阅读说明：本技术 在集成电路封装体的腔中集成无源组件 (Integrating passive components in a cavity of an integrated circuit package ) 是由 杰弗里·莫罗尼 拉吉夫·丁卡尔·乔希 斯里尼瓦萨恩·K·科杜里 舒扬·昆达普尔·马诺哈尔 约 于 2018-04-12 设计创作，主要内容包括：一种半导体封装体包含：引线框架(100b)；半导体管芯(138),所述半导体管芯附接到所述引线框架(100)；以及无源组件(130),所述无源组件通过所述引线框架(100b)电连接到所述半导体管芯(138)。所述引线框架(100b)包含腔,所述无源组件(130)的至少一部分以堆叠布置安置在所述腔中。(A semiconductor package includes: a lead frame (100 b); a semiconductor die (138) attached to the leadframe (100); and a passive component (130) electrically connected to the semiconductor die (138) through the lead frame (100 b). The leadframe (100b) includes a cavity in which at least a portion of the passive components (130) are disposed in a stacked arrangement.)

1. A semiconductor package, comprising:

a lead frame;

a semiconductor die attached to the lead frame; and

a passive component electrically connected to the semiconductor die through the lead frame;

the leadframe includes a cavity in which at least a portion of the passive component is disposed.

2. The semiconductor package of claim 1, wherein the cavity is at a side of the leadframe facing the semiconductor die.

3. The semiconductor package of claim 2, wherein a portion of the passive component is located within the cavity and a remaining portion of the passive component is outside the cavity and between the leadframe and the semiconductor die.

4. The semiconductor package of claim 2, wherein the leadframe has a portion etched from a side opposite the semiconductor die and directly below the cavity, and the etched portion is filled with a pre-mold compound.

5. The semiconductor package of claim 1, wherein the leadframe has a thickness T and the cavity has a depth of about 50% of T.

6. The semiconductor package of claim 1, wherein the leadframe has a thickness T and the cavity has a depth of between about 20% and 40% of T.

7. The semiconductor package of claim 1, wherein no portion of the passive component protrudes out of the cavity.

8. The semiconductor package of claim 1, wherein the passive component is a capacitor.

9. The semiconductor package of claim 1, further comprising a plurality of copper pillars for attaching the semiconductor die to the leadframe.

10. A method, comprising:

etching the conductive member to form a lead frame for the semiconductor die;

etching the lead frame to form a cavity;

attaching a capacitor to the leadframe inside the cavity; and

attaching the semiconductor die to the leadframe.

11. The method of claim 10, wherein etching the leadframe to form the cavity includes etching the leadframe on a side of the leadframe facing the semiconductor die.

12. The method of claim 11, wherein a depth of the cavity is less than a height of the capacitor.

13. The method of claim 11, wherein the leadframe has a thickness T, and etching the leadframe to form the cavity includes etching the leadframe to a depth of about 50% of T.

14. The method of claim 11, wherein the leadframe has a thickness T and etching the leadframe to form the cavity includes etching the leadframe to a depth of between about 20% and 40% of T.

15. A semiconductor package, comprising:

a lead frame;

a semiconductor die attached to the lead frame; and

a capacitor electrically connected to the semiconductor die through the lead frame;

the leadframe includes a cavity at a side of the leadframe facing the semiconductor die, and at least a portion of the capacitor is disposed within the cavity of the leadframe.

16. The semiconductor package of claim 15, wherein a portion of the passive components are located within the cavity and a remaining portion of the passive components are outside the cavity and between the leadframe and the semiconductor die.

17. The semiconductor package of claim 15, wherein the leadframe has a portion etched from a side opposite the semiconductor die and directly below the cavity, wherein the etched portion is filled with a pre-mold compound.

18. The semiconductor package of claim 15, wherein the leadframe has a thickness T and the cavity has a depth of about 50% of T.

19. The semiconductor package of claim 15, wherein the leadframe has a thickness T and the cavity has a height between about 20% and 40% of T.

