All right. This "prickly" issue is getting under my skin.
More questions:
If fibers are inadvertently exposed or disrupted by a board mod (a knife or rotary tool slips a fraction of a mm too deep while cutting a track...), but at a stage in the process where it will not go through further reflow/wave-type heat stress, and it is not going into a harsh environment; No boat is in danger of sinking here...
Would you repair it - dab some epoxy on and bake?
Or would you leave it?
Classic power struggle - margins are slim, and techs want to just push a board through rather than invest more process time, but quality inspectors and repair specialists want to fix it.
Techs want to know what could *possibly* go wrong from such a small defect. Start describing how they used to do things and *those* products didn't have problems. (not mentioning that in those days, the thinnest trace or PCB layer was 20th, and the smallest component was an 0805)
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Hfjord
Sent: June 19, 2007 1:03 PM
To: [log in to unmask]
Subject: [TN] SV: [TN] fibers
Genny,
When you shrub your back against a board with exposed fibers, you may get disrupted fibers into your skin.
What do the netters say? Will she be angry and disrupt the exposed fiber on the PC and unplug?
Allright, we have to think then. Very odd question. The FR4 fibers are from the beginning a woven mat with bundles of glass fibers. All is surrounded and completely 'molded' in epoxy and cured. The only few occasions when I've seen exposed fibers have been after(incorrect) board repair or modifications of boards (machining with various tools). Also, board edges have sometimes exposed some fibers from bad depaneling. What I know, noone has been anxious about that, because normal humidity won't penetrate far into the structure. However, compare with the gelcote on a sailing boat's hull. If the gelcote is damaged, water can indeed penetrate along the fibers in a long time scale. A friend of mine did not care about his boat for many years, the gelcote was scratched after endless pulling boat from water, across stone and sand to avoid tidewater. It was a small boat for fishing. After some years he left the boat in the water for one season, and...when I helped him to get it on land for repair, it weighted tons. He did not understand. I did. The glassfiber construction had sucked such a lot of water, that the weight was about 200 kg extra!
One can't compare a plastic boat to a PWB, but logically, some water may find its way into a FR4 structure likewise. Water molecules have a infamous capability to diffuse into various materials, as we all know.
My two ounces
Inge
-----Ursprungligt meddelande-----
Från: TechNet [mailto:[log in to unmask]] För Genny Gibbard
Skickat: den 19 juni 2007 17:26
Till: [log in to unmask]
Ämne: [TN] fibers
Trying again - would appreciate your knowledgeable responses or direct me to some info or sources of reading on this:
What are the dangers associated with each of exposed fibers and disrupted fibers in FR4 laminate?
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0 To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL) 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 847-615-7100
ext.2815
-----------------------------------------------------
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0 To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) 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 847-615-7100 ext.2815
-----------------------------------------------------
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
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 847-615-7100 ext.2815
-----------------------------------------------------
|
