposer heat sinks 22, 24 to the system PCB 10, copper bars 62 are inserted into holes 65 of the system PCB 10. The pins 88 are inserted into smaller holes in the system PCB 10 surrounded by the metal 19. Solder paste applied to the top surface of the system PCB 10 then forms a solder connection upon reheating.

Solder may also be applied to the bottom of copper bar 62 and pins 88 prior to insertion into the holes of system PCB 10.

Fig. 7 is a side view of the final assembled power converter module with interposer heat sinks and copper bars, increasing the gap between the PCB boards. Solder balls 64 are heated and reflowed during assembly to form solder joints. The interconnects 42 are connected to the top of the interposer heatsink 22 by solder balls 64, while the copper bars 62 are attached to the bottom of the interposer heatsink 22, connected to the interconnects 12, to form a ground path that also carries heat away from the IC package 32 for dissipation by the fins of the interposer heatsink 22.

Likewise, interconnects 44 are connected to the top of interposer heatsink 24 by solder balls 64, while copper bars 62 attached to the bottom of interposer heatsink 24 are soldered into holes 65 of system PCB 10 to connect to interconnects 14, thereby forming a path to the positive power supply that also carries heat away from IC package 34 for dissipation by fins of interposer heatsink 24.

Interconnect 48 is connected to the top of interposer PCB 50 by solder balls 64, while pins 88 connect the bottom of interposer PCB 50 to metal 19 and interconnect 18, forming a path for control signals.

Fig. 8 is a side view of the final assembled power converter module with interposer heat sinks and copper bars, but attached to the interposer PCB using solder balls. In this alternative, the copper bar 62 is pushed further into the hole 65, or the copper bar 62 has a shorter height. The gap between the PCB boards is reduced. The solder balls 67 at the bottom of the interposer PCB 50 are then connected to the metal pads 19 on the top surface of the system PCB 10. Pin 88 is replaced with solder ball 67 to establish a connection for control signals.

The solder balls 63, 64, 67 are heated and reflowed during assembly to form solder joints. The interconnects 48 are connected to the top of the interposer PCB 50 by solder balls 64, while solder balls 67 connect the bottom of the interposer PCB 50 to metal pads on the top surface of the system PCB 10, which are connected to the metal 19 and the interconnects 18, to form paths for control signals.

Solder balls 64 may provide an easier assembly process because it is not necessary to assemble pins 88 into the hole array of system PCB 10 prior to reflow. However, the smaller spacing or gap between the system PCB 10 and the interposer PCB 50 may impede airflow and cooling as compared to the larger gap in fig. 7. Solder balls 63 may also be provided between the bottoms of interposer heat sinks 22, 24 and metal pads (e.g., interconnects 12) on the top surface of system PCB 10.

Fig. 9 is a 3D top view of a power converter module with an interposer heat spreader and copper bars. The top of the switch PCB 30 faces upward. The interposer heat sinks 22, 24, 25 prevent the switch PCB 30 from contacting the system PCB 10, and in this 3D top view the system PCB 10 is located below the interposer heat sinks 22, 24, 25. The interposer PCB 50 is soldered to the bottom of the switch PCB 30, laterally between the interposer heat sinks 22, 25. Pins 88 for control signals extend downwardly from interposer PCB 50 to the same height as copper bars 62.

The copper strips 62 for the interposer heat spreader 24 are wider than the copper strips 62 for the interposer heat spreaders 22, 25 because the interposer heat spreader 24 is twice as wide as the interposer heat spreader 22. The width of the copper strips 62 may extend nearly the entire width of the interposer heatsink 22, providing a broad cross-section for current flow, reducing current crowding and heating.

The plastic housing 66 covers the top of the switch PCB 30, the IC packages 32, 34, and other components mounted on top of the switch PCB 30. Some embodiments may omit the plastic housing 66.

