CN222233622U - Packaging structure - Google Patents

Abstract

Some embodiments of the present application provide a package structure including a lead frame, a die disposed on the lead frame, metal wires electrically connecting the lead frame to the die, a rigid structure disposed above and spaced apart from the lead frame and overlapping projections of the metal wires in both horizontal and vertical directions, and a mold seal encasing the die, the metal wires, and a portion of the rigid structure therein. The present application suppresses the amount of warpage of the package structure by adding a rigid structure that overlaps with projections of the metal wire in both the horizontal direction and the vertical direction in a sectional view in order to reduce the volume of the package structure as a whole.

Description

Packaging structure

Technical Field

Embodiments of the present application relate to a package structure.

Background

As shown in fig. 1A, the conventional QFN (quad flat no-lead package) package structure 10 is wired by using a die 11 to connect conductive traces with metal wires 12, which has advantages of small size, low cost and mature technology, however, the number of IO (input/output) is gradually insufficient with the development of IC (integrated circuit) products. Referring next to fig. 1B-3, fig. 1B shows a top view of aQFN, and fig. 1C-1 shows a cross-sectional view along line A-A' of fig. 1B. As shown in fig. 1B, aQFN (modified quad flat no-lead package) package structure 10' improves the problem of IO deficiency, the die 11' has a larger number of bonding wires (i.e., more metal wires 12 ') and IO sites, but the problem is derived that as the number of bonding wires increases, the radian between bonding wires must also be raised to avoid contact with each other. As further shown in fig. 1C-1, an increase in the wire bond height of die 11' attached to leadframe 13 by adhesive layer 15 affects the thickness of mold seal 14, and mold seal 14 is typically formed of a material having a relatively large CTE (coefficient of thermal expansion), and thus affects the severity of warpage.

It can be seen that, in the prior art, the area of the die 11 '(the coverage area of the die 11' as shown in fig. 1B) is smaller than that of the die 11 of the QFN package 10, although the aQFN package 10 'has the advantage of high IO number, and a higher molding layer (EMC) 14 thickness is required due to the higher number of wire bonding rows (i.e., more metal wires 12') and higher arc height, as shown in fig. 1C-1. Therefore, aQFN 'is susceptible to shrinkage of the mold seal layer 14, resulting in excessive warpage of aQFN package structure 10', as shown in fig. 1C-2 through 1C-4. Fig. 1C-2 shows a perspective view of aQFN package structure 10 'of fig. 1C-1 at another angle, wherein wafer 11' is covered by mold layer 14, and mold layer 14 is shown as translucent in fig. 1C-2 and therefore not shown. Fig. 1D-1F illustrate a process flow of aQFN package structure 10 'of fig. 1C-1, specifically, attaching die 11' to leadframe 13, forming metal wires 12 'by wire bonding as is commonly used in the art, after which a mold seal 14 is formed over leadframe 13 and die 11'. Finally, aQFN package structure 10' of fig. 1C-1 is formed by a dicing process.

Further, fig. 1C-3 to 1C-4 show warpage of the aQFN package structure 10 'at Room Temperature (RT) and High Temperature (HT), respectively, the warpage of the aQFN package structure 10' shown in fig. 1C-3 is-31 μm (-the direction indicating warpage is toward the lead frame 13), the warpage of the aQFN package structure 10 'shown in fig. 1C-4 is +28 μm (+the direction indicating warpage is away from the lead frame 13), contrary to "+", and it can be seen that in the conventional aQFN package structure 10', the warpage change (Warpage variation) at Room Temperature (RT) and High Temperature (HT) is 59 μm. Therefore, the aQFN package structure 10 'in the related art is excessively warped (59 μm) >43 μm, resulting in a aQFN package structure 10' failed to be mounted on a board, so that a Surface Mount Technology (SMT) failure rate is >50%.

In summary, in the prior art, warpage of aQFN structure 10' can only be improved by selecting materials with a smaller CTE mismatch. Therefore, there is an urgent need for a structure capable of reducing the amount of warpage while being applied to a high-wire-bonding-amount product.

Disclosure of utility model

In order to solve the above problems, the present application suppresses the amount of warpage of a package structure by adding a rigid structure. In the application, the rigid structure is coated in the mold sealing layer of the packaging structure and avoids the position where the metal wire passes, and meanwhile, in order to reduce the whole volume of the packaging structure, the rigid structure is partially overlapped with the horizontal and vertical projections of the metal wire in the sectional view.

