U.S. patent application number 13/339981 was filed with the patent office on 2012-07-05 for active resin composition, surface mounting method and printed wiring board.
This patent application is currently assigned to SAN-EI KAGAKU CO., LTD. Invention is credited to Kazuki HANADA, Kazunori KITAMURA, Yasuhiro TAKASE.
Application Number | 20120168219 13/339981 |
Document ID | / |
Family ID | 46379761 |
Filed Date | 2012-07-05 |
United States Patent
Application |
20120168219 |
Kind Code |
A1 |
KITAMURA; Kazunori ; et
al. |
July 5, 2012 |
ACTIVE RESIN COMPOSITION, SURFACE MOUNTING METHOD AND PRINTED
WIRING BOARD
Abstract
A surface mounting method includes applying an active resin
composition to at least part of a surface of a printed wiring
substrate; mounting a surface mount device on the substrate;
performing reflow soldering; applying an under-filling resin into a
space of interest; before and/or after applying the under-filling
resin, performing a vacuum treatment and/or heating at a
temperature lower than the curing reaction-initiating temperature
of any of the applied active resin composition and the
under-filling resin; and subsequently, thermally curing the resin
composition and the under-filling resin. The active resin
composition contains an epoxy resin in an amount of 100 parts by
weight, a blocked carboxylic acid compound in an amount of 1-50
parts by weight and/or a carboxylic acid compound in an amount of
1-10 parts by weight, and a curing agent which can initiate curing
reaction at 150.degree. C. or higher, in an amount of 1-30 parts by
weight.
Inventors: |
KITAMURA; Kazunori;
(Saitama, JP) ; TAKASE; Yasuhiro; (Saitama,
JP) ; HANADA; Kazuki; (Saitama, JP) |
Assignee: |
SAN-EI KAGAKU CO., LTD
Tokyo
JP
|
Family ID: |
46379761 |
Appl. No.: |
13/339981 |
Filed: |
December 29, 2011 |
Current U.S.
Class: |
174/263 ;
228/203; 523/400 |
Current CPC
Class: |
Y02P 70/50 20151101;
H01L 24/83 20130101; H01L 2224/83102 20130101; H01L 21/563
20130101; Y02P 70/613 20151101; H01L 24/13 20130101; H01L
2924/13055 20130101; H05K 2201/10977 20130101; H01L 2224/16238
20130101; H01L 2224/81815 20130101; C08G 59/42 20130101; H01L
2224/2919 20130101; H01L 24/73 20130101; H01L 2224/81191 20130101;
H05K 3/305 20130101; H01L 2924/01029 20130101; B23K 2001/12
20130101; H05K 13/0465 20130101; H01L 2224/83862 20130101; H01L
2224/92125 20130101; H01L 2224/73204 20130101; H01L 2224/83192
20130101; H01L 24/81 20130101; C08L 63/00 20130101; H01L 24/16
20130101; H01L 24/92 20130101; H05K 3/341 20130101; B23K 1/20
20130101; H01L 2224/8191 20130101; B23K 1/0016 20130101; H01L
23/3135 20130101; H01L 24/29 20130101; H01L 24/32 20130101; H01L
2224/131 20130101; H01L 2224/81395 20130101; H01L 2224/32225
20130101; H01L 2924/13055 20130101; H01L 2924/00 20130101; H01L
2224/81815 20130101; H01L 2924/00012 20130101; H01L 2224/2919
20130101; H01L 2924/0665 20130101; H01L 2224/131 20130101; H01L
2924/014 20130101; H01L 2224/83192 20130101; H01L 2224/32225
20130101; H01L 2924/00 20130101; H01L 2224/73204 20130101; H01L
2224/16225 20130101; H01L 2224/32225 20130101; H01L 2924/00
20130101 |
Class at
Publication: |
174/263 ;
523/400; 228/203 |
International
Class: |
H05K 1/11 20060101
H05K001/11; B23K 31/02 20060101 B23K031/02; B23K 1/20 20060101
B23K001/20; C09D 163/04 20060101 C09D163/04; C09D 163/02 20060101
C09D163/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 4, 2011 |
JP |
2011-011378 |
Aug 25, 2011 |
JP |
2011-198839 |
Claims
1. An active resin composition comprising an epoxy resin in an
amount of 100 parts by weight, a blocked carboxylic acid compound
in an amount of 1 to 50 parts by weight and/or a carboxylic acid
compound in an amount of 1 to 10 parts by weight, and a curing
agent which can initiate curing reaction at 150.degree. C. or
higher, in an amount of 1 to 30 parts by weight.
2. A surface mounting method comprising: applying an active resin
composition as recited in claim 1 to at least a part of a surface
of a printed wiring substrate; mounting a surface mount device on
the printed wiring substrate; performing reflow soldering;
performing a vacuum treatment and/or heating at a temperature lower
than the curing reaction-initiating temperature of the applied
active resin composition; and subsequently, thermally curing the
applied resin composition.
3. A surface mounting method comprising: applying an active resin
composition as recited in claim 1 to at least a part of a surface
of a printed wiring substrate; mounting a surface mount device on
the printed wiring substrate; performing reflow soldering; putting
an under-filling resin into a space of interest; before and/or
after putting in the under-filling resin, performing a vacuum
treatment and/or heating at a temperature lower than the curing
reaction-initiating temperature of any of the applied active resin
composition and the under-filling resin; and subsequently,
thermally curing the applied active resin composition and the
under-filling resin.
4. A surface mounting method according to claim 2, wherein the
active resin composition is applied to at least a part of a
metallic surface of the printed wiring substrate.
5. A surface mounting method according to claim 3, wherein the
active resin composition is applied to at least a part of a
metallic surface of the printed wiring substrate.
