IC ISO Cleanroom Classification - ISO Class 7 (10k), ISO Class 8 (100K), ISO Class 9

C

celon

#1
Is there an existing study or detailed recommendation on what cleanroom classification is desirable or sufficient for a specific field of application? We're a semiconductor test facility. We test IC's (electrical and mechanical) of various package configurations, we also test wafers. Our wafer test facility is currently an ISO class 7 (10k) cleanroom. Our Test facility for packaged IC's is ISO Class 8(100K). This is the way it is since 10 years ago (though previously, classification was of FED 209). I am looking for specific risks to product quality or process operation should my facility cleanliness go beyond classification limits. Wouldn't ISO class 8 be sufficient for wafer testing? or ISO Class 9 for packaged IC testing? :confused:
 

jeffrey_Chang

Inactive Registered Visitor
#2
Re: IC ISO Cleanroom Classification - ISO Class 7 (10k), ISO Class 8 (100K), ISO Clas

The classification of air cleanliness is very simple as the class equates to the number of particles per cubic foot of air equal to or greater than 0.5µ (micron). I have attached a simple matrix that details the particles per cubic foot of air with particle size from 0.1µ to 5µ for class 1 to 100K.

In the microelectronics industry, we are concern with static as well as contaminations caused by particles, fibers and electrostatic charges where it will cause malfunction of the product.

A clean room can be divided into critical and general area. The critical area near the point of production where contamination can cause direct contact with the process and products. The critical area will often need to be protected by localised laminar flow.
The general area is the rest of the clean room where contamination will not have direct contact to the products but should be kept clean because of the transfer of contamination into the critical area.

My company also provides modules and wafer testing services to the industry. The clean room class we have for modules testing is at 100K 0.5µ and wafer test is set to class 10K 0.5µ but for wafer test, there are some specific requirements from our customer where they required the area surrounding the probers, transfer tools and scanners to be at class 1K 0.5µ. Note the critical and general area mentioned above to serve as a guideline.

The clean room class to follow will depend very much on the code of practise in your company as well as the product or services requirements.

thks.
jeffrey. :)
 

Attachments

C

celon

#3
Re: IC ISO Cleanroom Classification - ISO Class 7 (10k), ISO Class 8 (100K), ISO Clas

thanks Jeff, i've been browsing for industry practices and came across these IEST RP's... i'll try if we could purchase the docs so that I could have some baseline
 

gereard_kgb

Inactive Registered Visitor
#4
Re: IC ISO Cleanroom Classification - ISO Class 7 (10k), ISO Class 8 (100K), ISO Clas

Jerrey,
On thing:
the classification is based on particles content in cubic FOOT or METERS???

I was sure this were meter...

The matrix you supplier - is there any standard that it is based on or this is rather general approach?

:bonk:
 

Ajit Basrur

Staff member
Admin
#5
Re: IC ISO Cleanroom Classification - ISO Class 7 (10k), ISO Class 8 (100K), ISO Clas

Jerrey,
On thing:
the classification is based on particles content in cubic FOOT or METERS???

I was sure this were meter...

The matrix you supplier - is there any standard that it is based on or this is rather general approach?

:bonk:
Hi Gereard,

Classification can be done based on both cubic feet and cubic meters. Refer the attachment, where I have pasted the values for both.
 

Attachments

gereard_kgb

Inactive Registered Visitor
#6
Re: IC ISO Cleanroom Classification - ISO Class 7 (10k), ISO Class 8 (100K), ISO Clas

Thanks Qualityalways,
You're details as usually.

I checked EN ISO 14644-1 standard and counted cubic meters for cubic feet - now everything seams to be adding up...
:)

:D
 
E

Eric York - 2010

#7
Re: IC ISO Cleanroom Classification - ISO Class 7 (10k), ISO Class 8 (100K), ISO Clas

Celon,
I'm not a packaging expert so this response is more anecdotal in nature than anything else. Your cleanroom classes are in line with what I have seen at sites both within my company and at several assy/test subcontractors. A couple of risks (although I do not know what the real probabilities are...) are enough "gunk" collecting in the bond pads to prevent good bonds, and shorts between bond pads. It seems to me that if you are assembling products with very small, closely spaced pads, class 100k at wafer test could be asking for trouble.

Also, in my experience, a real problem that can arise with class 10k or class 100k cleanrooms is a lack of adherence to protocol by the personnel. This can create a much greater risk to product that is not formally tied to whether the cleanroom conforms to it's particle spec, but it seems to occasionally arise nevertheless.

Eric
 

Ajit Basrur

Staff member
Admin
#8
Re: IC ISO Cleanroom Classification - ISO Class 7 (10k), ISO Class 8 (100K), ISO Clas

Thanks Qualityalways,
You're details as usually.

I checked EN ISO 14644-1 standard and counted cubic meters for cubic feet - now everything seams to be adding up...
:)

:D
My pleasure ;)

Cleanrooms and related topics are my favourite and I enjoy writing on it.
 

jeffrey_Chang

Inactive Registered Visitor
#9
Re: IC ISO Cleanroom Classification - ISO Class 7 (10k), ISO Class 8 (100K), ISO Clas

Jerrey,
On thing:
the classification is based on particles content in cubic FOOT or METERS???

I was sure this were meter...

The matrix you supplier - is there any standard that it is based on or this is rather general approach?

:bonk:
Hi Gereard,
Cubic foot is used by the US under their Fed Stds 209.
Cubic meters is used by the British under their BS 5295.
You can used either cubic foot or cubic meters depending on the standard you choose to follow.
Fed Std 209 uses Class 100K to Class 100.
BS 5295 uses Class 1 to 4.
But both are equivalent.
We based our class on Fed Std 209.
thks.
jeffrey.:)
 

gereard_kgb

Inactive Registered Visitor
#10
Re: IC ISO Cleanroom Classification - ISO Class 7 (10k), ISO Class 8 (100K), ISO Clas

Jeffrey, thank you very much for your additional comments.

:2cents:
And EN ISO 14644-1 presents the same issue in a bit different way. It divides clean-rooms into classes 1-9.
And for example ISO class 8 should be equivalent to 100K as the limit for 0,5 micrometer particles is 3 520 000 per cubic meter. 1 cubic meter = ca 35,315 cubic foot. In this case all adds up.

The lower class the stricter the requirements are.

It is yet worth noting that the above mentioned standard indicates also the limits for particles of other sizes and they also need to be taken into account.
 

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