U.S. patent application number 14/466490 was filed with the patent office on 2015-02-26 for system for managing a cleanroom environment.
The applicant listed for this patent is Anthony Chien. Invention is credited to Anthony Chien.
Application Number | 20150056909 14/466490 |
Document ID | / |
Family ID | 52480795 |
Filed Date | 2015-02-26 |
United States Patent
Application |
20150056909 |
Kind Code |
A1 |
Chien; Anthony |
February 26, 2015 |
System for Managing a Cleanroom Environment
Abstract
A system for managing cleanroom resources by providing a number
of critical features in an integrated, low-cost package is
described. The critical features include monitoring and recording
cleanroom environmental conditions such as temperature, humidity
and room differential pressure, notifying users of alarm situations
when cleanroom environmental conditions fall outside predetermined
limits, and reducing cleanroom energy usage by turning off HEPA
filter fan units (FFUs) and cleanroom lights when they are not
needed.
Inventors: |
Chien; Anthony; (Laguna
Niguel, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Chien; Anthony |
Laguna Niguel |
CA |
US |
|
|
Family ID: |
52480795 |
Appl. No.: |
14/466490 |
Filed: |
August 22, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61870159 |
Aug 26, 2013 |
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Current U.S.
Class: |
454/187 |
Current CPC
Class: |
F24F 11/61 20180101;
F24F 2110/10 20180101; F24F 11/30 20180101; F24F 11/46 20180101;
F24F 2110/20 20180101 |
Class at
Publication: |
454/187 |
International
Class: |
F24F 3/16 20060101
F24F003/16; F24F 11/00 20060101 F24F011/00 |
Claims
1. In a cleanroom unit comprising an enclosed space supplied with
conditioned air characterized by its temperature, humidity and
differential pressure through electrically powered HEPA filter fan
units and illuminated by electric lights, a system for managing
cleanroom resources by a user comprising: a. means for monitoring
and recording said cleanroom air characteristics comprising: i. an
electronic temperature sensor located within said cleanroom, ii. an
electronic humidity sensor located within said cleanroom, iii. an
electronic room differential pressure sensor located within said
cleanroom, and iv. a personal computer having a graphical user
interface executing a cleanroom control system program, said
personal computer receiving electronic signals from said electronic
temperature, humidity and pressure sensors and providing electronic
control signals for said HEPA filter fan units and said electric
lights; b. means for setting predetermined limits within said
cleanroom control system program executing on said personal
computer that establish an acceptable range of electronic signals
from said temperature, humidity and pressure sensors; c. means for
notifying said user of alarm situations when said cleanroom air
characteristic sensor signals fall outside said predetermined
limits through the graphical user interface of the cleanroom system
control program executing on said personal computer; d. means for
setting predetermined schedules for application of said control
signals for said HEPA filter fan units and said electric lights;
and e. means for reducing cleanroom energy usage by controlling the
electrical power applied to said HEPA filter fan units (FFUs) and
said electric lights in response to said control signals provided
by the cleanroom system control program executing on said personal
computer.
2. The cleanroom management system of claim 1 wherein the means for
monitoring and recording cleanroom air characteristics further
includes an electronic particle detector.
3. The cleanroom management system of claim 1 wherein the means for
notifying said user of alarm situations includes telephone
messaging, text messaging, and e-mail messaging by the cleanroom
system control program executing on said personal computer.
4. The cleanroom management system of claim 1 further comprising
means for monitoring and recording, setting predetermined limits,
notifying the user, setting predetermined schedules, and reducing
cleanroom energy usage for a multiplicity of individual cleanroom
units.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to Provisional application
61/870,159 filed 26 Aug. 2013 which is incorporated herein by
reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Technical Field
[0003] The present invention relates to means for monitoring and
recording cleanroom environmental conditions while providing
warning messages in various formats if the environmental parameters
depart from preset limits. The system also provides a means for
optimizing cleanroom energy consumption.
[0004] 2. Related Background Art
[0005] Cleanrooms are specially constructed, environmentally
controlled enclosed spaces where extensive measures are taken to
eliminate airborne particulates. Cleanrooms may also exhibit tight
controls on temperature, humidity, air pressure, airflow patterns,
air motion, vibration, noise, viable (living) organisms, and
lighting, but the primary design objective of a cleanroom is
particulate control. The term "particulate control" applies to
controlling the concentration and dispersion of both particulate
and microbial contamination within the enclosed space. A cleanroom
is defined in the International Organization for Standardization
(ISO) standard 14644-1 as a "room in which the concentration of
airborne particles is controlled, and which is constructed and used
in a manner to minimize the introduction, generation and retention
of particles inside the room and in which other relevant
parameters, e.g. temperature, humidity and pressure are controlled
as necessary."
