Patent Description:
As is known, electronic power components and signal processing circuitry are often integrated into an integrated circuit (IC), power IC, or power module, for use in a variety of applications. For example, power transistors, such as Metal Oxide Semiconductor Field Effect Transistors (MOSFETs), are often interconnected to form of a bridge circuit, such as an H-bridge or half of an H-bridge, for motor applications. One example application is in an automotive power steering module. Integrating power components into an IC or module can present challenges including dissipating heat generated by the power components and providing complex circuitry while at the same time reducing the overall package size. <CIT> describes that a device may include a carrier, a semiconductor chip arranged over a first surface of the carrier, and an encapsulation body comprising six side surfaces and encapsulating the semiconductor chip. A second surface of the carrier opposite to the first surface of the carrier is exposed from the encapsulation body. The device may further include electrical contact elements electrically coupled to the semiconductor chip and protruding out of the encapsulation body exclusively through two opposing side surfaces of the encapsulation body which have the smallest surface areas of all the side surfaces of the encapsulation body, and an electrically insulating layer arranged over the exposed second surface of the carrier. <CIT> describes a semiconductor chip package includes a semiconductor chip disposed over a main surface of a carrier. <CIT> describes a semiconductor chip package includes a semiconductor chip, an encapsulation body encapsulating the semiconductor chip, a chip pad, and electrical contact elements connected with the semiconductor chip and extending outwardly. <CIT> describes a semiconductor device that includes a printed wiring board; a first semiconductor module including a first package body and a first heat radiation surface on one surface of the first package body, another surface of the first package body, facing the first heat radiation surface, faces one face of the printed wiring board; a first heat radiator on the first heat radiation surface; a second semiconductor module including a second package body and a second heat radiation surface on one surface of the second package body, another surface of the second package body, facing the second heat radiation surface, faces another face of the printed wiring board; and a second heat radiator provided on the second heat radiation surface. <CIT> B <NUM> describes an intelligent power module (IPM) that has first, second, third and fourth die paddles, a first, second, third, fourth, fifth and sixth transistors, a tie bar, a low voltage IC, a high voltage IC, a first, second and third boost diodes, a plurality of leads and a molding encapsulation.

According to the disclosure, there is provided a power integrated circuit (IC) as defined in claim <NUM>.

Features may include one or more of the following individually or in combination with other features. The lead frame can further include a dummy lead and the paddle can be attached to one or more of the signal lead, the power lead, and the dummy lead. The paddle can be only attached to the second portion of the power lead. The mold material has a first surface, a second surface parallel to the first surface, and a side surface extending between the first surface and the second surface and the first and second portions of the power lead can meet at a junction between a first portion of the mold material and a second portion of the mold material positioned along the side surface. In embodiments, the junction is located at a height of approximately one-fifth to one-third of a height of the side surface of the mold material. The junction can be located at a height of approximately one-fourth of a height of the side surface of the mold material. At least one of the signal lead and the power lead can have a recessed portion enclosed by the mold material and configured to lock the at least one lead into a fixed position relative to the exposed surface of the mold material. In embodiments, the recessed portion of the at least one lead can be formed by etching, stamping, coining, or laser cutting. The exposed surface of the paddle is configured to couple to a heatsink configured to extend beyond a surface of the mold material. At least one passive component can be coupled between at least two signal leads and enclosed by the mold material. The passive component comprises one or more of a resistor, a capacitor, an inductor, a thermistor, or a diode. The lead frame can include a plurality of signal leads, a plurality of power leads, and a plurality of paddles each attached to a respective one of the plurality of power leads or the plurality of signal leads, wherein the electrical component comprises a plurality of Field Effect Transistors (FETs) each supported by a respective paddle and electrically coupled to form a half H-bridge. At least one of the FETs can include a source terminal located external to the mold material and accessible at one of the plurality of signal leads. A wire bond can extend from the one of the signal leads to the one of the paddles by which the at least one FET is supported. In embodiments, a shunt can be coupled between the signal lead, the power lead, and the paddle. In embodiments, a jumper can be coupled in series with the power lead. The signal lead can have a first width at an end configured for external coupling and a second width larger than the first width at a bend.

Features may include one or more of the following individually or in combination with other features. The junction can be located at a height of approximately one-fifth to one-third of a height of the side surface of the mold material and in some embodiments is located at a height of approximately one-fourth of the height of the side surface of the mold material. The exposed surface of the paddle can be configured to attach to a heatsink configured to extend beyond the second surface of the mold material.

