U.S. patent application number 17/549933 was filed with the patent office on 2022-04-28 for control of under-fill using an encapsulant and a trench or dam for a dual-sided ball grid array package.
The applicant listed for this patent is SKYWORKS SOLUTIONS, INC.. Invention is credited to Robert Francis DARVEAUX, Bruce Joseph FREYMAN, Yi LIU.
Application Number | 20220130686 17/549933 |
Document ID | / |
Family ID | 1000006025726 |
Filed Date | 2022-04-28 |
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United States Patent
Application |
20220130686 |
Kind Code |
A1 |
DARVEAUX; Robert Francis ;
et al. |
April 28, 2022 |
CONTROL OF UNDER-FILL USING AN ENCAPSULANT AND A TRENCH OR DAM FOR
A DUAL-SIDED BALL GRID ARRAY PACKAGE
Abstract
Disclosed herein are methods of fabricating a packaged
radio-frequency (RF) device. The disclosed methods use an
encapsulant on solder balls in combination with a dam or a trench
to control the distribution of an under-fill material between one
or more components and a packaging substrate. The encapsulant can
be used in the ball attach process. The fluxing agent leaves behind
a material that encapsulates the base of each solder ball. The
encapsulant reduces the tendency of the under-fill material to wick
around the solder balls by capillary action which can prevent or
limit the capillary under-fill material from flowing onto or
contacting other components. The dam or trench aids in retaining
the under-fill material within a keep out zone to prevent or limit
the under-fill material from contacting other components.
Inventors: |
DARVEAUX; Robert Francis;
(Corona Del Mar, CA) ; FREYMAN; Bruce Joseph;
(Newport Coast, CA) ; LIU; Yi; (San Diego,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SKYWORKS SOLUTIONS, INC. |
Irvine |
CA |
US |
|
|
Family ID: |
1000006025726 |
Appl. No.: |
17/549933 |
Filed: |
December 14, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15885780 |
Jan 31, 2018 |
11201066 |
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17549933 |
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62452452 |
Jan 31, 2017 |
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62452457 |
Jan 31, 2017 |
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62452458 |
Jan 31, 2017 |
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62452460 |
Jan 31, 2017 |
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62452450 |
Jan 31, 2017 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 23/3135 20130101;
H01L 21/6836 20130101; H01L 23/5386 20130101; H01L 24/97 20130101;
H01L 25/0657 20130101; H01L 2224/48091 20130101; H01L 2224/92125
20130101; H01L 21/561 20130101; H01L 2224/32225 20130101; H01L
21/268 20130101; H01L 2224/92225 20130101; H01L 2224/48106
20130101; H01L 24/85 20130101; H01L 2924/0665 20130101; H01L
2224/73265 20130101; H01L 24/73 20130101; H01L 2224/831 20130101;
H01L 23/3128 20130101; H01L 2224/92247 20130101; H01L 2224/2919
20130101; H01L 2224/48227 20130101; H01L 21/568 20130101; H01L
23/544 20130101; H01L 21/0274 20130101; H01L 24/92 20130101; H01L
2224/83007 20130101; H01L 2225/0651 20130101; H01L 23/49816
20130101; H01L 2924/19011 20130101; H01L 21/481 20130101; H01L
24/32 20130101; H01L 2224/26175 20130101; H01L 2224/83855 20130101;
H01L 21/78 20130101; H01L 21/4853 20130101; H01L 2224/32227
20130101; H01L 24/16 20130101; H01L 2224/32155 20130101; H01L 24/48
20130101; H01L 2225/06572 20130101; H01L 23/5383 20130101; H01L
2224/16227 20130101; H01L 2224/83002 20130101; H01L 2924/1421
20130101; H01L 2924/3025 20130101; H01L 25/16 20130101; H01L 21/563
20130101; H01L 2225/06517 20130101; H01L 2225/06586 20130101; H01L
23/293 20130101; H01L 2223/54486 20130101; H01L 21/4864 20130101;
H01L 25/50 20130101; H01L 2224/73204 20130101; H01L 23/552
20130101; H01L 24/83 20130101; H01L 2924/19105 20130101; H01L 24/81
20130101 |
International
Class: |
H01L 21/56 20060101
H01L021/56; H01L 21/48 20060101 H01L021/48; H01L 23/552 20060101
H01L023/552; H01L 23/00 20060101 H01L023/00; H01L 23/544 20060101
H01L023/544; H01L 21/268 20060101 H01L021/268; H01L 21/683 20060101
H01L021/683; H01L 21/78 20060101 H01L021/78; H01L 23/31 20060101
H01L023/31; H01L 23/538 20060101 H01L023/538; H01L 25/065 20060101
H01L025/065; H01L 25/00 20060101 H01L025/00; H01L 23/29 20060101
H01L023/29 |
Claims
1. A method of fabricating a packaged radio-frequency (RF) device,
the method comprising: mounting electrical components to a first
side of a packaging substrate; forming a dam on a second side of
the packaging substrate; attaching solder balls to the second side
of the packaging substrate; encapsulating the solder balls with an
encapsulant; attaching a lower electrical component to the second
side of the packaging substrate; and under-filling the lower
electrical component mounted with an under-filling agent such that
the under-filling agent contacts the encapsulant or contacts the
dam.
2. The method of claim 1 wherein the encapsulant is a polymer.
3. The method of claim 1 wherein the encapsulant is not removed in
a cleaning process following attachment of the solder balls to the
packaging substrate.
4. The method of claim 1 wherein the encapsulant forms an obtuse
angle with the packaging substrate.
5. The method of claim 1 wherein the encapsulant forms an obtuse
angle to the solder balls.
6. The method of claim 1 wherein the under-filling agent contacts
the encapsulant and not the solder balls.
7. The method of claim 1 wherein the combination of the dam and the
encapsulant is configured to limit the distribution of the
under-fill material to maintain the under-fill material a targeted
distance from the solder balls while providing targeted coverage
under and around the lower electrical component.
8. The method of claim 1 wherein the dam is closer to the lower
electrical component than the encapsulant.
9. The method of claim 8 wherein the under-fill material contacts
the dam prior to contacting the encapsulant.
10. The method of claim 1 wherein the encapsulant is configured to
reduce capillary action causing the under-fill material to wick
around the solder balls.
11. A method of fabricating a packaged radio-frequency (RF) device,
the method comprising: mounting electrical components to a first
side of a packaging substrate; forming a trench on a second side of
the packaging substrate; attaching solder balls to the second side
of the packaging substrate; encapsulating the solder balls with an
encapsulant; attaching a lower electrical component to the second
side of the packaging substrate; and under-filling the lower
electrical component mounted with an under-filling agent such that
the under-filling agent contacts the encapsulant or at least
partially fills the trench.
12. The method of claim 11 wherein the encapsulant is a
polymer.
13. The method of claim 11 wherein the encapsulant is not removed
in a cleaning process following attachment of the solder balls to
the packaging substrate.
14. The method of claim 11 wherein the encapsulant forms an obtuse
angle with the packaging substrate.
15. The method of claim 11 wherein the encapsulant forms an obtuse
angle to the solder balls.
16. The method of claim 11 wherein the under-filling agent contacts
the encapsulant and not the solder balls.
17. The method of claim 11 wherein the combination of the trench
and the encapsulant is configured to limit the distribution of the
under-fill material to maintain the under-fill material a targeted
distance from the solder balls while providing targeted coverage
under and around the lower electrical component.
18. The method of claim 11 wherein the trench is closer to the
lower electrical component than the encapsulant.
19. The method of claim 18 wherein the under-fill material fills
the trench prior to contacting the encapsulant.
20. The method of claim 11 wherein the encapsulant is configured to
reduce capillary action causing the under-fill material to wick
around the solder balls.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 15/885,780 filed Jan. 31, 2018 and entitled
"CONTROL OF UNDER-FILL USING A DAM ON A PACKAGING SUBSTRATE FOR A
DUAL-SIDED BALL GRID ARRAY PACKAGE," which claims priority to U.S.
Provisional Application No. 62/452,450 filed Jan. 31, 2017 and
entitled "CONTROL OF UNDER-FILL USING A FILM DURING FABRICATION FOR
A DUAL-SIDED BALL GRID ARRAY PACKAGE," to U.S. Provisional
Application No. 62/452,452 filed Jan. 31, 2017 and entitled
"CONTROL OF UNDER-FILL USING UNDER-FILL DEFLASH FOR A DUAL-SIDED
BALL GRID ARRAY PACKAGE," to U.S. Provisional Application No.