Fig. 10 is a 3D top view of a power converter module with copper strips and a vertical fin interposer heat sink. The top of the switch PCB 30 faces upward. The interposer heat sinks 22, 24, 25 prevent the switch PCB 30 from contacting the system PCB 10, and in this 3D top view the system PCB 10 is located below the interposer heat sinks 22, 24, 25. The interposer PCB 50 is soldered to the bottom of the switch PCB 30, hidden. Pins 88 for control signals extend downwardly from interposer PCB 50 to the same height as copper bars 62.

In this embodiment, the fins 72 of the interposer heat sinks 22, 24, 25 are vertical, rather than horizontal. The horizontal shelf 78 has vertical fins 72 extending upwardly therefrom, and the interposer portion 76 is located between the switch PCB 30 and the system PCB 10 (not shown), with current being transferred from the switch PCB 30 to the copper bars 62 and then to the system PCB 10. A plastic housing 65 covers the top of the switch PCB 30 and the IC packages 32, 34 and other components mounted on top of the switch PCB 30.

Fig. 11 is a 3D top view of an asymmetric power converter module with interposer PCBs placed in one corner with copper strips on the interposer heat spreader. The top of the switch PCB 30 faces upward. The interposer heat sinks 22, 25 do not have the interposer PCB 50 therebetween, but rather leave a void as a separation between the interposer heat sinks 22, 25.

In this variation, the interposer PCB 50 is not placed between the interposer heat sinks 22, 25. Instead, the interposer PCB 50 is placed in a corner of the module in a cutout recess at one end of the interposer side heat sink 24. Pins 88 extend downwardly from interposer PCB 50 and in this asymmetric placement may be easier to insert into holes in system PCB 10. Due to this placement of interposer PCB 50, the width of copper strips 62 for interposer heat spreader 24 is reduced.

Fig. 12 is a 3D bottom view of a power converter module with copper strips and a vertical fin interposer heat sink. The bottom of the switch PCB 30 faces upward. The interposer heat sinks 22, 24, 25 prevent the switch PCB 30 from touching the system PCB 10, and in this 3D bottom view the system PCB 10 will be placed over the interposer heat sinks 22, 24, 25.

The interposer heat sink 22 may be grounded, while the interposer heat sink 24 connects the power input vin+ from the system PCB 10 to the switch PCB 30. A third interposer heat sink 25 may be used to connect the power output vout+ between the system PCB 10 and the switch PCB 30.

In this variation, the interposer PCB 50 is mounted in the gap or cavity between the interposer heat sinks 22, 25. The interposer PCB 50 may carry a plurality of control signals such as G1, G2, G3, G4 (fig. 1) and status or other signals. The array of pins 88 at the bottom of interposer PCB 50 are inserted into the array of holes of system PCB 10 and soldered to metal pads (not shown) around the holes of PCB 10. In this 3D view, the bottoms of pins 88 and copper bars 62 are facing upward, flush, so that all pins 88 and copper bars 62 can be inserted into holes in the top surface of system PCB 10. Alternatively, the pin 88 may be longer than the copper bar 62, such that the pin 88 may be inserted into the hole and then the copper bar 62 may be inserted into the larger hole 65.

A plastic housing 66 covers the top of the switch PCB 30 between the interposer heat sinks 22, 24, 25. The plastic housing 66 protects the IC packages 32, 34 and other components. The fins of the interposer heat sinks 22, 24, 25 are vertical, as shown in fig. 10, rather than horizontal.

Fig. 13 is a 3D bottom view of a power converter module with copper bars on one side and pins on the interposer PCB side. The bottom of the switch PCB 30 faces upward. The interposer heat sinks 22, 25 each have a row of pins 82 instead of copper bars 62. The interposer PCB 50 is located between the interposer heat sinks 22, 25. Because interposer PCB 50 has pins 88, replacing copper bar 62 with pins 82 allows the left side of the entire module to be inserted into the holes of system PCB 10 before the larger copper bar 62 on the right side of the module is inserted into the slot (holes 65) of system PCB 10. Thus, by using pins 82 around pins 88 extending from interposer PCB 50, assembly may be facilitated.

