Guys

Thanks for your inputs on this matter. The problem with the screw head scrabing against the PCB surface should be avioded if there is a protective layer that can be damaged.
Our PCB's are often placed in a very volatile environment - at sea, where the risk of corrosion is high. Therefore cupper should not be left unprotected on these - and all other boards for that matter.
If the screw head rests on a non cupper surface - directly on the PCB glass fiber a washer is not needed.

Torben

-----Original Message-----
From: Crepeau, Phil [mailto:[log in to unmask]] 
Sent: 5. december 2003 02:03
To: [log in to unmask]
Subject: Re: [TN] Taptite and washers


hi,

ipc 610 covers all fasteners in the sense that you use whatever the drawing tells you to use.  about the only thing it's specific about is that a flat washer needs to be against the laminate that is exposed to a rotating surface on the fastener to prevent the laminate from being damaged.  i imagine that the minimum no. of threads that extend beyond the 'tapped' surface could still be used.

phil

-----Original Message-----
From: Torben S. Taustrup [mailto:[log in to unmask]]
Sent: Wednesday, December 03, 2003 1:28 AM
To: [log in to unmask]
Subject: [TN] Taptite and washers


Our company has adapted the IPC-A-610C standard. We often use self tapping screws like taptites when mounting PCB's in boxes. In the above mentioned standard this type of screws are not mentioned - only screws with "regular" thread. When using these one or two washers are mandaory depending on the material.

My question is, does the IPC standard include self tapping screws?

Is it necessary to use washers in connection with self tapping screws?

The automobile industry uses a variety of self tapping screws and in most instances no washer is used - and this seems to work fine.

Regards

Torben Taustrup

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Torben Taustrup - [log in to unmask]
PTA, Technical Assistant / Radio Mechanic
Vestas Wind Systems A/S
Paludan-Müllers Vej 82, 8200 Århus N
Tlf: +45 97 30 40 31   Telefax: +45 97 30 40 01
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To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
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To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
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