6. A surface mounting method according to claim 2, wherein, before
mounting the surface mount device on the printed wiring substrate,
there is performed drying the applied resin composition and/or
heating at a temperature which is equal to or higher than the
softening temperature of the applied resin composition and which is
lower than the curing reaction-initiating temperature.
7. A surface mounting method according to claim 3, wherein, before
mounting the surface mount device on the printed wiring substrate,
there is performed drying the applied resin composition and/or
heating at a temperature which is equal to or higher than the
softening temperature of the applied resin composition and which is
lower than the curing reaction-initiating temperature.
8. A surface mounting method according to claim 4, wherein, before
mounting the surface mount device on the printed wiring substrate,
there is performed drying the applied resin composition and/or
heating at a temperature which is equal to or higher than the
softening temperature of the applied resin composition and which is
lower than the curing reaction-initiating temperature.
9. A surface mounting method according to claim 5, wherein, before
mounting the surface mount device on the printed wiring substrate,
there is performed drying the applied resin composition and/or
heating at a temperature which is equal to or higher than the
softening temperature of the applied resin composition and which is
lower than the curing reaction-initiating temperature.
10. A printed wiring board produced through a surface mounting
method as recited in claim 2.
11. A printed wiring board produced through a surface mounting
method as recited in claim 3.
12. A printed wiring board produced through a surface mounting
method as recited in claim 4.
13. A printed wiring board produced through a surface mounting
method as recited in claim 5.
14. A printed wiring board produced through a surface mounting
method as recited in claim 6.
15. A printed wiring board produced through a surface mounting
method as recited in claim 7.
16. A printed wiring board produced through a surface mounting
method as recited in claim 8.
17. A printed wiring board produced through a surface mounting
method as recited in claim 9.
Description
[0001] The entire disclosure of Japanese Patent Applications No.
2011-011378 filed on Jan. 4, 2011 and No. 2011-198839 filed on Aug.
25, 2011 is expressly incorporated by reference herein.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an active resin composition
suitably employed in flip-chip mounting, to a surface mounting
method, and to a printed wiring board produced through the surface
mounting method.
[0004] 2. Background Art
[0005] Conventionally, mounting of surface mount devices such as
BAG parts on the surface of a printed wiring substrate has been
carried out through a procedure including application of a flux
onto the surface; mounting BGA parts on a printed wiring substrate;
reflow soldering; washing off the flux; filling the space between
the printed wiring substrate and the BAG parts with an
under-filling resin; and curing the under-filling resin. As
disclosed in Japanese Patent Application Laid-Open (kokai) No.
2004-152936 (claim 2), a flux known in the art contains, as an
activating agent, a compound having a carboxylic acid group (e.g.,
rosin).
[0006] Meanwhile, a BGA part includes a plurality of mounted chips
for enhancing device performance. Thus, the dimensions of such a
BGA part have gradually over the years.
[0007] When the size of a BGA device increases, washing off the
flux is hindered by the presence of BGA parts, and unremoved flux
(i.e., flux residue) may remain. As a result, an activating agent
contained in the flux residue causes problematic corrosion reaction
during a subsequent step; i.e., a thermal curing of under-filling
resin.
[0008] Meanwhile, as disclosed in Japanese Patent Application
Laid-Open (kokai) No. 2002-237676, another type of the flux is a
wash-less flux, which contains a less-corrosive activating agent
having low activity and which requires no washing step. When such a
wash-less flux is used, the wash-less flux generates decomposition
gas during thermal curing of the under-filling resin, resulting in
destruction of BGA parts, which is also problematic.
[0009] Furthermore, when the size of a BGA part increases,
connection portions between BGA parts impedes filling the space
with under-filling resin. Particularly when the surface of a
printed wiring substrate has dents and protrusions (circuits,
solder resist, etc.), the dents cannot be completely filled with
the under-filling resin, in some cases, providing voids and
unfilled portions. As a result, quality and reliability of products
are considerably impaired. If such voids or the like are not found,
when a subsequent step of thermally curing the under-filling resin
is performed, the products cannot be repaired and must be
discarded, thereby lowering product yield.
SUMMARY OF THE INVENTION
[0010] The present invention provides an active resin composition
and a surface mounting method employing the resin composition,
exhibiting the below-described meritorious effects.
[0011] 1) In the surface mounting method, the step of washing off
the flux can be eliminated, leading to reduced production cost and
enhanced productivity.
[0012] 2) The cured products of applied resin, under-filling resin,
etc. have no defects such as bubbles and voids, leading to
enhancement in device reliability.
[0013] 3) Considerably high thermal stability of the cured product
of applied resin prevents corrosion reaction at high temperature,
and generation of unfavorable decomposition gas.
[0014] More preferably, according to the present invention,
[0015] 4) filling the spaces of interest with under-filling resin
is facilitated. As a result, even when large-scale BGA parts are
mounted, the cured portion of the under-filling resin is free from
bubbles and voids and the resin-unfilled portions are no generated,
whereby reliable bonding (adhesion) can be attained, and device
reliability can be enhanced.
[0016] Also, the present invention provides:
[0017] 5) an active resin composition having high storage
stability.
[0018] The present inventors have carried out extensive studies in
order to attain the aforementioned objects.
[0019] Accordingly, in a first mode of the present invention, there
is provided an active resin composition comprising an epoxy resin
in an amount of 100 parts by weight, a blocked carboxylic acid
compound in an amount of 1 to 50 parts by weight and/or a
carboxylic acid compound in an amount of 1 to 10 parts by weight,
and a curing agent which can initiate curing reaction at
150.degree. C. or higher, in an amount of 1 to 30 parts by
weight.
