U.S. patent application number 10/007820 was filed with the patent office on 2002-05-16 for heat exchanger.
This patent application is currently assigned to Fujikoshi Machinery Corp.. Invention is credited to Nakamura, Yoshio, Otsuka, Yoshio.
Application Number | 20020056548 10/007820 |
Document ID | / |
Family ID | 18855732 |
Filed Date | 2002-05-16 |
United States Patent
Application |
20020056548 |
Kind Code |
A1 |
Nakamura, Yoshio ; et
al. |
May 16, 2002 |
Heat exchanger
Abstract
The heat exchanger of the present invention is capable of easily
adjusting temperature of a machining liquid, e.g., slurry, etching
liquid. The heat exchanger of the present invention, which adjusts
temperature of the machining liquid, comprises a ceramic heat
exchanging tube, which is made by baking silicon carbide (SiC).
Inventors: |
Nakamura, Yoshio;
(Nagano-shi, JP) ; Otsuka, Yoshio; (Nagano-shi,
JP) |
Correspondence
Address: |
JORDAN AND HAMBURG LLP
122 EAST 42ND STREET
SUITE 4000
NEW YORK
NY
10168
US
|
Assignee: |
Fujikoshi Machinery Corp.
Nagano-shi
JP
|
Family ID: |
18855732 |
Appl. No.: |
10/007820 |
Filed: |
December 5, 2001 |
Current U.S.
Class: |
165/154 ;
165/905 |
Current CPC
Class: |
Y10T 29/5176 20150115;
F28D 7/106 20130101; Y10T 29/4935 20150115; B24B 57/02 20130101;
Y10S 165/905 20130101; F28F 21/04 20130101; Y10T 29/49361
20150115 |
Class at
Publication: |
165/154 ;
165/905 |
International
Class: |
F28D 007/10 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 21, 2000 |
JP |
2000-389115 |
Claims
What is claimed is:
1. A heat exchanger for adjusting temperature of a machining
liquid, comprising: a ceramic heat exchanging tube, which is made
by baking silicon carbide (SiC).
2. The heat exchanger according to claim 1, further comprising
inlets and outlets of the machining liquid and a lilquid for
adjusting temperature, wherein said inlets and outlets make the
both liquids flow as countercurrents.
3. The heat exchanger according to claim 1, wherein said ceramic
heat exchanging tube includes no boron (B).
4. The heat exchanger according to claim 3, further comprising
inlets and outlets of the machining liquid and a liquid for
adjusting temperature, wherein said inlets and outlets make the
both liquids flow as countercurrents.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a heat exchanger, more
precisely relates to a heat exchanger capable of adjusting
temperature of a machining liquid, e.g., slurry of abrading or
cutting work pieces.
[0002] In the case of abrading silicon wafers, the silicon wafers
are abraded by, for example, an abrasive machine 10 shown in FIG.
2. In the abrasive machine 10, abrasive cloth 14 is adhered on an
abrasive plate 12 rotating. A silicon wafer 16 is pressed onto the
abrasive cloth 14 by an abrasive head 20, so that a surface of the
silicon wafer 16 can be abraded. Slurry including abrasive grains
is supplied to the surface of the silicon wafer 16, and the used
slurry is collected to reuse.
[0003] Namely, the slurry, in which abrasive grains are mixed, is
dropped onto the abrasive cloth 14 so as to abrade the surface of
the wafer 16, then the slurry is discharged from the abrasive cloth
14 to a collecting section 18, which is provided outside of the
abrasive plate 12. The slurry discharged to the collecting section
18 has been heated by friction between the surface of the wafer 16
and the abrasive clothe 14, so the discharged slurry must be
cooled, by a heat exchanger "H", until reaching prescribed
temperature. Then, abraded dusts included in the discharged slurry,
which has been cooled, are removed by a removing unit 22. The
slurry, from which the abraded dusts have been removed, is
reservoired in a tank 24, and the slurry in the tank 24 is supplied
to the abrasive cloth 14 again, by a pump 26, via an
electromagnetic valve 28.
[0004] By providing the heat exchanger "H" in a circulation circuit
of the slurry, temperature of the slurry in the tank 24 can be
maintained at prescribed temperature, and the silicon wafers 16 can
be abraded with fixed abrasive rate without heat-deformation of the
abrasive plate 12. In some cases, etching liquid is used as the
machining liquid. Generally, etching function of the etching liquid
highly depends on temperature. If the temperature of the etching
liquid is high, the etching function is sharply made greater, so it
is difficult to control etching rate.
