U.S. patent application number 12/344023 was filed with the patent office on 2009-08-06 for semiconductor package and method of attaching semiconductor dies to substrates.
This patent application is currently assigned to UTAC - United Test and Assembly Test Center, Ltd.. Invention is credited to Florian Ammer, Denver Paul C. Castillo, Soo Pin Chow, Kian Teng Eng, Wolfgang Johannes Hetzel, Rodel Manalac, Pang Hup Ong, Werner Josef Reiss, Soon Hua Bryan Tan.
Application Number | 20090194871 12/344023 |
Document ID | / |
Family ID | 40786063 |
Filed Date | 2009-08-06 |
United States Patent
Application |
20090194871 |
Kind Code |
A1 |
Castillo; Denver Paul C. ;
et al. |
August 6, 2009 |
SEMICONDUCTOR PACKAGE AND METHOD OF ATTACHING SEMICONDUCTOR DIES TO
SUBSTRATES
Abstract
A method of mounting a semiconductor die on a substrate with a
solder mask on a first surface includes placing a die on the solder
mask, and mounting the die to the substrate by applying pressure
and heat. The applied pressure ranges from a bond force of
approximately 5 to 10 Kg, the heat has a temperature range from
approximately 150 to 200.degree. C. and the pressure is applied for
a range of approximately 1 to 10 seconds.
Inventors: |
Castillo; Denver Paul C.;
(Singapore, SG) ; Tan; Soon Hua Bryan; (Singapore,
SG) ; Manalac; Rodel; (Singapore, SG) ; Eng;
Kian Teng; (Singapore, SG) ; Ong; Pang Hup;
(Singapore, SG) ; Chow; Soo Pin; (Singapore,
SG) ; Hetzel; Wolfgang Johannes; (Nattheim, DE)
; Reiss; Werner Josef; (Bad Feilnbach, DE) ;
Ammer; Florian; (Ergoldsbach, DE) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W., SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
UTAC - United Test and Assembly
Test Center, Ltd.
Singapore
SG
|
Family ID: |
40786063 |
Appl. No.: |
12/344023 |
Filed: |
December 24, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61016863 |
Dec 27, 2007 |
|
|
|
Current U.S.
Class: |
257/734 ;
257/E21.509; 257/E23.026; 438/118 |
Current CPC
Class: |
H01L 2224/83192
20130101; H01L 2924/01006 20130101; H01L 24/83 20130101; H01L
2924/0665 20130101; H01L 2224/29101 20130101; H01L 2924/014
20130101; H01L 24/29 20130101; H01L 2924/01005 20130101; H01L
2924/01033 20130101; H01L 2224/8385 20130101; H01L 2924/01082
20130101; H01L 2224/2919 20130101; H01L 2924/07802 20130101; H01L
2224/2919 20130101; H01L 2924/0665 20130101; H01L 2224/2919
20130101; H01L 2924/0635 20130101; H01L 2924/0665 20130101; H01L
2924/00 20130101; H01L 2224/2919 20130101; H01L 2924/0665 20130101;
H01L 2924/00 20130101; H01L 2224/29101 20130101; H01L 2924/014
20130101; H01L 2924/00 20130101; H01L 2924/3512 20130101; H01L
2924/00 20130101 |
Class at
Publication: |
257/734 ;
438/118; 257/E21.509; 257/E23.026 |
International
Class: |
H01L 23/492 20060101
H01L023/492; H01L 21/60 20060101 H01L021/60 |
Claims
1. A method of mounting a semiconductor die on a substrate with a
solder mask on a first surface comprising: placing a die on said
solder mask; mounting said die to said substrate by applying
pressure and heat.
2. The method of claim 1 wherein said applied pressure ranges from
a bond force of approximately 5 to 10 Kg.
3. The method of any one of claims 1 and 2 wherein said heat has a
temperature range from approximately 150 to 200.degree. C.
4. The method of any one of claims 1 and 2 wherein said pressure is
applied for a range of approximately 1 to 10 seconds.
5. The method of claim 1 wherein said heat causes said solder mask
to adhere said die to said substrate.
6. The method of claim 1 wherein said applied pressure is a bond
force of approximately 5 Kg.
7. The method of any one of claims 1 and 6 wherein said heat has a
temperature of approximately 175.degree. C.
8. The method of any one of claims 1 and 6 wherein said pressure is
applied for approximately 5 seconds.
9. The method of claim 1 wherein said solder mask is not pre-baked
before said die is attached.
10. A semiconductor package comprising: a semiconductor die; a
substrate; and a solder mask; wherein said solder mask adheres said
die to said substrate.
11. The semiconductor package of claim 10, wherein said substrate
further comprises a core and a metal layer wherein said metal layer
is between said core and said solder mask.
12. The semiconductor package of claim 10, wherein said solder mask
comprises acrylic epoxy.
13. The semiconductor package of claim 10, wherein said solder mask
has a thickness of approximately at least 30 .mu.m.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority from U.S. Provisional
Application No. 61/016,863 filed on Dec. 27, 2007, the disclosure
of which is incorporated herein by reference.
