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August 1997

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Subject:
From:
"Leslie O. Connally" <[log in to unmask]>
Reply To:
Leslie O. Connally
Date:
Tue, 12 Aug 1997 11:31:29 -0700
Content-Type:
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text/plain (73 lines)
Hi Ed,

        I'm not sure where from, but the name is familar from somplace, perhaps
IPC. At TI austin we have had a class 100K clean room for a long time. It has
been certifiedin the past. The major item in the certification is that no more
than 100,000 particles less than 5 microns are detected with a particle
counter.
We measure this periodically and find that the room would pass for a class
10,000. This area produces 4 to 5 mil lines/spaces routinely. We find that the
disciplines in maintaining the clean room are more important than the particle
count. Anumber of years ago we had a class 100 clean room in Dallas where we
were making some specialized hi-density circuit boards. Looking back I believe
that the class 100 room was overkill. Initially some major problems were
overlooked. The lack of a good clean up of the room, wiping down of the
equipment to remove resist particles, not carring in resist boxes, and other
paper materials created some problems. We developed a clean up criteria of the
room and implemented it at the beginning of the shift, which probably did much
to improve the reliability of doing fine line circuitry than anything else.
I am a firm believer in the implementation of clean room practices and as you
progress into the fine line technology, I think it is a must, a class 10,000
room would be nice, and your product must lead you, However, a well controlled
class 100k room should suffice for most products down to about 4 mils l/s.
Remember it's not the 5 micron particles that Kill you, it's the resist chips,
fibers, paper, etc. of larger size that are the major problems.

Good Luck.

Les Connally

 [log in to unmask]

>  From: Ed Cosper <[log in to unmask]>, on 8/11/97 3:48 PM:
>  I am having some serious discussions regarding the planning of a new Photo
>  print area. Our current print area is not really a true "clean room"
>  environment. Basically we have positive air flow, tacky floor mats at the
>  entries,  and use the smocks and hair nets. Many board shops I've seen
>  operate in a similar fashion. However,  I would like to know how many bare
>  board manufactures really have a true certified clean room. I know of a few
>  shops that advertise they do but they have never had their rooms certified
>  and from my experience, I doubt they would pass a test.  The problem is that
>  I want to look at putting in a true class 100K clean room but I am meeting
>  resistance. Basically, it is felt by many here that no board shop really has
>  a true clean room and the cost associated with one does not justify the
>  implementation. Because I have personally seen this to be the case and have
>  never actually seen a true clean room in a board shop, I am having
>  difficulty disagreeing.
>
>  As I understand it,  a true class 100k clean room has to be certified by an
>  outside source. In addition all incoming air has be deionized. There should
>  be no flat surfaces and absolute no paper for fiber products.  So I have a
>  few questions I would like to pose to Technet.
>
>  1. Does anyone know of a bare board manufacture that has a true class 100K
>  clean
>      room where I can obtain some additional information?
>
>  2.  Does anyone feel a true clean room is really warranted for a board
>  manufacture that
>       currently producing lines down to only .005" ?
>
>  3. Does anyone have any data from studies performed in a bare board
>  manufacturing
>      environment that would support the need for a true clean room and would
>  you be willing
>      to share the information?
>
>  Any and all help in this matter will be appreciated.
>
>  Ed Cosper
>
>


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