[0005] The abrasive plate 12 is heated by frictional heat between
the surface of the wafer 16 and the abrasive cloth 14, and the
abrasive plate 12 deforms when the abrasive plate 12 is overheated,
so that accuracy of abrading the surface of the wafer 16 becomes
low.
[0006] By providing the heat exchanger "H" so as to maintain the
temperature of the slurry in the tank 24, the sharp increase of the
etching function can be prevented, so that the etching rate can be
easily controlled. Further, the heat of the liquid supplied to the
abrasive plate 12 can be removed, so that the heat-deformation of
the abrasive plate 12 can be prevented. The wafers 16 can be stably
abraded with high abrasive accuracy.
[0007] A conventional heat exchanger "H" is shown in FIG. 5. The
heat exchanger 180 is a double-tube type including: an inner heat
exchanging tube 100, in which the discharged slurry flows; and an
outer tube 102, in which cooling water flows along an outer
circumferential face of the inner heat exchanging tube 100. The
inner heat exchanging tube 100 is a fluororesin tube or a stainless
tube coated with fluororesin; the outer tube 102 is made of vinyl
chloride. As clearly shown in FIG. 5, an inlet 104 and an outlet
106 of the discharged slurry, which are provided to the heat
exchanging tube 100, and an inlet 108 and an outlet 110 of the
cooling water, which are provided to the outer tube 102, are
arranged so as to flow the discharged slurry and the cooling water
as countercurrents.
[0008] In the abrasive machine shown in FIG. 3, which has the heat
exchanger "H", the discharged slurry heated by the frictional heat
can be cooled. Even if the slurry is circulated to reuse, the
wafers 16 can be stably abraded.
[0009] However, heat conductivity of the heat exchanging tube 100
made of fluororesin is low. Therefore, a broad heat conductive area
is required so as to properly remove the heat, so that the heat
exchanger 180 must be large. If the heat exchanger 180 is large,
residence time of the machining liquid in the heat exchanger 180
must long, so that accuracy of controlling the temperature of the
machining liquid, e.g., slurry, etching liquid, is low, the
abrasive plate 12 deforms, and the etching function of the etching
liquid is badly influenced.
[0010] In the case of the stainless heat exchanging tube which is
not coated with fluororesin, the heat conductivity is high, so the
heat conductive area can be small and size of the heat exchanger
can be small.
[0011] However, metal ions solved out from the stainless tube stick
onto the surface of the silicon wafer 16 to be abraded, so that
function of semiconductor chips are badly influenced.
SUMMARY OF THE INVENTION
[0012] An object of the present invention is to provide a heat
exchanger, which includes a heat exchanging tube, whose heat
conductivity is greater than that of the conventional fluororesin
tube and from which no metal ions are solved out, and which is
capable of easily adjusting temperature of a machining liquid,
e.g., slurry, etching liquid.
[0013] The inventors of the present invention studied and found
that the heat conductivity of a ceramic, which is made by baking
silicon carbide, is 250 times as much as that of
polytetrafluoroethylene, which is an example of fluororesin, and
4.5 times as much as stainless steel, and no metal ions are solved
out from the ceramic.
[0014] Then, the inventors found that the heat exchanging tube made
of the ceramic, which is made by baking silicon carbide (SiC), can
be effectively used.
[0015] Namely, the heat exchanger of the present invention, which
adjusts temperature of a machining liquid, comprises: a ceramic
heat exchanging tube, which is made by baking silicon carbide
(SiC).
[0016] In the heat exchanger, the ceramic heat exchanging tube may
include no boron (B). With this structure, no boron (B) solved out
from the heat exchanging tube is included in the machining liquid,
the surface of the work piece, e.g., silicon wafer, is not
contaminated.
[0017] The heat exchanger may further comprise inlets and outlets
of the machining liquid and a liquid for adjusting temperature, and
the inlets and outlets make the both liquids may flow as
countercurrents. With this structure, temperature of the machining
liquid can be easily adjusted.
[0018] In the heat exchanger of the present invention, the heat
exchanging tube is the ceramic tube made by baking silicon carbide
(SiC). The heat conductivity of the ceramic is highly greater than
that of fluororesin and stainless steel, and no metal ion are
solved into the machining liquid.
[0019] Therefore, heat exchange between the machining liquid and
the temperature-adjusting liquid can be rapidly executed, and the
temperature of the machining liquid can be easily adjusted.
