U.S. patent application number 12/550655 was filed with the patent office on 2010-10-14 for advanced quad flat-leaded package structure and manufacturing method thereof.
This patent application is currently assigned to Advanced Semiconductor Engineering, Inc.. Invention is credited to PAO-HUEI CHANG CHIEN, WEI-LUN CHENG, PO-SHING CHIANG, PING-CHENG HU.
Application Number | 20100258921 12/550655 |
Document ID | / |
Family ID | 42933721 |
Filed Date | 2010-10-14 |
United States Patent
Application |
20100258921 |
Kind Code |
A1 |
CHANG CHIEN; PAO-HUEI ; et
al. |
October 14, 2010 |
ADVANCED QUAD FLAT-LEADED PACKAGE STRUCTURE AND MANUFACTURING
METHOD THEREOF
Abstract
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.
Inventors: |
CHANG CHIEN; PAO-HUEI;
(Kaohsiug County, TW) ; HU; PING-CHENG; (Kaohsiung
City, TW) ; CHIANG; PO-SHING; (Kaohsiung County,
TW) ; CHENG; WEI-LUN; (Kaohsiung City, TW) |
Correspondence
Address: |
COOLEY LLP;ATTN: Patent Group
Suite 1100, 777 - 6th Street, NW
WASHINGTON
DC
20001
US
|
Assignee: |
Advanced Semiconductor Engineering,
Inc.
Kaohsiung
TW
|
Family ID: |
42933721 |
Appl. No.: |
12/550655 |
Filed: |
August 31, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61168220 |
Apr 10, 2009 |
|
|
|
Current U.S.
Class: |
257/676 ;
257/E21.506; 257/E23.031; 438/123 |
Current CPC
Class: |
H01L 2924/01006
20130101; H01L 2224/48257 20130101; H01L 2924/078 20130101; H01L
2224/48253 20130101; H01L 24/48 20130101; H01L 2924/01079 20130101;
H01L 24/92 20130101; H01L 23/3107 20130101; H01L 2924/00014
20130101; H01L 2924/01046 20130101; H01L 2924/01021 20130101; H01L
2924/181 20130101; H01L 21/565 20130101; H01L 2924/00014 20130101;
H01L 2924/01005 20130101; H01L 24/28 20130101; H01L 2924/01029
20130101; H01L 2924/01078 20130101; H01L 2224/48091 20130101; H01L
2224/73265 20130101; H01L 2924/01074 20130101; H01L 2924/01082
20130101; H01L 2924/01028 20130101; H01L 2224/85464 20130101; H01L
2224/484 20130101; H01L 2224/85455 20130101; H01L 2924/15153
20130101; H01L 2924/014 20130101; H01L 2924/15165 20130101; H01L
21/4832 20130101; H01L 2224/48247 20130101; H01L 2924/30107
20130101; H01L 2924/00014 20130101; H01L 2224/48257 20130101; H01L
2924/00 20130101; H01L 2924/00012 20130101; H01L 2924/00014
20130101; H01L 2224/32245 20130101; H01L 2224/45099 20130101; H01L
2224/32245 20130101; H01L 2224/48247 20130101; H01L 2224/32245
20130101; H01L 2224/484 20130101; H01L 2224/73265 20130101; H01L
2224/48091 20130101; H01L 2224/85444 20130101; H01L 23/49582
20130101; H01L 2924/01014 20130101; H01L 2924/00014 20130101; H01L
2924/181 20130101; H01L 2224/32257 20130101; H01L 2224/73265
20130101; H01L 2924/01033 20130101; H01L 2224/05599 20130101 |
Class at
Publication: |
257/676 ;
438/123; 257/E23.031; 257/E21.506 |
International
Class: |
H01L 23/495 20060101
H01L023/495; H01L 21/60 20060101 H01L021/60 |
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.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] 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 INVENTION
[0002] 1. Field of the Invention
[0003] 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.
[0004] 2. Description of Related Art
[0005] 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.
[0006] 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 INVENTION
[0007] The 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.
[0008] 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.
[0009] 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.
[0010] 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.
[0011] 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.
[0012] 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.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] 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.
[0014] FIGS. 1A through 1G are schematic cross-sectional views
illustrating a manufacturing method of an advanced quad flat
non-leaded (a-QFN) package structure according to an embodiment of
the present invention.
[0015] FIGS. 1C'-1C''' show schematic, enlarged views of one
exemplary inner lead of the a-QFN package structure.