62/452,457 filed Jan. 31, 2017 and entitled "CONTROL OF UNDER-FILL
USING A FILM DURING FABRICATION FOR A DUAL-SIDED BALL GRID ARRAY
PACKAGE," to U.S. Provisional Application No. 62/452,458 filed Jan.
31, 2017 and entitled "CONTROL OF UNDER-FILL WITH A PACKAGING
SUBSTRATE HAVING AN INTEGRATED TRENCH FOR A DUAL-SIDED BALL GRID
ARRAY PACKAGE," and to U.S. Provisional Application No. 62/452,460
filed Jan. 31, 2017 and entitled "CONTROL OF UNDER-FILL USING AN
ENCAPSULANT FOR A DUAL-SIDED BALL GRID ARRAY PACKAGE," each of
which is expressly incorporated by reference herein in its entirety
for all purposes.
[0002] This application is also related to U.S. Pat. No. 9,381,529
issued Jul. 5, 2016 and entitled "SYSTEMS, DEVICES AND METHODS
RELATED TO PAINT RECIRCULATION DURING MANUFACTURE OF
RADIO-FREQUENCY MODULES," and to U.S. patent application Ser. No.
15/724,722 filed Oct. 4, 2017 and entitled "DUAL-SIDED
RADIO-FREQUENCY PACKAGE WITH OVERMOLD STRUCTURE," each of which is
expressly incorporated by reference herein in its entirety for all
purposes.
BACKGROUND
Field
[0003] The present disclosure generally relates to fabrication of
dual-sided packaged electronic modules.
Description of Related Art
[0004] The present disclosure relates to fabrication of packaged
electronic modules such as radio-frequency (RF) modules. In
radio-frequency applications, RF circuits and related devices can
be implemented in a packaged module. Such a packaged module can
then be mounted on a circuit board such as a phone board.
SUMMARY
[0005] According to a number of implementations, the present
disclosure relates to a method of fabricating a packaged
radio-frequency device. The method includes mounting components to
a first side of a packaging substrate. The method also includes
applying a film to a second side of a packaging substrate. The
method also includes mounting a lower component to the second side
of the packaging substrate after application of the film. The
method also includes under-filling the lower component mounted on
the second side of the packaging substrate with an under-fill
agent. The method also includes removing the film on the second
side of the packaging substrate. The method also includes mounting
solder balls to the second side of the packaging substrate after
removal of the film.
[0006] In some embodiments, the film covers contact pads of the
solder balls. In some embodiments, applying the film includes laser
cutting openings in a tape adhesive and mounting strips to the
film.
[0007] The method also includes applying the film includes covering
a first area of the second side of the packaging substrate while a
second area of the second side of the packaging substrate remains
uncovered by the film. In further embodiments, the first area
includes a plurality of contact pads for the solder balls. In
further embodiments, the second area includes a die area where the
lower-component is mounted.
[0008] In some embodiments, a size of a keep out zone is reduced by
application and removal of the film. In some embodiments, the
under-fill agent at least partially covers the film prior to
removal of the film. In further embodiments, the film prevents the
under-fill agent from coating contact pads of the solder balls.
[0009] According to a number of implementations, the present
disclosure relates to a method for manufacturing packaged
radio-frequency devices. The method includes applying a film to an
underside of a packaging substrate, the packaging substrate having
an upper side with one or more upper components mounted thereto,
the underside of the packaging substrate having a die area and a
contact pad area having a plurality of contact pads for
through-mold connections, application of the film including
covering the contact pad area with the film while leaving the die
area uncovered by the film. The method also includes after applying
the film, mounting one or more lower components within the die area
so that there is a gap between the one or more lower components and
the packaging substrate. The method also includes after mounting
the one or more lower components, depositing an under-fill material
on the packaging substrate so that the under-fill material
penetrates into the gap. The method also includes after depositing
the under-fill material, removing the film from the underside of
the packaging substrate.
[0010] In some embodiments, the method further includes mounting
through-mold connections to the underside of the packaging
substrate after removal of the film. In further embodiments, the
through-mold connections include solder balls. In yet further
embodiments, the method further includes singulating individual
units from the packaging substrate to yield a plurality of
dual-sided packages.
[0011] In some embodiments, the under-fill material includes a
sealing resin or an epoxy. In some embodiments, the method further
includes curing the under-fill material. In some embodiments,
applying the film includes laser cutting openings in a tape
adhesive and mounting strips to the film.
[0012] In some embodiments, the film is configured to control
distribution of the under-fill material during deposition of the
under-fill material. In further embodiments, the under-fill
material contacts the film. In further embodiments, removing the
film includes removing a portion of the under-fill material that
covers the film. In further embodiments, removing the film further
includes leaving the under-fill material deposited in the die
area.
[0013] According to a number of implementations, the present
disclosure relates to a method of fabricating a packaged
radio-frequency (RF) device. The method includes mounting
components to a first side of a packaging substrate. The method
also includes mounting a lower component to a second side of the
packaging substrate. The method also includes under-filling the
lower component mounted on the second side of the packaging
substrate with an under-filling agent. The method also includes
deflashing a portion of the under-filling agent. The method also
includes mounting solder balls to the second side of the packaging
substrate after the portion of the under-filling agent has been
deflashed.
[0014] In some embodiments, the portion of the under-filling agent
that is deflashed includes under-filling agent that coats contact
pads of the solder balls. In some embodiments, deflashing includes
removing a thin layer of the under-filling agent. In some
embodiments, a size of a keep out zone is reduced by deflashing a
portion of the under-filling agent prior to mounting the solder
balls.
[0015] In some embodiments, the second side of the packaging
substrate includes a plurality of contact pads for mounting the
solder balls. In further embodiments, the under-filling agent coats
a portion of at least one of the plurality of contact pads. In
further embodiments, deflashing includes removing the portion of
the under-filling agent that coats the portion of the at least one
of the plurality of contact pads.
[0016] According to a number of implementations, the present
disclosure relates to a method for manufacturing packaged
radio-frequency devices. The method includes mounting one or more
lower components on an underside of a packaging substrate so that
there is a gap between the one or more lower components and the
packaging substrate, the packaging substrate having an upper side
with one or more upper components mounted thereto, the underside of
the packaging substrate having a die area and a contact pad area
having a plurality of contact pads for through-mold connections.
The method also includes after mounting the one or more lower
components, depositing an under-fill material on the packaging
substrate so that the under-fill material penetrates into the gap.
The method also includes after depositing the under-fill material,
deflashing a portion of the under-fill material that covers one or
more targeted areas.
[0017] In some embodiments, the method further includes mounting
through-mold connections to the underside of the packaging
substrate after deflashing the portion of the under-fill material.
In further embodiments, the through-mold connections include solder
balls. In further embodiments, the method further includes
singulating individual units from the packaging substrate to yield
a plurality of dual-sided packages.
[0018] In some embodiments, the under-fill material includes a
sealing resin or an epoxy. In some embodiments, the method further
includes curing the under-fill material. In some embodiments, the
one or more targeted areas includes a portion of the contact pad
area. In some embodiments, deflashing includes removing a thin
layer of the under-fill material. In some embodiments, a size of a
keep out zone is reduced by deflashing a portion of the under-fill
material prior to mounting any through-mold connections to the
underside of the packaging substrate.
[0019] In some embodiments, the under-fill material coats a portion
of the contact pad area. In further embodiments, deflashing
includes removing the portion of the under-fill material that coats
the portion of the contact pad area.
[0020] According to a number of implementations, the present
disclosure relates to a packaging substrate for a packaged
radio-frequency (RF) device. The packaging substrate includes an
insulating material forming a first side and a second side, the
second side forming contact points for a ball grid array and a
lower component, the contact points exposing electrically
conducting material on the second side, the second side also
forming a dam on the insulating material forming an area to receive
under-fill agent during an under-fill process, the dam including a
feature configured to block the spread of under-fill material
during an under-fill process. The packaging substrate also includes
one or more conducting layers formed within the insulating
material. The packaging substrate also includes conducting paths
electrically coupling contact pads formed on the insulating
material to one of the one or more conducting layers.
