U.S. patent application number 12/715777 was filed with the patent office on 2010-09-09 for heat exchanger.
This patent application is currently assigned to HITACHI CABLE, LTD.. Invention is credited to Muneo Kodaira, Takaaki SASAOKA.
Application Number | 20100224351 12/715777 |
Document ID | / |
Family ID | 42677196 |
Filed Date | 2010-09-09 |
United States Patent
Application |
20100224351 |
Kind Code |
A1 |
SASAOKA; Takaaki ; et
al. |
September 9, 2010 |
HEAT EXCHANGER
Abstract
A heat exchanger is provide, in which a fin member and a tube
member are joined each other, wherein the fin member includes a
solder wetting film layer containing copper, in at least a part of
a surface of a fin substrate made of aluminum or an alloy mainly
composed of aluminum, where the fin member and the tube member are
joined each other, and the tube member includes a solder film layer
made of solder containing tin, in at least a part of a surface of a
tube substrate made of copper or an alloy mainly composed of
copper, where the tube member and the fin member are joined each
other, wherein the fin member and the tube member are joined each
other, through a diffusion bonding of a copper component of the
solder wetting film layer and a tin component of the solder film
layer.
Inventors: |
SASAOKA; Takaaki;
(Tsuchiura-shi, JP) ; Kodaira; Muneo;
(Tsuchiura-shi, JP) |
Correspondence
Address: |
Fleit Gibbons Gutman Bongini & Bianco PL
21355 EAST DIXIE HIGHWAY, SUITE 115
MIAMI
FL
33180
US
|
Assignee: |
HITACHI CABLE, LTD.
Tokyo
JP
|
Family ID: |
42677196 |
Appl. No.: |
12/715777 |
Filed: |
March 2, 2010 |
Current U.S.
Class: |
165/180 ;
165/181 |
Current CPC
Class: |
B23K 2103/18 20180801;
B23K 2103/10 20180801; B23K 1/203 20130101; B23K 2101/14 20180801;
F28D 1/05366 20130101; F28F 1/126 20130101; B23K 2101/34 20180801;
F28F 21/084 20130101; B23K 2103/12 20180801; B23K 1/19 20130101;
F28F 21/085 20130101; B23K 1/0012 20130101; F28F 2275/04
20130101 |
Class at
Publication: |
165/180 ;
165/181 |
International
Class: |
F28F 21/00 20060101
F28F021/00; F28F 1/10 20060101 F28F001/10 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 5, 2009 |
JP |
2009-051974 |
Claims
1. A heat exchanger having a structure in which a fin member and a
tube member are joined each other, wherein the fin member includes
a solder wetting film layer containing copper, in at least a part
of a surface of a fin substrate made of aluminum or an alloy mainly
composed of aluminum where the fin member and the tube member are
joined each other, and the tube member includes a solder film layer
made of solder containing tin, in at least a part of a surface of a
tube substrate made of copper or an alloy mainly composed of copper
where the tube member and the fin member are joined each other,
wherein the fin member and the tube member are joined each other,
through a diffusion bonding of a copper component of the solder
wetting film layer and a tin component of the solder film
layer.
2. A heat exchanger having a structure in which a fin member and a
tube member are joined each other, wherein the fin member includes
a solder wetting film layer containing copper in at least a part of
a surface of a fin substrate made of aluminum or an alloy mainly
composed of aluminum where the fin member and the tube member are
joined each other, and includes a solder film layer made of solder
containing tin on the surface of the solder wetting film layer, and
the tube member is made of copper or an alloy mainly composed of
copper, wherein the fin member and the tube member are joined each
other, through a diffusion bonding of a copper component of the
tube member and a tin component of the solder film layer.
3. The heat exchanger according to claim 1, wherein the solder
wetting film layer is formed as a two-layer lamination structure of
a underlayer made of niobium or chromium, and a surface layer made
of an alloy mainly composed of copper and added with at least one
kind of metal of nickel and zinc.
4. The heat exchanger according to claim 2, wherein the solder
wetting film layer is formed as a two-layer lamination structure of
a underlayer made of niobium or chromium, and a surface layer made
of an alloy mainly composed of copper and added with at least one
kind of metal of nickel and zinc.
5. The heat exchanger according to claim 1, wherein a thickness of
the solder wetting film layer is 5 nm or more and 400 nm or less,
and a thickness of the solder film layer is 3 .mu.m or more and 100
.mu.m or less.
6. The heat exchanger according to claim 2, wherein a thickness of
the solder wetting layer is 5 nm or more and 400 nm or less, and a
thickness of the solder film layer is 3 .mu.m or more and 100 .mu.m
or less.
7. The heat exchanger according to claim 3, wherein a thickness of
the solder wetting film layer is 5 nm or more and 400 nm or less,
and a thickness of the solder film layer is 3 .mu.m or more and 100
.mu.m or less.
8. The heat exchanger according to claim 4, wherein a thickness of
the solder wetting film layer is 5 nm or more and 400 nm or less,
and a thickness of the solder film layer is 3 .mu.m or more and 100
.mu.m or less.
9. The heat exchanger according to claim 1, wherein the solder film
layer is made of pure tin.
10. The heat exchanger according to claim 2, wherein the solder
film layer is made of pure tin.
11. The heat exchanger according to claim 3, wherein the solder
film layer is made of pure tin.
12. The heat exchanger according to claim 4, wherein the solder
film layer is made of pure tin.
13. The heat exchanger according to claim 3, wherein the solder
film layer is made of pure tin, having a thickness of 3 .mu.m or
more and 30 .mu.m or less.
14. The heat exchanger according to claim 4, wherein the solder
film layer is made of pure tin, having a thickness of 3 .mu.m or
more and 30 .mu.m or less.
15. The heat exchanger according to claim 3, wherein the underlayer
of the solder wetting film layer is made of niobium, and the solder
film layer is formed on the surface of the solder wetting film
layer not subjected to cathodic degrease, by electroplating.
16. The heat exchanger according to claim 4, wherein the underlayer
of the solder wetting film layer is made of niobium, and the solder
film layer is formed on the surface of the solder wetting film
layer not subjected to cathodic degrease, by electroplating.
17. The heat exchanger according to claim 3, wherein the underlayer
of the solder wetting film layer is a sputter film made of niobium
or chromium, with the underlayer having an internal residual stress
of a compression stress or a zero stress, and the surface layer of
the solder wetting film layer is the sputter film.