Fig. 14 is a 3D bottom view of a power converter module in which interposer heat sinks employ pins instead of copper bars. The bottom of the switch PCB 30 faces upward. The interposer heat sinks 22, 24, 25 each have a row of pins 82 instead of copper bars 62. The interposer PCB 50 between the interposer heat sinks 22, 25 also has pins 88. The use of pins alone may facilitate insertion of pins into holes in the system PCB 10 as compared to the use of copper bars 62.

[ alternative embodiment ]

The inventors have complemented several other embodiments. For example, thermal vias may be added to the switch PCB 30 or the system PCB 10 to facilitate heat transfer through the PCB. An array of thermal vias may be used. Other heat transfer and dissipation techniques may be used in conjunction with the power converter module with the interposer heat sink 22. The transistor or inductor may be soldered directly to the heat sink in the recess of the switch PCB 30.

The copper bar 62 may be rectangular in shape as shown, and may vary in height, width, and length, as well as other shapes or features. Unlike only one copper bar 62 per interposer heatsink 22, 24, 25, each interposer heatsink 22 may have two or more copper bars 62, which may be smaller in size than if there were only one copper bar 62 per heatsink. Copper strips or pin arrays, or various combinations, may be used. The copper bar 62 may be pure copper, may be added with various elements or compounds, and may be made of various copper alloys. The copper strips 62 may be the same material as the interposer heatsink 22 or may have a different composition. The pins 82, 88 may also be copper or other metal and have different shapes and lengths. Holes, cutouts, grooves, or other features may be added to the interposer heat sinks 22, 24, 25 for better fixation of copper bars or for other purposes. Rather than inserting the copper bar 62 into the hole 65 of the system PCB 10, a socket or other securing device is attached to the top surface of the system PCB 10 and then inserting the bottom of the copper bar 62 into the hole of the socket. Thus, the holes 65 may be holes in slots attached to the PCB board, rather than holes within the PCB board itself. The socket may be soldered to the system PCB to provide a soldered connection with the copper bar.

There may be many control signals, each with its own interconnect 48, 58, 18. Status or other signals may be included in these control signals. When separate grounds are used for input and output, the second interposer heatsink 22 may be used for the second ground. The interposer heat spreader 22 may be divided into 2 heat spreaders, such as the interposer heat spreaders 24, 25 shown. The interposer heatsink 25 connected to the power supply output vout+ may instead be connected to the left side of the inductor 314 (fig. 1), while another interposer heatsink may be connected to the left side of the inductor 312. This will provide better heat transfer because the thermal path does not pass through the inductors 312, 314, but rather the interposer heatsink is directly connected to the outputs of the transistors 302-308. Additional heat sinks may also be added. The additional heat sink may be electrically isolated or connected to other heat sinks.

Some power converters may have only transistors 302, 304 and no transistors 306, 308. Other variations of the power converter circuit are possible. Each transistor 302-308 may be packaged in a separate IC package 32, 34, or multiple transistors may be packaged in a single IC package 32. FIG. 1 is merely a topology; other types of power converter topologies may be substituted. Depending on the system requirements, a heat sink may be connected to the end node of the inductor or transistor to obtain additional thermal paths.

Other sensing and control components may also be added to the switch PCB 30, for example to measure the current or voltage of the power control system, thereby adjusting the duty cycle of G1-G4.

More complex interposer heat sinks 22, 24, 25 may be used, for example, having various complex shapes. Either horizontal or vertical fins may be used. The copper bar 62 may also have various sizes and shapes. Solder bumps or pads may be added to interposer heatsink 22 to make solder connections with switch PCB 30 on top and copper bars 62 on the bottom of interposer portion 76. Screw and bolt holes may be added to the interposer heat sinks 22, 24, 25 and the switch PCB 30. The cavity 26 may have various shapes and sizes. The interposer heat sinks 22, 24, 25 are preferably each of an integrally formed construction, with the fins and brackets formed as one piece of metal for better heat conduction. For example, the horizontal support 78, the vertical fins 72, and the interposer portion 76 may all be formed of the same copper metal, which may promote better heat conduction from the switch PCB 30. If the fin and interposer portions 76 are separate pieces of copper from each other, they may be secured together by screws or other fasteners, but the heat transfer performance is poorer and therefore less than if the fin and interposer portions were a single integrated metal block. Likewise, the copper strips 62 may be integrally formed with the interposer heatsink 22, or may be bonded by welding, sintering, or other methods.

