Increasing product quality by particle deposition control. Monitoring large particles in controlled environments.

1. Increasing product
quality by particle
deposition control
Koos Agricola
BrookhuisAplliedDataIntelligence

2. Content
Vulnerable products
Contamination mechanisms
Contamination control
Cleanroom
Cleanroom operation
Product contamination risk
Particle deposition rate
Relation between air cleanliness and particle deposition rate
Particle deposition monitoring with the APMON

3. Vulnerable products and treatments
Products or treatments can loose the quality of their
function(s) and/or can harm the user by contamination
These product are found in various industries:
electronics, semiconductors
technical products
(aero)space industry
automotive industry
medical products
pharma, biopharma
healthcare, hospitals
food
cosmetics

4. Contamination mechanisms
The cause of harm is unwanted surface contamination by particles and/or
micro-organisms of critical surfaces during exposure
Important factors are:
The area of the critical surface
The time of exposure
The air cleanliness of the environment
The particle deposition rate during exposure
The surface cleanliness of contact surfaces
The contact area and number of contacts

5. Contamination mechanisms
The air cleanliness determines the particle deposition rate
The particle deposition rate is the deposition of particles larger or equal than the
particle size of interest expressed in number per area (dm2 or m2) per hour.
Particle deposition is driven by sedimentation and air movement (turbulences)
The particle deposition rate is equal to the concentration of particles (N/m3)
times the deposition velocity (m/hr)

6. Contamination control
All measures to limit the particle deposition rate
Limit exposure
Clean controlled environment (cleanroom or clean zone)
Separated space with overpressure (limit introduction of particles)
Controlled transfer into cleanroom via air locks (limit introduction of particles)
Ventilation by filtered air (removal of airborne particles)
• Dilution (non-unidirectional airflow)
• Displacement (unidirectional air flow)
Cleaning (removal of surface particles)
Prevent contact with unclean surfaces (do not contact critical surfaces)

7. Cleanroom
Segregation
Physical
• Box in box (low emitting construction materials)
• Air locks
• Rooms and zones with different air cleanliness levels
By HEPA/ULPA filtered air flow
• Overpressure
• Air flow direction by pressure control
Ventilation (air volume rate, (non-)unidirectional)
Cleaning
All surfaces easy to clean

8. Ventilation concepts
Unidirectional
Vertical
• with raised perforated floor or low wall returns
Horizontal with perforated opposite wall
Air change rate 100 – 600 per hour
Non unidirectional
Vertical from 0.4 to 1.4 m2 terminal filters
• smaller units sometimes used of air diffusers
• raised perforated floor or low wall returns
Air change rate 5 – 100 per hour

9. Separative devices
Separated space that can not be accessed by a person
Open
Ventilation by vertical/horizontal unidirectional airflow (laminar airflow cabinet)
Safety cabinet with exhaust
Closed
Loading by transfer interface
Access by fixed gloves or half suit with gloves
Manipulation by robotic systems

10. Cleanroom operation
Access by personnel Introduction of particles and micro-organisms
Goods transfer Introduction of particles and micro-organisms
Logistics Distribution of particles and micro-organisms
Working methods Introduction and distribution of particles and micro-organisms
Operating equipment Introduction of particles and micro-organisms
Cleaning Removal of particles and micro-organisms
Cleanroom surfaces
Tools and equipment
Product surfaces

11. particle deposition
Source
Product
Clean air
Removal of
airborne
particles
Cleanroom operation causes

12. Product contamination risk
Product contamination risk depends on severity and likelihood of contamination
Product surfaces are contaminated by particle deposition
Particles can carry micro-organisms
Product surface can also be contaminated by contact transfer
Contact surfaces are contaminated by particle deposition
Surface contamination can be removed by cleaning
Product cleaning can damage product surfaces
Product contamination is determined by particle deposition rate or
microbial deposition rate, product area and time of exposure

13. Product contamination risk
Risk Assessment
What can harm the functions of product?
Critical surfaces and critical particle sizes
Location(s) critical surface is exposed
Acceptable final surface cleanliness
Initial surface cleanliness
Acceptable particle contamination during exposure
Contamination mechanisms are particle deposition and
contact transfer from unclean surfaces