[0020] Unlike the conventional heat exchanger including the
fluororesin heat exchanging tube, the heat conductive area of the
ceramic heat exchanging tube can be small and the size of the heat
exchanger can be small. Therefore, the residence time of the
machining liquid in the heat exchanger of the present invention can
be shorter, and the temperature of the machining liquid can be
precisely adjusted. Further, rate of abrading or cutting work
pieces can be easily controlled, and flatness of abraded faces or
cut faces of the work pieces can be improved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Embodiments of the present invention will now be described
by way of examples and with reference to the accompanying drawings,
in which:
[0022] FIG. 1 is a partial sectional view of a heat exchanger
relating to the present invention;
[0023] FIG. 2 is a schematic view of an abrasive machine including
the heat exchanger of the present invention;
[0024] FIG. 3 is a schematic view of another abrasive machine
including the heat exchanger of the present invention;
[0025] FIG. 4 is a schematic view of another abrasive machine
including the heat exchanger of the present invention; and
[0026] FIG. 5 is a partial sectional view of the conventional heat
exchanger.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0027] Preferred embodiments of the present invention will now be
described in detail with reference to the accompanying
drawings.
[0028] An embodiment of the heat exchanger of the present invention
is shown in FIG. 1. The heat exchanger 30 shown in FIG. 1 has a
double-tube structure. Namely, the heat exchanger 30 includes: an
inner ceramic heat exchanging tube 32, in which slurry including
abrasive grains flows; and an outer tube 34, which covers the inner
heat exchanging tube 32 and in which cooling water (the
temperature-adjusting liquid) flows along an outer circumferential
face of the inner heat exchanging tube 32. The inner heat
exchanging tube 32 is made of a ceramic made by baking silicon
carbide (SiC); the outer tube 34 is made of vinyl chloride or
fluororesin. The slurry, which is an example of machining liquid
and which flows in the heat exchanging tube 32, and the cooling
water, which flows in a flow path formed between an inner
circumferential face of the outer tube 34 and the outer
circumferential face of the inner heat exchanging tube 32, may flow
in the same direction. In the present embodiment, as clearly shown
in FIG. 1, an inlet 36 and an outlet 38 of the slurry, which are
provided to the heat exchanging tube 32, and an inlet 40 and an
outlet 42 of the cooling water, which are provided to the outer
tube 34, are arranged so as to flow the slurry and the cooling
water as countercurrents. By forming the countercurrents, the
temperature of the slurry can be easily adjusted in the present
embodiment.
[0029] Connectors, which are made of vinyl chloride or fluororesin,
are respectively attached to the inlet 36 and the outlet 38 of the
ceramic heat exchanging tube 32, and fluororesin tubes (not shown)
are respectively connected to the connectors.
[0030] The ceramic heat exchanging tube 32 of the heat exchanger 30
shown in FIG. 1 is made by baking silicon carbide (SiC) and
includes no boron (B).
[0031] Process of forming the ceramic heat exchanging tube 32 will
be explained. Firstly, powders of silicon carbide and resin, e.g.,
phenolic resin, are mixed, then the mixture is formed into a tube
(a green tube). The green tube is degreased and carbonized in a
nitrogen atmosphere, then it is baked. The baking process comprises
the steps of: heating the tube, under highly vacuumed condition,
until reaching first temperature; introducing argon gas so as to
make argon atmosphere; further heating the tube, in the argon
atmosphere, until reaching second temperature higher than the first
temperature; maintaining the second temperature for prescribed
period of time; and cooling the baked tube.
[0032] The ceramic tube 32 is made by baking silicon carbide (SiC)
without adding boron (B). Bending strength (1000.degree. C. or
more) of the baked tube 32 is lower than that of a baked tube
including boron (B), but maximum temperature of the slurry, which
is frictionally heated in the abrasive machine, is about 60.degree.
C., so the ceramic tube 32 has enough strength and function as the
heat exchanging tube of the heat exchanger 30.
[0033] The ceramic made by baking silicon carbide (SiC) has high
heat conductivity, which is 250 times as much as that of
polytetrafluoroethylene, which is an example of fluororesin, and
4.5 times as much as stainless steel. Therefore, the heat exchange
between the slurry, which flows in the ceramic tube 32, and the
cooling water, which flows in the flow path formed between the
inner circumferential face of the outer tube 34 and the outer
circumferential face of the inner heat exchanging tube 32, can be
rapidly executed, and the temperature of the slurry can be easily
adjusted.
[0034] Unlike the conventional heat exchanger including the
fluororesin heat exchanging tube, the heat conductive area of the
ceramic heat exchanging tube 32 of the heat exchanger 30 can be
small, so that the size of the heat exchanger 30 can be small.
Therefore, the residence time of the slurry in the heat exchanger
30 can be shorter, and the temperature of the machining liquid can
be precisely adjusted.
[0035] Further, the ceramic heat exchanging tube 32 includes no
boron (B); matal ions and boron (B) are not solved and included in
the slurry, so that the surface of the silicon wafer 16 for
semiconductor chips, etc. is not contaminated.