[0006] Today, many manufacturing processes require spaces in which
particulate and microbial contamination are tightly controlled
while maintaining reasonable installation and operating costs.
Clean rooms are typically used in manufacturing, packaging, and
research facilities associated with the following industries:
[0007] 1. Semiconductor: This industry drives the state of the art
clean room design, and this industry accounts for a significant
number of all operating clean rooms.
[0008] 2. Pharmaceutical: Clean rooms control living particles that
would produce undesirable bacterial growth in the preparation of
biological, pharmaceutical, and other medical products as well as
in genetic engineering research.
[0009] 3. Aerospace: The manufacturing and assembling of aerospace
electronics, missiles and satellites were the first application of
clean rooms. Large volume clean room spaces with extreme
cleanliness are involved.
[0010] 4. Miscellaneous Applications: Other uses include advanced
materials research, laser and optic industries, microelectronics
facility, paint room and in some aseptic foods production, also in
some high infection risk areas of hospitals. While hospital
operating rooms can be considered clean spaces, their concern is to
control the types of contamination rather than the quantity of
particles present.
[0011] The sources of particulate contamination are generally
categorized as either external sources or internal sources. For any
given space, there exists the external influence of gross
atmospheric contamination. External contamination is brought in
primarily through the air conditioning system through fresh air.
Also, external contamination can infiltrate through building doors,
windows, cracks, and wall penetrations for pipes, cables and ducts.
The external contamination is controlled primarily by using high
efficiency filtration such as high efficiency particle air (HEPA)
filters, by providing positive pressurization of the cleanroom
relative to external spaces to prevent the admission of external
contaminants, and rigorous sealing of potential penetrations into
the cleanroom space.
[0012] The largest potential internal source of contamination is
the clean room workforce. Other sources are the shedding of
surfaces, process equipment and the process itself. People in the
workspace generate particles in the form of skin flakes, lint,
cosmetics, and respiratory emissions. Industry processes generate
particles from mechanical friction between moving parts, combustion
processes, chemical vapors, soldering fumes, and cleaning agents.
The size of these particles ranges from 0.001 microns to several
hundred microns. Particles larger than 5 microns tend to settle
quickly unless disturbed by moving air. The greatest concern is
that a particle deposits on the product causing contamination or
defect.
[0013] Particulate control is primarily achieved through airflow
design. In essence, filtered and conditioned air is passed through
the enclosed room space at a rate sufficient to sweep any
internally generated particles out of the space to be trapped in
external filters before contamination of the work product can
occur. This often requires that the total volume of cleanroom air
be changed many times per hour. The cleanroom industry specifies
the cleanliness of rooms by referring to class numbers. Federal
Standard 209E, "Airborne Particulate Cleanliness Classes in Clean
Rooms and Clean Zones", Sep. 11, 1992, categorizes clean rooms in
six general classes, depending on the particle count (particles per
cubic foot) and size in microns. These classes are listed in Table
I along with the typical number of room air changes per hour and
typical air flow rates required to sustain them.
TABLE-US-00001 TABLE I Cleanroom Classes Maximum allowable count
per Air Air cubic foot of air Changes Flow Room Particle size
(microns) per (cfm/ Class 0.1 0.2 0.3 0.5 5 Hour sq. ft.) 1 35 7.5
3 1 0 600 100 10 350 75 30 10 0 540 85 100 750 300 100 0 480 75
1,000 1,000 7 180 25 10,000 10,000 70 60 10 100,000 100,000 700 20
1
[0014] The air flow requirements shown in Table I have significant
implications on the amount of energy needed to operate a cleanroom.