[0021] In some embodiments, the dam is formed using a solder mask
during fabrication of the packaging substrate. In some embodiments,
the dam is photolithographically defined in the original substrate
manufacturing process. In some embodiments, the dam includes a
plurality of outcroppings. In some embodiments, the dam includes
continuous elevated structures. In some embodiments, the dam
includes a plurality of disconnected elongated raised features. In
some embodiments, the dam defines a keep out region that includes
contact points for the lower component and excludes contact points
for the ball grid array. In some embodiments, the dam is configured
to surround the contact points for the ball grid array.
[0022] According to a number of implementations, the present
disclosure relates to a method of fabricating a packaged
radio-frequency (RF) device. The method includes mounting
components to a first side of a packaging substrate. The method
also includes mounting a lower component to a second side of the
packaging substrate. The method also includes mounting solder balls
to the second side of the packaging substrate. The method also
includes forming a dam on a second side of the packaging substrate
after mounting the lower component and after mounting the solder
balls. The method also includes under-filling the lower component
mounted on the second side of the packaging substrate with an
under-fill material such that the under-fill material at least
partially contacts the dam formed on the packaging substrate.
[0023] In some embodiments, the dam is formed using an application
method that includes jetting or needle dispensing. In some
embodiments, the dam is configured to limit the distribution of the
under-fill material to maintain the under-fill material a targeted
distance from the solder balls while providing targeted coverage
under and around the lower component. In some embodiments, the
method further includes singulating individual units from the
packaging substrate to yield a plurality of dual-sided packages. In
some embodiments, the under-fill material includes a sealing resin
or an epoxy. In some embodiments, the method further includes
curing the under-fill material.
[0024] According to a number of implementations, the present
disclosure relates to a method of fabricating a packaged
radio-frequency (RF) device. The method includes mounting
components to a first side of a packaging substrate. The method
also includes forming a dam on a second side of the packaging
substrate. The method also includes mounting a lower component to a
second side of the packaging substrate after forming the dam. The
method also includes mounting solder balls to the second side of
the packaging substrate after forming the dam. The method also
includes under-filling the lower component mounted on the second
side of the packaging substrate with an under-fill material such
that the under-fill material at least partially contacts the dam
formed on the packaging substrate.
[0025] In some embodiments, the dam is formed using an application
method that includes screen printing, jetting, or needle
dispensing. In some embodiments, the dam is configured to limit the
distribution of the under-fill material to maintain the under-fill
material a targeted distance from the solder balls while providing
targeted coverage under and around the lower component. In some
embodiments, the method further includes singulating individual
units from the packaging substrate to yield a plurality of
dual-sided packages. In some embodiments, the under-fill material
includes a sealing resin or an epoxy. In some embodiments, the
method further includes curing the under-fill material.
[0026] According to a number of implementations, the present
disclosure relates to a packaging substrate for a packaged
radio-frequency (RF) device. The packaging substrate includes an
insulating material forming a first side and a second side, the
second side forming contact points for a ball grid array and a
lower component, the contact points exposing electrically
conducting material on the second side, the second side also
forming trenches in the insulating material that include a feature
to receive under-fill agent during an under-fill process. The
packaging substrate also includes one or more conducting layers
formed within the insulating material. The packaging substrate also
includes conducting paths electrically coupling contact pads formed
on the insulating material to one of the one or more conducting
layers.
[0027] In some embodiments, the trenches are formed using a solder
mask during fabrication of the packaging substrate. In some
embodiments, the trenches do not expose electrically conducting
material on the second side. In some embodiments, the trenches form
continuous trench structures. In some embodiments, the trenches
form a plurality of disconnected elongated trenches. In some
embodiments, the trenches form a plurality of voids in the
substrate. In some embodiments, the trenches define a keep out
region that includes contact points for the lower component and
excludes contact points for the ball grid array. In some
embodiments, the substrate is configured to be singulated to yield
a plurality of dual-sided packages.
[0028] According to a number of implementations, the present
disclosure relates to a method of fabricating a packaged
radio-frequency (RF) device. The method includes forming a trench
in insulating material of a packaging substrate, the trench formed
on an underside of the packaging substrate. The method also
includes mounting components to an upper side of the packaging
substrate. The method also includes mounting a lower component to
the underside of the packaging substrate. The method also includes
mounting solder balls to the underside of the packaging substrate.
The method also includes under-filling the lower component mounted
on the second side of the packaging substrate with an under-fill
material such that the under-fill material at least partially fills
the trench formed in the insulating material of the packaging
substrate.
[0029] In some embodiments, the trench is configured to limit the
distribution of the under-fill material to maintain the under-fill
material a targeted distance from the solder balls while providing
targeted coverage under and around the lower component. In some
embodiments, the method further includes singulating individual
units from the packaging substrate to yield a plurality of
dual-sided packages. In some embodiments, the under-fill material
includes a sealing resin or an epoxy. In some embodiments, the
method further includes curing the under-fill material. In some
embodiments, forming the trench includes using a solder mask
process. In some embodiments, the trench includes continuous trench
structures. In some embodiments, the trench includes a plurality of
disconnected elongated trenches. In some embodiments, the trench
includes a plurality of voids in the substrate. In some
embodiments, forming the trench does not penetrate through the
insulating material to a conductive layer. In some embodiments, the
trench does not include conductive material. In some embodiments,
the trench defines a keep out region that includes contact points
for the lower component and excludes contact points for the solder
balls.
[0030] According to a number of implementations, the present
disclosure relates to a method of fabricating a packaged
radio-frequency (RF) device. The method includes mounting
components to a first side of a packaging substrate. The method
also includes coating solder balls with a fluxing agent. The method
also includes attaching the solder balls to a second side of the
packaging substrate. The method also includes encapsulating the
solder balls with an encapsulant that forms an obtuse angle with
the packaging substrate. The method also includes attaching a lower
component to the second side of the packaging substrate. The method
also includes under-filling the lower component mounted on the
second side of the packaging substrate with an under-filling agent
such that the under-filling agent contacts the encapsulant.
[0031] In some embodiments, the encapsulant is a polymer. In some
embodiments, the encapsulant is not removed in a cleaning process
following attachment of the solder balls to the packaging
substrate. In some embodiments, the encapsulant forms an obtuse
angle to the solder balls. In some embodiments, the under-filling
agent contacts the encapsulant and not the solder balls. In some
embodiments, the method further includes singulating individual
units from the packaging substrate to yield a plurality of
dual-sided packages.
[0032] According to a number of implementations, the present
disclosure relates to a method for manufacturing packaged
radio-frequency devices. The method includes mounting one or more
lower components within a die area on an underside of a packaging
substrate so that there is a gap between the one or more lower
components and the packaging substrate, the packaging substrate
having an upper side with one or more upper components mounted
thereto, the underside of the packaging substrate having the die
area and a contact pad area having a plurality of contact pads for
through-mold connections. The method also includes mounting the
solder balls to the underside of the packaging substrate, the
solder balls being coated with a fluxing agent that leaves behind a
material that encapsulates the base of each solder balls, the
material forming an encapsulant. The method also includes after
mounting the solder balls, depositing an under-fill material on the
packaging substrate so that the under-fill material penetrates into
the gap.
[0033] In some embodiments, the encapsulant forms an obtuse angle
with a surface of the underside of the packaging substrate and with
a surface of the solder balls. In further embodiments, the obtuse
angle is configured to reduce a surface energy driving force for
capillary action of the under-fill material.
[0034] In some embodiments, the method further includes singulating
individual units from the packaging substrate to yield a plurality
of dual-sided packages. In some embodiments, the under-fill
material includes a sealing resin or an epoxy. In some embodiments,
the method further includes curing the under-fill material.
[0035] In some embodiments, the encapsulant is configured to
control distribution of the under-fill material during deposition
of the under-fill material. In further embodiments, the under-fill
material contacts the encapsulant.
[0036] In some embodiments, the material is configured so that it
is not removed during a cleaning process that follows solder ball
attach reflow. In further embodiments, the material is a polymer.
In some embodiments, the encapsulant is configured to reduce
capillary action causing the under-fill material to wick around the
solder balls.
[0037] According to a number of implementations, the present
disclosure relates to a packaging substrate for a packaged
radio-frequency (RF) device. The packaging substrate includes an
insulating material forming a first side and a second side, the
second side forming contact points for a ball grid array and a
lower component, the contact points exposing electrically
conducting material on the second side, the second side also
forming trenches in the insulating material that include a feature
to receive under-fill agent during an under-fill process, the
second side also forming a dam on the insulating material forming
an area to receive under-fill agent during an under-fill process,
the dam including a feature configured to block the spread of
under-fill material during an under-fill process. The packaging
substrate also includes one or more conducting layers formed within
the insulating material. The packaging substrate also includes
conducting paths electrically coupling contact pads formed on the
insulating material to one of the one or more conducting
layers.