The interposer PCB 50 may be placed in a variety of locations, such as in a recess of the interposer heat sink 24 (fig. 11). This recess of the interposer heat spreader 24 need not be at the corners, but rather, as shown in fig. 11, only 2 sides may be surrounded by the interposer heat spreader 24, with 3 sides all surrounded by the interposer heat spreader 24. The interposer PCB 50 may also be placed between the interposer heat sinks 22, 25 as shown in fig. 9-10, but may also be located in notches at the corners of the interposer heat sink 22 or the interposer heat sink 25 or the interposer heat sink 24. The interposer PCB 50 may also be placed between the interposer heat spreader 22 and the interposer heat spreader 24, intermediate the switch PCBs 30, as shown in fig. 2-7. Many other placement of the interposer PCB 50 are possible. Furthermore, the interposer PCB 50 may be more than one. The interposer PCB 50 may be placed asymmetrically or symmetrically.

The plastic housing 66 is optional and may be omitted or replaced by other protective methods. Since the interposer heat sink 24 is connected to the voltage input vin+, there is a risk of a short circuit if someone touches the interposer heat sink 24 when the power converter is powered on. Larger chassis and housings may be used for the system PCB 10 to prevent human access to the interposer heat sink 24. Good system design ensures that no shorting of interposer heat spreader 24 occurs.

The inductors 312, 314 may be mounted to the switch PCB 30 or may be separately located outside the switch PCB 30, with wires or cables connecting the inductors to the switch PCB 30. The larger load capacitor of capacitor 330 may also be placed outside of switch PCB 30 and connected by a cable.

Because the ground, power input and power output pass through the interposer heat sinks 22, 24, 25, respectively, the ground and power need not pass through the interposer PCB 50. However, power and ground may still be connected in parallel with the path through the interposer heat sinks 22, 24, 25 through the interposer PCB 50.

The background section of the present invention may contain background information about the problem or environment of the present invention rather than the prior art describing others. Accordingly, the inclusion of materials in the background section is not an admission of the prior art by the applicant.

Any of the methods or processes described herein are machine-implemented or computer-implemented and are intended to be performed by a machine, computer, or other device, and are not intended to be performed by a human alone without machine assistance. The tangible results produced may include reports or other machine-generated displays on display devices such as computer displays, projection devices, audio generation devices, and related media devices, and may include hard copy printouts that are also machine-generated. Computer control of other machines is another tangible outcome.

Any of the advantages and benefits described are not necessarily applicable to all embodiments of the invention. When the term "means" appears in a claim element, the applicant intends that the claim element falls under the 35USC section 112, clause 6 specification. Typically, the word "device" is preceded by a tag of one or more words. One or more words preceding the word "means" is a label for ease of reference to claim elements and not for express structural limitations. Such means-plus-function claims are intended to cover not only the structures described herein for performing the function and their structural equivalents, but also equivalent structures. For example, although a nail and a screw have different constructions, they are equivalent structures in that they both perform a fastening function. The claims that do not use the term "means" do not fall under the 35USC section 112, clause 6. The signals are typically electronic signals, but may also be optical signals, for example, which may be transmitted over fiber optic lines.

The foregoing description of the embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto.