In their paper "Cleanroom Energy Optimization Methods," presented
at the Fourteenth Symposium on Improving Building Systems in Hot
and Humid Climates held in Richardson, Tex. May 17-20, 2004,
authors Schrecengost and Naughton summarized several studies on
energy use in cleanrooms used in the semiconductor industry. They
reported that up to 42% of the total non-process related energy
consumption (i.e., not related to the operation of manufacturing
equipment within the cleanroom) was related to operation of the
recirculation fans required to maintain adequate air flow rates
through the cleanroom to establish the desired class of particulate
control. More than 50% of the total non-process related energy
consumption was related to operation of the air-conditioning
systems required to maintain the required temperature and humidity
levels of the cleanroom air supply. Although the large cleanrooms
used in semiconductor manufacturing operations are typically used
24 hours per day, 7 days per week, it is not uncommon for small and
mid-sized cleanrooms operated in other industries to be unused at
night and on weekends, although the cleanroom systems typically
remain in operation to prevent particulate contamination during the
off hours. Thus, a need exists for a cleanroom resource management
system to allow reduced energy consumption during evening and
weekend hours without compromising the environmental integrity of
the cleanroom space.
DISCLOSURE OF THE INVENTION
[0015] The present invention provides a system for managing
cleanroom resources by providing a number of critical features in
an integrated, low-cost package:
[0016] 1. monitoring and recording cleanroom environmental
conditions such as temperature, humidity and room differential
pressure,
[0017] 2. notifying users of alarm situations when cleanroom
environmental conditions either exceed or fall below predetermined
limits, and
[0018] 3. reducing cleanroom energy usage by turning off HEPA
filter fan units (FFUs) and cleanroom lights when they are not
needed.
[0019] In a separate embodiment, user notification can be provided
to a list of selected users via telephone or internet
communications.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 illustrates the two primary configurations for
achieving a unidirectional airflow type of cleanroom.
[0021] FIG. 2 is a diagram showing the primary electromechanical
systems used in a cleanroom.
[0022] FIG. 3 shows a typical cleanroom configuration using filter
fan units (FFUs).
[0023] FIG. 4 is a diagram showing a prior art monitoring and
control system.
[0024] FIG. 5 is a diagram depicting a typical prior art monitoring
and control system graphical user interface.
[0025] FIG. 6 shows airflow configurations for a fully powered and
partially powered cleanroom.
[0026] FIG. 7 is a diagram depicting an embodiment of the present
invention cleanroom monitoring and control system.
[0027] FIG. 8 is a diagram depicting an embodiment of the present
invention monitoring and control system graphical user
interface.
[0028] FIG. 9 is a diagram depicting an embodiment of the present
invention monitoring and control system graphical user interface
for multiple cleanrooms.
DETAILED DESCRIPTION
[0029] The features of the present invention are set forth in the
appended claims which may be best understood by reference to the
following description taken in conjunction with the accompanying
drawings.
[0030] Cleanrooms have evolved into two major types differentiated
by their method of ventilation: unidirectional airflow and
non-unidirectional airflow cleanrooms. Unidirectional airflow
cleanrooms are characterized by a design that attempts to maintain
airflow at a constant level throughout the cleanroom. In
non-unidirectional airflow cleanrooms, the airflow is constant only
over a limited work area within the cleanroom, and is allowed to
diminish elsewhere within the cleanroom. Unidirectional airflow
cleanrooms are generally required to achieve the lowest cleanroom
classes. FIG. 1 depicts the two basic configurations used to
achieve unidirectional airflow cleanrooms. FIG. 1A shows a
cleanroom 100 wherein conditioned air 101 is pressurized by a
single large fan 102 and is directed into the cleanroom through
contiguous HEPA filter units 103 resulting in a uniform airflow 104
throughout the cleanroom. In this example air exits the cleanroom
through a perforated floor 105 and is extracted 106 for
recirculation. FIG. 1B shows an alternate configuration using HEPA
filter fan units (FFUs) 107 wherein fans are incorporated within
the HEPA filter housings to partially pressurize the cleanroom.
FFUs also typically contain integrated diagnostic sensors that
provide feedback on their operating condition. FFUs are
advantageous in that they provide for greater flexibility in the
cleanroom configuration and require simpler housings than the
single fan, however they are not capable of providing the static
pressure levels that can be achieved using a single large fan. In
the past, FFUs were generally less efficient than the dedicated
single fan unit, but their popularity has stimulated significant
efficiency improvements. Reducing the energy consumption of the
single fan requires the use of an expensive, high power controller
module to reduce fan speed and the air flow within the cleanroom
remains uniform. However, smaller individual control units can be
applied to control individual FFUs, allowing selected units to
remain operating at full speed to protect critical work areas.
