LEADFRAME WITH LEAD PROTRUDING FROM THE PACKAGE
The present disclosure is directed to a leadframe package having leads with protrusions on an underside of the leadframe. The protrusions come in various shapes and sizes. The protrusions extend from a body of encapsulant around the leadframe to couple to surface contacts on a substrate. The protrusions have a recess that is filled with encapsulant. Additionally, the protrusions may be part of the lead or may be a conductive layer on the lead. In some embodiments a die pad of the leadframe supporting a semiconductor die also has a protrusion on the underside of the leadframe. The protrusion on the die pad has a recess that houses an adhesive and at least part of the semiconductor die. The die pad with a protrusion may include anchor locks at the ends of the die pad to couple to the encapsulant.
The present disclosure is directed to a to a non-planar leadframe design and, in particular, to a leadframe that includes leads with protrusions that extend outside of the package for coupling the leads to a substrate.
Description of the Related ArtSemiconductor and leadframe packages often include a semiconductor die and a leadframe that provides an interface between external contacts and the semiconductor die. The semiconductor can include an encapsulant to secure the elements of the package into a single discrete unit. The semiconductor die is typically placed on the leadframe, and the combination is covered with encapsulant in an application chamber. The encapsulant is typically applied at high pressure or temperature, and is then allowed to cool and solidify around the package elements.
No-lead leadframes, such as quad-flat no-lead multiple-row (QFN-MR) leadframes, have integrated leads that are embedded in an encapsulant, with a side of the leads coplanar with a side of the encapsulant. The leads in these leadframes may suffer from degraded performance due to poor connections between the embedded leads and external contacts, such as those on a printed circuit board (PCB). The leads of the leadframe can be formed from copper, which may have insufficient wettability for establishing a low resistance electrical connection between the lead and the PCB.
In addition, the planar surface of the bottom of the leadframe package may encourage any solder to evacuate the space between the leadframe package and a PCB. Thus, what is needed is a device that encourages a higher quality of solder bonding between a lead of a leadframe and a substrate interfacing with the leadframe to which the lead is attached.
BRIEF SUMMARYThe present disclosure is directed to a leadframe package with a lead having a protrusion. The leadframe package includes a semiconductor die, a leadframe, and an encapsulant. The leadframe includes a lead and a die pad, with the die pad supporting the semiconductor die and the lead including the protrusion. The lead is electrically coupled to a contact on the semiconductor die using an electrical connector. The leadframe and the semiconductor die are encased by the encapsulant, and a portion of the protrusion has a recess filled with the encapsulant.
In some embodiments, the leadframe is coupled to a PCB. The PCB includes a contact pad, with the protrusion of the leadframe on the contact pad of the PCB. Furthermore, the protrusion is surrounded by a joint compound, such as solder, the solder forming an electrical and mechanical bond between the surface contact of the PCB and the protrusion of the leadframe.
In other embodiments, the lead has any number of shapes and configurations. For examples, the protrusion of the lead may have a cross-sectional shape that is circular, oblong, rectangular, triangular, or freeform. Additionally, the lead may be embedded in the encapsulant such that only the protrusion is exposed through the encapsulant. The lead may include a conductive layer and the conductive layer may include some or all of the protrusion
In some embodiments, the die pad of the leadframe also includes a protrusion. The protrusion of the die pad includes a recess with a portion of the semiconductor die in the recess of the protrusion of the die pad. The encapsulant also is in the recess of the protrusion of the die pad. In further embodiments, the protrusion of the die pad is coupled to a second surface contact of the die pad by a second joint compound surrounding the protrusion of the die pad.
In some embodiments with a protrusion on the die pad, the die pad includes an anchor on a first end of the die pad. The anchor may be a flared end of the die pad, such that the flared end is secured by being surrounded by encapsulant, preventing the end of the die pad from slipping out of the encapsulant under stress. Alternatively, the anchor may include a side of the die pad in the encapsulant having a concave surface.
In the following description, certain specific details are set forth in order to provide a thorough understanding of various embodiments of the disclosure. However, one skilled in the art will understand that the disclosure may be practiced without these specific details. In other instances, well-known structures associated with electronic components and fabrication techniques have not been described in detail to avoid unnecessarily obscuring the descriptions of the embodiments of the present disclosure.