18. The heat exchanger according to claim 4, wherein the underlayer
of the solder wetting film layer is a sputter film made of niobium
or chromium, with the underlayer having an internal residual stress
of a compression stress or a zero stress, and the surface layer of
the solder wetting film layer is a sputter film.
Description
TECHNICAL FIELD
[0001] The present invention relates to a heat exchanger having a
structure in which a fin member and a tube member are joined each
other.
DESCRIPTION OF RELATED ART
[0002] A heat exchanger includes a structure in which a fin member
and a tube member are joined each other. For example, in a case of
the heat exchanger used as a radiator for cooling an engine of an
automobile, the fin member, the tube member, and a tank member are
combined, with essential parts of them joined each other. As a main
joint part, there are a part between the tank member and the tube
member, and a part between the fin member and the tube member, and
generally such members are joined each other by soldering and
brazing (patent document 1)
[0003] If the heat exchanger is classified, with the joint between
the fin member and the tube member focused on, there are mainly two
kinds such as the heat exchanger made of brass wherein the fin
member and the tube member molded by using a plate material of
brass (or a copper (Cu)-based alloy similar to brass) as a metal
material, are joined each other by soldering of in-furnace heating
at 300.degree. C. or less, and the heat exchanger made of aluminum
wherein the fin member and the tube member, molded by using a plate
material of aluminum (Al: including not only pure Al but also an Al
alloy, etc.), are joined each other by aluminum brazing of
in-furnace heating at about 600.degree. C.
[0004] The heat exchanger made of brass was used in most of the
heat exchangers for automobiles before 1990. However, owing to a
progress of the aluminum brazing technique and due to a problem of
lead (Pb) involved in solder, the latter heat exchanger made of
aluminum is used in most cases in recent years. However, when
aluminum can not be used due to inconveniences such as corrosion in
the tube member, the former heat exchanger made of brass is used
even now. However, in a case of the heat exchanger made of brass,
there is an unavoidable defect such as a heavy weight, compared
with the latter heat exchanger made of aluminum.
[0005] Further, the heat exchanger made of all aluminum, using a
solder joining technique is also proposed (patent document 2). As a
main essential part of the all aluminum-made heat exchanger, the
fin member and the tube member are made of aluminum by applying
nickel (Ni) plating all over the surface of them, and after they
are temporarily assembled, each part where the fin member and the
tube member are brought into contact with each other is joined by
soldering.
(Patent document 1)
Japanese Patent Laid Open Publication No. 2007-136490
[0006] (Patent document 2)
Japanese Patent Laid Open Publication No. 1985-102270
[0007] Generally, the aluminum brazing is apt to be more
complicated in its process, thus incurring higher cost than
soldering. Therefore, even in a case of the heat exchanger made of
all aluminum, the soldering is preferably used for its joint.
[0008] However, a conventional technique involves a problem that it
is extremely difficult to surely join the fin member and the tube
member made of aluminum by soldering.
[0009] Further, in order to overcome both of a susceptibility to a
corrosion, which is a defect when the heat exchanger is made of all
aluminum, and a defect that total weight is increased, which is a
defect when the heat exchanger is made of all brass, it is
effective to use a method of making a the tube member using a
copper-based material such as brass, and also making the fin member
using aluminum. We study on this method, but in this case, there is
a problem that it is extremely difficult to surely join a member
made of aluminum and a member made of copper-based metal such as
brass by plating according to the conventional technique.
[0010] Further, in order to realize excellent soldering to the
member made of aluminum as described above, it can be considered to
use a technique of using a flux having an activity strong enough to
melt an oxide film (passivation film) on the surface of aluminum of
this member. However, actually, there is a high possibility that a
part near the joint part is remarkably damaged and deteriorated
after soldering by use of such an extremely strong flux as
described above, which is an undesirable defect from a viewpoint of
durability and reliability of the joint part.
SUMMARY OF THE INVENTION
[0011] An object of the present invention is to provide a heat
exchanger having a structure in which a fin member made of aluminum
or an alloy mainly composed of aluminum, and a tube member made of
copper or an alloy mainly composed of copper, are joined each other
satisfactorily, through a diffusion bonding of copper and tin.
[0012] According to an aspect of the present invention, a heat
exchanger is provided, having a structure in which a fin member and
a tube member are joined each other, wherein the fin member
includes a solder wetting film layer containing copper, in at least
a part of a surface of a fin substrate made of aluminum or an alloy
mainly composed of aluminum where the fin member and the tube
member are joined each other, and
[0013] the tube member includes a solder film layer made of solder
containing tin, in at least a part of a surface of a tube substrate
made of copper or an alloy mainly composed of copper where the tube
member and the fin member are joined each other,
[0014] wherein the fin member and the tube member are joined each
other, through a diffusion bonding of a copper component of the
solder wetting film layer and a tin component of the solder film
layer.
[0015] Further, according to other aspect of the present invention,
a heat exchanger is provided, having a structure in which a fin
member and a tube member are joined each other,
[0016] wherein the fin member includes a solder wetting film layer
containing copper, in at least a part of a surface of a fin
substrate made of aluminum or an alloy mainly composed of aluminum
where the fin member and the tube member are joined each other,
and
[0017] the tube member includes a solder film layer made of solder
containing tin, in at least a part of a surface of a tube substrate
made of copper or an alloy mainly composed of copper where the tube
member and the fin member are joined each other,
[0018] wherein the fin member and the tube member are joined each
other, through a diffusion bonding of a copper component of the
solder wetting film layer and a tin component of the solder film
layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a view showing a main essential part of an overall
structure of a heat exchanger according to an embodiment of the
present invention.
[0020] FIG. 2 is a view showing a fin substrate used in the heat
exchanger according to a first embodiment of the present
invention.
[0021] FIG. 3 is a view showing a tube substrate used in the heat
exchanger according to the first embodiment of the present
invention.
[0022] FIG. 4 is a view showing a tank substrate used in the heat
exchanger according to the first embodiment of the present
invention.
[0023] FIG. 5 is a front view showing a sample having a structure
of the heat exchanger formed by joining the fin member and the tube
member, and the tank member in the heat exchanger according to the
first embodiment of the present invention.
[0024] FIG. 6 is a side view of a sample of joining the fin member,
the tube member, and the tank member shown in FIG. 5.
[0025] FIG. 7 is a view showing a fin substrate used in the heat
exchanger according to a second embodiment of the present
invention.
[0026] FIG. 8 is a front view showing a sample of the structure of
the heat exchanger wherein the fin member and the tube member are
joined each other.
