U.S. patent application number 09/384105 was filed with the patent office on 2002-04-25 for surface reformation method of high polymer material.
Invention is credited to IWATA, YASUHIRO, KATAYAMA, KAORU, KAZUI, SHINICHI, SASAKI, HIDEAKI, SHIBUYA, TSUTOMU, SHIRAI, MITUGU.
Application Number | 20020048664 09/384105 |
Document ID | / |
Family ID | 13259877 |
Filed Date | 2002-04-25 |
United States Patent
Application |
20020048664 |
Kind Code |
A1 |
SHIBUYA, TSUTOMU ; et
al. |
April 25, 2002 |
SURFACE REFORMATION METHOD OF HIGH POLYMER MATERIAL
Abstract
There is disclosed a surface reformation method of a high
polymer material such that by irradiating and excimer-laser beam to
only a predetermined area in which electronic parts and the like
are temporarily immobilized by a liquid on a substrate which has a
high polymer layer on the surface, wettability of the liquid for
temporary immobilization only with respect to the predetermined
area is improved. After the electronic parts are temporarily
immobilized on the substrate by using the method, the electronic
parts can be soldered with preferable durability by a fluxess
reflow soldering.
Inventors: |
SHIBUYA, TSUTOMU;
(HADANO-SHI, JP) ; KATAYAMA, KAORU; (HADANO-SHI,
JP) ; SHIRAI, MITUGU; (HADANO-SHI, JP) ;
KAZUI, SHINICHI; (HADANO-SHI, JP) ; SASAKI,
HIDEAKI; (HADANO-SHI, JP) ; IWATA, YASUHIRO;
(HADANO-SHI, JP) |
Correspondence
Address: |
MATTINGLY, STANGER & MALUR, P.C.
1800 DIAGONAL ROAD
SUITE 370
ALEXANDRIA
VA
22314
US
|
Family ID: |
13259877 |
Appl. No.: |
09/384105 |
Filed: |
August 27, 1999 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09384105 |
Aug 27, 1999 |
|
|
|
09028095 |
Feb 23, 1998 |
|
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Current U.S.
Class: |
428/209 ;
174/259; 228/180.21; 228/223; 257/E21.503; 257/E21.511;
428/345 |
Current CPC
Class: |
H05K 2201/10674
20130101; H05K 2201/10734 20130101; H01L 21/6835 20130101; H05K
3/303 20130101; H01L 2924/15787 20130101; Y10T 29/49144 20150115;
H05K 3/305 20130101; H01L 2224/73203 20130101; H05K 3/3436
20130101; Y02P 70/613 20151101; H01L 2924/01005 20130101; H05K 3/22
20130101; H05K 2201/0154 20130101; H01L 2924/01033 20130101; H01L
2924/01004 20130101; H01L 2924/09701 20130101; H01L 2924/014
20130101; H01L 2924/12042 20130101; H01L 2924/14 20130101; H05K
2203/107 20130101; H05K 3/3452 20130101; H01L 2924/01029 20130101;
H01L 2924/01006 20130101; H05K 2203/0783 20130101; H01L 21/563
20130101; H01L 24/81 20130101; H01L 2224/16 20130101; Y10T 428/2809
20150115; Y10T 428/24917 20150115; Y02P 70/50 20151101; H01L
2224/81191 20130101; H01L 2224/81801 20130101; H01L 2924/15787
20130101; H01L 2924/00 20130101; H01L 2924/12042 20130101; H01L
2924/00 20130101 |
Class at
Publication: |
428/209 ;
428/345; 174/259; 228/180.21; 228/223 |
International
Class: |
B32B 003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 23, 1995 |
JP |
7-064496 |
Claims
What is claimed is:
1. A surface reformation method of a high polymer material for
improving wettability of a liquid on the surface of a high polymer
material, wherein light energy is irradiated onto the surface of
the high polymer material in a desired area of which said material
surface is to be reformed.