BACKGROUND OF INVENTION
[0002] 1. Field of Invention
[0003] Apparatuses consistent with the present invention relate to
semiconductor packages and methods for manufacturing semiconductor
packages. More particularly, the present invention relates to a
semiconductor package wherein a solder mask adheres a semiconductor
die to the substrate through the application of heat and
pressure.
[0004] 2. Description of the Related Art
[0005] Current methods for manufacturing semiconductor packages,
such as lead-on-chip (LOC) devices, include applying a printable
paste, epoxy or tape onto a substrate and then pressing the
semiconductor die onto the paste. Next, curing is performed (not if
tape is used), which securely bonds the die to the substrate. The
curing step can take up to three hours.
[0006] However, because the manufacture of semiconductor packages
is a high volume process, designers are always looking for ways to
reduce cost and manufacturing time. One cost savings approach that
was investigated was to reduce the volume of paste used in the
current process, such as a known as 4-dot printing design whereby
four "dots" of adhesive are provided on the substrate for die
attachment. However, this approach was unsuccessful because
delamination of the die from the substrate occurred.
[0007] Therefore, an objective of the present invention is to
develop a method of adhering a die to a substrate without the use
of paste or adhesive tape. By eliminating the printable paste
process, material and manpower savings can be obtained and
manufacturing time can be shortened through the elimination of the
LOC cure.
SUMMARY OF THE INVENTION
[0008] Exemplary embodiments of the present invention overcome the
above disadvantages and other disadvantages not described above.
Also, the present invention is not required to overcome the
disadvantages described above, and an exemplary embodiment of the
present invention may not overcome any of the problems described
above.
[0009] An embodiment of the inventive method of mounting a
semiconductor die on a substrate with a solder mask on a first
surface includes placing a die on the solder mask, and mounting the
die to the substrate by applying pressure and heat.
[0010] In another embodiment of the inventive method, the applied
pressure ranges from a bond force of approximately 5 to 10 Kg.
[0011] In another embodiment of the inventive method, the heat has
a temperature range from approximately 150 to 200.degree. C.
[0012] In another embodiment of the inventive method, the pressure
is applied for a range of approximately 1 to 10 seconds.
[0013] In another embodiment of the inventive method, the heat
causes the solder mask to adhere said die to the substrate.
[0014] In another embodiment of the inventive method, the applied
pressure is a bond force of approximately 5 Kg.
[0015] In another embodiment of the inventive method, the heat has
a temperature of approximately 175.degree. C.
[0016] In another embodiment of the inventive method, the pressure
is applied for approximately 5 seconds.
[0017] In another embodiment of the inventive method, the solder
mask is not pre-baked before the die is attached.
[0018] An embodiment of the inventive semiconductor package
includes a semiconductor die, a substrate, and a solder mask,
wherein the solder mask adheres the die to the substrate.
[0019] In another embodiment of the inventive package, the
substrate also includes a core and a metal layer wherein the metal
layer is between the core and the solder mask.
[0020] In another embodiment of the inventive package, the solder
mask is made of acrylic epoxy.
[0021] In another embodiment of the inventive package, the solder
mask has a thickness of approximately at least 30 .mu.m.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The above and/or other aspects of the present invention will
become apparent and more readily appreciated from the following
description of the exemplary embodiments, taken in conjunction with
the accompanying drawings, in which:
[0023] FIG. 1 is a cross-sectional view of an embodiment of the
inventive substrate with solder masks.
[0024] FIG. 2 is a table of technical specifications of an
exemplary substrate.
[0025] FIG. 3 is a cross-sectional view of an exemplary mounting
device.
[0026] FIGS. 4A, 4B, 5, 6 and 7 are tables showing results of
different studies related to the inventive method.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION
[0027] Hereinafter, exemplary embodiments of the present invention
will be described with reference to the accompanying drawings.
[0028] Prior to arriving at the present invention, a baseline study
was performed to aid in the determination of the optimum parameters
and methods. The study involved attempting to mount a plurality of
dies to a bare substrate. After the dies were placed on the
substrate, various pressures in the form of bonding forces (1 kg to
10 kg) and heat were applied. The temperatures ranged from
100.degree. C. to 475.degree. C. After application of the various
pressures and heat, none of the dies adhered to the substrate. In
addition, the substrate began showing signs of burning at
temperatures above 300.degree. C. Burning was very apparent at
temperatures at and above of 350.degree. C. Also, the passivation
coating of the die surface was damaged during the process.
[0029] Next, studies were performed to see if a solder mask could
be used to adhere the die to the substrate. The studies used a
two-metal layer substrate composition supplied by Kinsus that had a
solder mask applied over the bare metal layers. The invention is
not limited to substrates supplied by Kinsus. In this particular
embodiment, the solder mask was made from acrylic epoxy. FIG. 1
shows a substrate with top and bottom solder masks applied on the
metal layers M1 and M_Base. The metal layers cover a substrate
core. Technical specifications of an exemplary substrate are shown
in FIG. 2. The solder mask may be applied to the metal layers by
well-known printing methods. In addition, the solder mask is formed
at least on areas between the die and the substrate.
