In some examples, a method for manufacturing a semiconductor package comprises coupling first and second semiconductor dies to a metal frame; covering the first and second semiconductor dies and the metal frame with a mold compound; coupling first and second passive components to the first and second semiconductor dies, the first and second passive components on an external surface of the mold compound; sawing through a portion of the metal frame from a first direction to form a first vertical surface of the metal frame, the first vertical surface having a first roughness due to the sawing; and laser cutting through the mold compound and a remainder of the metal frame from a second direction opposing the first direction to form a second vertical surface on the metal frame and a third vertical surface on the mold compound, the second vertical surface having a second roughness due to the laser cutting and the third vertical surface having a third roughness due to the laser cutting.

BACKGROUND

During semiconductor chip manufacturing, circuits may be formed on a semiconductor wafer (or more simply “wafer”). The wafer may be separated (or “singulated”) into a plurality of semiconductor dies, each die having a circuit formed thereon. Each die is then coupled to a die pad and is coupled (e.g., via bond wires) to conductive terminals. A mold compound is applied to cover the die, the die pad, the bond wires, and the conductive terminals, thus forming a semiconductor package. The semiconductor package may be integrated in an electronic device (e.g., computers, smartphones).

SUMMARY

In some examples, a method for manufacturing a semiconductor package comprises coupling first and second semiconductor dies to a metal frame; covering the first and second semiconductor dies and the metal frame with a mold compound; coupling first and second passive components to the first and second semiconductor dies, the first and second passive components on an external surface of the mold compound; sawing through a portion of the metal frame from a first direction to form a first vertical surface of the metal frame, the first vertical surface having a first roughness due to the sawing; and laser cutting through the mold compound and a remainder of the metal frame from a second direction opposing the first direction to form a second vertical surface on the metal frame and a third vertical surface on the mold compound, the second vertical surface having a second roughness due to the laser cutting and the third vertical surface having a third roughness due to the laser cutting.

In examples, a semiconductor package comprises a metal structure including first and second vertical surfaces having first and second roughnesses, respectively; a semiconductor die coupled to the metal structure; a mold compound covering the metal structure and the semiconductor die, the mold compound having a third vertical surface, the third vertical surface having a third roughness; and a passive component on an external surface of the mold compound and coupled to the semiconductor die.

DETAILED DESCRIPTION

It is generally desirable for semiconductor packages to be as small and efficiently designed as possible. To that end, electrical components (e.g., passive components, such as inductors, capacitors, etc.) that have traditionally been included inside semiconductor packages are frequently re-located to an exterior of the semiconductor package to reduce the size of the semiconductor package or to accommodate other components within the semiconductor package. For example, an inductor that would occupy significant volume within a package may instead be mounted to a top surface of the package and may be electrically coupled to a semiconductor die inside the package using conductive traces (e.g., vias) extending through the mold compound of the package. Such components are typically mounted to exteriors of semiconductor packages after mold compound has been applied to a set of semiconductor dies, but before the mold compound and semiconductor dies have been singulated to form individual packages. Thus, during singulation, the components are already mounted to the exterior surfaces of the semiconductor packages. The singulation process typically entails the use of cutting equipment (e.g., saws) that may strike the components mounted to the exterior surfaces of the packages. Such physical trauma may damage the components. Such damage may also reduce manufacturing yield.

This disclosure describes various examples of a semiconductor package manufacturing technique that mitigates the challenges described above. More specifically, the package manufacturing technique is a singulation technique that may be useful to produce individual semiconductor packages after a mold compound has been applied and after components (e.g., passive components, such as inductors) have been coupled to exterior surfaces of the mold compound. The singulation technique avoids collisions with the components mounted to the exterior surfaces of the mold compound, thereby avoiding damage to the components and significantly boosting manufacturing yield. In examples, the singulation technique includes coupling first and second semiconductor dies to a metal frame and covering the first and second semiconductor dies and the metal frame with a mold compound. The technique also includes coupling first and second passive components to the first and second semiconductor dies, the first and second passive components being on an external surface of the mold compound. The technique further comprises sawing through a portion of the metal frame from a first direction to produce a first vertical surface of the metal frame. The first vertical surface has a first roughness due to the sawing. The technique also comprises laser cutting through the mold compound and a remainder of the metal frame from a second direction opposing the first direction to produce a second vertical surface on the metal frame and a third vertical surface on the mold compound. The second vertical surface has a second roughness due to the laser cutting and the third vertical surface has a third roughness due to the laser cutting.

