U.S. patent application number 09/246743 was filed with the patent office on 2001-09-13 for magnetic head.
Invention is credited to SATOH, HIDEZI.
Application Number | 20010021085 09/246743 |
Document ID | / |
Family ID | 12416268 |
Filed Date | 2001-09-13 |
United States Patent
Application |
20010021085 |
Kind Code |
A1 |
SATOH, HIDEZI |
September 13, 2001 |
MAGNETIC HEAD
Abstract
A magnetic head includes a slider having any one of recording
and reproducing elements, and a flexure having an elastically
deformative tongue. The slider and the flexure are bonded together
with a resin adhesive therebetween. The resin adhesive has a
Young's modulus E in a range of 700 to 5,200 kg/cm.sup.2 at
25.degree. C. and a bond strength of 50 gf or more.
Inventors: |
SATOH, HIDEZI; (NIIGATA-KEN,
JP) |
Correspondence
Address: |
BRINKS HOFER GILSON & LIONE
P.O. BOX 10395
CHICAGO
IL
60610
US
|
Family ID: |
12416268 |
Appl. No.: |
09/246743 |
Filed: |
February 8, 1999 |
Current U.S.
Class: |
360/234.6 ;
G9B/5.151 |
Current CPC
Class: |
G11B 5/4826
20130101 |
Class at
Publication: |
360/234.6 |
International
Class: |
G11B 005/60; G11B
021/21 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 17, 1998 |
JP |
10-034510 |
Claims
What is claimed is:
1. A magnetic head comprising: a slider having any one of recording
and reproducing elements; and a flexure having an elastically
deformative tongue, said slider and said flexure being bonded
together with a resin adhesive therebetween, wherein, said resin
adhesive has a Young's modulus E in a range of 700 to 5,200
kg/cm.sup.2 at 25.degree. C. and a bond strength of 50 gf or
more.
2. A magnetic head according to claim 1, wherein said resin
adhesive has a glass transition temperature Tg in a range of 4 to
70.degree. C.
3. A magnetic head according to claim 1, wherein, at an operating
temperature T of 25.degree. C., said resin adhesive has a product
{E.multidot.(Tg-25.degree. C.)} obtained by multiplying the Young's
modulus E at 25.degree. C. by the difference when 25.degree. C. is
subtracted from the glass transition temperature Tg of said resin
adhesive in a range of 7,000 to 234,000
kg.multidot..degree.C./cm.sup.2.
4. A magnetic head according to claim 2, wherein, at an operating
temperature T of 25.degree. C., said resin adhesive has a product
.DELTA.E.multidot.(Tg-25.degree. C.)} obtained by multiplying the
Young's modulus E at 25.degree. C. by the difference when
25.degree. C. is subtracted from the glass transition temperature
Tg of said resin adhesive in a range of 7,000 to 234,000
kg.multidot..degree.C./cm.sup.2.
5. A magnetic head according to claim 1, wherein a conductive resin
film is formed between an end of said slider and said flexure as a
countermeasure against static electricity, and said conductive
resin film has the same properties as those of said resin
adhesive.
6. A magnetic head according to claim 2, wherein a conductive resin
film is formed between an end of said slider and said flexure as a
countermeasure against static electricity, and said conductive
resin film has the same properties as those of said resin
adhesive.
7. A magnetic head according to claim 3, wherein a conductive resin
film is formed between an end of said slider and said flexure as a
countermeasure against static electricity, and said conductive
resin film has the same properties as those of said resin
adhesive.
8. A magnetic head according to claim 4, wherein a conductive resin
film is formed between an end of said slider and said flexure as a
countermeasure against static electricity, and said conductive
resin film has the same properties as those of said resin adhesive.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a floating type magnetic
head device for use in a hard disk apparatus or the like. In
particular, the invention relates to a magnetic head in which a
slider and a flexure for supporting the slider are bonded together
with an adhesive.
[0003] 2. Description of the Related Art
[0004] FIG. 3 is a partial side view of a known magnetic head
device for use in a hard disk apparatus.
