This application claims the benefit under 35 U.S.C. § 119(a) of European Application No. 21162409.3 filed Mar. 12, 2021, the contents of which are incorporated by reference herein in their entirety.
The present disclosure relates to a lead-frame based half-bridge package. The present disclosure is particularly useful in power electronics applications, such as DC-DC converters and motor controllers.
A half-bridge circuit is an often used building block in various applications of power electronics, such as DC-DC converters or (H-bridge) motor controllers. For example, in a DC-DC converter, a half-bridge circuit may be used to control an output voltage of a transformer included in the DC-DC converter using two input switches included in the half-bridge circuit.
An example of a half-bridge circuit is shown in
First transistor T1 has a gate terminal G1, a source terminal S1 and a drain terminal D1. Similarly, second transistor T2 has a gate terminal G2, a source terminal S2 and a drain terminal D2. In the half-bridge configuration, drain terminal D2 of second transistor T2 is electrically connected to source terminal S1 of first transistor T1. Gate terminals G1 and G2 may for example be referred to as (control) input terminals of the half-bridge circuit, while drain terminal D2 (and source terminal S1) forms an output terminal of the half-bridge circuit.
The half-bridge circuit of
Examples of packaged half-bridge circuits known in the art are shown in
Package 20 of
Similarly, package 20 further comprises a second drain contact 22B (e.g., another die pad) arranged next to first drain contact 22A and on which a second semiconductor die 21B is arranged. Second semiconductor die 21B has second transistor T2 integrated thereon that comprises drain terminal D2 (not shown) arranged at a bottom surface of second semiconductor die 21B, and gate and source terminal G2, S2 arranged at a top surface of second semiconductor die 21B. Furthermore, a second gate contact 23B and a second source contact 24B are provided on top of second semiconductor die 21B.
Package 20 further comprises a bridge connection 25 extending from first source contact 24A to a region on top of second drain contact 22B, thereby electrically connecting second drain contact 22B and first source contact 24A. Through bridge connection 25, source terminal S1 of first transistor T1 is electrically connected to drain terminal D2 of second transistor T2.
Semiconductor dies 21A and 21B, drain contacts 22A and 22B, gate contacts 23A and 23B, source contacts 24A and 24B, and bridge connection 25 are all encapsulated by a solidified moulding compound 26. Furthermore, each contact has one or more leads extending therefrom through and out of solidified moulding compound 26 to provide external access to corresponding terminals of first and second transistor T1, T2. Each contact may be integrally connected to its corresponding lead(s).
Package 40 shown in
A problem associated with the packaged half-bridge circuits known in the art is that the interconnection between drain terminal D2 of second transistor T2 and source terminal S1 of first transistor T1 is typically provided either externally to the package by electrically connecting the corresponding leads, or internally using a bridge connection. Said interconnection introduces an unwanted additional resistance and inductance to the half-bridge circuit that, in turn, degrade the performance of the circuit. Using a bridge connection may also substantially complicate the alignment of various elements of the package during the manufacturing process.
Furthermore, for power applications, a relatively low on-resistance of first transistor T1 and second transistor T2 is preferred. However, the on-resistance is strongly dependent on the die size, which in turn is limited by the maximum footprint of the package. In other words, for a given package footprint, the on-resistance performance of first transistor T1 and second transistor T2 is generally limited to the maximum corresponding die size in said package.
It is an object of the present disclosure to provide a packaged half-bridge circuit for which the abovementioned problems do not occur, or hardly so.
This object is achieved with the lead-frame based half-bridge package according to claim 1. The package comprises: a die pad having a first surface and a second surface; a first semiconductor die arranged on the first surface of the die pad, the first semiconductor die having a first transistor integrated thereon that comprises a first terminal and a second terminal arranged at a first surface of the first semiconductor die, and a third terminal arranged at a second surface of the first semiconductor die, wherein the die pad is electrically connected to the drain terminal; a second semiconductor die having a second transistor integrated thereon that comprises a first terminal and a second terminal arranged at a first surface of the second semiconductor die, and a third terminal arranged at a second surface of the second semiconductor die, wherein the second surface of the second semiconductor die is arranged to face the first surface of the first semiconductor die; a first contact element arranged on the first surface of the first semiconductor die and being electrically connected to the first terminal of the first transistor; a second contact element arranged in between the first and second semiconductor die and being electrically connected to the second terminal of the first transistor and the third terminal of the second transistor; a third contact element arranged on the first surface of the second semiconductor die and being electrically connected to the first terminal of the second transistor; a fourth contact element arranged on the first surface of the second semiconductor die and being electrically connected to the second terminal of the second transistor; and a solidified moulding compound encapsulating the first semiconductor die, the second semiconductor die and the first through fourth contact element. Each of the first through fourth contact element comprises one or more leads that extend from their respective contact element through and out of a side of the solidified moulding compound to provide external access to said contact element.