[0027] FIG. 9 is a view showing the structure of the fin member and
the tube member, a heating temperature during joining, and a joint
state indicated by a table form, according to an example 1 and a
comparative example 1 of the present invention.
[0028] FIG. 10 is a view showing the structure of the fin member
and the tube member, the heating temperature during joining, and
the joint state indicated by a table form, according to the example
1 and the comparative example 1.
[0029] FIG. 11 is a view showing the structure of the fin member
and the tube member, the heating temperature during joining, and
the joint state indicated by a table form, according to an example
2 and a comparative example 2.
[0030] FIG. 12 is a view showing the structure of the fin member
and the tube member, the heating temperature during joining, and
the joint state indicated by a table form, according to an example
2 and a comparative example 2.
DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
[0031] A heat exchanger according to preferred embodiments of the
present invention will be described hereinafter, with reference to
the drawings.
[0032] As an overall structure common in heat exchangers according
to the first and second embodiments of the present invention, as
shown in FIG. 1, a fin member 1, a tube member 2, and a tank member
3 are provided, as essential parts thereof.
[0033] In the heat exchanger having this structure, the fin member
1 is formed in a wave shape. Such a wave shape contributes to
increasing a substantial surface area of the fin member 1, and also
contributes to performing efficient heat exchange with outer air in
a space 15 formed between the tube member and the fin member 1.
Accordingly, when a refrigerant (high-temperature refrigerant) such
as cooling water 4 is passed through the tube member 2, heat held
by the cooling water 4 is transmitted to the tube member 2, then
passed out, and further transmitted to the fin member 1 brought
into contact with the tube member 2. Then, the heat transmitted to
the tube member 2 and the fin member 1 is discharged into the outer
air (low-temperature refrigerant) flowing through the space 15.
Thus, the efficient heat exchange is performed in this heat
exchanger.
[0034] Further, in this heat exchanger, the fin member 1 and the
tube member 2 are surely joined each other by a solder joining
technique according to an embodiment of the present invention.
[0035] Note that the fin member may be joined not to an outer face
of the tube member but to an inner face of the tube member.
Further, a direction of joining the fin member to the tube member
may be a peripheral direction or an axial direction of the tube
member. Further, the fin member may be continuously joined to the
tube member or may be joined thereto discontinuously.
The Heat Exchanger According to a First Embodiment
[0036] In the heat exchanger according to the first embodiment, the
fin member 1 is formed by folding and bending a fin plate material
9, an example of which is shown in FIG. 2, into a wave shape, and
is disposed in a state of being interposed between adjacent two
tube members 2, 2, and each part of the fin member 1 brought into
contact with the tube member 2 is surely joined to the tube member
2. Further, the fin member 1 is disposed in a state of being
interposed between right and left tank members 3. The fin member 1
and the tank member 3 may be joined each other or may be simply set
in contact with each other mechanically.
[0037] The fin plate material 9 has a solder wetting film layer 5
containing copper (Cu), on approximately the whole surface or at
least in a part of the fin substrate 6 made of aluminum (Al) or an
alloy mainly composed of aluminum (Al) where the fin member 1 and
the tube member 2 are joined each other.
[0038] According to a preferable numerical aspect, a thickness of
the solder wetting film layer 5 is set to 5 nm or more and 400 nm
or less, and further preferably set to 10 nm or more and 400 nm or
less.
[0039] This is because if the thickness is less than 10 nm, it is
highly possibly difficult to obtain solder wettability for
obtaining a satisfactory joint (if the thickness is less than 5 nm,
it is further remarkably difficult to obtain solder wettability),
and also this is because if the thickness is beyond 400 nm, a
manufacturing cost is highly possibly increased, due to a technical
factor such that a time and a material are required for forming
such a thick layer.
[0040] Here, as schematically shown in FIG. 2, it is a preferable
aspect that the solder wetting film layer 5 has a two-layer
lamination structure of a underlayer 7 made of niobium (Nb) and
chromium (Cr), and a surface layer 8 made of an alloy mainly
composed of copper (Cu) and added with at least one kind of metal
of nickel (Ni) and zinc (Zn), provided on the surface of the
underlayer 7.
[0041] With such a two-layer lamination structure, separation
between the solder in a heated and melted state, and aluminum (Al)
can be prevented.
[0042] In the solder wetting film layer 5 having the two-layer
lamination structure, it is preferable that the underlayer
(adhesive layer) 7 made of niobium or chromium is a sputter film
made of niobium or chromium, with an internal residual stress of
this sputter film set as a compressive stress or zero stress, and
the surface layer (bonding layer) 8 mainly composed of copper and
added with at least one kind of metal of nickel and zinc is the
sputter film. Further, it is preferable to set an oxygen amount
contained in the underlayer (adhesive layer) 7 and the surface
layer (bonding layer) 8 to be extremely small, and when the
underlayer (adhesive layer) 7 and the surface layer (bonding layer)
8 are formed by sputtering, film formation is performed in a film
forming atmosphere in which oxygen is removed as much as possible.
Further, the thickness of the underlayer (adhesive layer) 7 is set
to 10 nm or more and the thickness of the surface layer (bonding
layer) 8 is set to 15 nm or more.
[0043] Aluminum or an aluminum-based alloy has an oxide film
(passivation film) on an outermost surface, and therefore
originally they are materials difficult to plate and the materials
difficult to solder. However, by forming the underlayer (adhesive
layer) 7 and the surface layer (bonding layer) 8 formed of the
aforementioned sputter film, excellent solder wettability and
bonding strength to soldering can be given to the surface of the
fin substrate 6 made of aluminum or an aluminum-based alloy having
the passivation film formed on the outermost surface, even if not
removing the passivation film that exists on the outermost surface
of the fin substrate 6 through acid pickling.
[0044] The tube member 2 is obtained by molding a tube plate
material 10 shown in FIG. 3 into a pipe shape having, for example,
a flat elliptic or rectangular sectional face, with a solder film
layer 12 formed on its surface disposed outside. The tube member 2
is provided so as to be bridged between the right and left tank
members 3, and serves as a conduit for guiding the refrigerant such
as cooling water 4 from the tank member 3 of one side to the tank
member 3 of the other side.
[0045] The tube plate material 10 includes the solder film layer 12
made of solder containing tin (Sn) on the whole surface or in at
least a part of the tube substrate 11 made of metal containing
copper or mainly composed of copper such as brass where the tube
member 1 and the fin member 2 are joined each other.
[0046] According to a preferable numerical aspect, a thickness of
the solder film layer 12 is set to 3 .mu.m or more and 100 .mu.m or
less.