[0016] FIG. 1A' show a schematic, enlarged top view regarding part
of the photoresist pattern for the exemplary inner lead of FIG.
2D.
[0017] FIG. 1B' show a schematic, enlarged top view regarding part
of the resultant metal pattern following FIG. 1A'.
[0018] FIGS. 2A-2F are schematic top views illustrating designs of
the inner leads and the locking grooves of the present
invention.
[0019] FIG. 3A shows a schematic bottom view illustrating an
advanced quad flat non-leaded (a-QFN) package structure according
to an embodiment of the present invention.
[0020] FIG. 3B is a schematic cross-sectional view along a line
I-I' of the a-QFN package structure depicted in FIG. 3A.
[0021] FIGS. 4A through 4D are schematic views illustrating a
manufacturing method of an advanced quad flat non-leaded package
structure according to another embodiment of the present
invention.
DESCRIPTION OF THE EMBODIMENTS
[0022] 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.
[0023] FIGS. 1A through 1G are schematic cross-sectional views
illustrating a manufacturing method of an advanced quad flat
non-leaded package structure according to an embodiment of the
present invention.
[0024] As shown in FIG. 1A, a substrate 110 having the upper
surface 110a and the lower surface 110b is provided. The material
of the substrate 110 can be, for example, copper, a copper alloy,
or other applicable metal materials. Next, still referring to the
FIG. 1A, a first patterned photoresist layer 114a is formed on the
upper surface 110a of the substrate 110, and a second patterned
photoresist layer 114b is formed on the lower surface 110b of the
substrate 110. Basically, the patterns of the first patterned
photoresist layer 114a are mostly symmetric to those of the second
patterned photoresist layer 114b, except for the location(s) of the
to-be-formed die pad(s).
[0025] Next, referring to the FIG. 1B, using the first/second
photoresist layers 114a/114b as masks, a first/second metal layers
116a/116b is respectively formed on the exposed portions of the
upper surface 110a of the substrate 110 or the exposed portions of
the lower surface 110b of the substrate 110. In the present
embodiment, the first metal layer 116a and the second metal layer
116b may be formed by, for example, plating. The material of the
first metal layer 116a and/or the second metal layer 116b may
comprise nickel, gold or palladium, for example. The first or
second metal layer 116a/116b described herein may be composed of
various groups of unconnected patterns or a continuous layer,
depending on the pattern designs of the first or second patterned
photoresist layer 114a/114b.
[0026] As shown in FIG. 1B, the first metal layer 116a includes a
plurality of first metal portions 115a and at least a second metal
portion 115b. The first metal portions 115a subsequently will be
formed as inner leads 130, while the second metal portion 115b will
subsequently be formed as a ground ring 124 of the die pad 120 (as
shown in FIG. 1D). Similarly, the second metal layer 116b includes
a plurality of third metal portions 117a and at least a fourth
metal portion 117b. The third metal portions 117a correspond to the
subsequently to-be-formed inner leads 130, while the second metal
portion 117b corresponds to the subsequently to-be-formed die pad
120.
[0027] Next, referring to the FIG. 1C, after removing the first and
second photoresist layers 214a/214b, an etching process is
performed to the upper surface 110a of the substrate 110 by using
the first metal layer 116a as an etching mask, so as to remove
portions of the substrate 110 and form at least an accommodating
cavity 120a and a plurality of first openings S1. The etching
process can be a wet etching process, for example. So far, the
carrier 100 is roughly formed following the formation of the first
metal layer 116a, the second metal layer 116b and patterning the
substrate 110.
[0028] 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.
[0029] 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.
[0030] 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.
[0031] For example, the exemplary designs of the inner leads 130
and the locking grooves 132 are shown in FIG. 2A-2F. The exemplary
cross-sectional views of the locking grooves 132 can be arched (as
shown in FIG. 2A), semicircular, elliptical, oval, circular,
T-shaped (FIG. 2C), square (FIG. 2B), rectangular (FIG. 2D),
polygonal (triangular, tetragonal, pentagonal, hexagonal . . .
etc.) or a combination thereof, for example. The exemplary
cross-sectional views of the inner leads 130 can be circular (as
shown in FIGS. 2A-2C), arched, oval, elliptical, square (FIG. 2D),
polygonal (e.g. hexagonal as shown in FIG. 2E) or a combination
thereof (e.g. FIG. 2F), for example.
[0032] 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.