[0038] According to a number of implementations, the present
disclosure relates to a method of fabricating a packaged
radio-frequency (RF) device. The method includes forming a trench
in insulating material of a packaging substrate, the trench formed
on an underside of the packaging substrate. The method also
includes forming a dam on the underside of the packaging substrate.
The method also includes mounting components to an upper side of a
packaging substrate. The method also includes mounting a lower
component to the underside of the packaging substrate. The method
also includes mounting solder balls to the underside of the
packaging substrate. The method also includes under-filling the
lower component mounted on the second side of the packaging
substrate with an under-fill material such that the under-fill
material at least partially flows into the trench or contacts the
dam formed on the packaging substrate.
[0039] According to a number of implementations, the present
disclosure relates to a method of fabricating a packaged
radio-frequency (RF) device. The method includes forming a dam on
an underside of the packaging substrate. The method also includes
mounting components to an upper side of the packaging substrate.
The method also includes mounting a lower component to the
underside of the packaging substrate. The method also includes
under-filling the lower component mounted on the second side of the
packaging substrate with an under-fill material such that the
under-fill material at least partially flows into the trench or
contacts the dam formed on the packaging substrate. The method also
includes deflashing a portion of the under-filling agent. The
method also includes mounting solder balls to the underside of the
packaging substrate.
[0040] According to a number of implementations, the present
disclosure relates to a method of fabricating a packaged
radio-frequency (RF) device. The method includes forming a trench
in insulating material of a packaging substrate, the trench formed
on an underside of the packaging substrate. The method also
includes mounting components to an upper side of the packaging
substrate. The method also includes mounting a lower component to
the underside of the packaging substrate. The method also includes
under-filling the lower component mounted on the second side of the
packaging substrate with an under-fill material such that the
under-fill material at least partially flows into the trench or
contacts the dam formed on the packaging substrate. The method also
includes deflashing a portion of the under-filling agent. The
method also includes mounting solder balls to the underside of the
packaging substrate.
[0041] For purposes of summarizing the disclosure, certain aspects,
advantages and novel features have been described herein. It is to
be understood that not necessarily all such advantages may be
achieved in accordance with any particular embodiment. Thus, the
disclosed embodiments may be carried out in a manner that achieves
or optimizes one advantage or group of advantages as taught herein
without necessarily achieving other advantages as may be taught or
suggested herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0042] FIG. 1 illustrates a dual-sided package having a shielded
package and a lower component mounted thereto.
[0043] FIG. 2 illustrates another example of a dual-sided package
having one or more lower components that can be mounted under a
shielded package, generally within a volume defined on an underside
of the shielded package.
[0044] FIGS. 3A, 3B, 3C, 3D, 3E, 3F, 3G, 3H, and 3I illustrate a
typical process flow for fabricating a dual-sided ball grid array
package.
[0045] FIGS. 4A, 4B, 4C, 4D, 4E, and 4F illustrate a modified
fabrication process that uses a film to control distribution of an
under-fill material.
[0046] FIGS. 5A, 5B, 5C, and 5D illustrate a modified fabrication
process using under-fill deflash to control the distribution of an
under-fill material.
[0047] FIGS. 6A, 6B, 6C, and 6D illustrate a modified fabrication
process that includes using a dam to contain an under-fill
material.
[0048] FIGS. 7A and 7B illustrate a modified fabrication process
that uses a substrate with trenches on the underside of the
substrate.
[0049] FIGS. 8A and 8B illustrate a modified fabrication process
using encapsulant to control the distribution of an under-fill
material.
[0050] FIGS. 9A and 9B illustrate a panel with a dam or a series of
raised features in conjunction with a trench or a series of
valleys, holes, or the like in a substrate, wherein the dam and the
trench are configured to control the distribution of an under-fill
material.
DETAILED DESCRIPTION OF SOME EMBODIMENTS
[0051] The headings provided herein, if any, are for convenience
only and do not necessarily affect the scope or meaning of the
claimed invention.
Overview
[0052] Described herein are technologies related to fabrication of
dual-sided packaged electronic modules, such as radio-frequency
modules, and devices, systems, and methods to control the
distribution of an under-fill material between one or more
components and a packaging substrate. The disclosed technologies
include applying a film to targeted areas on the packaging
substrate prior to under-filling one or more components and prior
to attaching solder balls. By applying the film to the packaging
substrate prior to under-filling, the region that receives
under-fill material can be controlled to a greater degree. After
under-filling, the film can be removed to expose clean contact pads
for the solder balls. Furthermore, because the solder balls are not
present during under-fill, there is little capillary action drawing
material away from the components being under-filled. This can
advantageously reduce the frequency of voids under the components
being under-filled. Accordingly, the disclosed systems, devices,
and methods control under-fill for dual-sided ball grid array
packages using a film prior to attaching solder balls of the ball
grid array.
[0053] The disclosed technologies also include under-filling one or
more components and deflashing a portion of the under-fill to
remove under-fill material prior to attaching solder balls. By
adding the deflashing step and adding solder balls after
deflashing, the region that has under-fill material can be
controlled to a greater degree. The deflashing step removes a thin
layer of under-fill material that may have coated contact pads for
the ball grid array. Furthermore, because the solder balls are not
present during under-fill, there is little capillary action drawing
material away from the components being under-filled. This can
advantageously reduce the frequency of voids under the components
being under-filled. Accordingly, the disclosed systems, devices,
and methods control under-fill for dual-sided ball grid array
packages using under-fill deflash prior to attaching solder balls
of the ball grid array.
[0054] The disclosed technologies also include using a dam on a
packaging substrate. The dam on the packaging substrate is
configured to prevent or limit the flow of a capillary under-fill
material. For example, the dam can form a controlled area so that
the capillary under-fill material fills or flows substantially free
within this area but does not flow outside of the area. This can
prevent or limit the capillary under-fill material from flowing
onto or contacting other components or elements on the packaging
substrate, such as solder balls of a ball-grid array. Accordingly,
the disclosed systems, devices, and methods control under-fill for
dual-sided ball grid array packages using a dam on a packaging
substrate.
[0055] The disclosed technologies also include forming a trench in
a packaging substrate. The trench in the packaging substrate is
configured to prevent or limit the flow of a capillary under-fill
material. For example, the trench can form a controlled area so
that the capillary under-fill material fills or flows substantially
free within this area but does not flow outside of the area. This
can prevent or limit the capillary under-fill material from flowing
onto or contacting other components or elements on the packaging
substrate, such as solder balls of a ball-grid array. Accordingly,
the disclosed systems, devices, and methods control under-fill for
dual-sided ball grid array packages using a trench on a packaging
substrate.
[0056] The disclosed technologies also include using an encapsulant
on solder balls to limit distribution of an under-fill agent. The
encapsulant can be used in the ball attach process. The fluxing
agent leaves behind a material that encapsulates the base of each
solder ball. The encapsulant forms an obtuse angle with the
substrate surface and with the ball surface. This reduces the
tendency of the under-fill material to wick around the solder balls
by capillary action. This can prevent or limit the capillary
under-fill material from flowing onto or contacting other
components or elements on the packaging substrate, such as solder
balls of a ball-grid array. Accordingly, the disclosed systems,
devices, and methods control under-fill for dual-sided ball grid
array packages using an encapsulant on the solder balls.
[0057] In radio-frequency (RF) applications, RF circuits and
related devices can be implemented in a packaged module. Such a
packaged module can then be mounted on a circuit board such as a
phone board. Certain packaged modules can include dual-sided
packages, with components mounted over and under a packaging
substrate. Such packaged modules can include an array of solder
balls, or a ball grid array, on an underside of the packaging
substrate, which collectively may be referred to as a dual-sided
ball grid array (DS-BGA).
[0058] FIG. 1 illustrates a dual-sided package 100 having a
shielded package 102 and a lower component 104 mounted thereto. For
the purpose of description, a lower side of the shielded package
102 can include a side 103 of a packaging substrate that is to be
mounted onto a circuit board such as a phone board. Although not
shown separately in FIG. 1, it will be understood that the shielded
package 102 can include such a packaging substrate and one or more
upper components mounted on its upper side (when oriented as shown
in FIG. 1). Accordingly, the dual-sided property can include such
upper component(s) mounted over the substrate and lower
component(s) mounted under the substrate.