Unless the context requires otherwise, throughout the specification and claims that follow, the word “comprise” and variations thereof, such as “comprises” and “comprising,” are to be construed in an open, inclusive sense, that is, as “including, but not limited to.”
Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise. It should also be noted that the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.
As used in the specification and appended claims, the use of “correspond,” “corresponds,” and “corresponding” is intended to describe a ratio of or a similarity between referenced objects. The use of “correspond” or one of its forms should not be construed to mean the exact shape or size.
Throughout the specification, the term “layer” is used in its broadest sense to include a thin film, a cap, or the like, and one layer may be composed of multiple sub-layers.
Specific embodiments of leadframe packages are described herein; however, the present disclosure and the reference to certain materials, dimensions, and the details and ordering of processing steps are exemplary and should not be limited to those shown.
The present disclosure is generally directed to leadframe packages, such as the exemplary leadframe package 100 shown in
As represented in the cross-sectional view of
In one embodiment, the leadframe 302 has a planar form factor that is stamped to form the leadframe 302. In this embodiment, the leadframe 302 may be pre-formed with space 310, or space 310 may be formed as part of the stamping process. The stamping may be conducted with the use of a mandrel or other implement useful for stamping. During the stamping, a protrusion on the stamp is pressed into the lead 308 to force the lead 308 into the recess 206 of the mold 202. To aid in the stamping process, the stamping may be conducted at various temperatures.
In another embodiment, the leadframe 302 is formed by blanket depositing a layer on a top side of the mold 202 and etching the layer to shape the leadframe 302. The leadframe may be etched using any known masking and etching chemistry, such as a selective etchant or a non-selective etchant, and a wet etch or a dry etch. Additionally, the etching may be isotropic, anisotropic, or completely anisotropic.
In yet another embodiment, the leadframe 302 is formed on the mold 202 as a nonplanar layer. For instance, the leadframe may be applied by electro-plating, metallization, or any other deposition process. Using these processes, the leadframe may be applied on the top side 204 of the mold 202 and in the recess 206 of the mold 202. The space 310 may be formed during the deposition process by using an inhibitor, or may be formed at a later stage of manufacturing through a removal process.
The lead 308 includes a first portion 312, a second portion 314, and a protruding portion 316 coupled between the first portion 312 and the second portion 314. The protruding portion 316 may include, in whole or in part, a convex surface that extends from the first portion 312 or the second portion 314. The first portion 312, the second portion 314, and the protruding portion 316 may have the same thickness as each other, and as the die pad 306. In other embodiments, there is no second portion 314 of the lead 308. The protruding portion 316 of the lead 308 may electrically and mechanically couple the first portion 312 to the second portion 314. Additionally, in some embodiments, the protruding portion 316 of the lead 308 forms a recess or an recess 318 such that the protruding portion 316 has a concave surface facing the recess 318. The recess 318 may extend from a top side of the lead 308 to beyond a first plane at the bottom side 304 of the leadframe 302 at the die pad 306, or alternatively, to beyond a second plane at the bottom side 304 of the leadframe 302 at the first portion 312 of the lead 308. In some embodiments, the protruding portion 316 of the leadframe 302 has a thickness that is less than the thickness of the first portion 312 or the second portion 314 of the lead 308. Furthermore, the protruding portion 316 of the lead 308 may have a uniform thickness between the first portion 312 and the second portion 314 of the lead 308. In some embodiments, approximately half of the volume of the recess 318 is between the first or second plane and the protruding portion 316 on the bottom side 304 of the leadframe 302. In some embodiments, the protruding portion 316 of the lead 308 covers the entirety of the recess 206 etched in the mold 202. The lead 308 may also include a contact pad positioned on a side opposite the bottom side 304.