14. Product contamination risk
Risk assessment
Risk = probability x severity of consequences
Severity increases with particle size
Probability of particle contamination =
Particle deposition rate PDR x product area x time of exposure
PDR limit determines air cleanliness

15. Microbe carrying particles (MCP’s)
Micro-organisms are mostly carried by particles.
The number of micro-organisms (in colony
forming units) is a fraction m of all particles.
m depends on particle size D and cleanroom class.
Average MCP size: d = 12 µm or D = 20 µm
Most micro-organisms are dispersed by personnel,
therefore in ISO 5 m is higher than in ISO 8, although the total number
of particles and micro-organisms is lower.
MDR = m.PDR
0,0
0,2
0,4
0,6
0,8
1,0
0 20 40 60 80 100 120 140 160 180 200
m
Particlesizeinµm
Estimated of value m,
ratio microbial and particle deposition
ISO 8
ISO 7
ISO 6
ISO 5

16. Particle deposition rate
Particle deposition rate depends on air cleanliness
Particle deposition rate depends on particle size
Air cleanliness depends on operation:
Introduction of particles by sources
• Personnel
• Goods
• Equipment
Distribution of particles
Re-entry of particles
• Reduced by cleaning
Resulting air cleanliness depends on ventilation system

17. Relation between air cleanliness and
particle deposition rate
The supply of cleanroom air determines the air cleanliness by dilution of
the total number particles introduced in the air per time and the ventilation efficiency
𝐶 =
𝑆
ε𝑄
where C is the number of particles per m3
S is number of emission of particles per second
ε is ventilation effciency
Q supply volume rate m3/s
The removal efficiency is related to the air change rate of the supplied air and the
ventilation efficiency: ε.Q/room volume = ε.air change rate = ε.acr

18. Cleanroom qualification
Cleanroom class determines the maximum
concentration of the worst location in the
cleanroom
Room area determines measurement locations
Selected particle size determines limit
concentration and minimum sample volume
State of occupancy
Cleanroom monitoring is the frequent
measurement of the air cleanliness at a critical
location
Recovery rate is determined by the removal
efficiency and thus by: ε.acr
ISO class Particles
≥ 0.5 µm/m3
Particles
≥ 5 µm/m3
9 35,200,000 293,000
8 3,520,000 29,300
7 352,000 2,930
6.5 111,000 953
6 35,200 293
5.5 11,100 (95)
5 3,520 (29)
Most used part of classification table

19. ISO 14644-1 classification table
Table for classification of air clealiness by particle concentration
0,1 µm 0,2 µm 0,3 µm 0,5 µm 1 µm 5 µm
1 10
2 100 24 10
3 1,000 237 102 35
4 10,000 2,370 1,020 352 83
5 100,000 23,700 10,200 3,520 832
6 1,000,000 237,000 102,000 35,200 8,320 293
7 352,000 83,200 2,930
8 3,520,000 832,000 29,300
9 35,200,000 8,320,000 293,000
ISO Class
number (N)
Maximum allowable concentrations (particles/m3
) for particles equal to and
greater than the considered sizes, shown below:
Sample collection limitations for both particles in low concentrations and sizes > 1 um make classification at
this particle size inapprpopriate, due to potetial losses in the sampling system.
Sampling and statistical limitations for particles in low concentrations make classification inappropriate.

20. State of occupancy
As build: empty cleanroom.
At rest: with equipment, no people.
Operational: with people, result depends
on balance between source strength and
supplied clean air.
The concentration of particles ≥ 5 µm is
almost zero “at rest” but high in
“operational”.

21. Removal efficiency by air flow
Airborne particles can be removed by air flow.
Larger particles will deposit on all surfaces.
Deposition velocity depends on Stokes law.
Deposited particles must be removed by cleaning.
In non unidirectional ventilation:
The removal efficiency depends on the particles size and the air change rate;
The air cleanliness depends on the total sources strength and the air supply
volume and removal efficiency.
In unidirectional air flow the removal efficiency depends on the air
velocity and the unidirectionality.

