U.S. patent application number 10/170193 was filed with the patent office on 2003-01-09 for lead-free solder.
Invention is credited to Domi, Shinjiro, Nakagaki, Shigeki, Sakaguchi, Koichi, Suganuma, Katsuaki.
Application Number | 20030007885 10/170193 |
Document ID | / |
Family ID | 27300067 |
Filed Date | 2003-01-09 |
United States Patent
Application |
20030007885 |
Kind Code |
A1 |
Domi, Shinjiro ; et
al. |
January 9, 2003 |
Lead-free solder
Abstract
Lead-free solder comprising Sn, Zn and 0.001 to 0.005 wt. % Ti.
The lead-free solder does not contain toxic lead, and has
sufficient bonding strength to oxide materials such as glass and
ceramics.
Inventors: |
Domi, Shinjiro; (Osaka,
JP) ; Sakaguchi, Koichi; (Osaka, JP) ;
Nakagaki, Shigeki; (Osaka, JP) ; Suganuma,
Katsuaki; (Osaka, JP) |
Correspondence
Address: |
KANESAKA AND TAKEUCHI
1423 Powhatan Street
Alexandria
VA
22314
US
|
Family ID: |
27300067 |
Appl. No.: |
10/170193 |
Filed: |
June 13, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10170193 |
Jun 13, 2002 |
|
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PCT/JP00/01422 |
Mar 9, 2000 |
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10170193 |
Jun 13, 2002 |
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09703882 |
Nov 2, 2000 |
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Current U.S.
Class: |
420/557 ;
420/560 |
Current CPC
Class: |
B23K 35/262 20130101;
B23K 35/282 20130101 |
Class at
Publication: |
420/557 ;
420/560 |
International
Class: |
C22C 013/00; C22C
013/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 16, 1999 |
JP |
H11-69505 |
Feb 24, 2000 |
JP |
2000-47325 |
Claims
What is claimed is:
1. Lead-free solder comprising Sn, Zn and 0.001 to 0.005 wt. % of
Ti.
2. Lead-free solder as claimed in claim 1, wherein a ratio of Sn to
Zn (Sn/Zn) is 4.0 to 19.0.
3. Lead-free solder as claimed in claim 1, wherein the ratio of Sn
to Zn (Sn/Zn) is 9.0 to 12.0, and said solder contains
substantially no Cu.
4. Lead-free solder consisting essentially of Sn, Zn, 0.001 to
0.005 wt. % of Ti, and 0.001 to 0.005 wt. % of Al, wherein a ratio
of Sn to Zn (Sn/Zn) is 4.0 to 19.0.
5. Lead-free solder consisting essentially of Sn, Zn, 0.001 to
0.005 wt. % of Ti, and 0.001 to 9.0 wt. % of Cu wherein a ratio of
Sn to Zn (Sn/Zn) is 4.ltoreq.Sn/Zn<9 and
12<Sn/Zn.ltoreq.19.
6. Lead-free solder consisting essentially of Sn, Zn, 0.001 to
0.005 wt. % of Ti, 0.001 to 0.005 wt. % of Al, and 5.0 to 9.0 wt. %
of Cu, wherein a ratio of Sn to Zn (Sn/Zn) is 4.ltoreq.Sn/Zn<9
and 12<Sn/Zn.ltoreq.19.
7. Lead-free solder consisting essentially of Sn, Zn, 0.001 to
0.005 wt. % of Ti, and at least one element selected from a group
consisting of Bi, Si and Sb in a range of 3.2 to 10 wt. %, wherein
a ratio of Sn to Zn (Sn/Zn) is 4.0 to 19.0.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This is a continuation application of PCT/JP00/01422 filed
on Mar. 9, 2000, and a continuation-in-part application of U.S.
Ser. No. 09/703,882 filed on Nov. 2, 2000.
FIELD OF THE INVENTION
[0002] The present invention relates to lead-free solder for
soldering an oxide material, such as ceramics and glass at a low
temperature.
BACKGROUND OF THE INVENTION
[0003] Electroplating or electroless plating such as gold plating,
copper plating, and nickel plating is conducted on an oxide
material including ceramics and glass before soldering thereof.
However, another pre-plating method preceding soldering is desired
because the above plating is expensive and complicated.