[0020] In a second mode of the present invention, there is provided
a surface mounting method comprising:
[0021] applying an active resin composition of the first mode to at
least a part of a surface of a printed wiring substrate;
[0022] mounting a surface mount device on the printed wiring
substrate;
[0023] performing reflow soldering;
[0024] performing a vacuum treatment and/or heating at a
temperature lower than the curing reaction-initiating temperature
of the applied active resin composition; and
[0025] subsequently, thermally curing the applied resin
composition.
[0026] In a third mode of the present invention, there is provided
a surface mounting method comprising:
[0027] applying an active resin composition of the first mode to at
least a part of a surface of a printed wiring substrate;
[0028] mounting a surface mount device on the printed wiring
substrate;
[0029] performing reflow soldering;
[0030] putting an under-filling resin into a space of interest;
[0031] before and/or after putting in the under-filling resin,
performing a vacuum treatment and/or heating at a temperature lower
than the curing reaction-initiating temperature of any of the
applied active resin composition and the under-filling resin;
and
[0032] subsequently, thermally curing the applied active resin
composition and the under-filling resin.
[0033] In the second and third modes of the invention, the active
resin composition may be applied to at least a part of a metallic
surface of the printed wiring substrate.
[0034] In the second and third modes of the invention, before
mounting the surface mount device on the printed wiring substrate,
there may be performed drying the applied resin composition and/or
heating at a temperature which is equal to or higher than softening
temperature of the applied resin composition and which is lower
than the curing reaction-initiating temperature.
[0035] In a fourth mode of the present invention, there is provided
a printed wiring board produced through any of the aforementioned
surface mounting methods.
[0036] By use of the active resin composition of the present
invention, the following meritorious effects can be attained.
[0037] The present invention provides an active resin composition
and a surface mounting method employing the resin composition,
exhibiting the below-described effects.
[0038] 1) In the surface mounting method, the step of washing off
the flux can be eliminated, leading to reduced production cost and
enhanced productivity.
[0039] 2) The cured products of applied resin, under-filling resin,
etc. have no defects such as bubbles and voids, leading to
enhancement in device reliability.
[0040] 3) Considerably high thermal stability of the cured product
of applied resin prevents corrosion reaction at high temperature,
and generation of unfavorable decomposition gas.
[0041] 4) Filling the spaces of interest with under-filling resin
is facilitated. As a result, even when large-scale BGA parts are
mounted, the cured portion of the under-filling resin is free from
bubbles and voids and the resin-unfilled portions are no generated,
whereby reliable bonding (adhesion) can be attained, and device
reliability can be enhanced.
[0042] In a preferred embodiment of the active resin composition of
the present invention,
[0043] 5) the storage stability of the active resin composition can
be enhanced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0044] Various other objects, features, and many of the attendant
advantages of the present invention will be readily appreciated as
the same becomes better understood with reference to the following
detailed description of the preferred embodiments when considered
in connection with the accompanying drawings, in which:
[0045] FIG. 1 is a sketch with cross-sections showing an embodiment
of the mounting method of the present invention;
[0046] FIG. 2 is a sketch with cross-sections showing another
embodiment of the mounting method of the present invention;
[0047] FIG. 3A is a plan view of a printed wiring substrate
employed in Examples 1 to 5;
[0048] FIG. 3B is a cross-section of the printed wiring substrate
shown in FIG. 3A, cut along a-a';
[0049] FIG. 4 is a sketch with cross-sections showing an embodiment
of the mounting method employed in the Examples;
[0050] FIG. 5A is a bottom plan view of a semiconductor chip
employed in Examples 1 to 5;
[0051] FIG. 5B is a cross-section of the semiconductor chip shown
in FIG. 5A, cut along a-a';
[0052] FIG. 6A is a plan view of another printed wiring substrate
employed in Examples 1 to 5;
[0053] FIG. 6B is a cross-section of the printed wiring substrate
shown in FIG. 6A, cut along a-a';
[0054] FIG. 7A is a bottom plan view of a BGA part employed in
Examples 1 to 5; and
[0055] FIG. 7B is a cross-section of the BGA part shown in FIG. 7A,
cut along a-a'.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0056] Best modes of the present invention will next be described
with reference to the drawings.
[0057] The active resin composition employed in the surface
mounting method of the present invention contains an epoxy resin,
which also serves a matrix resin. The epoxy resin reacts with the
below-described activating agent during the curing reaction, to
thereby deactivate the activating agent. By virtue of the epoxy
resin, the cured active resin composition has very high thermal
stability, and therefore, corrosion and generation of decomposition
gas during heating (e.g., thermal curing of the under-filling
resin) are prevented.
[0058] Examples of the epoxy resin include epoxy resins which
assume solid at room temperature. The epoxy resin preferably has a
softening temperature of, for example, 70 to 150.degree. C.,
particularly preferably 80 to 100.degree. C. Specific examples of
the solid epoxy resin include cresol-novolak epoxy resin,
dicyclopentadienyl-type epoxy resin, biphenyl-type epoxy resin,
bisphenol A-type solid epoxy resin, and solid alicyclic epoxy
resin.
[0059] Alternatively, the epoxy resin may be an epoxy resin which
assumes liquid at room temperature. The liquid epoxy resin is an
epoxy resin which is liquid or semi-solid at ambient temperature,
for example, an epoxy resin having fluidity at ambient temperature.
Such liquid epoxy resin preferably has a viscosity (room
temperature) of, for example, 20,000 mPas or lower, particularly
preferably 1,000 to 10,000 mPas.
[0060] Specific examples of the liquid epoxy resin include liquid
bisphenol A-type epoxy resins represented by the following
formula:
##STR00001##
(wherein n is 0 or 1, and G represents glycidyl group). These epoxy
resins may be used singly or in combination. Specific examples
further include liquid bisphenol F-type epoxy resins represented by
the following formula:
##STR00002##
(wherein n is 0 or 1, and G represents glycidyl group). These epoxy
resins may be used singly or in combination.