20. The semiconductor package of claim 15, wherein no portion of the capacitor protrudes out of the cavity.

Background

Many types of Integrated Circuits (ICs) have input/output (I/O) pins for connecting external passive or active components. An IC (also referred to as a semiconductor die) is typically attached to a leadframe and then surrounded with a molding compound to form a semiconductor package. The package is then attached to a Printed Circuit Board (PCB). Capacitors (or other types of components) may be attached to the same PCB. The capacitor is electrically connected to one or more I/O pins of the lead frame (and to the IC through the lead frame) through traces on the PCB. The connection between the capacitor and the components within the IC to which the capacitor is connected may create loop inductance, which may affect the performance of the IC in certain applications such as power converters.

For a power converter, the loop inductance may make it necessary to turn on and off the power transistors of the power converter more slowly to reduce ringing. However, turning the power transistor on and off more slowly may produce greater switching losses.

Disclosure of Invention

In described examples, a semiconductor package includes: a lead frame; a semiconductor die attached to the lead frame; and passive components (e.g., capacitors) electrically connected to the semiconductor die through the lead frame. The leadframe includes a cavity in which at least a portion of the capacitors are disposed in a stacked arrangement. In one example, the cavity is formed in the leadframe on a side of the leadframe facing the semiconductor die.

Another example relates to a method that includes etching a conductive member to form a leadframe of a semiconductor die and then etching the leadframe to form a cavity. The method further includes attaching passive components to the leadframe inside the cavity and attaching the semiconductor die to the leadframe.

In yet another example, a semiconductor package includes: a lead frame; a semiconductor die attached to the lead frame; and a capacitor electrically connected to the semiconductor die through the lead frame. The leadframe includes a cavity at a side of the leadframe facing the semiconductor die, and wherein at least a portion of the capacitor is disposed within the cavity of the leadframe.

Drawings

Fig. 1A-1G illustrate a method for forming a semiconductor package in which passive components are disposed within a cavity in a leadframe, according to an embodiment.

Fig. 2 illustrates dimensions of the embodiment according to fig. 1A-1G.

Fig. 3 shows another embodiment of forming a cavity to include passive components.

Fig. 4 shows yet another embodiment in which a cavity is formed to include passive components.

Fig. 5A-5E show a method for forming a semiconductor package in which passive components are disposed within a cavity in a leadframe, according to an alternative embodiment.

Fig. 6 illustrates dimensions according to the embodiment of fig. 5A-5E.

Fig. 7 shows an embodiment of a semiconductor package in which passive components are positioned between a semiconductor die and a leadframe without the use of a cavity.

Detailed Description

The described embodiments relate to a semiconductor package containing a semiconductor die attached to a leadframe and encapsulated in a mold. The package also includes passive components. The package includes a stacked configuration in which passive components are attached to the leadframe on the same side of the leadframe as the die or on an opposite side of the leadframe. In embodiments where the passive component is on the same side of the leadframe as the die, the passive component is mounted in a cavity formed in the leadframe, so the passive component is sandwiched between the die and the leadframe. In embodiments where the passive components are on the opposite side of the leadframe from the die, the passive components are also mounted within cavities formed in the leadframe. The passive components may have electrical contacts to the leadframe and may be connected to specific electrical contact pads of the semiconductor die through the leadframe.

By integrating the passive components into the package containing the die in a stacked arrangement of semiconductor die, passive components and lead frame, the length is reduced relative to the length of the electrical conductor (between the passive components and the die) that would exist if the passive components were completely outside the package (as described above). By reducing the length of the passive components to the die conductors, the magnitude of the loop inductance is advantageously reduced.

In the embodiments described below, the passive component is a capacitor. However, in other embodiments, the passive component may be a component other than a capacitor, such as a resistor or an inductor. Furthermore, active components, rather than passive components, may be mounted in a stacked arrangement with the semiconductor die and the leadframe.

Fig. 1A-1G illustrate an example of a process for fabricating an embodiment of a semiconductor package having a stacked configuration of semiconductor die and capacitor. Fig. 1A shows a cross-sectional view of a blank conductive member 100 a. The conductive member may comprise a copper alloy or an alloy of another suitable conductive material. The blank conductive member 100 will be processed to form a lead frame 100b, as described below.