The second contact element, according to the present disclosure, is simultaneously used as a ‘die pad’ for the second semiconductor die, and a clip for the source terminal of the first semiconductor die, thereby eliminating the need for a bridge connection. Consequently, by stacking the first and second semiconductor die and interconnecting the first and second transistor using a shared second contact element as described above, a parasitic resistance and inductance associated with an interconnection between the first and second transistor is significantly reduced. Furthermore, the stacked configuration described above effectively reduces the package footprint, or enables increasing the size of both the first and second semiconductor die, thereby improving the on-resistance performance of the first and second transistor for a particular package footprint.
The solidified moulding compound may partially encapsulate the die pad. At least part of the second surface of the die pad may be exposed through the solidified moulding compound to provide external access to the third terminal of the first transistor. Alternatively, the package may further comprise one or more leads extending from the die pad, through and out of the solidified moulding compound to provide external access to said die pad.
The lead(s) of the first and second contact element may extend parallel to each other. For example, first and second contact element may have originated from different parts of a same clip comprised in a lead frame. Additionally or alternatively, the lead(s) of the third and fourth contact element may extend parallel to each other. For example, the third and fourth contact element may have originated from different parts of a same clip comprised in a lead frame.
At least one but preferably all of the first through fourth contact element may comprise a central planar part that is connected to one or more corresponding terminals of the first and second transistor and from which the one or more respective leads extend. For example, the clips and leads comprised in the lead frame may be substantially planar, thereby greatly simplifying the manufacturing process of the package, such as steps of aligning contact elements with respective semiconductor dies.
The leads corresponding to the first through fourth contact element may be gull-wing shaped such that an end thereof is positioned on a plane that coincides with a plane on which a bottom surface of the moulding compound and/or the second surface of the die pad is arranged.
The first transistor and the second transistor may each comprise a field-effect transistor (FET), wherein the first terminal is a gate terminal, wherein the second terminal is a source terminal, and wherein the third terminal is a drain terminal. Alternatively, the first transistor and the second transistor may each comprise a bipolar junction transistor (BJT), wherein the first terminal is a base terminal, wherein the second terminal is an emitter terminal, and wherein the third terminal is a collector terminal. In yet another alternative, one of the first transistor and the second transistor may be an FET, and another of the first transistor and the second transistor may be a BJT.
The first through fourth contact element may be attached and electrically connected to corresponding surfaces of the first and second semiconductor die using a conductive layer. For example, the conductive layer may comprise one of aluminium, copper, gold, silver and tin.
The fourth contact element may be at least partially exposed to an outside for allowing a heat sink or heat spreader to be connected to a surface of said fourth contact element.
The first transistor may be substantially identical to the second transistor. In some embodiments, the first semiconductor may be substantially identical to the second semiconductor die.
The first and/or second terminal of the first transistor may be arranged at opposing ends of the package with respect to the first and/or second terminal of the second transistor, respectively. In some embodiments, the one or more leads corresponding to the first contact element and the second contact element may extend in an opposite direction with respect to a direction in which the one or more leads corresponding to the third contact element and the fourth contact element extend.
According to another aspect of the present disclosure, a DC-DC converter is provided, comprising the packaged half-bridge circuit described above. According to yet another aspect of the present disclosure, a motor controller is provided, comprising the packaged half-bridge circuit described above.
Next, the present disclosure will be described with reference to the appended drawings, wherein:
Hereinafter, reference will be made to the appended drawings. It should be noted that identical reference signs may be used to refer to identical or similar components.