[0059] The package can be shielded using any suitable shielding
method. For example, the package 100 can be shielded using a
plurality of shielding wires that are electrically coupled to a
ground plane within the packaging substrate. The package 100 can be
shielded using a conformal coating that is electrically coupled to
a ground plane within the packaging substrate. Any suitable
combination of features can be used to define a shielded volume or
region. Such configurations can be implemented to provide shielding
functionality between regions within and outside of the shielded
package 100, and/or between regions that are both within the
shielded package 100.
[0060] For the purpose of description, it will be understood that a
lower component can include any device that can be mounted on the
substrate and/or the circuit board. Such a device can be an active
radio-frequency (RF) device or a passive device that facilitates
processing of RF signals. By way of non-limiting examples, such a
device can include a die such as a semiconductor die, an integrated
passive device (IPD), a surface-mount technology (SMT) device, and
the like. In some embodiments, the lower component as described
herein can be electrically coupled to the one or more upper
components through, for example, the substrate.
[0061] FIG. 2 illustrates another example of a dual-sided package
200 having one or more lower components 204 that can be mounted
under a shielded package 202, generally within a volume defined on
an underside of the shielded package. In some embodiments, a set of
through-mold connections (e.g., one or more through-mold
connections) may be implemented, formed, located, and/or positioned
on the underside (e.g., side 103 illustrated in FIG. 1) of the
shielded package 202. The set of through-mold connections may
define a volume on the underside of the shielded package 202. A
volume 208 under a shielded package 202 is shown to be defined by
the underside of the shielded package 202 and solder balls 206 of a
ball grid array (BGA). The BGA may be a set of through-mold
connections. For example, each solder ball 206 of the BGA may be a
through-mold connection in the set of through-mold connections.
Other examples of through-mold connections include, but are not
limited to solder balls, pillars, columns, posts, pedestals, etc.
The through-mold connections described herein may also be referred
to as contact features. The solder balls 206 allow the dual-sided
package 200 to be mounted on a circuit board 210 such as a phone
board. The solder balls 206 can be configured so that when mounted
to the circuit board 210, there is sufficient vertical space
between the upper surface of the circuit board 210 and the lower
surface of the shielded package 202 for the lower component 204.
The volume 208 can be at least partially filled with an over-mold
205. The over-mold 205 substantially encapsulates the lower
component 204. In certain embodiments, at least a portion of the
solder balls 206 may be exposed through the over-mold 205. Exposing
at least a portion of the solder balls 206 may provide a connection
(e.g., an electrical and/or thermal connection) through the
over-mold 205. For example, the solder balls 206 may provide a
connection (e.g., an electrical connection) to the lower component
204 and/or upper components 224, 226 in the shield package 202. In
various embodiments, solder (or other conductive material) may be
applied to the exposed portion of the solder balls 206 to form a
connection (e.g., electrical connection) with the circuit board
210. The over-mold 205 may also be referred to as an over-mold
structure. In some embodiments, the over-mold 205 and/or the solder
balls 206 (e.g., the exposed portions of the solder balls 206) may
form a land grid array (LGA) type/style package.
[0062] A close-up view of the solder ball 206 is also illustrated
in FIG. 2. As illustrated in the close-up view of the solder ball
206, the bottom of the shielded package includes a pad 215. The pad
215 may be a metallic pad (or some other material) that may provide
electrical and/or thermal conductivity between the solder ball 206
and components of the shield package 202 and/or the lower component
204. Solder mask 214 may be deposited over portions of the pad 215
to define a location where the solder ball 206 may be formed. The
solder ball 206 may be formed (e.g., implemented, formed, dropped,
etc.) on top of the pad 215 and the solder mask 214.
[0063] The dual-sided package 200 may be installed on the circuit
board 210 using the solder ball 206. The solder ball 206 may be
attached to the circuit board 210 (e.g., may be installed, mounted,
fixed, etc., to the circuit board 210) via connection 216. As
illustrated in the close-up view of the solder ball 206, the
connection 216 may include solder material 221 and pad 219. The
solder material 221 may be solder material from the solder ball 206
that is deposited/melted onto the pad 219 when the dual-sided
package 200 is attached to the circuit board. For example, during a
reflow process, heat may be applied to melt at least a portion of
the solder ball 206 to form the solder material 221. The solder
material 221 may also include additional material that is formed,
implemented, deposited, etc., over the solder ball 206. The pad 219
may be part of the circuit board 210. The pad 219 may provide
electrical and/or thermal conductivity between the dual-sided
package 200 and other components/circuits attached to the circuit
board 210 (not illustrated in the figures). In some embodiments,
the pad 219 may include solder material.
[0064] The over-mold 205 has a surface 212 (facing downward toward
the circuit board 210). In some embodiments, the surface 212 may
not contact (e.g., may not physically touch) the surface 213 of the
circuit board 210. For example, a gap 209 may be present between
the surface 212 and the surface 213. In some implementations, the
gap 209 may help protect the lower component 204 from damage when
there are linear displacements of the dual-sided package 200 due to
flexing or dropping. For example, the gap 209 may help protect the
lower component 204 from damage as the dual-sided package 200 is
installed on the circuit board 200 (e.g., may prevent the lower
component 204 from contacting the surface 213 of the circuit board
210 during installation/mounting of the dual-sided package). The
portion of the over-mold material 205 that covers the lower
component 204 may provide additional protection from damage when
there are linear displacements of the dual-sided package 200 due to
flexing or dropping. For example, the over-mold material 205 may
also prevent the lower component 204 from contacting the surface
213 of the circuit board 210 during installation/mounting of the
dual-sided package. In some embodiments, the gap 209 may also allow
the dual-sided package 200 to adapt to process/manufacturing
variations when the dual-sided package 200 is installed on the
circuit board 210. For example, different temperatures may be used
to melt the solder ball 206 during installation of the dual-sided
package. The gap 209 may help ensure that the dual-sided package
200 is properly installed by providing enough distance between the
surface 212 (of over-mold 205) and the surface 213 (of circuit
board 210) while still allowing the solder material of the solder
ball 206 to properly bond with the pad 219 of the circuit board
210. In some embodiments, although the over-mold 205 and/or the gap
209 may prevent the component 204 from contacting the surface 213
(of the circuit board 210), the dual-sided package 200 and/or the
component 204 may still operate/function properly even if the
component 204 does contact the surface 213. For example, the
component 204 may remain undamaged and/or operable even after
contacting the surface 213 of the circuit board 210.
[0065] The dual-sided ball grid array package 200 can include a
packaging substrate 222 (e.g., a laminate substrate) and a
plurality of components mounted thereon. For example, a first
component 224 can be mounted on the upper surface of the packaging
substrate 222, and electrical connections between the component 224
and the packaging substrate 222 can be facilitated by, for example,
wire-bonds 228. In another example, a second component 226 is shown
to be mounted on the upper surface of the packaging substrate 222
in a die-attach configuration. Electrical connections between the
component 226 and the packaging substrate 222 can be facilitated
by, for example, die-attach features.
[0066] In some embodiments, an under-fill can be provided between
the lower component 204 and an underside of the dual-sided package
200. An under-fill 230 can be provided between the lower component
204 and the underside of the package 200 to provide, for example, a
more secure mounting of the lower component 204.
[0067] Examples related to fabrication of dual-sided packages
having similar configurations are described herein in greater
detail. It will be understood that although such examples are
described in the context of solder balls, other types of connection
features that provide sufficient vertical space can also be
utilized. Although the embodiments, examples, configurations,
and/or implementations disclosed herein may refer to solder balls
and/or a BGA, one having ordinary skill in the art understands that
solder balls and/or a BGA are examples of through-mold connections.
One having ordinary skill in the art understands that other types
of through-mold connections (e.g., pillars, columns, etc.,) may be
used to define a volume on an underside of a shielded package and
an over-mold may be implemented in the volume (on the underside of
the shielded package). In some embodiments, a through-mold
connection (or a set of through-mold connections) may be any
structure and/or component that may be used to define a volume on
the underside of a shielded package and/or may be used to support
the shielded package above a surface.