Fig. 1B shows that the blank conductive member 100 has been partially etched to form a lead frame 100B, which includes: an upper surface 109 comprisingThere is a portion to which the semiconductor die will be attached; and a lower surface 111 containing a portion to be mounted to a PCB. In the example of fig. 1B, portions of conductive material 100 have been removed to form recesses 101, 103, and 105. The recesses 101, 103 and 105 are formed by any suitable process operation, such as etching a copper alloy. For example, by using a material based on iron chloride (FeCl)₃) Of copper chloride (CuCl) in an etching solution or complex base (e.g., pH greater than 7) solution₂) To etch the copper. FeCl₃Solution ratio is usually higher than CuCl₂The solution is more aggressive and faster, but CuCl₂The solution may be easier to control during the manufacturing process. A recess 110 is also formed, as shown. This particular recess will serve to separate the portions of the leadframe that will be electrically connected to the capacitor, thereby avoiding shorting the terminals of the capacitor together.

FIG. 1C shows the introduction of premold compound 114 into recesses 101, 103, 105, and 110. In some embodiments, the premold compound 114 is a silica-based multifunctional aromatic resin. An example of a composition of the molding compound is about 60-80% silica, and the remainder is a mixture of epoxy resin and additives that may be included to modify specific properties.

Fig. 1D shows that cavities 120 have been etched into leadframe 100 b. The conductive material 100 may be etched using a suitable etch, such as a copper etchant, to form the cavity 120. In one embodiment, the conductive material is etched from surface 109 (the surface that will face the die after mounting) towards surface 101 (the surface of the leadframe opposite the die). The cross-sectional shape and size may be any suitable shape to accommodate a capacitor.

Fig. 1E illustrates a selective metal plating process for forming conductive contacts 125a, 125b, 125c, 125d, 125E, 125f, and 125g on respective portions of conductive material 100. In this example, conductive contacts 125a, 125b, and 125c will connect the lead frame to the semiconductor die. Conductive contacts 125d and 125e will connect the lead frame to the PCB. Conductive contacts 125f and 125g are formed in the cavity 120 and will provide contact points for the capacitor.

In fig. 1F, capacitor 130 has been placed in cavity 120 and has been connected to conductive contacts 125F and 125g by solder balls 131 and 132. Fig. 1F also shows a semiconductor die 138 mounted on the conductive material 100 (i.e., the leadframe) by copper (or other suitable conductive material) posts 136 at the conductive contacts 125a, 125b, and 125 c. In this embodiment, at least a portion of the capacitor 130 is disposed within the cavity 120. Due to the height created by the copper pillars and conductive pads 125a-125c, a portion of the capacitor 130 protrudes above the cavity, as shown. In other embodiments, the entire capacitor is disposed within the cavity, wherein no portion of the capacitor protrudes above the cavity.

Fig. 1G shows the introduction of post-mold compound 140 to encapsulate semiconductor die 138 and capacitor 130, as shown, to form a semiconductor package. The post-mold compound 140 may be formulated from an epoxy resin containing inorganic fillers (e.g., fused silica), catalysts, flame retardants, stress modifiers, adhesion promoters, and other additives. In one example, the granular molding compound is liquefied and transferred into the recess using a molding press. Liquefaction produces a low viscosity material that flows easily into the mold cavity and encapsulates the device.

Fig. 2 shows a portion of the semiconductor package of fig. 1G to identify various dimensions. Electrical contacts 130a and 130b are bonded to conductive pads 125f and 125g, respectively, as shown. The thickness of the leadframe between surfaces 109 and 111 is designated T. Cavities 120 have been etched into leadframe 100b from surface 109 to a depth designated H1. The height of the capacitor is designated H2. The height of contact pads 125b, 125c, 125f, and 125g is designated as H3. The spacing between leadframe portions 100c and 100d under capacitor 130 is designated H4, and the height of copper pillar 136 is designated H5. In some embodiments, H1 (depth of cavity 120) is about 50% of T. In such an embodiment, the lead frame is half etched to form the cavities for the capacitors. The height H2 of the capacitor is less than the combined height of H1 (cavity depth), H3 (height of conductive pads 125b and 125 c), and H5 (height of copper pillar 136). An additional gap H6 is also included between the top surface 130c of capacitor 130 and the bottom surface 138a of die 138 to allow the molding compound to flow. In one example, T is 200 micrometers ("microns"), H1 (depth of cavity 120) is 100 microns, H3 is 15 microns, and H5 is 60 microns. In this example, the distance from cavity bottom 126 to bottom surface 138a of die 138 is the combined height of H1, H3, and H5, or 175 microns. Thus, in this example, the height H2 of the capacitor needs to be less than 175 microns. For example, to allow for a gap H6 of 50 microns, the height H2 of the capacitor 120 should be equal to or less than 125 microns. The length H4 of the gap between leadframe portions 100c and 100d may be 170 microns.

