U.S. patent application number 10/546824 was filed with the patent office on 2006-07-06 for metal structure and method for production thereof.
Invention is credited to Yoshihiro Hirata, Shinji Inazawa, Kazunori Okada, Teruhisa Sakata, Masao Sakuta, Yoshiaki Tani.
Application Number | 20060144485 10/546824 |
Document ID | / |
Family ID | 33296006 |
Filed Date | 2006-07-06 |
United States Patent
Application |
20060144485 |
Kind Code |
A1 |
Okada; Kazunori ; et
al. |
July 6, 2006 |
Metal structure and method for production thereof
Abstract
A metal structure according to the present invention is unlikely
to become brittle and has excellent hardness and creep resistance,
characterized in that annealing has been applied at a temperature
not more than the temperature at which crystals of the metal
material start to become larger. This metal structure includes at
least two kinds of metal material, and annealing can be applied at
a temperature not more than the temperature at which crystals of
the metal material start to become larger. For example, the present
invention is advantageous in the manner of a microstructure for a
contact probe. A fabricating method according to the present
invention is a method of fabricating a metal structure unlikely to
become brittle and having excellent hardness and creep resistance,
characterized in that the step of applying annealing at at a
temperature not more than the temperature at which crystals of the
metal material start to become larger is included.
Inventors: |
Okada; Kazunori; (Hyogo,
JP) ; Hirata; Yoshihiro; (Hyogo, JP) ;
Inazawa; Shinji; (Osaka, JP) ; Sakuta; Masao;
(Hyogo, JP) ; Tani; Yoshiaki; (Hyogo, JP) ;
Sakata; Teruhisa; (Hyogo, JP) |
Correspondence
Address: |
MCDERMOTT WILL & EMERY LLP
600 13TH STREET, N.W.
WASHINGTON
DC
20005-3096
US
|
Family ID: |
33296006 |
Appl. No.: |
10/546824 |
Filed: |
April 12, 2004 |
PCT Filed: |
April 12, 2004 |
PCT NO: |
PCT/JP04/05228 |
371 Date: |
August 24, 2005 |
Current U.S.
Class: |
148/675 ;
148/400; 148/426 |
Current CPC
Class: |
G01R 1/06755 20130101;
G01R 1/0675 20130101; C22F 1/10 20130101; G01R 1/06733
20130101 |
Class at
Publication: |
148/675 ;
148/400; 148/426 |
International
Class: |
C22C 19/03 20060101
C22C019/03; C22F 1/10 20060101 C22F001/10 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 16, 2003 |
JP |
2003-111710 |
Claims
1. A metal structure unlikely to become brittle and having
excellent hardness and creep resistance, wherein annealing has been
applied at a temperature not more than a temperature at which
crystals of a metal material start to become larger.
2. The metal structure according to claim 1, wherein said metal
structure is formed of at least two kinds of metal material, and
annealing has been applied at a temperature not more than the
temperature at which crystals of the metal material start to become
larger.
3. The metal structure according to claim 1, wherein said metal
structure is a microstructure.
4. The metal structure according to claim 1, wherein said metal
structure is a contact probe.
5. A method of fabricating a metal structure unlikely to become
brittle and having excellent hardness and creep resistance, wherein
the method comprises the step of applying annealing at at a
temperature not more than a temperature at which crystals of a
metal material start to become larger.
Description
TECHNICAL FIELD
[0001] The present invention relates to a method of modifying a
metal structure, and more particularly, to a method of annealing
for fabricating a metal structure unlikely to become brittle and
having excellent hardness and creep resistance.
BACKGROUND ART
[0002] Annealing is a process to heat a metal structure and the
like, hold it at a temperature and then cool the same to lower
temperature. It is a heat treatment intended for improvement of
plastic working properties, removal of residual internal stress,
adjustment of crystal grain and the like. For annealing a metal
structure formed of nickel (Ni), the structure is generally heated
to around 700-900.degree. C. and held for 1-2 hours, and then
cooled down slowly. With this heat treatment, since nickel (Ni) is
recrystallized, nanocrystal material of a crystal size of around 10
nm, or amorphous material of a further smaller crystal size, will
have a larger crystal size of several .mu.m --a several ten .mu.m.