Some embodiments of the present application provide a package structure including a lead frame, a die disposed on the lead frame, a metal wire electrically connecting the lead frame with the die, a rigid structure disposed above and spaced apart from the lead frame and overlapping projections of the rigid structure in both horizontal and vertical directions with the metal wire, and a mold seal encasing the die, the metal wire, and a portion of the rigid structure therein.

In some embodiments, the metal wire includes an apex and an endpoint connected to the leadframe, wherein the rigid structure overlaps a projection of the apex in a horizontal direction and the rigid structure overlaps a projection of the endpoint in a vertical direction.

In some embodiments, the mold seal encapsulates an upper surface of the leadframe that faces the die, the metal wires, and a lower surface of the rigid structure that faces the leadframe.

In some embodiments, the sides of the mold seal layer are not flush with the sides of the rigid structure.

In some embodiments, the sides of the mold seal layer are disposed outside the lateral extent of the rigid structure.

In some embodiments, the upper surface of the rigid structure is flush with the upper surface of the mold seal layer, wherein the upper surface of the rigid structure and the upper surface of the mold seal layer are surfaces remote from the leadframe.

In some embodiments, the coefficient of thermal expansion of the rigid structure is less than the coefficient of thermal expansion of the mold seal layer.

In some embodiments, the rigid structure is an annular structure in plan view and defines a receiving space.

In some embodiments, the apex is disposed within the receiving space.

In some embodiments, the rigid structure includes a plurality of corners and a plurality of connections connecting the corners.

In some embodiments, the corner portion has a thickness greater than a thickness of the connecting portion.

In some embodiments, the corner portion has a thickness equal to a thickness of the connecting portion.

In some embodiments, the rigid structure has a beveled surface conformal with the metal wire, the beveled surface disposed closest to the metal wire.

In some embodiments, the rigid structure is spaced apart from the leadframe by a mold seal.

In some embodiments, the metal leads electrically connect the die to pads on the leadframe.

In some embodiments, the die is attached to the leadframe by an adhesive layer.

In some embodiments, the sides of the mold seal layer are flush with the sides of the rigid structure.

Further embodiments of the present application provide a package structure comprising a lead frame, a die disposed on the lead frame, a metal wire electrically connecting the lead frame with the die, a mold seal covering the die and the metal wire, and a rigid structure encased in the mold seal and spaced apart from the lead frame, wherein the metal wire comprises an apex and an endpoint connected to the lead frame, and wherein the apex is disposed between horizontal surfaces of upper and lower surfaces of the rigid structure, and the endpoint is disposed between vertical surfaces of opposite sides of the rigid structure.

In some embodiments, the coefficient of thermal expansion of the rigid structure is less than the coefficient of thermal expansion of the mold seal layer.

In some embodiments, the rigid structure is an annular structure in plan view and defines a receiving space, wherein the apex is disposed within the receiving space.

The packaging structure provided by the application can reduce the warpage change of the packaging structure to 16 mu m, thereby increasing the upper plate rate of the corresponding packaging structure.

Drawings

The various aspects of the utility model are best understood from the following detailed description when read in connection with the accompanying drawings. It should be noted that the various components are not drawn to scale according to standard practice in the industry. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

Fig. 1A to 1F illustrate a prior art package structure and a process flow thereof.

Fig. 2-4 illustrate a package structure according to some embodiments of the application.

Fig. 5, 5A-5E illustrate package structures according to some embodiments of the application.

Fig. 6A-6C illustrate warpage of a package structure according to some embodiments of the present application.

Fig. 7-8, 9A-9B, and 10 illustrate process flows of a package structure according to some embodiments of the application.

Detailed Description

The following disclosure provides many different embodiments, or examples, for implementing different features of the utility model. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to limit the utility model. Furthermore, when values or ranges of values are recited as being "about," "approximately," "substantially," etc., unless otherwise stated, the term is intended to cover values within + -10% of the stated value. For example, the term "about 5nm" encompasses a size range from 4.5nm to 5.5 nm.