Claims (20)

1. A thermal enhancement module, comprising:

a switch Printed Circuit Board (PCB);

a system PCB;

a semiconductor package having terminals soldered to pads on a top surface of the switch PCB;

a first interposer heat spreader including cooling fins for dissipating heat and a first interposer portion having a top surface soldered to a metal pad of the switch PCB lower surface, the first interposer portion having a bottom surface;

a first conductive strip attached to a bottom surface of the first interposer heat spreader, wherein the

The bottom of the first conducting strip is inserted into a first hole of the system PCB and is used for welding the first conducting strip to a metal wire on the system PCB;

a second interposer heat spreader including cooling fins for dissipating heat and a second interposer portion having a top surface soldered to the metal pads of the switch PCB lower surface, the second interposer portion having a bottom surface;

a second conductive strip connected to a bottom surface of the second interposer heatsink, wherein a bottom of the second conductive strip is inserted into a second hole of the system PCB for soldering the second conductive strip to a metal trace on the system PCB;

An interposer PCB having top pads of a top surface thereof soldered to metal pads of a lower surface of the switch PCB and bottom pads of a bottom surface thereof connected to metallized pads of a top surface of the system PCB for soldering the bottom pads to the system PCB;

a first thermal and electrical path of metal from a first terminal of the semiconductor package, through metal traces and vias of the switch PCB, through a solder joint between the switch PCB and the first interposer heatsink, and through the first conductive strip to the system PCB; and

a second thermal and electrical path of metal from a second terminal of the semiconductor package, through metal traces and vias of the switch PCB, through a solder joint between the switch PCB and the second interposer heat sink, and through the second conductive strip between the second interposer heat sink and the system PCB to the system PCB.

2. A thermally enhanced power converter module comprising:

a switch Printed Circuit Board (PCB) having a plurality of layers of patterned metal;

a semiconductor package mounted on a top surface of the switch PCB;

a pull-down transistor within the semiconductor package, a gate of the pull-down transistor being controlled by a first control terminal of the semiconductor package, a source of the pull-down transistor being connected to a ground terminal of the semiconductor package;

A pull-up transistor within the semiconductor package, a gate of the pull-up transistor being controlled by a second control terminal of the semiconductor package, a source or drain of the pull-up transistor being connected to a power terminal of the semiconductor package;

a metal pad on a lower surface of the switch PCB, the metal pad including a ground pad, a power pad, a first control pad, and a second control pad;

a ground interconnect in the multi-layered patterned metal in the switch PCB electrically and thermally connecting a ground terminal of the semiconductor package soldered on the top surface of the switch PCB with the ground pad on the lower surface;

a power interconnect in the multi-layered patterned metal in the switch PCB, the power interconnect electrically and thermally connecting a power terminal of the semiconductor package soldered on a top surface of the switch PCB with the power pad on the lower surface;

a first control interconnect in the multi-layer patterned metal in the switch PCB, the first control interconnect electrically connecting a first control terminal of the semiconductor package soldered on a top surface of the switch PCB to the first control pad on the lower surface;

A second control interconnect in the multi-layer patterned metal in the switch PCB, the second control interconnect electrically connecting a second control terminal of the semiconductor package soldered on the switch PCB top surface to the second control pad on the lower surface;

a first interposer heat spreader including a first cooling fin and a first interposer portion, a top surface of the first interposer portion being soldered to the ground pad of the switch PCB, the first interposer portion having a bottom surface;

a first conductive strip attached to a bottom surface of the first interposer heatsink, wherein a bottom of the first conductive strip is inserted into a first hole of the system PCB to solder the first conductive strip to a grounded metal pad near the first hole of the system PCB;

wherein the first interposer heatsink conducts ground current from the switch PCB to the first conductive strip, which in turn conducts ground current to the system PCB and dissipates heat generated by the pull-down transistor using the first cooling fin;

a second interposer heat spreader including a second cooling fin and a second interposer portion, a top surface of the second interposer portion being soldered to the power pads of the switch PCB, the second interposer portion having a bottom surface;