[0031] FIG. 2 is a diagram showing the primary electromechanical
systems used in a cleanroom wherein FFUs are employed to establish
a unidirectional airflow configuration. As in FIG. 1, supply air
101 is furnished to FFUs 107 which establish a unidirectional
airflow 104 within the clean room. Air is extracted through
openings in the floor 105 or sidewalls (not shown) and return air
106 is partially exhausted 204 outside the building using exhaust
fan 203 and partially recirculated 205 to HVAC unit #2 200 for
recirculation. Fresh air 202 from outside the building is
separately conditioned by HVAC #2 201 and combined with the
conditioned recirculated air. Optionally, separate fans in units
HVAC #1 201 and HVAC #2 200 can be employed to prepressurize the
supply air 101 in order to achieve the overall desired room
pressurization. Fresh air 202 is required to compensate for the
extract air 204 and the inevitable cleanroom leakage 206.
[0032] FIG. 3 shows a typical cleanroom configuration using FFUs.
Cleanroom 300 incorporates window units 301 for visibility and six
FFUs: FFU1 302, FFU2 303, FFU3 304, FFU4 305, FFU5 306 and FFU6
307. Supply air 101 enters the FFUs from the HVAC units and return
air is extracted either through the floor or the walls (not shown.)
The cleanroom also has three lighting units L1 308, L2 309 and L3
310. Subsequent discussion of cleanroom management systems will use
this configuration as an example.
[0033] FIG. 4 is a diagram showing a prior art monitoring and
control system. In this system, a personal computer (PC) 400
executes a monitor and control program that is used to receive and
display cleanroom environmental parameters from various sensors,
and to manually control the FFUs and room lights. Cleanroom
environmental sensors for temperature 401, humidity 402 and room
differential pressure 403 provide either analog or digital
electronic signals that are directed to the PC 400 on sensor bus
404. Diagnostic signals 405 from FFUs 302-307 are directed to the
PC 400 on FFU input bus 406. These sensor signals are monitored and
displayed by the program executing on PC400 and audible and visible
warning messages are displayed if the environmental parameters or
FFU operational parameters exceed or fall below preprogrammed
limits. Lighting control signals 408 are applied through the
lighting output bus 407 to control digital switches 410 that
connect power lines 409 to cleanroom lights 308-310 to the power
mains 411. The speed of each of the FFU fans is controlled by FFU
control signals 413 on the FFU output bus 412 that connect FFU
power lines 415 to variable frequency motor drives 414. Lighting
control and FFU speed control are effected by inputs to the program
executing on PC 400.
[0034] FIG. 5 is a diagram depicting a typical prior art monitoring
and control system graphical user interface (GUI) 500 as would be
displayed continuously during cleanroom operation on PC 400 in FIG.
4. Multiple users who have been trained and qualified to manage
cleanroom operations login to the program using preestablished
usernames 501 and passwords 502. Cleanroom environmental conditions
corresponding to temperature 503, humidity 504 and differential
pressure 505 are shown on the graphic displays in the center of the
GUI. Optionally, upper and lower setpoints can be entered for each
of these quantities through pop-up menus accessed by clicking on an
icon and audible and visible alarms triggered if operating
conditions drift out of range. The status of each of the FFUs is
shown in the graphic displays 506-511 at the left. Each of the FFU
displays shows the unit number 512 and a status description
(Normal, Off or Alarm) 513 as well as the current set point 514 and
indicators for power 515 and alarm condition 516. All of the
cleanroom parameter values in displays 503-511 are recorded with a
time stamp on the PC 400 hard drive at predetermined intervals.
Also displayed on the GUI are a scrolling history of alarm
conditions 517 and a related action log 518 that provides
traceability for actions associated with the alarm history 517.
[0035] Although the system depicted in FIGS. 4 and 5 functions
adequately in managing cleanroom resources, it exhibits several
deficiencies that are addressed by the present invention. In one
aspect, the variable frequency motor drive units 414 used to adjust
FFU fan speeds are expensive and represent a potential reliability
risk. It is much more economical and reliable to employ simple
digitally controlled electrical switches to shut off selected FFUs.
FIG. 6A shows a cross section of the example cleanroom 300 shown in
FIG. 3 wherein all FFUs 302-307 are powered resulting in the
desired unidirectional airflow configuration 104 supported during
work hours. FIG. 6B illustrates the airflow configuration 600 that
results when the outside FFUs 302, 303 and 306, 307 are powered
off. The airflow configuration is now non-unidirectional, which
would be unacceptable during normal working hours, but may be
adequate during off hours, particularly if any work-in-progress
(WIP) 601 stored within the cleanroom is located beneath the active
FFUs 304, 305.
