Looks to me like the polyimide modulus is way too high.
Plasticizer concentration to low? Chemical, heat, radiation damage to the kapton?
Chris
Chris Mahanna
President, Technical Manager
Robisan Laboratory Inc.
6502 E. 21st Street
Indianapolis, Indiana 46219
317-353-6249
-----Original Message-----
From: IPC-600-6012 [mailto:[log in to unmask]] On Behalf Of Koop, Nicholas
Sent: Wednesday, October 28, 2015 12:49 PM
To: x, IPC-600-6012 <[log in to unmask]>
Subject: Re: [IPC-600-6012] Flex quesstion
William,
There have been a few causes:
1. Having plated thru hole pads in the bend radius cause a "spike" in the part thickness, creating a stress riser
2. Having too tight of a bend radius that causes material to be stretched to the rupture point
3. A tool that cut the part
In the case of the image that Vicka has shared, the bend radius is not very severe, and it seemed to happen in just a bend or two. This makes me wonder what is happening in this case. It seems like the film was brittle, which is not something I have experienced before.
The only other case of something similar is when I have seen a thin coat of prepreg resin getting on the coverlay. When bent, the resin would crack or release from the coverlay creating a similar visual. However, Vicka's microsections do not seem to have any resin on top of the coverlay.
I am assuming that Vicka has caught the condition before it propagated into the adhesive and eventually the foil.
Nick
-----Original Message-----
From: IPC-600-6012 [mailto:[log in to unmask]] On Behalf Of Dieffenbacher, William C (US)
Sent: Wednesday, October 28, 2015 11:38 AM
To: [log in to unmask]
Subject: Re: [IPC-600-6012] Flex quesstion
Nick, When you have seen it did you ever determine a root cause?
-----Original Message-----
From: IPC-600-6012 [mailto:[log in to unmask]] On Behalf Of Koop, Nicholas
Sent: Wednesday, October 28, 2015 12:25 PM
To: [log in to unmask]<mailto:[log in to unmask]>
Subject: Re: [IPC-600-6012] Flex quesstion
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EXTERNAL EMAIL -- This message originates from outside our organization.
This is a rare condition. When it happens, usually I see the crack propagate thru the adhesive eventually.
Nick Koop | Sr. Field Application Engineering - Flex Technology | TTM Technologies
(763) 245-4825 - Office | (763) 245-4825 - Cell | [log in to unmask]<mailto:[log in to unmask]> www.ttm.com<http://www.ttm.com>
-----Original Message-----
From: IPC-600-6012 [mailto:[log in to unmask]] On Behalf Of Hammill, Vicka (EHCOE)
Sent: Wednesday, October 28, 2015 10:56 AM
To: [log in to unmask]<mailto:[log in to unmask]>
Subject: [IPC-600-6012] Flex quesstion
Has anyone ever seen this condition of cracking of the Kapton on a flexible part of a rigid flex? If so, do you the cause? We have done crossections on this and it showed the kapton only cracking...the adhesive was not cracked and remained untouched. So far, we have found no specific reason for the cause.
Any input would be appreciated.
Vicka Hammill
Staff Engineer/PB CAA
Honeywell
Lync Phone: 480-627-5547
FAX: 602-436-1005
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