2. A method according to claim 1, wherein said high polymer
material is polyimide system resin.
3. A method according to claim 2, wherein said polyimide system
resin is polyimide isoindroquinaqolindion or
polymethylmethacrylate.
4. A method according to any one of claims 1, 2, and 3, wherein
said light energy has a wavelength which lies in a range from 100
nm to 600 nm and energy density which exceeds 0.03 J/cm.sup.2 and
is equal to 0.5 J/cm.sup.2 or less.
5. A method according to claim 4, wherein said light energy is an
excimer-laser beam.
6. A method according to claim 4, wherein the energy density of
said light energy is equal to 0.05 J/cm.sup.2 or larger.
7. A method according to claim 4, wherein the energy density of
said light energy is equal to 0.15 J/cm.sup.2 or less.
8. A method according to claim 5, wherein said light energy is
irradiated by irradiating a light energy pulse, of which duration
lies in a range from 20 ns to 100 ns, at least once.
9. A method according to claim 4, wherein a metal pattern for
soldering is provided in said desired area of said high polymer
material.
10. A method according to claim 1, wherein said light energy is
irradiated in either one of the atmosphere, vacuum, and He
assist.
11. A method according to claim 1, wherein said liquid is an
alcohol system liquid or an ester system liquid.
12. A method according to claim 1, wherein said liquid is one
liquid selected from the group consisting of tetraethylene glycol,
pentaethylene glycol, and ethyl salicylate.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a surface reformation
method of a high polymer material and, more particularly, to a
surface reformation method of a high polymer material which is
preferable to be used in order to improve wettability of a liquid
used for temporarily immobilizing electronic parts on an electronic
circuit board of which surface is covered by a high polymer
material layer. The invention also relates to improvement of
wettability of a liquid used for temporary immobilization of
electronic parts when the electronic parts are soldered on an
electronic circuit board according to a fluxless reflow
soldering.
[0002] As a conventional technique regarding a surface reformation
method for wettability improvement of a high polymer material, for
example, methods using an O.sub.2 asher, Ar sputter, or the like
are known. In the methods, a process is performed by setting a
circuit board on which a high polymer material layer to be
processed is coated in a vacuum vessel, and the surface reformation
is executed for the entire surface of the high polymer material on
the substrate.
[0003] According to the conventional technique using, for example,
the O.sub.2 asher or Ar sputtering mentioned above, the surface of
the substrate can be reformed only in an atmosphere of vacuum and
there is a problem such that a large-scaled apparatus including
vacuum equipment, vacuum vessel, and the like is necessary.
According to the conventional technique, since the surface
reformation is executed for the entire surface of the high polymer
material on the substrate, an area which is not necessary to be
processed other than the area on which the electronic parts are
temporarily immobilized on the electronic circuit board or the like
is also reformed. Consequently, the liquid used for the temporary
immobilization of the electronic parts wets the portion which is
unnecessary for the temporary immobilization of the parts, so that
there is a problem such that a large amount of vain liquid is
needed. As mentioned above, when the entire surface of the high
polymer material on the substrate is reformed and the liquid for
temporary immobilization wets even the unnecessary portion, even if
the parts are temporarily immobilized, the parts are moved from
positions of the temporary immobilization at the time of a reflow
soldering, so that the object of the temporary immobilization
cannot not be achieved. Particularly, when the size of the
substrate is equal to 50 mm.times.50 mm or larger, since the liquid
for temporary immobilization tends to gather in the center and the
temporarily immobilized parts easily move, it is not preferable.
Hitherto, a flux for soldering is commonly used in the temporary
immobilization of the parts in the reflow soldering and the parts
are not moved from the positions of the temporary immobilization.
In case of performing the reflow soldering without using the flux,
however, when the liquid for temporary immobilization wets the
unnecessary portion, the object of the temporary immobilization is
not achieved as mentioned above. It is, therefore, conventionally
difficult to solder the electronic parts at predetermined positions
on the electronic circuit board by performing a fluxless reflow
soldering.