Examples of Fabricating Dual-Sided Ball Grid Array Packages
[0068] In a dual-sided ball grid array package structure, a zone is
required between solder ball(s) and integrated circuit chips, dies,
or other such components. This zone (sometimes referred to as a
"keep out" zone) is a design rule that calls out a targeted minimum
distance between solder ball and component. The keep out zone
facilitates meeting manufacturing quality and reliability
requirements. Defects such as voids under the component (e.g., an
IC chip) where there is no under-fill material, or contamination of
the solder balls with undesired material can occur if the keep out
zone design rule is violated. It is advantageous to reduce the size
of the keep out zone because it can enhance product performance
and/or reduce package size. For example, the overall package size
can be reduced and/or the chip size can be increased if the size of
the keep out zone can be reduced. Decreasing the package size or
increasing chip size may result in additional or improved
functionality per unit area on the final product motherboard to
which the dual-sided ball grid array package is mounted.
Accordingly, described herein are systems, devices, and methods
that advantageously reduce the keep out zone between solder balls
and the IC chip in a dual-sided ball grid array package. This
results in greater functionality per unit area when the package is
mounted to the final product motherboard.
[0069] Typical fabrication techniques attempt to reduce or minimize
the IC chip-to-solder ball keep out zone by controlling the
capillary under-fill dispense process. This may be controlled
through the needle selection, the dispense volume, the number of
dispense passes, and/or the dispense temperature. By way of
example, the keep out zone on the dispense side of the chip may be
about 700 .mu.m, and may be about 200 .mu.m on the other three
sides of the chip.
[0070] FIGS. 3A-3I illustrate a process flow for fabricating a
dual-sided ball grid array package. FIGS. 3A-3F illustrate a
process for completing a top side assembly of a laminate strip
(e.g., surface mount, die attach, wire bond, molding, and marking).
FIGS. 3G-3I illustrate a process for completing a bottom side
assembly and forming individual packages through singulation.
Optionally, a conformal shield material stack may be applied to
individual packages. As illustrated in FIGS. 4A-4F, the present
disclosure improves on this fabrication process by applying a film
to the bottom side of the packaging substrate prior to
under-filling to protect the contact pads of the solder balls of
the ball grid array and to control the distribution of the
under-filling material. In addition, as illustrated in FIGS. 5A-5D,
the present disclosure improves on this fabrication process by
under-filling and deflashing a portion of the under-fill material
prior to adding the solder balls of the ball grid array. Moreover,
as illustrated in FIGS. 6A-6D, the present disclosure improves on
this fabrication process by forming a dam on the substrate to
impede or prevent the capillary under-fill material from flowing
into the solder balls. Furthermore, as illustrated in FIGS. 7A and
7B, the present disclosure improves on this fabrication process by
forming a trench in the substrate to impede or prevent the
capillary under-fill material from flowing into the solder balls.
Additionally, as illustrated in FIGS. 8A and 8B, the present
disclosure improves on this fabrication process by using an
encapsulant on the solder balls to impede or prevent the under-fill
material from flowing onto the solder balls.
[0071] FIGS. 3A-3I illustrate various stages of a fabrication
process in which dual-sided features can be implemented in a panel
format having an array of to-be-separated units, and separation of
the array into individual units (also referred to as singulation).
Although described in the context of BGA-based dual-sided packages,
it will be understood that one or more features of the fabrication
technique of FIGS. 3A-3I, 4A-4F, 5A-5D, 6A, 6B, 7A, 7B, 8A, and 8B
can also be implemented for fabrication of dual-sided packages
having other types of mounting features. In some implementations,
the disclosed fabrication processes can be utilized for
manufacturing dual-sided packages described herein and in U.S.
Patent No. 9,381,529 and U.S. Patent Application No. 15/724,722
(each of which has been expressly incorporated by reference
herein).
[0072] FIG. 3A illustrates a cross-section view of a panel 300
having a plurality of to-be-singulated units. For example,
singulation can occur at boundaries depicted by dashed lines 360 so
at to yield singulated individual units. The panel 300 includes a
substrate 305 on which components are to be mounted. The substrate
305 can be a laminate substrate, a ceramic substrate (e.g., a
low-temperature co-fired ceramic substrate), or the like. The
substrate 305 can include surface features 310 that may provide
mechanical support. The panel 300 includes conductive material 315
that is configured to provide electrical connections between
conductive layers, surface-mount devices, chips, solder balls, and
the like. The conductive material 315 can form contact pads on the
upper and lower sides of the substrate 305 to provide electrical
contact points for surface mount devices, chips, solder balls,
pillars, any combination of these, or the like. Vias can be formed
in the substrate where the conductive material 315 provides an
electrical connection between conductive layers in the panel
300.
[0073] FIG. 3B illustrates mounting of surface mount technology
(SMT) devices 320 such that conductive points on the devices 320
are electrically coupled to contact pads formed by the conductive
material 315 on the panel 300. By way of example, solder paste can
be applied on the substrate 305 to allow mounting of one or more
SMT devices 320. A reflow operation can be performed to melt the
solder paste to solder the one or more SMT devices on their
respective contact pads. Solder residue from the reflow operation
can be removed by running the substrates through a solvent or
aqueous cleaning step, for example.
[0074] FIG. 3C illustrates mounting of a die or chip 325. By way of
example, adhesive 326 can be applied on one or more selected areas
on the substrate 305. The die 325 can be positioned on the selected
area with adhesive applied thereon. The adhesive 326 between the
die 325 and the die-mounting area can be cured to secure the die
325.
[0075] FIG. 3D illustrates forming electrical connections between
the die 325 and contact pads using wirebonds 327. The wirebonds 327
can provide electrical connections for signals and/or power to and
from one or more circuits of the die 325.
[0076] FIG. 3E illustrates forming an over-mold 330 over the SMT
component(s) 320, die(s) 325, and any other upper component on the
substrate 305. By way of example, molding compound can be
introduced from one or more sides of a molding volume to form an
upper over-molded volume 330. In some embodiments, the over-mold
330 may completely encapsulate the upper components 320, 325.
[0077] FIG. 3F illustrates an optional process of marking the
over-mold 330. By way of example, marking may be accomplished using
laser etching or similar techniques.
[0078] FIG. 3G illustrates attaching a lower component 335 to the
underside (which may face upward during fabrication) of the
substrate 305. In addition, an array of solder balls 340 can be
formed on the underside of the substrate 305. It will be understood
that the lower component 335 may be attached for each unit after
the array of solder balls 340 is formed, or vice versa. It shall
also be understood that the lower component 335 and the array of
solder balls 340 may be attached, implemented, and/or formed
substantially simultaneously.
[0079] FIG. 3H illustrates filling a gap between the lower
component 335 and the substrate 305 with an under-fill agent 345 or
an under-fill material (also referred to as under-filling). By way
of example, an under-fill material 345, such as a sealing resin or
epoxy, can be deposited on the substrate 305 and the under-fill
material 345 can penetrate into the gap between the lower component
335 and the substrate 305 by capillary forces. The coating shape
and amount of under-fill agent 345 vary depending on the package
size, pitch, and gap. The under-fill material 345 can be cured to
provide mechanical support to the lower component 335, to provide
advantageous thermal properties, to improve solder-ball bonding
reliability under external stresses, and the like.
[0080] FIG. 3I illustrates singulating individual units to yield a
plurality of dual-sided packages 350 substantially ready to be
mounted to circuit boards. Controlling Under-Fill Using a Film
[0081] To better control the size of the keep out area, the
fabrication process illustrated in FIGS. 3A-3I can be improved by
applying a film to the bottom side of the packaging substrate prior
to adding the solder balls and prior to under-filling the lower
component. Upon removal of the film, the solder balls can be added.
The film protects the contact pads of the solder balls and controls
the distribution of the under-filling agent.
[0082] FIGS. 4A-4F illustrate a modified fabrication process,
replacing steps illustrated in FIGS. 3G and 3H. FIG. 4A illustrates
a substrate 305 with a die area 337 (e.g., for mounting one or more
lower components) and a plurality of solder ball contact pads 342.
A film 447 can be added to the substrate 305 to protect the solder
ball contact pads 342 and to expose the die area 337 for mounting
one or more lower components. The illustration on the left is shown
without the film 447 while the illustration on the right is shown
with the film 447.
[0083] FIG. 4B illustrates the substrate 305 with the film 447
covering the contact pads 342 prior to addition of the lower
component 335 and solder balls 340 and prior to under-filling the
lower component 335. The film can be used to control the
distribution of the under-filling agent, thereby making it possible
to reduce the size of the keep out zone.
