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ISO 14644-1 Cleanroom Classifications

Cleanroom for Microelectronic Manufacturing

A question commonly asked is "What is a clean room?" Generally speaking a "clean room" is an enclosed room that has equipment which controls the amount of particulate matter in the air by using air pressure and filters. To meet requirements of a "clean room" as defined by Federal Standard 209E and newer ISO Standards, all clean rooms must not exceed a particulate count as specified in the air cleanliness class.

As of November 29th, 2001, the Federal Standard 209E has been replaced with ISO 14644-1. This method is simple; the number assigned to the class is the classification that the room must be designed to. In the Fed. Standard 209E, Class 1 was the cleanest. In the new ISO 14644-1 Standard, Class 3 is the cleanest. The difference? Generally speaking, the federal standards were measured in cubic feet and the ISO standards are measured in cubic meters.

What is measured in the air? Class 3, 4, and 5 are based on the maximum number of 0.1 and 0.5 micron particles that are permitted in a cubic foot of air approaching any work operation within the room. Class 6, 7, and 8 are based on the number 0.5 micron particles.

What is a micron? To give you an idea of what is being measured, one micron is one-hundredth the width of a human hair. The smallest particle seen with the naked eye is a 10 micron particle. Clean rooms can control 0.01 and 0.05 particles!

Where do these particles come from? The clean room is under positive pressure, keeping out new particles from coming in. So where do they come from? Micro-organisms come from people in the room and other particulates from the processes in the room. Microbes come from skin cells of humans. We shed our outermost layer of skin every 24 hours, that is 1 billion flakes every 24 hours! One flake is about 35 microns.

What are the clean room classifications? The ISO 14644-1 has changed these numbers to simple classes:

ISO 14644-1 Cleanroom Standards
Classification Maximum Particles/m3 FED STD 209E Equivalent
≥0.1µm ≥0.2µm ≥0.3µm ≥0.5µm ≥1µm ≥5µm
ISO 1 10 2.37 1.02 0.35 0.083 0.0029
ISO 2 100 23.7 10.2 3.5 0.83 0.029
ISO 3 1,000 237 102 35 8.3 0.029 Class 1
ISO 4 10,000 2,370 1,020 352 83 2.9 Class 10
ISO 5 100,000 23,700 10,200 3,520 832 29 Class 100
ISO 6 1.0 x 10 237,000 102,000 35,200 8,320 293 Class 1,000
ISO 7 1.0 x 107 2.37 x 106 1,020,000 352,000 83,200 2,930 Class 10,000
ISO 8 1.0 x 108 2.37 x 107 1.02 x 107 3,520,000 832,000 29,300 Class 100,000
ISO 9 1.0 x 106 2.37 x 108 1.02 x 108 35,200,000 8,320,000 293,000 Room Air

The now defunct Federal Standard 209E classifications are as follows:

US FED Standard 209E Cleanroom Standards
Classification Maximum Particles/ft3 ISO 14644-1 Equivalent
≥0.1µm ≥0.2µm ≥0.3µm ≥0.5µm ≥5µm
1 35 7.5 3 1 0.007 ISO 3
10 350 75 30 10 0.07 ISO 4
100 3,500 750 300 100 0.7 ISO 5
1,000 35,000 7,500 3,000 1,000 7 ISO 6
10,000 350,000 75,000 30,000 10,000 70 ISO 7
100,000 3.5 x 106 750,000 300,000 100,000 700 ISO 8
US Fed. Standard 209E was officially cancelled by the General Services Administration of the US Dept. of Commerce November 29, 2001, but is still widely used.

The British Standard BS5295 Classifications are:

BS 5295 Cleanroom Standards
Classification ≥0.5µm ≥1µm ≥5µm ≥10µm ≥25µm
Class 1 3,000 0 0 0
Class 2 300,000 2,000 30
Class 3 1,000,000 20,000 4,000 300
Class 4 200,000 40,000 4,000
BS 5295 Class 1 also requires that the greatest particle present in any sample does not exceed 5µm.

The GMP EU Classifications are:

GMP EU Classification
Classification Maximum Particles/m3
At Rest In Operation
0.5µm 5µm 0.5µm 5µm
Class A 3,520 20 3,500 20
Class B 3,520 29 352,000 2,900
Class C 352,000 2,900 3,520,000 29,000
Class D 3,520,000 29,000

Air Quality: A properly designed clean room must have a high rate of air changes to scrub the room of particulates. A Class 5 room can have an air change rate of 400 to 600 times per hour while a class 7 room can change at 50 to 60 changes per hour.

Testing and Certification: Once the room is completed, most specifications call for testing and certification. Some requirements state that the room should be tested annually also. Testing is usually conducted by an independent testing agency using the ISO Standards. It is also imperative for the owner to purchase a clean room monitor in order to determine the daily status of the room.

CleanPro® offers all types of cleanrooms, including mobile options along with monitoring, furniture and garments. Everything you need to start, maintain, or expand an existing cleanroom. Contact us anytime at [email protected] and let our clean room experts help you find what you need.

©Jenn Weesies. Feb. 25, 2010