U.S. patent application number 12/805279 was filed with the patent office on 2011-09-01 for nozzle plate containing multiple micro-orifices for cascade impactor and method for manufacturing the same.
This patent application is currently assigned to NATIONAL CHIAO TUNG UNIVERSITY. Invention is credited to Hong-Dar Chen, Sheng-Chieh Chen, Chuen-Jinn Tsai.
Application Number | 20110209528 12/805279 |
Document ID | / |
Family ID | 44504550 |
Filed Date | 2011-09-01 |
United States Patent
Application |
20110209528 |
Kind Code |
A1 |
Tsai; Chuen-Jinn ; et
al. |
September 1, 2011 |
Nozzle plate containing multiple micro-orifices for cascade
impactor and method for manufacturing the same
Abstract
A nozzle plate containing multiple micro-orifices for the
cascade impactor and a method for manufacturing the same are
disclosed. The nozzle plate is formed by a series of semiconductor
processes, including lithography, etching and electroplating. The
nozzle plate comprises a plate body and a plurality of
micro-orifices formed on the plate body. The orifice has a diameter
which gradually expands in the direction away from the bottom of
the plate body to achieve a smooth inner surface, allowing
particles to pass therethrough smoothly without being clogged in
the nozzle plate.
Inventors: |
Tsai; Chuen-Jinn; (Hsinchu
County, TW) ; Chen; Sheng-Chieh; (Taipei County,
TW) ; Chen; Hong-Dar; (Kaohsiung County, TW) |
Assignee: |
NATIONAL CHIAO TUNG
UNIVERSITY
Hsinchu City
TW
|
Family ID: |
44504550 |
Appl. No.: |
12/805279 |
Filed: |
July 22, 2010 |
Current U.S.
Class: |
73/28.05 ;
216/37 |
Current CPC
Class: |
G01N 15/0255 20130101;
G01N 2015/0261 20130101; B44C 1/227 20130101; G01N 1/2208
20130101 |
Class at
Publication: |
73/28.05 ;
216/37 |
International
Class: |
G01N 1/22 20060101
G01N001/22; B05D 3/10 20060101 B05D003/10 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 1, 2010 |
TW |
99105869 |
Claims
1. A nozzle plate for a multi-stage cascade impactor, comprising: a
plate body; and a plurality of micro-orifices formed on the said
plate body and cutting through top and bottom sides of the said
plate body, each said micro-orifice having a smooth inner surface
and a diameter expanding gradually in direction from the bottom
side of said the plate body toward the top side thereof.
2. The nozzle plate as claimed in claim 1, wherein the number of
the said micro-orifices is within 50-10000.
3. The nozzle plate as claimed in claim 1, wherein the number of
the said micro-orifices is within 900-2000.
4. The nozzle plate as claimed in claim 1, further comprising a
plurality of annular protrusions protruded from the bottom side of
said plate body around each said micro-orifice.
5. The nozzle plate as claimed in claim 1, wherein the diameter of
each said micro-orifice at the bottom side of said plate body is
within 45-410 .mu.m.
6. A method for making a nozzle plate containing multiple
micro-orifices, comprising the steps of: (1) depositing a seed
layer on a substrate; (2) coating the said seed layer with a layer
of first photoresist, radiating UV light through a first mask onto
said first photoresist, and then developing the first photoresist;
(3) etching said seed layer and removing the said first
photoresist, so as to form a plurality of through holes on said
seed layer that cut through top and bottom sides of said seed
layer; (4) coating a sacrificial layer on said substrate and said
seed layer; (5) depositing a metal mask film on said sacrificial
layer; (6) coating a layer of second photoresist on the said metal
mask film, radiating UV light through a second mask onto the said
second photoresist, and then developing the second photoresist; (7)
etching the said metal mask film and removing the said second
photoresist, so as to form a plurality protrusions on the said
sacrificial layer; (8) etching the said sacrificial layer until
said substrate and the said seed layer are exposed to the outside;
(9) electroplating a metal material onto the said seed layer; and
(10) removing the said substrate, the said seed layer and the said
sacrificial layer.