[0004] Solder of Pb--Sn which can be soldered directly to glass and
ceramics is disclosed in Japanese patents S49-22299B and
S52-21980B.
[0005] However, lead is toxic on the health, the environment, and
the ecosystem, so lead-free solder is desired.
[0006] The solder of Pb--Sn--Cd--Sb disclosed in the above Japanese
patent 49-22299B is possible to be soldered directly to an oxide
material such as glass and ceramics. However, toxic lead eluates
from the solder in quantity to cause serious problem, to the
environment, when the solder contacts acid rain.
[0007] The solder disclosed in the above Japanese patent S52-21980B
contains rare earth materials which are useful for joining oxide
materials such as glass and ceramics. However, the solder has the
same problems as above, because it comprises lead as a main
component.
[0008] Lead-free solder has been investigated for mounting
electronic parts. For example, solder of Sn--Ag--In is disclosed in
Japanese patent H9-326554A, and solder of Sn--Zn--Bi system is
disclosed in Japanese patent H8-164495A. However, their bonding
strength are not enough to metal oxide materials such as glass and
ceramics.
[0009] Solder of Sn--Ag--Al--Zn for soldering metal oxides is
disclosed in Japanese patent S55-36032B. This solder easily
separates from oxide material such as glass and ceramics, because
the coefficient of thermal expansion of the solder is greatly
different from that of the oxide material.
[0010] The above solders can be used as a sealing material which
seals a periphery of a double-glazing unit comprising two glass
plates arranged parallel with a space therebetween. When
manufacturing the double-glazing unit, the solder is introduced
from a solder feeding apparatus having a solder tank and a feeding
line to the space between the glass plates via an introducing plate
which is inserted into the space.
[0011] However, when the conventional solder is fed into the solder
tank and kept for a predetermined time, a (Sn, Zn) Ti series
compound is deposited on a bottom of the solder tank, whereby the
compound blocks the feeding line of the solder feeding apparatus
and the solder can not be fed stably.
DISCLOSURE OF THE INVENTION
[0012] It is an object of the present invention to solve problems
of prior art mentioned above and to provide lead-free solder
comprising no toxic lead, being capable of bonding strongly to
oxide materials such as glass and ceramics and preventing producing
the above (Sn, Zn), Ti series compound so that the solder can be
fed stably.
[0013] The solder of the present invention comprises Sn and Zn as
main components and further comprises at least one of Ti, Al and
Cu.
[0014] It should be noted that a content value of each component
represents a mean composition in the solder because Zn, Ti and Al
in the solder are very easily oxidized, and tend to segregate at
the surface of the solder.
[0015] A first aspect of the lead-free solder of the present
invention comprises Sn, Zn and 0.001 to 0.005 wt. % Ti.
[0016] The lead-free solder of the present invention may further
comprise 0.001 to 0.005 wt. % Al.
[0017] The lead-free solder of the present invention may further
comprise 5.0 to 9.0 wt. % Cu.
[0018] The lead-free solder of the present invention preferably
comprises Sn and Zn such that a ratio of Sn to Zn (Sn/Zn) is 4.0 to
19.0. Where each of "Sn" and "Zn" represents a weight percentage
thereof in the solder. In case that the lead-free solder contains
91 wt. % Sn and 9 wt. % Zn for example, the ratio of Sn/Zn is 10.1
(91/9).
[0019] The lead-free solder of the present invention comprises Sn
and Zn more preferably such that the ratio of Sn to Zn (Sn/Zn) is
4.ltoreq.Sn/Zn<9 and 12<Sn/Zn.ltoreq.19, and contains
substantially no Cu. "Substantially no Cu" means that Cu content is
not greater than Cu content included as impurity in usual raw
material of the solder including raw metals of Sn and Zn.
[0020] The lead-free solder of the present invention may comprise
one or more than two elements among Bi, Si and Sb in the range of
3.2 to 10 wt. %.
[0021] The lead-free solder of the present invention may comprise
0.001 to 1.0 wt. % Si.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a graph showing a relationship between a
temperature at which the solder is kept and an amount of a
deposited compound concerning two solders having a different Ti
content from each other; and,
[0023] FIG. 2 is a graph showing a relationship between a Ti
content and an amount of deposited compound when a solder is kept
at 270.degree. C.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0024] The composition of the lead-free solder of the present
invention is as follows. The content of components will be
represented with a percentage by weight.