The foregoing features may be more fully understood from the following description of the drawings. The drawings aid in explaining and understanding the disclosed technology. Since it is often impractical or impossible to illustrate and describe every possible embodiment, the provided figures depict one or more illustrative embodiments. Accordingly, the figures are not intended to limit the scope of the broad concepts, systems and techniques described herein. Like numbers in the figures denote like elements.

Referring to <FIG>, <FIG>, and <FIG>, a power module <NUM> includes a lead frame <NUM>, one or more electrical components <NUM>, and a mold material <NUM> enclosing the electrical component. The lead frame <NUM> includes at least one signal lead <NUM>, at least one power lead <NUM>, and a paddle <NUM> attached to one or more of the signal lead and the power lead. The electrical component <NUM> is supported by the paddle <NUM>. Internal to the module, electrical connection between leads and electrical components can be made in various ways, such as by clips <NUM> and/or by wire bonds <NUM>.

According to an aspect of the disclosure, the mold material <NUM> is configured to enclose a portion of the lead frame <NUM> and expose a surface <NUM> of the paddle <NUM> such that power lead <NUM> has a first portion <NUM> extending from an edge, or side surface 15a of the mold material outside of the mold material in a first direction (i.e., generally upward in the view of <FIG>) and a second portion <NUM> enclosed by the mold material <NUM> and extending from the edge of the mold material inside the mold material in a second direction (i.e., generally downward the view of <FIG>) to the paddle <NUM>, wherein the second direction is substantially opposite to the first direction. The first and second directions in which the power lead portions <NUM>, <NUM> extend can be substantially vertical with respect to the module <NUM> as illustrated.

Mold material <NUM> can be considered to form a package <NUM> from which the second portion <NUM> of the leads extend to permit electrical connection to other circuits and systems (not shown). Leads <NUM>, <NUM> are surface mount leads configured to be attached to bond pads of a printed circuit board or other suitable substrate in use. It will be appreciated that in use, the module <NUM> can be inverted with respect to the view of <FIG> and mounted with the orientation shown in the view of <FIG>.

The first and second portions <NUM>, <NUM> of the power lead <NUM> can be considered to meet at a junction <NUM>. The exposed paddle surface <NUM> can be referred to as a down set paddle portion or surface. The lead <NUM> has a jog <NUM> between the junction <NUM> and the down set paddle surface <NUM>, as shown. In embodiments, the down set height (jog height) can have a minimum dimension on the order of <NUM>. Mold material <NUM> has a first surface 15b and a second surface 15c parallel to the first surface and side surface 15a extends from the first surface 15b to the second surface 15c.

With this arrangement of the first power lead portion <NUM> extending in a different, substantially vertical direction than the second power lead portion <NUM>, which second power lead portion extends to the down set exposed surface <NUM> of the paddle <NUM>, a heatsink (or other direct contact heat conduction cooling system) <NUM> attached to the exposed paddle surface <NUM> can be larger than otherwise possible. This is because the heatsink <NUM> can extend horizontally beyond the leads <NUM>, <NUM>. This arrangement presents a flat, planar surface for heat sink mounting and thus eliminates restrictions on design of heat sink <NUM> for the module. By contrast, in conventional configurations in which the leads extend outside of the package in the same direction as the down set paddle surface <NUM>, the heatsink is confined to a width generally no larger than the width of the mold material <NUM>.

Referring also to <FIG>, lead frame <NUM> is shown in an orientation inverted with respect to <FIG>. <FIG> shows the module <NUM> overmolded by mold material <NUM>. From these views, down set exposed paddle surface <NUM> can be seen. While lead features are explained in connection with power lead <NUM> to include portions <NUM>, <NUM> meeting at junction <NUM>, paddle <NUM> with down set exposed surface <NUM>, jog <NUM>, etc., it will be appreciated that other leads (other power leads <NUM> and/or signal leads <NUM>) can have similar features. In general, the down set area of some leads includes a paddle <NUM> supporting an electrical component and the down set area of other leads includes a bond pad for internal connection by a clip <NUM> or wire bond <NUM>. Further, the down set area of still other leads may or may not be internally coupled in which case such "dummy leads" can form tie bars as will be explained. In general, as illustrated in <FIG>, the down set area of the leads <NUM>, <NUM> has an exposed surface (collectively labeled <NUM>) in order to facilitate heat removal.