SUMMARY OF THE INVENTION
[0004] It is an object of the present invention to provide a
surface reformation method of a high polymer material which solves
the problems of the conventional technique and which can perform a
surface reformation of a substrate in which wettability for a
liquid employed for temporary immobilization is improved with
respect to only an area necessary for temporary immobilization of
electronic parts without needing vacuum equipment, vacuum vessel,
and the like. The surface reformation here denotes the reformation
of the properties of the surface for improving the wettability of
the liquid for temporary immobilization.
[0005] The above-mentioned object of the present invention is
achieved by irradiating only the area to be treated of the surface
(that is, an area to be wetted by the liquid for temporary
immobilization) of high polymer material as a target with light
energy.
[0006] According to the present invention, by applying the light
energy to only the area which needs the surface reformation of the
present high polymer material, the surface of the only portion
which is irradiated with the light energy can be reformed and the
wettability for the liquid can be improved only in the necessary
area. Consequently, the liquid for temporarily immobilizing the
electronic parts and the like can make only the processed area wet,
the processed area can be wetted by the liquid of the minimum
amount, and the electronic parts can be certainly temporarily
immobilized at predetermined positions on the surface of the high
polymer material.
[0007] As a base material of a substrate on which the high polymer
material layer is provided, any substrate used for an integrated
circuit such as, for example, printed board, glass plate, or
ceramic plate can be used.
[0008] A polyimide system resin is used for the high polymer
material layer on which the electronic parts are mounted. As the
polyimide system resin, polyimide isoindroquinazolindion (PIQ;
trade name of Hitachi Chemical Co., Ltd.) and
polymethylmethacrylate (PMMA) can be usually employed. In addition,
OFPR (trade name of Tokyo Ohka Kogyo Co., Ltd.), B20 (trade name of
Hitachi Chemical Co., Ltd.), and the like can be also given.
[0009] A wavelength of the light energy which is thrown onto the
surface of the high polymer material lies in a range from 100 nm to
600 nm. When the wavelength of the irradiation light is too short,
the irradiation light is transmitted to the inside of the high
polymer material. When the wavelength is too long, abrasion of the
high polymer material surface is insufficient. Both of the cases
are not preferable.
[0010] An energy density of the irradiation light is set to larger
than 0.03 J/cm.sup.2 and is equal to 0.5 j/cm.sup.2 or less. When
the energy density is equal to 0.03 J/cm.sup.2 or less, a contact
angle of the liquid for temporary immobilization is equal to 20
degrees or larger, so that the improvement of the wettability is
insufficient. When the energy density exceeds 0.5 J/cm.sup.2, it is
not preferable since a damage caused to the resin layer is too
large to permit when the thickness of the polyimide system resin
layer is equal to 0.5 .mu.m or less.
[0011] As light energy which satisfies the above conditions, an
excimer-laser beam can be used in the present invention.
[0012] Irradiation by the excimer-laser beam is performed by
throwing a pulse of 20 ns to 100 ns (pulse duration is 20 ns to 100
ns) at least once. The pulse duration is set to 20 ns to 100 ns,
because the pulse duration of the excimer-laser beam is equal to
from 20 ns to 100 ns at the present technique level, it is not an
absolute condition. The energy of each pulse of the irradiation
pulse of the light energy exceeds 0.03 J/cm.sup.2 and is equal to
0.5 J/cm.sup.2 or less. At least one pulse of the light irradiation
is necessary. Although the number of pulses can be one or more, the
cost increases when the number is set to an unnecessarily large
number, so that it is usually set to 5 times or less.
[0013] As a liquid for temporary immobilization, for example, an
alcohol system liquid such as tetraethylene glycol or pentaethylene
glycol or an ester system liquid such as ethyl salicylate can be
used.