[0005] The magnetic head device includes a slider 1 and a support 2
for supporting the slider 1.
[0006] The slider 1 is composed of a ceramic material or the like.
A thin-film element 4 is provided on the trailing end B, and the
thin-film element 4 includes an MR head (read head) for reading
magnetic signals by detecting a leakage magnetic field from a
recording medium such as a hard disk, using a magnetoresistance
effect, and an inductive head (write head) in which a coil and so
on are formed by patterning.
[0007] The support 2 includes a load beam 5 and a flexure 6.
[0008] The load beam 5 is composed of a leaf spring material such
as stainless steel, and has a bent section 5a having rigidity on
each side of the front portion. A predetermined elastic force can
be displayed at the base end of the load beam 5 in which the bent
section 5a is not formed.
[0009] A spherical pivot 7 which protrudes downward in the drawing
is formed in the front portion of the load beam 5, and the slider 1
abuts against the pivot 7 with the flexure 6 therebetween.
[0010] The flexure 6 is composed of a leaf spring such as stainless
steel. The flexure 6 includes a fixed section 6a and a tongue 6b,
and a step 6c connects the fixed section 6a to the tongue 6b.
[0011] As shown in FIG. 3, to the lower surface of the tongue 6b,
the slider 1 is bonded with a resin adhesive 20. An example of the
resin adhesive 20 is a thermosetting epoxy resin adhesive.
[0012] A conductive pattern (not shown in the drawing) is provided
on the reverse side of the tongue 6b, and an electrode terminal
section (not shown in the drawing) formed of a thin film extracted
from the thin-film element 4 is provided on the trailing end B of
the slider 1. At the junction between the conductive pattern and
the electrode terminal section, a joint 9 is formed by ball bonding
using gold (Au) or the like. The joint 9 is covered with a
reinforcing resin film 10 for protection.
[0013] A fillet conductive resin film 21 is formed between the
leading end A of the slider 1 and the tongue 6b. The conductive
resin film 21 is provided to secure electrical connection between
the slider 1 and the flexure 6 and to dissipate static electricity
to the support 2.
[0014] The upper surface of the tongue 6b abuts against the pivot 7
formed on the load beam 5, and the slider 1 bonded to the lower
surface of the tongue 6b can change the attitude freely, by means
of elasticity of the tongue 6b, with the apex of the pivot 7
serving as a fulcrum.
[0015] The slider 1 of the magnetic head device is applied force
with the elastic force of the base end of the load beam 5 in the
direction of the disk D. The magnetic head device is used for a
so-called "CSS" (Contact Start Stop) type hard disk apparatus or
the like, and when the disk D stops, an air bearing surface (flying
surface) la comes into contact with the recording surface of the
disk D. When the disk D starts, an airflow occurs between the
slider 1 and the surface of the disk D along the disk movement, and
the slider 1 is lifted by a short spacing .delta.2 from the surface
of the disk D because of a lifting force caused by the airflow.
[0016] When the slider 1 is lifted, as shown in FIG. 3, the leading
end A of the slider 1 is lifted higher above the disk D than the
trailing end B. While maintaining the lifting attitude, magnetic
signals from the disk are detected by the MR head of the thin-film
element 4, or the magnetic signals are written by the inductive
head.
[0017] In the conventional magnetic head device, however, the
flatness or crown height of the air bearing surface la of the
slider 1 may easily change, resulting in extreme difficulty in
setting the spacing .delta.2 at a given amount.
[0018] The flatness or crown height of the air bearing surface 1a
of the slider 1 easily changes because a rigid adhesive such as a
thermosetting epoxy resin adhesive is conventionally used as the
resin adhesive 20 for bonding the upper surface of the slider 1 and
the lower surface of the tongue 6b of the flexure 6 together.
[0019] As shown in FIG. 3, the trailing end B of the slider 1 is
rigidly bonded to the tongue 6b of the flexure 6 by the joint 9
formed by ball bonding.