According to a further aspect, at least one signal lead <NUM> and/or power lead <NUM> has a recessed, or thinned portion <NUM> enclosed by the mold material <NUM> and configured to securely lock the respective lead into a fixed position relative to the mold material. The recessed portion <NUM> can be seen at various locations in the view of <FIG> and <FIG> as labelled <NUM>. Recessed portions <NUM> can be formed by various techniques including, but not limited to etching (by either wet etch or dry etch), stamping, coining or laser cutting. Formation of the recessed portion can reduce a thickness of the respective lead by about <NUM>% to <NUM>% and in some embodiments by about <NUM>%. The mold material <NUM> engages the recessed portions <NUM> to form a locking mechanism by which the leads are firmly and fixedly held in place with respect to the mold material. Suitable materials for the mold material <NUM> include thermoset and thermoplastic mold compounds and other commercially available IC mold compounds. In some embodiments, a recessed portion <NUM> is provided for those leads having a down set area with an exposed surface or having a down set paddle with an exposed surface, as shown in <FIG>.

An example circuit formed by the components within the module <NUM> is shown and described in connection with <FIG>. Suffice it to say here that integrated electrical component <NUM> can take various forms, such as a MOSFET. Here, power module <NUM> is shown to include three FETs 65a, 65b, 65c, each supported by a separate substrate or semiconductor die. Thus, power module <NUM> can be referred to interchangeably as a multichip module. It will be appreciated that in some embodiments, more than one component 65a- 65c and in some cases all of the components 65a, 65b, 65c can be supported by a single die. In such embodiments where all of the power components are supported by a single die, the packaged device <NUM> may be referred to as a power IC rather than a power module. However, more generally, power IC and power module are used interchangeably.

Each FET supporting die is in turn attached to a respective paddle <NUM>. Various materials and techniques can be used to attach the die to the paddles, such as by soldering or with the use of an epoxy (either conductive or non-conductive epoxy may be used depending on the need) or an adhesive tape or sintered silver.

In addition to power components 65a-65c, one or more passive components <NUM> can be coupled between at least two signal leads within the package <NUM>. For example, a thermistor <NUM> can be coupled between signal leads <NUM>, as shown. Thermistor <NUM> can monitor the internal temperature of the module and provide temperature information to an external controller. Other example passive components that can be integrated in a similar fashion include but are not limited to a resistor, a capacitor, inductor, a thermistor, or a diode.

Another example electrical component can be provided in the form of a shunt resistor, or simply shunt <NUM>. Shunt <NUM> can be coupled between a power lead <NUM>, a signal lead <NUM>, and a paddle as shown.

Passive component <NUM> and shunt <NUM> can be attached to the down set area of one or more respective leads by soldering to one or more bond pads or with a conductive epoxy process as examples.

In general, signal leads <NUM> differ from power leads <NUM> in the types of signals carried, with power leads generally carrying higher power signals than signal leads. Accordingly, signal leads <NUM> tend to be smaller in width than power leads <NUM> as shown. In embodiments, a width of one or more signal leads <NUM> can be enlarged at a bend area 25a (<FIG>) of the lead in order to improve the lead's coplanarity, and positioning of leads with respect to mold body <NUM>.

According to a further aspect, one or more paddles <NUM> is only attached to the second portion <NUM> of the power lead (i.e., is only attached on one side) such that the paddle is cantilevered as shown. Stated differently, the down set paddle surface <NUM> can be described as a one-sided down set. With this arrangement, stress that could otherwise occur due to the deep down set of the relatively thick lead frame is avoided and the required electrical isolation between the signal leads and power leads is achieved.

As shown in the plan view of <FIG>, package <NUM> has first and second opposing edges 22a, 22b from which the signal leads <NUM> and the power leads <NUM> extend, respectively, and further has third and fourth opposing edges 22c, 22d orthogonal to the first and second opposing edges. According to a further aspect, lead frame <NUM> includes at least one tie bar <NUM> (and here five tie bars 24a, 24b, 24c, 24d, and 24e) extending from one of the first or second opposing edges 22a, 22b, as shown. Tie bars <NUM> hold the molded package during lead forming process.