[0014] A proper amount of the liquid for temporary immobilization
is adhered to a predetermined area by, for example, dropping the
liquid in the predetermined area. An adhesion amount of the liquid
for temporary immobilization is set to an amount sufficient to wet
the predetermined area on the surface of the high polymer material
to temporarily immobilize the electronic parts and ordinarily set
to 4.5 cc to 13.5 cc for an area of 16 mm.times.16 mm (that is,
0.017 cc/mm.sup.2 to 0.053 cc/mm.sup.2).
[0015] According to the method of the present invention, by
temporarily immobilizing the electronic parts on the high polymer
material layer on the substrate, the electronic parts can be easily
soldered at positions where the electronic parts are temporarily
immobilized in a step of the fluxless reflow soldering after
that.
[0016] In order to solder the electronic parts on the substrate, a
metal pattern for the soldering can be provided in at least an area
to be soldered on the substrate. The metal pattern in this case is
constructed by a solderable metal (for example, Cu) and the
thickness can be any thickness as long as it is easy to be
soldered. The soldering can be performed in accordance with, for
example, the micro Ball Grid Array (micro BGA) method or CCB
(Controlled Collapse Bonding) method. A metal layer of a
predetermined shape is provided on the surface of the base material
of the substrate and the high polymer material layer having holes
corresponding to predetermined positions of the metal layer is
coated on the substrate on which the metal layer is provided. On
the other hand, a solder ball is provided for the electronic part
at a position corresponding to the hole section and the solder ball
and the metal layer exposed at the hole section of the high polymer
layer are aligned, thereby temporarily immobilizing the electronic
parts.
[0017] In the method of the present invention using the irradiation
light of the energy density in the above range, the metal pattern
for soldering is not damaged and the surface reformation of the
high polymer material as an insulating material can be
performed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a schematic perspective view for explaining a
surface reformation method of a high polymer material in one
embodiment of the present invention;
[0019] FIG. 2 is a section view showing a construction of a
substrate in one embodiment of the present invention;
[0020] FIG. 3 is a section view showing a state in which electronic
parts are temporarily immobilized on a substrate in one embodiment
of the present invention;
[0021] FIG. 4 is a schematic perspective view showing a state in
which a metal pattern is damaged because of the improper intensity
of an irradiation light;
[0022] FIGS. 5a, 5b, and 5c are perspective views showing
substrates to which light energy is applied so that patterns of
irradiation areas are a square, a circle, a shape obtained by
gathering a plurality of patterns on the substrate
respectively;
[0023] FIG. 6a is an explanatory diagram showing a wet state by a
liquid in one embodiment of the present invention;
[0024] FIG. 6b is an explanatory diagram showing a wet state by a
liquid in the conventional technique;
[0025] FIG. 7a is a schematic perspective view showing a step of
dropping a liquid for temporary immobilization onto a substrate in
order to evaluate the wettability for the liquid used in one
embodiment of the present invention;
[0026] FIG. 7b is a schematic perspective view showing a state in
which the liquid is spread after the step of FIG. 7a;
[0027] FIGS. 7c, 7d, and 7e are schematic perspective views showing
states such that the liquid is further spread after the step of
FIG. 7b and the wet states of the liquid become to be
evaluated;
[0028] FIG. 8a is a schematic section view for explaining a contact
angle for judging the wettability for the liquid in another
embodiment of the present invention; and
[0029] FIG. 8b is a graph showing the relation between the contact
angle of the liquid for temporary immobilization and the energy
density of the irradiation light in the another embodiment of the
present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0030] EMBODIMENT 1
[0031] Embodiment 1 will be described hereinbelow with reference to
the drawings. In the drawings, reference numeral 1 denotes a laser
irradiation area; 2 a substrate; 3 a laser beam; 4 a high polymer
material layer; 5 a base material; 6 an electronic part; 7 a liquid
for temporary immobilization; 8 a metal wiring; 9 an area worked by
an O.sub.2 asher; 10 a pipette; 11 a wetted area; 12 a ball solder;
13 an electrode; 14 a metal pattern; and 15 a hole section.