[0061] Specific examples of the liquid epoxy resin further include
naphthalene-type epoxy resin, diphenyl thioether (sulfide)-type
epoxy resin, trityl-type epoxy resin, alicyclic epoxy resin,
alcohol-derived epoxy resin, diallyl bis-A-type epoxy resin,
methylresorcinol-type epoxy resin, bisphenol AD-type epoxy resin,
and N,N,O-tris(glycidyl)-p-aminophenol. These epoxy resins may be
used singly or in combination.
[0062] Examples of preferred liquid epoxy resins include bisphenol
A-type epoxy resin, bisphenol F-type epoxy resin,
N,N,O-tris(glycidyl)-p-aminophenol, and bisphenol AD-type epoxy
resin. These epoxy resins may be used singly or in combination.
[0063] The active resin composition of the invention contains a
blocked carboxylic acid compound and/or a carboxylic acid compound.
The carboxylic acid species serves as an activating agent.
[0064] The blocked carboxylic acid compound is synthesized through
reaction between a carboxylic acid compound with a blocking agent.
When the blocked carboxylic acid compound is used, side reaction at
low temperature can be inhibited, to thereby enhance storage
stability of the active resin composition.
[0065] The carboxylic acid compound, serving as a starting material
for synthesizing the blocked carboxylic acid compound, may be a
monocarboxylic acid compound. Specific examples of the starting
carboxylic acid compound include aromatic monocarboxylic acids
(e.g., (hydroxy)benzoic acid, dihydroxybenzoic acid, phenylacetic
acid, benzoic acid, toluic acid, and naphthoic acid); saturated
monocarboxylic acids (e.g., acetic acid, propionic acid, butyric
acid, 2-methylpropanoic acid (isobutyric acid), 2-ethylhexanoic
acid, lauric acid, and cyclohexanecarboxylic acid); unsaturated
monocarboxylic acids (e.g., acrylic acid, methacrylic acid,
crotonic acid, and oleic acid); and abietic acid.
[0066] Specific examples of the starting carboxylic acid compound
further include polycarboxylic acid compounds. More specific
examples include aliphatic polyvalent carboxylic acids (e.g.,
oxalic acid, malonic acid, succinic acid, glutaric acid, adipic
acid, azelaic acid, sebacic acid, decamethylenedicarboxylic acid,
butanetetracarboxylic acid, and 1,2,3,4-butanetetracarboxylic
acid); aromatic polyvalent carboxylic acids (e.g., phthalic acid,
isophthalic acid, terephthalic acid, trimellitic acid, pyromellitic
acid, naphthalenedicarboxylic acid, and benzenecarboxylic acid (in
particular, having 3 to 4 carboxylic groups)); alicyclic polyvalent
carboxylic acids (e.g., tetrahydrocarboxylic acid,
hexahydrocarboxylic acid, tetrahydrophthalic acid, and
hexahydrophthalic acid); unsaturated aliphatic polyvalent
carboxylic acids (e.g., maleic acid, fumaric acid, and itaconic
acid); polyvalent carboxylic acids produced through
half-esterification between polyol having two or more (preferably 2
to 50) hydroxyl groups and acid anhydride; polyvalent carboxylic
acids produced through addition reaction between polyisocyanate
having two or more (preferably 2 to 50) isocyanato groups and
hydroxycarboxylic acid or amino acid; polyvalent carboxylic acids
produced through homo- or co-polymerization of unsaturated
carboxylic acid(s); polyester-type polyvalent carboxylic acids
produced through reaction between polyol and polyvalent carboxylic
acid; and carboxylic acid polymers (e.g., styrene-maleic acid
copolymer and acrylic acid copolymer).
[0067] The blocking agent, serving as the other starting material
for synthesizing the blocked carboxylic acid compound, is
preferably a compound whose carboxyl-blocking (protecting) group is
removed at the curing reaction-initiating temperature of the active
resin composition. Specific examples of the starting blocking agent
include compounds having one vinyl ether moiety in the molecules
thereof, more specifically, aliphatic vinyl ethers (e.g., methyl
vinyl ether, ethyl vinyl ether, isopropyl vinyl ether, n-propyl
vinyl ether, isobutyl vinyl ether, n-butyl vinyl ether, cyclohexyl
vinyl ether, propyl vinyl ether, butyl vinyl ether,
2-ethylcyclohexyl vinyl ether, t-butyl vinyl ether, and
2-ethylhexyl vinyl ether); cyclic vinyl ethers (e.g.,
2,3-dihydrofuran, 2,3-dihydro-2H-pyran, 3,4-dihydro-2H-pyran,
3,4-dihydro-2-methoxy-2H-pyran,
3,4-dihydro-4,4-dimethyl-2H-pyran-2-one,
3,4-dihydro-2-ethoxy-2H-pyran, sodium
3,4-dihydro-2H-pyran-2-carboxylate, and 3,4-dihydrofuran);
aliphatic vinyl thioether compounds (e.g., dihydrofuran); cyclic
vinyl ether compounds (e.g., dihydro-2H-pyran); and cyclic vinyl
thioether compounds.