[0036] In the case of employing the heat exchanger 30 shown in FIG.
1 as the heat exchanger "H" of the abrasive machine 10 shown in
FIG. 2, the lower surface of the wafer 16 to be abraded is pressed
onto the abrasive cloth 14 of the abrasive pate 12 rotating by the
abrasive head 20. The slurry reservoired in the tank 24 is dropped
onto the abrasive cloth 14 so as to abrade the surface of the wafer
16. Then the used slurry is discharged from the abrasive cloth 14
to the collecting section 18, which is provided outside of the
abrasive plate 12. The slurry discharged to the collecting section
18 has been heated by friction between the surface of the wafer 16
and the abrasive clothe 14, so the discharged slurry must be cooled
by the heat exchanger 30 until reaching the prescribed temperature.
Abraded dusts included in the cooled slurry are removed by the
removing unit 22. The slurry, from which the abraded dusts have
been removed, is reservoired in the tank 24, and the slurry in the
tank 24 is supplied to the abrasive cloth 14 again, by the pump 26,
via the electromagnetic valve 28.
[0037] By employing the heat exchanger 30 as the heat exchanger "H"
of the abrasive machine 10 shown in FIG. 2, variations of the
temperature of the slurry with respect to the object temperature
can be limited within .+-.1.degree. C. Further, the size of the
heat exchanger 30 can be smaller, so the size of the abrasive
machine 10 too can be smaller.
[0038] In the abrasive machine 10 shown in FIG. 2, the slurry
discharged to the collecting section 18 is introduced to the tank
24 via the heat exchanger 30 and the removing unit 22. Further, the
heat exchanger 30 may be employed in an abrasive machine shown in
FIG. 3. In the abrasive machine shown in FIG. 3, the slurry
discharged to the collecting section 18 is once reservoired in the
tank 24, and the slurry 24 in the tank 24 is circulated by a pump
29. The temperature of the slurry circulating is adjusted by the
heat exchanger 30. The slurry, whose temperature has been adjusted
to the prescribed temperature, is sent to the removing unit 22 by
the pump 26 so as to remove abraded dusts. The slurry, from which
the abraded dusts have been removed, is supplied to the abrasive
cloth 14 again via the electromagnetic valve 28.
[0039] Further, the heat exchanger 30 may be employed in an
abrasive machine shown in FIG. 4. In the abrasive machine shown in
FIG. 4, the slurry discharged to the collecting section 18 is once
reservoired in the tank 24, and the slurry in the tank 24 is
circulated by the pump 26. The temperature of the slurry
circulating is adjusted by the heat exchanger 30. The slurry, whose
temperature has been adjusted to the prescribed temperature, is
sent to the removing unit 22 by the pump 26 so as to remove abraded
dusts. The slurry, from which the abraded dusts have been removed,
is supplied to the abrasive cloth 14 again via the electromagnetic
valve 28.
[0040] In the abrasive machines shown in FIGS. 2-4, the silicon
wafers 16 are abraded as the work pieces. In the case of abrading,
for example, a glass plate, the ceramic heat exchanging tube, which
is made by baking silicon carbide (SiC), may include boron (B).
Even if very small amount of boron (B) is solved in the slurry, it
does not badly influence to the glass plate.
[0041] In the above described embodiments, the heat exchanger 30 is
employed in the abrasive machines. But the heat exchanger 30 shown
in FIG. 1 may be employed in cutting machines. Cutting machines use
slurry including abrasive grains. The slurry is also circulated in
the cutting machine as well as the abrasive machine.
[0042] Especially, in the case of a cutting machine for cutting a
silicon ingot to form silicon wafers, the heat exchanger includes
the ceramic heat exchanging tube. Preferably, the ceramic heat
exchanging tube is made by baking silicon carbide (SiC) and
includes no boron (B) as well as the heat exchanging tube 32 of the
heat exchanger 30 shown in FIG. 1.
[0043] In the cutting machine including the heat exchanger 30 shown
in FIG. 1, the temperature of the slurry for cutting can be
precisely adjusted, and metal ions and boron (B) are not solved,
from the heat exchanging tube, into the slurry. Therefore, products
cut from an ingot, e.g., wafers, are not badly influenced.
[0044] The invention may be embodied in other specific forms
without departing from the spirit or essential characteristics
thereof. The present embodiments are therefore to be considered in
all respects as illustrative and not restrictive, the scope of the
invention being indicated by the appended claims rather than by the
foregoing description and all changes which come within the meaning
and range of equivalency of the claims are therefore intended to be
embraced therein.
* * * * *