[0032] In the present embodiment, as shown by a construction
example in FIG. 2, the substrate 2 to be processed in accordance
with the surface reformation method for the high polymer material
is constructed in a manner such that the high polymer material
layer 4 such as PIQ (polyimide isoindroquinazolindion), PMMA
(polymethylmethacrylate), or the like is coated as an insulating
material on the surface of the base material 5 such as ceramic or
the like. On such a substrate 2, metal wiring necessary for forming
an electronic circuit is performed and electronic parts such as LSI
and the like are soldered at predetermined positions. The substrate
2 in the present embodiment has a square shape of 150 mm.times.150
mm and the thickness of 5 mm. As shown in FIG. 3, the high polymer
material layer 4 is formed on the surface of the substrate base
material 5 on which the metal wiring 8 is arranged. There are the
hole sections 15 at predetermined positions of the high polymer
material layer 4. At the positions, the metal wiring 8 is exposed
to form the metal pattern 14 to be soldered.
[0033] The present embodiment intends to improve the wettability of
only necessary portion on the substrate 2 for the liquid 7 for
temporary immobilization in case of temporarily immobilizing the
electronic parts 6 and the like by using the liquid 7 for temporary
immobilization when the electronic parts 6 such as LSI and the like
are soldered.
[0034] As shown in FIG. 1, the surface reformation method of the
high polymer material 4 according to the present embodiment is
executed by applying the light energy by the laser beam 3 to the
laser irradiation area 1 to which the electronic parts 6 are
temporarily immobilized on the substrate 2 which is coated by the
high polymer material layer 4. As a light source of the laser beam
3, an excimer-laser is used. It is particularly preferable that the
wavelength of the laser beam 3 lies within a range from 100 nm to
600 nm and the energy density lies within a range from 0.05
J/cm.sup.2 to 0.5 J/cm.sup.2.
[0035] When an alcohol system solvent such as tetraethylene glycol,
pentaethylene glycol, or the like as a liquid 7 for temporarily
immobilizing the electronic parts is dropped onto the laser
irradiation area 1 on the surface of the substrate 2 to which the
surface reformation has been performed by irradiating the laser
beam 3, the liquid 7 evenly wets in the laser irradiation area 1
and does not wet the unprocessed surface of the substrate 2. The
electronic parts 6 such as LSI and the like can be temporarily
immobilized by the liquid 7 at the predetermined positions on the
substrate 2 to which an embodiment of the present invention has
been performed before soldering as shown in FIG. 3.
[0036] Even in the case where the surface reformation method of the
high polymer material according to the present embodiment is
performed to the surface of the substrate 2 on which the metal
pattern 14 exists for the soldering, the surface of the high
polymer material layer 4 coated on the substrate 2 can be reformed
without damaging the metal wiring 8. When the energy density of the
laser beam 3 is remarkably larger than the values indicated in the
invention, for example, equal to 20 J/cm.sup.2, the metal wiring 8
is damaged as shown in FIG. 4 and it can be broken.
[0037] Further, in the method according to the embodiment of the
present invention, the shape of the laser irradiation area 1 can be
optional in accordance with the sectional shape of the laser beam 3
to be irradiated as shown in FIGS. 5a, 5b and 5c. For example, it
can be a square shown in FIG. 5a, a circle shown in FIG. 5b, and a
shape obtained by gathering a plurality of shapes for reforming a
wide region shown in FIG. 5c. The method according to the present
embodiment is effective in either one of the atmosphere, vacuum, He
assist and can in such circumstance reform the surface of the high
polymer material layer 4. The He assist denotes an atmosphere
during spraying He in order to blow off dusts. By spraying He,
dusts can be blew off further than spraying other gas.
[0038] A state of wettability with respect to the liquid when the
method according to the foregoing embodiment is performed will be
described in comparison with the case of the conventional technique
with reference to FIGS. 6a and 6b.