22. Particle removal from cleanroom
by airflow and deposition

23. Particle removal from cleanroom
by airflow and deposition

24. Emission of particles by a person in a cleanroom

25. Resulting air cleanliness during operation
In operation personnel causes increase of
particle concentration.
Particle size distribution changes from at rest
to operational occupancy state.

26. Air cleanliness
Number of particles per m3 air is function of particle size:
In at rest situation:
the number of particles is determined by the quality of the cleanroom installation
the number of particles is proportional to the square of the particle size (d2)
In operation:
the number of particles is determined by the number of personnel
the local number of particles varies with the location and activity of personnel
the number of particles is proportional to the particle size (d)
The removal efficiency of the cleanroom installation decreases rapidly with particle size (>5µm).
Particles that are not removed deposit on all surfaces.
Surface particle can become airborne under influence of turbulent airflow.

27. Particle deposition rate
PDR determines likelihood of contamination
Direct
Indirect via contact surfaces
PDR depends on:
Contamination sources
Cleanroom installation
Cleaning

28. Monitoring air cleanliness at a critical location
Monitor particle concentration regularly at critical locations during operation
ISO 14644-2:2015
Determine critical locations by risk assessment
Make a monitoring plan
Set measurement time and frequency
Critical locations
Particle sizes of interest
Set action and alert levels
Real time measurement shows the impact of activities by personnel

29. Particle deposition rate PDR
PDR is number of particles per area per hour
Number of particles ≥ D µm per m2 per hour
ISO 14644-17:2020 Particle deposition rate applications
ISO 14644- 3:2019 Measurement methods

30. Relation between particle deposition rate and air
cleanliness for particles between 5 and 50 µm
Hamberg relation: C5 = PDR5
1.294/295
PDRL1 = 10.PDRLISO per m2/hr In APMON PDR = PRDL1 per dm2/hr
PDC = 10log PDRL1 per m2/hr
Particle concentration
PDRLISO
N10/m2
/hr
PDC (VCCN)
N1/m2
/hr
PDR
N1/dm2
/hr
PDR5
/m2
/hr
PDR50
/m2
/hr
C5 ISO level
1 1 0.1 2 0.2 0.008 1.5
10 2 1 20 2 0.16 2.7
100 3 10 200 20 3.2 4.0
1,000 4 100 2,000 200 63 5.3
10,000 5 1,000 20,000 2,000 1,247 6.6
100,000 6 10,000 200,000 20,000 24,531 7.9
1,000,000 2,000,000 200,000 482,737 9.2
Particle deposition rate level

31. Relation between particle deposition rate and air
cleanliness for particles between 5 and 50 µm
A cleanroom is used to control and
limit the particle deposition during
operation.
Relation between airborne particles <
5 µm is not very clear since most
particles do not deposit and are
removed by air flow.
For particles ≥ 5 µm (D= d= 5 µm)
Hamberg found a relation between air
cleanliness C5 and particle deposition
rate PDR5:
PDR5 = 81.2* C5
0.773 per m2 per hour

32. Relation between particle deposition rate and air
cleanliness for particles between 5 and 50 µm

33. Particle deposition monitoring with the APMON
Advanced Particle deposition MONitor
Particle deposition rate can be measured using a witness plates plus microscopic
inspection (time and labour consuming)
Particle deposition can be measured real time using one or more APMON sensors

35. APMON data
The APMON counts every set sampling period the number of
deposited particle, their size and cross section area.
From this data the following information can be derived:
Deposition event screen
Differential and cumulative particle size distribution Screen
Coverage event screen and total area coverage
Particle Deposition Rate, Class or Level
Particle Obscuration Rate
The real-time screens will create operator awareness.
The data in the screen s can be exported in a .csv file