[0084] The process for applying the film 447 to the bottom side of
the packaging substrate 305 can be similar to the process used in
shielding DS-BGA packages. For example, openings can be laser cut
in a tape adhesive. Strips can then be mounted to the film so that
the film can protect the contact pads of the ball grid array from
under-fill runout.
[0085] FIG. 4C illustrates that, after application of the film 447,
the lower component 335 can be added, as described herein with
reference to FIG. 3G. However, the solder balls of the ball grid
array are not mounted to the substrate 305 as described in FIG.
3G.
[0086] FIG. 4D illustrates that, after reflow and cleaning, the
under-fill agent 345 can be applied as described herein with
reference to FIG. 3H. However, there is a lack of capillary action
drawing the under-fill material 345 toward the solder balls because
the solder balls are not yet installed. This can reduce the
occurrence of under-fill voids under the lower component 335. In
addition, the film 447 prevents the under-fill material 345 from
coating the solder ball contact pads 342.
[0087] FIG. 4E illustrates an additional process step of removing
the film 447. Removing the film 447 can prevent the under-fill
material 345 from coating contact pads 342 of the solder balls
and/or can remove any under-fill material 345 that would have
coated those contact pads 342. In this way, the size and extent of
the keep out zone can be controlled.
[0088] FIG. 4F illustrates that, after removal of the film 447, the
solder balls 340 can be added as described in FIG. 3G. The process
can then proceed to reflow again and then to singulate the
individual units, as described herein with reference to FIG.
3I.
Controlling Under-Fill Using Deflashing
[0089] To better control the size of the keep out area, the
fabrication process illustrated in FIGS. 3A-3I can be improved by
adding the solder balls after under-filling the lower component and
deflashing excess under-fill to control the distribution of
under-fill agent.
[0090] FIGS. 5A-5D illustrate a modified fabrication process,
replacing steps described herein with reference to FIGS. 3G and 3H.
In FIG. 5A, a lower component 335 is added as described in FIG. 3G.
However, the solder balls of the ball grid array are not mounted to
the substrate 305 as described in FIG. 3G. In FIG. 5B, the
under-fill material 345 is applied as described in FIG. 3H.
However, there is a lack of capillary action drawing the under-fill
material 345 toward the solder balls because the solder balls are
not yet installed. This can reduce the occurrence of under-fill
voids under the lower component 335.
[0091] FIG. 5C illustrates an additional process step of deflashing
the under-fill material 345. Deflashing is configured to remove a
thin layer of under-fill material from targeted locations 347 on
the substrate. For example, deflashing can remove under-fill
material that may have coated the contact pads for the solder
balls. In this way, the size and extent of the keep out zone can be
controlled. FIG. 5D illustrates that, after deflashing, the solder
balls 340 can be added as described in FIG. 3G.
Controlling Under-Fill Using a Dam
[0092] To better control the size of the keep out area, the
fabrication process illustrated in FIGS. 3A-3I can be improved by
forming a dam or a series of raised features on the substrate 305,
wherein the dam or similar features is configured to control the
distribution of under-fill agent in the process step illustrated in
FIG. 3H.
[0093] As illustrated in FIGS. 6A-6C, a panel 600 can be provided
wherein the substrate 605 includes a dam 607 on the underside of
the substrate 605, wherein the dam 607 can be an integral part of
the substrate 605 or formed on the substrate 605 at a later time.
The dam 607 provides a way to control the distribution of the
under-fill agent during manufacturing of the disclosed double-sided
ball grid array packages. The dam 607 contains the capillary
under-fill material and may prevent it from contacting or
contaminating the solder balls 340. The dam 607 can provide a
repeatable volume of material to flow under the lower component 335
(e.g., a die), which reduces the frequency of voiding under the
lower component 335. Although the dam 607 is illustrated on a
single side of the solder balls 340, it is to be understood that
the dam 607 can be configured to surround the solder balls 340. For
example, the dam 607 can be configured to have raised features on a
plurality of sides of the solder balls 340. The dam 607 can
surround individual solder balls 340 and/or surround or enclose the
area that contains the solder balls 340.
[0094] The substrate 605 can be a laminate substrate, a ceramic
substrate (e.g., a low-temperature co-fired ceramic substrate), or
the like. The substrate 605 can include surface features 610 that
may provide mechanical support. The panel 600 includes conductive
material 615 that is configured to provide electrical connections
between conductive layers, surface-mount devices, chips, solder
balls, and the like. The conductive material 615 can form contact
pads on the upper and lower sides of the substrate 605 to provide
electrical contact points for surface mount devices, chips, solder
balls, pillars, any combination of these, or the like. Vias can be
formed in the substrate 605 where the conductive material 615
provides an electrical connection between conductive layers in the
panel 600. The dam 607 can form continuous elevated structures, a
plurality of disconnected elongated raised features, or a plurality
of outcroppings in the substrate 605. The dam 607 can define one or
more keep out areas on the underside of the substrate 605.
[0095] FIG. 6A illustrates that the dam 607 forms part of the
substrate 605. In some embodiments, the dam 607 can be formed
during an additional solder mask process during fabrication of the
substrate 605. In some embodiments, the panel 600 includes a
substrate 605 having insulating material forming an upper side and
a lower side. The substrate 605 forms voids in which conducting
material electrically couples contact pads to conductive layers or
other contact pads. The substrate 605 forms a dam 607 (e.g.,
elevated features, connected raised features, disconnected raised
features, etc.) in the insulating material to form a feature that
can block the spread of under-fill material during an under-fill
process. The dam 607 can be photolithographically defined during
the original substrate manufacturing process. Then, when assembling
the bottom side of the panel 600, the process flow illustrated in
FIGS. 3A-3I can be used.
[0096] FIG. 6B illustrates that the dam 607 can be added to the
substrate 605 during fabrication after the ball and die attach
process steps, illustrated in FIG. 3G. To apply the dam 607,
jetting or needle dispensing may be used.
[0097] FIG. 6C illustrates that the dam 607 can be added to the
substrate 605 during fabrication before the ball and die attach
process steps, illustrated in FIG. 3G. To apply the dam 607, screen
printing, jetting, or needle dispensing may be used.
[0098] FIG. 6D illustrates the modified process of under-filling in
the presence of the dam 607, compared to the under-filling process
illustrated in FIG. 3H. The dam 607 limits the distribution of the
under-fill material 345 to maintain the under-fill material 345 a
targeted or desired distance from the solder balls 340 while still
providing targeted coverage under and around the lower component
335.
Controlling Under-Fill Using a Trench
[0099] To better control the size of the keep out area, the
fabrication process illustrated in FIGS. 3A-3I can be improved by
forming a trench or a series of valleys, holes, or the like in the
substrate 305, wherein these trenches or similar features are
configured to control the distribution of under-fill agent in the
process step illustrated in FIG. 3H.
[0100] As illustrated in FIG. 7A, a panel 700 can be provided
wherein the substrate 705 includes trenches 708 on the underside of
the substrate 705. The trenches provide a way to control the
distribution of the under-fill agent during manufacturing of the
disclosed double-sided ball grid array packages. The substrate 705
can be a laminate substrate, a ceramic substrate (e.g., a
low-temperature co-fired ceramic substrate), or the like. The
substrate 705 can include surface features 710 that may provide
mechanical support. The panel 700 includes conductive material 715
that is configured to provide electrical connections between
conductive layers, surface-mount devices, chips, solder balls, and
the like. The conductive material 715 can form contact pads on the
upper and lower sides of the substrate 705 to provide electrical
contact points for surface mount devices, chips, solder balls,
pillars, any combination of these, or the like. Vias can be formed
in the substrate 705 where the conductive material 715 provides an
electrical connection between conductive layers in the panel
700.
[0101] To form the trenches 708, vias can be formed in the
substrate 705, but instead of providing conductive paths between
conductive layers, the vias for the trenches 708 can provide a void
in the substrate structure to receive under-fill agent during the
under-fill processing step. By way of example, the trench 708 can
be formed during a solder mask process during fabrication of the
substrate 705. The trenches 708 can form continuous trench
structures, a plurality of disconnected elongated trenches, or a
plurality of voids or holes in the substrate 705. The trenches 708
can define one or more keep out areas on the underside of the
substrate 705.
[0102] In some embodiments, the panel 700 includes a substrate 705
having insulating material forming an upper side and a lower side.
The substrate 705 forms voids in which conducting material
electrically couples contact pads to conductive layers or other
contact pads. The substrate 705 forms trenches 708 (e.g., elongated
voids) in the insulating material to form a feature that can
receive under-fill material during an under-fill process. In some
embodiments, the trenches 708 do not include conductive material or
do not penetrate to a conductive layer.
