U.S. patent application number 12/187453 was filed with the patent office on 2009-09-17 for underfill air vent for flipchip bga.
This patent application is currently assigned to International Business Machines Corporation. Invention is credited to Takashi Hisada, Sayaka Nishi.
Application Number | 20090229513 12/187453 |
Document ID | / |
Family ID | 41061584 |
Filed Date | 2009-09-17 |
United States Patent
Application |
20090229513 |
Kind Code |
A1 |
Hisada; Takashi ; et
al. |
September 17, 2009 |
Underfill Air Vent for Flipchip BGA
Abstract
The invention relates to a system for assembling a flip chip
assembly. An underfill resin is dispensed at multiple semiconductor
die edges such that vacuum suction provided at a substrate through
hole located beneath a stage enables spread of underfill resin from
each edge simultaneously for quicker spread and reduction of voids.
The excess underfill resin suctioned through the through hole on
the underside of the semiconductor die is attracted to reusable
tape. The attracted underfill resin is cleaned from a rotating head
mechanism by a cleaning pad positioned beneath a lower surface of
the head.
Inventors: |
Hisada; Takashi; (Ritto-shi,
JP) ; Nishi; Sayaka; (Yamato-shi, JP) |
Correspondence
Address: |
The Law Firm of Andrea Hence Evans, LLC
14625 Baltimore Ave., #853
Laurel
MD
20707
US
|
Assignee: |
International Business Machines
Corporation
Armonk
NY
|
Family ID: |
41061584 |
Appl. No.: |
12/187453 |
Filed: |
August 7, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12046772 |
Mar 12, 2008 |
|
|
|
12187453 |
|
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Current U.S.
Class: |
118/50 |
Current CPC
Class: |
H01L 21/563 20130101;
H01L 2924/01079 20130101; H01L 2924/01029 20130101; H01L 2224/73204
20130101; Y10T 29/49172 20150115; H01L 2224/16237 20130101; H01L
2224/16225 20130101; Y10T 29/49171 20150115; H01L 2924/01078
20130101; H01L 24/743 20130101; H01L 24/27 20130101; H01L
2224/73203 20130101; H01L 2224/32225 20130101; H01L 2924/15151
20130101; H01L 2224/73204 20130101; H01L 2224/16225 20130101; H01L
2224/32225 20130101; H01L 2924/00 20130101 |
Class at
Publication: |
118/50 |
International
Class: |
C23C 14/00 20060101
C23C014/00 |
Claims
1. (canceled)
2. A system for assembling a flip chip assembly comprising: a flip
chip having a semiconductor die with a top surface and a bottom
surface, wherein the bottom surface is in physical communication
with a machine stage; an underfill resin, wherein the underfill
resin is dispensed in a continuous manner at all peripheral edges
of the semiconductor die by a nozzle; a substrate through hole
positioned on the bottom surface of the semiconductor die, wherein
the through hole is not capped by solder resist and the through
hole provides an electrical route and thermal conduction path; an
air vent in physical communication with the substrate through hole
and a vacuum suction means for using suction force to enable the
underfill to spread on all peripheral edges simultaneously, wherein
the machine stage further comprises a rotary head mechanism having
a reusable tape, wherein the rotary head mechanism moves the
reusable tape to remove excess resin protruding from the substrate
through hole.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation application of U.S. Ser.
No. 12/046,772 filed on Mar. 12, 2008, the entirety of which is
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to flip-chip ball grid array
(BGA) packaging, and more particularly to an underfill material
injection system for a semiconductor package that eliminates voids
or air bubbles between a semiconductor chip and a BGA substrate
during an underfill process and in a manner which shortens the
underfill time.
BACKGROUND OF THE INVENTION
[0003] FIGS. 1a through 1d illustrate an existing technique for
putting underfill resin 602 beneath the surface of a semiconductor
die 601. The underfill resin 602 is placed along two adjacent edges
of the semiconductor die 601 wherein the adjacent edges intersect.
After a period of time has elapsed, the underfill resin 602 begins
to spread by capillary effect across the under surface of the die
to opposing intersecting edges until the underneath of the die is
completely covered. However, the coverage of the voids (i.e. air
pockets or bubbles) on the semiconductor surface is not easy to
control. Further, there is a long processing time for the underfill
resin to level out.