[0068] Specific examples of the starting blocking agent further
include compounds having two or more vinyl ether moieties in the
molecules thereof, more specifically, divinyl ether compounds
(e.g., ethylene glycol divinyl ether, 1,2-propylene glycol divinyl
ether, 1,3-propylene glycol divinyl ether, 1,3-butanediol divinyl
ether, 1,4-butanediol divinyl ether, 2,3-butanediol divinyl ether,
1,6-hexanediol divinyl ether, diethylene glycol divinyl ether,
triethylene glycol divinyl ether, pentanediol divinyl ether,
dimethylbutanediol divinyl ether, 3-methyl-1,5-pentanediol divinyl
ether, hydrogenated bisphenol A divinyl ether, neopentyl glycol
divinyl ether, 1,8-octanediol divinyl ether,
1,4-cyclohexanedimethanol divinyl ether, 2-methyl-1,3-propanediol
divinyl ether, 1,4-cyclohexanediol divinyl ether, 1,9-nonanediol
divinyl ether, triethylene glycol divinyl ether, tetraethylene
glycol divinyl ether, bisphenol A divinyl ether, and hydrogenated
bisphenol A divinyl ether), and divinyl thioether compounds.
[0069] Specific examples of the blocked carboxylic acid compound
include bisalkyl esters of cyclohexanedicarboxylic acid,
1-isopropoxyethyl (meth)acrylate, 1-ethoxyethyl (meth)acrylate,
1-t-butoxyethyl (meth)acrylate, 1-(1-methylhexyloxy)ethyl
(meth)acrylate, 1-(1,1-dimethylpropoxy)ethyl (meth)acrylate,
1-isopropoxyethyl(meth)acrylamide, 1-ethoxyethyl(meth)acrylamide,
1-t-butoxyethyl(meth)acrylamide,
1-(1-methylhexyloxy)ethyl(meth)acrylamide,
1-(1,1-dimethylpropoxy)ethyl(meth)acrylamide,
1,2,4-benzenetricarboxylic acid
2,4-bis(propoxyethyl)-1-((meth)acryloxyethyl)ester, and
(co)polymers thereof. These compounds may be used singly or in
combination.
[0070] Specific examples of commercial products of the blocked
carboxylic acid compound include Santacid G, Santacid FK-03,
Santacid FK-05, Santacid FK-16, Santacid KM-01, Nofcure-TN-2,
Nofcure-OP, and Nofcure-TY501 (products of NOF Corporation). These
compounds may be used singly or in combination.
[0071] Instead of or in addition to the blocked carboxylic acid
compound, the carboxylic acid compound itself may be used. The
carboxylic acid compound may be the same as those exemplified as
the aforementioned starting material for synthesizing the blocked
carboxylic acid compound. These compounds may be used singly or in
combination.
[0072] The active resin composition of the invention contains a
curing agent. The curing agent can initiate curing reaction at
150.degree. C. or higher (preferably 160 to 200.degree. C.) Through
employment of the curing agent that acts at high temperature, no
curing reaction occurs by heating for a short period of time. Thus,
curing of the active resin composition during reflow soldering can
be prevented. Specific examples of the curing agent include
dicyandiamide.
[0073] The active resin composition may further contain a solvent.
Particularly when the composition contains a solid material (solid
epoxy resin or the like), incorporation of a solvent is preferred.
The solvent preferably has a boiling point lower than the curing
reaction-initiating temperature, particularly preferably 150 to
200.degree. C. Specific examples of the solvent include glycol
ethers, ethylene glycol ether esters, propylene glycol ether
esters, and N-methylpyrrolidone.
[0074] The active resin composition may contain other additives
such as a defoaming agent (e.g., polydimethylsiloxane), a silane
coupling agent, and Aerosil.
[0075] The active resin composition contains an epoxy resin in an
amount of 100 parts by weight, a blocked carboxylic acid compound
in an amount of 1 to 50 (preferably 10 to 40) parts by weight
and/or a carboxylic acid compound in an amount of 1 to 10
(preferably 2 to 5) parts by weight, and a curing agent in an
amount of 1 to 30 (preferably 2 to 7) parts by weight. The amount
of solvent is preferably 10 to 300 (preferably 30 to 100) parts by
weight.
[0076] The active resin composition may or may not contain a
solvent and may assume solid or liquid form. However, in a
preferred embodiment, the active resin composition assumes in the
form of a solid having a softening temperature of 50 to 150
(particularly 80 to 120).degree. C., after removal of solvent (or
drying of resin). In the case where the softening temperature is
excessively low, the composition exhibits a tacky property even at
room temperature, possibly resulting in deposition of dust (i.e.,
migration of foreign matter into the device), whereas when the
softening temperature is excessively high, defoaming during the
vacuum treatment performed after reflow-mounting may be
insufficient. In addition, the active resin composition is
preferably re-softened by heating after solidification by
cooling.
[0077] In one embodiment of the surface mounting method of the
present invention, an active resin composition 3 (FIG. 1) (See step
B) falling within the scope of the invention is applied to at least
a part of the surface (or the entire surface) of a printed wiring
substrate 1 (FIG. 1) (See step A). Hereinafter, the thus-applied
active resin composition may be referred to as "applied resin." The
active resin composition may be applied to at least a part of a
metallic surface of the printed wiring substrate. The metallic
surface may be formed of, for example, at least one species
selected from among pure metals (e.g., copper) and alloys (e.g.,
solder). More specifically, the resin composition may be applied
onto at least a part of a circuit and/or at least a part of a pad 2
(FIG. 1) (See step A). Furthermore, the resin composition may be
applied to at least a solder portion of a surface mount device 4
(FIG. 1) (See step C) serving as a member to be bonded. More
specifically, the resin composition may be applied to the entire
bottom surface of the surface mount device or to a bump 9 (FIG. 1)
(See step C) of the surface mount device. The applied resin
generally has a thickness of 10 to 50 .mu.m.
[0078] Thereafter, if needed (for example, in the case where a
solid epoxy resin and a solvent is used), the applied resin may be
dried for removal of the solvent. Through drying, the applied resin
generally assumes the form of a tack-free coating film. The drying
conditions may be 80 to 120.degree. C. for 10 to 30 minutes.
