Hi Mike
I would say you are not crazy, but the designer is. 1/2" of bend each
end on a 6 inches? You are talking about 16% bend. Basic mechanical
engineering will tell you how crazy that is.
I would not build such a thing without some airtight liability
waivers.
There is likely no IPC spec on this one, but at some point common sense
has to apply.
regards,
Graham Collins
Process Engineer,
L-3 Communications Electronic Systems Inc.
Halifax
(902) 873-2000 ext 6215
>>> [log in to unmask] 01/12/05 09:51AM >>>
Hello Joyce,
You seem to have a misunderstanding of the situation.
We have a customer who is building an assembly on a rigid substrate
and then flexing it. The board is about the size of a 6-inch ruler.
Each end is deflected about half an inch.
Solder joints at the extremities are failing. Resistors in those
areas are mounted parallel to curvature. These joints see maximum
stress.
Although the contract manufacturer has changed the orientation of
these devices (to be perpendicular to the curvature), we don't
understand
why the assemblies are not built on flex material.
There is no IPC document which I can find that mandates the use of
flex material for this type of application.
Am I crazy? Is this an acceptable practice?
Regards,
Mike
Mike Simms
Chemist
Trace Laboratories - Central
1150 W. Euclid Ave.
Palatine, IL 60067
phone 847-934-5300
fax 847-934-4600
www.tracelabs.com
-----Original Message-----
From: Joyce Koo [mailto:[log in to unmask]]
Sent: Tuesday, January 11, 2005 8:10 AM
Subject: Re: FW: Flexible vs. rigid substrates
Michael,
who is the MFG of your flex? they must have design guide, including
radius
of curvature, slot/hole location at bent, etc.etc. some of them got
shielding requirements, impedance matching, etc.etc. performance
driven and
material related (e.g. number of layers, thickness, etc). if you just
want
to know 180 degree fold flex and design how it be done, many of
cellphone,
LCD got flex folded over, you can measure the thickness, components
mount,
encapsulation, etc.etc. (most of them are well designed), you can form
your
own design guide if you like...
jk (my 2 cents.)
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Simms, Michael
Sent: Monday, January 10, 2005 5:50 PM
To: [log in to unmask]
Subject: [TN] FW: Flexible vs. rigid substrates
Hello T'Netters,
In the absence of any replies to a question that I believe many of
you
should have knowledge about, please allow me to re-post:
> Recently, the issue of the use of rigid printed wiring boards in an
> application
> which demands that printed wiring boards be pressed into an outer
shell
> with some
curvature has surfaced.
> I'm accustomed to the use of flexible substrates for any
applications
> which demand
that the board does not stay flat.
> However, I don't see any IPC document which mandates the use of
rigid
> boards
> for 180-degree assembly applications and flex boards (or rigid-flex)
for
> anything else.
>
Should rigid boards be used in applications which demancd that
the assemblies be flexed to some degree?
> Are there any guidelines for the selection of one type over another?
> Are there any reliability issues with the use of surface mount
devices on
> flex boards which don't also apply to rigid boards?
> Why would a manufacturer opt for a rigid board over a flex board for
> assemblies which
> are subsequently flexed? Is this a choice based on cost?
Thanks,
Regards,
Mike
Mike Simms
Chemist
Trace Laboratories - Central
1150 W. Euclid Ave.
Palatine, IL 60067
phone 847-934-5300
fax 847-934-4600
www.tracelabs.com
Notice: This message is confidential and intended for the private use
of
the addressee only.
>
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
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 1.8e
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 1.8e
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 1.8e
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
-----------------------------------------------------
|