[0020] Additionally, since the slider 1 has a coefficient of
thermal expansion which is different from that of the flexure 6, if
the resin adhesive 20 bonding the upper surface of the slider 1 and
the lower surface of the tongue 6b together is rigid, thermal
stress owing to the difference in coefficient of thermal expansion
between the tongue 6 and the slider 1 may affect the slider 1 with
the resin adhesive 20 therebetween, resulting in adhesive
deformation with respect to the slider 1.
[0021] Generally, since the flexure 6 has a larger coefficient of
thermal expansion in comparison with the slider 1, for example, in
the low temperature region, the air bearing surface 1a of the
slider 1 is deformed to be convex in relation to the disk D, and
thus a spacing loss increases, resulting in a decrease in
output.
[0022] In the high temperature region, the air bearing surface 1a
of the slider 1 is deformed to be concave in relation to the disk
D, and thus it is highly possible that the trailing end B of the
slider 1 collides with the surface of the disk D, and the minimum
flying height (spacing amount) cannot be guaranteed.
[0023] Also, as shown in FIG. 3, when the conductive resin film 21
is provided between the leading end A of the slider 1 and the
tongue 6b of the flexure 6, if the conductive resin film 21 is
rigid the same as the resin adhesive 20, both the trailing end B
and the leading end A of the slider 1 are rigidly bonded, resulting
in larger adhesive deformation with respect to the slider 1 owing
to thermal stress.
SUMMARY OF THE INVENTION
[0024] The present invention has been achieved in order to overcome
the difficulties noted above with respect to the conventional art.
It is an object of the present invention to provide a magnetic head
which can reduce adhesive deformation with respect to a slider by
using a resin adhesive which is flexible particularly after curing
in order to bond the slider and a flexure together.
[0025] In accordance with the present invention, a magnetic head
includes a slider having an element for recording and/or
reproducing and a flexure having an elastically deformative tongue.
The slider and the flexure are bonded together with a resin
adhesive therebetween. The resin adhesive has a Young's modulus E
in the range of 700 to 5,200 kg/cm.sup.2 at 25.degree. C. and a
bond strength of 50 gf or more.
[0026] Preferably, the resin adhesive has a glass transition
temperature in the range of 4 to 70.degree. C.
[0027] Also, preferably, the resin adhesive has a product
{E.multidot.(Tg-25.degree. C.)} obtained by multiplying the Young's
modulus E at 25.degree. C. by the temperature obtained by
subtracting 25.degree. C. from the glass transition temperature Tg
in the range of 7,000 to 234,000
kg.multidot..degree.C./cm.sup.2.
[0028] Also, when a conductive resin film is formed between an end
of the slider and the flexure as a countermeasure against static
electricity, the conductive resin film used has the same properties
as those of the resin adhesive described above.
[0029] Although, in conventional art, wiring is directly connected
to a slider in order to output signals from a thin-film element
provided on the slider or to input signals to the thin-film
element, as the slider is miniaturized, use of a magnetic head, in
which a conductive pattern is formed on a flexure for bonding the
slider and the conductive pattern and a conductive terminal section
provided on the slider are bonded together with a ball bonding
technique, has been implemented.
[0030] However, since one end (trailing end) of the slider is
rigidly bonded to the flexure with a gold bump by ball bonding, if
a resin adhesive used for connecting the slider and the flexure is
rigid, adhesive deformation may easily occur in which the flatness
or crown height of the air bearing surface (flying surface) changes
after bonding.
[0031] Therefore, a flexible resin adhesive which can absorb strain
owing to the difference in coefficient of thermal expansion between
the slider and the flexure and which can decrease internal stress
resulting from curing shrinkage is required as the resin adhesive
used for bonding the slider and the flexure.
[0032] For example, the resin adhesive may contain a thermoplastic
resin such as an acrylic resin, a polyurethane resin, a polyester
resin, or a nylon resin as a major constituent, or may contain a
thermosetting resin if it has elasticity in the operating
temperature region.
[0033] The factors that determine flexibility of a resin adhesive
(after curing) are the Young's modulus E and the glass transition
temperature Tg of the resin adhesive.