36. APMON screens
real time deposition of particles > 15 µm

37. APMON screens: Particle area coverage

38. APMON screens (2 sensors)
real time deposition of particles > 15 µm

39. Differential Particle Size Distribution
Brookhuis ADI Cleanroom 39

40. Differential particle size distribution and area coverage

41. Cumulative Particle Distribution

42. Particle deposition rate graph

43. Cumulative particle size distribution
< 30 µm: impact of cleanroom installation
30-100 µm: impact of people and logistics:
Number of people
Garments and changing procedures
Discipline and working methods
Transfer of goods
> 100 µm: impact cleaning program:
Cleaning of large surfaces by cleaners
Cleaning of workplaces tools and equipment by operators
Cleaning of incoming goods

44. Important ISO standards
ISO 14644-2:2015 Monitoring to provide evidence of cleanroom performance
related to air cleanliness by particle concentration
ISO 14644-3:2019 Test methods (including Particle deposition test)
ISO 14644-9:2012 Classification of surface cleanliness with respect to particle
concentration
ISO 14644-13:2017 Cleaning of surfaces to achieve defined levels of cleanliness
in terms of particle and chemical classifications
ISO 14644-17:DIS2019 Particle deposition rate applications
EN17141:2019 Biocontamination

45. Particle deposition rate level
PDRL = PDR.D
where PDR is the particle deposition rate of particles ≥ D µm /m2/hr
PDR = C.u
where C is the particle concentration and u is the deposition velocity
PDR = ΔCS / T
where ΔCS = CS – CS initial and T is the time of exposure

46. Product contamination risk
Product are contaminated by deposition
ND = PDRL * A * T / D
where ND is the expected number of particles ≥ D µm
A is the product area
Products can also be contaminated by contact transfer
ND = n * δ * Acontact * CS = n * δ * Acontact * PDR * T
where n is the number of contacts, δ is the transfer efficiency
Acontact is the contact area
ND = PDRL * A * T * (1 + n * δ) / D where D is the critical particle size

47. APMON 100
Travel case
Mini-pc with i5 processor
APMON Sensor (no battery, no Bluetooth)
1 Witness cartridge
USB with User guide
Optional
Extra Witness cartridge(s)
LCD screen mouse and keyboard
Brookhuis ADI Cleanroom 47

48. APMON 200
As APMON 100 +
APMON Sensor (with battery and Bluetooth)
2 battery’s and
battery charger (for 3 battery’s)
Optional
2nd APMON sensor (with travel case, battery and Bluetooth and witness
cartridge)
Extra Witness cartridge(s)
LCD screen mouse and keyboard
Witness cartridge exchange program refurbished (per 4 pieces)
Brookhuis ADI Cleanroom 48

49. APMON PRO
Travel case
Base computer with i7 processor and battery charger (for 3 battery’s)
APMON sensor (with travel case, battery and Bluetooth and witness cartridge)
2 Witness cartridge
2 battery’s
USB with User guide
Optional
Extra Witness cartridge(s)
Extra APMON sensors (with travel case, battery and Bluetooth and witness cartridge)
LCD screen mouse and keyboard
Witness cartridge exchange program refurbished (per 4 pieces)
Brookhuis ADI Cleanroom 49

50. Use of particle deposition data
To set limits based cleanliness requirements
Contamination control solution is a combination of clean zones
(from cleanroom to separate devices)
Operational procedures
Monitor performance of cleanroom installation
Balance between particle sources and ventilation
Monitor performance of operational procedures
Transfer of particles into cleanroom
Generation of particles in the cleanroom
Distribution of particles in the cleanroom
Removal of particles by cleaning

51. Aspects that influence particle deposition rate
Particle deposition rate impacts the product contamination risk.
Particle deposition rate data provides guidance to the improvement of operational quality.
Critical aspects and activities are:
Transfer
Preparation
Cleaning
Behaviour
Awareness of personnel
Garment selection
Entry and exit procedures and working methods

52. Applications
Aerospace industry
Automotive industry
Inkjet printheads
Electronics
Optics
Displays
Semiconductor equipment
Medical devices
Hospitals

53. Thank you for
your attention
a g r i c o l a @ b r o o k h u i s . c o m
https://www.brookhuis.com/cleanroom