[0025] Sn (tin) is not toxic and gives good wetting property
against materials to be joined, and Sn is an indispensable
constituent for the solder. Zn (Zinc) is comprised in the solder in
order to improve adhesion strength thereof to oxide materials such
as glass and ceramics.
[0026] Ti (titanium) is extremely easy to be oxidized, but it bonds
the solder to an oxide material strongly. When Ti content is less
than 0.001 wt. %, the solder does not bond to an oxide material
firmly enough. When Ti content is more than 0.005%, heat cycle
resistance decreases due to increase of hardness of the solder, and
further the solder becomes too hard to use due to a rise of a
melting point thereof. Accordingly, Ti content is preferably 0.001
to 0.005%.
[0027] Al (aluminum) is also extremely easy to be oxidized, and Al
makes the solder to bond to an oxide material firmly. When Al
content is less than 0.001 wt. %, the solder does not bond the
oxide firmly. When Al content is more than 0.005%, heat cycle
resistance of the solder decreases due to increase of hardness of
the solder, the solder has an increased melting point, and the
solder loses workability. Accordingly, Al content is preferably
0.001 to 0.005%.
[0028] Cu (copper) has a good effect on mechanical strength of the
solder. This effect is insufficient when Cu is less than 5.0%. When
Cu is more than 9.0%, the melting point of the solder increases,
the mechanical strength decreases and a lot of Cu--Sn intermetalic
compounds grow. Accordingly, Cu content is preferably 5.0 to 9.0%,
more preferably 0.01 to 3.0%.
[0029] In the lead-free solder of the present invention, the ratio
of Sn to Zn (Sn/Zn), where Sn and Zn are expressed with a
percentage by weight, is preferably 4.0 to 19.0. Sn and Zn make
eutectic reaction in an alloy, and eutectic structures therein
consist of a minute mixture of fine Sn phases and Zn phases. The
eutectic structures have high flexibility, so that stress applied
to the solder is easily dispersed in the eutectic phases. The
stress does not concentrate on the interface of the solder and
oxide material such as glass, so that the solder hardly separates
from the oxide material.
[0030] When the lead-free solder of the present invention has the
Sn/Zn ratio between 9.0 and 12.0 where Sn and Zn are percentages
thereof by weight, the solder preferably contains substantially no
copper. When the solder has the Sn/Zn ratio of 9.0 to 12.0, the
composition of the solder is near or equal to the ratio of the
eutectic composition (Sn/Zn=10.1), and proeutectoids of Sn or Zn
hardly grow large so that the eutectic structure of the solder
becomes fine. A solder containing a lot of eutectic structures has
high flexibility so that it is suitable for soldering glass and the
like as mentioned above. However, grains of the eutectic phases
grow large when the solder contains a lot of seed compounds. Cu and
Zn in the solder tend to react with each other to form CuZn
intermetalic compounds. The compounds work as seeds for of the
proeutectoids, so that the eutectic grains grow large. When the
grains grow large in the solder, the stress applied thereto
concentrates on the grain boundary and causes fracture. Accordingly
the solder is preferable to contain substantially no Cu.
[0031] The lead-free solder of the present invention may contain
one or more elements among Bi, Si and Sb in a range 3.2 to 10%. Bi
and Si improve wettability of the solder. Sb improves an appearance
of the soldered solder and increases creep resistance of the
solder. The solder may contain further another element such as Cr,
Be, Fe, Ni, Co, Ga, Ge and P in a small amount in order to improve
wettability and mechanical strength of the solder.
[0032] When Si is less than 0.001%, above effects are achieved
insufficiently. Si of more than 1.0% raises the melting point of
the solder so that workability of soldering is lowered. Accordingly
Si content is preferably 0.001 to 1.0%, more preferably 0.01 to
0.1%.
[0033] The lead-free solder of the present invention may contain In
(indium). The In decreases the melting point of the solder,
improves wetting property of the solder, and improves flexibility
of the solder, so that the stress applied to the interface of the
soldered solder and oxide material is relaxed.
[0034] The lead-free solder of the present invention directly
solders to not only an oxide such as glass and ceramics but also
metal such as Al, Ti, and Zr which is hard to be soldered due to a
metal oxide film thereon.