[0047] This is because it is highly possibly difficult to obtain a
satisfactory joint if the film thickness is less than 3 .mu.m, and
also there is a high possibility that if the thickness is beyond
100 .mu.m, the solder film layer 12 itself is easily peeled-off
after joint or crack is easily generated, and also there is a high
possibility that a material cost is increased for forming the thick
solder film layer 12.
[0048] Further, according to a preferable aspect, it is also
possible to make the solder film layer 12 made of pure tin, and not
allow lead (Pb) and cadmium (Cd), etc, to be contained in the
component of the whole body of the solder film layer 12. Thus, the
joint is surely achieved by so-called lead-free soldering.
[0049] Further, according to a preferable numerical aspect, when
the solder film layer 12 is made of pure tin, the thickness is set
to 3 .mu.m or more and 30 .mu.m or less.
[0050] This is because when the thickness is made to be excessively
thin like less than 3 .mu.m or when the thickness is made to be
excessively thick like more than 30 .mu.m, there is a high
possibility that the sure joint can not be achieved. Further
specifically, this is because although satisfactory diffusion
bonding is realized by diffusion of copper of the solder wetting
film layer 5 toward pure tin of the film layer 12, at this time, if
the film layer 12 made of pure tin is excessively thick, a
sufficient diffusion is not carried out, and the satisfactory joint
can not be achieved, and reversely when the film layer 12 is
excessively thin, a function of securing wettability during joint
can not be sufficiently exhibited, and the satisfactory joint can
not be achieved.
[0051] Further, particularly when the thickness of the solder film
layer 12 made of pure tin is beyond 30 .mu.m, joint is made by
diffusion of the copper of the surface layer of the fin member 1
during heating in a soldering process for joint. There is also a
possibility that inconvenience occurs, such that a copper
concentration is decreased.
[0052] The tank member 3 is constituted, so that the refrigerant
such as high temperature cooling water 4 sent from, for example, an
engine is distributed and supplied to the tube member 2 by the tank
member 3 of one side, and the cooling water 4 passed through the
tube member 2 and cooled is recovered and returned to the engine by
the tank member 3 of the other side.
[0053] As shown in FIG. 4, for example in the same way as the case
of the tube plate material 10, the tank plate material 13 can be
used, with the solder film layer 12 made of solder containing tin
provided on the surface of the tank substrate 14 made of metal
containing copper or mainly composed of copper. Alternatively, when
there is no necessity for being joined to the fin member 1, the
solder film layer 12 on the surface of the tank plate material 13
can also be omitted, provided that a sure (with high water
tightness) joint between the fin member 1 and the tube member 2
made of copper-based metal is secured by general soldering, etc.
Alternatively, the tank member 3 may also be made of a material
other than metal, provided that the joint capable of securing the
water tightness against the tube member 2 is achieved.
[0054] As described above, the fin member 1, the tube member 2, and
the tank member 3 are assembled, and a contact part of them are
joined each other in each essential part, to thereby constitute the
main essential part of the heat exchanger (a connection structure
of the heat exchanger is simulated) according to the first
embodiment of the present invention, as shown in FIG. 5 and FIG. 6.
Here, in the structure of the heat exchanger shown in FIG. 5 and
FIG. 6, a sample of the connection structure is shown, and
therefore the tube member 2 is not formed into a flat tube-like
shape, but substantially formed into a shape obtained by cutting
the flat tube into about half.
[0055] The heat exchanger thus formed has a solder wetting film
layer 5 containing copper in at least a part of the surface of the
fin substrate 6 made of aluminum or an alloy mainly composed of
aluminum where the fin member 1 and the tube member 2 are joined
each other; and has the solder film layer 12 made of solder
containing tin in at least a part of the surface of the tube
substrate 11 made of metal containing copper and mainly composed of
copper where the tube member 1 and the fin member 1 are joined each
other, so that the fin member 1 and the tube member 2 are joined
each other through a diffusion bonding (diffusion joining) of the
copper component of the solder wetting film layer 5 and the tin
component of the solder film layer 12.
[0056] In the heat exchanger of the first embodiment formed as
described above, the fin member 1 and the tube member 2 are
temporarily assembled and thereafter heat treatment is applied
thereto, to thereby cause mutual heat diffusion of the copper
component of the melted solder wetting film layer 5 or particularly
the surface layer 8 in the structure of the first aspect (the
copper component can be diffused to outside from the film by being
melted; the same thing can be said hereinafter), and the tin
component of the melted solder film layer 12 on the surface of the
tube member 2. Then, a metal diffusion bonding is thereby formed,
and as a result, satisfactory solder joint can be surely
obtained.
[0057] As described above, according to the heat exchanger of the
first embodiment, a satisfactory joint can be surely realized,
between the fin member 1 made of aluminum or an alloy mainly
composed of aluminum, and the tube member 2 made of copper or a
copper-based alloy, without using a flux with excessively strong
activity, and without using a joint method which is complicated
like aluminum brazing and incurs a high cost.
[0058] Further, the fin member 1 is made of aluminum or the alloy
mainly composed of aluminum, and the tube member 2 is made of the
copper-based alloy such as brass. Therefore, both decrease of a
weight and improvement of a corrosion resistance of the heat
exchanger manufactured by using the aforementioned fin member 1 and
the tube member 2, is achieved.
[0059] Further, when the solder film layer 12 made of pure tin is
used, a so-called Pb-free solder joint is possible, and therefore
manufacture of an environmentally-friendly heat exchanger is
realized.
The Heat Exchanger According to a Second Embodiment
[0060] In the heat exchanger according to the second embodiment,
the fin member 1 as shown in FIG. 7 is used. Namely, the fin member
1 is formed by further adding the solder film layer 12 to the
outermost surface of the fin plate material 9 of the first
embodiment, and folding and bending this fin plate material 9 into
a prescribed wave shape. The fin member 1 is disposed in such a
manner as being sandwiched between the adjacent two tube members 2
and 2, so that each part where the tube member 2 and the fin member
1 are brought into contact with each other, is surely joined each
other. Moreover, the fin member 1 is disposed in such a manner as
being sandwiched between right and left tank members 3. The fin
member 1 and the tank member 3 may be joined each other or may be
set in a state of simply being brought into contact with each other
mechanically.
[0061] Further specifically, the fin member 1 has the solder
wetting film layer 5 containing copper, on approximately the whole
surface of the fin substrate 6 made of aluminum or mainly composed
of aluminum, or at least in part of the surface thereof where the
fin member 1 and the tube member 2 are joined each other.