The relatively unordered initial structure is reconfigured by
annealing, to arrive at a more stable state of equilibrium, and is
essentially removed of all residual internal stress.
[0003] As an improved annealing method, Japanese Patent National
Publication No. 2001-516812 discloses a method of heat treatment to
obtain stable machinability under load. In this method, a wire
coated with metal such as nickel (Ni) and cobalt (Co) using
saccharine and 2-butyne-1,4-diol and the like is relatively mildly
heat-treated to fabricate an elastic metal structure.
[0004] For a heat treatment temperature of this method, effective
is a temperature 0-150.degree. C. higher than the transformation
temperature at which crystals of a metal material on the wire
become larger. For example, for a wire coated with a metal material
including nickel (Ni) and cobalt (Co), the effective temperature
for heat treatment is 266-416.degree. C. since the transformation
temperature of the metal material is 266.degree. C. (refer to FIG.
6). Therefore, in this method, the structure is heat treated at a
temperature lower than the normal annealing temperature for nickel
(Ni) of 700-900.degree. C.
[0005] For a metal structure including nickel (Ni) and cobalt (Co),
when annealing is applied at 330.degree. C. for 10 minutes,
nanocrystal material or amorphous material having an average grain
diameter of 16 nm will have larger crystals to become crystal
material with an average grain diameter of 78 nm. Consequently, due
to annealing, yield strength, elastic modulus and temperature
stability of the metal structure are modified.
[0006] As the semiconductor technology advances, importance of a
contact probe, which is necessary to test a circuit formed on a
semiconductor substrate or the like, increases. Since the contact
probe is pressed against a circuit of a semiconductor substrate or
the like for usage, it has a spring capability to increase the
reliability of connection with the circuit as well as not to damage
the circuit. Therefore, the contact probe is required to have the
property of being unlikely to become brittle and damaged while
having high hardness. Further, since the contact probe is
repeatedly used, it is required to have a property to return to its
original shape when load is removed after the test. Thus, it is
required for the contact probe that the amount remaining as
deformation after load is removed (hereinafter referred to as
"creep amount") is small, and that spring load which occurs when
the spring achieves a predetermined stroke does not change with
loading time. Therefore, it is necessary to use a metal structure
having superior creep resistance. More specifically, it is required
to maintain creep resistance even when a semiconductor substrate to
be tested is at a temperature of around 50-125.degree. C. or
higher.
DISCLOSURE OF THE INVENTION
[0007] When annealing is applied on a metal structure, excellent
quality modifying effects are achieved such as reduction of
residual internal stress, increase of hardness and the like.
However, depending on conditions of annealing, the metal structure
becomes more brittle and has reduced hardness, so that it is more
likely to break. One object of the present invention is to provide
a method of annealing to fabricate a metal structure unlikely to
become brittle and having excellent creep resistance while
maintaining hardness.
[0008] To achieve the object, a metal structure according to the
present invention is a metal structure unlikely to become brittle
and having excellent hardness and creep resistance, characterized
in that annealing has been applied at a temperature not more than
the temperature at which crystals of the metal material start to
become larger. This metal structure is formed of at least two kinds
of metal material, and annealing can be applied at a temperature
not more than the temperature at which crystals of the metal
material start to become larger. For example, the present invention
is more advantageous in the manner of a microstructure for a
contact probe or the like. A method of fabricating a metal
structure according to the present invention is a method of
fabricating a metal structure unlikely to become brittle and having
excellent hardness and creep resistance, characterized in that a
step of applying annealing at a temperature not more than the
temperature at which crystals of the metal material start to become
larger is included.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 shows a perspective view of a contact probe according
to the present invention.
[0010] FIGS. 2A-2D show steps in a method of fabricating a contact
probe according to the present invention.
[0011] FIG. 3 shows a plan view of a mask having a pattern of a
contact probe.