[0079] Alternatively, if needed (for example, in the case where the
dried applied resin assumes solid), the applied resin may be heated
at a temperature which is equal to or higher than the softening
temperature of the applied resin and which is lower than the curing
reaction-initiating temperature (hereinafter this heating process
may be referred to as "heating A"). Through heating A, the applied
resin generally exhibits tacky property, whereby mounting of a
surface mount device is facilitated. The heating conditions may be
80 to 180.degree. C. for 10 seconds to 10 minutes.
[0080] Drying and heating A of the applied resin may be performed
singly or in combination, and sequentially in any order or
simultaneously.
[0081] Subsequently, the surface mount device 4 (FIG. 1) (See step
C) is mounted on the printed wiring substrate 1 (FIG. 1) (See step
C). In the present invention, there may be large-scale surface
mount devices; for example, those of 50 mm.times.50 mm squares or
more. Specifically, the surface mount device may be a package
device or a semiconductor chip. Examples of the package device
include BGA parts, CSP parts, MCM parts, IPM parts, and IGBT
parts.
[0082] Next, reflow soldering is performed (FIG. 1) (See step D).
The reflow conditions may be 240 to 300.degree. C. for 10 seconds
to 10 minutes. When the reflow heating time is excessively long,
the applied resin may undergo curing reaction, which is not
preferred.
[0083] Subsequently, there is performed a vacuum treatment and/or
heating of the applied resin at a temperature lower than the curing
reaction-initiating temperature (hereinafter this heating process
may be referred to as "heating B").
[0084] The vacuum treatment is performed for the following reasons.
Specifically, during reflow soldering, oxides or the like present
on the surface of molten solder undergo chemical reaction
(including reduction) by the applied resin (active resin
composition), to thereby possibly form water or other substances.
In the case where the formed water or other substances remain in
the applied resin, they are evaporated with volume expansion during
thermal curing of the resin, whereby the cured applied resin may
have bubbles, voids, etc. Therefore, the vacuum treatment is
performed for the purpose of removing water or the like in advance.
In addition, through the vacuum treatment, defoaming of the applied
resin or the like is completed. Preferred vacuum treatment
conditions include a vacuum degree of 10 to 80,000 (particularly
100 to 50,000) Pa for 1 to 60 (particularly 5 to 30) minutes.
[0085] Heating B is performed at a temperature lower than the
curing reaction-initiating temperature of the applied resin. In the
case where the applied resin is solid, heating B is preferably
performed at a temperature equal to or higher than the softening
temperature of the applied resin. Through heating B, dehydration
and defoaming of the resin or the like is completed. In the above
case, the applied resin is softened through heating B, and the
thus-softened applied resin buries the irregularities of the
surface of the printed wiring substrate (i.e., planarization). As a
result, when a space of interest is filled with the under-filling
resin, resin filling is facilitated, whereby the cured
under-filling resin includes no bubbles, voids, or resin-unfilled
cavities. Preferred specific heating conditions include 60 to 150
(particularly 80 to 120).degree. C. for 0.1 to 60 (particularly 1
to 10) minutes.
[0086] The vacuum treatment and heating B may be performed singly
or in combination, and sequentially in any order or simultaneously.
Preferably, at least the vacuum treatment is performed.
[0087] Subsequently, the applied resin 10 is thermally cured (FIG.
1) (See step E). The thermal curing temperature is equal to or
higher than the curing reaction-initiating temperature provided by
the curing agent. Specific thermal curing conditions include 150 to
200.degree. C. for 1 to 4 hours. In this case, the blocked
carboxylic acid compound and/or carboxylic acid compound react(s)
with the epoxy resin, thereby losing the activity as the activating
agent. Thus, impairment of reliability, which would otherwise be
caused by corrosion or the like, can be prevented.
[0088] As described above, the printed wiring board of the present
invention is produced.
[0089] In another embodiment of the surface mounting method of the
present invention, similar to the first embodiment, the
above-described steps; from application of active resin to reflow
soldering, are performed. Specifically, the aforementioned active
resin composition 3 (FIG. 2) (See step B) is applied to at least a
part of the surface of a printed wiring substrate 1 (FIG. 2) (See
step A). A surface mount device 4 (FIG. 2) (See step C) is mounted
on the printed wiring substrate 1 (FIG. 2) (See step C). Then,
reflow soldering is performed (FIG. 2) (See step D).
[0090] For the purpose of packaging and other reasons, a space of
interest is filled with an under-filling resin 11 (FIG. 2) (See
step E). Specifically, the space between the printed wiring
substrate and the surface mount device is filled with the
under-filling resin. The under-filling resin preferably has a
curing reaction-initiating temperature of 100 to 250 (particular
150 to 200).degree. C. Specific examples of the under-filling resin
include epoxy resin, silicone resin, polyimide resin, polyolefin
resin, cyanate ester resin, phenolic resin, and naphthalene resin.
At least one of these resins may be employed.
[0091] Before and/or after putting in the under-filling resin,
there is performed the vacuum treatment and/or heating at a
temperature lower than the curing reaction-initiating temperature
of any of the applied resin and the under-filling resin
(hereinafter this heating process may be referred to as "heating
C"). In one embodiment, reflow soldering, and sequentially any one
of i)-iii) as follows are performed, and then thermally curing of
the resins (applied resin and under-filling resin) is
performed:
i) the vacuum treatment and/or heating C, and putting in the
under-filling resin, ii) the vacuum treatment and/or heating C, and
putting in the under-filling resin, and the vacuum treatment and/or
heating C, iii) putting in the under-filling resin, and the vacuum
treatment and/or heating C.