[0062] According to a preferable numerical aspect, the thickness of
the solder wetting film layer 5 is set to 10 nm or more and 400 nm
or less, for the same reason described in the first embodiment.
[0063] According to a preferable aspect of the present invention,
as schematically shown in FIG. 7, here, the solder wetting film
layer 5 has a two-layer lamination structure of the underlayer 7
made of niobium or chromium, and the surface layer 8 made of an
alloy mainly composed of copper and added with at least one kind of
metal of nickel and zinc, provided on the surface of the underlayer
7, also for the same reason as described in the first
embodiment.
[0064] Further, in the solder wetting film layer 5 having the
aforementioned two-layer lamination structure, preferably, the
underlayer (adhesive layer) 7 made of niobium or chromium, is the
sputter film made of niobium or chromium, and the internal residual
stress of the sputter film is set as the compressive stress or the
zero stress, and the surface layer (bonding layer) 8 mainly
composed of copper and added with at least one kind of metal of
nickel and zinc, is the sputter film. Further, it is preferable to
set an oxygen amount contained in the underlayer (adhesive layer) 7
and the surface layer (bonding layer) 8 to be extremely small, and
when the underlayer (adhesive layer) 7 and the surface layer
(bonding layer) 8 are formed by sputtering, film formation is
performed in a film forming atmosphere in which oxygen is removed
as much as possible. Further, the thickness of the underlayer
(adhesive layer) 7 is set to 10 nm or more and the thickness of the
surface layer (bonding layer) 8 is set to 15 nm or more. Such a
structure is preferable, also for the same reason as described in
the first embodiment.
[0065] The solder film layer 12 made of solder containing tin, is
provided on the surface of the solder wetting film layer 5.
According to a preferable numerical aspect, the thickness of the
solder film layer 12 is set to 3 .mu.m or more and 100 .mu.m or
less.
[0066] This is because it is highly possibly difficult to obtain a
satisfactory joint if the film thickness is less than 3 .mu.m, and
also there is a high possibility that if the thickness is beyond
100 .mu.m, the solder film layer 12 itself is easily peeled-off
after joint or crack is easily generated, and also there is a high
possibility that a material cost is increased for forming the thick
solder film layer 12.
[0067] Further according to a preferable aspect, it is also
possible to make the solder film layer 12 made of pure tin, and not
allow lead (Pb) and cadmium (Cd), etc, to be contained in the
component of the whole body of the solder film layer 12. Thus, the
joint is surely achieved by so-called lead-free soldering.
[0068] When the solder film layer 12 is made of pure tin, it is a
preferable numerical aspect that the thickness is set to 3 .mu.m or
more and 30 .mu.m or less. This is because there is a high
possibility that sure joint can not be obtained, when the thickness
is set to be excessively thin like less than 3 .mu.m, or is set to
be excessively thick like beyond 30 .mu.m. Further, particularly
when the thickness of the solder film layer 12 made of pure tin is
beyond 30 .mu.m, joint is made by diffusion of the copper on the
surface layer of the fin member 1 during heating in the soldering
process for joint. There is a possibility that inconvenience
occurs, such that a copper concentration is decreased.
[0069] Although not shown, the tube member 2 is formed by molding
the tube plate material 10 into a flat pipe shape having, for
example, an elliptic or rectangular sectional face, wherein the
tube plate material 10 is made of only the tube substrate 11, which
is made of metal containing copper or mainly composed of copper
such as brass. Namely, the tube plate material of the second
embodiment is obtained by omitting the solder film layer 12 from
the tube plate material 10 as shown in FIG. 3. The tube member 2 is
provided so as to be bridged between the right and left tank
members 3 and 3, serving as a conduit for guiding the refrigerant
such as cooling water 4 from the tank member 3 of one side to the
tank member 3 of the other side.
[0070] The tank member 3 is constituted, so that the refrigerant
such as high temperature cooling water 4 sent from, for example, an
engine is distributed and supplied to the tube member 2 by the tank
member 3 of one side, and the cooling water 4 passed through the
tube member 2 and cooled is recovered and returned to the engine by
the tank member 3 of the other side.
[0071] The tank plate material 13 can be used, having the solder
film layer 12 made of solder containing tin provided on the surface
of the tank substrate 14 made of an alloy containing copper or
mainly composed of copper. Alternatively, when there is no
necessity for being joined to the fin member 1, the solder film
layer 12 on the surface of the tank plate material 13 can also be
omitted, provided that a sure (with high water tightness) joint
between the fin member 1 and the tube member 2 made of copper-based
metal is secured by general soldering, etc. Alternatively, the tank
member 3 may also be made of a material other than metal, provided
that the water tightness against the tube member 2 is secured by
jointing.
[0072] As described above, the fin member 1, the tube member 2, and
the tank member 3 are temporarily assembled, and thereafter a
contact part of them are joined each other in each essential part,
to thereby constitute the main essential part of the heat exchanger
(a connection structure of the heat exchanger is simulated)
according to the second embodiment of the present invention.
[0073] Namely, in the heat exchanger according to the second
embodiment, the solder wetting film layer 5 containing copper and
the solder film layer 12 further formed on the surface of the
solder wetting film layer 5 are provided at least in a part of the
surface of the fin substrate 6 made of aluminum or an alloy mainly
composed of aluminum where the fin member 1 is brought into contact
with the tube member 2. Further, the tube member 2 is formed by
molding the tube plate material 10 into a tube shape, wherein the
tube substrate 11 itself made of copper or mainly composed of
copper is used as the tube plate material 10, and the fin member 1
and the tube member 2 are joined each other, mainly through the
diffusion bonding of the copper component of the tube member 2 and
the tin component of the solder film layer 12.
[0074] In the heat exchanger according to the second embodiment,
the fin member 1 and the tube member 2 are temporarily assembled,
and thereafter heat treatment is applied thereto, and heat
diffusion of copper and tin is caused in a melted solder between
the fin member 1 and the tube member 2, to thereby form a metal
diffusion bonding, and as a result satisfactory solder joint
between the fin member 1 and the tube member 2 can be surely
achieved.
[0075] As described above, according to the heat exchanger of the
first embodiment, the satisfactory joint can be surely realized,
between the fin member 1 made of aluminum or an alloy mainly
composed of aluminum, and the tube member 2 made of copper or a
copper-based alloy, without using a flux with excessively strong
activity, and without using a joint method such as aluminum brazing
which is complicated and requires a high cost.