[0012] FIGS. 4 and 5 show a deformation amount of a contact probe
over time.
[0013] FIG. 6 shows the relationship between annealing temperature
and metal crystal size.
BEST MODES FOR CARRYING OUT THE INVENTION
[0014] (Method of Producing a Metal Structure)
[0015] The method of fabricating a metal structure according to the
present invention is characterized in that a step of applying
annealing at a temperature not more than the temperature at which
crystals of the metal material start to become larger is included.
Methods to increase creep resistance of the metal material include
a method to reduce residual internal stress within crystals and a
method to enlarge the crystal grain size. When heat treatment is
applied at a temperature higher than the temperature at which
crystals of the metal material increases, residual internal stress
within crystals reduces, but crystals become larger at the same
time. Consequently, although creep resistance of the metal material
increases, decrease in hardness or embrittlement of the metal
material tends to occur due to larger crystals. On the other hand,
according to the producing method of the present invention which
applies annealing at a temperature not more than the temperature at
which crystals of the metal material start to become larger, creep
resistance increases due to reduction of residual internal stress
within crystals while hardness of the metal material is maintained
and embrittlement is small because crystals do not enlarge.
[0016] Annealing is applied at a temperature not more than the
temperature at which crystals of the metal material start to become
larger. At a temperature higher than this temperature, decrease in
hardness or embrittlement of the metal material is likely to occur.
More specifically, if the metal structure includes nickel-manganese
(Ni--Mn) alloy, annealing is applied at a temperature not more than
260.degree. C. since the temperature at which crystals start to
become larger is 260.degree. C. In this case, since the range of
250-260.degree. C. is a transitional region where some of the
crystals start to become larger, the annealing temperature is
preferably 150-250.degree. C., and more preferably 200-230.degree.
C. When the annealing temperature is lower than 150.degree. C., it
is difficult to sufficiently reduce the residual stress within
crystals. On the other hand, when the annealing temperature is
higher than 250.degree. C., it is possible to reduce internal
stress of crystals and increase creep resistance, but decrease in
hardness or embrittlement tends to occur.
[0017] Although the annealing period of time varies depending on
the metal material and annealing temperatures, in general, when
annealing is applied at a lower temperature, embrittlement of
crystals is depressed and longer annealing time is preferable to
reduce residual stress within crystals sufficiently and to prevent
crystals from enlarging. Meanwhile, when annealing is applied at a
higher temperature, shorter annealing time is preferable to depress
enlargement of crystals since it is possible to efficiently reduce
residual stress within crystals. For example, when the metal
structure is formed of nickel-manganese (Ni--Mn) alloy and the
annealing temperature is 150.degree. C., annealing of 10-30 hours
is preferable. When the annealing temperature is 250.degree. C.,
annealing of 0.5-2 hours is preferable.
[0018] In the present invention, the metal material to be subjected
to annealing is preferably at least one material selected from the
group consisting of nickel (Ni), cobalt (Co), iron (Fe), rhodium
(Rh), palladium (Pd), tungsten (W), copper (Cu), manganese (Mn),
chromium (Cr), titanium (Ti), aluminum (Al), gold (Au) and platinum
(Pt). Among these, nickel (Ni), cobalt (Co) or iron (Fe) are more
preferable. With regards to alloys, nickel-cobalt (Ni--Co),
cobalt-manganese (Co--Mn), nickel-manganese (Ni--Mn), nickel-iron
(Ni--Fe), cobalt-iron (Co--Fe), titanium-tungsten (Ti--W) or
nickel-cobalt-manganese (Ni--Co--Mn) are more preferable.
[0019] (Metal Structure)
[0020] The metal structure according to the present invention is
characterized in that annealing has been at a temperature not more
than the temperature at which crystals of the metal material start
to become larger. The metal structure according to the present
invention includes at least two kinds of metal material, and
annealing can be applied at a temperature not more than the
temperature at which crystals of the metal material start to become
larger. These metal structures are unlikely to cause decrease in
hardness and embrittlement, and have excellent creep resistance.