The present application reduces or inhibits warpage of a package structure by adding a rigid structure to a mold seal of the package structure, and in particular, referring to fig. 2, fig. 2 illustrates a package structure 100 according to some embodiments of the present application, the package structure 100 comprising a leadframe 103, a die 101 disposed on the leadframe 103, the die 101 being attached to the leadframe 103 by an adhesive layer 105 in some embodiments. In some embodiments, the adhesive layer 105 may be a die attach film, or may be an epoxy glue or the like. Further, the package structure 100 further includes a metal wire 102, and the metal wire 102 electrically connects the lead frame 103 with the die 101. Further, the package structure 100 further includes a rigid structure 106, the rigid structure 106 being disposed above the lead frame 103 and spaced apart from the lead frame 103 (not in contact with the lead frame 103), and the rigid structure 106 overlapping both the projection 102Rh of the metal wire 102 in the horizontal direction H and the projection 102Rv in the vertical direction V, as shown in fig. 2. In some embodiments, the package structure 100 further includes a mold layer 104 encasing the wafer 101, the metal wire 102, and a portion of the rigid structure 106, as can be seen in fig. 2, the rigid structure 106 encases the mold layer 104, and the mold layer 104 molds the metal wire 102, the wafer 101, and the like therein. Further, the rigid structure 106 is spaced apart from the leadframe 103 by a mold seal 104. Specifically, the mold layer 104 encapsulates the upper surface 103t of the leadframe 103 facing the die 101, the metal wires 102, and the lower surface 106d of the rigid structure 106 facing the leadframe 103. In the embodiment shown in fig. 2, the sides 104s of the mold seal layer 104 are flush with the sides 106s of the rigid structure 106. In other embodiments such as shown in fig. 3, the sides 104s of the mold layer 104 are not flush with the sides 106s of the rigid structure 106, in particular, the sides 104s of the mold layer 104 are disposed outside the lateral extent of the rigid structure 106, i.e., the mold layer 104 extends beyond the lateral extent of the rigid structure 106, which may be due to a dicing process of the package structure 100, as will be described in further detail below. As further shown in fig. 2, the upper surface 106t of the rigid structure 106 is flush with the upper surface 104t of the mold seal layer 104, and as can be seen in fig. 2, the upper surface 106t of the rigid structure 106 and the upper surface 104t of the mold seal layer 104 are surfaces remote from the lead frame 103.

In the above-described embodiment, the lead frame 103 may be a metal frame, such as a frame made of metal of copper, aluminum, or the like, and the lead frame 103 includes a plurality of rows of finger pads 103P connected to the metal wires 102, as shown in fig. 2, the metal wires 102 electrically connect the die 101 to the pads on the lead frame 103 (i.e., respectively to the plurality of rows of finger pads 103P). In some embodiments, the rows of finger pads 103P are integrally formed with the leadframe 103. In other embodiments, the rows of finger pads 103P are formed separately from the leadframe 103. Further, the rows of finger pads 103P may comprise the same or different materials as the leadframe 103. In the above embodiment, the metal wire 102 may include copper, tin, an alloy thereof, or the like. In the above embodiments, the rigid structure 106 may be made of a relatively strong material such as silicon, copper, etc., and the mold layer 104 may be made of a molding compound, etc. In an embodiment, the modulus of the rigid structure 106 is greater than the modulus of the mold seal layer 104, because a greater modulus may make the rigid structure 106 stiffer, thereby better resisting deformation of the package structure 100. In some embodiments, the wafer 101 may include dies or the like.

Further, referring to fig. 2, the metal wire 102 includes an apex 102t and an end 102d connected to the lead frame 103 (specifically, one of the plurality of rows of finger pads 103P of the lead frame 103), and as can be seen from fig. 2, the rigid structure 106 overlaps with a projection 102th of the apex 102t in the horizontal direction H, and the rigid structure 106 overlaps with a projection 102dv of the end 102d in the vertical direction V. In some embodiments, the Coefficient of Thermal Expansion (CTE) of the rigid structure 106 is less than the coefficient of thermal expansion of the mold seal layer 104, further reducing warpage of the package structure 100.

Referring to fig. 4, in some other embodiments, the rigid structure 106 has a beveled surface 106x (which may not be conformal in some embodiments) that is substantially conformal with the metal wire 102, the beveled surface 106x being disposed closest to the metal wire 102. In the present application, the beveled surface 106x (triangular cross section) can better avoid the metal wire 102 and can be made thicker, thereby having better ability to suppress warpage.