The protrusions shown in
It is not required that the internal, concave portion and external, convex portion of the led 308 have the same shape. For example, the thickness of the lead 308 may vary to provide an ellipse on the outside convex portion as shown in
The leadframe 802 also includes a lead 811 that is separated from the die pad 804 but is electrically coupled to the semiconductor die 808. The electrical coupling between the lead 811 and the semiconductor die 808 may be over an electrical connector 809, or over any other electrical connector. The lead 811 has a first portion 812, a second portion 814, and a protruding portion 816 that mechanically and electrically couples the first portion 812 to the second portion 814. The protruding portion 816 has an internal, concave recess, the concave portion of the recess being filled with encapsulant 810 to form a protruding portion 818 of encapsulant 810. The protruding portion 816 of the lead 811 and the protruding portion 818 of the encapsulant 810 form a protrusion 820. The protrusion 820 may be any of the types discussed with respect to the other figures.
The protrusion 820 is coupled to a metal pad 823 on a top side 824 of a substrate 822. The substrate 822 may be of any of the types discussed with respect to the other figures and, in one embodiment, the substrate 822 is a PCB with a surface contact pad. The protruding portion 816 of the lead 811 contacts the metal pad 823 on the top side 824 of the substrate 822, and in one embodiment, the end is pressed with a force to be in an abutting surface contact on the substrate 822. The protrusion 820 is surrounded by a joint compound 826. The joint compound may be any substance used to secure the protrusion 820 to the substrate 822. In some embodiments, the joint compound 826 is an electrical and/or thermal conductor. In one embodiment, the joint compound 826 is a solder. The joint compound 826 at least partially surrounds the convex portion of protrusion 820. In some embodiments, the joint compound 826 extends from the first portion 812 and second portion 814 of the lead 811 to the top side 824 of the substrate 822.
The shape of the protrusion 820 may improve the connection between the leadframe package 800 and the substrate 822. In one embodiment, the shape of the protrusion 820 allows the joint compound 826 to bond with a large surface area of the lead 811, but without the leadframe package 800 and the substrate 822 exerting a compression force on the joint compound 826. One potential benefit of preventing a compression force on the joint compound is that compression can cause the joint compound 826 to be moved out of position between the lead 811 and the substrate 822. For example, without the protrusion 820, if a sufficient force is applied to bring the leadframe package 800 and the substrate 822 together, the joint compound will be expelled from between the two elements. With the designs shown, the convex part of protrusion 820 can be placed in abutting contact with the substrate 822. Some slight pressure can be applied to provide firm, abutting contact with a metal pad 823. Even if large pressure is applied, the joint compound 826 will not be compressed. Rather, the joint compound 826 can flow along on sides of the convex protrusion 820 of the lead 811 to provide a large surface area for electrical contact to the substrate 822. The encapsulant 810 in the concave region provides protruding portion 818 that mechanically supports the lead 811.
In addition, the shape of the protrusion 820 can promote a better connection electrically or mechanically between the leadframe package 800 and the substrate 822. For example, the protruding portion 816 of the lead 811 may have poor wettability characteristics for the joint compound 826. By having a protrusion 820 pierce a bubble of joint compound 826 on the substrate 822, an otherwise poor connection between the joint compound 826 and the leadframe 802 may be improved.
Viewing
As is shown in
In the embodiment shown in
The layer 1014 can be a separate, thinner layer than the lead frame 1002 because the encapsulant 1022 goes into the concave region to have a protruding 1024 that provides rigidity and mechanical strength to support the protrusion. In this case, it is not a protrusion of the lead itself, but a protrusion of an insert into a layer on the lead.
Additionally,
In the embodiment shown in
Additionally,
The lead 1106 can be any of the type shown and described with respect to
In some embodiments, the die pad 1104 includes an encapsulant lock 1126 on a side of the die pad 1104. In the embodiment shown in
The various embodiments described above can be combined to provide further embodiments. Aspects of the embodiments can be modified, if necessary to employ concepts of the various patents, applications and publications to provide yet further embodiments.
These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.