[0034] When the glass transition temperature Tg of the resin
adhesive is higher than the operating temperature T and the resin
adhesive is assumed to be an elastic body (having a Young's modulus
E), a thermal stress .delta. caused by the resin adhesive to the
slider (and the flexure) is represented by the following equation
1:
.delta.=E.multidot..epsilon.=.intg.E(T).multidot..DELTA..alpha..multidot.(-
Tg-T)dT Equation 1
[0035] (wherein Tg>T)
[0036] where .epsilon. is a strain between the slider and the
flexure, and .DELTA..alpha. is a difference in coefficient of
thermal expansion between the slider and the flexure.
[0037] In reality, since the resin adhesive (after curing) is a
viscoelastic body, a portion of the strain .epsilon. between the
slider and the flexure is absorbed (buffered) by viscous
deformation and does not contribute to adhesive deformation.
[0038] The adhesive deformation of the slider is considered to have
a positive linear relationship with thermal stress .delta..
Therefore, at an operating temperature T, as the Young's modulus E
of the resin adhesive increases and as the glass transition
temperature Tg increases, thermal stress .delta. increases and
adhesive deformation increases.
[0039] When the glass transition temperature Tg of the resin
adhesive is lower than the operating temperature T, the Young's
modulus of the adhesive decreases, and the resin adhesive has
rubber elasticity. Therefore, even if a strain .epsilon. occurs
between the slider and the flexure, the strain .epsilon. is
absorbed by deformation of the adhesive, and thus, thermal stress
.delta. that causes adhesive deformation does not show great
effects between the slider and the flexure.
[0040] The present inventors measured adhesive deformation of the
slider using a plurality of resin adhesives having different
properties for bonding the slider and the flexure together.
[0041] In experimentation, resin adhesive sample Nos. 1 through 10
shown in Table 1 were applied to joining surfaces of the slider and
the flexure, and the resin adhesives were cured at 120.degree. C.
to bond the slider and the flexure together.
[0042] Also, a gold bump was formed between the trailing end of the
slider and the flexure, and in order to protect the bump, the bump
was covered with a resin film.
[0043] The Young's modulus E of the resin adhesive was measured at
25.degree. C. in accordance with a tensile test method
(stress/displacement curve). The glass transition temperature Tg of
the resin adhesive was measured in accordance with a thermal
mechanical analysis (TMA), and the adhesive deformation of the
slider was measured by a WYCO flatness meter. Bond strength was
measured by a peel test in which, using a slider and a flexure
bonded to each other with a resin adhesive, the flexure was pulled
perpendicular to the bond plane between the slider and the
flexure.
1 TABLE 1 Young's Glass modulus E transition Adhesive deformation
Bond strength (25.degree. C.) temperature (Crown height) (nm) (gf)
Sample No. Adhesive (kg/cm.sup.2) Tg (.degree. C.) 5.degree. C.
25.degree. C. 50.degree. C. 25.degree. C. 50.degree. C. 1 Epoxy
5,000 34 2.0 0.4 0.1 87 80 2 Epoxy 13,500 132 28.0 27.4 21.0 51 88
3 Adhesive 400 28 1.5 0.4 0.1 30 10 4 Adhesive 700 35 1.1 0.4 0.1
75 60 5 Adhesive 1,000 4 1.7 0.7 0.1 70 55 6 Adhesive 3,000 69 1.8
1.3 0.5 71 70 7 Adhesive 3,500 20 1.7 0.8 0.2 80 62 8 Adhesive
5,200 70 3.0 2.0 0.7 81 79 9 Adhesive 7,400 78 13.5 9.8 6.5 58 70
10 Cyanoacrylate 14,800 130 23.1 22.8 17.4 75 98
[0044] A positive adhesive deformation shown in Table 1 indicates
that the air bearing surface (flying surface) of the slider
protrudes in the direction of a disk, and a distance between the
peak of the protrusion and the air bearing surface before
deformation is defined as the adhesive deformation.
[0045] As shown in Table 1, sample Nos. 2, 9, and 10 have a
significantly higher adhesive deformation at 5.degree. C.,
25.degree. C., and 50.degree. C. in comparison with other
samples.
