ADVANCED QUAD FLAT-LEADED PACKAGE STRUCTURE AND MANUFACTURING METHOD THEREOF
The advanced quad flat non-leaded package structure includes a carrier, a chip, a plurality of wires, and a molding compound. The carrier includes a die pad and a plurality of leads. The inner leads of the leads electively have a plurality of locking grooves for enhancing the adhesion between the inner leads and the surrounding molding compound.
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This application claims the priority benefit of U.S. Provisional Application Ser. No. 61/168,220, filed on Apr. 10, 2009. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention generally relates to a package structure and a manufacturing method thereof. More particularly, the present invention relates to an advanced quad flat non-leaded (a-QFN) package structure and a manufacturing method thereof.
2. Description of Related Art
Quad flat package (QFP) family includes I-type (QFI), J-type (QFJ) and non-lead-type (QFN) packages, characterized by the shape of the leads of leadframes. Among them, the QFN package structures offer a variety of advantages, including reduced lead inductance, small-sized footprint, thinner profile and faster speeds for signal transmission. Thus, the QFN package has become one popular choice for the package structures and is suitable for the chip package with high-frequency (for example, radio frequency bandwidth) transmission.
For the QFN package structure, the die pad and surrounding contact terminals (lead pads) are fabricated from a planar lead-frame substrate. The QFN package structure generally is soldered to the printed circuit board (PCB) through the surface mounting technology (SMT). Accordingly, the contact terminals/pads of the QFN package structure need to be designed to fit well within the packaging process capabilities, as well as promote good long term joint reliability.
SUMMARY OF THE INVENTIONThe present invention is directed to an advanced quad flat non-leaded package structure and a manufacturing method thereof, which can help lessen lead fall-off concerns and enhance the product reliability.
The present invention provides an advanced quad flat non-leaded package structure having a carrier, a chip disposed on the carrier, a plurality of wires and a molding compound. The carrier includes a die pad and a plurality of leads, and the leads include a plurality of inner leads and a plurality of outer leads exposed by the molding compound. The inner lead includes at least one locking groove, which is capable of increasing adhesion between the inner lead and the surrounding molding compound. The wires are disposed between the chip and the inner leads. The molding compound encapsulates the chip, the die pad, the wires, the inner leads and filling the locking groove.
According to embodiments of the present invention, the shape of the inner lead may be designed to promote the locking or wedging capability of the inner leads with the surrounding molding compound. The inner lead may further include the locking groove(s), as long as the locking groove can enhance the locking capability toward the molding compound as well. The inner lead or the locking groove can be designed to have cross-sectional views of any geometric shapes. Similarly, the number or the arrangement of the locking groove(s) can be adjusted depending on the product requirements.
The present invention further provides a manufacturing method of an advanced quad flat non-leaded package structure. A substrate having an upper surface and a lower surface is provided, and the substrate includes at least an accommodating cavity and a plurality of inner leads defined by a plurality of openings there-between. The inner leads are disposed around the accommodating cavity, and the inner leads have a plurality of locking grooves. The substrate further includes a first metal layer disposed on the patterned substrate and a second metal layer disposed on the lower surface of the substrate. Followed by providing a chip to the accommodating cavity of the substrate and forming a plurality of wires between the chip and the inner leads, a molding compound is formed over the substrate to encapsulate the chip, the wires, the inner leads, and filling the accommodating cavity, the openings and the locking grooves of the inner leads. Afterwards, an etching process using the second metal layer as an etching mask is performed to etch through the substrate, until the molding compound filled inside the openings is exposed, so as to form a plurality of leads and a die pad.
According to embodiments of the present invention, the inner leads can be fabricated by plating the first metal layer and then patterning the substrate using the first metal layer as the mask. Alternatively, the inner leads can be fabricated by patterning the substrate and then forming the first metal layer on the patterned substrate by plating.
In order to make the above and other features and advantages of the present invention more comprehensible, embodiments accompanied with figures are described in detail below.
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
FIGS. 1C′-1C′″ show schematic, enlarged views of one exemplary inner lead of the a-QFN package structure.
FIG. 1A′ show a schematic, enlarged top view regarding part of the photoresist pattern for the exemplary inner lead of
FIG. 1B′ show a schematic, enlarged top view regarding part of the resultant metal pattern following FIG. 1A′.
Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the descriptions to refer to the same or like parts.
As shown in
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The accommodating cavities 120a has a central portion 122 and a peripheral portion 124 disposed around the central portion 122. Defined by the openings S1, a plurality of individual inner leads 130, also separate from the peripheral portion 124, is formed. The inner leads 130 are disposed surrounding the peripheral portion 124. The inner leads 130 may be arranged in rows, columns or arrays. The peripheral portion 124 can function as the ground ring.