[0039] As shown in FIG. 6a, the liquid 7 as an alcohol system
solvent in case of performing the method according to the
embodiment wets only a portion of the area 1 which was irradiated
by the laser beam. This is because the portion which is not
subjected to the process according to the present embodiment does
not allow the liquid 7 to wet due to the surface tension even when
the liquid is dropped to the not processed portion or the liquid
tries to invade from the area 1 to which the laser beam has been
thrown.
[0040] On the other hand, in case of the method according to the
conventional technique using the O.sub.2 asher, as shown in FIG.
6b, since the area 9 to be worked by the O.sub.2 asher cannot be
limited to a specific area and the entire surface of the substrate
is processed. The liquid 7 consequently wets the whole surface of
the substrate 2.
[0041] As mentioned above, in the present embodiment in which only
the predetermined area on the substrate 2 is set to the laser beam
irradiation area 1, the liquid 7 for temporary immobilization wets
only the laser beam irradiation area 1 as shown in FIG. 6a. The
electronic parts 6 having the solder ball 12 on the electrode 13 as
shown in FIG. 3 are mounted on the substrate 2 of which only
predetermined area is wet by the liquid 7 for temporary
immobilization and the electronic parts 6 are temporarily
immobilized in a manner such that the solder ball 12 faces the
metal pattern 14 through the hole section 15 of the high polymer
material layer 4. The substrate 2 on which the electronic parts 6
are set as mentioned above is reflow soldered, thereby soldering
the electronic parts to the predetermined positions on the
substrate. The flux is not particularly used. The residual liquid
for temporary immobilization after the completion of the soldering
is evaporated by putting the substrate in the vacuum
atmosphere.
[0042] On the other hand, when the surface of the high polymer
material is not especially processed (when the irradiation of the
light energy, the work by the O.sub.2 asher, sputtering, and the
like are not performed), the surface of the high polymer material
is not wet by the alcohol system solvent, and the electronic parts
cannot be temporarily immobilized, so that the electronic parts
cannot be soldered by the fluxless reflow soldering.
[0043] When the surface of the high polymer material is processed
by the O.sub.2 asher or Ar sputtering as in the conventional
technique, the liquid for temporary immobilization spreads over the
entire surface of the high polymer material and the electronic
parts cannot be soldered to the predetermined positions on the
substrate by the fluxless reflow soldering as mentioned above.
[0044] EMBODIMENT 2
[0045] A method of evaluating the method according to the present
embodiment of the present invention will now be described with
reference to FIGS. 7a to 7e.
[0046] First, the substrate 2 having the square of 150 mm.times.150
mm and thickness of 5 mm is prepared as a sample as shown in FIG.
2, and by the excimer-laser beam having the wavelength of 308 nm,
the energy density of 0.1 J/cm.sup.2, and a time of 30 ns is
irradiated once at the area 1 of the square of 16 mm.times.16 mm.
After that, as shown in FIG. 7a, the liquid 7 of the alcohol system
solvent, that is, tetraethylene glycol or pentaethylene glycol of
about 4.5 cc to 13.5 cc, typically about 9 cc is dropped by using
the pipette 10. The droplet wets the whole surface in a
predetermined area as shown in FIG. 7b. The droplet spread by
wetting is left for 15 minutes. When the liquid 7 remains spread on
the entire surface of the predetermined processed area and is not
leaked out of the processed area as shown in FIG. 7c, it is
evaluated that the surface is sufficiently reformed.
[0047] On the other hand, a case where it is evaluated that the
surface is not sufficiently reformed is shown in FIGS. 7d and 7e.
FIG. 7d shows a state where the liquid 7 wets even out of the
predetermined area 1. FIG. 7e shows a state where an area wetted by
the liquid 7 is reduced and a portion which is not wetted by the
liquid 7 appears on the predetermined area 1. The surface
reformation is insufficient in both of the cases.
[0048] In case of irradiating the surface of the high polymer
material by the light energy under the conditions of the present
invention, a preferred result shown in FIG. 7c can be obtained.