[0046] With respect to sample Nos. 2, 9, and 10, the Young's
modulus E of the resin adhesive at 25.degree. C. and the glass
transition temperature Tg are significantly higher in comparison
with other samples.
[0047] Therefore, the thermal stress 6 that affects the slider
increases (refer to equation 1), resulting in a significantly high
adhesive deformation.
[0048] In order to improve the reliability of the flying height
(spacing), the variation in the flying height in response to
temperature must be suppressed within .+-.3 nm. Therefore, the
adhesive deformation of the slider at each of 5.degree. C.,
25.degree. C., and 50.degree. C. also must be suppressed within
.+-.3 nm, and a difference between the adhesive deformation of the
slider at an operating temperature of 5.degree. C. and the adhesive
deformation of the slider at an operating temperature of 50.degree.
C. also must be suppressed within .+-.3 nm.
[0049] Sample Nos. 1, 3, 4, 5, 6, 7, and 8 in table 1 satisfy the
above-mentioned conditions.
[0050] Therefore, in view of the adhesive deformation of the
slider, preferably, the resin adhesive has a Young's modulus at
25.degree. C. of 700 to 5,200 kg/cm.sup.2 and a glass transition
temperature Tg of 4 to 70.degree. C.
[0051] In sample No. 3, although the adhesive deformation is
suppressed to 3 nm or less, the bond strength (peel strength) is 50
gf or less which is lower in comparison with other samples.
[0052] In sample No. 5, although the glass transition temperature
of 4.degree. C. is significantly low, the bond strength (peel
strength) is 50 gf or more.
[0053] That is, the major factor which determines the bond strength
presumably lies in the Young's modulus E rather than the glass
transition temperature Tg.
[0054] In detail, at an operating temperature of 25.degree. C.,
with respect to sample No. 5, although the resin adhesive is
considered to have significantly low elasticity since the glass
transition temperature is 4.degree. C., the actual resin adhesive
in sample No. 5 functions as a viscoelastic body and the bond
strength does not greatly decrease since the resin adhesive has a
significantly high Young's modulus E of 1,000 kg/cm.sup.2 at
25.degree. C.
[0055] On the contrary, with respect to sample No. 3, at an
operating temperature of 25.degree. C., although the resin adhesive
is considered to function as a viscoelastic body and have
relatively high bond strength since the glass transition
temperature is 28.degree. C., the actual resin adhesive in sample
No. 3 has low bond strength since the resin adhesive has a
significantly low Young's modulus E of 400 kg/cm.sup.2 at
25.degree. C.
[0056] Accordingly, in table 1, preferable samples are Nos. 1, 4,
5, 6, 7, and 8.
[0057] These samples have a Young's modulus E at 25.degree. C. in
the range of 700 to 5,200 kg/cm.sup.2 and a bond strength of 50 gf
or more, which are conditions of preferred resin adhesives in the
present invention.
[0058] Also, in accordance with the present invention, the glass
transition temperature Tg of the resin adhesive preferably ranges
from 4 to 70.degree. C.
[0059] Next, at an operating temperature T of 25.degree. C., a
value of E(T).times.(Tg-T) represented in equation 1 was calculated
with respect to sample Nos. 1, 2, 3, 4, 6, 8, 9, and 10 shown in
table 1.
[0060] The results are shown in table 2. In table 2, samples are
listed by sorting in an ascending order with respect to the value
of E(25.degree. C.).times.(Tg-25.degree. C.). The adhesive
deformation of the slider at 25.degree. C. is also listed.
2TABLE 2 Adhesive E(25.degree. C.) .multidot. (Tg-25.degree. C.)
deformation Sample (Logarithmic value (Crown height) (nm) No.
Adhesive in parentheses) 25.degree. C. 3 Acrylic 1,200 (3,079) 0.4
4 Acrylic 7,000 (3,845) 0.4 1 Epoxy 45,000 (4,653) 0.4 6 Acrylic
132,000 (5,121) 1.3 8 Acrylic 234,000 (5,326) 2.0 9 Acrylic 392,200
(5,594) 9.8 2 Epoxy 1,444,500 (6,160) 27.4 10 Cyanoacrylate
1,554,000 (6,191) 22.8
[0061] As shown in table 2, as the value of E(25.degree.