7. The method for making a nozzle plate containing multiple
micro-orifices as claimed in claim 6, wherein the metal material
used during step (9) is a mix of nickel and cobalt.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to aerosol sampling
technology, and more particularly to a nozzle plate containing
multiple micro-orifices for use in a cascade impactor and a method
for manufacturing the same.
[0003] 2. Description of the Related Art
[0004] The Micro-Orifice Uniform Deposit Impactor (MOUDI) invented
by MSP Corporation has been widely used for size-classified aerosol
sampling. Each stage of the MOUDI consists of a nozzle plate with a
plurality of nozzles and an impaction plates to collect particles
of a specific size range. By decreasing the nozzle diameter and
increasing the air jet speed in the nozzle from the top to the
bottom stages, the MOUDI is able to collect particles of
subsequently smaller size ranges. In a 10 stage MOUDI, the cutoff
aerodynamic diameter of the stage 0 to 10 is 18, 10.0, 5.6, 3.2,
1.8, 1.0, 0.56, 0.32, 0.18, 0.1, 0.056 .mu.m, respectively, and
there is a final after filter to collect particles smaller than
0.056 .mu.m. To classify very small particles, the nozzle plates of
the last 4 impaction stages, or stage 7 to 10, use 900-2000
micro-orifices with the diameter ranging from 140 to 52 .mu.m to
collect particles ranging from 0.32 to 0.056 .mu.m in diameter.
[0005] U.S. Pat. No. 6,431,014 disclosed an improved MOUDI design
with a series of differential pressure sensors for measuring the
pressure drop across the nozzle plates. Additionally, the influence
of particle accumulation and blockage in the micro-orifices on the
performance of the MOUDI is also briefly discussed. The clogged
orifices may cause the cut-point of the impactor to change which
leads to measurement errors. The dust accumulation problem in the
nozzle can be eliminated by periodic cleaning. However, an improper
cleaning method, such as high intensity ultrasonic cleaning, may
damage the nozzle plates whose wall thickness to define the nozzle
diameter is very thin.
[0006] Ji et al. (2006) observed the 6.sup.th to 8.sup.th stage
nozzle plate of a 8-stage MOUDI by using an electron microscope,
and the results were published in a journal paper (Ji, J. H., Bae,
G. N., Hwang, J., 2006. Observation and evaluation of nozzle
clogging in a micro-orifice impactor used for atmospheric aerosol
sampling, Particulate Sci. Technol. 24: 85-96). In the study,
nozzle clogging caused by particle deposition in the nozzle was
observed. The collection efficiency curves were shifted to that
corresponding to smaller orifice sizes, and the 50% cutoff sizes
were much smaller than those specified by the manufacturer for the
three stages with nozzles less than 400 .mu.m in diameter. The
pressure drops across the clogged nozzles were also higher than the
nominal values given by the manufacturer.
[0007] The inventor of the present invention used an optical
microscope to observe the micro-orifices of the nozzle plate of the
last several stages of the MOUDI. An uneven inner surface of the
micro-orifices was observed (see FIG. 11). In the current method,
the major part of the nozzle is made by the wet etching process
while the final bottom part of the orifice has to be made by laser
drilling to define a known orifice diameter. Due to the thickness
limitation of laser drilling used to manufacture the orifice, the
wall thickness D1 at the bottom side of each micro-orifice is only
about 10 .mu.m. This is the main reason why there exists an abrupt
step at the bottom of the orifice which renders clogging of
particles easily. Besides, this fragile structure prevent the
nozzle plates from being cleaned effectively, such as by an
ultrasonic cleaner. Improvement of the structure and the shape of
the micro-orifices for the nozzle plate is therefore critically
needed.
SUMMARY OF THE INVENTION
[0008] It is the main object of the present invention to provide a
nozzle plate with multiple micro-orifices for a cascade impactor
and a method for manufacturing the same, wherein the micro-orifices
of the nozzle plate have a smooth inner surface, avoiding clogging
of particles in the nozzle plate.
[0009] It is another object of the present invention to provide a
nozzle plate for a cascade impactor and a method for manufacturing
the same, wherein the uniform wall thickness and sturdy structure
of the micro-orifices facilitate cleaning by an ultrasonic
cleaner.