[0004] In the past, the underfill resin has been applied along two
edges of a multiple edged die deeming it necessary to wait for the
resin to completely spread out by capillary effect such that the
underfill levels out beneath the die to substantially cover the
surface underneath, the die and eliminate voids. Further, there is
a significant problem created when overfill occurs absent a clean
up mechanism to prevent over-spreading of the underfill
material.
[0005] Akram et al., disclose, in U.S. Pat. No. 6,048,656 A, issued
Apr. 11, 2000, a vacuum source placed over an opening to draw
underfill material in a uniform manner throughout interstices so
that voids are not created. Akram et al. disclose dams disposed
along multiple edges of a flip chip im order to help contain the
flow of underfill material 190. Akram et al. further disclose using
multiple vacuum sources and multiple injection sites to assist in
the spread of underfill across the under surface of flip chip 110.
Further, Akram discloses the underfill material may be inserted
from an aperture in the substrate located beneath the semiconductor
device.
[0006] However, Akram et al. is not directed towards providing a
laminate through hole in physical communication with an air vent
and a vacuum source to promoting flow of underfill from each edge
of a semiconductor chip simultaneously. Further, Akram et al. is
not concerned with intentionally creating excessive underfill at a
through hole exit to eliminate voids and cleaning and sealing the
through hole in the manner of the present invention.
[0007] DiStefano et al. disclose, in U.S. Pat. No. 6,653,172 B2,
issued Nov. 25, 2003, methods for providing substantially void-free
layers for semiconductor assemblies. DiStefano et al. disclose
providing an interposer layer between such a fluid encapsulant
between a semiconductor chip and a substrate so that voids within
the interposer layer are sealed after applying pressure
simultaneously to the voids. However, DiStefano et al. is not
directed towards providing a laminate through hole in physical
communication with an air vent and a vacuum source to promoting
flow of underfill from each edge of a semiconductor chip
simultaneously. Further, DiStefano et al. is not concerned with
intentionally creating excessive underfill at a through hole exit
to eliminate voids and cleaning and sealing the through hole in the
manner of the present invention.
[0008] In order to combat the issue of voids, Hong et al.,
discloses in U.S. Pat. No. 6,895,666 B2, issued May 24, 2005, an
underfill system for a semiconductor package. The underfill system
uses a nozzle to dispense underfill resin into a gap between
semiconductor chips and substrates. The gap is filled with the
underfill resin due to a pressure difference between a main duct
and a plurality of sub-ducts that occurs when a blower blows air
through the main duct causing suction of the underfill from the
sub-ducts. The invention of Hong et al. provides for shortened
filling time of the underfill process and prevents voids (i.e. air
bubbles) of the filling material from forming within the gap.
[0009] However, Hong et al. is not directed towards providing a
laminate through hole in physical communication with an air vent
and a vacuum source to promoting flow of underfill from each edge
of a semiconductor chip simultaneously. Further, Hong et al. is not
concerned with intentionally creating excessive underfill at a
through hole exit to eliminate voids and cleaning and sealing the
through hole in the manner of the present invention.
[0010] Further, none of the prior art inventions resolve the issue
of preventing over spreading of the underfill material. However,
each of these solutions encounters significant problems. One
problem is the residual void occurring in underfill resin is not
eliminated in a low cost manner. The difficulty in the void control
contributes to a significant increase in manufacturing costs in
light of the prior art. Another problem is there is a long process
time for resin leveling. Further, the inefficient and
time-consuming prior art underfill techniques also cause undue and
significant increases in the manufacturing costs. None of the prior
art attempts resolve the problem caused by excessive resin
underfill.
[0011] Despite these and other efforts in the art, still further
improvements in enabling quicker underfill spread, reduction of
voids and optimal management of excessive resin underfill would be
desirable.
SUMMARY OF THE INVENTION
[0012] The present invention provides an apparatus and method of
using a through hole of a laminate as an air vent to carry out
underfilling after a flip-chip joint processing.
[0013] The present invention further provides creating the through
hole in the laminate by drilling or laser methods. The through hole
is normally capped by solder resist, but is designed not to be
capped by solder resist in the embodiments of this invention.
[0014] Vacuum suction is applied from the bottom side of the
laminate via the through hole in order to assist the resin
underfilling process. The vacuum suction is equipped at the stage
which contacts the back side of the laminate. This enables faster
underfilling to occur. Intentionally exposing excessive underfill
resin at a rate of approximately at most 10% of the total underfill
resin amount at the through hole aids in completely eliminating the
occurrence of voids.