C.).times.(Tg-25.degree. C.) increases, the adhesive deformation of
the slider at 25.degree. C. increases.
[0062] As indicated in equation 1, .DELTA..alpha. (a difference in
coefficient of thermal expansion between the slider and the
flexure) is a constant, in order to decrease a thermal stress
.delta., it is recommended that the value of E(T).times.(Tg-T) be
decreased.
[0063] At an operating temperature of 25.degree. C., as shown in
table 2, sample Nos. 3, 4, 1, 6, and 8 can suppress the adhesive
deformation to 3 nm or less. In sample No. 3, as shown in table 1,
the bond strength at 25.degree. C. is as low as 30 gf.
[0064] Accordingly, preferable samples in table 2 are Nos. 4, 1, 6,
and 8, and these samples have a value of E(25.degree.
C.).times.(Tg-25.degree. C.) in the range of 7,000 to 234,000
kg.multidot..degree.C./cm.sup.2.
[0065] That is, by selecting a resin adhesive that has a value of
E(25.degree. C.).times.(Tg-25.degree. C.) in the range of 7,000 to
234,000 kg.multidot..degree.C./cm.sup.2 at an operating temperature
of 25.degree. C., the adhesive deformation of the slider can be
suppressed to 3 nm or less, and also, a bond strength of 50 gf or
more can be obtained.
[0066] When a conductive resin film is formed between the leading
end of the slider and the flexure, since the conductive resin film
must be a flexible adhesive the same as the resin adhesive, the
conductive resin film must have the same properties as those of the
resin adhesive described above.
BRIEF DESCRIPTION OF THE DRAWINGS
[0067] FIG. 1 is a partial side view which shows a floating type
magnetic head device for use in a hard disk apparatus or the like
as an embodiment of the present invention;
[0068] FIG. 2 is a partial perspective view of the tip region of
the magnetic head device shown in FIG. 1 taken from the reverse
side; and
[0069] FIG. 3 is a side view which shows a conventional floating
type magnetic head device for use in a hard disk apparatus or the
like.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0070] FIG. 1 is a partial side view which shows a floating type
magnetic head device for use in a hard disk apparatus or the like
and FIG. 2 is a partial perspective view of the tip region of the
magnetic head device shown in FIG. 1 taken from the reverse
side.
[0071] The magnetic head device includes a slider 1 and a support 2
for supporting the slider 1.
[0072] The slider 1 is composed of a ceramic material and a
thin-film element 4 is provided on the trailing end B of the slider
1. An air bearing surface (ABS) la is formed on the surface of the
slider 1 facing a disk D.
[0073] The thin-film element 4 is formed by depositing a magnetic
material such as Permalloy (an Ni--Fe alloy) and an insulating
material such as alumina. The thin-film element 4 includes a
magnetic detecting section for reproducing magnetically recorded
signals recorded in the disk D or a magnetic recording section for
recording magnetic signals in the disk D, or both the magnetic
detecting section and the magnetic recording section. The magnetic
detecting section is, for example, an MR head including a
magnetoresistive element (MR element). The magnetic recording
section includes an inductive head in which a coil and a core are
formed by patterning.
[0074] The support 2 includes a load beam 5 and a flexure 6.
[0075] The load beam 5 is composed of a leaf spring material such
as stainless steel. A bent section 5a having rigidity is formed on
each side of the load beam 5 from the upper right side in FIG. 1 to
the vicinity of the top. The bent section 5 extends to the
substantially middle position of the load beam 5, a leaf spring
section (not shown in the drawing) which does not have the bent
section 5a is formed from the end of the bent section 5a through
the base of the load beam 5.
[0076] A spherical pivot 7 which protrudes downward in the drawing
is formed on the planar section sandwiched by the bent section
5a.
[0077] The apex of the pivot 7 abuts against the upper surface of
the slider 1 with a tongue 6b of the flexure 6 therebetween.