[0010] To achieve these and other objects of the present invention,
a nozzle plate for a multi-stage cascade impactor comprises a plate
body, and a plurality of micro-orifices formed on the plate body
and cutting through top and bottom sides of the plate body. Each
micro-orifice has a smooth inner surface and a diameter expanding
gradually in direction from the bottom side of the plate body
toward the top side thereof. Further, the number of the
micro-orifices is preferably within 50-10000, and the diameter of
each micro-orifice at the bottom side of the plate body is within
45-410 .mu.m. The nozzle plate further comprises a plurality of
annular protrusions protruded from the bottom side of the plate
body around each micro-orifice.
[0011] To achieve these and other objects of the present invention,
a method for making a nozzle plate containing multiple
micro-orifices comprises the steps of:
[0012] (1) depositing a seed layer on a substrate; (2) coating the
seed layer with a layer of first photoresist, radiating UV light
through a first mask onto the first photoresist, and then
developing the first photoresist; (3) etching the seed layer and
removing the first photoresist, so as to form a plurality of
through holes on the seed layer that cut through top and bottom
sides of the seed layer; (4) coating a sacrificial layer on the
substrate and the seed layer; (5) depositing a metal mask film on
the sacrificial layer; (6) coating a layer of second photoresist on
the metal mask film, radiating UV light through a second mask onto
the second photoresist, and then developing the second photoresist;
(7) etching the metal mask film and removing the second
photoresist, so as to form a plurality of protrusions on the
sacrificial layer; (8) etching the sacrificial layer until the
substrate and the seed layer are exposed to the outside; (9)
electroplating a metal material onto the seed layer; and (10)
removing the substrate, the seed layer and the sacrificial layer.
Further, the metal material used during step (9) is a mix of nickel
and cobalt.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a schematic drawing showing the fabrication of a
nozzle plate containing a plurality of micro-orifices for cascade
impactor in accordance with the present invention (I).
[0014] FIG. 2 is a schematic drawing showing the fabrication of a
nozzle plate containing a plurality of micro-orifices for cascade
impactor in accordance with the present invention (II).
[0015] FIG. 3 is a schematic drawing showing the fabrication of a
nozzle plate containing a plurality of micro-orifices for cascade
impactor in accordance with the present invention (III).
[0016] FIG. 4 is a schematic drawing showing the fabrication of a
nozzle plate containing a plurality of micro-orifices for cascade
impactor in accordance with the present invention (IV).
[0017] FIG. 5 is a schematic drawing showing the fabrication of a
nozzle plate containing a plurality of micro-orifices for cascade
impactor in accordance with the present invention (V).
[0018] FIG. 6 is a schematic drawing showing the fabrication of a
nozzle plate containing a plurality of micro-orifices for cascade
impactor in accordance with the present invention (VI).
[0019] FIG. 7 is a schematic drawing showing the fabrication of a
nozzle plate containing a plurality of micro-orifices for cascade
impactor in accordance with the present invention (VII).
[0020] FIG. 8 is a schematic drawing showing the fabrication of a
nozzle plate containing a plurality of micro-orifices for cascade
impactor in accordance with the present invention (VIII).
[0021] FIG. 9 is a schematic drawing showing the fabrication of a
nozzle plate containing a plurality of micro-orifices for cascade
impactor in accordance with the present invention (IX).
[0022] FIG. 10 is a schematic drawing showing the fabrication of a
nozzle plate containing a plurality of micro-orifices for cascade
impactor in accordance with the present invention (X).
[0023] FIG. 11 is a schematic sectional view of a nozzle plate for
cascade impactor made according to the prior art design.