[0036] FIG. 7 is a diagram showing an embodiment of the present
cleanroom monitoring and control system. As in the system of FIG.
4, a personal computer (PC) 400 executes a monitor and control
program that is used to receive and display cleanroom environmental
parameters from various sensors, and to control the FFUs and room
lights. Cleanroom environmental sensors for temperature 401,
humidity 402 and room differential pressure 403 are complemented
with an optional particle counter 701 and each provide either
analog or digital electronic signals that are directed to the PC
400 on sensor bus 404. Diagnostic signals 405 from FFUs 302-307 are
directed to the PC 400 on FFU input bus 406. These sensor signals
are monitored and displayed by the program executing on the PC 400
and audible and visible warning messages are displayed if the
environmental parameters or FFU operational parameters exceed or
fall below preprogrammed limits. In this embodiment, PC 400 is
connected to the Internet 702 through a firewall 703 thereby
allowing warning messages to be communicated to a predetermined
list of recipients using telephone messaging, text messaging or
e-mail messaging. Lighting control signals 408 are applied through
the lighting output control line 407 to control digital switches
410 that connect power lines 409 to cleanroom lights 308, 310 to
the power mains 411. Note that cleanroom light 309 is hardwired to
be powered at all times. The FFU fans for FFUs 302, 303 and 306,
307 are controlled by FFU control signals 413 on the FFU output
control line 412 that connect FFU power lines 415 to digital
switches 410. Note that FFUs 304, 305 are hardwired to be powered
at all times. Lighting and FFU power control are effected by inputs
to the program executing on PC 400.
[0037] FIG. 8 is a diagram depicting an embodiment of the present
monitoring and control system graphical user interface (GUI) 800 as
would be displayed continuously during cleanroom operation on PC
400 in FIG. 7. As in FIG. 5, multiple users who have been trained
and qualified to manage cleanroom operations login to the program
using preestablished usernames 501 and passwords 502, and cleanroom
environmental conditions corresponding to temperature 503, humidity
504 and differential pressure 505 are displayed. Optionally, upper
and lower setpoints can be entered for each of the environmental
quantities through pop-up menus accessed by clicking on an icon and
audible, visible, and, optionally, electronic messaging alarms
triggered if operating conditions drift out of range. The
preprogrammed alarm threshold values for the room condition sensors
are also displayed 809. Since the FFUs are not individually
programmed, individual FFU icons are not needed. All of the
cleanroom parameter values in displays 503-505 and 809 are recorded
with a time stamp on the PC 400 hard drive at predetermined
intervals. The status of the Energy Saver feature 801 appears in
the center of the GUI which powers off the designated FFUs 302, 303
and 306, 307 and the designated cleanroom lights 308, 310 according
to the schedule 802. Schedule parameters 802 can be set by clicking
button 803. The Energy Saver mode can be enabled and disabled by
clicking button 804. The present state of the Energy Saver feature
is indicated by the position of icon 805 either over the "100% On"
or over the "Saving Energy" schedule segments. Also displayed on
the GUI is a scrolling action log 518 that provides traceability
for actions associated with the Energy Saver settings 801.
[0038] In many instances, a manufacturing facility may comprise a
number of separate mini-cleanroom units for individual specific
manufacturing processes, each requiring independent control and
monitoring of its environmental conditions. FIG. 9 shows a GUI 900
for an alternate embodiment of the present monitoring and control
system wherein the sensor bus 404 shown previously in FIG. 7
directs sensor signals from multiple rooms to the controlling PC
400. Although all of the sensor signals are continuously monitored
by the program executing on the PC 400, the GUI 900 displays the
room conditions 901 and alarm thresholds 902 for one specific room
selected by means of a Room Selector submenu 903 on the GUI.
[0039] In a further embodiment of the monitoring and control system
(not shown) the monitoring and control program executing on PC 400
and the GUI 900 include the means for controlling and displaying
the status of the Energy Saver Mode for the selected room.
[0040] The present invention has been described in terms of the
preferred embodiment and it is recognized that equivalents,
alternatives and modifications, beyond those expressly stated, are
possible and are within the scope of the attached claims.
* * * * *