[0078] The flexure 6 is composed of a leaf spring such as stainless
steel. The flexure 6 includes a fixed section 6a and the tongue 6b,
and a step 6c connects the fixed section 6a to the tongue 6b.
[0079] As shown in FIG. 1, to the lower surface of the tongue 6b,
the slider 1 is bonded with a resin adhesive 8.
[0080] As shown in FIG. 2, in the tip region of the flexure 6, a
conductive pattern 14 is formed from the fixed section 6a through
the tongue 6b. The width of the conductive pattern 14 formed on the
tongue 6b increases toward the base end of the flexure 6 to form a
connection 14a which connects to the slider 1.
[0081] On the trailing end B of the slider 1, an electrode terminal
section 4a formed of a thin film extracted from the thin-film
element 4 is provided at the same distance as that of the
connection 14a.
[0082] In the present invention, the electrode terminal section 4a
provided on the trailing end B of the slider 1 and the connection
14a provided on the flexure 6 are rigidly bonded together by a
joint 9 formed by ball bonding using gold (Au) or the like.
[0083] The joint 9 is covered with a reinforcing resin film 10 for
protection, as shown in FIG. 1.
[0084] When the trailing end B of the slider 1 is rigidly bonded to
the tongue 6b of the flexure 6 by the joint 9 formed by ball
bonding using Au or the like as described above, since the slider 1
has a coefficient of thermal expansion which is different from that
of the flexure 6, the resin adhesive (after curing) 8 for bonding
the slider 1 and the tongue 6b must be a flexible adhesive which
can absorb (buffer) the strain E caused by the difference in
coefficient of thermal expansion between the slider 1 and the
flexure 6 and can decrease internal stress resulting from curing
shrinkage.
[0085] In the present invention, as the flexible resin adhesive 8,
for example, an adhesive containing a thermoplastic resin such as
an acrylic resin, a polyurethane resin, a polyester resin, or a
nylon resin as a major constituent, or containing a thermosetting
resin such as an epoxy resin which is flexible in the operating
temperature region may be selected.
[0086] Although the method for curing the resin adhesive 8 may
include a reactive process such as heating or UV radiation, or a
solvent drying process, in the present invention, the method for
curing is not limited to any one of the above.
[0087] Next, with respect to the properties of the resin adhesive 8
(after curing), in the present invention, the resin adhesive 8
preferably has a Young's modulus E in the range of 700 to 5,200
kg/cm.sup.2 at 25.degree. C. and a bond strength (peel strength) of
50 gf or more.
[0088] In addition, preferably, the resin adhesive 8 has a glass
transition temperature Tg in the range of 4 to 70.degree. C.
[0089] If the resin adhesive 8 has a Young's modulus E in the range
of 700 to 5,200 kg/cm.sup.2 at 25.degree. C., the adhesive
deformation of the slider 1 can be reduced.
[0090] Specifically, when the ABS la of the slider 1 protrudes in
the direction of the disk D and a distance between the peak of the
protrusion and the flat or crown ABS la before deformation is
defined as an adhesive deformation, the adhesive deformation can be
set at 3 nm or less in the range of 5 to 50.degree. C., and a
difference between the adhesive deformation at 5.degree. C. and the
adhesive deformation at 50.degree. C. can be set at 3 nm or
less.
[0091] Accordingly, the absolute value of the variation in the
flying height .delta.1 (refer to FIG. 1) in response to temperature
can be suppressed to 3 nm or less, and thus, problems such as
collision of the trailing end B of the slider 1 with the disk D or
a decrease in output because of an increase in the flying height
.delta.1 as has been experienced in the past will not occur.
[0092] Also, preferably, at an operating temperature T of
25.degree. C., the product obtained by multiplying the Young's
modulus E at 25.degree. C. by the difference when 25.degree. C. is
subtracted from Tg (Tg-25.degree. C.) is in the range of 7,000 to
234,000 kg.multidot..degree.C./cm.sup.2 If the value E (25.degree.