Claims
1. A package comprising:
- a die pad having a first side and a second side;
- a semiconductor die coupled to the first side of the die pad;
- a contact pad positioned on a first side of the semiconductor die;
- an electrical lead spaced from the die pad, the electrical lead having a first side and a second side;
- a contact pad positioned on the first side of the electrical lead;
- an electrical connector extending from the contact pad on the semiconductor die to the contact pad on the electrical lead;
- a protrusion extending as a portion of the electrical lead, the protrusion having a convex region that extends from the second side the electrical lead and having a concave region that is on the first side of the lead; and
- an encapsulant that overlays the semiconductor die, the die pad, and the first side of the electrical lead, the encapsulant surrounding the electrical connector, being in contact with the first side of the electrical lead and filling the concave region of the protrusion.
2. The package of claim 1 wherein the internal surface of the concave region of the protrusion has a shape that is rounded.
3. The package of claim 2 wherein the internal surface of the concave region has a semicircular shape that is approximately equal to half of a circle.
4. The package of claim 2 wherein the internal surface of the concave region has a rounded shape that is greater than 55% of a circle and less than 75% of a circle with the portion that is greater than 50% of the circle extending inward to overlay other regions of the same internal surface.
5. The package of claim 2 wherein the internal surface of the concave region extends in a rounded shape that is less than 40% of a circle.
6. The package of claim 1 wherein the internal surface of the concave region extends as a rectangle, the concave portion having two flat sidewalls that are parallel to each other and a bottom wall that is perpendicular to the flat sidewalls.
7. The package of claim 1 wherein the internal surface of the concave region extends as a triangle.
8. The package of claim 1 wherein the internal surface of the concave region extends as an ellipsoid.
9. The package of claim 1 wherein the internal surface of the concave region of the protrusion has two flat sidewalls that extend parallel to each other for a selected distance and has a bottom side with a rounded shape.
10. The package of claim 1 wherein the external surface of the convex portion extends in a rounded shape that is greater than 55% of a circle and less than 75% of a circle with the portion that is greater than 50% of the circle extending inward to be above other regions of the same external surface to create an anchor region for a solder that is applied to the convex portion of the electrical lead.
11-15. (canceled)
16. A system, comprising:
- a leadframe package including a leadframe supporting a semiconductor die, the semiconductor die and the leadframe in an encapsulant, the leadframe including a lead and a die pad, the semiconductor die on the die pad and electrically coupled to the lead, the lead having a protrusion, the encapsulant having a bottom side, a first portion of the protrusion extending away from the bottom side of the encapsulant, a portion of the encapsulant in the protrusion; and
- a printed circuit board having a surface contact, the protrusion on the surface contact and coupled to the surface contact with a joint compound.
17. The system of claim 16, wherein the lead includes a conductive layer on the lead, the protrusion including the conductive layer.
18. The system of claim 16, wherein the die pad includes a second protrusion, the second protrusion extending away from the bottom side of the encapsulant.
19. The system of claim 18, wherein a side of the die pad has an anchor, the anchor having a flared tip, the flared tip in the encapsulant.
20. The system of claim 16, wherein the lead has a side orthogonal to the bottom side of the encapsulant, the side of the lead having a side surface with a portion of the side surface having a concave curvature.
21. A device, comprising:
- a leadframe having a first side and a second side, the leadframe including: a die pad; and a lead having a protrusion on the second side of the leadframe and extending away from the lead, the protrusion having a cavity with an opening through the lead to the first side of the leadframe;
- a semiconductor die on the first side of the leadframe;
- an electrical connector coupled to the lead at a first end and the semiconductor die at a second end; and
- an encapsulant surrounding the semiconductor die and in the cavity.
22. The device of claim 21 wherein the protrusion has a wall thickness measured from the second side of the leadframe at the protrusion to the cavity, the wall thickness less than a thickness of the lead measured from the first side to the second side at a position adjacent to the first end of the electrical connector.
23. The device of claim 21 wherein one portion of the protrusion is in the shape of a hollow cylinder.
24. The device of claim 21 wherein a tip of the protrusion is rounded.
25. The device of claim 24 wherein the cavity extends into the tip, the inner wall of the tip being rounded.
Type: Application
Filed: Jan 5, 2017
Publication Date: Jul 5, 2018
Inventors: Rennier Rodriguez (Bulacan), Raymond Albert Narvadez (Santa Rosa), Ernesto Antilano, JR. (Binan Laguna)
Application Number: 15/399,536