Package 1 comprises a die pad 2 having a first surface and a second surface. A first semiconductor die 3A (not visible in
Furthermore, package 1 comprises a first contact element 4A and a second contact element 4B that are arranged on top of first semiconductor die 3A and are electrically connected, using for example a solder or sinter layer 7, to first terminal G1 and second terminal S1 of first transistor T1, respectively.
Package 1 further comprises a second semiconductor die 3B that is arranged on top of second contact element 4B. Second semiconductor die 3B has second transistor T2 integrated thereon. Second transistor T2 comprises a first terminal G2 and a second terminal S2 arranged at a top surface of second semiconductor die 3B, and a third terminal D2 (not shown) arranged at a bottom surface of second semiconductor die 3B. Second semiconductor die 3B is attached and electrically connected to second contact element 4B with its bottom surface, using a solder or sinter layer 7, such that third terminal D2 of second transistor T2 is electrically connected to second contact element 4B. In other words, second contact element 4B forms an electrical contact for both second terminal S1 of first transistor T1 and third terminal D2 of second transistor T2.
Furthermore, package 1 comprises a third contact element 4C and a fourth contact element 4D that are arranged on top of second semiconductor die 3B and that are electrically connected, using a solder or sinter layer 7, to first terminal G2 and second terminal S2 of second transistor T2, respectively.
The structure described above is encapsulated in a solidified moulding compound 5. In the embodiment shown in
A portion of solidified moulding compound 5 may be omitted. For example, a bottom surface of die pad 2 may be exposed to an outside of package 1, such that said surface can serve as external access to die pad 2, and therefore to third terminal D1 of first transistor T1. Said bottom surface may also be attached to a heat sink or heat spreader (not shown), using thermal paste or the like, to remove heat from package 1 in operation. Similarly, a portion of solidified moulding compound 5 may be omitted such that a portion or surface of third contact element 4C and/or fourth contact element 4D are exposed to an outside of package 1.
A process of manufacturing package 1 is described next with reference to
Next, in
Then, in
For example, first and second contact element 4A and 4B may be comprised in a lead frame that is aligned with first semiconductor die 3A to properly attach the contact elements. First and second contact element 4A and 4B may be referred to as clips, having one or more respective leads 6A and 6B which will eventually extend externally to the package to enable an external connection to first terminal G1 and second terminal S1 of first transistor T1, respectively. Alternatively, the aforementioned clips are singulated prior to arranging them on first semiconductor die 3A.
Following this, in
Next, in
For example, third and fourth contact element 4C and 4D may be comprised in a lead frame that is aligned with second semiconductor die 3B to properly attach the contact elements. Third and fourth contact element 4C and 4D may be referred to as clips, having one or more respective leads 6C and 6D which will eventually extend externally to the package to enable an external connection to first terminal G2 and second terminal S2 of second transistor T2, respectively. Alternatively, the aforementioned clips are singulated prior to arranging them on second semiconductor die 3B.
Referring to
Finally, in
In some embodiments, second semiconductor die 3B is identical to first semiconductor die, or has a similar transistor terminal layout. In that case, the first and/or second terminal G1, S1 of first transistor T1 may be arranged at opposing ends of package 1 with respect to first and/or second terminal G1, S1 of second transistor T2, respectively. For example, first terminal G1 of first transistor T1 is arranged at the first surface of first semiconductor die 3A at an opposing end of package 1 with respect to first terminal G2 of second transistor T2. Leads 6A, 6B corresponding to first and second contact element 4A, 4B may then extend in a direction opposite to a direction in which leads 6C, 6D corresponding to third and fourth contact element 4C, 4B extend. This provides an efficiently packaged half-bridge circuit having a balanced orientation of leads on opposing sides of the package.
The embodiments discussed above are in the art referred to as loss-free packages, i.e., LFPAKs, or small outline packages, i.e., SOTs.
In the above, the present disclosure has been explained using detailed embodiments thereof. However, it should be appreciated that the disclosure is not limited to these embodiments and that various modifications are possible without deviating from the scope of the present disclosure as defined by the appended claims.
Number | Date | Country | Kind |
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21162409.3 | Mar 2021 | EP | regional |