Coating with the metal material can be effected by any of commonly
known methods such as electroplating, chemical vapor deposition
(CVD), physical vapor deposition (PVD), or electrolytic plating or
electroless plating of metal. For example, for physical vapor
deposition, vacuum deposition, sputtering or ion plating can be
used, and a metal material layer with a thickness of 250-600 nm can
be formed by sputtering.
[0021] The present invention is more effective for a
microstructure. The present invention is also effective for a metal
structure which is not a microstructure. However, the effect of
making the material itself homogeneous by preventing crystals from
enlarging according to the invention is outstanding for a
microstructure with a minimum machinable dimension of several
.mu.m--several hundred .mu.m. Therefore, the metal structure
according to the present invention can be preferably used as a
contact probe, since the contact probe needs to have a
microstructure of several .mu.m--several hundred .mu.m in its
spring portion and the like, and it is necessary to use a material
unlikely to become brittle and having excellent hardness and creep
resistance.
[0022] An example of the contact probe is shown in FIG. 1. The
contact probe includes a plunger portion 1 in contact with a
circuit to be tested, a spring portion 2 supporting plunger portion
1 at one end, and a lead line connection portion 3 electrically
connecting the other end of spring portion 2 to the lead line. The
contact probe is arranged within a probe card. When test is
conducted, the contact probe is used with plunger portion 1 pressed
against a circuit to be tested.
[0023] An example of the method of fabricating a contact probe is
shown in FIG. 2. As shown in FIG. 2A, a resist layer 22 is formed
on a surface of a conductive substrate 21. For a substrate, a
conductive substrate of SUS, Cu or Al can be used. Also, a
non-conductive substrate can be used which includes Si or glass and
the like and has a conductive layer formed thereon of Ti, Al, Cu or
alloys thereof by sputtering and the like.
[0024] Then, using a mask 23 having a pattern of a desired contact
probe, UV or X-ray 24 is directed. Subsequently, an exposed region
22a of resist layer 22 is removed by development, and a resin mold
22b as shown in FIG. 2B is obtained. After resin mold 22b is
formed, as shown in FIG. 2C, a metal layer 25 is formed on resin
mold 22b. Metal layer 25 can be formed by electroforming.
Electroforming means to form a metal layer including nickel (Ni)
and the like on a conductive substrate using a metal solution.
[0025] After achieving a desired thickness by polishing or
grinding, resin mold 22b on substrate 21 is removed by ashing with
oxygen plasma and the like, followed by removal of substrate 21 by
dry etching and the like. Finally, annealing is applied at a
temperature not more than the temperature at which crystals of the
metal material start to become larger to obtain a contact probe
according to the present invention as shown in FIG. 2D. With this
method, a contact probe unlikely to become brittle and having
excellent hardness and creep resistance can be fabricated. In
addition, a contact probe with its plunger portion, spring portion
and lead line connection portion integrated can be easily
fabricated, adaptable to micro miniaturization or complexation of
the contact probe. Furthermore, assembling work is eliminated.
EXAMPLE 1
[0026] As shown in FIG. 2A, X-ray resist layer 22 was formed on a
surface of SUS substrate 21. Then, exposed to X-ray 24 through mask
23 having a pattern of the contact probe, the pattern was
transformed to X-ray resist layer 22. The mask corresponding to the
pattern of the contact probe had a shape as shown in FIG. 3, with L
of 1550 .mu.m, W of 1000 .mu.m, T.sub.1 of 82 .mu.m and T.sub.2 of
65 .mu.m. Exposed region 22a of resist layer 22 was removed by
development to obtain resin mold 22b as shown in FIG. 2B. Then, as
shown in FIG. 2C, metal layer 25 of nickel-manganese alloy was
formed on resin mold 22b. Formation of metal layer 25 was performed
by electroforming. For electroforming, a plating bath having nickel
sulfamate solution blended with manganese sulfamate, boric acid,
saccharine sodium, 2-butyne-1,4-diol and sodium lauryl sulfate was
used.