In details, due to the pattern designs of the first photoresist layer 114a and/or the first metal layer 116a, the resultant inner leads 130 may be designed to posses locking grooves 132. FIG. 1C′ shows an enlarged, top view of one exemplary inner lead of the a-QFN package structure, while FIG. 1C″ is a cross-sectional view of FIG. 1C′ along the line A-A′ and FIG. 1C′″ is a cross-sectional view of FIG. 1C′ along the line B-B′. Taking the square inner lead 130 of FIG. 1C′ as an example, the locking grooves 132 may be rectangle trenches at two opposite sides of the inner lead 130.
In principle, the locking grooves are optional, depending on the shapes of the inner leads. The inner lead 130 can be a 3-D block or post with a cross-sectional view of any geometric shapes, in order to promote the locking or wedging capability of the inner leads 130 with the surrounding molding compound. As long as the locking grooves 132 of the inner leads 130 can promote the locking or wedging capability of the inner leads 130 with the molding compound, the locking grooves 132 can be a gutter or concavity with a cross-sectional view of any geometric shapes. Similarly, the shape designs of the locking grooves 132 should match or balance with the shape designs of the inner leads 130.
For example, the exemplary designs of the inner leads 130 and the locking grooves 132 are shown in
For example, considering the exemplary cross-sectional views of the inner leads being circular or hexagonal, the locking capability of the circular inner leads should be weaker than that of the hexagonal inner leads, and the circular inner leads may be further designed to have locking grooves to enhance the locking capability. However, either the existence or the arrangements of the locking grooves should be calculated together with the shapes of the inner leads as a whole for optimizing locking capability. In addition, the existence of the locking grooves will decrease the effective contact area(s) of the inner lead(s), which must be taken into consideration. In this case, it is necessary to balance the designs of the inner leads and the locking grooves.
In this embodiment, during the etching process of
If considering the inner lead shown in
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In detail, in the present embodiment, the first etching process (
The carrier 200 in the present embodiment is, for example, a metal carrier or a leadframe. In detail, the carrier 200 includes a die pad 220 and a plurality of contact terminals (leads) 238. The leads 238 include a plurality of inner leads 230 and a plurality of outer leads 236. In
In more details, the contact terminal 238 in the present embodiment has a rectangular shape. As shown in the enlarged view at the right, the inner lead 230 has at least two rectangular locking grooves 232 at two opposite sides, for example. However, the locking grooves 232 can be arranged at four sides. In the present embodiment, the arrangement or the shape of the inner leads 230 and/or the locking grooves 232 are merely exemplificative. As a result of the etching profiles, the locking groove 232 gradually becomes shallower (from the top surface of the inner lead toward the lower portion of the inner lead). That is, the cross-sectional area of the locking groove 232 gradually decreases (from the top surface of the inner lead toward the lower portion of the inner lead). Due to the shape designs of the leads and the optional locking grooves, the binding between the leads and the molding compound is significantly increased.
In addition, the a-QFN package structure 20 in the present embodiment further includes a molding compound 280. The molding compound 280 encapsulates the chip 250, the wires 260, the inner leads 230 and fills the gaps between the inner leads 230, while the outer leads 236 and the bottom surface of the die pad 220 are exposed. A material of the molding compound 280 is, for example, epoxy resins or other applicable polymer material.
Further, in the present embodiment, to meet the electrical integration design requirement of the a-QFN package structure 20, the carrier 200 further includes at least a ground ring 224. The ground ring 224 is disposed between the leads 238 and the die pad 220 and electrically connected to the chip 250 through wires 260. As the ground ring 224 is connected to the die pad 220, the die pad together with the ground ring may function as the ground plane.
It should be noted that the position, the arrangement and the amount of the leads 238, relative to the ground ring 224 and the die pad 220 as shown in
As shown in
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In
As shown in
For the a-QFN package structures according to the above embodiments, the patterns of the inner leads can be fabricated by plating the first metal layer and then patterning the substrate using the first metal layer as the mask, or by patterning the substrate and then plating the first metal layer thereon. For the previous approach, only one photomask is required, while the later approach requires two photomasks. However, as the first metal layer is formed after the etching process, the metal layer is less damaged.
The a-QFN package structures in the present embodiments are designed to have better locking capability (i.e. stronger adhesion between the inner leads and the molding compound) to solve the fall-off problems and improve the product reliability.
It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.
Claims
1. An advanced quad flat non-leaded package structure, comprising:
- a carrier having a die pad, and a plurality of leads disposed around the die pad, wherein each of the plurality of the leads includes an inner lead and an outer lead and each inner lead includes at least one locking groove;
- a chip, disposed on an upper surface of the carrier and located within the die pad;
- a plurality of wires, disposed between the chip and the inner leads; and
- a package body, encapsulating the chip on the die pad, the wires and the inner leads and filling the locking grooves.
2. The advanced quad flat non-leaded package structure as claimed in claim 1, wherein a cross-sectional shape of the inner lead is a circle and the at least one locking groove is disposed at at least one point of a circumference of the circle.
3. The advanced quad flat non-leaded package structure as claimed in claim 2, wherein each inner lead includes four locking grooves disposed at four points of a circumference of the circle.