FIG.1Ais a cross-sectional view of a semiconductor package100having been manufactured using the singulation technique described herein, in accordance with various examples. As described below, the semiconductor package100includes physical evidence that the package100was manufactured using the singulation techniques described herein. The package100includes a semiconductor die102coupled to a die pad104. The semiconductor die102may be coupled to the die pad104by way of a die attach layer, which is not expressly shown. The semiconductor die102includes a device side106in which circuitry is formed. Ball bonds108are coupled to the device side106, and bond wires110couple to conductive terminals112. A conductive member114extends vertically between a bottom surface116and a top surface118of the package100. A mold compound120covers the semiconductor die102, die pad104, ball bonds108, bond wires110, conductive terminals112, and conductive members114. A passive component122(e.g., inductor, capacitor) is coupled to the top surface118of the package100. The conductive member114extends through the top surface118and has a top surface115that couples to a conductive terminal (not expressly shown) of the passive component122. The conductive member114may be coupled to the device side106of the semiconductor die102through any suitable combination of conductive terminals112, bond wires110, metal traces on a printed circuit board (PCB) to which the package100may be coupled, etc.FIG.1Adoes not expressly show such connections. Additional conductive members114may be included.

The package100is manufactured using the singulation techniques described herein. The singulation techniques are applied to a structure that includes a lead frame, semiconductor dies on the die pads of the lead frame, a mold compound applied to the dies and the lead frame, and passive components coupled to the mold compound. The singulation techniques result in the formation of multiple, individual semiconductor packages100. The singulation techniques, as described above, include using a blade saw (e.g., tape saw) to cut part of the way through the lead frame from a first direction. The singulation techniques also include using a laser to cut through the mold compound and the remainder of the lead frame from a second direction that is opposite the first direction. A package manufactured using these singulation techniques will bear physical marks indicating that the singulation techniques were used. Specifically, each conductive terminal112, which is useful to couple to a PCB or other electrical component, includes a notch124. The notch124is formed because the saw cut, described above, is a relatively wide cut, while the laser cut, also described above, is a relatively narrow cut. Consequently, a vertical surface126formed by the saw cut is a horizontal distance132from a center134of the package100. In contrast, a vertical surface128formed by the laser cut is a horizontal distance136from the center134, and a vertical surface130formed by the laser cut is a horizontal distance138from the center134. The horizontal distances136and138are greater than the horizontal distance132.

In addition, the vertical surface126, which is formed by the blade saw cut, has a different roughness than the vertical surface128, which is formed by a laser cut. Similarly, the vertical surface126has a different roughness than the vertical surface130, which is also formed by a laser cut. Because the vertical surface128is composed of metal and vertical surface130is composed of mold compound, these surfaces may have differing roughnesses, even though both were revealed using a laser. Each of the vertical surfaces126,128, and130may have different roughnesses than the roughnesses of other parts of the structure ofFIG.1A, such as other metal components (e.g., die pad104). Based on real-world measurement data, the vertical surface126has a roughness ranging from 4 microns to 8 microns (roughness average (Ra)) due to the saw cut. Based on real-world measurement data, the surface128has a roughness ranging from 6 microns to 12 microns (Ra) due to the laser cut. Based on real-world measurement data, the surface130has a roughness ranging from 10 microns to 16 microns (Ra) due to the laser cut. A roughness outside of this range appears as physical voiding (i.e., a pitted appearance and structure). The laser cut makes use of ablation/thermal processes where the material (such as mold compound) is being heated by molecular vibrations. This process produces significant amounts of peripheral heating as well as loose debris, recast material and relatively rough edges. This produces missing mold compound fillers which will leave gaps and increase roughness. In contrast, diamond sawing produces a roughness that is dependent on blade grain structure and processing temperature, and the mold compound fillers remain intact after sawing.