[0030] In the particular embodiment shown in FIG. 1, the core is
approximately 200 .mu.m thick, the metal layers are approximately
8-16 .mu.m thick, and the solder masks are approximately 30 .mu.m
thick. The total substrate thickness, with the solder masks is
approximately 285.+-.50 .mu.m. Solder masks that are greater than
30 .mu.m thick will also be acceptable for this invention.
[0031] FIG. 3 is a representation of a mounting device that can
used to mount the die to the substrate, with the solder masks
already applied. In the study, a Renesas CM 700 series lead-on-chip
mounter was used along with diamond coated 8.0.times.8.0 mm mount
and stage tools. The invention is not limited to mounting machines
supplied by Renesas. The die is positioned next to the
corresponding substrate by the stage tool. After the stage tool and
mount tool are heated, the mount tool presses the die and substrate
together. The heat causes the material state of the solder mask to
change, which causes the die to adhere to the substrate.
[0032] During the study, several combinations of temperature (e.g.,
150, 175 and 200.degree. C.), bond force (e.g., 1, 2, 5 and 10 kg)
and bond time (e.g., 1, 5 and 10 sec.) were used.
[0033] FIGS. 4A and 4B shows some of the different combinations and
results. In the first six legs in FIG. 4A, none of the dies adhered
to the substrate. Likewise, in the first leg in FIG. 4B, the die
did not adhere.
[0034] In legs 7A and 7B in FIG. 4A, some dies adhered, however,
approximately one-third of the dies did not adhere.
[0035] In legs 8A and 8B in FIG. 4A, all dies adhered
satisfactorily. The parameters that were used in stages 8A and 8B
were a temperature of 200.degree. C., pressure of 10 kg and a bond
time of 10 seconds.
[0036] In legs 2 through 9 in FIG. 4B, the dies adhered
satisfactorily, despite issues with low die shear, high bond forces
and high temperatures. The optimal combination of parameters
occurred in leg 5. In that leg, the temperature was 175.degree. C.,
bond force was 5 kg and bond time of 5 seconds.
[0037] Next, studies were performed to see if oven baking impacted
the process. Studies were carried out using substrates with solder
masks that were not pre-baked, and substrates with solder masks
that were pre-baked. As shown in FIG. 5, when the substrates that
were not oven baked before die attachment, all of the samples had
acceptable results. However, when the substrates were oven baked
before die attachment, many of the samples failed. Hence, the
studies show that it is desirable to use substrates with solder
masks that are not pre-baked before assembly.
[0038] FIG. 6 is a summary of studies that were performed with
different conditions on the mounting device. As mentioned above,
the mounting device used in these series of studies is Renesas CM
700 series lead-on-chip mounter together with diamond coated
8.0.times.8.0 mm mount and stage tools. The mounting device has
"pre-heat", "pre-bake" or "laminate" functions typically designed
for die attachment to substrates using adhesive paste or tape. For
example, the "pre-heat" function heats up the adhesive before die
attachment, the "pre-bake" function bakes the adhesive to remove
moisture before die attachment and the "laminator" function
laminates the adhesive (in the form of tape) onto the substrate
before die attachment. As the present invention does not utilize
any form of adhesive between the die and substrate, the inventors
have experimented with these functions for die attachment to the
solder mask layer of the substrate. The mounting device was
configured as follows--Legs A & B with pre-heat, pre-bake and
laminator functions OFF, Legs C & D with pre-heat and pre-bake
functions ON and laminator function OFF, and Legs E & F with
pre-heat, pre-bake and laminator functions ON. It was found that
die adhesion is most satisfactory in Legs A & B when the
pre-bake, pre-heat and laminator functions are OFF. Die adhesion
was also observed for Legs C & D but with lower die shear
values. Some of the dies did not adhere in Legs E & F thereby
showing that conditions of pre-heat, pre-bake and laminator
functions in togetherness are not desirable.
[0039] FIG. 7 shows additional test results.
[0040] In summary, the studies showed that good die to substrate
adhesion is possible when using the following parameter settings:
Bond Force of 5-10 kg; Bond Time of 1-10 seconds; Bond Temperature
of 150-200.degree. C. Optimal parameter settings would be Bond
Force of 5 kg; Bond Time of 5 seconds; Bond Temperature of
175.degree. C. The studies also show that substrates with solder
mask which are not pre-baked are desirable in this invention.
[0041] These parameter settings have been shown to provide good die
to substrate adhesion even after MSL 3 testing. In addition, no die
cracks were observed during the mounting process. Advantageously,
the present invention provided means of attaching a die to a
substrate without using an adhesive paste or tape thereby resulting
in process time, material and manpower savings
[0042] While the present invention has been particularly shown and
described with reference to exemplary embodiments thereof, it will
be understood by those of ordinary skill in the art that various
changes in form and details may be made therein without departing
from the spirit and scope of the present invention as defined by
the following claims.
* * * * *