4. The advanced quad flat non-leaded package structure as claimed in claim 1, wherein a cross-sectional shape of the inner lead is a polygon and the at least one locking groove is disposed at at least one side of the polygon.
5. The advanced quad flat non-leaded package structure as claimed in claim 4, wherein the cross-sectional shape of the inner lead is a tetragon and each inner lead includes four locking grooves disposed at four sides of the tetragon.
6. The advanced quad flat non-leaded package structure as claimed in claim 1, wherein the carrier further comprises at least a ground ring located on the die pad and electrically connected to the chip through the wire.
7. The advanced quad flat non-leaded package structure as claimed in claim 1, further comprising an adhesive layer disposed between the chip and the die pad.
8. The advanced quad flat non-leaded package structure of claim 1, further comprising:
- a first metal coating disposed on surfaces of the inner leads; and
- a second metal coating disposed on surfaces of the outer leads and on a lower surface of the die pad.
9. The advanced quad flat non-leaded package structure of claim 8, wherein the first metal coating on each inner lead has at least one recess corresponding to the at least one locking groove.
10. The advanced quad flat non-leaded package structure as claimed in claim 9, wherein a dimension of the recess ranges from about 10 microns to about 50 microns.
11. The advanced quad flat non-leaded package structure as claimed in claim 9, wherein, and a ratio of a dimension of the first metal coating on each inner lead to that of the recess ranges from about 20/1 to about 4/1.
12. The advanced quad flat non-leaded package structure as claimed in claim 8, wherein a material of the first or second metal coating comprises nickel, gold or palladium.
13. The advanced quad flat non-leaded package structure as claimed in claim 1, wherein a cross-sectional area of the locking groove at a top surface of the inner lead is larger than that of the locking groove at a lower portion of the inner lead.
14. A manufacturing method of an advanced quad flat non-leaded package structure, comprising:
- providing a metal carrier having an upper surface and a lower surface, wherein the metal carrier has at least an accommodating cavity and a plurality of inner leads defined by a plurality of openings existing there-between, the inner leads are disposed around the accommodating cavity, and the inner leads have a plurality of locking grooves, and wherein the metal carrier further includes a first metal layer disposed on the upper surface of the metal carrier and a second metal layer disposed on the lower surface of the metal carrier;
- providing a chip to the accommodating cavity of the metal carrier;
- forming a plurality of wires between the chip and the inner leads;
- forming a package body over the metal carrier to encapsulate the chip, the wires, the inner leads, and filling the accommodating cavity, the openings and the locking grooves of the inner leads; and
- performing a first etching process using the second metal layer on the lower surface of the metal carrier as an etching mask to etch through the metal carrier until the package body filled inside the openings is exposed, so as to form a plurality of leads and a die pad.
15. The manufacturing method as claimed in claim 14, wherein the step of providing the metal carrier comprises:
- forming a first patterned photoresist layer having a plurality of patterns on the upper surface of the metal carrier, wherein each of the plurality of the patterns has at least one indentation;
- performing a second etching process to the upper surface of the metal carrier, using the first patterned photoresist layer as an etching mask, to form a plurality of inner lead portions and each of the plurality of the inner lead portions has at least one groove; and
- removing the first patterned photoresist layer.
16. The manufacturing method as claimed in claim 15, further comprising forming the first metal layer directly on upper surfaces of the plurality of the inner lead portions of the metal carrier, and forming the second metal layer directly on the lower surface of the metal carrier, wherein the first metal layer formed on each of the plurality of the inner lead portions has at least one recess.
17. The manufacturing method as claimed in claim 14, wherein the first and second metal layers are formed by plating.
18. The manufacturing method as claimed in claim 14, wherein the step of providing the metal carrier comprises:
- forming a first patterned photoresist layer on the upper surface of the metal carrier and a second patterned photoresist layer on the lower surface of the metal carrier;
- forming the first metal layer directly on the upper surface of the metal carrier that is exposed by the first patterned photoresist layer, and forming the second metal layer directly on the lower surface of the metal carrier that is exposed by the second patterned photoresist layer, wherein the first metal layer includes a plurality of metal patterns, and each of the plurality of the metal patterns has at least one recess;
- removing the first and second patterned photoresist layers; and
- performing a third etching process to the upper surface of the metal carrier, using the first metal layer as an etching mask, to form the plurality of the inner leads and each of the plurality of the inner leads has at least one locking groove.
19. The manufacturing method as claimed in claim 14, further comprising forming an adhesive layer within the accommodating cavity before the chip is provided.
Type: Application
Filed: Aug 31, 2009
Publication Date: Oct 14, 2010
Applicant: Advanced Semiconductor Engineering, Inc. (Kaohsiung)
Inventors: PAO-HUEI CHANG CHIEN (Kaohsiug County), PING-CHENG HU (Kaohsiung City), PO-SHING CHIANG (Kaohsiung County), WEI-LUN CHENG (Kaohsiung City)
Application Number: 12/550,655
International Classification: H01L 23/495 (20060101); H01L 21/60 (20060101);