[0027] After electroforming, polishing to a thickness of 60 .mu.m,
resin mold 22b was removed by ashing, and substrate 21 was
separated to obtain a contact probe as shown in FIG. 2D. When the
metal crystal size of the contact probe obtained was measured, it
was about 13 nm. Annealing was applied by heating this contact
probe within a constant temperature bath held at 200.degree. C. for
1 hour and cooling it down naturally at room temperature. When
metal crystal size of the contact probe after annealing was
measured, it maintained 13 nm.
[0028] Creep resistance of the contact probe was evaluated by a
micro load test machine (H-100 produced by Fischer). Evaluation of
creep resistance was performed by measuring the deformation amount
when the contact probe was subjected to a constant load of 50 mN
for 1 hour (3600 seconds) at 85.degree. C. The result is shown in
FIG. 4.
[0029] Based on the result in FIG. 4, delayed deformation amount
was determined by an equation as follows: Delayed deformation
amount (.mu.m)=deformation amount after 1 hour-initial deformation
amount
[0030] As clearly shown from the measurement result, the
deformation amount of the contact probe not subjected to annealing
gradually increased over time, and after 1 hour of loading, it
reached 45 .mu.m. In contrast, in the contact probe subjected to
annealing at 200.degree. C. for 1 hour, the initial deformation
amount was comparable, but the delayed deformation amount after 1
hour of loading was about 2 .mu.m. Therefore, it was found that the
contact probe subjected to annealing according to the present
invention did not have enlargement of crystals and showed higher
creep resistance than the contact probe not subjected to
annealing.
EXAMPLE 2
[0031] In the present example, for the contact probe produced in
Example 1 and before annealing, annealing time was fixed to 1 hour,
and annealing was applied at various temperatures of 150.degree.
C., 200.degree. C., 230.degree. C., 250.degree. C. and 300 .degree.
C. Then creep resistance was measured respectively. Evaluation
method of creep resistance was the same as in Example 1, and
deformation amount after the contact probe was subjected to a
constant load of 50 mN for 1 hour (3600 seconds) at 85.degree. C.,
was measured. The result is shown in FIG. 5.
[0032] In the present example, deformation amount (108-132 .mu.m)
.+-.10% of the initial deformation amount (120 .mu.m) of the
contact probe not subjected to annealing was evaluated as the
tolerable range for a product. As clearly shown from the result in
FIG. 5, the contact probe subjected to annealing at 150-250.degree.
C. for 1 hour was within that tolerable range. Particularly, the
contact probe subjected to annealing at the range of
200-230.degree. C. for 1 hour exhibited extremely superior creep
resistance. When the annealing temperature was 300.degree. C.,
although creep resistance was apparently good, the initial
deformation amount decreased considerably, and the metal became
hard and brittle. Therefore, the contact probe unpreferably often
broke when installed or used repeatedly.
EXAMPLE 3
[0033] In the present example, for the contact probe produced in
Example 1 and before annealing, annealing was applied at
temperatures of 150.degree. C., 200.degree. C., 250.degree. C.,
260.degree. C. and 300.degree. C., and the metal crystal size was
measured. The result is shown in FIG. 6. As clearly shown from the
result in FIG. 6, with annealing at 250.degree. C., crystals
slightly began to grow, and at 260.degree. C., the crystal size
became about ten times larger. At 300.degree. C., crystal size
reached about 600 nm, showing that crystals completely enlarged.
Therefore, it was found that the temperature at which crystals
enlarge was 260.degree. C., and also taking into account the result
of Example 2, the annealing temperature to effectively exhibit the
effects of the present invention was a temperature at which
crystals of the metal material start to enlarge, or lower.
[0034] It should be understood that the embodiments and examples
disclosed herein are illustrative and non-restrictive in every
respect. The scope of the present invention is defined by the terms
of the claims, rather than the description above, and is intended
to include any modifications within the scope and meaning
equivalent to the terms of the claims.
INDUSTRIAL APPLICABILITY
[0035] According to the method of annealing of the present
invention, a metal structure unlikely to become brittle and having
good creep resistance can be fabricated while maintaining
hardness.
* * * * *