As shown in fig. 2, there is an inherent gap between the top surface 130c of the capacitor 130 and the bottom surface 138a of the semiconductor die 138 due to the height of the copper pillar 136 and the conductive pads 125b and 125 c. Thus, in some embodiments, if the capacitor 130 is sufficiently thin, the capacitor can be mounted in the gap without the need for the cavity 120. In some such cases, whether or not a cavity is included, the gap may be increased by using taller copper pillars 136 (e.g., 130 microns), allowing thicker capacitors to be used.

In the example of fig. 1D, the recess 110 is formed by etching the conductive member 100a from the surface 111 toward the surface 109 and etching 50% of the thickness of the conductive member 100 a. In fig. 1D, cavity 120 is then formed by etching leadframe 100b from surface 109 in the direction of opposite surface 111 and etching 50% of the thickness of the leadframe. The etch is performed until the etch tool just reaches the top surface 114a of the pre-mold compound 114.

Fig. 3 shows an alternative embodiment for forming the cavity 120. In this example, the etching tool has etched the leadframe 100b from surface 109 in the direction of surface 111, but to a depth of less than 50% of the thickness T of the leadframe. Two etching processes are performed in this embodiment. The first etching process is performed to a depth H7 to form a cavity 120 a. A second etching process is then performed in the central region of cavity 120a to a depth H8 to electrically isolate the leadframe contacts for the capacitors. In one embodiment, H7 is between about 20% and 40% of T, and H8 is T minus H7. If the recesses 110 containing the molding compound are formed to a depth of 50% of T and H7 is 20% -40% of T, H8 is 10% -30% of T.

In the example of fig. 1B-1D, the recess 110 is formed, then filled with a pre-mold compound 114, and then the cavity 120 is etched down to the level of the mold compound. Fig. 4 shows an alternative embodiment in which the recess 110 and cavity 120 are formed prior to introducing molding compound into the recess 110. In this embodiment, the conductive member 100a is etched from the two surfaces 109 and 111 in the direction of the other surface using a bidirectional etcher. Thus, the cavity 120 is formed by etching the conductive member 100a in the direction of arrow 150, while the recess 110 is formed by etching the conductive member 100a in the direction of arrow 155. After the recess 110 and the cavity 120 are completely formed, the etching process is completed. This process for forming the cavity 120 is sufficient even though the etching is not as accurate as another embodiment in which the recess 110 has already been formed and filled with the pre-mold compound 114.

Fig. 5A-5E illustrate an alternative embodiment for forming a semiconductor package. In this embodiment, the cavity and the semiconductor die are on opposite sides of the leadframe, so the cavity is not sandwiched between the leadframe and the die. This process begins with a blank conductive member 200 at fig. 5A. After the conductive member 200 has been etched and processed, it acts as a lead frame for the semiconductor die. The conductive member may comprise a copper alloy or other suitable material. Fig. 5B shows that a cavity 220 into which a capacitor is to be inserted is formed in the conductive member 200. In this embodiment, the cavity 220 may be etched to a depth of about 75% of the thickness T of the conductive member 200. Also, a recess 225 is formed to provide electrical isolation between the contacts of the capacitor.

Fig. 5C shows that the capacitor 230 has been attached to the conductive member 200 inside the cavity. In this embodiment, the height of the capacitor 230 is equal to or less than the height of the cavity. Therefore, no portion of the capacitor 230 protrudes out of the cavity. Fig. 5D shows that premold compound 235 is introduced into cavity 220 and recess 225, as well as other recesses and cavities formed in conductive member 200 to form a lead frame. Fig. 5E shows semiconductor die 240 attached to surface 200a of the leadframe by copper pillars or solder balls, which is opposite surface 200b where cavities 220 are etched to receive capacitors 230. Although not shown, the semiconductor die 240 and the lead frame are encapsulated in a post-mold compound to form a completed semiconductor package.