[0035] It is preferable to use an ultrasonic equipment which gives
ultrasonic vibration to the solder during soldering in case of
hardsoldering materials. It is also preferable to use an equipment
having a member which transmits a physical stimulus to the
interface of the solder and the hardsoldering material to promote
bonding to each other. The member may have a shape of a plate or a
rod. The member may be rotated or vibrated.
[0036] Hereinafter, the present invention will be described
referring to examples.
EXAMPLES 1 To 24
[0037] A soda-lime glass plate (50.times.50.times.3 mm) was used as
a material to be adhered with lead-free solder. The lead-free
solder has a composition shown in Tables 1, 2 and 3. The solder was
soldered to the glass using an ultrasonic soldering iron having a
tip which vibrates at 60 kHz. The compositions in the tables are
represented with a percentage by weight.
[0038] Adhering property of the solder to the glass was estimated
by knifing the solder on the glass with a knife. In Tables 1, 2 and
3, a circle mark (.largecircle.) of the adhering property shows
that more than half of the solder remains on the glass, and a cross
mark (X) shows that the solder peels off in its entirety.
1TABLE 1 Compositions of the solder (wt %) Example 1 2 3 4 5 6 7 8
9 10 Sn 90.85 89.8 91.5 91.2 92.5 88.6 91.2 92.2 86.5 93.2 Zn 8.99
9.9 8.35 7.6 7.1 11.1 8.39 7.41 12.4 6.2 Ti 0.16 0.2 0.15 1 0.4 0.3
0.08 0.05 0.1 0.15 Al 0 0.1 0 0.2 0 0 0 0 0 0.1 Cu 0 0 0 0 0 0 0.33
0.34 1 0.35 Sum 100 100 100 100 100 100 100 100 100 100 adhering
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. property
[0039]
2TABLE 2 Compositions of the solder (wt %) Example 11 12 13 14 15
16 17 18 19 20 Sn 90.5 80 89.9 95 80.7 70 50 40 90.05 60 Zn 9.0
19.85 9.0 3.7 9.8 29.98 49.99 56.5 9.9 39.99 Ti 0.15 0.03 0.5 1 2
0.007 0.005 1.5 0.05 0.003 Al 0 0.07 0.5 0.1 2.5 0.005 0.002 1.5 0
0.003 Cu 0.35 0.05 0.1 0.2 5 0.008 0.003 0.5 0 0.004 Sum 100 100
100 100 100 100 100 100 100 100 adhering .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. property
[0040]
3TABLE 3 Compositions of the solder (wt %) Example Comparative
Example 21 22 23 24 1 2 3 Sn 75 65 87 45 93.7 89 70 Zn 24.8 32 10.5
49.5 0 0 0 Ti 0.07 0.3 0.7 2.5 3.5 0 0 Al 0.05 0.7 0.3 2 2.8 1 30
Cu 0.08 2 1.5 1 0 10 0 Sum 100 100 100 100 100 100 100 adhering
.largecircle. .largecircle. .largecircle. .largecircle. X X X
property
[0041] As shown from Tables 1, 2 and 3, each of the solder of the
present invention adheres to the glass firmly, since it contains at
least one of Ti, Al, Cu, Sn and Zn. The solder solders glasses each
other firmly, since it has high mechanical strength, and relaxes
the stress applied to the interface between the glass and the
solder during the solder is cooled. The solder of the present
invention does not peel off when impact is applied thereto after it
is soldered.
COMPARATIVE EXAMPLES 1-3
[0042] Table 3 shows compositions and adhesive properties of
comparative examples. The compositions are represented with a
percentage by weight.
[0043] In the comparative examples 1 to 3, contents of Zn and Ti
are out of the scope of the present invention. In the comparative
example 2, a content of Cu is out of the scope of the present
invention. In the comparative example 3, a content of Al is out of
the scope of the present invention. The adhesive property between
the lead-free solder of the comparative examples and the glass is
inferior, so that all the solder separates or peels off completely
from the glass.
EXAMPLES 25-34
[0044] A soda-lime glass plate (50.times.50.times.3 mm) was used as
a material to be soldered. Lead-free solder shown in Table 4 was
used. The solder was soldered to the glass plate using the
ultrasonic soldering iron having the tip which vibrates at 60 kHz.
Compositions shown in Table 4 are represented with a percentage by
weight.