[0033] In this embodiment, during the etching process of FIG. 1C,
the inner lead 130 and the locking grooves 132 (if needed,
depending on the design) are formed simultaneously. The etching
rate, selectivity of the etching process can be finely tuned for
optimal performances, so as to control the dimension or the profile
of the grooves and optimize the shapes of the lead patterns.
However, according to the other embodiment, the inner lead 130 and
the locking grooves 132 may be formed sequentially by two etching
process steps.
[0034] If considering the inner lead shown in FIG. 2D as an
example, the photoresist pattern of the first photoresist layer
114a is shown in FIG. 1A' and the resultant metal pattern of the
plated first metal layer 116a is shown in FIG. 1B'. The plated
first metal layer 116a (on top of the inner lead 130) has two
recesses 116c corresponding to the underlying locking grooves 132.
Taking FIG. 1B' as an example, for the plated first metal layer
116a, the dimension d of the recess may range from 10 microns to 50
microns, while the dimension D of the metal pattern (on top of the
inner lead) may range from 150 microns to 250 microns. In addition,
the pitch between inner leads may range from 150 microns to 250
microns, and the dimension ratio D/d ranges from about 20:1 to
4:1.
[0035] Next, referring to the FIG. 1D, at least a chip 150 is
attached to the central portion 122 of each accommodating cavity
110a with an adhesive layer 140 in-between.
[0036] Next, referring to the FIG. 1E, a plurality of wires 160 are
provided between the chip 150, the ground ring 124 and the inner
leads 130. In other words, the chip 150 is electrically connected
to the ground ring 124 and the inner leads 130 through the wires
160.
[0037] Next, referring to the FIG. 1F, a molding compound 180 is
formed to encapsulate the chip 150, the wires 160, the inner leads
130, the ground ring 124, and fill the accommodating cavities 120a
and the first openings S1. Although the molding compound is
described herein, any suitable package body can be used.
[0038] Then, referring to the FIG. 1G, using the second metal layer
116b as an etching mask, an etching process is performed toward the
lower surface 110b of the carrier 100 to remove a portion of the
substrate 110, so that the carrier 100 is etched through to expose
the molding compound 180 filled inside the first openings S1 and
simultaneously form a plurality of second openings S2. Owning to
the formation of the second openings S2, a plurality of outer leads
136 is defined and the inner leads 130 are electrically isolated
from one another. That is, after the etching process, a plurality
of leads or contact terminals 138, each consisting of one inner
lead 130 and the corresponding outer lead 136, is formed. Besides,
the etching process further defines at least a die pad 120 of the
carrier 100. The die pad 120 is surrounded by the leads 138 and
isolated from the leads 138 through the second openings S2. On the
whole, the leads 138 are electrically isolated from one another
through this etching process. Basically, although the patterns of
the second metal layer 116b correspond to or are mostly symmetric
(except for the location of the to-be-formed die pad) to those of
the first metal layer 116a, the patterns of the second metal layer
116b can be designed to match the cross-sectional shapes of the
inner leads without the locking grooves. If considering the inner
lead shown in FIG. 2D as an example, the shape of the corresponding
outer lead can be simply square.
[0039] In detail, in the present embodiment, the first etching
process (FIG. 1C) is performed toward the upper surface 110a of the
carrier 100 using the first patterned metal layer 116a as an
etching mask, so as to form the inner leads 130 and simultaneously
form the locking grooves 132 (optional). Consequently, binding
between the inner leads 130 (along with the locking grooves 132)
and the surrounding molding compound 180 can be enhanced, so that
the contact terminals 138 will not fall off during the surface
mounting processing and the product reliability can be greatly
improved. For the a-QFN package structure 10 in the present
embodiment, the fall-off issues of the contact terminals 138 can be
lessened and the mold locking capability can be of the contact
terminals (or leads) can be enhanced.
[0040] FIG. 3A is a schematic bottom view illustrating an advanced
quad flat non-leaded (a-QFN) package structure according to an
embodiment of the present invention. FIG. 3B is a schematic
cross-sectional view along a line I-I' of the a-QFN package
structure depicted in FIG. 3A, while one of the inner lead of the
a-QFN package structure is shown in an enlarged 3-D view on the
right. Referring to FIGS. 2A and 2B, in the present embodiment, an
advanced quad flat non-leaded ( a-QFN ) package structure 20
includes a carrier 200, a chip 250, and a plurality of wires
260.