C.).times.(Tg-25.degree. C.) ranges from 7,000 to 234,000
kg.multidot..degree.C./cm.sup.2, the adhesive deformation of the
slider 1 at 25.degree. C. can be suppressed to 3 nm or less, and
the bond strength (peel strength) at 25.degree. C. can be increased
to 50 gf or more.
[0093] As shown in FIG. 1, when a fillet conductive resin film 11
is formed between the leading end A of the slider 1 and the tongue
6b of the flexure 6, the conductive resin film 11 preferably has
the same properties as those of the resin adhesive 8.
[0094] The reason for providing the conductive resin film 11 is to
secure electrical connection between the slider 1 and the flexure
6.
[0095] The magnetic head in the present invention described above
is used for a CSS type hard disk apparatus (apparatus for magnetic
recording and reproducing). When the disk stops, the slider 1 is
pressed toward the upper surface of the disk D by means of elastic
force of the leaf spring section at the base of the load beam 5,
and the ABS la of the slider 1 is brought into contact with the
surface of the disk D. When the disk D starts to rotate, the entire
slider 1 is lifted by a short distance .delta.1 from the surface of
the disk D because of an airflow between the slider 1 and the disk
D. The leading end A may be lifted higher above the disk D than the
trailing end B, or the leading end A only may be lifted from the
surface of the disk and the trailing end B may come into contact
with the surface of the disk D continuously or discontinuously
during rotation.
[0096] As described above, in the present invention, the flexible
resin adhesive 8 (after curing) is used to bond the slider 1 and
the tongue 6b of the flexure 6, a portion of the strain E between
the slider 1 and the tongue 6b can be absorbed (buffered) by
deformation of the resin adhesive 8, and the thermal stress .delta.
that affects the slider 1 can be reduced, enabling a decrease in
the adhesive deformation of the slider 1.
[0097] Specifically, the resin adhesive 8 preferably has a Young's
modulus E in the range of 700 to 5,200 kg/cm.sup.2 at 25.degree. C.
and a bond strength (peel strength) of 50 gf or more. A resin
adhesive 8 having the above properties can suppress the adhesive
deformation of the slider 1, to 3 nm or less.
[0098] Preferably, the resin adhesive 8 has a glass transition
temperature Tg in the range of 4 to 70.degree. C.
[0099] Also, in the present invention, the resin adhesive 8
preferably has a product obtained by multiplying the Young's
modulus E at 25.degree. C. by (Tg-25.degree. C.) in the range of
7,000 to 234,000 kg.multidot..degree.C./cm.sup.2.
[0100] If the value of E (25.degree. C.).times.(Tg-25.degree. C.)
is in the range of 7,000 to 234,000
kg.multidot..degree.C./cm.sup.2, the adhesive deformation of the
slider 1 at 25.degree. C. can be suppressed to 3 nm or less and the
bond strength (peel strength) at 25.degree. C. can be increased to
50 gf or more.
[0101] As described above, in the present invention, adhesive
deformation of the slider 1 can be decreased, and specifically can
be suppressed to 3 nm or less. Thus, spacing loss can be reduced,
stable output signals are obtainable, and the minimum flying height
can be secured.
[0102] As described above in detail, in the present invention,
since a resin adhesive such as a thermoplastic resin which is
flexible after curing is used in order to bond the slider and the
flexure together, a portion of the strain between the slider and
the flexure caused by the difference in coefficient of thermal
expansion can be absorbed by deformation of the resin adhesive,
enabling a decrease in the adhesive deformation of the slider.
[0103] With respect to properties of the resin adhesive, in the
present invention, the resin adhesive preferably has a Young's
modulus E in the range of 700 to 5,200 kg/cm.sup.2 at 25.degree. C.
and a bond strength (peel strength) of 50 gf or more.
[0104] Also, preferably, the resin adhesive has a glass transition
temperature Tg in the range of 4 to 70.degree. C.
[0105] By using a resin adhesive having the properties described
above, the adhesive deformation can be suppressed to 3 nm or less,
and thus, a stable output can be obtained and the minimum flying
height can be secured.
* * * * *