In addition to differing distances from the center134and different roughnesses, the vertical surfaces126,128, and130that are cut differently will have different roughness patterns. For example, a blade saw may cause the vertical surface126to have a roughness pattern that includes a finer roughness than would be obtained with a laser cut, and that follows the blade grain structure.FIG.1Bshows an example surface having been exposed by a blade saw. In contrast, a laser cut may cause the surfaces128and130to have a roughness pattern that is rougher than that of a blade cut. For example, a laser used to cut a mold compound may expose a mold compound surface that is missing mold compound fillers as a result of the laser cut, as numeral140inFIG.1Cshows.

FIG.1Dis a top-down view of the semiconductor package100, in accordance with various examples.FIG.1Eis a profile view of the semiconductor package100, in accordance with various examples.FIG.1Fis a perspective view of the semiconductor package100, in accordance with various examples.

FIG.2is a flow diagram of a method200for manufacturing a semiconductor package using the singulation technique described herein, in accordance with various examples.FIG.3A-3Fare a cross-sectional process flow for manufacturing a semiconductor package using the singulation technique described herein, in accordance with various examples. Accordingly,FIGS.2and3A-3Fare now described in parallel. The method200includes coupling first and second semiconductor dies to a metal frame (202).FIG.3Ashows a cross-sectional view of a lead frame300(e.g., a copper lead frame) to which semiconductor dies102are coupled. The components of the lead frame300shown inFIG.3Ado not appear to be connected to each other, due to the cross-sectional view ofFIG.3A. However, in examples, the components of the lead frame300shown inFIG.3Aare coupled to each other. For example, the lead frame300may be part of a lead frame tape that was wound on a roll. The semiconductor dies102may be coupled to the lead frame300using a die attach layer, but to simplify the drawings, such die attach layers are not expressly shown. The lead frame300may include the conductive members114, but the conductive members114are not visible in the cross-sectional views ofFIGS.3A-3F.

The method200includes covering the first and second semiconductor dies and the metal frame with a mold compound (204).FIG.3Bis a cross-sectional view of the structure ofFIG.3A, but with a mold compound120applied to cover the lead frame300and the semiconductor dies102. The mold compound may be applied using any suitable technique, such as a mold injection technique (e.g., using a mold chase). In some examples, a mold chase used to apply a mold compound may include structural features that cover the top surfaces115of the conductive members114to prevent the mold compound from covering these surfaces115, thereby facilitating the coupling of passive components to these surfaces.

The method200may further include coupling the first and second passive components to the first and second semiconductor dies (206). The first and second passive components are coupled to an external surface of the mold compound (206).FIG.3Cis a cross-sectional view of the structure ofFIG.3B, but with the addition of passive components122. The passive components122are coupled to an external surface of the mold compound120, as shown. The passive components122may be coupled to conductive terminals that are exposed to the external surface of the mold compound120. Such conductive terminals may be electrically coupled to the semiconductor dies102. For example, the passive components122may be coupled (e.g., soldered) to the conductive members114ofFIG.1A, and these conductive members114may be electrically coupled via one or more conductive structures to the semiconductor dies102. In examples, the passive components122are of different thicknesses.

A gap301is between the passive components122. The gap301is vertically aligned with a portion of the lead frame300, as line303indicates. In examples, surfaces305and307of the passive components122face each other across the gap301, and in such examples, each of the surfaces305and307is vertically aligned with a same portion of the lead frame300, as lines309and311indicate. Such vertical alignments facilitate the formation of the notch124(FIG.1A) during the sawing process, as described below.

The method200further includes applying a tape to the first and second passive components (208).FIG.3Dis a cross-sectional view depicting the structure ofFIG.3Cpositioned on a chuck table302A or other suitable platform. The chuck table302A is coupled to multiple springs304, and the multiple springs304are coupled to chuck members302B. The springs304are useful to adjust a height of the chuck members302B. The chuck members302B support a flex frame306to which a tape308is coupled.