[0041] 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 FIG. 3A, only two or three columns/rows of the
contact terminals 238 are schematically depicted. Specifically, the
leads 238 are disposed around the die pad 220, and the material of
the leads 238 may comprise nickel, gold or palladium, for example.
The inner leads and the outer leads are defined by the molding
compound; that is, the portions of the leads that are encapsulated
by the molding compound are defined as the inner leads, while the
outer leads are the exposed portions of the leads.
[0042] 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.
[0043] 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.
[0044] 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.
[0045] 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 FIGS. 3A and 3B are merely
exemplificative and should not be construed as limitations to the
present invention.
[0046] FIGS. 4A through 4D are schematic views illustrating a
manufacturing method of an advanced quad flat non-leaded (a-QFN)
package structure according to another embodiment of the present
invention. FIGS. 4A & 4D are shown in top views illustrating
the lead portions, while FIGS. 4B-4C are shown in cross-sectional
views.
[0047] As shown in FIG. 4A, a substrate 410 having the upper
surface 410a is provided. Next, a first patterned photoresist layer
414a is formed on the upper surface 410a of the substrate 410. The
first patterned photoresist layer 414a includes a plurality of
hexagonal patterns 413a and each hexagonal pattern 413a includes
two recesses 413c at two opposite sides. For example, the dimension
d of the recess may range from 10 microns to 50 microns, while the
dimension D of the hexagonal pattern 413a may range from 150
microns to 250 microns. The distance (i.e. the pitch) between the
hexagonal patterns 413a may range from 150 microns to 250 microns,
and the dimension ratio D/d ranges from about 20:1 to 4:1.
[0048] Next, referring to the FIG. 4B, using the first photoresist
layer 414a as an etching mask, an etching process is performed to
the upper surface 410a of the substrate 410 to pattern the
substrate 410, so that at least an accommodating cavity 420a and a
plurality of first openings S1 are formed. The etching process can
be a wet etching process, for example. The accommodating cavity
420a has a central portion 422 and a peripheral portion 424 around
the central portion 422. Defined by the openings S1, a plurality of
individual inner lead portions 430' is formed. The inner lead
portions 430+ are disposed surrounding the peripheral portion 424.
The peripheral portion 424 can function as the ground ring.
[0049] In FIG. 4C, the remained first photoresist layer 414a is
removed and a second patterned photoresist layer 414c is formed on
the upper surface 410a of the substrate 410 and a third patterned
photoresist layer 414b is formed on the lower surface 410b of the
substrate 410. The patterns of the first patterned photoresist
layer 414a are complementary to those of the second patterned
photoresist layer 414c. Later, using the second or third patterned
photoresist layer 414c/414b as masks, the first metal layer 416a
and the second metal layer 416b are respectively formed on the
upper surface 410a and lower surface 410b by, for example, plating.
The material of the first metal layer 416a and/or the second metal
layer 416b may comprise nickel, gold or palladium, for example. As
the patterns of the second patterned photoresist layer 414c are
complementary to those of the first patterned photoresist layer
414a, the first metal layer 416a is formed directly on the inner
lead portions 430', so as to form the inner leads 430. The first or
second metal layer 416a/416b described herein may be composed of
various groups of unconnected patterns or a continuous layer,
depending on the pattern designs of the second or third patterned
photoresist layer 414c/414b.
[0050] As shown in FIG. 4D, the first metal layer 416a formed on
the inner lead portions 430' includes a plurality of hexagonal
metal patterns 415a with two recesses 415c. The inner lead 430 has
a hexagonal cross-sectional shape with two semi-circular locking
grooves 432 disposed at two opposite sides of the hexagon. The
locking groove 432 gradually becomes shallower (from the top
surface of the inner lead toward the lower portion of the inner
lead). That is, the dimension of the locking groove 432 at the
lower portion of the inner lead is smaller than d or even
approaching zero. However, the cross-sectional shape of the inner
leads and/or the locking grooves can be any geometric shapes and
should not be limited by the embodiments described herein. As the
second and third patterned photoresist layers 414c/414b are
removed, the first openings S1 are exposed. The following process
steps are similar to the steps described in FIGS. 1D-1G and will
not be described in details herein. In brief, followed by
die-attaching, wire-bonding and forming the molding compound, an
etching process is performed to the lower surface of the substrate
using the second metal layer 416b as the etching mask, so as to
etch through the substrate 410 and isolate the inner leads 430.
[0051] 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.
[0052] 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.
[0053] 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.
* * * * *