[0049] EMBODIMENT 3
[0050] An experiment result for obtaining the optimum energy
density of the excimer-laser beam according to the present
embodiment will now be described with reference to FIG. 8.
[0051] The surface reformation can be evaluated by measuring the
contact angle .theta. as an angle between the surface of the liquid
7 for temporary immobilization and the surface of the substrate
when the temporary immobilizing liquid is dropped onto the surface
of the substrate 2 as shown in FIG. 8a. When the contact angle
.theta. is equal to 20 degrees or less, it can be usually evaluated
that the surface reformation regarding the wettability is
sufficient. As it is known, the contact angle is measured by
photographing the side and measuring the contact angle in the
photograph. The surface of the substrate 2 is composed of PIQ. The
irradiation condition of the laser beam, kind of the temporary
immobilizing liquid, and dropping condition of the temporary
immobilizing liquid are the same as those in the embodiment 2. The
energy density of the laser beam is changed in a range shown by the
axis of abscissa of FIG. 8b.
[0052] FIG. 8b is the experiment result showing the relation
between the energy density of the excimer-laser beam and the
contact angle .theta. mentioned above.
[0053] As will be clearly understood from FIG. 8b, when the energy
density of the excimer-laser exceeds 0.03 J/cm.sup.2, the contact
angle .theta. becomes 20 degrees or less and the effect of the
invention can be obtained. When the energy density is equal to 0.05
J/cm.sup.2 or larger, the contact angle .theta. is sufficiently
smaller than 20 degrees and it is further preferable. When the
energy density exceeds 0.5 J/cm.sup.2, however, it is not
preferable since the damage caused to the high polymer material
layer becomes large as mentioned above, it is preferable that the
energy density is equal to 0.5 J/cm.sup.2 or less. When the energy
density exceeds 0.15 J/cm.sup.2, there is a tendency such that a
residue after working increases, so that it is further preferable
that the energy density is set to 0.15 J/cm.sup.2 or less.
[0054] In the present invention, the energy density of the
excimer-laser beam is consequently set to larger than 0.03
J/cm.sup.2 and is equal to 0.5 J/cm.sup.2 or less and, preferably,
it is equal to 0.05 J/cm.sup.2 or larger and is equal to 0.15
J/cm.sup.2 or less.
[0055] In the present embodiment, the pulse of the excimer-laser
beam for 30 ns is irradiated only once onto the substrate, thereby
obtaining the data. When the pulse is irradiated three times or
when the irradiation time is set to from 20 ns to 100 ns, it is
confirmed that an almost similar result can be obtained. Further,
when PMMA is used for a high polymer material, a substantially same
result can be also obtained.
[0056] When the laser irradiation condition by which the preferred
result is obtained in the present embodiment is applied to
Embodiment 2, the preferred result can be also obtained.
[0057] According to the surface reformation method of the high
polymer material according to the present invention as mentioned
above, by applying the light energy to only the area which needs
the surface reformation of the high polymer material, the surface
reformation of only the portion to which the light energy is
irradiated can be performed and the wettability of the liquid can
be improved only in the necessary area. Thus, the liquid for
temporarily immobilizing the electronic parts and the like without
needing the vacuum equipment or the like can be wetted only in the
process area and the process area can be wetted with the minimum
amount.
[0058] According to the invention, since the surface reformation of
only the necessary area can be performed, the electronic parts and
the like can be temporarily immobilized on the substrate by using
the minimum amount of the liquid for temporary immobilization.
[0059] When the surface reformation is executed by using the
surface reformation method of the high polymer material of the
present invention, the electronic parts and the like are
temporarily immobilized on the substrate by using the liquid for
temporary immobilization after that and the fluxless reflow
soldering is performed, thereby enabling the soldering of the
electronic parts and the like on the substrate to be executed with
preferable durability.
[0060] In the surface reformation method of the high polymer
material of the invention, even when the metal pattern for
soldering exists in the light energy irradiation area, the metal
pattern is not damaged.
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