As is apparent, the bars 24a - 24e may or may not be connected within the module <NUM>. For example, tie bar 24a is electrically connected to electrical component 65a and tie bars 24b and 24c are electrically connected to electrical component 65c. Tie bars 24d and 24e however are not connected within the package <NUM> and thus, can be referred to as dummy leads or dummy tie bars. It will be appreciated that a paddle can be attached to a dummy lead (in addition to or instead of being attached one or more of a signal lead and a power lead).

With this arrangement of having tie bars that extend only from the package edges 22a, 22b from which the leads extend (rather than also or alternatively having tie bars extending from orthogonal packages edges 22c, 22d), the lead frame density is increased. Stated differently, the number of lead frame units that can be provided by the same area of lead frame metal is increased since "side protrusions" are avoided.

The junction <NUM> between the first lead portion <NUM> and the second lead portion <NUM> (i.e., the location at which the lead <NUM> exits the package <NUM> and thus the location where the first lead portion <NUM> starts and second lead portion <NUM> ends or vice versa) can be located at a parting, or separation line <NUM> (<FIG>) in the mold material <NUM> between a first mold portion 16a and a second mold portion 16b. In embodiments, the junction <NUM> is located at a height of approximately one-fifth to one-third of a height of the side surface 15a of the mold material <NUM>, for example, the junction <NUM> can be located at a height of approximately one-fourth of the height of the side surface 15a of the mold material <NUM>.

With this arrangement of the lead <NUM> exiting the package <NUM> at the separation line <NUM> between the first and second mold portions 16a, 16b, a mechanical advantage is achieved. In particular, this design prevents the leads from popping out of the mold material <NUM> and thus, provides an improved strength of retention of the leads relative to the package <NUM>.

During manufacture, lead frame <NUM> is formed from a sheet or strip of metal that is patterned (e.g., stamped, etched) to provide the desired lead frame features (e.g., signal leads, power leads, and paddles) and the desired bends (e.g., jog <NUM>, surface mount pads) in the leads. Generally, a plurality of lead frames like lead frame <NUM> are formed from the same metal sheet and tie bars hold together the lead frame <NUM> with other lead frames (not shown). Once the module <NUM> is formed (i.e., once the electrical component <NUM> is attached, internal electrical connections are made (e.g., by wire bonds or clips), and the device is overmolded by mold material <NUM>), the module <NUM> is separated (i.e., singulated) from other modules (not shown) formed from the same lead frame material. The thickness of the lead frame can vary. In some embodiments the lead frame thickness is on the order of <NUM> mils. As one example, the manufacturing process can include attaching the FET supporting die to respective paddles <NUM>, attaching other components to paddles (e.g., passives <NUM> and shunt <NUM>), solder reflow to attach the die and other components to bond pads on the paddles, attaching clips <NUM>, another solder reflow, and attaching wire bonds <NUM>. The subassembly thus formed can then be overmolded with mold material <NUM>.

Mold material <NUM> can be formed by a single step molding process by which the first mold portion 16a and the second mold portion 16b are formed. For example, the lead frame subassembly (i.e., lead frame <NUM> with components and interconnections in place) can be placed in a hollow space created by joining the two mold cavities (i.e., negatives) that can be held together by means of high-pressure hydraulic systems. Molding compound is then forced through a small opening (i.e., gate) into the cavities by a process such as injection molding, compression molding, transfer molding, or potting. After sufficient time has passed, the mold material is partially cured and then the two mold chases are separated, and the molded body is then "ejected" out of the cavities. The molded body unit is then fully cured at high temperature to improved mechanical strength of the molded body.

Referring also to <FIG>, <FIG>, and <FIG>, a power module <NUM> is shown which is similar to the module <NUM> of <FIG>, <FIG>, and <FIG>. Module <NUM> differs from module <NUM> only in that shunt <NUM> is replaced with a jumper <NUM>. Thus, like elements with respect to <FIG>, <FIG>, and <FIG> are labeled with like reference numbers.