The tape308is useful to hold the passive components122in place during sawing operations. The tape308has features that ensure that it adheres to most or all of the passive components122, even if the passive components122have differing heights, as is the case inFIG.3D. Specifically, the tape308has features that enable it to absorb portions of the passive components122. Thus, asFIG.3Dshows, although the passive component122on the right is thicker than the passive component122on the left, the portion of the passive component122on the right that exceeds the thickness of the passive component122on the left is absorbed by the tape308, as the dashed line indicates. Critical features of the tape308required to facilitate such absorption includes its thickness, which is at least 0.50 millimeters, as well as its base thickness, which is at least 0.30 millimeters and adhesive thickness, which is at least 0.06 millimeters, and its material composition, which includes polyolefin for the base film and acrylic for adhesive. A roller310, such as a laminate roller, may be useful to adhere the tape308to the various passive components122. Thus, for example, the spring304may be useful to adjust the height of the chuck members302B, thereby adjusting a height of the tape308, and the roller310may be useful in tandem with the height adjustment feature of the spring304and chuck members302B to ensure that the tape308adheres to most or all of the passive components122. In some examples, a latch or other locking mechanism may be useful to maintain a selected height of the chuck members302B.

The method200includes cutting through a portion of the metal frame from a first direction and using a first cutting technique (210).FIG.3Eis a cross-sectional view of the structure ofFIG.3D, but with the chuck table302A and chuck members302B removed, and with the remaining structure turned upside down. Specifically, the tape308now lies on the chuck table302A. In this orientation, the lead frame300is accessible for cutting. For example, asFIG.3Eshows, a saw (e.g., a tape saw) may be used to cut through some, but not all, of the thickness of the lead frame300segment that is vertically aligned with the gap301. In examples, the lead frame300segment is sawn in the vertical direction312. In examples, a cut315formed along the vertical direction312has a width ranging from 0.20 millimeters to 0.40 millimeters. The cut315exposes vertical surfaces126of the lead frame300, as shown. In examples, the cut315extends halfway through the lead frame300segment being cut. In examples, the cut315occupies between 45% and 75% of the thickness of the lead frame300segment being cut, with a deeper cut315being disadvantageous because the lead frame becomes flimsy and easy to break (e.g., when handled in the next process step), and with a shallower cut315being disadvantageous because of an excessive thickness that the laser would have difficulty completely cutting, necessitating multiple passes to achieve a complete cut.

The method200includes cutting through the mold compound and a remainder of the metal frame from a second direction and using a second cutting technique (212). The second direction opposes the first direction (212).FIG.3Fis a cross-sectional view of the structure ofFIG.3E, except that the structure is turned upside down such that the mold compound120rests on the chuck table302A and the segment of the mold compound120between the passive components122is accessible by cutting tools. A laser is used to cut along a vertical direction314, first through the mold compound120and then through a remainder of the thickness of the lead frame300segment that contains cut315. Cut313is the result of this cutting operation. The cut of step212reveals the surface130of the mold compound120. The cut of step212also reveals the surface128of the lead frame300segment that is being cut. Thus, the lead frame300segment being cut includes the vertical surface126in the notch124and a surface128, and the mold compound120includes a surface130. The laser used to cut along the vertical direction314may have varying average power, effective cutting speed and pulse width, and may have a cut width ranging from 0.05 millimeters to 0.15 millimeters. The notch124is formed because the cut width of the saw used to form cut315is wider than the cut width of the laser used to form cut313. Because the cut313joins the cut315, packages100(FIGS.1A and1D-1F) are formed.

FIG.4Ais a cross-sectional view of a semiconductor package having been manufactured using the singulation technique described herein, in accordance with various examples. The semiconductor package100depicted inFIG.4Ais identical to that shown inFIG.1A, except that the device side106of the semiconductor die100is facing downward, toward the conductive terminals112. The device side106is coupled to the conductive terminals112by way of solder balls400. Thus, the semiconductor die100has a “flip-chip” configuration.FIG.4Bis a top-down view of the semiconductor package100, in accordance with various examples.FIG.4Cis a perspective view of the semiconductor package100, in accordance with various examples.

In this description, the term “couple” may cover connections, communications or signal paths that enable a functional relationship consistent with this description. For example, if device A provides a signal to control device B to perform an action, then: (a) in a first example, device A is directly connected to device B; or (b) in a second example, device A is coupled to device B through intervening component C if intervening component C does not alter the functional relationship between device A and device B, so device B is controlled by device A via the control signal provided by device A.

In this description, unless otherwise stated, “about,” “approximately” or “substantially” preceding a parameter means being within +/−10 percent of that parameter. Modifications are possible in the described examples, and other examples are possible within the scope of the claims.