Fig. 6 shows a portion of the semiconductor package of fig. 5E to identify various dimensions. Electrical contacts 230a and 230b of capacitor 230 are bonded to conductive pads 225a and 225b, respectively, as shown. The thickness of the lead frame is designated T, as described above (although in each embodiment the lead frame thickness need not be the same). Cavities 220 have been etched into the leadframe 200 from surface 200a toward surface 200b to a depth designated H14. The height of the capacitor is designated H13. The height of contact pads 225a, 225b, 225c, and 225d is designated H18. The spacing of the recesses between leadframe portions 200c and 200d above capacitor 230 is designated H10, and the height of copper pillars 242 is designated H19. In some embodiments, H14 (depth of cavity 220) is about 75% of T. In such an embodiment, the leadframe is three-quarters etched to form the cavities 220 for the capacitors 230. In some embodiments, the height H13 of the capacitor is less than the height H1 of the cavity so that no portion of the capacitor protrudes out of the cavity 220. In other embodiments, a portion of the capacitor 230 does protrude out of the cavity 230. An additional gap H11 (e.g., 75 microns) is also included between the top surface 200b of the lead frame 200 and the bottom surface of the die 240 to allow the molding compound to flow. In one example, T is 200 microns, H14 (depth of cavity 120) is 150 microns, H18 is 15 microns, and H19 is 60 microns. In this example, the height H13 of the capacitor should be 150 microns (e.g., less than or equal to 135 microns). The length H10 of the gap between lead frame portions 200c and 200d may be 125 microns. The distance H12 between the end of the capacitor 230 and the sidewall 200e of the cavity 220 may be about 150 microns.

As shown in fig. 2, there is an inherent gap between the top surface 130c of the capacitor 130 and the bottom surface 138a of the semiconductor die 138 due to the height of the copper pillar 136 and the conductive pads 125b and 125 c. Thus, in some embodiments, if the capacitor 130 is sufficiently thin, the capacitor can be mounted in the gap without the need for the cavity 120. In some such cases, whether or not a cavity is included, the gap may be increased by using taller copper pillars 136 (e.g., 130 microns), allowing thicker capacitors to be used.

Fig. 7 shows an example of a semiconductor package in which passive components 330 are positioned between a semiconductor die 340 and a leadframe 300. The passive component may be a capacitor or other type of passive electrical device (e.g., an inductor). In this example, the passive components 330 are not placed within the cavities formed in the leadframe 300. The etching process (of the above described embodiments) is avoided without the need to etch the cavity for the purpose of placing the passive components. In contrast, the solder columns 325 have a height H15 that is large enough to accommodate the height of the passive components. In one example, H15 is about 130 microns, in which case the height H16 of the passive components is less than 130 microns (e.g., about 80 microns). Dimension H20 represents the spacing between the passive component and the nearest solder post 325. In one example, H20 is about 150 microns.

The opposite end of passive component 330 includes electrical contacts 330a and 330 b. Electrical contacts 330a and 330b are bonded to conductive pads 322 as shown, thereby electrically connecting the passive components to the lead frame and to semiconductor die 340 through solder columns 325. Recesses 335 are formed in the leadframe 300 to electrically isolate the electrical contacts 330a and 330b of the passive components 330.

In the example of fig. 7, a spacing of dimension H17 is provided between passive component 330 and semiconductor die 340. The spacing between the passive components and the semiconductor die allows the post-mold compound to encapsulate the semiconductor die 340 and the passive components 330, thereby forming a semiconductor package. As described above, the post-mold compound may be formulated from an epoxy resin containing inorganic fillers (e.g., fused silica), catalysts, flame retardants, stress modifiers, adhesion promoters, and other additives. In one example, the granular molding compound is liquefied and transferred into the recess using a molding apparatus.

In an example embodiment, the term "about" means that the value or range of values is or is within plus or minus 10% of the recited value or range of values.

In this description, the term "coupled" means either indirect or direct wired or wireless connection. Thus, if a first device couples to a second device, that connection may be through a direct connection, or through an indirect connection via other devices and connections. Also, in this description, the statement "based on" means "based at least in part on". Thus, if X is based on Y, X may be a function of Y and any number of other factors.

Modifications may be made to the described embodiments within the scope of the claims and other embodiments are possible.