Referring also to <FIG>, a schematic representation of a module <NUM> is shown, which module <NUM> can be the same as or similar to module <NUM> of <FIG> or module <NUM> of <FIG>. In order to provide the module <NUM> of <FIG>, module <NUM> includes a shunt resistor or simply a shunt <NUM> as may be the same as or similar to shunt <NUM> of <FIG>. Shunt <NUM> can be used to sense a load current (i.e., a motor phase current). To this end, leads SUS1 <NUM> and SUS2 <NUM> permit external connection to terminals of the shunt, as shown. In order to provide module <NUM> of <FIG>, module <NUM> includes jumper <NUM> (shown schematically by dotted line <NUM> in <FIG>) instead of the shunt <NUM>. Because modules <NUM> and <NUM> both can be provided by module <NUM> requiring just a simple change of replacing the shunt <NUM> with the jumper <NUM> or vice versa, the manufacturing expense (e.g., tooling costs) of providing modules <NUM> and <NUM> can be reduced.

Module <NUM> includes FETs <NUM>, <NUM>, and <NUM> that can be the same as or similar to FETs 65a, 65b, and 65c, respectively. Electrical connection points between the integrated components and external to the package are shown. FETs <NUM>, <NUM>, and <NUM> are coupled in a half bridge (or half H-bridge) configuration, as shown. Electrical connections to terminals of the FETs include lead VBRG <NUM> coupled to a drain terminal of FET <NUM>, lead GHU <NUM> coupled to a gate terminal of FET <NUM>, lead SU <NUM> coupled to a source terminal of FET <NUM>, lead GLU <NUM> coupled to a gate terminal of FET <NUM>, lead LSSU <NUM> coupled to a source terminal of FET <NUM>, and lead GIU <NUM> coupled to a gate terminal of FET <NUM>. Also shown in the schematic of <FIG> is thermistor <NUM> that can be the same as or similar to thermistor <NUM> (<FIG>, <FIG>). FET <NUM> can be coupled to a load <NUM> as can take various forms depending on the application. In some embodiments, the load <NUM> is a motor winding. Leads VBRG <NUM>, PHU <NUM>, and PGND <NUM> can be power leads <NUM> and the remaining leads can be signal leads.

According to an aspect of the disclosure, at least one FET has an additional connection to its source terminal for diagnostic purposes. In particular, generally FETs require only one external connection to a gate terminal to operate. Here, FET <NUM> (i.e., FET 65b in <FIG>, <FIG>) has an additional external connection to its source terminal provided by lead LSSU <NUM>. Lead LSSU <NUM> is coupled to a source bond pad (labelled <NUM> in <FIG>, <FIG>, <FIG>, <FIG>) on the FET <NUM> by a wire bond 70d. This arrangement is advantageous for testing purposes, such as in order to meet the high safety standards for certain types of applications such as Automotive Safety Integrity Level (ASIL) requirements. Without this extra source bond pad <NUM>, in order to electrically connect to the source of FET <NUM>, wire would have been bonded to a copper clip <NUM> which would require additional plating thus increasing design and production costs.

Internal to the module, electrical connection between leads and internal components can be made in various ways, such as by clips <NUM> or by wire bonds <NUM>. For example, connection between a transistor gate terminal and a signal lead can be made by wire bonds, as labelled wire bonds 70a, 70b, and 70c in <FIG> and <FIG> for FETs 65a, 65b, and 65c, respectively. Further, internal electrical connection to a source terminal (e.g., source terminal of transistor <NUM>) can be made by a wire bond labeled 70d coupled to source bond pad <NUM> as shown in <FIG>, <FIG>.

Claim 1:
A power integrated circuit (IC) (<NUM>) comprising:
a lead frame (<NUM>) comprising a signal lead (<NUM>), a power lead (<NUM>), a tie bar (24a, 24b, 24c, 24d, 24e), and a paddle (<NUM>), wherein the paddle is attached to one or more of the signal lead and the power lead;
an electrical component (<NUM>) supported by the paddle; and
a mold material (<NUM>) configured to enclose a portion of the lead frame and expose a surface of the paddle, wherein the power lead has a first portion extending from an edge of the mold material outside of the mold material in a first direction and a second portion enclosed by the mold material and extending from the edge of the mold material inside the mold material in a second direction to the paddle, wherein the second direction is substantially opposite to the first direction; and
wherein the mold material (<NUM>) forms an IC package having first and second opposing edges (22a, 22b) from which the signal lead (<NUM>) and the power lead (<NUM>) extend and having third and fourth opposing edges (22c, 22d) orthogonal to the first and second opposing edges (22a, 22b), and wherein the tie bar extends from one of the first or second opposing edges (22a, 22b) and does not extend from the third or fourth opposing edges (22c, 22d).