[0045] The adhesive property between the glass and the lead-free
solder was estimated by knifing the solder adhered on the glass in
the same way as in the Examples 1-24. In the adhesive property
shown in Table 4, a circle mark (.largecircle.) shows that more
than half of the solder does not separate but remains on the glass,
and a cross mark (X) shows that the solder separates from the glass
in its entirety.
4TABLE 4 Compositions of the solder (wt %) Example 25 26 27 28 29
30 31 32 33 34 Sn 83 84 86.8 76.8 81.3 90.4 89.99 90.5 90.45 90.49
Zn 9 8.5 8.7 7.7 8.1 9.0 9.0 8.5 9.0 9.0 Ti 0.15 0.05 0.15 0.15
0.15 0.08 0.105 0.15 0.15 0.159 Al 0 0 0 0 0 0 0 0 0 0 Cu 0.35 0.35
0.10 0.30 0.35 0.35 0.35 0.35 0.35 0.35 Sb 3 2 1 5 0 0 0 0 0 0 Si
0.5 0.1 0.2 0 0.05 0.02 0.005 0 0 0 Bi 1 3 2 5 0 0 0 0 0 0 In 3 2 1
5 10 0.1 0.5 0 0 0 Cr 0 0 0.05 0 0 0 0 0 0 0 Be 0 0 0 0.05 0 0 0 0
0 0 Fe 0 0 0 0 0.05 0 0 0 0 0 Ni 0 0 0 0 0 0.05 0 0 0 0 Co 0 0 0 0
0 0 0.05 0 0 0 Ga 0 0 0 0 0 0 0 0.5 0 0 Ge 0 0 0 0 0 0 0 0 0.05 0 P
0 0 0 0 0 0 0 0 0 0.001 Sum 100 100 100 100 100 100 100 100 100 100
adhering .largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. property
[0046] As shown in Table 4, each solder of the examples contains
the components of the invention and components such as Cr, Be, Fe,
Ni, Co, Ga, Ge, and P. The solder solders glasses each other
firmly, since it has high mechanical strength, and relaxes the
stress applied to the interface between the glass and the solder
during the solder is cooled. The solder does not peel off when
impact is applied thereto after it is soldered.
[0047] The inventors have found that a Ti content of the solder has
an influence on the deposition of the (Sn, Zn) Ti series compound
deposited on the bottom of the solder tank.
[0048] The inventors conducted experiments for the Ti content which
prevents deposition of the compound and enables to feed the solder
stably.
[0049] The inventors, at first, fed a Ti containing solder having a
composition of (Sn--Zn eutectic with Ti) into a solder tank, and
melted the solder at a certain temperature to obtain a melt of the
solder. The melt was kept at a predetermined temperature for 10
minutes, and then the melt was flown out of the tank and the
deposition on the bottom of the tank was recovered to measure the
weight thereof. An amount of the deposition (%) was calculated
according to the following equation:
[amount of the deposited compound (%)]
=[amount of the recovered compound (g)/amount of the melt flown out
of
the tank (g)].times.100.
[0050] The results were shown in FIG. 1 wherein two kinds of
solders having different Ti contents were described.
[0051] FIG. 1 shows that the amount of the deposited compound
becomes less as the Ti content decreases.
[0052] The inventors, referring above, conducted experiments for a
Ti content of the solder which can be fed stably at 270.degree. C.
It should be noted that a solder is usually fed at 270.degree. C.
at a usual plant.
[0053] The results were shown in FIG. 2 where a relationship
between the Ti content of the solder and the amount of the compound
deposited therefrom at 270.degree. C., at which the solder was
kept.
[0054] As shown from FIG. 2, the solder having the Ti content of
equal to or less than 0.007 wt. % preferably equal to or less than
0.005 wt. % has the deposition amount of the compound of not more
than 2.4%. The solder of the deposition amount of the compound of
not more than 2.4% can be fed stably without a practical problem at
a usual plant.
[0055] Industrial Capability
[0056] As mentioned above, the lead-free solder of the present
invention does not contain toxic lead, and contains components
according to the invention, and a small amount of Cr, Be, Fe, Ni,
Co, Ga, Ge and P. The solder solders glasses each other firmly,
since it has high mechanical strength, and relaxes the stress
applied to the interface between the glass and the solder during
the solder is cooled. The solder does not peel off when impact is
applied thereto after it is soldered.
* * * * *