[0015] A head which has a pressure sensor detects resin from the
through hole and moves up to press excessive resin at the hole to
flatten and cap with appropriate timing control. The head is
covered with a tape belt, and tape area wherein resin is attached
and moved down towards the cleaner pad by rotary mechanism. Resin
attached on tape is cleaned by the cleaner pad, and the tape can
continue to be re-used.
[0016] The time required to complete the underfill process will be
less than 1/2 by putting the underfill at least on four edges of a
semiconductor die.
[0017] An aspect of an embodiment of die invention provides for
vacuum suction and flattening excessive resin protrusions at the
air vented through hole reducing voids in the underfill
process.
[0018] A further aspect of an embodiment of the invention is to
control excessive resin, enabling reduction of droplets of
underfill resin at the chip edge.
[0019] An aspect of an embodiment of the invention, though
excessive underfill resins at the through hole can result in large
protrusions which affect manufacturability of the apparatus and
method, provides for the possibility of minimizing influences of
the protrusions by flattening the underfill protrusions.
[0020] Additional aspects, objectives and features of the present
invention will become apparent from the following description of
the preferred embodiments with reference to the attached
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1a illustrates a two-edged underfill technique, in
accordance with a conventional invention.
[0022] FIGS. 1b-1d illustrate a cross sectional view of a two-edged
underfill technique, in accordance with a conventional
invention.
[0023] FIGS. 2a-2g illustrates an example of a flip-chip joint in
accordance with the embodiments of the present invention.
[0024] FIG. 3a illustrates a top view of a multiple-edged underfill
technique, in accordance with the embodiments of the present
invention.
[0025] FIGS. 3b-3d illustrates a cross sectional view of a
multiple-edged underfill technique, in accordance with the
embodiments of the present invention.
[0026] FIG. 4 illustrates an underfill technique with a vacuum and
cleaning mechanism, is accordance with the embodiments of the
present invention.
[0027] FIG. 5 illustrates a process for underfill encapsulation, in
accordance with the embodiments of the present invention.
[0028] FIG. 6 illustrates an underfill technique with a vacuum and
sealing mechanism, in accordance with the embodiments of the
present invention.
[0029] FIG. 7 illustrates a detailed view an underfill process, in
accordance with the embodiments of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0030] FIGS. 2a-2g illustrate an example of a flip-chip joint. FIG.
2a illustrates a wafer bumping by plating, printing, ball bonding,
or the like. The bump can be comprised of solder, Cu pillar and
solder, gold, or the like. The bump layout can be either peripheral
or an array matrix. FIG. 2b illustrates application of a flux to
the printed circuit board (PBC) which can be comprised of an
organic carrier wherein no pre-solder is required. The laud for the
flip chip joint can be pre-soldered or the land can be comprised of
Cu with anti-oxidation, or can be Ni/Au plated, etc. FIG. 2c
illustrates flip chip placement. FIG. 2d illustrates reflow
soldering after flip-chip placement. FIG. 2e illustrates a plasma
treatment process. FIG. 2f illustrates applying an underfill resin.
FIG. 2g illustrates curing the underfill resin. Each of these
figures when taken as a whole illustrate the semiconductor
packaging process upon which this present invention is based.
[0031] FIG. 3a illustrates a top view of a technique for putting
underfill beneath the surface of a semiconductor die 701 in
accordance with an embodiment of the present invention. In a first
embodiment, underfill material 702 is placed along all peripheral
edges of a semiconductor die.
[0032] FIGS. 3b-3d are cross sectional views illustrating a
laminate 703 having a through hole 704 located in the center. The
through hole 704 is made by drilling or laser. Further, the through
hole 704 is not capped by solder resist. A vacuum source (not
shown) provides suction in the direction of arrow 705 from the
backside of the laminate. The vacuum source contains a suction port
built into a machine stage which will be discussed in detail in a
further embodiment. The vacuum source enables quicker underfill and
reduces the occurrence of voids (i.e. air bubbles). The through
hole 704 can be Cu-plated. In this case, the through hole can be an
electrical conduit and thermal conduction path. The through hole
further serves as an air vent. The location of the through hole
does not necessarily have to be at the flip-chip center. The offset
can be optimized considering spreadout of underfill resin. Further,
multiple through holes can be applied, as well.