[0092] The vacuum treatment and heating C may be performed singly
or in combination, and sequentially in any order or simultaneously.
Preferably, at least the vacuum treatment is preformed, and heating
C is performed before putting in the under-filling resin.
[0093] The vacuum treatment may be performed through the same
procedure as described above. Through the vacuum treatment,
dehydration and defoaming of the resins (e.g., applied resin and
filled resin) may be completed.
[0094] Heating C may be performed through the same procedure as
that of heating B. Through heating C, dehydration/defoaming and
putting in the under-filling resin are facilitated. However, in the
case where heating C is performed after putting in the
under-filling resin, the heating temperature is adjusted to be
lower than the curing reaction-initiating temperature of any of the
applied resin and the under-filling resin so as not to cause curing
reaction of the applied resin and the under-filling resin.
[0095] Subsequently, the applied resin 10 and the under-filling
resin 6 are thermally cured (FIG. 2) (See step F). The thermal
curing temperature is equal to or higher than the curing
reaction-initiating temperature provided by the curing agent and
equal to or higher than the curing temperature of the under-filling
resin. Specific thermal curing conditions include 150 to
200.degree. C. for 1 to 12 hours.
[0096] As described above, the printed wiring board of the present
invention including the under-filling resin is produced.
EXAMPLES
[0097] The present invention will next be described in detail by
way of examples.
<Preparation of Active Resin Composition>
Preparation Examples 1 to 5
[0098] Ingredients (compositions shown in Table 1) were uniformly
mixed together, to thereby prepare active resin compositions
(Preparation Examples 1 to 5).
<Production of Printed Wiring Board>
Examples 1 to 5
[0099] Each of the above-prepared active resin compositions
(Preparation Examples 1 to 5) 3 (FIG. 4) (See step B) was applied,
through screen printing, to the entire surface of a printed wiring
substrate 1 (FIG. 3A, 3B, FIG. 4 (See step A)) (10 mm.times.10 mm)
having pads 2 (FIG. 4) (See step A) (pitch: 0.6 mm, pad diameter:
0.3 mm, number of pads: 25) (FIG. 4) (See step B).
[0100] Thereafter, the printed wiring substrate was heated at
100.degree. C. for 20 minutes, to thereby dry the applied resin.
After cooling to room temperature, the applied resin coated on the
printed wiring substrate assumed the form of non-tacky solid and
was found to have a pencil hardness of HB.
[0101] When the printed wiring substrate was heated to 120.degree.
C., the applied resin was softened and exhibited tacky
property.
[0102] While the applied resin remained soft, a semiconductor chip
4 (4 mm.times.4 mm) (FIG. 5A, 5B, FIG. 4 (See step C)) having bumps
9 (FIG. 4) (See step C) (pitch: 0.6 mm, bump diameter: 0.3 mm,
number of bumps: 25) was mounted by means of a mounter onto the
printed wiring substrate (FIG. 4) (See step C).
[0103] The printed wiring substrate 1 (FIG. 4) (See step C) on
which the semiconductor chip 4 (FIG. 4) (See step C) was mounted
was reflow-soldered by means of a reflow apparatus (preliminary
heating: 150 to 180.degree. C. for 60 seconds, reflow heating: 220
to 260.degree. C. for 30 seconds) (FIG. 4) (See step D).
[0104] When the printed wiring substrate to which the semiconductor
chip was bonded via soldering was cooled, the applied resin surface
assumed the form of solid having a pencil hardness of HB.
[0105] Thereafter, when the printed wiring substrate was heated
again to 120.degree. C., the applied resin was softened again and
exhibited tacky property. While the temperature was maintained at
120.degree. C., the printed wiring substrate was subjected to
vacuum treatment (vacuum degree: 100 Pa, 2 minutes).
[0106] The printed wiring substrate was heated (190.degree. C. for
2 hours), to thereby cure the active resin composition, to thereby
produce each of the printed wiring boards (Examples 1 to 5). After
curing, the applied resin surface exhibited a pencil hardness of
8H, indicating that the resin was completely cured (FIG. 4) (See
Step E).
[0107] The semiconductor chip was physically peeled from each of
the printed wiring boards (Examples 1 to 5). When the active resin
composition was observed under a magnifying glass (.times.20), no
forms or voids were observed.
Comparative Example 1
[0108] The procedure of Example 1 (production of a printed wiring
board) was repeated, except that no heating at 120.degree. C. or
vacuum treatment was performed before thermal curing of the active
resin composition, to thereby produce a printed wiring board
(Comparative Example 1).
[0109] The semiconductor chip was physically peeled from the
printed wiring board (Comparative Example 1). When the cured active
resin composition was observed under a magnifying glass
(.times.20), 17 bubbles and voids were observed. The sizes of the
bubbles and voids were found to be 0.5 to 2 mm.
Example 6
[0110] Firstly, a uniform paste-like active resin composition
having the following compositional proportions was prepared
(Preparation Example 6).
[0111] Composition: cresol novolak-type epoxy resin (softening
temperature: 94.degree. C.) (100 parts by weight), p-hydroxybenzoic
acid (4 parts by weight), dicyan diamide (5 parts by weight), and
propylene glycol methyl ether acetate (50 parts by weight).
[0112] The above paste-like active resin composition (Preparation
Example 6) was applied, through screen printing, to the entire
surface of a printed wiring substrate 1 (FIG. 6) (100 mm.times.100
mm) having pads (pad pitch: 0.6 mm, pad diameter: 0.3 mm, number of
pads: 1,010).
[0113] Thereafter, the printed wiring substrate was heated at
100.degree. C. for 20 minutes, to thereby dry the applied resin.