[0076] Further, the fin member 1 can be made of aluminum or the
alloy mainly composed of aluminum, and the tube member 2 can be
made of the copper-based alloy such as brass. Therefore, both
decrease of a weight and improvement of the corrosion resistance of
the heat exchanger manufactured by using the aforementioned fin
member 1 and the tube member 2, is achieved.
[0077] Further, when the solder film layer 12 made of pure tin is
used, a so-called Pb-free solder joint is also possible, and
therefore manufacture of the environmentally-friendly heat
exchanger is realized.
Examples
[0078] The fin member 1, tube member 2, and tank member 3 described
in the aforementioned embodiments were prepared, and a trial model
was manufactured by joining these members, to thereby evaluate and
examine the joint.
Example 1
[0079] According to the first embodiment, as example 1, the trial
model of the heat exchanger having the structure as shown in FIG. 5
and FIG. 6 was manufactured and its joint state was evaluated.
[0080] First, the fin member 9 having the structure as shown in
FIG. 2, the tube plate material 10 having the structure as shown in
FIG. 3, and the tank member 13 having the structure as shown in
FIG. 4 were manufactured.
[0081] As the fin substrate 6, being the substrate of the fin plate
material 9, a hard material of A5052, being an Al--Mg alloy (Al--Mg
based alloy defined in JIS, containing 2.2 to 2.8 wt % of Mg)
having thickness of t=50 .mu.m, width of W1=16 mm, and length of 40
mm, was used.
[0082] As the tube substrate 11, being the substrate of the tube
plate material 10, a brass material having a composition of Cu--35
wt % Zn, and having thickness of 230 .mu.m, width W2=20 mm, and
length of 80 mm, was used.
[0083] Also, as the tank substrate 14, being the substrate of the
tank plate material 13, the brass material which is the same as the
material of the tube plate material 10, and having thickness of 500
.mu.m, width W3=30 mm, and length (height) H of 60 mm, was
used.
[0084] Then, the solder wetting film layer 5 (underlayer 7 and the
surface layer 8) as described in the first embodiment, was formed
on the surface of the fin substrate 6 by sputtering, and the solder
film layer 12 was formed on the surface of the tube substrate 11
and the tank substrate 14, respectively.
[0085] Further, these substrates are molded into prescribed shapes,
to thereby manufacture the fin member 1, the tube member 2, and the
tank member 3, then after such members are temporarily assembled,
heat treatment is applied thereto, to thereby join essential parts
by soldering, and the trial model of the heat exchanger having the
structure as shown in FIG. 5 and FIG. 6 was manufactured.
[0086] As the underlayer 7 in the solder wetting film layer 5 of
the fin member 1, there are two kinds of layers made of niobium
(Nb) (samples 1 to 21 of FIG. 9), and the layer made of chromium
(Cr) (samples 22 to 41 of FIG. 10). However, as the surface layer 8
combined with the aforementioned two kinds of underlayers 7, the
layer made of copper (Cu)--20 wt % nickel (Ni) was used in both
cases. The thickness of the underlayer 7 was set to 20 nm, and the
thickness of the surface layer 8 was set to 60 nm.
[0087] A wave-shaped pitch D1 of the fin member 1 shown in FIG. 5
was set to 30 mm. Further, total length D2 of the tube member 2 and
the tank member 3 assembled to both ends of the tube member 2 was
set to 60 mm.
[0088] Then, three kinds of the tube members 2, with the solder
film layer 12 made of Sn, made of Sn--37 wt % Pb, and made of Sn--3
wt % Bi (bismuth), were prepared for the sample of the two kinds of
fin members 1, and heat treatment is applied thereto, to thereby
join the fin members 1 and the tube members 2 each other.
[0089] As a forming method of the solder film layer 12 on the
surface of the tube member 2, two kinds of methods were tried, such
as an electric plating method and a hot dipping method.
[0090] Then, the fin member 1, the tube member 2, and the tank
member 3 were joined each other by heat treatment, to thereby
manufacture the trial model of the heat exchanger having the
structure as shown in FIG. 5 and FIG. 6.
[0091] More specifically, the fin member 1, the tube member 2, and
the tank member 3 were temporarily assembled into a prescribed
structure, and thereafter RMA type (model number; HS-722, by HOZAN
Inc.) with low activity as flux was applied thereto, to thereby
perform joint by heat treatment for 3 seconds at 200.degree. C. to
260.degree. C., and a joint state of the fin member 1 and the tube
member 2 was evaluated.
[0092] Regarding the evaluation method of the joint state between
the fin member 1 and the tube member 2 immediately after joint by
heat treatment, the evaluation method in a quality
management/inspection of this kind of heat exchanger was used.
Namely, absolutely no joint state visually is judged to be "without
joint", and a state, in which the fin member 1 and the tube member
2 are easily separated from each other when a load is added thereto
even in a state of joint, is judged to be "failure", and a state,
in which the fin member 1 and the tube member 2 are not easily
separated from each other, is judged to be "excellent". Further
regarding the sample judged to be "excellent", a salt water spray
test using salt water at 35.degree. C. containing 5.0% salt was
performed for 96 hours, as an environmental test. Then, regarding
the joint state after performing the salt water spray test, in the
same way as the case of judgment immediately after joint, the
state, in which the fin member 1 and the tube member 2 were easily
separated from each other, was judged to be "failure", and the
state, in which the fin member 1 and the tube member 2 were not
easily separated from each other, was judged to be "excellent".
[0093] A judgment (evaluation) result of the joint of samples 1 to
41 according to example 1 will be described hereinafter, in further
detail.
[0094] FIG. 9 shows the result, in a case that the underlayer 7 of
the fin member 1 is made of Nb, and in a case that the surface
layer 8 is made of Cu--20 wt % Ni.
[0095] As shown in FIG. 9, in the samples No. 1 to 21 in which
niobium (Nb) was selected as the material of the solder wetting
film layer 5 of the fin member 1, approximately excellent joint was
achieved. Meanwhile, in the samples No. 1 to No. 9, pure tin was
selected as the material of the solder film layer 12 of the tube
member 2, and in the sample No. 1 of comparative example 1, the
thickness of the solder film layer 12 was 1.5 .mu.m and excessively
thin, and therefore the state of this sample was judged to be
"without joint".