Fig. 5 to 5E show top views and corresponding partial cross-sectional views of the package structure 100 of fig. 2 and the package structure 300 of fig. 4. Specifically, as shown in fig. 5, the rigid structure 106 is a ring-shaped structure in a plan view, and defines an accommodation space V. Further, the apexes 102t of the metal wires 102 in the package structures 100 to 300 of fig. 2 to 4 are disposed in the accommodation space V. Fig. 5A and 5B show partial cross-sectional views of the rigid structure 106 along line B-B' of fig. 5, as can be seen in fig. 5A and 5B, the rigid structure 106 may have different cross-sectional shapes, with the rigid structure 106 being filled with the mold seal 104. Fig. 5C to 5E show a partial cross-sectional view of the rigid structure 106 along the line C-C' of fig. 5, and it can be seen from fig. 5C to 5E that the rigid structure 106 comprises a plurality of corner portions 106C and a plurality of connecting portions 106l connecting the corner portions 106C. As shown in fig. 5C and 5E, the corner portion 106C has a thickness greater than that of the connecting portion 106l. As shown in fig. 5D, the thickness of the corner portion 106c is equal to the thickness of the connecting portion 106l.

As can be seen from the above embodiments, in the present application, the rigid structure 106 may be a ring-shaped structure that is sheet-shaped and hollow in a top view (see fig. 5), and the hollow portion may accommodate the metal wire 102 to reduce the volume of the package structures 100-300. In addition, in the cross-sectional view of the corner portion 106c of the rigid structure 106 (the annular rigid structure 106 of each package structure 100-300 has four corner portions 106c, respectively) as shown in fig. 5A to 5E, the thickness of the corner portion 106c may be thickened, and the shape may be set according to the actual situation, not limited to the square shape. In the present application, the shape of the corner 106c may be sufficient to avoid the metal wire 102, and the thicker the thickness, the better the ability to suppress warpage.

Still further embodiments of the present application provide a package structure 100, with continued reference to fig. 2, comprising a leadframe 103, a die 101 disposed on the leadframe 103, a metal wire 102 electrically connecting the leadframe 103 with the die 101, a mold seal 104 encasing the die 101 and the metal wire 102, and a rigid structure 106 encased in the mold seal 104 and spaced apart from the leadframe 103. In the package structure 100, the metal wire 102 includes an apex 102t and an end point 102d connected to the lead frame 103, and wherein the apex 102t is disposed between horizontal surfaces h1 and h2 where an upper surface 106t and a lower surface 106t of the rigid structure 106 are located, and the end point 102d is disposed between vertical surfaces v1 and v2 where opposite sides of the rigid structure 106 are located. In some embodiments, the Coefficient of Thermal Expansion (CTE) of the rigid structure 106 is less than the coefficient of thermal expansion of the mold seal layer 104, further reducing warpage of the package structure 100. As also shown in fig. 5, the rigid structure 106 is an annular structure in a top view, and defines a receiving space V in which the apex 102t is disposed.

The warp variation of the package structure 100 shown in fig. 2 is shown below, in particular, as shown in fig. 6A to 6C, fig. 6A shows a perspective view of the package structure 100 of fig. 2 at another angle, wherein the wafer 101 is covered by the mold seal layer 104, and the mold seal layer 104 is shown translucent in fig. 6A and thus not shown. Fig. 6B to 6C show warpage of the package structure 100 at Room Temperature (RT) and High Temperature (HT), respectively, wherein the warpage of the package structure 100 shown in fig. 6B is-24 μm (-the direction indicating warpage is toward the lead frame 103 (as shown in fig. 2)), and the warpage of the package structure 100 shown in fig. 6C is +40 μm, and it can be seen that the warpage variation (Warpage variation) at Room Temperature (RT) and High Temperature (HT) is 16 μm (much smaller than 43 μm) for the package structure 100 provided by the present application. Therefore, the present application reduces deformation and warpage of the package structure 100 as a whole by adding the rigid structure 106 in the mold seal layer 104, and reduces the volume of the mold seal layer 104 and achieves the effect of reducing shrinkage of the mold seal layer 104 by partially overlapping the rigid structure 106 with the projection 102Rh of the metal wire 102 in the horizontal direction H and the projection 102Rv in the vertical direction V in the cross-sectional view. Therefore, the package structure 100-300 provided by the application can reduce the warpage variation to 16 μm, which is far smaller than 43 μm, and the reduced warpage variation increases the upper board rate of the corresponding package structure 100-300.

The process flow for forming the package structure 100 shown in fig. 2 and 6A will be described with reference to fig. 7-10.

Referring to fig. 7, a plurality of wafers 101 are attached to a lead frame 103 such as a copper frame, and as shown in fig. 2, the plurality of wafers 101 (such as dies) may be attached to the lead frame 103 by an adhesive layer 105, respectively. Next, referring to fig. 8, metal wires 102 (such as copper wires) are formed by wire bonding as is commonly used in the art to make wire bonds, thereby connecting die 101 to leadframe 103.