After cooling to room temperature, the applied resin coated on the
printed wiring substrate assumed non-tacky solid and was found to
have a pencil hardness of HB.
[0114] When the printed wiring substrate was heated to 120.degree.
C., the applied resin was softened and exhibited tacky
property.
[0115] While the applied resin remained soft, a BGA part 4 (70
mm.times.70 mm) (FIG. 7) (bump pitch: 0.6 mm, bump diameter: 0.3
mm, number of bumps: 1,010) were mounted by means of a mounter onto
the printed wiring substrate.
[0116] The printed wiring substrate on which the BGA part was
mounted was reflow-soldered by means of a reflow apparatus (peak
temperature: 260.degree. C.)
[0117] When the printed wiring substrate to which the BGA part was
bonded via soldering was cooled, the applied resin surface assumed
the form of solid having a pencil hardness of HB.
[0118] Thereafter, when the printed wiring substrate was heated
again to 120.degree. C., the applied resin was softened again and
exhibited tacky property. While the temperature was maintained at
120.degree. C., the printed wiring substrate was subjected to
vacuum treatment (vacuum degree: 150 Pa, 60 minutes).
[0119] The printed wiring substrate was heated (190.degree. C. for
2 hours), to thereby cure the active resin composition, to thereby
produce a printed wiring boards (Example 6). After curing, the
applied resin surface exhibited a pencil hardness of 8H, indicating
that the resin was completely cured.
[0120] The BGA part was physically peeled from the printed wiring
board (Example 6). When the cured active resin composition was
observed under a magnifying glass (.times.20), no bubbles or voids
were observed.
Example 7
[0121] Firstly, similar to the method of producing the printed
wiring board (Example 6), the steps to the reflow soldering were
performed.
[0122] When the printed wiring substrate to which the BGA part was
bonded via soldering was cooled, the applied resin surface assumed
the form of solid having a pencil hardness of HB.
[0123] Thereafter, when the printed wiring substrate was heated
again to 120.degree. C., the applied resin was softened again and
exhibited tacky property.
[0124] While the temperature was maintained, an under-filling resin
(CEL-C-3720, product of Hitachi Chemical Co., Ltd.) was
charged.
[0125] Thereafter, the printed wiring substrate was subjected to
vacuum treatment (vacuum degree: 150 Pa, 30 minutes).
[0126] The printed wiring substrate was heated (190.degree. C. for
2 hours), to thereby cure the active resin composition and
under-filling resin, to thereby produce a printed wiring boards
(Example 7).
[0127] The thus-produced printed wiring board (Example 7) was
subjected to X-ray observation. Either the cured active resin
composition or the cured under-filling resin was found to contain
no bubbles or voids. The cavities unfilled with the cured
under-filling resin were no found.
Examples 8 to 12
[0128] The procedure of Example 7 (production of a printed wiring
board) was repeated, except that an active resin composition of any
of Preparation Examples 1 to 5 was used instead of the active resin
composition of Preparation Example 6, to thereby produce each of
the printed wiring boards (Examples 8 to 12).
[0129] The thus-produced printed wiring boards (Examples 8 to 12)
were subjected to X-ray observation. In each case, either the cured
active resin composition or the cured under-filling resin was found
to contain no bubbles or voids. The cavities unfilled with the
cured under-filling resin were no found.
Comparative Example 2
[0130] The procedure of Example 8 (production of a printed wiring
board) was repeated, except that no heating at 120.degree. C. or
vacuum treatment was performed before thermal curing of the active
resin composition and the under-filling resin, to thereby produce a
printed wiring board (Comparative Example 2).
[0131] The thus-produced printed wiring board (Comparative Example
2) was subjected to X-ray observation. In the cured active resin
composition and under-filling resin, 22 bubbles and voids were
observed. The sizes of the bubbles and voids were found to be 0.5
to 2 mm. Two cavities unfilled with the cured under-filling resin
were observed, and the sizes of the cavities were 4 mm and 7 mm,
respectively.
<Active Resin Composition Performance Test>
Solder Bonding Test
[0132] Each active resin composition (storage period: 0 day) was
used, and the steps from application of active resin to reflow
soldering were performed in a manner similar to that employed in
the method of producing the printed wiring board (any of Examples 1
to 5). Thereafter, the printed wiring substrate was cooled, and a
BGA part was forcedly peeled from the printed wiring board. Among
25 solder bumps, the number of bumps bonded to the land of the
printed wiring substrate was counted. Table 1 shows the ratio of
bonded solder bump (percent solder bonding).
Storage Stability (25.degree. C.)
[0133] The solder bonding test was repeated, except that an active
resin composition of a different storage period was used instead of
the active resin composition (storage period: 0 day). There was
determined the period of time when the percent solder bonding
attained by the composition (storage period: 0 day) was maintained.
Table 1 shows the data (storage limit).
TABLE-US-00001 TABLE 1 Ingredients Preparation Examples (parts by
wt.) 1 2 3 4 5 Cresol novolak epoxy resin.sup.1) 100 -- 100 -- 100
Bisphenol A type liq. epoxy resin.sup.2) -- 100 -- 100 -- Santacid
G 10 35 10 20 -- Nofcure TN-2 10 -- 5 -- -- Hydroxybenzoic acid --
-- -- -- 4 Dicyan diamide 4 4 4 4 1 Diethylene glycol monoethyl
ether 30 -- 30 -- 30 acetate Solder bonding 100% 100% 100% 100% 80%
Storage stability .gtoreq.60 .gtoreq.60 .gtoreq.60 .gtoreq.60 2
days (25.degree. C.) days days days days .sup.1)Nippon Kayaku Co.,
Ltd. "EOCN-103" .sup.2)Nippon Kayaku Co., Ltd. "RE-310S"
* * * * *