[0096] Further, in the sample No. 2 of the comparative example 1,
the thickness of the solder film layer 12 was 2 .mu.m and very
thin, and therefore it is so judged that the joint immediately
after heat treatment was "excellent", but the joint after
performing the salt water spray test was "failure". Reversely, in
the sample No. 8 of the comparative example 1, the thickness of the
solder film layer 12 was 40 .mu.m and excessively thick, and
therefore the joint immediately after heat treatment was judged to
be "failure".
[0097] Thus, generation of the failure of the joint due to
thickness of the solder film layer 12, which is thin or thick, has
the same tendency in both cases of a case of the sample No. 10 to
No. 18 in which Sn--37 wt % Pb is selected as the material of the
solder film layer 12, and a case of the sample No. 19 to No. 21 in
which Sn--3 wt % Bi is selected as the material of the solder film
layer 12. Namely, in the sample No. 10 and sample No. 11 of the
comparative example 1, the thickness was set thin to 1.5 .mu.m and
2 .mu.m, and therefore the joint immediately after heat treatment
was "excellent", but the joint after performing the salt water
spray test was "failure". Reversely, in the sample No. 17 of the
comparative example 1 in which the thickness was set excessively
thick to 120 .mu.m, the joint immediately after heat treatment was
"failure".
[0098] From the result as described above, it was confirmed that
the thickness of the solder film layer 12 was desirably set to 3
.mu.m or more and 100 .mu.m or less. Also particularly it was
confirmed that the film thickness was desirably set to 3 .mu.m or
more and 30 .mu.m or less when pure tin was used as the solder film
layer 12.
[0099] Further, when the thickness of the solder film layer 12 was
set within a range of the above-described numerical aspect, it was
confirmed that excellent joint could be achieved, irrespective of
the forming method of the solder film layer 12, namely in either
case of the electroplating method or the hot dipping method.
[0100] FIG. 10 shows the result of a case in which Cr is selected
to be the material of the underlayer 7 of the fin member 1, and
also Cu--20 wt % Ni is selected to be the material of the surface
layer 8.
[0101] In this case also, approximately the same result was
obtained as the case in which Nb was selected to be the material of
the underlayer 7. However, in this case, regarding the sample No.
31 in which the thickness of the solder film layer 12 made of
Sn--37 wt % Pb was set to 1.5 .mu.m, "failure" was already shown
immediately after heat treatment, unlike the above-described sample
No. 11. However, in each case, it was confirmed from this result,
that if the thickness of the solder film layer 12 was excessively
thin like less than 3 .mu.m, the excellent joint could not be
achieved.
Example 2
[0102] According to second embodiment, as example 2, the trial
model of the heat exchanger having the structure as shown in FIG.
8, was manufactured and its joint state was evaluated.
[0103] First, the fin plate material 9 having the structure as
shown in FIG. 7, the tube plate material 10 (not shown), and the
tank plate material 13 having the structure as shown in FIG. 4,
were manufactured.
[0104] As the fin substrate 6, being the substrate of the fin plate
material 9, a hard material of A3004, being an Al--Mn alloy (Al--Mn
based alloy defined in JIS, containing 1.0 to 1.5 wt % of Mn)
having thickness of t=60 .mu.m, and width of W1=16 mm, was
used.
[0105] As the tube substrate 11, being the substrate of the tube
plate material 10, a brass material having a composition of Cu--35
wt % Zn, thickness of 230 .mu.m, width W2=20 mm, and length of 40
mm, was used.
[0106] Also, as the tank substrate 14, being the substrate of the
tank plate material 13, the brass material which was the same as
the material of the tube plate material 10, and having thickness of
500 .mu.m, width W3=30 mm, length of 80 mm, and height of 60 mm,
was used.
[0107] Then, the solder wetting film layer 5 (underlayer 7 and the
surface layer 8) as described in the second embodiment, was formed
on the surface of the fin substrate 6 by sputtering, and the solder
film layer 12 was further formed thereon, and the fin substrate 6
thus formed was molded into a prescribed shape, to thereby
manufacture the fin member 1.
[0108] Further, the tube substrate 11 was used as it is, and
molding process was applied thereto, to thereby manufacture the
tube member 2.
[0109] Moreover, the solder film layer 12 was provided on the
surface of the tank substrate 14, and molding treatment was applied
thereto, to thereby manufacture the tank member 3.
[0110] Then, the fin member 1, the tube member 2, and the tank
member 3 were temporarily assembled, and thereafter heat treatment
was applied thereto, and the essential parts were joined each other
by soldering, to thereby manufacture the trial model of the heat
exchanger having the structure as shown in FIG. 8.
[0111] As the underlayer 7 in the solder wetting film layer 5 of
the fin member 1, there are two kinds of layer made of niobium (Nb)
(samples 1 to 24 of FIG. 11), and the layer made of chromium (Cr)
(samples 25 to 48 of FIG. 12). However, as the surface layer 8
combined with the aforementioned two kinds of underlayers 7, the
layer made of Cu--20 wt % Ni was used in both cases. The thickness
of the underlayer 7 was set to 20 nm, and the thickness of the
surface layer 8 was set to 60 nm.
[0112] Further, the solder film layer 12 was formed on the surface
of the solder wetting film layer 5. Then, three kinds of the solder
film layers 12, such as the solder film layer 12 made of Sn, made
of Sn--37 wt % Pb, and made of Sn--3 wt % Bi, were prepared.
[0113] As the forming method of the solder film layer 12, two
methods were tried in the samples No. 1 to No. 48 of the example 2
(including comparative example 2), such as the electroplating
method without cathodic degrease as preprocessing, and the
electroplating method with cathodic degrease as preprocessing. The
cathodic degrease was carried out by using a sodium hydroxide
solution at temperature of 50.degree. C., with the sample set as a
cathode, and under a condition that a current of 1.7 A/dm.sup.2
flows. Although the hot dipping method was also tried, excellent
solder plating was not achieved.
[0114] The fin member 1, the tube member 2, and the tank member 3
thus manufactured were temporarily assembled into prescribed
structures, and they were joined by soldering by applying heat
treatment thereto, to thereby obtain the trial model of the heat
exchanged having the structure as shown in FIG. 8.
[0115] More specifically, the fin member 1, the tube member 2, and
the tank member 3 were temporarily assembled into prescribed
structures, and thereafter RMA type (model number; HS-722, by HOZAN
Inc.) with low activity as flux was applied thereto, to thereby
perform joint by heat treatment for 3 seconds at 200.degree. C. to
260.degree. C., and a joint state thereof was evaluated.