A second conductive strip attached to a bottom surface of the second interposer heatsink, wherein a bottom of the second conductive strip is inserted into a second hole of the system PCB to solder the second conductive strip onto a power metal pad adjacent to the second hole of the system PCB;

the second interposer heat sink conducts power supply current from the system PCB to the second conductive strip, the second conductive strip conducts power supply current to the switch PCB again, and the second cooling fin is used for radiating heat generated by the pull-up transistor;

an interposer PCB having multiple layers of patterned metal, the interposer PCB having a top interposer first control pad soldered to the first control pad on the switch PCB and a top interposer second control pad soldered to the second control pad on the switch PCB on a top surface thereof;

the bottom surface of the interposer PCB is also provided with a bottom interposer first control pad and a bottom interposer second control pad; and

an interposer first control interconnect in the multi-layer patterned metal in the interposer PCB electrically connects the top interposer first control pad on the top surface to the bottom interposer first control pad on the bottom surface.

3. The thermally enhanced power converter module of claim 2, further comprising:

a first pin extending downward from the bottom interposer first control pad on the interposer PCB bottom surface;

a first control hole in the system PCB for receiving a bottom of the first pin and connecting the first pin to a first control metal on the system PCB;

a second pin extending downward from the bottom interposer second control pad on the interposer PCB bottom surface;

a second control hole in the system PCB for receiving a bottom portion of the second pin and connecting the second pin to a second control metal on the system PCB.

4. The thermally enhanced power converter module of claim 2 wherein the bottom interposer first control pad is for soldering to a first control metal pad on the system PCB top surface; wherein the bottom interposer second control pad is for soldering to a second control metal pad on the top surface of the system PCB;

wherein a bottom surface of the interposer PCB is flush with a bottom surface of the first interposer portion of the first interposer heat spreader and is also flush with a bottom surface of the second interposer portion of the second interposer heat spreader;

Wherein the top surface of the system PCB is flush mounted and soldered to pads on the bottom surface of the interposer PCB, the bottom surface of the first interposer heat spreader, and the bottom surface of the second interposer heat spreader.

5. The thermally enhanced power converter module of claim 4 wherein the switch PCB has a first edge and a counter edge opposite the first edge;

wherein the first interposer heatsink is mounted along the first edge, with the first cooling fins extending beyond the first edge;

wherein the second interposer heatsink is mounted along the opposing edge, with the second cooling fins extending beyond the opposing edge.

6. The thermally enhanced power conversion module of claim 4, wherein the first conductive strip and the second conductive strip are copper strips.

7. The thermally enhanced power conversion module of claim 4, wherein the first conductive strip is attached to the first interposer heat sink by sintering, welding, or brazing;

wherein the second conductive strip is attached to the second interposer heatsink by sintering, welding, or brazing.

8. The thermally enhanced power converter module of claim 4 wherein the first conductive strip is integrally formed with the first interposer heatsink, wherein the first conductive strip is part of a downward extension of the first interposer heatsink;

wherein the second conductive strip is integrally formed with the second interposer heatsink, wherein the second conductive strip is part of the second interposer heatsink that extends downward.

9. The thermally enhanced power converter module of claim 4 wherein the first conductive strip is a first array of pins extending downwardly from the first interposer heat sink;

wherein the first hole is a first hole array on the system PCB that receives a bottom of the first pin array;

wherein the second conductive strip is a second array of pins extending downward from the second interposer heatsink;

wherein the second hole is a second hole array on the system PCB that receives a bottom of the second pin array.

10. The thermally enhanced power converter module of claim 4, further comprising:

a power output interconnect in the multi-layer patterned metal of the switch PCB, the power output interconnect electrically and thermally connecting a power output node of the switch PCB to a power output pad on a lower surface of the switch PCB;

The pull-up transistor and the pull-down transistor perform current switching according to the first control terminal and the second control terminal to generate a power output on the power output node; a third interposer heat spreader including a third cooling fin and a third interposer portion, a top surface of the third interposer portion being soldered to the power output pad of the switch PCB, the third interposer portion having a bottom surface;

a third conductive strip attached to a bottom surface of the third interposer heatsink, wherein a bottom of the third conductive strip is inserted into a third hole of the system PCB to solder the third conductive strip to a power output metal pad adjacent the third hole of the system PCB;

the third interposer radiator conducts power supply output current from the switch PCB to the system PCB through the third conducting strip, and radiates heat generated by the pull-up transistor and the pull-down transistor through the third cooling fin.