Referring to fig. 9A, a rigid structure 106 is attached over wafer 101, such as by a bracket 107 securing rigid structure 106 over wafer 101 and spacing rigid structure 106 from wafer 101 and leadframe 103. In some embodiments, the support 107 may be the same or different material as the rigid structure 106, and may be a metal support, such as a copper support, or the like. Fig. 9B shows an enlarged cross-sectional view of the area a of fig. 9A, and it can be seen from fig. 9B that the thickness of the connection rigid structure 106e between the corner portions 106c of the rigid structures 106 of the unit of each package structure 100 is thinned, i.e., the thickness of the connection rigid structure 106e is smaller than the thicknesses of the corner portions 106c and the connection portions 106l, to facilitate later dicing.

Thereafter, referring to fig. 10, the molding compound is filled in the space between the rigid structure 106 and the die 101 and leadframe 103 by compression molding or other suitable molding or filling process, thereby forming a mold layer 104 in which the die 101, metal wires 102, and leadframe 103 are molded/encapsulated. After the mold seal layer 104 is formed, the rigid structure 106 is further encased in the mold seal layer 104.

After the mold layer 104 is formed, the structure shown in fig. 10 is cut by a cutting process, such as cutting the rigid structure 106 by a relatively hard knife (such as a blade), and the mold layer 104 is cut by a blade or the like, thereby forming the package structure 100 shown in fig. 6A and 2. In the dicing process, as described above with reference to fig. 9A to 9B, the thickness of the rigid structure 106 between the units of the respective package structures 100, that is, the thickness of the connection rigid structure 106e may be thinned for dicing convenience. Furthermore, the use of different cutters for the rigid structure 106 and the mold seal 104 during the cutting process may result in the sides 104s of the mold seal 104 not being flush with the sides 106s of the rigid structure 106, as described above with reference to fig. 3.

In summary, the present application suppresses the amount of warpage of the package structures 100-300 by adding the rigid structure 106. Specifically, the rigid structure 106 is wrapped in the mold layer 104 of the package structure 100-300 and avoids the position where the metal wire 102 would pass, and in order to reduce the overall volume of the package structure 100-300, the rigid structure 106 overlaps both the projection 102Rh of the metal wire 102 in the horizontal direction H and the projection 102Rv of the metal wire 102 in the vertical direction V in the cross-sectional view. In addition, the package structure 100-300 provided by the application can reduce the warpage variation to 16 μm, which is far smaller than 43 μm, and the reduced warpage variation increases the upper board rate of the corresponding package structure 100-300.

The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present utility model. Those skilled in the art will appreciate that they may readily use the present utility model as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments described herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the utility model, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the utility model.

Claims (10)

1. A package structure, comprising:

A lead frame;

a die disposed on the leadframe;

a metal wire electrically connecting the lead frame with the die;

a rigid structure disposed above and spaced apart from the lead frame and overlapping projections of the metal wire in both horizontal and vertical directions, and

And the die sealing layer is used for wrapping the wafer, the metal wires and part of the rigid structure.

2. The package structure of claim 1, wherein the metal wire includes an apex and an end connected to the leadframe,

Wherein the rigid structure overlaps with a projection of the apex in a horizontal direction and the rigid structure overlaps with a projection of the end point in a vertical direction.

3. The package structure of claim 1, wherein the mold layer further encapsulates an upper surface of the leadframe that faces the die.

4. The package structure of claim 1, wherein the sides of the mold layer are not flush with the sides of the rigid structure.

5. The package structure of claim 1, wherein an upper surface of the rigid structure is flush with an upper surface of the mold seal, wherein the upper surface of the rigid structure and the upper surface of the mold seal are surfaces remote from the leadframe.

6. The package structure of claim 1, wherein the coefficient of thermal expansion of the rigid structure is less than the coefficient of thermal expansion of the mold layer.

7. The package structure according to claim 2, wherein the rigid structure is an annular structure in plan view and defines a receiving space.

8. The package structure of claim 7, wherein the vertex is disposed within the receiving space.

9. The package structure of claim 1, wherein the rigid structure comprises a plurality of corner portions and a plurality of connection portions connecting the corner portions, wherein a thickness of the corner portions is greater than a thickness of the connection portions.

10. The package structure of claim 1, wherein the rigid structure has a beveled surface conformal with the metal wire, the beveled surface disposed closest to the metal wire.