DETAILED DESCRIPTION OF THE INVENTION
[0024] Referring to FIGS. 1-10, a method for the fabrication of a
nozzle plate having multiple micro-orifices for the cascade
impactor in accordance with the present invention includes the
steps of:
[0025] (1) depositing a seed layer 22 on a glass substrate 20, as
shown in FIG. 1, wherein copper or chromium can be used to deposit
the seed layer 22 by a sputtering process, an evaporation process
or a chemical vapor deposition (CVD) process; the seed layer 22 has
a thickness D2 about 3 .mu.m;
[0026] (2) coating the seed layer 22 with a layer of first
photoresist 24, radiating UV light through a first mask 26 onto the
first photoresist 24, and then developing the first photoresist 24,
as shown in FIG. 2, wherein the first mask 26 has a plurality of
transparent regions 261 for the passing of the applied UV light;
for the sake of brevity, only one transparent region 261 is seen in
FIG. 2;
[0027] (3) etching the seed layer 22 and removing the first
photoresist 24, as shown in FIG. 3, so as to form a plurality of
through holes 221 on the seed layer 22 that cut through top and
bottom sides of the seed layer 22;
[0028] (4) coating a sacrificial layer 28 on the glass substrate 20
and the seed layer 22, as shown in FIG. 4, wherein the sacrificial
layer 28 can be prepared from, for example, but not limited to,
polyimide (PI);
[0029] (5) using copper or chromium to deposit a metal mask film 30
on the sacrificial layer 28 by a sputtering process, an evaporation
process or a chemical vapor deposition process, as shown in FIG.
5;
[0030] (6) coating a layer of second photoresist 32 on the metal
mask film 30, radiating UV light through a second mask 34 onto the
second photoresist 32, and then developing the second photoresist
32, as shown in FIG. 6, wherein the second mask 34 has a plurality
of circular opaque regions 341 at locations corresponding to the
first through holes 221 on the seed layer 22;
[0031] (7) etching the metal mask film 30 and removing the second
photoresist 32, as shown in FIG. 7, so as to form a plurality of
protrusions 301 on the sacrificial layer 28; for the sake of
brevity, only one circular opaque region 341 and one protrusion 301
are respectively seen in FIGS. 6 and 7;
[0032] (8) etching the sacrificial layer 28 until the glass
substrate 20 and the seed layer 22 are exposed to the outside, as
shown in FIG. 8;
[0033] (9) electroplating a metal material 36 onto the seed layer
22 to a desired thickness D3, as shown in FIG. 9, wherein the metal
material can be, but not limited to, a mix of nickel and cobalt,
and the thickness D3 of the metal material 36 is 150 .mu.m; and
[0034] (10) removing the substrate 20, the seed layer 22 and the
sacrificial layer 28, thereby obtaining a nozzle plate 10, as shown
in FIG. 10, which is to be processed further through a series of
cutting and hole-drilling processes for installation in a
multi-stage cascade impactor.
[0035] Referring to FIG. 10, a nozzle plate 10 for cascade impactor
in accordance with the present invention is made through a series
of semiconductor processes, including lithography, etching and
electroplating. The nozzle plate 10 comprises a plate body 12 and a
plurality of micro-orifices 14 cut through top and bottom sides of
the plate body 12. Because the nozzle plate 10 is formed by means
of electroplating, the micro-orifices 14 have a smooth inner
surface and a diameter which expands gradually from the bottom side
of the plate body 12 toward the top side thereof. Further, the
nozzle plate 10 has an annular protrusion 16 protruded from the
bottom side around each of the micro-orifices 14.
[0036] Further, the smooth inner surfaces of the micro-orifices 14
allow particles to pass therethrough smoothly without clogging the
micro-orifices. Further, the uniform wall thickness and sturdy
structure of the micro-orifices 14 facilitate cleaning by an
ultrasonic cleaner and improve the convenience of use and the
sampling quality. Further, subject to different desired cut-off
aerodynamic diameters, the number of the micro-orifices 14 of the
nozzle plate 10 and their final orifice diameter can be 900/140
.mu.m, 900/90 .mu.m, 2000/55 .mu.m, 2000/52 .mu.m, 980/49 .mu.m,
1650/450 .mu.m or 2000/55 .mu.m. Preferably, the number of the
micro-orifices 14 is within 50-10000, and the diameter is within
45-410 .mu.m.
[0037] Although particular embodiments of the invention have been
described in detail for purposes of illustration, various
modifications and enhancements may be made without departing from
the spirit and scope of the invention. Accordingly, the invention
is not to be limited except as by the appended claims.
* * * * *