11. The thermally enhanced power converter module of claim 10 wherein the second interposer heat sink and the third interposer heat sink are mounted along a first edge of the switch PCB;

Wherein the first interposer heatsink is mounted along opposing edges of the switch PCB, the opposing edges being opposite the first edge.

12. The thermally enhanced power converter module of claim 4 wherein the first cooling fin and the second cooling fin are parallel to a plane of the switch PCB.

13. The thermally enhanced power converter module of claim 4 wherein the first cooling fin and the second cooling fin are perpendicular to a plane of the switch PCB.

14. A power converter module, comprising:

a switch Printed Circuit Board (PCB);

a ground trace formed in the switch PCB, the ground trace having a first upper pad and a first lower pad connected together by a metal trace and a via in the switch PCB; a power input trace formed in the switch PCB, the power input trace having a second upper pad and a second lower pad connected together by a metal trace and a via in the switch PCB;

a first power transistor in a package mounted on the switch PCB, a ground terminal of the first power transistor being electrically connected by a first package lead soldered to the first upper pad;

A second power transistor in a package mounted on the switch PCB, a power input terminal of the second power transistor being electrically connected through a second package lead soldered to the second upper pad;

a first interposer heat spreader including cooling fins and a first interposer portion;

a second interposer heat sink including cooling fins and a second interposer portion;

wherein the cooling fin is located outside the perimeter of the switch PCB;

wherein the first interposer portion and the second interposer portion are at least partially within a perimeter of the switch PCB;

wherein the first interposer portion has a top surface and a bottom surface, the top surface of which is soldered to the first lower pad;

a first copper bar extending downward from a bottom surface of a first interposer portion of the first interposer heat spreader, the first copper bar being inserted into a hole of the system PCB to be soldered onto a metal trace around the hole of the system PCB;

wherein the second interposer portion has a top surface and a bottom surface, the top surface of which is soldered to the second lower pad;

a second copper bar extending downward from a bottom surface of a second interposer portion of the second interposer heatsink, the second copper bar being inserted into a hole of the system PCB to be soldered onto a metal trace around the hole of the system PCB;

An interposer PCB; and

control wires formed in the interposer PCB, each control wire having a control upper pad and a control lower pad, which are connected together by metal wires and vias in the interposer PCB;

wherein the under-control pads are for soldering to pads of the system PCB;

wherein the control upper pads on the upper surface of the interposer PCB are soldered to lower pads on the lower surface of the switch PCB.

15. The power converter module of claim 14 further comprising a control pin extending downward from the under control pad, wherein the control pin is inserted into a hole of the system PCB.

16. The power converter module of claim 14 wherein a perimeter of the system PCB is greater than a perimeter of the switch PCB.

17. The power converter module of claim 14, further comprising:

a power output trace formed in the switch PCB, the power output trace having a third upper pad and a third lower pad connected together by a metal trace and a via in the switch PCB;

a third interposer heat sink including cooling fins and a third interposer portion;

Wherein the third interposer portion has a top surface and a bottom surface, the top surface of which is soldered to the third lower pad;

and a third copper bar extending downward from a bottom surface of the third interposer portion of the third interposer heat spreader, the third copper bar being inserted into a hole of the system PCB to be soldered to a third upper pad through the hole of the system PCB.

18. The power converter module of claim 17 wherein the third upper pad is connected to a power output.

19. The power converter module of claim 18, further comprising:

an inductor having a first terminal connected to the outputs of the first and second power transistors and a second terminal driving the power supply output.

20. The power converter module of claim 14 wherein the first power transistor is located in a first package and the second power transistor is located in a second package.