[0033] FIG. 4 illustrates an underfill apparatus in accordance with
another embodiment of the present invention. As shown, a dispense
nozzle 801 dispenses underfill resin 802 into in a similar manner
as described in the previous embodiment. The semiconductor die 803
consists of a laminate having a through hole 804.The semiconductor
die 803 rests on a machine stage 805. A vacuum source (not shown)
causes air to move in the direction of arrow 810 and suctions the
underfill resin 802 out of the through hole 804. Excessive
underfill resin at the through hole 804 on the backside of the
semiconductor die 803 can form a large protrusion which manifests
itself by spreading out widely around the through hole opening. A
head mechanism which, is comprised of a pressure sensor 807, tape
808, and cleaning pad 809, moves up and down, and is a part of the
machine stage. The tape is rotated and operates in such a manner as
to use pressure to continually remove the excessive underfill resin
onto a clean surface of tape. The underfill resin 802 can be
cleaned at the cleaning pad located at the base of the head
mechanism.
[0034] FIG. 5, illustrates a packaging process in another
embodiment of the present, invention. Step 1001 involves bumping
process to form a bump. There are several conventional types of
bump forming processes. Step 1002 is a chip dicing process. The
bumping process and the chip dicing process are standard processes
which can be reversed. Step 1003 is a standard laminate design
process. The laminate design process involves using a drilling or
laser process to form a through hole in the laminate. The through
hole is formed without a solder resist cap in a standard processing
manner. Step 1004 involves forming a flip-chip joint. There are
several flip chip joint methods. Step 1005 involves an underfill
encapsulation process. Step 1006 involves an underfill cure
process. Step 1007 involves a marking step. Step 1008 involves a
ball grid array (BGA) ball attach process. Step 1009 involves a
package singulation process. And, Step 1010 involves a visual
inspection process.
[0035] FIG. 6 illustrates an underfill apparatus in accordance with
another embodiment of the present invention. As shown, a dispense
nozzle 901 dispenses underfill resin 902 into in a similar manner
as described in the previous embodiment. The semiconductor die 903
consists of a laminate having a through hole 904. The semiconductor
die 903 rests on a machine stage 905. A vacuum source (not shown)
causes air to move in the direction of arrow 908 and suctions the
underfill resin 902 out of the through hole 904. Optionally,
adhesive tape is applied across the through hole 904 to either
permanently or temporarily seal the through hole 904 located at the
backside of laminate 903. Excessive underfill resin at the through
hole 904 on the backside of the laminate 903 can form a large
protrusion which manifests itself by spreading out widely around
the through hole opening. A head mechanism which is comprised of a
pressure sensor 907, and tape 906, moves up and down, and is a part
of the machine stage. Optionally, the tape is rotated and operates
in such a manner as to use pressure to attach large pieces of
adhesive tape to flatten the protrusion and seal if at the same
time in an alternative method.
[0036] FIG. 7 illustrates a detailed underfill process. Step 1101
is one of the several the flip-chip joint methods. Step 1102
involves the underfill encapsulation process. The underfill
encapsulation step 1102 further is comprised of step 1104 involving
dispensing underfill resin to all edges of the semiconductor die.
Step 1105 comprises providing vacuum suction from the backside of a
laminate. Step 1107 comprises a head moving up to flatten and cap
exposed resin with the appropriate timing control. Step 1108
comprises ahead with a rotary tape mechanism which moves down upon
attaching resin. The resin is cleaned by the cleaning pad as the
head rotates to move the attached resin past the cleaning pad. Step
1103 comprises an underfill cure process.
[0037] Regarding each of the foregoing embodiments, intentionally
exposing excessive underfill resin at a rate of approximately at
most 10% of the total underfill resin amount at the through hole
aids in completely eliminating the occurrence of voids. Further,
the tape described in the foregoing embodiments can be re-used.
[0038] The apparatus/method of this invention has been described
with respect to individual semiconductor flip-chips. However, it is
contemplated that the apparatus/method of underfill encapsulation
may be employed with a plurality of semiconductor flip-chips.
[0039] While particular embodiments of the present invention have
been described herein for the purposes of illustration, many
modifications and changes will become apparent to those skilled in
the art. Accordingly, the appended claims are intended to encompass
all such modifications and changes as fall within the true spirit
and scope of this invention.
* * * * *