[0116] Regarding the evaluation method of the joint state between
the fin member 1 and the tube member 2 after joint by heat
treatment, in the same way as the case of the example 1, the
evaluation method in a quality management/inspection of this kind
of heat exchanger was used. Namely, absolutely no joint state
visually is judged to be "without joint", and a state, in which the
fin member 1 and the tube member 2 are easily separated from each
other when a load is added thereto even in a state of joint, is
judged to be "failure", and a state, in which the fin member 1 and
the tube member 2 are not easily separated from each other, is
judged to be "excellent". Further regarding the sample judged to be
"excellent", a salt water spray test using salt water at 35.degree.
C. containing 5.0% salt was performed for 96 hours, as an
environmental test. Then, regarding the joint state after
performing the salt water spray test, in the same way as the case
of judgment immediately after joint, the state, in which the fin
member 1 and the tube member 2 were easily separated from each
other, was judged to be "failure", and the state, in which the fin
member 1 and the tube member 2 were not easily separated from each
other, was judged to be "excellent".
[0117] A judgment (evaluation) result of the joint of samples 1 to
48 according to example 2 will be described hereinafter, in further
detail.
[0118] FIG. 11 shows the result, in a case that the underlayer 7 of
the fin member 1 is made of Nb, and in a case that the surface
layer 8 is made of Cu--20 wt % Ni.
[0119] In the samples No. 1 to No. 24 in which niobium (Nb) was
selected as the material of the underlayer 7 of the fin member 1,
approximately excellent joint was achieved regarding the samples in
which no cathodic degrease was carried out before performing
electroplating of the solder film layer 12 (samples of "without
cathodic degrease" in FIG. 11). The result was examined in further
detail. In samples No. 1 to No. 10, pure tin was selected as the
material of the solder film layer 12 of the tube member 2, and in
the sample No. 1 of the comparative example 2, the thickness of the
solder film layer 12 was 1.5 .mu.m and excessively thin. Therefore
the joint was judged to be "without joint". Further, in the sample
No. 2 of the comparative example 2, the thickness of the solder
film layer 12 was 2 .mu.m and thin. Therefore although the joint
immediately after heat treatment was judged to be "excellent", the
joint after salt water spray test was judged to be "failure".
Moreover, in the sample No. 7, the thickness of the solder film
layer 12 was 40 .mu.m and thick. Therefore the joint immediately
after heat treatment was judged to be "failure".
[0120] Thus, the generation of the failure of the joint due to
thickness of the solder film layer 12, which is thin or thick, has
the same tendency in both cases of a case of the sample No. 11 to
No. 21 in which Sn--37 wt % Pb is selected as the material of the
solder film layer 12, and a case of the sample No. 22 to No. 24 in
which Sn--3 wt % Bi is selected as the material of the solder film
layer 12. However, in these cases, a suitable thickness for
achieving the excellent joint was 3 .mu.m or more and 100 .mu.m or
less. From such a result, it was confirmed that the thickness of
the solder film layer 12 was desirably set to at least 3 .mu.m or
more and 100 .mu.m or less, and particularly in a case of the
solder film layer 12 made of pure tin, the film thickness was
desirably set to 3 .mu.m or more and 30 .mu.m or less.
[0121] Further, when the cathodic degrease was carried out as the
preprocessing of the electroplating (samples No. 8 to No. 10, No.
19 to No. 21 of the "with cathodic degrease" in FIG. 11), all of
the samples were judged to be "without joint", irrespective of the
thickness.
[0122] From this fact, it was found that when the solder film layer
12 was formed by the electroplating method, on the surface of the
solder wetting film layer 5 made of niobium (Nb), it is one of the
conditions for achieving the excellent joint, to perform
electroplating of the solder film layer 12 in a state of not
carrying out the cathodic decrease, irrespective of the
thickness.
[0123] Note that it is desirable to carry out degrease processing
as the preprocessing of the electroplating, although the cathodic
degrease is not carried out. Namely, when the solder film layer 12
is formed by the electroplating method, on the surface of the
solder wetting film layer 5 made of niobium (Nb), it is desirable
to carry out the degrease processing, other than the cathodic
degrease, so that joint failure is not generated.
[0124] FIG. 12 shows the result of a case in which chromium (Cr) is
selected as the material of the underlayer 7 of the fin member 1,
and copper Cu--20 wt % Ni is selected as the material of the
surface layer 8.
[0125] When chromium (Cr) was selected as the material of the
underlayer 7, unlike the case of the niobium (Nb), no joint failure
was generated, due to the cathodic degrease which was carried out.
Regarding the other point, the same tendency was shown as the case
of the niobium (Nb).
[0126] Here, it is generally desirable to carry out degreasing, as
the preprocessing of the electroplating. This is because if grease,
etc, is adhered to the surface to be plated in a manufacturing
step, there is a high possibility that the adhesion of grease, etc,
becomes a factor of generating defects, etc, in an electroplating
film. From this viewpoint, if the underlayer 7 is made of chromium
(Cr), this is preferable because degreasing of the underlayer 7 is
possible by cathode electrolysis using, for example, alkali
solution, even if the grease, etc, is adhered to the underlayer
7.
[0127] The underlayer 7 made of niobium (Nb) absorbs hydrogen
during cathodic degrease, and an original function as a base can
not be fulfilled, and this is considered to be the factor of
generating the joint failure due to the cathodic degrease. When the
underlayer 7 is made of chromium (Cr), the joint failure does not
occur, and the reason therefore is considered that hydrogen
absorption does not occur during cathodic degrease in the
underlayer 7 made of chromium.
[0128] As described above, according to the example of the present
invention, it was confirmed that excellent solder joint was
achieved by setting the material and the thickness of the solder
wetting film layer 5 and the solder film layer 12 to the
aforementioned appropriate values.
[0129] Note that in the above-described example, explanation is
given for a case of using pure tin, an alloy of tin and lead, and
an alloy of tin and bismuth, as a base material (main component) of
solder. However, the solder base material is not limited
thereto.
[0130] Also, each kind of specific design specification such as
thickness and outer dimension of each substrate of the fin member
1, tube member 2, and tank member 3, is not limited to the
structure given in the above-described examples.
[0131] Further, for example when only one surface of the fin member
1 is joined to the tube member 2, the solder wetting film layer 5,
the solder film layer 12 may be formed on only one surface of the
fin substrate 6. It is needless to say that various variations are
possible other than the above-described examples.
[0132] The present application is based on Japanese Patent
Application No. 2009-051974, filed on Mar. 5, 2009, the entire
contents of which are hereby incorporated by reference.
* * * * *