[0103] FIG. 7B illustrates the modified process of under-filling in
the presence of trenches 708 in the substrate 705, compared to the
under-filling process illustrated in FIG. 3H. The trenches 708
limit the distribution of the under-fill material 345 to maintain
the under-fill material 345 a targeted or desired distance from the
solder balls 340 while still providing targeted coverage under and
around the lower component 335.
Controlling Under-Fill Using Encapsulant
[0104] To better control the size of the keep out area, the
fabrication process illustrated in FIGS. 3A-3I can be improved by
using a special material during the ball attach process illustrated
in FIG. 3G. As illustrated in FIG. 8A, a fluxing agent can be used
on the solder balls 340 that leaves behind a material which
encapsulates the base of each solder ball 340, forming encapsulant
842. This material may be a polymer. This material can be
configured so that it is not removed during a cleaning process that
follows solder ball attach reflow. The encapsulant 842 forms an
obtuse angle with the surface of the substrate 305 and with the
surface of the solder balls 340.
[0105] When the under-fill material 845 is dispensed in the process
step illustrated in FIG. 8B, it no longer has a tendency to wick
around the solder balls 340 by capillary action. The obtuse angles
formed by the encapsulant 842 reduce the surface energy driving
force for capillary action. This reduces or prevents the under-fill
material from flowing around the solder balls 340. Instead, the
under-fill material 345 primarily flows under the lower component
335 (e.g., an IC chip).
Controlling Under-Fill Using a Combination of Features
[0106] To better control the size of the keep out area, the
fabrication process illustrated in FIGS. 3A-3I can be improved by
combining features and techniques described herein with respect to
FIGS. 4A-4F, 5A-5D, 6A-6D, 7A, 7B, 8A, and 8B. For example, a dam
(e.g., as described herein with reference to FIGS. 6A-6D) can be
used in combination with a trench (e.g., as described herein with
reference to FIGS. 7A and 7B), which is illustrated in FIGS. 9A and
9B. Other combinations can be implemented as well. For example, the
dam can be used in conjunction with a film, deflashing, trench,
and/or an encapsulant. As another example, the trench can be used
in conjunction with a film, deflashing, dam, and/or an encapsulant.
Similarly, deflashing can be used in conjunction with a film, dam,
trench, and/or an encapsulant. As another example, the film can be
used in conjunction with deflashing, dam, trench, and/or an
encapsulant. Likewise, encapsulant can be used in conjunction with
a film, dam, trench, and/or deflashing.
[0107] FIG. 9A illustrates a panel 900 with a dam 907 or a series
of raised features in conjunction with a trench 908 or a series of
valleys, holes, or the like in a substrate 905, wherein the dam 907
and the trench 908 are configured to control the distribution of
under-fill agent 345.
[0108] The panel 900 can be provided wherein the substrate 905
includes the dam 907 on the underside of the substrate 905, wherein
the dam 907 can be an integral part of the substrate 905 or formed
on the substrate 905 at a later time. Similarly, the substrate 905
includes the trench 908 on the underside of the substrate 905. The
dam 907 and the trenches 908 provide a way to control the
distribution of the under-fill agent 345 during manufacturing of
the disclosed double-sided ball grid array packages. For example,
the combination of the dam 907 and the trenches 908 contains the
capillary under-fill material 345 and may prevent it from
contacting or contaminating the solder balls 340. The combination
of the dam 907 and the trenches 908 can provide a repeatable volume
of material to flow under the lower component 335 (e.g., a die),
which reduces the frequency of voiding under the lower component
335. Although the combination of the dam 907 and the trenches 908
is illustrated on a single side of the solder balls 340, it is to
be understood that the dam 907 and/or the trenches 908 can be
configured to surround the solder balls 340.
[0109] The substrate 905 is similar to the substrate 605 and 705
described herein with reference to FIGS. 6A-6D, 7A, and 7B. For
example, the substrate 905 can include surface features 910 that
may provide mechanical support and conductive material 915 to
provide electrical connections between layers and components. The
dam 907 can form continuous elevated structures, a plurality of
disconnected elongated raised features, or a plurality of
outcroppings in the substrate 905. To form the trenches 908, vias
can be formed in the substrate 905, but instead of providing
conductive paths between conductive layers, the vias for the
trenches 908 can provide a void in the substrate structure to
receive under-fill agent during the under-fill processing step. The
trenches 708 can form continuous trench structures, a plurality of
disconnected elongated trenches, or a plurality of voids or holes
in the substrate 705. The trenches 708 can define one or more keep
out areas on the underside of the substrate 705. The combination of
the dam 907 and the trenches 908 can define one or more keep out
areas on the underside of the substrate 905.
[0110] In some embodiments, as described herein with reference to
FIG. 6A, the dam 907 can be formed during an additional solder mask
process during fabrication of the substrate 905. In some
embodiments, the trench 908 can be formed during a solder mask
process during fabrication of the substrate 905. Then, when
assembling the bottom side of the panel 900, the process flow
illustrated in FIGS. 3A-3I can be used. In some embodiments, the
dam 907 can be added to the substrate 905 during fabrication after
the ball and die attach process steps (e.g., as described herein
with reference to FIG. 6B) or the dam 907 can be added to the
substrate 905 during fabrication before the ball and die attach
process steps (e.g., as described herein with reference to FIG.
6C).
[0111] FIG. 9B illustrates the modified process of under-filling in
the presence of the combination of the dam 907 and the trench 908,
compared to the under-filling process illustrated in FIG. 3H. The
combination of the dam 907 and the trench 908 limits the
distribution of the under-fill material 345 to maintain the
under-fill material 345 a targeted or desired distance from the
solder balls 340 while still providing targeted coverage under and
around the lower component 335.
Terminology
[0112] The present disclosure describes various features, no single
one of which is solely responsible for the benefits described
herein. It will be understood that various features described
herein may be combined, modified, or omitted, as would be apparent
to one of ordinary skill. Other combinations and sub-combinations
than those specifically described herein will be apparent to one of
ordinary skill, and are intended to form a part of this disclosure.
Various methods are described herein in connection with various
flowchart steps and/or phases. It will be understood that in many
cases, certain steps and/or phases may be combined together such
that multiple steps and/or phases shown in the flowcharts can be
performed as a single step and/or phase. Also, certain steps and/or
phases can be broken into additional sub-components to be performed
separately. In some instances, the order of the steps and/or phases
can be rearranged and certain steps and/or phases may be omitted
entirely. Also, the methods described herein are to be understood
to be open-ended, such that additional steps and/or phases to those
shown and described herein can also be performed.
[0113] Unless the context clearly requires otherwise, throughout
the description and the claims, the words "comprise," "comprising,"
and the like are to be construed in an inclusive sense, as opposed
to an exclusive or exhaustive sense; that is to say, in the sense
of "including, but not limited to." The word "coupled", as
generally used herein, refers to two or more elements that may be
either directly connected, or connected by way of one or more
intermediate elements. Additionally, the words "herein," "above,"
"below," and words of similar import, when used in this
application, shall refer to this application as a whole and not to
any particular portions of this application. Where the context
permits, words in the above Detailed Description using the singular
or plural number may also include the plural or singular number
respectively. The word "or" in reference to a list of two or more
items, that word covers all of the following interpretations of the
word: any of the items in the list, all of the items in the list,
and any combination of the items in the list. The word "exemplary"
is used exclusively herein to mean "serving as an example,
instance, or illustration." Any implementation described herein as
"exemplary" is not necessarily to be construed as preferred or
advantageous over other implementations.
[0114] The disclosure is not intended to be limited to the
implementations shown herein. Various modifications to the
implementations described in this disclosure may be readily
apparent to those skilled in the art, and the generic principles
defined herein may be applied to other implementations without
departing from the spirit or scope of this disclosure. The
teachings of the invention provided herein can be applied to other
methods and systems, and are not limited to the methods and systems
described above, and elements and acts of the various embodiments
described above can be combined to provide further embodiments.
Accordingly, the novel methods and systems described herein may be
embodied in a variety of other forms; furthermore, various
omissions, substitutions and changes in the form of the methods and
systems described herein may be made without departing from the
spirit of the disclosure. The accompanying claims and their
equivalents are intended to cover such forms or modifications as
would fall within the scope and spirit of the disclosure.
* * * * *